Clinical use of the locking compression plate (LCP) in horses: a retrospective study of 31 cases (2004-2006)

The influence of a tension band fixation as an adjunct for arthrodesis of the metacarpophalangeal joint in the horse

OBJECTIVES

To determine the influence of a stainless-steel cable (SSC) tension band fixation as an adjunct to a locking compression plate (LCP) for arthrodesis of the equine metacarpophalangeal (MCP) joint.

STUDY DESIGN

Experimental. An ex vivo biomechanical paired equine cadaver limb study.

SAMPLE POPULATION

Five MCP joint pairs were collected from adult Thoroughbred horses, euthanized for reasons unrelated to orthopedic disease.

METHODS

Each pair of MCP joints were randomly implanted with either a dorsally placed 5.5 mm LCP and a palmarly placed 2.0 mm SSC or a dorsally placed 5.5 mm LCP alone. Each construct was tested in cyclic loading followed by single cycle to failure in axial compression. Displacement at a target load of 1 kN over 3600 cycles at 1 Hz was recorded prior to single cycle to failure testing.

RESULTS

In cyclic testing, displacement was not significantly different between the first and last 5% of testing cycles regardless of construct. Maximum displacement of each construct during cyclic testing was <1.1 mm. In single cycle testing, the observed yield point did not reveal any difference between LCP and LCP-SSC (p = .440). The maximum load at failure was significantly higher in LCP-SSC compared to constructs with the LCP alone (p = .046).

CONCLUSION

The addition of the SSC to the LCP did not statistically affect construct displacement during cyclic loading or construct yield load during subsequent single cycle to failure.

CLINICAL SIGNIFICANCE

This study provided much needed information regarding the necessity of a tension band SSC application in the arthrodesis of the MCP/MTP joint in horses.

Incidence of surgical site infection after internal fixation of the first phalangeal bone and the third metacarpal/metatarsal bone fractures in Thoroughbred racehorses

Surgical site infection (SSI) is one of the major complications of equine fracture surgery. The purpose of this study was to investigate the incidence of and risk factors for SSI after internal fixation of the first phalangeal bone (P1) and the third metacarpal/metatarsal bone (MC3/MT3) fractures in Thoroughbred racehorses. Between 2011 and 2020, 451 cases underwent surgery with screws or a locking compression plate (LCP) for sagittal fractures of P1 or condylar fractures of MC3/MT3. Overall, 2.9% (13/451) of the cases developed an SSI. The incidence was significantly higher in plate fixation (21.4%) than in screw fixation (2.3%). There was no significant association with other variables, such as sex, age, number of screws, experience of surgeon, or prophylactic antimicrobials. The median duration of hospitalization for screw fixation was 14 days without an SSI and 20 days with an SSI, and those for plate fixation were 26 and 25-88 days, respectively, indicating that the development of SSI prolongs the duration of hospitalization. On the other hand, there were no significant differences in discharge and race resumption rates between cases with and without an SSI. These data indicate that the incidence of SSI in this study was low and that it was higher following plate fixation than screw fixation.

Proximal Interphalangeal Arthrodesis in Horses: A Meta-Analysis of Retrospective Studies

The aim of this study was to determine the clinical outcomes reported in retrospective studies of proximal interphalangeal arthrodesis (PIA) in horses through a meta-analysis of retrospective studies. CAB Abstracts, PubMed, ScienceDirect, Web of Science, and Scopus were searched. The primary outcomes included survival and surgical site infection (SSI) rates, return to activities, and time of hospital stay and casting. Subgroups were formed for fractures and other conditions. Meta-analyses were performed with fixed and random effects models to estimate proportions, mean values, and effect size by odds ratio (OR) with 95% confidence intervals (CI). Twenty-one full articles were included, totaling 458 horses. The survival rate was 90% (95% CI [86%-93%]), return to activities was 65% (95% CI [61%-70%]), and SSI was 12% (95% CI [8%-16%]). The mean hospitalization was 25 days (95% CI [18-35 days]) and time of casting was 29 days (95% CI [21-42 days]). The OR of survival (P = .769), return to activities (P = .576), and SSI (P = .467) were similar between cases of fractures and other conditions. PIA is an efficient and safe method to treat injuries in the pastern region, with a high survival rate and low SSI. However, the rate of return to soundness for intended use was modest, being potentially lower for fracture cases. Thus, investigations of more efficient interventions are needed to improve this outcome.

