Stifle extension results in differential tensile forces developing between abaxial and axial components of the cranial meniscotibial ligament of the equine medial meniscus: a mechanistic explanation for meniscal tear patterns

Arthroscopic findings and long-term outcomes in 76 sport horses with meniscal injuries (2008-2018)

OBJECTIVE

To report the findings and long-term outcome of 76 sport horses with meniscal injury.

STUDY DESIGN

Retrospective case series.

ANIMALS

Seventy-six horses with 93 meniscal injuries in 85 stifles.

METHODS

Medical records of sport horses diagnosed with meniscal injury during arthroscopy were reviewed. Owner follow up was obtained via telephone interview ≥1.5 years postoperatively. Preoperative and intraoperative findings, and postoperative treatments, were analyzed for potential association with return to athletic performance.

RESULTS

The medial meniscus was involved in 82.8% of cases, with grade 1 injuries diagnosed in 76.3% of menisci. Overall, 85.5% of horses returned to athletic performance, with 40% returning to their previous level. The grade of meniscal injury was associated with long-term outcome (P = .023). The presence of preoperative radiographic abnormalities (P = .259) or additional joint pathology (P = 1.00) was not associated with long-term outcomes. Fifty-nine stifles were treated with an orthobiologic: autologous conditioned serum, platelet-rich plasma, or marrow-derived mesenchymal stem cells. There was no association between the use of any orthobiologic and long-term outcome (P = .394).

CONCLUSION

This is the first report on long-term outcome of sport horses with meniscal injuries following arthroscopic surgery. Overall, the long-term prognosis was fair, with 40% of horses returning to their previous level of use. Severity of the meniscal injury was a prognostic indicator for return to work. The presence of radiographic abnormalities or additional joint pathology, or the use of orthobiologics, was not associated with long-term outcome.

CLINICAL SIGNIFICANCE

These findings can help in prognostication for sport horses with meniscal injuries.

Regenerative Medicine for Equine Musculoskeletal Diseases

Simple Summary

Lameness due to musculoskeletal disease is the most common diagnosis in equine veterinary practice. Many of these orthopaedic disorders are chronic problems, for which no clinically satisfactory treatment exists. Thus, high hopes are pinned on regenerative medicine, which aims to replace or regenerate cells, tissues, or organs to restore or establish normal function. Some regenerative medicine therapies have already made their way into equine clinical practice mainly to treat tendon injures, tendinopathies, cartilage injuries and degenerative joint disorders with promising but diverse results. This review summarises the current knowledge of commonly used regenerative medicine treatments and critically discusses their use.

Abstract

Musculoskeletal injuries and chronic degenerative diseases commonly affect both athletic and sedentary horses and can entail the end of their athletic careers. The ensuing repair processes frequently do not yield fully functional regeneration of the injured tissues but biomechanically inferior scar or replacement tissue, causing high reinjury rates, degenerative disease progression and chronic morbidity. Regenerative medicine is an emerging, rapidly evolving branch of translational medicine that aims to replace or regenerate cells, tissues, or organs to restore or establish normal function. It includes tissue engineering but also cell-based and cell-free stimulation of endogenous self-repair mechanisms. Some regenerative medicine therapies have made their way into equine clinical practice mainly to treat tendon injures, tendinopathies, cartilage injuries and degenerative joint disorders with promising results. However, the qualitative and quantitative spatiotemporal requirements for specific bioactive factors to trigger tissue regeneration in the injury response are still unknown, and consequently, therapeutic approaches and treatment results are diverse. To exploit the full potential of this burgeoning field of medicine, further research will be required and is ongoing. This review summarises the current knowledge of commonly used regenerative medicine treatments in equine patients and critically discusses their use.

Morfometria dos meniscos lateral e medial na articulação femorotibial de equinos

RESUMO As lesões dos meniscos são uma das principais causas de dor e claudicação em equinos. O objetivo do presente estudo foi avaliar a morfometria dos meniscos da articulação femorotibial de equinos. Foram utilizados 48 meniscos de 12 animais de ambos os sexos, com idade entre cinco e 15 anos e com peso entre 400kg e 500kg. A medida da extensão periférica compreendeu desde a parte mais cranial à mais caudal e denominou-se circunferência externa (CE). A margem interna, com o mesmo tratamento, foi chamada de circunferência interna (CI). Os meniscos foram divididos em terços craniais, médios e caudais. A espessura foi obtida nos pontos médios de cada terço. Foi calculada a área dos meniscos em contato com os côndilos femorais. O menisco medial apresentou maior CE com média de 126,38mm, enquanto o menisco lateral apresentou média de 115,32mm. O menisco lateral mostrou maior espessura nos terços médio e caudal, com valores médios de 16,00mm e 19,85mm, respectivamente, contra 13,75mm e 14,99mm dos meniscos mediais. Os resultados deste estudo mostraram relação importante entre os dados morfométricos e os achados clínicos na tentativa de explicar a maior incidência de lesões envolvendo o menisco medial.

