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Ali OJ, Ehrle A, Comerford EJ, Canty-Laird EG, Mead A, Clegg PD, Maddox TW. Intrafascicular chondroid-like bodies in the ageing equine superficial digital flexor tendon comprise glycosaminoglycans and type II collagen. J Orthop Res 2021; 39:2755-2766. [PMID: 33580534 DOI: 10.1002/jor.25002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 12/24/2020] [Accepted: 01/29/2021] [Indexed: 02/04/2023]
Abstract
The superficial digital flexor tendon (SDFT) is considered functionally equivalent to the human Achilles tendon. Circular chondroid depositions scattered amongst the fascicles of the equine SDFT are rarely reported. The purpose of this study was the detailed characterization of intrafascicular chondroid-like bodies (ICBs) in the equine SDFT, and the assessment of the effect of ageing on the presence and distribution of these structures. Ultrahigh field magnetic resonance imaging (9.4T) series of SDFT samples of young (1-9 years) and aged (17-25 years) horses were obtained, and three-dimensional reconstruction of ICBs was performed. Morphological evaluation of the ICBs included histology, immunohistochemistry and transmission electron microscopy. The number, size, and position of ICBs was determined and compared between age groups. There was a significant difference (p = .008) in the ICB count between young and old horses with ICBs present in varying number (13-467; median = 47, mean = 132.6), size and distribution in the SDFT of aged horses only. There were significantly more ICBs in the tendon periphery when compared with the tendon core region (p = .010). Histological characterization identified distinctive cells associated with increased glycosaminoglycan and type II collagen extracellular matrix content. Ageing and repetitive strain frequently cause tendon micro-damage before the development of clinical tendinopathy. Documentation of the presence and distribution of ICBs is a first step towards improving our understanding of the impact of these structures on the viscoelastic properties, and ultimately their effect on the risk of age-related tendinopathy in energy-storing tendons.
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Affiliation(s)
- Othman J Ali
- Department of Musculoskeletal Biology and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK.,Department of Surgery and Theriogenology, College of Veterinary Medicine, University of Sulaimani, Sulaymaniyah, Sulaymaniyah, Iraq.,Department of Medical Laboratory Science, Komar University of Science and Technology, Sulaymaniyah, Kurdistan Region, Iraq
| | - Anna Ehrle
- Department of Musculoskeletal Biology and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | - Eithne J Comerford
- Department of Musculoskeletal Biology and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK.,Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Neston, UK.,The Medical Research Council Versus Arthritis Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, Faculty of Health and Life Science, University of Liverpool, Liverpool, UK
| | - Elizabeth G Canty-Laird
- Department of Musculoskeletal Biology and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK.,The Medical Research Council Versus Arthritis Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, Faculty of Health and Life Science, University of Liverpool, Liverpool, UK
| | - Ashleigh Mead
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Neston, UK
| | - Peter D Clegg
- Department of Musculoskeletal Biology and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK.,Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Neston, UK.,The Medical Research Council Versus Arthritis Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, Faculty of Health and Life Science, University of Liverpool, Liverpool, UK
| | - Thomas W Maddox
- Department of Musculoskeletal Biology and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK.,Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Neston, UK
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2
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Crawford KL, Finnane A, Greer RM, Barnes TS, Phillips CJC, Woldeyohannes SM, Bishop EL, Perkins NR, Ahern BJ. Survival Analysis of Training Methodologies and Other Risk Factors for Musculoskeletal Injury in 2-Year-Old Thoroughbred Racehorses in Queensland, Australia. Front Vet Sci 2021; 8:698298. [PMID: 34796223 PMCID: PMC8593238 DOI: 10.3389/fvets.2021.698298] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 09/30/2021] [Indexed: 11/13/2022] Open
Abstract
Musculoskeletal injuries remain a global problem for the Thoroughbred racing industry and there is conflicting evidence regarding the effect of age on the incidence of injuries. The ideal time to commence race training is strongly debated, with limited supporting literature. There is also conflicting evidence regarding the effect of high-speed exercise on musculoskeletal injuries. There is a strong interest in developing training and management strategies to reduce the frequency of injuries. The types of musculoskeletal injuries vary between 2-year-old and older horses, with dorsal metacarpal disease the most common injury in 2-year-old horses. It is likely that risk factors for injury in 2-year-old horses are different than those for older horses. It is also likely that the risk factors may vary between types of injury. This study aimed to determine the risk factors for musculoskeletal injuries and dorsal metacarpal disease. We report the findings of a large scale, prospective observational study of 2-year-old horses in Queensland, Australia. Data were collected weekly for 56-weeks, from 26 trainers, involving 535 2-year-old Thoroughbred racehorses, 1, 258 training preparations and 7, 512-weeks of exercise data. A causal approach was used to develop our statistical models, to build on the existing literature surrounding injury risk, by incorporating the previously established causal links into our analyses. Where previous data were not available, industry experts were consulted. Survival analyses were performed using Cox proportional hazards or Weibull regression models. Analysis of musculoskeletal injuries overall revealed the hazard was reduced with increased exposure to high-speed exercise [Hazard ratio (HR) 0.89, 95% Confidence Interval (CI) 0.84, 0.94, p < 0.001], increased number of training preparations (HR 0.58, 95% CI 0.50, 0.67, p < 0.001), increased rest before the training preparation (HR 0.89, 95% CI 0.83, 0.96, p = 0.003) and increased dam parity (HR 0.86, 95% CI 0.77, 0.97, p = 0.01). The hazard of injury was increased with increasing age that training commenced (HR 1.13, 95% CI 1.06, 1.19, p < 0.001). Analyses were then repeated with the outcome of interest dorsal metacarpal disease. Factors that were protective against dorsal metacarpal disease and musculoskeletal injuries overall included: increased total cumulative distance (HR 0.89, 95% CI 0.82, 0.97, p = 0.001) and total cumulative days exercised as a gallop (HR 0.96, 95% CI 0.92, 0.99, p = 0.03), the number of the training preparations (HR 0.43, 95% CI 0.30, 0.61, p < 0.001). The age that training commenced was harmful for both dorsal metacarpal disease (HR 1.17, 95% CI 1.07, 1.28, p < 0.001 and overall musculoskeletal injuries.). The use of non-ridden training modalities was protective for dorsal metacarpal disease (HR 0.89, 95% CI 0.81, 0.97, p = 0.008), but not musculoskeletal injuries overall. The male sex increased the hazard of DMD compared to females (HR 2.58, 95% CI 1.20, 5.56, p = 0.02), but not MSI overall. In summary, the hazard of musculoskeletal injury is greatest for 2-year-old horses that are born from uniparous mares, commence training at a later age, are in their first training preparation, have undertaken little high-speed exercise or had limited rest before their training preparation. The hazard of dorsal metacarpal disease is greatest for 2-year-old horses that are males, commence training at a later age, are in their first training preparation, have undertaken little high-speed exercise or had limited use of non-ridden training modalities. Close monitoring of these high-risk horses during their training program could substantially reduce the impact of MSI. Furthermore, an understanding of how training methodologies affect the hazard of MSI facilitates modification of training programs to mitigate the risk impact of injury. The strengths of this study include a large sample size, a well-defined study protocol and direct trainer interviews. The main limitation is the inherent susceptibility to survival bias.
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Affiliation(s)
- Kylie L Crawford
- School of Veterinary Science, The University of Queensland, Gatton, QLD, Australia.,School of Public Health, The University of Queensland, Herston, QLD, Australia
| | - Anna Finnane
- School of Public Health, The University of Queensland, Herston, QLD, Australia
| | - Ristan M Greer
- Torus Research, Bridgeman Downs, QLD, Australia.,Mater Research Institute, The University of Queensland, Brisbane, QLD, Australia
| | - Tamsin S Barnes
- School of Veterinary Science, The University of Queensland, Gatton, QLD, Australia.,Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Gatton, QLD, Australia
| | - Clive J C Phillips
- Curtin University Sustainability Policy (CUSP) Institute, Curtin University, Perth, WA, Australia
| | | | - Emma L Bishop
- Garrards Equine Veterinary Practice, Albion, QLD, Australia
| | - Nigel R Perkins
- School of Veterinary Science, The University of Queensland, Gatton, QLD, Australia
| | - Benjamin J Ahern
- School of Veterinary Science, The University of Queensland, Gatton, QLD, Australia
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Mlyniec A, Dabrowska S, Heljak M, Weglarz WP, Wojcik K, Ekiert-Radecka M, Obuchowicz R, Swieszkowski W. The dispersion of viscoelastic properties of fascicle bundles within the tendon results from the presence of interfascicular matrix and flow of body fluids. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2021; 130:112435. [PMID: 34702520 DOI: 10.1016/j.msec.2021.112435] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Revised: 09/06/2021] [Accepted: 09/09/2021] [Indexed: 01/12/2023]
Abstract
In this work, we investigate differences in the mechanical and structural properties of tendon fascicle bundles dissected from different areas of bovine tendons. The properties of tendon fascicle bundles were investigated by means of uniaxial tests with relaxation periods and hysteresis, dynamic mechanical analysis (DMA), as well as magnetic resonance imaging (MRI). Uniaxial tests with relaxation periods revealed greater elastic modulus, hysteresis, as well as stress drop during the relaxation of samples dissected from the posterior side of the tendon. However, the normalized stress relaxation curves did not show a statistically significant difference in the stress drop between specimens cut from different zones or between different strain levels. Using dynamic mechanical analysis, we found that fascicle bundles dissected from the anterior side of the tendon had lower storage and loss moduli, which could result from altered fluid flow within the interfascicular matrix (IFM). The lower water content, diffusivity, and higher fractional anisotropy of the posterior part of the tendon, as observed using MRI, indicates a different structure of the IFM, which controls the flow of fluids within the tendon. Our results show that the viscoelastic response to dynamic loading is correlated with fluid flow within the IFM, which was confirmed during analysis of the MRI results. In contrast to this, the long-term relaxation of tendon fascicle bundles is controlled by viscoplasticity of the IFM and depends on the spatial distribution of the matrix within the tendon. Comparison of results from tensile tests, DMA, and MRI gives new insight into tendon mechanics and the role of the IFM. These findings may be useful in improving the diagnosis of tendon injury and effectiveness of medical treatments for tendinopathies.