Use of Locking Compression Plate and Locking Compression T-Plate for Surgical Arthrodesis of the Carpometacarpal and Distal Tarsal Joints in 13 Horses

OBJECTIVE

 The aim of this study was to describe the use of the locking compression plate (LCP) and locking compression T-plate (LCTP) in cases of carpometacarpal and distal tarsal arthrodesis for the treatment of osteoarthritis and small carpal or tarsal bone fractures, and to document clinical outcomes.

STUDY DESIGN

 Case records of horses treated with carpometacarpal or distal tarsal arthrodesis via internal fixation using an LCP or LCTP between 2013 and 2021 were reviewed. All cases were evaluated retrospectively. Follow-up information was gained via phone conversation with owners and referring veterinarians.

RESULTS

 Data were collected for 13 horses that fulfilled the study criteria. A total of eight horses underwent distal tarsal arthrodesis, and five underwent carpometacarpal arthrodesis. Twelve of thirteen horses went back to some level of athletic performance. Eight of 13 returned to the same level, while 4 of 13 returned to a lower level. Minor postoperative complications were recorded in 3 of 13 cases, with all horses suffering manageable short-term complications returning to the same level of work. Two horses suffered a major complication, with one resulting in euthanasia.

CONCLUSION

 Carpometacarpal and distal tarsal arthrodesis performed using the LCP and LCTP allowed all surviving horses in the study to obtain immediate postoperative comfort and eventual return to use.

Evaluation of factors associated with surgical site infection in equine proximal interphalangeal joint arthrodesis: 54 cases (2010–2019)

Background

The frequency of surgical site infection (SSI) following orthopaedic implant placement in horses has been reported but not compared with respect to specific antibiotic protocols administered.

Objectives

To determine factors associated with SSI in horses undergoing proximal interphalangeal joint (PIPJ) arthrodesis including perioperative antibiotic protocols.

Methods

Records were evaluated (2010–2019), and horses undergoing PIPJ arthrodesis were identified. Patient signalment, supervising surgeon, reason for surgery, limb, implants placed, anaesthetic time, duration casting/coaptation postoperatively, antibiotic regimen and incidence/onset SSI were recorded. Bayesian and frequentist logistic regressions were used to estimate the contribution of covariates to infection occurrence.

Results

Fifty‐four PIPJ arthrodeses were performed. SSI occurred in 2/54 (3.7%) on day 15,30. Arthrodesis was performed most commonly for osteoarthritis (33/54, 61.1%), fracture (11/54, 20.4%), and subluxation (5/54, 9.3%). Perioperative systemic antibiotics were administered 1–3 days (15/54, 27.8%) or > 3 days (39/54, 72.2%). Antibiotic protocols included cefazolin/gentamicin (20/54, 37%), cefazolin/gentamicin/doxycycline (14/54, 25.9%) and potassium penicillin/gentamicin (10/54, 18.5%). Regional limb perfusion was performed preoperatively 31/54 (57.4%) and postoperatively 7/54 (13%). Survival to dismissal was 98.1% (53/54 horses) with one horse euthanized due to support limb laminitis. No association was identified between antibiotic selection or duration (1–3 vs. > 3 days), pre‐operative regional antibiotic perfusion, intraoperative antibiotic lavage or anaesthetic time (< or > 3 h) and SSI; however, modelling was complicated by quasi‐complete or complete separation of the data. Bayesian analysis (but not frequentist analysis) indicated an association between post‐operative regional antibiotic perfusion and SSI. Limitations include the retrospective nature of data collection and the low rate of infection overall.

Conclusions

The prevalence of SSI in this population was lower than that in previous reports of equine orthopaedic internal fixation. There was no difference in SSI rate in cases administered systemic antibiotics for 1–3 days or >3 days, or for those horses that did or did not receive preoperative regional antibiotic perfusion.

