Scapula stress fractures in Thoroughbred racehorses: Eight cases (1997–2006)

No case series exists in the literature describing scapula stress fractures. The purpose of this study was to review the clinical findings, diagnostic images and outcome of 8 horses diagnosed with scapula stress fractures. Scapula stress fractures were seen in Thoroughbred racehorses displaying acute moderate forelimb lameness. Nuclear scintigraphy identified the mid‐distal scapula spine and/or scapula supraspinous fossa as predilection sites. Conservative management resulted in a good prognosis for return to racing, but stress fracture recurrence may be seen.     

Risk factors for race-associated sudden death in Thoroughbred racehorses in the UK (2000-2007)

Reasons for performing study: Sudden death adversely affects racehorse welfare, jockey safety and the public perception of horseracing. Objective: To describe the risk of racing‐associated sudden death in Thoroughbred racehorses in the UK from 2000 to 2007, to identify whether there were risk factors uniquely associated with sudden death and to improve the understanding of the pathogenesis of racing‐associated sudden death by identification of risk factors for such cases. Methods: A sudden death was defined as an acute collapse and death, in an apparently healthy Thoroughbred racehorse, during or immediately after racing, in the absence of clinical data indicative of a catastrophic orthopaedic injury. The retrospective study included 201 case race starts and 705,712 control race starts. Univariable and multivariable logistic regression were used to identify risk factors for sudden death at any one start. Results: In the multivariable model, age, distance, race type, season and number of starts in the 60 days prior to the race were associated with sudden death. Conclusions: The risk factors identified in this study are not uniquely associated with sudden death and have been also been identified in studies using all causes of fatality as the outcome. These data suggest that a generic approach to reduce fatal musculoskeletal injury and sudden death may be possible. Potential relevance: The identification of risk factors allows speculation on the underlying mechanisms of sudden death in racing. This may stimulate hypothesis‐led investigations into the pathogenesis of exercise‐related arrhythmias, exercise‐induced pulmonary haemorrhage and blood vessel rupture. See also correspondence by Cook     

Long-term study of partial arytenoidectomy with primary mucosal closure in 76 Thoroughbred racehorses (1992-2006)

REASON FOR PERFORMING STUDY: The effectiveness and best method to perform a partial arytenoidectomy in racehorses is unclear. This study was performed to evaluate the success of and complications that can occur after a unilateral partial arytenoidectomy with primary mucosal closure in Thoroughbred racehorses. HYPOTHESIS: Partial arytenoidectomy is an effective surgical procedure to return Thoroughbred racehorses, afflicted by arytenoid chondropathy or a failed laryngoplasty, to preoperative levels of performance. METHODS: Seventy-six Thoroughbred racehorses admitted to the New Bolton Centre between 1992 and 2006 were assessed. Information was obtained from the medical records about the horse, laryngeal abnormalities, surgery and other findings during hospitalisation. Racing information was evaluated relative to those independent variables by an analysis of variance with a level of significance of P<0.05. RESULTS: Arytenoid chondropathy was the presenting complaint in 54 horses and failed laryngoplasty in 22 horses. Thirteen horses (17%) underwent a second surgery for laser excision of intralaryngeal granulation tissue at the arytenoidectomy site. Seventy-three horses were discharged from the hospital and racing outcome was evaluated. Sixty horses (82%) raced after surgery and 46 horses (63%) raced 5 or more times after surgery. The median time from surgery to the first start was 6 months. The average earnings/start was not significantly different before and after surgery. There was no association between earnings after surgery and age, gender, location of lesion, type of lesion, duration of tracheal intubation or undergoing a second surgery. CONCLUSIONS AND POTENTIAL RELEVANCE: A Thoroughbred racehorse is likely to race after a unilateral partial arytenoidectomy with primary mucosal closure and return to a preoperative level of performance.     