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Affiliation(s)
- Andrzej Mlyniec
- AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, Krakow, Poland.
| | - Sylwia Dabrowska
- AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, Krakow, Poland
| | - Marcin Heljak
- Warsaw University of Technology, Faculty of Materials Science and Engineering, Warsaw, Poland
| | | | - Kaja Wojcik
- AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, Krakow, Poland
| | - Martyna Ekiert-Radecka
- AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, Krakow, Poland
| | - Rafal Obuchowicz
- Jagiellonian University Collegium Medicum, Department of Radiology, Krakow, Poland
| | - Wojciech Swieszkowski
- Warsaw University of Technology, Faculty of Materials Science and Engineering, Warsaw, Poland
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Wagner FC, Gerlach K, Geiger SM, Gittel C, Böttcher P, Mülling CKW. Biplanar High-Speed Fluoroscopy of Pony Superficial Digital Flexor Tendon (SDFT)-An In Vivo Pilot Study. Vet Sci 2021; 8:vetsci8060092. [PMID: 34072030 PMCID: PMC8228745 DOI: 10.3390/vetsci8060092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 05/22/2021] [Accepted: 05/24/2021] [Indexed: 11/16/2022] Open
Abstract
The superficial digital flexor tendon (SDFT) is the most frequently injured structure of the musculoskeletal system in sport horses and a common cause for early retirement. This project's aim was to visualize and measure the strain of the sound, injured, and healing SDFTs in a pony during walk and trot. For this purpose, biplanar high-speed fluoroscopic kinematography (FluoKin), as a high precision X-ray movement analysis tool, was used for the first time in vivo with equine tendons. The strain in the metacarpal region of the sound SDFT was 2.86% during walk and 6.78% during trot. When injured, the strain increased to 3.38% during walk and decreased to 5.96% during trot. The baseline strain in the mid-metacarpal region was 3.13% during walk and 6.06% during trot and, when injured, decreased to 2.98% and increased to 7.61%, respectively. Following tendon injury, the mid-metacarpal region contributed less to the overall strain during walk but showed increased contribution during trot. Using this marker-based FluoKin technique, direct, high-precision, and long-term strain measurements in the same individual are possible. We conclude that FluoKin is a powerful tool for gaining deeper insight into equine tendon biomechanics.
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Affiliation(s)
- Franziska C. Wagner
- Institute of Veterinary Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, Leipzig University, An den Tierkliniken 43, 04103 Leipzig, Germany; (S.M.G.); (C.K.W.M.)
- Correspondence: ; Tel.: +49-341-97-38054
| | - Kerstin Gerlach
- Department for Horses, Faculty of Veterinary Medicine, Leipzig University, An den Tierkliniken 43, 04103 Leipzig, Germany; (K.G.); (C.G.)
| | - Sandra M. Geiger
- Institute of Veterinary Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, Leipzig University, An den Tierkliniken 43, 04103 Leipzig, Germany; (S.M.G.); (C.K.W.M.)
| | - Claudia Gittel
- Department for Horses, Faculty of Veterinary Medicine, Leipzig University, An den Tierkliniken 43, 04103 Leipzig, Germany; (K.G.); (C.G.)
| | - Peter Böttcher
- Small Animal Clinic, Department of Veterinary Medicine, Freie Universität Berlin, Oertzenweg 19b, 14163 Berlin, Germany;
| | - Christoph K. W. Mülling
- Institute of Veterinary Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, Leipzig University, An den Tierkliniken 43, 04103 Leipzig, Germany; (S.M.G.); (C.K.W.M.)
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Crawford KL, Finnane A, Phillips CJC, Greer RM, Woldeyohannes SM, Perkins NR, Kidd LJ, Ahern BJ. The Risk Factors for Musculoskeletal Injuries in Thoroughbred Racehorses in Queensland, Australia: How These Vary for Two-Year-Old and Older Horses and with Type of Injury. Animals (Basel) 2021; 11:ani11020270. [PMID: 33494508 PMCID: PMC7910838 DOI: 10.3390/ani11020270] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 01/08/2021] [Accepted: 01/18/2021] [Indexed: 11/25/2022] Open
Abstract
Simple Summary Musculoskeletal injuries (MSI) continue to affect Thoroughbred racehorses internationally, despite over thirty years of research into this problem. Studies of risk factors for musculoskeletal injuries report inconsistent findings. Consequently, developing training strategies to mitigate the risk of MSI is difficult. We identified factors associated with particularly high odds of injury in this population of racehorses. Two-year-old horses from primiparous mares (first foals born) are at increased odds of MSI, particularly dorsal metacarpal disease (“shinsoreness”). Two-year-old horses that have had a total preparation length of between 10 and 14 weeks also have increased odds of injury. Horses of all ages that travelled a total distance of 2.4–3.8 km (12–19 furlongs) at a gallop (faster than 15 m/s; 13 s/furlong; 900 m/min; 55 km/h) in the last four weeks and horses three years and older that travelled 3.0–4.8 km (15–24 furlongs) at three-quarter pace and above (faster than 13 m/s; 15 s/furlong; 800 m/min; 48 km/h) also have increased odds of injury. We recommend that these horses should be monitored closely for impending signs of injury. We also observed a non-linear relationship between high-speed exercise and musculoskeletal injuries. This highlights the importance of high-speed exercise to enable tissue adaptation to training. Finally, in some situations, increasing the number of days worked at a slow pace may be more effective for preventing MSI, if horses are perceived at a higher risk, than resting the horse altogether. Early identification of horses at increased risk of injury and appropriate intervention could substantially reduce the impact of musculoskeletal injuries in Thoroughbred racehorses. Abstract Musculoskeletal injuries (MSI) continue to affect Thoroughbred racehorses internationally. There is a strong interest in developing training and management strategies to reduce their impact, however, studies of risk factors report inconsistent findings. Furthermore, many injuries and fatalities occur during training rather than during racing, yet most studies report racing data only. By combining racing and training data a larger exposure to risk factors and a larger number of musculoskeletal injuries are captured and the true effect of risk factors may be more accurately represented. Furthermore, modifications to reduce the impact of MSI are more readily implemented at the training level. Our study aimed to: (1) determine the risk factors for musculoskeletal injuries and whether these are different for two-year-old and older horses and (2) determine whether risk factors vary with type of injury. This was performed by repeating analyses by age category and injury type. Data from 202 cases and 202 matched controls were collected through weekly interviews with trainers and analysed using conditional logistic regression. Increasing dam parity significantly reduced the odds of injury in horses of all age groups because of the effect in two-year-old horses (odds ratio (OR) 0.08; 95% confidence interval (CI) 0.02, 0.36; p < 0.001). Increasing total preparation length is associated with higher odds of injury in horses of all ages (OR 5.56; 95% CI 1.59, 19.46; p = 0.01), but particularly in two-year-old horses (OR 8.05; 95% CI 1.92, 33.76; p = 0.004). Increasing number of days exercised at a slow pace decreased the odds of injury in horses of all ages (OR 0.09; 95% CI 0.03, 0.28; p < 0.001). The distance travelled at three-quarter pace and above (faster than 13 m/s; 15 s/furlong; 800 m/min; 48 km/h) and the total distance travelled at a gallop (faster than 15 m/s; 13 s/furlong; 900 m/min; 55 km/h) in the past four weeks significantly affected the odds of injury. There was a non-linear association between high-speed exercise and injury whereby the odds of injury initially increased and subsequently decreased as accumulated high-speed exercise distance increased. None of the racing career and performance indices affected the odds of injury. We identified horses in this population that have particularly high odds of injury. Two-year-old horses from primiparous mares are at increased odds of injury, particularly dorsal metacarpal disease. Two-year-old horses that have had a total preparation length of between 10 and 14 weeks also have increased odds of injury. Horses of all ages that travelled a total distance of 2.4–3.8 km (12–19 furlongs) at a gallop in the last four weeks and horses three years and older that travelled 3.0–4.8 km (15–24 furlongs) at three-quarter pace and above also have increased odds of injury. We recommend that these horses should be monitored closely for impending signs of injury. Increasing the number of days worked at a slow pace may be more effective for preventing injury, if horses are perceived at a higher risk, than resting the horse altogether. Early identification of horses at increased risk and appropriate intervention could substantially reduce the impact of musculoskeletal injuries in Thoroughbred racehorses.
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Affiliation(s)
- Kylie L. Crawford
- School of Veterinary Science, The University of Queensland, Gatton 4343, Australia; (S.M.W.); (N.R.P.); (L.J.K.); (B.J.A.)
- School of Public Health, The University of Queensland, Herston 4006, Australia;
- Correspondence:
| | - Anna Finnane
- School of Public Health, The University of Queensland, Herston 4006, Australia;
| | - Clive J. C. Phillips
- Curtin University Sustainability Policy (CUSP) Institute, Curtin University, Perth 6845, Australia;
| | - Ristan M. Greer
- Torus Research, Bridgeman Downs 4035, Australia;
- School of Medicine, The University of Queensland, Herston 4006, Australia
| | - Solomon M. Woldeyohannes
- School of Veterinary Science, The University of Queensland, Gatton 4343, Australia; (S.M.W.); (N.R.P.); (L.J.K.); (B.J.A.)
| | - Nigel R. Perkins
- School of Veterinary Science, The University of Queensland, Gatton 4343, Australia; (S.M.W.); (N.R.P.); (L.J.K.); (B.J.A.)
| | - Lisa J. Kidd
- School of Veterinary Science, The University of Queensland, Gatton 4343, Australia; (S.M.W.); (N.R.P.); (L.J.K.); (B.J.A.)
| | - Benjamin J. Ahern
- School of Veterinary Science, The University of Queensland, Gatton 4343, Australia; (S.M.W.); (N.R.P.); (L.J.K.); (B.J.A.)
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Crawford KL, Finnane A, Greer RM, Phillips CJC, Woldeyohannes SM, Perkins NR, Ahern BJ. Appraising the Welfare of Thoroughbred Racehorses in Training in Queensland, Australia: The Incidence and Type of Musculoskeletal Injuries Vary between Two-Year-Old and Older Thoroughbred Racehorses. Animals (Basel) 2020; 10:ani10112046. [PMID: 33167429 PMCID: PMC7694396 DOI: 10.3390/ani10112046] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/29/2020] [Accepted: 11/02/2020] [Indexed: 11/16/2022] Open
Abstract
Simple Summary Musculoskeletal injuries (MSI) remain a concerning cause of racehorse morbidity and mortality with serious ethical and welfare consequences. Previous research examining risk factors for injuries report inconsistent findings. Age is thought to affect the risk of injury, but, to date, there have been no prospective studies specifically comparing injuries between two-year-old versus older horses. We aimed to: (1) determine the incidence of injuries for two-year-old and older horses, and whether this was affected by training track, season, or rainfall, and (2) determine the types of injuries affecting two-year-old and older horses, and whether horses trialled or raced after injury. Data were collected through personal structured weekly interviews with participating trainers over a 13-month period. Data were analysed using Poisson regression. The incidence of MSI in the current study was low (0.6%). The incidence of MSI in two-year-old horses was higher than older horses. Types of MSI varied between two-year-old and older horses and affected whether horses subsequently trialled or raced from 11 to 23 months after injury. A larger proportion of two-year-old horses had dorsal metacarpal disease and traumatic lacerations. A smaller proportion of two-year-old horses had suspensory desmitis, superficial digital flexor tendonitis, proximal sesamoid bone fractures, and fetlock joint injuries than older horses. Training track and rainfall did not affect the incidence of injuries. The season affected the incidence of injuries in two-year-old horses but not in older horses. Abstract Musculoskeletal injuries (MSI) remain a concerning cause of racehorse morbidity and mortality with important ethical and welfare consequences. Previous research examining risk factors for MSI report inconsistent findings. Age is thought to affect MSI risk, but, to date, there have been no prospective studies comparing MSI in two-year-old versus older horses. This study aimed to: (1) determine the incidence of MSI for two-year-old and older horses, and whether this was affected by training track, season, or rainfall, and (2) determine the types of MSI affecting two-year-old and older horses, and whether horses trialled or raced after injury. A prospective survey was conducted with data collected through personal structured weekly interviews with participating trainers over a 13-month period. Data were analysed using Poisson regression. The incidence of MSI in the current study was low (0.6%). The incidence of MSI in two-year-old horses was higher than older horses (p < 0.001). Types of MSI varied between two-year-old and older horses (p < 0.001) and affected whether horses subsequently trailed or raced from 11 to 23 months after injury (p < 0.001). A larger proportion of two-year-old horses had dorsal metacarpal disease and traumatic lacerations. A smaller proportion of two-year-old horses had suspensory ligament desmitis, superficial digital flexor tendonitis, proximal sesamoid bone fractures, and fetlock joint injuries than older horses. Training track and rainfall did not affect MSI. The season affected MSI in two-year-old horses (p < 0.001) but not older horses. The major limitation was that trainers in this study were metropolitan (city) and our findings may not be generalisable to racehorses in regional (country) areas. Another significant limitation was the assumption that MSI was the reason for failure to trial or race after injury. In conclusion, the incidence of MSI was low in the current study and the types and the risk factors for MSI are different for two-year-old and older horses.