Cervical Epidural Spinal Analgesia for Acute Management of Severe Unilateral Forelimb Lameness: Case Report

A 20-year-old Quarter Horse gelding was presented with severe right forelimb lameness (5/5 AAEP Lameness Scale) due to a tear of the superficial digital flexor muscle which was diagnosed via palpation of swelling and ultrasonography revealing major muscle fiber disruption and hematoma formation. When traditional systemic therapy (non-Steroidal anti-inflammatories) did not restore clinically acceptable comfort and the risk of supporting limb laminitis became a reasonable concern, a cervical epidural catheter was placed between the first and second cervical vertebrae in the standing, sedated patient using ultrasound guidance. The gelding was treated with epidural morphine (0.1 mg/kg every 24 h then decreased to 0.05 mg/kg every 12 h) and was pain-scored serially following treatment. Spinal analgesia was provided for 3 days. Pain scores significantly decreased following each treatment with morphine, and the gelding was successfully managed through the acutely painful period without any adverse effects associated with the C1-C2 epidural catheter placement technique, the epidural morphine, or contralateral limb laminitis. At the 2-month follow-up, the gelding was walking sound with no complications seen at the catheter insertion site. In this case, spinal analgesia using epidural morphine administered via a cervical epidural catheter was an effective and technically achievable option for pain management associated with severe forelimb muscle injury in a horse.

Supporting Limb Laminitis

Supporting limb laminitis (SLL) is a relatively frequent complication of painful limb conditions that alter normal weight-bearing patterns in horses. New evidence suggests that a lack of limb load cycling activity (normally associated with ambulation) interferes with normal perfusion of the lamellae in these cases, resulting in ischemia and dysfunction/death of cells critical to the mechanical function of the lamellae. Excessive weight-bearing load drives the progression to overt acute laminitis in the supporting limb. Monitoring and enhancement of limb load cycling activity are key strategies that may lead to successful prevention of SLL by ensuring adequate lamellar perfusion.

Locking compression plate fixation of critical-sized bone defects in sheep. Development of a model for veterinary bone tissue engineering

PURPOSE

To develop a segmental tibial bone defect model for tissue engineering studies in veterinary orthopedics using single locking compression plate (LCP) fixation and cast immobilization.

METHODS

A 3-cm bone defect was created in the right tibia of 18 adult Suffolk sheep. A 10-hole, 4.5-mm LCP was applied to the dorsomedial aspect of the bone. Four locking screws were inserted into the proximal and three into the distal bone fragment. Operated limbs were immobilized with casts. Animals were submitted to stall rest, but were allowed to bear weight on the operated limb. During the recovery period, animals were checked daily for physiological parameters, behavior and lameness. Follow-up radiographs were taken monthly.

RESULTS

Surgical procedures and postoperative recovery were uneventful. Animals adapted quickly to casts and were able to bear weight on the operated limb with no signs of discomfort or distress. No clinical or radiographic complications were detected over a 90-day follow-up period.

CONCLUSIONS

Surgical creation of tibial segmental bone defects followed by fixation with single LCP and cast immobilization was deemed a feasible and appropriate model for veterinary orthopedic research in tissue engineering.

Proximal interphalangeal locking compression plate for pastern arthrodesis in horses

BACKGROUND

Outcomes following proximal interphalangeal joint (PIPJ) arthrodesis by a variety of surgical methods are available. Reports detailing clinical outcomes following PIPJ arthrodesis utilising the proximal interphalangeal joint locking compression plate (PIP-LCP) and abaxial transarticular lag screws technique are limited.

OBJECTIVES

To report survival, radiographic and clinical outcomes following PIPJ arthrodesis with PIP-LCP and abaxial transarticular lag screw fixation.

STUDY DESIGN

Retrospective case series.

METHODS

Medical records of all horses undergoing pastern arthrodesis from 2009 to 2018 were reviewed. Arthrodeses performed using a 3-hole, 4.5 mm narrow LCP, specifically designed for the proximal interphalangeal joint, were included. Patient details, presentation, radiographic findings, intraoperative and post-operative data, and complications were documented. Short- and long-term follow-up was available for 23 horses.

RESULTS

Thirty PIPJ arthrodeses were performed in 29 horses meeting the criteria for inclusion. Twenty-eight horses (97%, 95% CI 83-100) survived to discharge. Twenty-three horses (79%, 95% CI 60%-92%) had successful outcomes including 12 of the 15 forelimb cases and 11 of the 13 hindlimb cases with available follow-up. Fifteen of 19 performance horses returned to athletic activity. Soundness in performance horses was recognised at less than 3 months in one case, 3 to 6 months in six cases, 6 to 12 months in five cases, and greater than 12 months in six cases. Complications included three implant infections, support limb laminitis (two horses), and fragmentation of the extensor process of the distal phalanx (one horse).