Finite Element Modelling Simulated Meniscus Translocation and Deformation during Locomotion of the Equine Stifle

Simple Summary

Meniscal tears are one of the most common soft tissue injuries in the equine stifle joint. To date no optimal treatment strategy to heal meniscal tissue is available. Accordingly, there is a need to improve treatment for meniscal injuries and thus to identify appropriate translational animal models. A possible alternative to animal experimentation is the use of finite element modelling (FEMg). FEMg allows simulation of time dependent changes in tissues resulting from biomechanical strains. We developed a finite element model (FEM) of the equine stifle joint to identify pressure peaks and simulate translocation and deformation of the menisci at different joint angles under loading conditions. The FEM model was tested across a range of motion of approximately 30°. Pressure load was higher overall in the lateral meniscus than in the medial meniscus. Accordingly, the simulation showed higher translocation and deformation throughout the whole range of motion in the lateral compared to the medial meniscus. The results encourage further refinement of this FEM model for studying loading patterns on menisci and articular cartilages as well as the resulting mechanical stress in the subchondral bone. A functional FEM model can not only help identify segments in the femoro–tibial joint which are predisposed to injury, but also provide better understanding of the progression of certain stifle disorders, simulate treatment/surgery effects and to optimize implant/transplant properties in order to most closely resemble natural tissue.

Abstract

We developed a finite element model (FEM) of the equine stifle joint to identify pressure peaks and simulate translocation and deformation of the menisci. A series of sectional magnetic resonance images (1.5 T) of the stifle joint of a 23 year old Shetland pony gelding served as basis for image segmentation. Based on the 3D polygon models of femur, tibia, articular cartilages, menisci, collateral ligaments and the meniscotibial ligaments, an FEM model was generated. Tissue material properties were assigned based on data from human (Open knee(s) project) and bovine femoro-tibial joint available in the literature. The FEM model was tested across a range of motion of approximately 30°. Pressure load was overall higher in the lateral meniscus than in the medial. Accordingly, the simulation showed higher translocation and deformation in the lateral compared to the medial meniscus. The results encourage further refinement of this model for studying loading patterns on menisci and articular cartilages as well as the resulting mechanical stress in the subchondral bone (femur and tibia). A functional FEM model can not only help identify segments in the stifle which are predisposed to injury, but also to better understand the progression of certain stifle disorders, simulate treatment/surgery effects and to optimize implant/transplant properties.

Equine meniscal degeneration is associated with medial femorotibial osteoarthritis

BACKGROUND

There is limited information available concerning normal equine meniscal morphology, its degeneration and role in osteoarthritis (OA).

OBJECTIVES

To characterise normal equine meniscal morphology and lesions and to explore the relationship between equine meniscal degeneration and femorotibial OA.

STUDY DESIGN

Ex vivo cadaveric study.

METHODS

Menisci were harvested from 7 normal joints (n = 14 menisci) and 15 joints with OA (n = 30 menisci). A macroscopic femorotibial OA score (cartilage degeneration and osteophytosis) was employed to measure disease severity in each compartment. The femoral and tibial meniscal surfaces were scored for macroscopic fibrillation and tears (1-4). Histological sections (regions: cranial and caudal horn; body) were also scored for microscopic fibrillation and tears (0-3) and inner border degeneration (0-3).

RESULTS

Partial meniscal tears were present on both femoral and tibial surfaces in all 3 regions and most frequently identified on the femoral surface of the cranial horn of the medial meniscus and body of the lateral meniscus. There was a significantly positive correlation between the global medial meniscal macroscopic scores and osteophyte (r = 0.7, P = 0.002) or cartilage degeneration (r = 0.5, P = 0.03) scores within the medial femorotibial joint. The global medial meniscal macroscopic score was greater (P = 0.004) in the advanced OA joints compared with control joints.

MAIN LIMITATIONS

The menisci were principally from abattoir specimens without a known clinical history because of the challenge in obtaining a large number of specimens with a clinical diagnosis of femorotibial OA.