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Affiliation(s)
- Kylie L. Crawford
- School of Veterinary Science, The University of Queensland, 4343 Gatton, Australia; (S.M.W.); (N.R.P.); (B.J.A.)
- School of Public Health, The University of Queensland, 4006 Herston, Australia;
- Correspondence:
| | - Anna Finnane
- School of Public Health, The University of Queensland, 4006 Herston, Australia;
| | - Ristan M. Greer
- Torus Research, 4035 Bridgeman Downs, Australia;
- School of Medicine, The University of Queensland, 4006 Herston, Australia
| | - Clive J. C. Phillips
- Curtin University Sustainability Policy (CUSP) Institute, Curtin University, 6845 Perth, Australia;
| | - Solomon M. Woldeyohannes
- School of Veterinary Science, The University of Queensland, 4343 Gatton, Australia; (S.M.W.); (N.R.P.); (B.J.A.)
| | - Nigel R. Perkins
- School of Veterinary Science, The University of Queensland, 4343 Gatton, Australia; (S.M.W.); (N.R.P.); (B.J.A.)
| | - Benjamin J. Ahern
- School of Veterinary Science, The University of Queensland, 4343 Gatton, Australia; (S.M.W.); (N.R.P.); (B.J.A.)
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7
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Evaluation of Return Rates to Races in Racehorses After Tendon Injuries: Lesion-Related Parameters. J Equine Vet Sci 2020; 87:102931. [PMID: 32172919 DOI: 10.1016/j.jevs.2020.102931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 01/02/2020] [Accepted: 01/13/2020] [Indexed: 11/20/2022]
Abstract
Metacarpal tendon diseases are important problems that may cause a decrease in performance and even may finish sport life in equine athletes. In this study, it was aimed to evaluate the ratio of return to races and the time of staying away from races and also to detect the prognostic value of ultrasonographic findings in Thoroughbred and Arabian racehorses with metacarpal flexor tendon injury or peritendonitis. Of 120 cases, 84 (70.0%) returned to races. Among these, 82.1% had tendonitis (69/84) and 17.9% peritendonitis (15/84). Among the cases being unable to return to races, 91.7% had tendonitis (33/36), and 8.3% had peritendonitis (3/36). Although not statistically significant (P > .05), tendonitis cases were found to be away from races for longer periods. Tendonitis cases (85.0%, 102/120) stayed away from races for an average of 39.9 months, whereas peritendonitis cases (15.0%, 18/120) stayed away from races for an average of 27.1 months. It was found that the ratio of return to races after injury was higher in cases without tendon thickening (86.7%, 26/30) than in cases with tendon thickening (64.4%, 58/90). The results of this study show that tendon injuries causing tendon thickening have a negative effect on the ratio of return to races (P < .05).
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8
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Rogers CW, Bolwell CF, Gee EK, Rosanowski SM. Equine musculoskeletal development and performance: impact of the production system and early training. ANIMAL PRODUCTION SCIENCE 2020. [DOI: 10.1071/an17685] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The welfare debate around horse racing appears to be focussed on musculoskeletal injury and the racing of 2-year-olds. Much of this debate appears contrary to the evolutionary history of the horse as a cursorial animal and the capability of the equine musculoskeletal system to respond to the demands of race training. Epidemiological studies have reported that 2-year-old racehorses have a longer time period from entering training to the first race and a greater number of lost training days than older horses. However, this is, in part, due to the time taken to learn to train and the impact of dorsal metacarpal disease, which is due to loading of naïve as opposed to immature tissue. Across several racing jurisdictions and codes, it has been demonstrated that horses that train and race as 2-year-olds have longer, more successful, careers than those that start racing later in life. This positive trend has also been observed with horses starting in equestrian sport at an early age. The literature on the growth and development of the horse indicates that the musculoskeletal system is primed for activity and loading from an early age. Additional exercise for the young horse has a positive rather the negative effect, with many tissues having a sensitive period for ‘priming’ when the horse is a juvenile. This implies that under many modern management systems, the challenge to horse welfare is not ‘too much exercise too soon’ but ‘too little too late’. The current limitation in our understanding is the lack of knowledge of what is the correct exercise dose to optimise the musculoskeletal system. Modern management systems invariably provide too little exercise, but is the exercise data from feral horses the ‘gold standard’, or more a reflection of what the horse is capable of if resources such as food and water are limited? Further research is required to refine our understanding of the optimal exercise levels required and development of greater precision in identifying the sensitive periods for priming the musculoskeletal system.
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Plevin S, McLellan J, Schie H, Parkin T. Ultrasound tissue characterisation of the superficial digital flexor tendons in juvenile Thoroughbred racehorses during early race training. Equine Vet J 2018; 51:349-355. [DOI: 10.1111/evj.13006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 07/29/2018] [Indexed: 12/28/2022]
Affiliation(s)
- S. Plevin
- Florida Equine Veterinary Associates Ocala Florida USA
| | - J. McLellan
- Florida Equine Veterinary Associates Ocala Florida USA
| | - H. Schie
- Department of Equine Sciences Utrecht University Utrecht the Netherlands
| | - T. Parkin
- University of Glasgow, School of Veterinary Medicine Glasgow UK
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10
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Alzola R, Easter C, Riggs CM, Gardner DS, Freeman SL. Ultrasonographic-based predictive factors influencing successful return to racing after superficial digital flexor tendon injuries in flat racehorses: A retrospective cohort study in 469 Thoroughbred racehorses in Hong Kong. Equine Vet J 2018; 50:602-608. [PMID: 29352495 PMCID: PMC6099230 DOI: 10.1111/evj.12810] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 01/10/2018] [Indexed: 11/28/2022]
Abstract
BACKGROUND Superficial digital flexor tendon (SDFT) injury is an important health and welfare concern in racehorses. It is generally diagnosed with ultrasonography, but predictive ultrasonographic features have not been reported. OBJECTIVES To determine ultrasonographic features of forelimb SDFT injury at initial presentation in Thoroughbred racehorses that could predict a successful return to racing (completing ≥5 races). STUDY DESIGN Retrospective cohort study. METHODS Digitised ultrasonographic images of 469 horses with forelimb SDFT injuries from the Hong Kong Jockey Club (2003-2014) were evaluated, using a previously validated ultrasonographic scoring system. Six ultrasonographic parameters were evaluated (type and extent of the injury, location, echogenicity, cross-sectional area and longitudinal fibre pattern of the maximal injury zone [MIZ]), as well as horse signalment, retirement date and number of races before and after injury. Data were analysed by generalised linear regression with significance at P<0.05. RESULTS Cases were divided into two groups: 1) For cases of SDFT tendonitis with core lesions, cross-sectional area at the MIZ was the most significant factor determining a successful return to racing (P = 0.03). If the lesion was <50% of the total cross-sectional area, horses had 29-35% probability of successfully racing again, but if it was ≥50% this decreased to 11-16%. 2) For cases of SDFT tendonitis without a core lesion, longitudinal fibre pattern at the MIZ best predicted a successful return to racing (P = 0.002); if the affected longitudinal fibre pattern was <75% of the total, horses had 49-99% probability of successfully return to racing, but if it was ≥75% this decreased to 14%. MAIN LIMITATIONS Prognostic information may not be applicable to other breeds/disciplines. CONCLUSIONS This is the first study to describe ultrasonographic features of forelimb SDFT injuries at initial presentation that were predictive of successful return to racing. The outcomes will assist with early, evidence-based decisions on prognosis in Thoroughbred racehorses.
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Affiliation(s)
- R. Alzola
- Oakham Veterinary HospitalOakhamRutlandUK
| | | | - C. M. Riggs
- Veterinary Clinical ServicesHong Kong Jockey ClubHong Kong
| | - D. S. Gardner
- School of Veterinary Medicine and ScienceUniversity of NottinghamLoughboroughLeicestershireUK
| | - S. L. Freeman
- School of Veterinary Medicine and ScienceUniversity of NottinghamLoughboroughLeicestershireUK
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11
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Pardey D, Tabor G, Oxley JA, Wills AP. Peak forelimb ground reaction forces experienced by dogs jumping from a simulated car boot. Vet Rec 2018; 182:716. [PMID: 29622683 DOI: 10.1136/vr.104788] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Revised: 03/07/2018] [Accepted: 03/22/2018] [Indexed: 11/04/2022]
Abstract
Many dog owners allow their pets to jump out of a car boot; however, to date, there has been no study that has investigated whether this places dogs at risk of injury. The aim of this study was to investigate the relationship between height and peak vertical ground reaction force (vGRF) in static start jumps. Fifteen healthy adult dogs performed three jumps from a platform that represented common vehicle boot sill heights (0.55, 0.65, 0.75 m), landing on a single force platform. Kinetic data (mediolateral (Fx), craniocaudal (Fy) and vertical (Fz)) were normalised for body weight and analysed via a one-way repeated analysis of variance (ANOVA) and pairwise post hoc tests with a Bonferroni correction applied. There was a significant difference in peak forelimb vGRF between both the 0.55 m (27.35±4.14 N/kg) and the 0.65 m (30.84±3.66 N/kg) platform (P=0.001) and between the 0.65 and 0.75 m (34.12±3.63 N/kg) platform (P=0.001). There was no significant difference in mediolateral or craniocaudal forces between the heights examined. These results suggest that allowing dogs to jump from bigger cars with a higher boot sill may result in augmented levels of loading on anatomical structures. Further research is required to investigate the kinematic effects of height on static jump-down and how peak forelimb vGRF relates to anatomical loading and subsequent injury risk.