MAIN LIMITATIONS

A retrospectively reviewed, small study population with a variety of breeds and disciplines.

CONCLUSIONS

The PIP-LCP construct provides a very good prognosis for performance and an excellent prognosis for pasture soundness.

Toll-like receptor activation of equine mesenchymal stromal cells to enhance antibacterial activity and immunomodulatory cytokine secretion

OBJECTIVE

To evaluate effects of Toll-like and nucleotide-binding oligomerization domain (NOD)-like receptor (TLR, NLR) ligand stimulation of equine mesenchymal stromal cells (MSCs) on antibacterial and immunomodulatory properties in vitro.

STUDY DESIGN

Controlled laboratory study.

SAMPLE POPULATION

Equine bone-marrow-derived MSCs (three horses).

METHODS

MSCs were stimulated with TLR (polyinosinic:polycytidylic acid [pIC] and lipopolysaccharide [LPS]) and NLR agonists (γ-d-Glu-mDAP [IE-DAP]) for 2 h, and plated at 1 × 10⁵ cells/well 24 h. MSC-conditioned media (MSC-CM) were collected and assessed for antimicrobial peptide cathelicidin/LL-37 production, bactericidal action against multidrug-resistant planktonic and biofilm Staphylococcus aureus and neutrophil phagocytosis. Bacterial growth was measured by plating bacteria and counting viable colonies, reading culture absorbance, and live-dead staining with confocal microscopy imaging. Following initial comparison of activating stimuli, TLR3-agonist pIC protocols (cell density during activation and plating, culture time, %serum) were further optimized for bactericidal activity and secretion of interleukin-8 (IL-8), monocyte-chemoattractant-protein (MCP-1), and cathelicidin/LL37.

RESULTS

MSCs stimulation with pIC (p = .004) and IE-DAP (p = .03) promoted increased bactericidal activity, evidenced by reduced viable planktonic colony counts. PIC stimulation (2 × 10⁶ cells/ml, 2 h, 10 μg/ml) further suppressed biofilm formation (p = .001), enhanced neutrophil bacterial phagocytosis (p = .009), increased MCP-1 secretion (p < .0001), and enhanced cathelicidin/LL-37 production, which was apparent when serum concentration in media was reduced to 1% (p = .01) and 2.5% (p = .05).

CONCLUSION

TLR-3 pIC MSCs activation was most effective to enhance antibacterial and cytokine responses, which were affected by serum reduction.

CLINICAL SIGNIFICANCE

In vitro TLR-3 activation of equine MSCs tested here may be a strategy to improve antibacterial properties of MSCs to treat antibiotic-resistant infections.

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.

The effect of regional hypothermia on mechanical nociceptive thresholds in the equine distal forelimb

Regional hypothermia has shown promise as analgesic in horses when used to manage painful conditions of the distal limb such as laminitis. In this prospective study, the analgesic effects of regional hypothermia were assessed using mechanical nociceptive thresholds during distal limb cooling. The study population consisted of eight healthy adult Standardbred horses, selected from a teaching herd. A distal forelimb of each horse was cooled using water immersion at the following sequential target water temperatures: 34 °C, 20 °C, 10 °C, 5 °C, 1 °C, 5 °C, 10 °C, 20 °C. Limb surface temperature was measured after 30 min at each target water temperature and the mechanical force required to elicit a response (mechanical nociceptive threshold) was determined using a pneumatic actuator. Both forelimbs of each horse were tested one week apart. At skin surface temperatures above 7 °C, there was little association between skin surface temperature and the mechanical force required to elicit a response. As the skin surface temperature decreased below 7 °C, there was a rapid increase in the force required to elicit a response (P = 0.036). Skin surface temperatures of <7 °C required water temperatures below 2 °C. The results of this study suggest that hypothermia has potential to provide distal limb analgesia in horses at skin surface temperatures below 7 °C. Further evaluation of the technique is warranted.

Lamellar perfusion and energy metabolism in a preferential weight bearing model

BACKGROUND

Supporting limb laminitis (SLL) is suspected to be caused by lamellar ischaemia as a consequence of increased mechanical load.

OBJECTIVES

Examine the effects of prolonged preferential weight bearing (PWB) on lamellar perfusion and metabolism.

STUDY DESIGN

In vivo experiment.

