Condylar fracture location is correlated to exercise history in Thoroughbred racehorses.

BACKGROUND: Condylar fractures are a major cause of morbidity and mortality in Thoroughbred racehorses. Condylar fractures have a variety of fracture configurations that suggest there may be differences in aetiopathogenesis. OBJECTIVE: To determine if exercise history differs with condylar fracture location in a population of Thoroughbred racehorses. STUDY DESIGN: Retrospective analysis of clinical and exercise data. METHODS: Exercise history of Thoroughbred racehorses that had condylar fracture repair between 1 January 2018 and 28 February 2021 was compared between racehorses that had fractures located radiographically either within the parasagittal groove (PSG) or abaxial to the PSG (non-PSG). Age, sex, and last event (race, timed work) matched control groups were compared between the PSG and non-PSG groups. Additionally, exercise history variables of both groups were each compared with a group-specific control population, each consisting of three control racehorses of equivalent age and sex matched to each affected racehorse by last event (race or official timed work) before fracture. RESULTS: Eighty-two horses with 84 fractures (45 PSG, 39 non-PSG) met inclusion criteria. Age was not different between groups (PSG: 3.4 ± 1.3 years [mean ± SD], non-PSG: 3.7 ± 1.3, p = 0.3). Number of races (PSG: 5.3 ± 7.1, non-PSG: 11.4 ± 8.9, p < 0.001), total race furlongs (PSG: 38.2 ± 54.7, non-PSG: 79.2 ± 64, p = 0.003), and number of active days (PSG: 304 ± 224, non-PSG: 488 ± 314, p = 0.003) before fracture were greater; while mean number of layups was fewer (PSG: 1.0 ± 1.2, non-PSG: 0.5 ± 0.7, p = 0.02) in horses with non-PSG fracture. Horses with non-PSG fracture had more differences compared with their respective control group than horses with PSG fractures. Outcomes following fracture repair were not different between groups. MAIN LIMITATIONS: Retrospective study, one regional racehorse population, two-dimensional imaging and potential inherent bias for fracture localisation, low statistical power for return to performance analysis. CONCLUSIONS: Thoroughbred racehorses with non-PSG condylar fractures have a more extensive exercise history than horses with PSG condylar fractures, suggesting differences in fracture aetiopathogenesis.

CONTEXTO: Fraturas condilares são uma das principais causas de morbidade e mortalidade em cavalos de corrida puro­sangue inglês. As fraturas condilares apresentam uma variedade de configurações que sugerem que pode haver diferenças em suas etiopatogenia. OBJETIVO: Determinar se o histórico de exercícios difere com a localização da fratura condilar em uma população de cavalos de corrida puro­sangue inglês. DELINEAMENTO DO ESTUDO: Análise retrospectiva de dados clínicos e de exercício. MÉTODOS: O histórico de exercícios de cavalos de corrida puro­sangue inglês que tiveram reparo de fratura condilar entre 1 de janeiro de 2018 e 28 de fevereiro de 2021 foi comparado entre cavalos de corrida que tiveram fratura localizada radiograficamente dentro da ranhura parasagital (RPS) ou abaxial à RPS (não RPS). Os grupos foram pareados de acordo com a idade, sexo e último evento (corrida ou trabalho cronometrado) para comparação de RPS e não RPS. Além disso, as variáveis de histórico de exercícios de ambos os grupos foram comparadas a uma população de controle específica, cada uma consistindo em três cavalos de corrida de controle com idade e sexo equivalentes combinados com cada cavalo de corrida afetado pelo último evento (corrida ou trabalho cronometrado oficial) antes da fratura. RESULTADOS: Oitenta e dois cavalos com 84 fraturas (45 RPS, 39 não RPS) atenderam aos critérios de inclusão. A idade não foi diferente entre os grupos (RPS: 3,4 ± 1,3 anos (média ± DP), não RPS: 3,7 ± 1,3, p=0,3). O número de corridas (RPS: 5,3 ± 7,1, não RPS: 11,4 ± 8,9, p<0,001), furlongs totais de corrida (RPS: 38,2 ± 54,7, não RPS: 79,2 ± 64, p=0,003) e número de dias ativos (RPS: 304 ± 224, não RPS: 488 ± 314, p=0,003) antes da fratura foram maiores; enquanto o número médio de repousos foi menor (RPS: 1,0 ± 1,2, não RPS: 0,5 ± 0,7, p=0,02) em cavalos com fratura não RPS. Cavalos com fratura não RPS tiveram mais diferenças em comparação com seu grupo controle respectivo do que cavalos com fraturas RPS. Os resultados após o reparo da fratura não foram diferentes entre os grupos. PRINCIPAIS LIMITAÇÕES: Estudo retrospectivo, uma população regional de cavalos de corrida, imagens bidimensionais e viés inerente potencial para localização de fraturas, baixo poder estatístico para análise de retorno ao desempenho. CONCLUSÕES: Cavalos de corrida puro­sangue inglês com fraturas condilares não RPS têm um histórico de exercícios mais extenso do que cavalos com fraturas condilares RPS, sugerindo diferenças na etiopatogenia das fraturas.

Osteoblastic differentiation of human and equine adult bone marrow-derived mesenchymal stem cells when BMP-2 or BMP-7 homodimer genetic modification is compared to BMP-2/7 heterodimer genetic modification in the presence and absence of dexamethasone.