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Affiliation(s)
- David Pardey
- Animal Welfare Research and Knowledge Exchange Arena, Department of Animal and Agriculture, Hartpury University Centre, Gloucester, UK
| | - Gillian Tabor
- Animal Welfare Research and Knowledge Exchange Arena, Department of Animal and Agriculture, Hartpury University Centre, Gloucester, UK
| | | | - Alison P Wills
- Animal Welfare Research and Knowledge Exchange Arena, Department of Animal and Agriculture, Hartpury University Centre, Gloucester, UK
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12
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Spiesz EM, Thorpe CT, Thurner PJ, Screen HRC. Structure and collagen crimp patterns of functionally distinct equine tendons, revealed by quantitative polarised light microscopy (qPLM). Acta Biomater 2018; 70:281-292. [PMID: 29409868 PMCID: PMC5894809 DOI: 10.1016/j.actbio.2018.01.034] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 01/19/2018] [Accepted: 01/24/2018] [Indexed: 01/15/2023]
Abstract
Structure-function relationships in tendons are directly influenced by the arrangement of collagen fibres. However, the details of such arrangements in functionally distinct tendons remain obscure. This study demonstrates the use of quantitative polarised light microscopy (qPLM) to identify structural differences in two major tendon compartments at the mesoscale: fascicles and interfascicular matrix (IFM). It contrasts functionally distinct positional and energy storing tendons, and considers changes with age. Of particular note, the technique facilitates the analysis of crimp parameters, in which cutting direction artefact can be accounted for and eliminated, enabling the first detailed analysis of crimp parameters across functionally distinct tendons. IFM shows lower birefringence (0.0013 ± 0.0001 [−]), as compared to fascicles (0.0044 ± 0.0005 [−]), indicating that the volume fraction of fibres must be substantially lower in the IFM. Interestingly, no evidence of distinct fibre directional dispersions between equine energy storing superficial digital flexor tendons (SDFTs) and positional common digital extensor tendons (CDETs) were noted, suggesting either more subtle structural differences between tendon types or changes focused in the non-collagenous components. By contrast, collagen crimp characteristics are strongly tendon type specific, indicating crimp specialisation is crucial in the respective mechanical function. SDFTs showed much finer crimp (21.1 ± 5.5 µm) than positional CDETs (135.4 ± 20.1 µm). Further, tendon crimp was finer in injured tendon, as compared to its healthy equivalents. Crimp angle differed strongly between tendon types as well, with average of 6.5 ± 1.4° in SDFTs and 13.1 ± 2.0° in CDETs, highlighting a substantially tighter crimp in the SDFT, likely contributing to its effective recoil capacity. Statement of Significance This is the first study to quantify birefringence in fascicles and interfascicular matrix of functionally distinct energy storing and positional tendons. It adopts a novel method – quantitative polarised light microscopy (qPLM) to measure collagen crimp angle, avoiding artefacts related to the direction of histological sectioning, and provides the first direct comparison of crimp characteristics of functionally distinct tendons of various ages. A comparison of matched picrosirius red stained and unstained tendons sections identified non-homogenous staining effects, and leads us to recommend that only unstained sections are analysed in the quantitative manner. qPLM is successfully used to assess birefringence in soft tissue sections, offering a promising tool for investigating the structural arrangements of fibres in (soft) tissues and other composite materials.
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Affiliation(s)
- Ewa M Spiesz
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Rd, London E1 4NS, United Kingdom; Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.
| | - Chavaunne T Thorpe
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Rd, London E1 4NS, United Kingdom; Comparative Biomedical Sciences, Royal Veterinary College, Royal College Street, London NW1 0TU, United Kingdom.
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt 9, A-1060 Vienna, Austria.
| | - Hazel R C Screen
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Rd, London E1 4NS, United Kingdom.
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13
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Lavagnino M, Brooks AE, Oslapas AN, Gardner KL, Arnoczky SP. Crimp length decreases in lax tendons due to cytoskeletal tension, but is restored with tensional homeostasis. J Orthop Res 2017; 35:573-579. [PMID: 27878991 DOI: 10.1002/jor.23489] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 11/10/2016] [Indexed: 02/04/2023]
Abstract
Collagen crimp morphology is thought to contribute to the material behavior of tendons and may reflect the local mechanobiological environment of tendon cells. Following loss of collagen tension in tendons, tenocytes initiate a contraction response that shortens tendon length which, in turn, may alter crimp patterns. We hypothesized that changes in the crimp pattern of tendons are the result of cell-based contractions which are governed by relative tautness/laxity of the collagen matrix. To determine the relationship between crimp pattern and tensional homeostasis, rat tail tendon fascicles (RTTfs) were either allowed to freely contract or placed in clamps with 10% laxity for 7 days. The freely contracting RTTfs showed a significant decrease in percent crimp length on both day 5 (3.66%) and day 7 (7.70%). This decrease in crimp length significantly correlated with the decrease in freely contracting RTTf length. Clamped RTTfs demonstrated a significant decrease in percent crimp length on day 5 (1.7%), but no significant difference in percent crimp length on day 7 (0.57%). The results demonstrate that the tendon crimp pattern appears to be under cellular control and is a reflection of the local mechanobiological environment of the extracellular matrix. The ability of tenocytes to actively alter the crimp pattern of collagen fibers also suggests that tenocytes can influence the viscoelastic properties of tendon. Understanding the interactions between tenocytes and their extracellular matrix may lead to further insight into the role tendon cells play in maintaining tendon heath and homeostasis. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:573-579, 2017.
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Affiliation(s)
- Michael Lavagnino
- Laboratory for Comparative Orthopaedic Research, College of Veterinary Medicine, Michigan State University, 784 Wilson Road, East Lansing, Michigan, 48824
| | - Andrew E Brooks
- Laboratory for Comparative Orthopaedic Research, College of Veterinary Medicine, Michigan State University, 784 Wilson Road, East Lansing, Michigan, 48824
| | - Anna N Oslapas
- Laboratory for Comparative Orthopaedic Research, College of Veterinary Medicine, Michigan State University, 784 Wilson Road, East Lansing, Michigan, 48824
| | - Keri L Gardner
- Laboratory for Comparative Orthopaedic Research, College of Veterinary Medicine, Michigan State University, 784 Wilson Road, East Lansing, Michigan, 48824
| | - Steven P Arnoczky
- Laboratory for Comparative Orthopaedic Research, College of Veterinary Medicine, Michigan State University, 784 Wilson Road, East Lansing, Michigan, 48824
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14
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Szczesny SE, Driscoll TP, Tseng HY, Liu PC, Heo SJ, Mauck RL, Chao PHG. Crimped Nanofibrous Biomaterials Mimic Microstructure and Mechanics of Native Tissue and Alter Strain Transfer to Cells. ACS Biomater Sci Eng 2016; 3:2869-2876. [PMID: 29147681 DOI: 10.1021/acsbiomaterials.6b00646] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
To fully recapitulate tissue microstructure and mechanics, fiber crimping must exist within biomaterials used for tendon/ligament engineering. Existing crimped nanofibrous scaffolds produced via electrospinning are dense materials that prevent cellular infiltration into the scaffold interior. In this study, we used a sacrificial fiber population to increase the scaffold porosity and evaluated the effect on fiber crimping. We found that increasing scaffold porosity increased fiber crimping and ensured that the fibers properly uncrimped as the scaffolds were stretched by minimizing fiber-fiber interactions. Constitutive modeling demonstrated that the fiber uncrimping produced a nonlinear mechanical behavior similar to that of native tendon and ligament. Interestingly, fiber crimping altered strain transmission to the nuclei of cells seeded on the scaffolds, which may account for previously observed changes in gene expression. These crimped biomaterials are useful for developing functional fiber-reinforced tissues and for studying the effects of altered fiber crimping due to damage or degeneration.
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Affiliation(s)
- Spencer E Szczesny
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, Philadelphia, Pennsylvania 19104, United States
| | - Tristan P Driscoll
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, Philadelphia, Pennsylvania 19104, United States.,Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Hsiao-Yun Tseng
- Institute of Biomedical Engineering, School of Medicine and School of Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Pang-Ching Liu
- Institute of Biomedical Engineering, School of Medicine and School of Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Su-Jin Heo
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, Philadelphia, Pennsylvania 19104, United States.,Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Robert L Mauck
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, Philadelphia, Pennsylvania 19104, United States.,Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Pen-Hsiu G Chao
- Institute of Biomedical Engineering, School of Medicine and School of Engineering, National Taiwan University, Taipei 10617, Taiwan
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15
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Abstract
The current understanding of pathology as it relates to common diseases of the equine musculoskeletal system is reviewed. Conditions are organized under the fundamental categories of developmental, exercise-induced, infectious, and miscellaneous pathology. The overview of developmental pathology incorporates the new classification system of juvenile osteochondral conditions. Discussion of exercise-induced pathology emphasizes increased understanding of the contribution of cumulative microdamage caused by repetitive cyclic loading. Miscellaneous musculoskeletal pathology focuses on laminitis, which current knowledge indicates should be regarded as a clinical syndrome with a variety of possible distinct mechanisms of structural failure that are outlined in this overview.
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Affiliation(s)
- Frances J Peat
- Equine Orthopaedic Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, 300 West Drake Rd, Fort Collins, CO 80523, USA
| | - Christopher E Kawcak
- Equine Orthopaedic Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, 300 West Drake Rd, Fort Collins, CO 80523, USA.
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16
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Seto SP, Parks AN, Qiu Y, Soslowsky LJ, Karas S, Platt MO, Temenoff JS. Cathepsins in Rotator Cuff Tendinopathy: Identification in Human Chronic Tears and Temporal Induction in a Rat Model. Ann Biomed Eng 2015; 43:2036-46. [PMID: 25558848 DOI: 10.1007/s10439-014-1245-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Accepted: 12/29/2014] [Indexed: 01/08/2023]
Abstract
While overuse of the supraspinatus tendon is a leading factor in rotator cuff injury, the underlying biochemical changes have not been fully elucidated. In this study, torn human rotator cuff (supraspinatus) tendon tissue was analyzed for the presence of active cathepsin proteases with multiplex cysteine cathepsin zymography. In addition, an overuse injury to supraspinatus tendons was induced through downhill running in an established rat model. Histological analysis demonstrated that structural damage occurred by 8 weeks of overuse compared to control rats in the region of tendon insertion into bone. In both 4- and 8-week overuse groups, via zymography, there was approximately a 180% increase in cathepsin L activity at the insertion region compared to the controls, while no difference was found in the midsubstance area. Additionally, an over 400% increase in cathepsin K activity was observed for the insertion region of the 4-week overused tendons. More cathepsin K and L immunostaining was observed at the insertion region of the overuse groups compared to controls. These results provide important information on a yet unexplored mechanism for tendon degeneration that may operate alone or in conjunction with other proteases to contribute to chronic tendinopathy.