METHODS

Microdialysis probes were inserted in the lamellar and sublamellar dermis of one forelimb in 13 Standardbred horses. In six horses, a platform shoe (contralateral forelimb) was used to induce increased load on the microdialysis-instrumented forelimb (PWB). The remaining seven horses were controls (CON). All horses were housed in stocks with limb weight distribution logged continuously for 92 hours. Microdialysate was collected and analysed every 4 hours for glucose, lactate, pyruvate, and lactate to pyruvate ratio (L:P). Microdialysis urea clearance was used to estimate lamellar perfusion. Data were analysed using a mixed-effects linear regression model.

RESULTS

Median [IQR] load on the microdialysis-instrumented limb was equivalent to 38.7% bwt. [37.3-40.3] in PWB and 27.3% bwt. [26.6-28] in CON. Limb offloading frequency increased in CON (P < .001) but not PWB (P = .2). Lamellar microdialysate glucose decreased in PWB (P < .001) and CON (P = .004), however, the rate of decrease was higher in PWB (P = .007). Lamellar L:P increased in PWB (P < .001) and peaked at 196 [79-656], whereas L:P did not change over time in CON (P = .6) and peaked at 42 [41-49]. Lamellar urea clearance decreased in PWB (P < .001) but not in CON (P = .3). Sublamellar L:P and urea clearance did not change over time in either group (P > .05).

MAIN LIMITATIONS

The PWB model may not be representative of naturally occurring SLL.

CONCLUSIONS

Evidence of lamellar ischaemia (increased L:P and decreased urea clearance) was detected exclusively in the lamellar dermis of PWB feet subjected to persistently increased load. Lamellar ischaemia is a consequence of increased mechanical load and likely contributes to the development of SLL.

Biomechanical comparison of locking compression plate fixation and a novel pedicle screw external fixation to repair equine mandibular fractures

OBJECTIVE

To determine the biomechanical properties of pedicle screw external fixation (PDW) for equine mandibular fracture repair and compare PDW to locking compression plates (LCP).

STUDY DESIGN

Cadaveric study.

SAMPLE POPULATION

Sixteen adult equine mandibles.

METHODS

Four mandibles were kept intact, while 12 were osteotomized and stabilized with the LCP or PDW construct (6 mandibles/group). Failure, stiffness, and yield were calculated from quasi-static ramp to failure and compared with previous analysis of mandibular fracture constructs. Tooth root involvement and method of failure were determined from radiographs and videos.

RESULTS

Locking compression plate constructs achieved greater stiffness and load at failure (4656 ± 577 N-m/radian, 558 ± 27 N-m P < .05) compared with PDW constructs (2626 ± 127 N-m/radian, 315 ± 48 N-m). Yield did not differ between types of fixation (369 ± 57 N-m, 193 ± 35 N-m, P = .145). Tooth involvement was noted in two LCP constructs with failure via bone fracture. Pedicle screw external fixation constructs failed via wire unraveling and screw bending.

CONCLUSION

Locking compression plate fixation increased stiffness and failure of constructs but did not influence yield. It also increased the risk to tooth root involvement relative to fixation with PDW. Compared with another study, PDW offered stiffness and failure similar to an intraoral splint with interdental wires, external fixator (EF), and external fixator with wires (EFW) and yield similar to an EF, an EFW, and a dynamic compression plate.

CLINICAL RELEVANCE

Pedicle screw external fixation offers biomechanical stability comparable to other relevant mandibular fixation techniques and reduces the risk of tooth root damage compared with LCP fixation.

Use of a locking compression plate for equine proximal interphalangeal joint arthrodesis: 29 cases (2008-2014)

