Articular stress fracture arising from the distal end of the third metacarpal bone (MC3) is a common serious injury in Thoroughbred racehorses. Currently, there is no method for predicting fracture risk clinically. We describe an ex-vivo biomechanical model in which we measured subchondral crack micromotion under compressive loading that modeled high speed running. Using this model, we determined the relationship between subchondral crack dimensions measured using computed tomography (CT) and crack micromotion. Thoracic limbs from 40 Thoroughbred racehorses that had sustained a catastrophic injury were studied. Limbs were radiographed and examined using CT. Parasagittal subchondral fatigue crack dimensions were measured on CT images using image analysis software. MC3 bones with fatigue cracks were tested using five cycles of compressive loading at -7,500N (38 condyles, 18 horses). Crack motion was recorded using an extensometer. Mechanical testing was validated using bones with 3 mm and 5 mm deep parasagittal subchondral slots that modeled naturally occurring fatigue cracks. After testing, subchondral crack density was determined histologically. Creation of parasagittal subchondral slots induced significant micromotion during loading (p<0.001). In our biomechanical model, we found a significant positive correlation between extensometer micromotion and parasagittal crack area derived from reconstructed CT images (SR = 0.32, p<0.05). Correlations with transverse and frontal plane crack lengths were not significant. Histologic fatigue damage was not significantly correlated with crack dimensions determined by CT or extensometer micromotion. Bones with parasagittal crack area measurements above 30 mm2 may have a high risk of crack propagation and condylar fracture in vivo because of crack micromotion. In conclusion, our results suggest that CT could be used to quantify subchondral fatigue crack dimensions in racing Thoroughbred horses in-vivo to assess risk of condylar fracture. Horses with parasagittal crack arrays that exceed 30 mm2 may have a high risk for development of condylar fracture.
Objective To describe perioperative antimicrobial use in horses undergoing elective arthroscopy. Study design. Retrospective study. Sample population. Horses that underwent elective arthroscopy at one institution between July 2016 and May 2018, excluding those with a suspected infectious orthopedic disease or with a comorbidity that may have impacted prophylactic antimicrobial use decisions. Methods Medical records were reviewed to evaluate preoperative, intraoperative, and postoperative antimicrobial drug selection, dose, and timing. Associations between body weight and underdosing were evaluated by using analysis of variance, χ2 test was used for categorical comparisons, and least squares fit was used to evaluate factors associated with duration of postoperative antimicrobials. Results Among 150 horses, 149 (99.3%) received systemic preoperative antimicrobials. Only 53 (40.2%) horses were administered doses within 60 minutes of surgical incision. First incision was performed more than two half‐lives after administration of sodium penicillin in 46 of 131 (35.1%) horses but in only 1 of 106 (0.8%) horses that received trimethoprim‐sulfadoxine. Body weight was associated with underdosing for penicillin (P = .0075) and trimethoprim‐sulfadoxine (P = .002) but not gentamicin (P = .92). Twenty‐six (17%) horses received one postoperative antimicrobial dose, while antimicrobials were continued in hospital for a mean of 22.3 ± 4.4 hours after surgery in the other 123 horses. Among the 149 discharged horses, 115 (77.2%) were prescribed antimicrobials after discharge (range, 3‐10 days; median, 3 days, interquartile range, 0 days). Conclusion Deviations from common recommendations were apparent and provide evidence for the requirement to develop interventions to optimize perioperative prophylaxis. Clinical significance Perioperative antimicrobial use practices should be regularly assessed to provide a benchmark and identify areas for intervention.
Summary This study reports a distinct presentation of cellulitis, which involved formation of perisuspensory abscessation in eight horses. Medical records of horses presented for cellulitis unresponsive to medical treatment were reviewed. Cases in which perisuspensory abscesses were diagnosed were included. All abscesses formed between the cannon bone and suspensory ligament and extended around one or both suspensory branches. Abscesses were diagnosed via ultrasonography upon admission in three horses and developed within a few days following admission in five horses. All horses were treated with broad‐spectrum antibiotics, anti‐inflammatories, topical therapies and regional limb perfusions; however, only partial improvement of clinical signs was observed with medical therapy alone. Full resolution of clinical signs was obtained in all cases once the abscess was surgically lanced and drained. The surgical drainage was performed standing in seven cases and under general anaesthesia in one. In all cases, Staphylococcus aureus was cultured. Six out of eight isolates showed at least some level of antibiotic resistance, and penicillin and trimethoprim sulfonamides were most commonly involved. Short‐term complications included skin necrosis in two cases and mild impaction colic in two cases and were successfully treated. All horses were discharged from the hospital within 4–13 days and were sound upon discharge. All Thoroughbreds (n = 7) were able to return to their intended use, and the Standardbred was unraced prior to the cellulitis event and remained unraced afterwards.
CASE DESCRIPTION A 4-year-old 55.0-kg (121-lb) spayed female Vietnamese potbellied pig was examined for right forelimb lameness of 2 months’ duration that had not resolved following rest and treatment with meloxicam. CLINICAL FINDINGS The only abnormality identified during physical examination was non–weight-bearing lameness of the right forelimb. Radiographic and CT examinations revealed that the right humerus was displaced laterally and slightly cranial to the glenoid cavity of the scapula with moderate evidence of osteoarthritis. Chronic craniolateral luxation of the right humeral (shoulder) joint was diagnosed. TREATMENT AND OUTCOME Arthrodesis of the right shoulder joint was performed surgically by a lateral approach. The humeral head was replaced in the glenoid cavity. The joint was immobilized at a 115° angle with two 3.5-mm string-of-pearls orthopedic plates and a 4.5-mm cortical bone screw placed across the joint in lag fashion. The pig recovered from surgery without any complications. At 6 weeks and 5 months after surgery, the pig had the expected mechanical lameness of the right forelimb owing to immobilization of the shoulder joint and radiographic evidence of progressive arthrodesis of that joint. The pig had resumed its usual activities and had only mechanical lameness present 1 year after surgery. CLINICAL RELEVANCE This report described successful treatment of chronic shoulder joint luxation in an adult Vietnamese potbellied pig by surgical arthrodesis of the affected joint. The described procedure might also be useful for treatment of other debilitating conditions of the shoulder joint, such as severe osteoarthritis or intra-articular fractures, in pigs.
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