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Affiliation(s)
- Song P Seto
- W.H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 313 Ferst Drive, Atlanta, GA, 30332, USA,
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17
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Tipton TE, Ray CS, Hand DR. Superficial digital flexor tendonitis in cutting horses: 19 cases (2007-2011). J Am Vet Med Assoc 2014; 243:1162-5. [PMID: 24094264 DOI: 10.2460/javma.243.8.1162] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To characterize superficial digital flexor (SDF) tendon lesions in the forelimbs of cutting horses and determine recurrence rate and prognosis for this condition. DESIGN Retrospective case series. ANIMALS 19 cutting horses with SDF tendonitis. PROCEDURES Medical records for horses evaluated for SDF tendonitis in 2007 through 2011 were reviewed. Data regarding age, sex, lameness grade, affected limb, and treatment were collected. Ultrasonographic images were reviewed, and lesion characteristics were recorded. Follow-up telephone interviews with owners or trainers were conducted to determine recurrence of SDF tendonitis, return of horse to its previous level of activity, and duration of the convalescent period. RESULTS All 19 horses initially evaluated for SDF tendonitis had similar lesions in the lateral aspect of the tendon. The right forelimb was affected in 11 horses, and the left forelimb was affected in 7 horses; 1 horse was affected in both forelimbs. Mean lameness grade was 1.26 (range, 0 to 3). Of 17 horses for which follow-up information was available, 3 had recurrence of tendon lesions and 1 developed a lesion in the contralateral forelimb SDF tendon; 16 horses returned to their previous level of activity. CONCLUSIONS AND CLINICAL RELEVANCE The location of SDF tendonitis in cutting horses appeared to be unique in that no central core lesions were detected ultrasonographically. Lesions at the periphery of the tendon may have an increased ability to heal, compared with lesions at the central core. Results suggested that cutting horses with SDF tendonitis have a better prognosis than that reported for affected racehorses.
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Affiliation(s)
- Tyler E Tipton
- Equine Sports Medicine and Surgery, 2991 W 1-20 S Frontage Rd, Weatherford, TX 76086
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18
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Tully LJ, Murphy AM, Smith RKW, Hulin-Curtis SL, Verheyen KLP, Price JS. Polymorphisms inTNCandCOL5A1genes are associated with risk of superficial digital flexor tendinopathy in National Hunt Thoroughbred racehorses. Equine Vet J 2013; 46:289-93. [DOI: 10.1111/evj.12134] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 06/27/2013] [Indexed: 01/21/2023]
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19
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Veres SP, Harrison JM, Lee JM. Repeated subrupture overload causes progression of nanoscaled discrete plasticity damage in tendon collagen fibrils. J Orthop Res 2013; 31:731-7. [PMID: 23255142 DOI: 10.1002/jor.22292] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 11/22/2012] [Indexed: 02/04/2023]
Abstract
A critical feature of tendons and ligaments is their ability to resist rupture when overloaded, resulting in strains or sprains instead of ruptures. To treat these injuries more effectively, it is necessary to understand how overload affects the primary load-bearing elements of these tissues: collagen fibrils. We have investigated how repeated subrupture overload alters the collagen of tendons at the nanoscale. Using scanning electron microscopy to examine fibril morphology and hydrothermal isometric tension testing to look at molecular stability, we demonstrated that tendon collagen undergoes a progressive cascade of discrete plasticity damage when repeatedly overloaded. With successive overload cycles, fibrils develop an increasing number of kinks along their length. These kinks-discrete zones of plastic deformation known to contain denatured collagen molecules-are accompanied by a progressive and eventual total loss of D-banding along the surface of fibrils, indicating a loss of native molecular packing and further molecular denaturation. Thermal analysis of molecular stability showed that the destabilization of collagen molecules within fibrils is strongly related to the amount of strain energy dissipated by the tendon after yielding during tensile overload. These novel findings raise new questions about load transmission within tendons and their fibrils and about the interplay between crosslinking, strain-energy dissipation ability, and molecular denaturation within these structures.
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Affiliation(s)
- Samuel P Veres
- School of Biomedical Engineering, Dalhousie University, 5981 University Avenue, PO Box 15000, Halifax, Nova Scotia, Canada B3H 4R2.
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TAKAHASHI T, YOSHIHARA E, MUKAI K, OHMURA H, HIRAGA A. Use of an implantable transducer to measure force in the superficial digital flexor tendon in horses at walk, trot and canter on a treadmill. Equine Vet J 2010:496-501. [DOI: 10.1111/j.2042-3306.2010.00285.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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21
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Takahashi T, Kasashima Y, Eto D, Mukai K, Hiraga A. Effect of uphill exercise on equine superficial digital flexor tendon forces at trot and canter. Equine Vet J 2010:435-9. [PMID: 17402462 DOI: 10.1111/j.2042-3306.2006.tb05583.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
REASONS FOR PERFORMING STUDY One cause of overstrain injury to the superficial digital flexor tendon (SDFT) in horses is the force loaded on the SDFT during repeated running. Therefore, decreasing this force may reduce SDFT injury. It has been reported that strain on the SDFT decreases with a toe-wedge shoe. Uphill courses are used for training of racehorses, and the angle of hoof-sole to the horizon during uphill running is similar to that of the toe-wedge shoe. OBJECTIVES To determine the effects of uphill exercise on the force on the SDFT during trotting and cantering. METHODS Arthroscopically implantable force probes (AIFP) were implanted into the SDFT of the left or right forelimb of 7 Thoroughbred horses and AIFP output recorded during trotting and cantering on a treadmill inclined at slopes of 0, 3 or 8%, and then 0% again. Superficial digital flexor tendon force was calculated as a relative value, with the amplitude of AIFP output voltage at initial 0% slope equal to 100. RESULTS Out of 14 sets of experiments, AIFP data were analysed successfully in 9 at the trot, in 3 at the canter in the trailing forelimb on a slope of 3 and 8%, and in 2 at the canter in the leading forelimb on a slope of 3%. Increasing the incline from 0-8% tended to decrease peak force in the SDFT at the trot, and in the trailing forelimb at the canter. However, force in the SDFT was unchanged in the leading forelimb at the canter on the 3% incline. CONCLUSIONS The force in the SDFT trotting or cantering uphill is unchanged or lower than that loaded at the same speed on a flat surface. Because at similar speeds the workload for uphill exercise is greater than on the flat, uphill running increases exercise intensity without increasing force in the SDFT. POTENTIAL RELEVANCE Uphill exercise may reduce the risk of SDFT injury as both running speed and SDFT force are decreased on an incline as compared to the flat, even when exercise intensity is the same. Further study is needed to confirm these findings at canter in a larger population of horses.
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Affiliation(s)
- T Takahashi
- Equine Research Institute, Japan Racing Association, 321-4 Tokami-cho, Utsunomiya, Tochigi 320-0856, Japan
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Effects of exercise on tenocyte cellularity and tenocyte nuclear morphology in immature and mature equine digital tendons. Equine Vet J 2010; 40:141-6. [DOI: 10.2746/042516408x266097] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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23
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Superficial digital flexor tendon lesions in racehorses as a sequela to muscle fatigue: A preliminary study. Equine Vet J 2010; 39:540-5. [DOI: 10.2746/042516407x212475] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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24
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Moffat PA, Firth EC, Rogers CW, Smith RKW, Barneveld A, Goodship AE, Kawcak CE, McIlwraith CW, van Weeren PR. The influence of exercise during growth on ultrasonographic parameters of the superficial digital flexor tendon of young Thoroughbred horses. Equine Vet J 2008; 40:136-40. [PMID: 18093890 DOI: 10.2746/042516408x253109] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
REASON FOR PERFORMING STUDY Conditioning by early training may influence the composition of certain musculoskeletal tissues, but very few data exist on its effect during growth on tendon structure and function. OBJECTIVES To investigate whether conditioning exercise in young foals would lead to any ultrasonographically detectable damage to the superficial digital flexor tendon or an increase in cross-sectional area (CSA). METHODS Thirty-three Thoroughbred foals reared at pasture were allocated to 2 groups: control (PASTEX) allowed exercise freely at pasture; and CONDEX, also at pasture, began conditioning exercise from mean age 21 days over 1030 m on a purpose-built oval grass track, for 5 days/week until mean age 18 months. Foals were observed daily, and underwent orthopaedic examination monthly. Ultrasonographic images of the superficial digital flexor tendon (SDFT) at the mid-metacarpal level of both forelimbs were obtained in all foals at ages 5, 8, 12, 15 and 18 months. CSA was validated (r(2) = 0.89) by determining CSA from digital photographs of the transected SDFT surface from 12 of the horses necropsied at age 17.1 months. RESULTS here was no clinical or ultrasonographic evidence of tendonopathy in either group and the greatest increase in mean CSA in both groups occurred between age 5 and 8 months. Across all age categories, there was no significant difference in mean CSA between the left and right limbs, or colts and fillies; there was a trend towards a larger CSA in the CONDEX group (P = 0.058). CONCLUSIONS There was no conclusive evidence for a structural adaptive hypertrophy of the SDFT, probably because the regimen was insufficiently rigorous or because spontaneous pasture exercise may induce maximal development of energy storing tendons. POTENTIAL RELEVANCE A moderate amount of early conditioning exercise against a background of constant exercise at pasture is not harmful to the development of the flexor tendons.
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Affiliation(s)
- P A Moffat
- Institute of Veterinary and Animal Biomedical Sciences, Massey University, Palmerston North, New Zealand
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Patterson-Kane JC, Firth EC. The pathobiology of exercise-induced superficial digital flexor tendon injury in Thoroughbred racehorses. Vet J 2008; 181:79-89. [PMID: 18406184 DOI: 10.1016/j.tvjl.2008.02.009] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Revised: 02/11/2008] [Accepted: 02/12/2008] [Indexed: 12/21/2022]
Abstract
Despite the high incidence of superficial digital flexor tendon (SDFT) injury in racehorses, the pathobiology of the condition is not clearly defined. The SDFT improves locomotor efficiency by storing elastic energy, but as a result it has low mechanical safety margins. As with the Achilles tendon in humans, rupture during athletic activity often follows accumulation of exercise and age-induced degenerative change that is not repaired by tenocytes. There is limited understanding of tenocyte biology and pathology, including responses to high mechanical strains and core temperatures during exercise. Unfortunately, much of the current information on SDFT pathology is derived from studies of collagenase-induced injury, which is a controversial model. Following rupture the overlapping phases of reactive inflammation, proliferation, remodelling and maturation do not necessarily reconstitute normal structure and function, resulting in long-term persistence of scar tissue and high re-injury rates. Tissue engineering approaches are likely to be applicable to SDFT lesions, but will require significant advances in cell biology research.
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Affiliation(s)
- Janet C Patterson-Kane
- School of Veterinary Science, The University of Queensland, St. Lucia, Queensland 4072, Australia.