OBJECTIVE To describe clinical use of a locking compression plate (LCP) for proximal interphalangeal joint (PIPJ) arthrodesis in horses and compare outcomes for horses that underwent the procedure as treatment for fracture of the middle phalanx (P2) versus other causes. DESIGN Retrospective case series. ANIMALS 29 client-owned horses. PROCEDURES Medical records of 2 veterinary teaching hospitals from 2008 through 2014 were reviewed to identify horses that underwent PIPJ arthrodesis of 1 limb. Signalment, surgical, and outcome-related variables were recorded. Owners were contacted from 1 to 6 years after surgery to determine rehabilitation time, current use of the horse, and overall owner satisfaction with the procedure. Success was determined on the basis of owner satisfaction and outcome for intended use. Variables of interest were compared statistically between horses that underwent surgery for P2 fracture versus other reasons. RESULTS 14 horses underwent surgery for treatment of P2 fracture, and 15 had surgery because of osteoarthritis, subluxation, or osteochondrosis. Median convalescent time after surgery (with no riding or unrestricted exercise) was 7 months. Four horses were euthanized; of 23 known alive at follow-up, 22 were not lame, and 18 had returned to their intended use (8 and 10 at higher and lower owner-reported levels of work, respectively). Horses undergoing arthrodesis for reasons other than fracture were significantly more likely to return to their previous level of work. Twenty-two of 24 owners contacted indicated satisfaction with the procedure. CONCLUSIONS AND CLINICAL RELEVANCE Surgical arthrodesis of the PIPJ was successful in most horses of the study population. Various nuances of the system for fracture repair need to be understood prior to its use.

Arthrodesis of the metacarpophalangeal and metatarsophalangeal joints to treat osteoarthritis in 17 horses

OBJECTIVE

To describe arthrodesis of the metacarpophalangeal (MCP) or metatarsophalangeal (MTP) joint with a locking compression plate (LCP) and a metallic tension band and report the outcome of horses treated for osteoarthritis (OA) with this technique.

STUDY DESIGN

Retrospective case series.

ANIMALS

Seventeen horses with OA of the MCP or MTP joint treated with arthrodesis.

METHODS

Medical records (2004-2017) of horses treated for OA with arthrodesis of the MCP or MTP joint with an LCP and metallic tension band were reviewed. Preoperative variables included age, sex, breed, affected limb, and lameness grade. Surgical variables included implants used, surgery time, postoperative angle of joint, intraoperative complications, and anesthetic recovery method. Outcome was obtained from medical records and phone interviews.

RESULTS

Lameness was scored as 4 out of 5 (range, 2-4) in 13 of 17 horses. All horses survived to discharge and were alive >6 months postoperatively, without any report of long-term complications. All horses were allowed unrestricted turnout, and 1 horse was lightly ridden. No postoperative infections or implant failures were reported. The only complications consisted of cast sores (n = 4).

CONCLUSION

Arthrodesis of the MCP/MTP joint was associated with acceptable morbidity and good long-term outcomes in these 17 horses with OA refractory to medical management.

CLINICAL SIGNIFICANCE

The morbidity and prognosis after fetlock arthrodesis for OA seem more favorable than reported in horses treated with traumatic disruption of the suspensory apparatus.

Are There Shared Mechanisms in the Pathophysiology of Different Clinical Forms of Laminitis and What Are the Implications for Prevention and Treatment?

Laminitis is a consequence of primary disease processes elsewhere in the body. The key pathophysiologic events are insulin dysregulation in endocrinopathic laminitis, ischemia in supporting limb laminitis, and inflammation in sepsis-related laminitis. These apparently disparate mechanisms converge to cause lamellar attachment failure through epithelial cell adhesion loss and stretch, possibly mediated by common growth factor signaling pathways. Tissue damage through mechanical distraction, inflammation, pain, and a proliferative epithelial healing response are features of acute laminitis regardless of the cause. Preventive and treatment strategies based on knowledge of these unique and common mechanistic events are likely to improve clinical outcomes.

Surgical site infection associated with equine orthopedic internal fixation: 155 cases (2008-2016)

OBJECTIVE

To determine the prevalence of surgical site infection (SSI) after internal fixation and to identify risk factors for SSI and nonsurvival.

STUDY DESIGN

Retrospective study.

ANIMALS

One hundred fifty-five horses with long bone fractures or arthrodesis treated by internal fixation at 1 hospital between 2008-2016.

METHODS

Signalment, diagnosis, surgical repair, surgeon, surgical time, antimicrobial use, SSI onset, bacterial identification, and adjunct treatments were recorded. Perioperative variables were analyzed to identify risk factors associated with outcomes.

RESULTS

Surgical-site infection was reported in 22 of 155 (14.2%) horses, which is lower than what has been previously reported (P = .003). Horses with fetlock arthrodesis or ulnar fracture were more likely to develop SSI. Local prophylactic antimicrobial therapy was associated with an increased risk of SSI. Horses with SSI were 12 times (P < .0001) less likely to survive to discharge than horses without SSI. Horses with a fetlock or carpal arthrodesis or those with radial/humeral/femoral fractures were less likely to survive. No association was identified between open fractures, open reduction and internal fixation, or surgical times and SSI.