Bone marrow-derived mesenchymal stem cells (BMDMSCs) have been targeted for use in enhancement of bone healing; and their osteogenic potential may be further augmented by genes encoding bone morphogenetic proteins (BMP's). The purpose of this study was to compare the effect of genetic modification of human and equine BMDMSCs with BMP-2 or -7 or BMP-2 and -7 on their osteoblastogenic differentiation in the presence or absence of dexamethasone. The BMDMSCs were harvested from the iliac crest of three human donors and tuber coxae of three equine donors. Monolayer cells were genetically modified using adenovirus vectors encoding BMP-2, -7 or both and cultured in the presence or absence of dexamethasone. Expression of BMPs was confirmed by enzyme linked immunosorbent assay (ELISA). To evaluate osteoblastic differentiation, cellular morphology was assessed every other day and expression and secretion of alkaline phosphatase (ALP), as well as expression levels of osteonectin (OSTN), osteocalcin (OCN), and runt-related transcription factor-2 (Runx2) were measured for up to 14 days. Human and equine BMDMSCs showed a capacity for osteogenic differentiation regardless of genetic modification or dexamethasone supplementation. Dexamethasone supplementation was more important for osteoblastogenic differentiation of equine BMDMSCs than human BMDMSCs. Genetic modification of BMDMSCs increased ALP secretion with AdBMP-2 homodimer having the greatest effect in both human and equine cells compared to AdBMP 7 or AdBMP 2/7. BMP protein elution rates reached their maximal concentration between day 4 and 8 and remained relatively stable thereafter, suggesting that genetically modified BMDMSCs could be useful for cell-based delivery of BMPs to a site of bone formation.

Clinical evaluation of the locking compression plate for fetlock arthrodesis in six thoroughbred racehorses.

OBJECTIVE: To report use of a locking compression plate (LCP) for fetlock arthrodesis in Thoroughbred racehorses after catastrophic disruption of the suspensory apparatus. STUDY DESIGN: Retrospective case study. ANIMALS: Racing Thoroughbreds (n=6) with a catastrophic breakdown injury of the suspensory apparatus. METHODS: Medical records (2004-2006) of horses that had fetlock arthrodesis using an LCP were reviewed. Preoperative recorded variables were: age, gender, affected limb, injury type and occurrence, limb support used and time to surgery. Recorded surgical variables were: implants used and cost, surgery time, and anesthetic recovery method. Postoperative recorded variables included: treatment, physical status, complications, and outcome. RESULTS: Of 6 Thoroughbred racehorses that had LCP arthrodesis, 4 were sound for breeding purposes the next year and 2 horses were euthanatized (1 at 16 days, 1 at 68 days) because of proximal interphalangeal joint (PIJ) luxation. No surgical complications were associated with implant application. Postoperative complications were similar to those reported for other arthrodesis techniques. CONCLUSIONS: LCP is a viable option for fetlock arthrodesis in Thoroughbred racehorses after catastrophic suspensory apparatus disruption. CLINICAL RELEVANCE: Adequate fetlock stability can be achieved with an LCP, and although the repair is likely more stable it is approximately 3 times more expensive than using a limited contact dynamic compression plate (LC-DCP) with cortical screws.

Locking compression plates for pancarpal arthrodesis in a Thoroughbred filly.

OBJECTIVE: To report treatment of a comminuted ulnar carpal (UC) bone fracture associated with carpal instability by pancarpal arthrodesis using 2 locking compression plates (LCP). STUDY DESIGN: Case report. ANIMALS: A 2-year-old Thoroughbred filly. METHODS: An UC fracture and luxation of the proximal row of carpal bones was diagnosed radiographically. Pancarpal arthrodesis was performed with 2 LCP positioned dorsolaterally and dorsomedially and centered over the carpus through a single skin incision. The filly was maintained in a full limb cast for 15 days, followed by a tube cast for 14 days, and subsequently a full limb bandage with caudal splint for 21 days. RESULTS: Two LCP provided appropriate carpal stability resulting in a pasture sound horse 6 months after surgery. The filly was discharged from the hospital 63 days after surgery, walking well with only a slight mechanical lameness. CONCLUSION: Use of 2 LCP applied on the dorsomedial and dorsolateral aspect of the carpus can provide carpal stability for pancarpal arthrodesis. CLINICAL RELEVANCE: Excellent stability of the carpal joints can be achieved with 2 LCP.

Effect of diameter of the drill hole on torque of screw insertion and pushout strength for headless tapered compression screws in simulated fractures of the lateral condyle of the equine third metacarpal bone.

OBJECTIVE: To compare variables for screw insertion, pushout strength, and failure modes for a headless tapered compression screw inserted in standard and oversize holes in a simulated lateral condylar fracture model. SAMPLE POPULATION: 6 pairs of third metacarpal bones from horse cadavers. PROCEDURE: Simulated lateral condylar fractures were created, reduced, and stabilized with a headless tapered compression screw by use of a standard or oversize hole. Torque, work, and time for drilling, tapping, and screw insertion were measured during site preparation and screw implantation. Axial load and displacement were measured during screw pushout. Effects of drill hole size on variables for screw insertion and screw pushout were assessed by use of Wilcoxon tests. RESULTS: Drill time was 59% greater for oversize holes than for standard holes. Variables for tapping (mean maximum torque, total work, positive work, and time) were 42%, 70%, 73%, and 58% less, respectively, for oversize holes, compared with standard holes. Variables for screw pushout testing (mean yield load, failure load, failure displacement, and failure energy) were 40%, 40%, 47%, and 71% less, respectively, for oversize holes, compared with standard holes. Screws could not be completely inserted in 1 standard and 2 oversize holes. CONCLUSIONS AND CLINICAL RELEVANCE: Enlarging the diameter of the drill hole facilitated tapping but decreased overall holding strength of screws. Therefore, holes with a standard diameter are recommended for implantation of variable pitch screws whenever possible. During implantation, care should be taken to ensure that screw threads follow tapped bone threads.