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Smith RK, Goodship AE. The Effect of Early Training and the Adaptation and Conditioning of Skeletal Tissues. Vet Clin North Am Equine Pract 2008; 24:37-51. [DOI: 10.1016/j.cveq.2007.11.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Kasashima Y, Takahashi T, Birch HL, Smith RKW, Goodship AE. Can exercise modulate the maturation of functionally different immature tendons in the horse? J Appl Physiol (1985) 2008; 104:416-22. [DOI: 10.1152/japplphysiol.00379.2007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Tendons can be considered in two functional groups, those contributing to energetics of locomotion and those acting solely to position the limb. The energy-storing tendons in both human and equine athletes have a high frequency of injury with similar pathophysiology. In previous studies, high-intensity exercise appears to induce a disruption of the matrix rather than functional adaptation in adults. Here we explore the hypothesis that the introduction of controlled exercise during growth would result in an adaptive response without deleterious effects. Young horses were given a controlled exercise program similar to that previously shown to induce matrix changes in energy-storing tendons of skeletally mature animals. The tendons were assessed in relation to mechanical properties, molecular composition, and morphology. Results showed a significant increase in cartilage oligomeric matrix protein (COMP) in the positional tendon but not in the energy-storing tendon. Other matrix properties and mechanical properties were not significantly changed. While the imposition of high-strain-rate exercise in immature horses failed to augment the development of the energy-storing tendon over and above that induced by normal pasture exercise, it did not induce deleterious changes, supporting an earlier introduction of athletic training in horses.
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O’Sullivan CB. Injuries of the Flexor Tendons: Focus on the Superficial Digital Flexor Tendon. ACTA ACUST UNITED AC 2007. [DOI: 10.1053/j.ctep.2007.08.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
Horses can gallop within hours of birth, and may begin training for athletic competition while still growing. This review cites studies on the effects of exercise on bone, tendon and articular cartilage, as detected by clinical and research imaging techniques, tissue biochemical analysis and microscopy of various kinds. For bone, alterations in bone mineral content, mineral density and the morphology of the mineralized tissue are the most common end-points. Apparent bone density increases slightly after athletic training in the cortex, but substantially in the major load paths of the epiphyses and cuboidal bones, despite the lower material density of the new bone, which is deposited subperiosteally and on internal surfaces without prior osteoclastic resorption. With training of greater intensity, adaptive change is supervened by patho-anatomical change in the form of microdamage and frank lesions. In tendon, collagen fibril diameter distribution changes significantly during growth, but not after early training. The exact amount and type of protracted training that does cause reduction in mass average diameter (an early sign of progressive microdamage) have not been defined. Training is associated with an increase in the cross-sectional area of some tendons, possibly owing to slightly greater water content of non-collagenous or newly synthesized matrix. Early training may be associated with greater thickness of hyaline but not calcified articular cartilage, at least in some sites. The age at which adaptation of cartilage to biomechanical influences can occur may thus extend beyond very early life. However, cartilage appears to be the most susceptible of the three tissues to pathological alteration. The effect of training exercise on the anatomical or patho-anatomical features of connective tissue structures is affected by the timing, type and amount of natural or imposed exercise during growth and development which precedes the training.
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Affiliation(s)
- Elwyn C Firth
- Institute of Veterinary, Animal and Biological Sciences, Massey University, Palmerston North, New Zealand.
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Dowling BA, Dart AJ. Mechanical and functional properties of the equine superficial digital flexor tendon. Vet J 2005; 170:184-92. [PMID: 16129339 DOI: 10.1016/j.tvjl.2004.03.021] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2004] [Indexed: 11/15/2022]
Abstract
The in vitro and in vivo mechanical properties of the superficial digital flexor tendon have been described. To date the focus has been on single load to failure testing, however refined in vivo methods may prove useful to evaluate the effects of treatment and exercise on tendons. During maximal exercise, the adult superficial digital flexor tendon operates close to its functional limits with a narrow biomechanical safety margin. This combined with exercise and age associated microdamage, and a limited adaptive ability may increase the risk of fatigue failure. Studies evaluating treatment regimens for tendonitis have focused on repair and regeneration and yielded varying results. It would appear that the superficial digital flexor tendon has a limited ability if any to adapt positively to exercise after maturity. In contrast, the foal's superficial digital flexor tendon may have a greater adaptive ability and may respond to an appropriate exercise regimen to produce a more functionally adapted tendon. Recent studies have shown that foals allowed free pasture exercise develop a larger, stronger, more elastic tendon compared to foals that were confined or subjected to a training program. Effects on the non-collagenous matrix appear to be responsible for these differences. In contrast, training or excess exercise may have permanent detrimental effects on the biomechanical and functional properties of the superficial digital flexor tendon in the foal. The implication is that the determination of optimum exercise intensity and timing, and the role of the non-collagenous matrix in tendon physiology in the young horse may hold the key to developing tendons more capable of resisting injury.
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Affiliation(s)
- B A Dowling
- University Veterinary Centre Camden, Faculty of Veterinary Science, University of Sydney, Werombi Road, Camden, NSW 2570, Australia
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Abstract
This article examines basic tendon biomechanics, the anatomy and mechanics of digital flexor tendons, and the digital flexor pulley system. It also explores the various models that have tried to simulate the motion of the flexor tendons and several testing modalities that have been used. Finally, clinical applications are considered, including the biomechanics of flexor tendon repairs and tendon transfers. As we reach limits in the care of flexor tendon injuries, research into molecular, biochemical, and micromechanical methods of tendon repair will become the forefront of future investigation.
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Affiliation(s)
- Howard J Goodman
- Department of Orthopaedic Surgery, Maimonides Medical Center, 927 49th Street, Brooklyn, NY 11219, USA.
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Rogers CW, Firth EC. Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 2. Measurement error and effect of training stage on the relationship between objective and subjective criteria of training workload. N Z Vet J 2004; 52:272-9. [PMID: 15768123 DOI: 10.1080/00480169.2004.36439] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
AIM To identify the magnitude and sources of error involved in simply quantifying the workload of a group of Thoroughbred racehorses in training. METHODS Data were obtained from seven 2-year-old fillies trained for 13 weeks on sand and grass tracks at various cantering velocities, and at the gallop in the last 4 weeks. Four fillies completed training and comprised a 'high exercise intensity' subgroup; three fillies did not complete all gallops due to lameness or injury and comprised a 'medium exercise intensity' subgroup. The trainer recorded the distance, time, track used, and subjective gait (SG; viz canter, 1/4-pace, 1/2-pace and gallop) of each horse each day. Data were analysed to describe the training programme and sources of variation in workload. A cumulative workload index (CWI) was devised to simply express distance and velocity aspects of the training programme. RESULTS The magnitude of errors in measurement of timing and distance were small but significant (<0.8%, p=0.01). SG was an inaccurate descriptor of velocity. Mean velocity of 1/2-pace decreased from 8.92 (SE 0.049) in Weeks 6-8 to 6.33 (SE 0.061) m/sec after the start of galloping sessions in Week 9 (p=0.01). Track surface had a significant effect on the velocity of 1/2-pace (p=0.001). The fastest velocity was recorded on the grass (9.06, SE 0.292 m/sec), followed by 'plough' (8.23, SE 0.152 m/sec), and sand (7.90, SE 0.132 m/sec) tracks. The CWI of the horses ranged between 1,085,000 and 1,634,000 (mean=1,428,000; SE 78,000). The average exercise intensity per week was 110,000 (SE 1,048). There were no significant differences between high and medium exercise intensity subgroups for the canter and 1/4-pace. The high exercise subgroup had a greater CWI for the 1/2-pace (839,000 vs 559,000; p=0.004), gallop (71,000 vs 31,000; p=0.001), and total index (1,580,000 vs 1,242,000; p=0.001). CONCLUSIONS The workload history of a horse can be accurately described using an index based on manual measurement of the time and distance worked. CLINICAL RELEVANCE Accurate and precise data on the training programme of performance horses are likely to enable greater differentiation of aspects of workload which are associated with both performance and injury.
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Affiliation(s)
- C W Rogers
- Epicentre, Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
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Takahashi T, Kasashima Y, Ueno Y. Association between race history and risk of superficial digital flexor tendon injury in Thoroughbred racehorses. J Am Vet Med Assoc 2004; 225:90-3. [PMID: 15239479 DOI: 10.2460/javma.2004.225.90] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine whether race history, including the number of races and total race distance, was associated with risk of superficial digital flexor tendon (SDFT) injury in Thoroughbred racehorses in Japan. DESIGN Matched case-control study. ANIMALS 515 Thoroughbred racehorses (case horses) that sustained an SDFT injury during training or racing in Japan during 2002 and 951 horses (control horses) without SDFT injury that were matched with case horses on the basis of age and month of the latest race. PROCEDURE Variables related to race history were compared between case and control horses by means of conditional logistic regression. RESULTS The odds of SDFT injury increased as mean race distance and mean body weight at race time increased. Compared with females that had never competed in steeplechase races, males regardless of steeplechase race history and females that had competed in steeplechase races had higher odds of SDFT injury. CONCLUSIONS AND CLINICAL RELEVANCE Results suggest that longer mean distance per race, heavier mean body weight at race time, steeplechase experience, and sex (male) increased the risk of SDFT injury in Thoroughbred racehorses.
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Affiliation(s)
- Toshiyuki Takahashi
- Equine Research Institute, Japan Racing Association, 321-4 Tokami-cho, Utsunomiya-shi, Tochigi 320-0856, Japan
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Kjaer M. Role of extracellular matrix in adaptation of tendon and skeletal muscle to mechanical loading. Physiol Rev 2004; 84:649-98. [PMID: 15044685 DOI: 10.1152/physrev.00031.2003] [Citation(s) in RCA: 953] [Impact Index Per Article: 47.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The extracellular matrix (ECM), and especially the connective tissue with its collagen, links tissues of the body together and plays an important role in the force transmission and tissue structure maintenance especially in tendons, ligaments, bone, and muscle. The ECM turnover is influenced by physical activity, and both collagen synthesis and degrading metalloprotease enzymes increase with mechanical loading. Both transcription and posttranslational modifications, as well as local and systemic release of growth factors, are enhanced following exercise. For tendons, metabolic activity, circulatory responses, and collagen turnover are demonstrated to be more pronounced in humans than hitherto thought. Conversely, inactivity markedly decreases collagen turnover in both tendon and muscle. Chronic loading in the form of physical training leads both to increased collagen turnover as well as, dependent on the type of collagen in question, some degree of net collagen synthesis. These changes will modify the mechanical properties and the viscoelastic characteristics of the tissue, decrease its stress, and likely make it more load resistant. Cross-linking in connective tissue involves an intimate, enzymatical interplay between collagen synthesis and ECM proteoglycan components during growth and maturation and influences the collagen-derived functional properties of the tissue. With aging, glycation contributes to additional cross-linking which modifies tissue stiffness. Physiological signaling pathways from mechanical loading to changes in ECM most likely involve feedback signaling that results in rapid alterations in the mechanical properties of the ECM. In developing skeletal muscle, an important interplay between muscle cells and the ECM is present, and some evidence from adult human muscle suggests common signaling pathways to stimulate contractile and ECM components. Unaccostumed overloading responses suggest an important role of ECM in the adaptation of myofibrillar structures in adult muscle. Development of overuse injury in tendons involve morphological and biochemical changes including altered collagen typing and fibril size, hypervascularization zones, accumulation of nociceptive substances, and impaired collagen degradation activity. Counteracting these phenomena requires adjusted loading rather than absence of loading in the form of immobilization. Full understanding of these physiological processes will provide the physiological basis for understanding of tissue overloading and injury seen in both tendons and muscle with repetitive work and leisure time physical activity.