CONCLUSION

The prevalence of SSI in this population was lower than what has been previously reported. Horses with fetlock or carpal arthrodesis or radial/humeral/femoral fractures were at increased risk for SSI and/or nonsurvival to discharge. A protective role of local antimicrobial therapy for SSI could not be established.

CLINICAL RELEVANCE

The impact of SSI on outcomes of cases of equine internal fixation remains substantial. Identification of cases at higher risk of SSI should influence surgical technique, postoperative management, and early intervention when SSI is suspected. Additional investigation is warranted regarding local antimicrobial therapy.

Influence of plate type and placement on the immobilization of bilateral equine mandibular osteotomies: Ex vivo study

OBJECTIVE

To determine the influence of plate fixation (locking or dynamic compression) and the site of application (ventral [V] or ventrolateral [VL]) on the resistance to bending of transverse mandibular fractures.

STUDY DESIGN

Ex vivo, simple randomized study.

SAMPLE POPULATION

Mandibles harvested from adult equine cadavers (n = 18).

METHODS

Bilateral osteotomies were created 1 cm caudal to the mental foramen and perpendicular to the long axis of each mandible. Mandibles were fixed with 1 of 3 methods: (1) VL dynamic compression plate (DCP), (2) V-DCP, or (3) VL locking compression plating (LCP). Constructs were mounted on a custom testing jig and tested for resistance in bending by applying force to the rostral aspect of the mandible. Stiffness and change of distance of the dorsal osteotomy at 200 N were compared among constructs.

RESULTS

VL-LCP constructs were 5.25 and 2.42 times stiffer than V and VL constructs, respectively (P<.001). Change in the width of the osteotomy gap at 200 N of load was reduced 6.04 times when osteotomies were stabilized with VL compared to V (P<.001); no difference was detected between the VL and VL-LCP constructs (P=.836).

CONCLUSION

Ventrolateral LCP fixation of equine transverse mandibular osteotomies provided greater resistance to bending compared with V and VL constructs.

CLINICAL SIGNIFICANCE

These results provide evidence to recommend fixation of transverse interdental mandibular fractures with VL-LCP rather than with DCP in horses.

Surgical repair of a depressed, comminuted fracture of the zygomatic process of the frontal bone using a locking compression plate in a Thoroughbred colt foal

This case report demonstrates the use of a 10-hole 2.7-mm locking compression plate (LCP) to repair a depressed, comminuted fracture of the zygomatic process of the frontal bone, in a foal. LCP fixation resulted in excellent cosmesis. The use of LCP fixation in this region has not been previously described.

Use of locking compression plates in ulnar fractures of 18 horses

OBJECTIVES

To describe the outcome, clinical findings, and complications associated with the use of the locking compression plate (LCP) for various types of ulnar fractures in horses.

STUDY DESIGN

Retrospective case series.

SAMPLE POPULATION

Client owned horses (n = 18).

METHODS

Medical records, radiographs, and follow-up for horses having an ulnar fracture repaired using at least 1 LCP were reviewed. Fifteen of 18 horses had fractures of the ulna only, and 3 horses had fractures of the ulna and proximal radius.

RESULTS

All 18 horses were discharged from the hospital. Complications occurred in 5 horses; incisional infection (n = 4, 22%), implant-associated infection (n = 2, 11%), and colic (n = 1, 6%). Follow-up was available for all horses at a range of 13-120 months and 15 horses (83%) were sound for their intended purpose and 3 horses (17%) were euthanatized. One horse was euthanatized for complications associated with original injury and surgery.

CONCLUSIONS

The LCP is a viable method of internal fixation for various types of ulnar fractures, with most horses in this series returning to soundness.

In vitro biomechanical comparison of a 5-hole 4.5 mm locking compression plate and 5-hole 4.5 mm dynamic compression plate for equine proximal interphalangeal joint arthrodesis

OBJECTIVE

To compare the biomechanical properties of a 5-hole 4.5 mm narrow locking compression plate (LCP) and 5-hole 4.5 mm narrow dynamic compression plate (DCP) for equine proximal interphalangeal (PIP) joint arthrodesis.