CONCLUSIONS

This study is the first to describe normal equine meniscal morphology and lesions. Meniscal lesions were identified in all segments and on both articular surfaces. Meniscal degeneration significantly correlated with OA severity in the equine medial femorotibial joint. The relationship between OA and meniscal pathology remains to be elucidated.

Fracture of the medial intercondylar eminence of the tibia in horses treated by arthroscopic fragment removal (21 horses)

BACKGROUND

Fractures of the medial intercondylar eminence of the tibia (MICET) are scarcely reported in horses.

OBJECTIVES

To report the clinical and diagnostic findings, surgical treatment and outcome in a series of horses presented with MICET fracture and treated with arthroscopic fragment removal.

STUDY DESIGN

Multicentre retrospective case series.

METHODS

Case records of horses diagnosed with MICET fractures that had undergone surgical treatment were reviewed. Follow-up information was obtained from re-examination visits and/or owners.

RESULTS

Twenty-one cases were identified at 9 equine hospitals between 2004 and 2016. A history of trauma and acute onset of lameness was reported in 12 horses. All cases underwent fracture removal via arthroscopy of the medial femorotibial joint. The cranial cruciate ligament was intact in 6 horses and damaged in 15 horses (damage was ≤25% [n = 9], 25-50% [n = 4] or ≥50% [n = 2] of the cross-sectional area). The cranial ligament of the medial meniscus was damaged in 11 horses (≤25% [n = 8], 25-50% [n = 3]). The medial meniscus was damaged in 5 horses and articular cartilage damage was identified in 14 horses (mild [n = 8], moderate [n = 6]). Follow-up information (median 14 months; 4 months-6 years) was available for 20 cases; 2 horses were sound but convalescing; 13 horses were sound and returned to their previous or expected use. Of the 4 horses with the most severe changes to the articular soft tissue structures, 2 remained lame and 2 were subjected to euthanasia because of persistent lameness.

MAIN LIMITATIONS

The retrospective, multicentre nature of this study and the limited number of horses are the main limitations.

CONCLUSIONS

Fractures of the MICET are commonly associated with a traumatic event. Prompt diagnosis and early arthroscopic removal of the fracture are recommended.

Nociceptive and sympathetic innervations in the abaxial part of the cranial horn of the equine medial meniscus: an immunohistochemical approach

In athletic horses, diseases leading to lameness are of great importance due to the loss of performance and the resultant economic concerns. Although stifle lesions are frequent in the hindlimb, due to the large size and complexity of the joint, and although meniscal tears have been identified as the most common soft tissue injuries in this joint, little is known about the mechanism that causes the painful sensation and thus the lameness. The aim of our study was to highlight any peripheral fibres involved in meniscal nociception in five macroscopically sound cranial horns of the equine medial meniscus, which has been one of the most common sites reported for equine meniscal injuries. Immunohistochemical stainings were performed using antibodies against Substance P in order to identify nociceptive fibres; against tyrosine hydroxylase for detecting postganglionic sympathetic fibres; and against glial fibrillary acidic proteins in order to identify Schwann cells. Our work highlights for the first time the presence of nociceptive and sympathetic fibres in equine menisci. They were found in the abaxial part of the cranial horn of the equine medial meniscus. This study suggests that when the abaxial part is injured, the meniscus itself could be the source of pain. These findings could provide a better understanding of the clinical presentation of horses with meniscal injury and contribute towards improving therapeutic strategies to alleviate pain in cases of equine meniscal injury.

Mechanoreceptors in the Anterior Horn of the Equine Medial Meniscus: an Immunohistochemical Approach

Lameness due to stifle and especially meniscal lesions is frequent in equine species. In humans, mechanoreceptors involved in proprioceptive function are well studied. Given the high incidence of meniscal injuries in horses, and the lack of information concerning them in equine menisci, our objective was to study these corpuscles in six healthy anterior horns of the equine medial meniscus, which is the most common localisation reported for equine meniscal injuries. Immunohistochemical stainings were performed using antibodies against high molecular weight neurofilaments and glial fibrillary acidic proteins. From a purely fundamental point of view, our work highlights for the first time the presence of Ruffini, Pacini and Golgi corpuscles in equine meniscus. They were found, isolated or in clusters and always located at the vicinity of blood vessels, at the level of the anterior horn of the equine medial meniscus. This morphological approach could serve as a basis for clinical studies, to evaluate the impact of these corpuscles on the poor sportive prognosis in equine meniscal tears.