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Affiliation(s)
- Michael Kjaer
- Sports Medicine Research Unit, Department of Rheumatology, Copenhagen University Hospital at Bispebjerg, 23 Bispebjerg Bakke, DK-2400 Copenhagen NV, Denmark.
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Zarucco L, Swanstrom MD, Driessen B, Hawkins D, Hubbard M, Steffey EP, Stover SM. An in vivo equine forelimb model for short-term recording of peak isometric force in the superficial and deep digital flexor muscles. Vet Surg 2004; 32:439-50. [PMID: 14569572 DOI: 10.1053/jvet.2003.50058] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To develop and test an experimental model for in vivo short-term recording of peak isometric forces of the digital flexor muscles in the forelimb of adult horses. STUDY DESIGN In vivo experimental study. SAMPLE POPULATION Four healthy, anesthetized, adult Thoroughbred horses (3 to 7 years old; 527 +/- 87 kg) METHODS In dorsal recumbency, ulnar and median nerves were exposed and instrumented with insulated bipolar cuff stimulation electrodes for later connection to an electrical stimulator. In left lateral recumbency, a biplanar fixator was applied to the right humerus and a custom-made, rigid, aluminum frame connected to it, to allow loading of muscles distal to the fixator. Threaded transfixation pins through the radial and metacarpal condyles were clamped to the rigid frame so that the humerus, radius, ulna, and metacarpus were fixed in position. Each digital flexor muscle insertion tendon was transected just above the metacarpophalangeal joint, extracted from the carpal canal, and secured in a metal clamp positioned at the distal myotendinous (MT) junction. Distally, the clamp was connected in series to a load cell and a pneumatic actuator to record force and to maintain muscle length during nerve stimulation. A linear potentiometer was connected in parallel to the actuator to record MT junction position. Initial trials were conducted to identify median and ulnar nerve stimulation variables to achieve maximal muscle contraction. Isometric contractions were performed at different muscle lengths and peak forces registered during 3 seconds of supramaximal dual (ulnar and median) nerve stimulation. RESULTS A stimulation voltage of 2.5 to 5.0 V at 50 Hz usually produced maximal force for both the superficial digital flexor (SDF) and deep digital flexor (DDF) muscles. Single ulnar and median nerve stimulation elicited force development not only in the DDF muscle but also in the SDF muscle. At voltages higher than 1 V, normalized force was greatest with combined median and ulnar nerve stimulation for both the DDF and SDF muscles; however, normalized force was greater for median nerve stimulation than ulnar nerve stimulation in the DDF muscle, and the opposite relationship was observed for the SDF muscle. Final recording of dual supramaximal nerve stimulation of SDF and DDF muscles resulted in peak isometric forces of 716 +/- 192 N and 1,577 +/- 203 N, respectively. CONCLUSIONS The instrumentation technique and experimental protocol enabled recording of peak isometric forces in the SDF and DDF muscles of anesthetized adult horses. CLINICAL RELEVANCE Studies using this model will improve knowledge of SDF and DDF muscle mechanics with insight to functional implications of the complex architecture of these muscles. Knowledge of the dynamic performance of the SDF and DDF muscles would also be useful for the development of new treatment strategies for flexor deformities and tendon injuries in horses.
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Affiliation(s)
- Laura Zarucco
- Veterinary Medical Teaching Hospital, Biomedical Engineering Graduate Group, the Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA, USA
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Hayashi K, Frank JD, Hao Z, Schamberger GM, Markel MD, Manley PA, Muir P. Evaluation of ligament fibroblast viability in ruptured cranial cruciate ligament of dogs. Am J Vet Res 2003; 64:1010-6. [PMID: 12926594 DOI: 10.2460/ajvr.2003.64.1010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine fibroblast viability, assess development of apoptosis, and evaluate tissue hypoxia via histochemical, in-situ hybridization, or immunohistochemical staining in ruptured and intact cranial cruciate ligaments (CCLs) of dogs. ANIMALS 32 dogs with ruptured CCLs, and 8 aged and 19 young dogs with intact CCLs. PROCEDURE Markers of cell viability (lactate dehydrogenase [LDH]), apoptosis (terminal deoxynucleatidyl transferase-mediated deoxyuridine triphosphate-nick end labeling [TUNEL] method), and hypoxia (hypoxia-inducible factor-1alpha [HIF-1alpha] monoclonal antibody) were applied to CCL specimens; positive cells were assessed objectively (LDH) and subjectively (TUNEL and HIF-1alpha) in the main axial tissue component (core) and synovial intima and subintima (epiligamentous tissue). RESULTS Viable fibroblasts were seen in all intact and ruptured CCLs. More nonviable cells were found in the core regions of ruptured CCLs and intact CCLs of young dogs than in the epiligamentous regions. Number of nonviable cells in the core region of ruptured CCLs was greater than that in intact CCLs of young and aged dogs, whereas the number in the epiligamentous region was similar in all specimens. The TUNEL and HIF-1alpha staining was only found in the epiligamentous region of ruptured CCLs. CONCLUSIONS AND CLINICAL RELEVANCE Ruptured CCLs contained a high number of nonviable cells but not a great number of apoptotic cells. Repair processes in the epiligamentous region of the CCL include a metabolic response to hypoxia, suggesting that necrosis of ligament fibroblasts and transformation of surviving cells to a spheroid phenotype may be a response to hypoxia cause by microinjury or inadequate blood flow.
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Affiliation(s)
- Kei Hayashi
- Comparative Orthopaedic Research Laboratory, University of Wisconsin-Madison, School of Veterinary Medicine, 2015 Linden Dr, Madison, WI 53706, USA
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Hayashi K, Frank JD, Dubinsky C, Zhengling H, Markel MD, Manley PA, Muir P. Histologic changes in ruptured canine cranial cruciate ligament. Vet Surg 2003; 32:269-77. [PMID: 12784204 DOI: 10.1053/jvet.2003.50023] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVES To determine changes to the cells and collagenous and amorphous extracellular matrix (ECM) structure in ruptured canine cranial cruciate ligaments (CCL). STUDY DESIGN Prospective clinical study. ANIMALS CCL specimens obtained from 29 dogs with ruptured CCL and 6 young dogs with intact CCL. METHODS Ligament fibroblast number density and phenotype were determined in the core and epiligamentous regions. ECM birefringence and crimp structure in the core region were also studied. RESULTS Loss of fibroblasts from the core region of ruptured CCL was seen (P <.001), whereas, in the epiligamentous region, cell number densities were similar in ruptured and intact CCL (P =.7). In ruptured CCL, numbers of typical ligament fibroblasts (fusiform and ovoid cells) were decreased, and numbers of cells exhibiting chondroid transformation (spheroid cells) were increased in the core region (P <.001). Expansion of the volume of the epiligamentous region was also seen, although bridging scar tissue was not seen between the ends of ruptured CCL. The structure of the ECM collagen in the core region was extensively disrupted in ruptured CCL. This was, in part, because of decreased birefringence and elongation of the crimp in the remaining collagen fibers when compared with intact CCL (P <.01). CONCLUSIONS Extensive alterations to the cell populations and collagenous ECM structure were seen in ruptured CCL. Although a proliferative epiligamentous repair response was seen in ruptured CCL, there was a lack of any bridging scar between the ruptured ends of the CCL. CLINICAL RELEVANCE The cellular and ECM changes in ruptured CCL that we have described appear to result from the cumulative effects of remodeling and adaptation to mechanical loading and microinjury. Treatment of early cruciate disease in dogs will need to inhibit or reverse these progressive changes to CCL tissue, which are directly associated with partial or complete structural failure of the CCL under conditions of normal activity.
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Affiliation(s)
- Kei Hayashi
- Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, USA
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Gibson KT, Burbidge HM, Robertson ID. The effects of polyester (terylene) fibre implants on normal equine superficial digital flexor tendon. N Z Vet J 2002; 50:186-94. [PMID: 16032269 DOI: 10.1080/00480169.2002.36309] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
AIM To determine the effect of polyester (terylene) fibre implants on normal equine superficial digital flexor (SDF) tendon structure. METHODS Normal forelimb SDF tendons (n=24) of 12 horses were divided into unoperated, sham-operated, and implanted (terylene fibre implant) groups. Horses were assessed for lameness and ultrasonographic changes to SDF tendons at intervals up to 48 weeks post-operatively. After euthanasia, SDF tendons were collected for histological and ultrastructural examination. Histological sections were examined for alcian blue staining intensity, cellularity, fibril bundle alignment, fascicle separation and crimp morphology. Mass-average diameters (MADs) of collagen fibrils were calculated from electron micrographs and compared between treatment groups. RESULTS Insertion of terylene fibre implants resulted in short-term (8 weeks) lameness in implanted limbs. Ultrasonographically, the implants could be detected in 50% of implanted tendons, but were associated with tendon swelling and the presence of hypoechoic core lesions in 7/8 implanted limbs. There were significant alterations in alcian blue staining, cellularity and crimp morphology in the central fascicles of sham-operated and implanted tendons, and alteration in fibril alignment in the central fascicles of implanted tendons. Unoperated tendons remained histologically normal. MADs of collagen fibrils did not differ between sham-operated, implanted and unoperated limbs. CONCLUSIONS Both the sham procedure and the insertion of terylene fibre implants led to alterations in tendon structure that persisted for up to 48 weeks. Persistence of disorganised connective tissue at the proximal and distal ends of the terylene fibre implants may predispose implanted tendons to continued risk of injury. CLINICAL RELEVANCE It is unlikely that terylene fibre implants offer any advantage over standard non-surgical treatments for mild to moderate cases of SDF tendonitis in the horse.
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Affiliation(s)
- K T Gibson
- Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
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Takahashi T, Kai M, Hada T, Eto D, Muka K, Ishida N. Biomechanical implications of uphill training on the aetiology of tendinitis. Equine Vet J 2002:353-8. [PMID: 12405715 DOI: 10.1111/j.2042-3306.2002.tb05447.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It has been reported that a small decrease in the strain in the superficial digital flexor tendon (SDFT) occurs if the toe is raised during walking. Although walking on a slope appears similar to raising the toe, it is unclear whether uphill exercise decreases the strain in the SDFT. Because the force or strain on tendons is one of the important factors leading to tendon stress injury, we hypothesised that reducing the force in the SDFT during exercise may prevent tendinitis. The purpose of this study was to determine the effects of treadmill inclination on the force in the SDFT in the walking horse. 'Arthroscopically implantable force probes' (AIFP) were implanted into the SDFT of the forelimb of 4 horses. The AIFP output was recorded during walking on a treadmill inclined at 0%, 3%, 8% and then 0% again. When the inclination increased from 0 to 8%, the first peak of force in the SDFT decreased significantly, the second increased significantly, but the maximal force and the area under the force-time curve did not change. In conclusion, uphill walking on an inclined treadmill did not decrease the maximal force in the SDFT or the area under the force-time curve, however, the patterns of force were altered. Future research should focus on the force distributions of tendons and ligaments at faster gaits, because the effects of a change in hoof angle and slope may be greater at faster gaits.