STUDY DESIGN

Experimental mechanical study.

ANIMALS

Cadaveric adult equine forelimbs (n = 6 pair).

METHODS

For each forelimb pair, 1 PIP joint was stabilized with LCP and the contralateral PIP joint with DCP. The 6 construct pairs were tested using a single-cycle, 3-point dorsopalmar bending system. PIP joints were evaluated with pre- and post-test radiography.

RESULTS

The LCP technique had significantly greater yield load, failure load, and stiffness under single-cycle, 3-point dorsopalmar bending to failure than the DCP technique. There was no significant difference between the 2 constructs for displacement at yield and failure point.

CONCLUSIONS

Biomechanically, the LCP technique provided significantly greater stability than the DCP technique under the test condition.

Equine ulnar fracture repair with locking compression plates can be associated with inadvertent penetration of the lateral cortex of the radius

OBJECTIVE

To evaluate if the use of locking head screws (LHS) in the distal holes of a locking compression plate (LCP) applied to the caudal aspect of the ulna to treat equine ulnar fractures is associated with a risk of injury to the lateral cortex of the radius.

STUDY DESIGN

Controlled laboratory study.

SAMPLE POPULATION

Cadaveric equine forelimbs (n = 8 pair).

METHODS

After transverse ulnar osteotomy, osteosynthesis was performed with a narrow 10-13 hole 4.5/5.0 LCP applied to the caudal aspect of each ulna. The distal 3 holes were filled with 4.5 mm cortex screws (CS) in 1 limb (group 1) and with 5.0 mm LHS contralaterally (group 2). CS were inserted in an angle deemed appropriate by the surgeon and LHS were inserted perpendicular to the plate. Implant position and injury to the lateral cortex of the radius were assessed by radiography, CT, and limb dissection.

RESULTS

In group 1, injury of the lateral radius cortex did not occur. In group 2, 4 limbs and 6/24 LHS were associated with injury of the lateral radius cortex by penetration of a LHS. This difference was statistically significant. CS were inserted with a mean angle of 17.6° from the sagittal plane in a caudolateral-craniomedial direction.

CONCLUSIONS

Use of LHS in the distal part of a LCP applied to the caudal aspect of the ulna is associated with a risk of inadvertent injury to the lateral cortex of the radius.

Surgical treatment of distal tarsal joint luxations in three horses

The clinical signs, radiographic findings, surgical treatment, and outcome of three horses with luxation of the distal tarsal joints are reported. Two patients showed luxations of the tarsometatarsal joint whereas luxation of the proximal intertarsal joint was found in one case. Open reduction, followed by internal fixation was performed in two horses and closed reduction with a transfixation pin cast was performed in the third. The treatment in all three cases resulted in a satisfactory clinical outcome.

Incidence of support limb laminitis in horses treated with half limb, full limb or transfixation pin casts: a retrospective study of 113 horses (2000-2009)

REASONS FOR PERFORMING STUDY

To determine the incidence of support limb laminitis among horses treated with half limb, full limb or transfixation pin casts and determine potential risk factors.

METHODS

Medical records of 113 horses treated with half limb, full limb or transfixation pin casts at an equine referral hospital from 2000 to 2009 were reviewed. Associations between potential risk factors and development of support limb laminitis were evaluated by bivariable and multivariable logistic regression analyses.

RESULTS

Of the 113 horses that received casts, 14 (12%) developed confirmed support limb laminitis. The bodyweight of the horse and duration of casting in weeks were significantly associated with support limb laminitis. Horses requiring full limb casts or transfixation pin casts were more likely to develop this complication than horses requiring half limb casts. There were no significant associations between developing support limb laminitis and weightbearing capacity on presentation to the hospital, the limb affected (fore- or hind), whether there was a fracture present or breed of horse.

CONCLUSIONS

Support limb laminitis is a relatively common complication among horses treated with half limb, full limb and transfixation pin casts. Greater durations of casting and higher bodyweights increase the likelihood of developing this complication.

POTENTIAL RELEVANCE

Support limb laminitis may occur secondary to any painful unilateral lameness and is not necessarily more likely to develop in horses with severe orthopaedic conditions such as fractures. However, heavier horses, those requiring casts for longer periods of time and those that require a full limb or transfixation pin cast as opposed to a half limb cast should be considered to have an increased risk for developing support limb laminitis post operatively.