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Affiliation(s)
- T Takahashi
- Equine Research Institute, Japan Racing Association, Utsunomiya, Tochigi
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Dowling BA, Dart AJ, Hodgson DR, Rose RJ, Walsh WR. Recombinant equine growth hormone does not affect the in vitro biomechanical properties of equine superficial digital flexor tendon. Vet Surg 2002; 31:325-30. [PMID: 12094346 DOI: 10.1053/jvet.2002.33591] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To evaluate the effect of recombinant equine growth hormone (rEGH) on the in vitro biomechanical properties of normal adult equine superficial digital flexor tendon (SDFT). STUDY DESIGN Completely randomized design. SAMPLE POPULATION Nine Standardbred horses, 6 to 9 years of age with ultrasonographically normal forelimb SDFT. METHODS Six horses were administered intramuscular (IM) rEGH at 10 microg/kg/day for 1 week, and then 20 microg/kg/day for another 5 weeks; 3 horses (control subjects) were administered an equivalent daily volume of sterile water IM. Horses were killed at the end of the 6-week treatment period, and both forelimb SDFT were harvested and stored at -70 degrees C. In vitro biomechanical testing was performed under uniaxial tension. Results were analyzed using a general linear model of analysis of variance; significance was set at P <.05. RESULTS There were no differences in cross-sectional area, maximal load at failure, yield load, ultimate and yield tensile strain, ultimate and yield tensile stress, or stiffness between tendons from control and treated horses. CONCLUSIONS Administration of rEGH to adult Standardbred horses for 6 weeks had no detectable effect on the in vitro biomechanical properties of normal SDFT. CLINICAL RELEVANCE Administration of rEGH does not modulate the in vitro biomechanical properties of SDFT from adult Standardbred horses.
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Affiliation(s)
- Bradley A Dowling
- University Veterinary Centre Camden, Department of Veterinary Clinical Sciences, Sydney University, Australia
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41
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Magnusson SP, Qvortrup K, Larsen JO, Rosager S, Hanson P, Aagaard P, Krogsgaard M, Kjaer M. Collagen fibril size and crimp morphology in ruptured and intact Achilles tendons. Matrix Biol 2002; 21:369-77. [PMID: 12128074 DOI: 10.1016/s0945-053x(02)00011-2] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The present study examined the hypothesis that collagen fibril diameter and crimp angle in ruptured human Achilles tendons differed from that of intact ones. Tissue samples were obtained from the central core (distal core) and the posterior periphery (distal superficial) at the rupture site, and the proximally intact (proximal superficial) part of the tendon in 10 subjects (38+/-8 years) with a complete tendon rupture. For comparisons corresponding tissue samples were procured from age (38+/-7 years) and gender matched intact Achilles tendons during routine forensic autopsy. The cross-sectional area density and diameter distribution of fibrils were analyzed using stereological techniques of digitized electron microscopy biopsy cross-sections, while crimp angle was measured by the changing banding pattern of collagen fibers when rotated between crossed polars. Nine of 10 persons with tendon ruptures reported that the injury did not occur during exceedingly large forces, and none experienced any symptoms in the days or months prior to the injury. Fibril diameter distribution showed no region-specific differences in either the ruptured or intact tendons for either group. However, in the distal core there were fewer fibrils in the ruptured compared to the intact tendons in 60-150 nm range, P<0.01. Similarly, in the distal superficial portion there were fewer fibrils in the ruptured compared to the intact tendons in the 90-120 nm range, 2P<0.05, while there were no differences in the proximal superficial tendons. Crimp angle did not display any region-specific differences, or any difference between the rupture and intact tendons. In conclusion, these data suggest that although crimp morphology is unchanged there appears to be a site-specific loss of larger fibrils in the core and periphery of the Achilles tendon rupture site. Moreover, the lack of symptoms prior to the rupture suggests that clinical tendinopathy is not an etiological factor in complete tendon ruptures.
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Affiliation(s)
- S P Magnusson
- Team Danmark Test Center, Bispebjerg Hospital, Bispebjerg bakke 23, 2400 NV, Copenhagen, Denmark.
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42
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Cherdchutham W, Meershoek LS, van Weeren PR, Barneveld A. Effects of exercise on biomechanical properties of the superficial digital flexor tendon in foals. Am J Vet Res 2001; 62:1859-64. [PMID: 11763171 DOI: 10.2460/ajvr.2001.62.1859] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine the effects of exercise on biomechanical properties of the superficial digital flexor tendon (SDFT) in foals. ANIMALS 43 Dutch Warmblood foals. PROCEDURE From 1 week until 5 months of age, 14 foals were housed in stalls and not exercised, 14 foals were housed in stalls and exercised daily, and 15 foals were maintained at pasture. Eight foals in each group were euthanatized at 5 months, and remaining foals were housed together in a stall and paddock until euthanatized at 11 months. After euthanasia, SDFT were isolated and fit in a material testing system. Mean cross-sectional area (CSA) was measured and traction forces recorded. Normalized force at rupture (force(rup)), normalized force at 4% strain, strain at rupture, stress at 4% strain (stress(4%stain)), and stress at rupture were compared among and within groups. RESULTS At 5 months, mean CSA and normalized force(rup) were significantly greater and stress(4%strain) significantly less in the pastured group, compared with the other groups. At 11 months, CSA and normalized force(rup) were not significantly different among groups, because force(rup) increased significantly from 5 to 11 months in the nonexercised group and decreased significantly in the pastured group. CONCLUSIONS AND CLINICAL RELEVANCE Exercise significantly affected the biomechanical properties of the SDFT in foals. Evenly distributed moderate- and low-intensity exercise at a young age may be more effective for development of strong, flexible tendons in horses than single episodes of high-intensity exercise superimposed on stall rest. This effect may impact later susceptibility to SDFT injury.
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Affiliation(s)
- W Cherdchutham
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, The Netherlands
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43
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Abstract
The superficial digital flexor tendon (SDFT) is an elastic structure that during maximal exercise appears to operate close to its functional limits. The biomechanical and biochemical responses to exercise, injury, and healing are still poorly understood but ongoing research is providing valuable new information which is addressed in this review. It appears that the SDFT matures early, after which time it has limited ability to adapt to stress and undergoes progressive degeneration. Focal hypocellularity, collagen fibril degeneration, selective fibril loading and alterations in the noncollagenous matrix occur primarily within the central core region of the midmetacarpal segment. Current treatment strategies have had equivocal results in returning animals to optimal athletic activity. To date it would seem that progressive rehabilitation programmes coupled with regular ultrasonographic evaluations are a cost-effective and comparable strategy when compared to surgical treatment methods. Recent interest in pharmacological modulation of intrinsic healing of collagenous structures has led to the investigation of various growth factors as potential therapeutic aids in the healing of tendon injuries. However, one of the major goals in tendon research, and one which holds the most optimism for success in the immediate future, is the prevention of tendon injuries.
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Affiliation(s)
- B A Dowling
- University Veterinary Centre Camden, Department of Veterinary Clinical Sciences, NSW, Australia
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Birch HL, McLaughlin L, Smith RK, Goodship AE. Treadmill exercise-induced tendon hypertrophy: assessment of tendons with different mechanical functions. Equine Vet J 1999:222-6. [PMID: 10659256 DOI: 10.1111/j.2042-3306.1999.tb05222.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The equine superficial digital flexor tendon (SDFT) functions as an energy store during high-speed gaits reducing the energetic cost of locomotion. To enable the SDFT to function effectively, the appropriate mechanical properties are essential. We tested the hypothesis that the SDFT does not undergo gross hypertrophy in response to high-intensity exercise whereas tendons not involved in energy storage undergo adaptive hypertrophy. Two groups (n = 6) of Thoroughbred fillies were trained at high-intensity on a high-speed equine treadmill for 5 months (short-term study) or 18 months (long-term study). Age-matched groups (n = 6) of horses undertook low-intensity exercise only for the same time period. Throughout the short-term study the SDFT and deep digital flexor tendon (DDFT) were ultrasonograpically scanned at mid-metacarpal level and cross-sectional area (CSA) calculated. At the end of the short-term study (horse age = 2 years) and long-term study (horse age = 3 years) the left SDFT, DDFT, suspensory ligament (SL) and common digital extensor tendon (CDET) were harvested and CSA calculated. Comparison of the DDFT from 2- and 3-year-old horses revealed an age-related increase in CSA which was confirmed by ultrasonographs. Post mortem analysis showed a significant hypertrophy of the CDET with high-intensity training in the short-term study (younger horses). CSA did not differ significantly between training groups for any of the structures following long-term training. These results suggest a structure specific hypertrophic response to the imposed training regime.
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Affiliation(s)
- H L Birch
- Royal Veterinary College, University of London, North Mymms, Hatfield, UK
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Smith RK, Birch H, Patterson-Kane J, Firth EC, Williams L, Cherdchutham W, van Weeren WR, Goodship AE. Should equine athletes commence training during skeletal development?: changes in tendon matrix associated with development, ageing, function and exercise. Equine Vet J 1999:201-9. [PMID: 10659252 DOI: 10.1111/j.2042-3306.1999.tb05218.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In human athletes, conditioning, training and competition are commenced before skeletal maturity. Yet in equine athletics, racing of young (age 2 years) horses remains contentious. Tendon injury persists as major causes of wastage in equine athletes. Minimising injury and associated welfare issues could involve a radical approach to the timing and implementation of conditioning and training. Tendons were examined from Thoroughbreds, Dutch Warmblood foals, working horses and also a group of wild horses to evaluate effects of age, function and exercise. Gross mechanical properties did not differ significantly with age or exercise, but showed a high variance within each group. Mechanical properties of tendon tissue showed significant differences as a function of age and location. The collagen fibril crimp angle and length showed a regional reduction in the central core with exercise and age, with a synergistic effect. Regional differences in collagen fibril diameter were seen in long-term exercised older horses, but not in short-term exercised, or younger, horses. The higher proportion of small fibrils in the central region of the long-term exercised horses did not correlate with new collagen formation and therefore appear to result from disassembly of the larger diameter fibrils. Fibril diameter distributions were influenced by exercise regimens in the growing foal. Changes in molecular composition occurred in longer-term exercise and older horses, in the centre of the tendon, with higher levels of type III collagen and changes in glycosaminoglycan (GAG) content. Cartilage Oligomeric Matrix Protein (COMP) levels also appear to be modulated by age, function and superimposition of exercise. These changes were all exacerbated with age and exercise, suggesting appropriate exercise in young horses may lead to a lower incidence of injury than in older horses. An hypothesis is advanced that immature tendon can respond to exercise while mature tendon has limited, if any, ability to do so. These findings support potentially controversial earlier conditioning and racing of younger, rather than older, equine athletes.
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Affiliation(s)
- R K Smith
- Royal Veterinary College, Hatfield, Herts, UK
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