Intralesional injection of insulin-like growth factor-I for treatment of superficial digital flexor tendonitis in Thoroughbred racehorses: 40 cases (2000-2004)

OBJECTIVE-To evaluate outcome after intralesional injection of insulin-like growth factor-I (IGF-I) for treatment of superficial digital flexor (SDF) tendonitis in Thoroughbred racehorses. DESIGN-Retrospective case series. ANIMALS-40 Thoroughbred racehorses. PROCEDURES-Medical records of racehorses with SDF tendonitis treated within 13 weeks after injury by intralesional injection of IGF-I (25 or 50 μg every other day for 4 or 5 treatments) were reviewed. Outcome was determined via analysis of race records, owner follow-up, and examination. RESULTS-Mean age of the horses was 3.1 years (range, 2 to 7 years), and time from injury to treatment ranged from 8 to 90 days. Mean ± SD approximate lesion length on admission was 15.6 ± 6.0 cm, and mean percentage cross-sectional area of the tendon affected was 26 ± 18%. Twenty-six of the 40 horses underwent desmotomy of the accessory ligament of the SDF tendon. Echolucency was reduced in 23 of 26 horses by the end of the treatment period. Twenty-one of 34 (62%) horses for which race data were available raced at least once after treatment, including 10 (30%) horses that raced between 1 and 4 times and 11 horses (32%) that raced ≥ 5 times. Thirteen of 28 (46%) horses had a recurrence of tendonitis or developed tendonitis elsewhere. CONCLUSIONS AND CLINICAL RELEVANCE-Results suggested that in Thoroughbred racehorses with SDF tendonitis, intralesional injection of IGF-I led to a decrease in ultrasonographic lesion severity, but treated horses had only a moderate prognosis for return to racing.     

Descriptive epidemiology of fractures occurring in British Thoroughbred racehorses in training

REASONS FOR PERFORMING STUDY: Musculoskeletal injury is the major cause of days lost from training and wastage in Thoroughbred racehorses. Little scientific information is available on the majority of injuries occurring in training. OBJECTIVES: To estimate the incidence of fractures in British racehorses in training and describe the occurrence of different fracture types and bones involved. METHODS: Thirteen UK racehorse trainers participated in a prospective study, providing data on horses in their care for 2 years. Details on horses, their daily exercise and fracture occurrence were recorded. RESULTS: A total of 1178 horses provided 12,893 months at risk. Nontraumatic fracture incidence was 1.15/100 horse months (95% CI = 0.98, 1.35) and 78% of fractures occurred during training. A wide variety of fracture types and bones were involved, although at least 57% were stress fractures. Pelvic and tibial stress injuries accounted for 28% of fractures diagnosed. CONCLUSIONS: It is important to study injuries in training as well as in racing. The number of stress fractures suggests that training regimes for young Thoroughbreds could often be improved to create a more robust skeleton, able to withstand injury. POTENTIAL RELEVANCE: Studying injuries in racehorses in training can provide a scientific basis for the design of safer training regimes.     

Quantitative analysis of scintigraphic findings in tibial stress fractures in Thoroughbred racehorses

OBJECTIVE: To develop a quantitative method of interpreting tibial scintigrams of Thoroughbred racehorses with tibial stress fractures that may facilitate diagnosis of fractures and to provide prognostic information regarding future performance of affected horses. ANIMALS: 35 Thoroughbred racehorses. PROCEDURES: Static bone-phase scintigrams of tibial stress fractures were quantitatively analyzed by use of ratios of the mean radionuclide counts per pixel in a region of interest (ROI) drawn around the area of increased uptake of radiopharmaceutical to mean counts per pixel in a second ROI drawn around an apparently normal area of the tibial diaphysis. In horses with unilateral fractures, ratios for the contralateral tibia were determined by use of 2 ROIs drawn at the same positions as the ROIs in the fractured tibia. Ratios were compared between fractured versus apparently normal tibias, between horses that returned to racing versus those that did not, and among horses with various grades of lameness. The association between ratios for fractured tibias and intervals between diagnosis and return to racing was also assessed. RESULTS: Mean ratio of ROIs in apparently normal tibias was 1.35 (95% confidence interval [CI], 1.21 to 1.50); that in tibias with stress fractures was 3.55 (95% CI, 2.50 to 4.60). These ratios were significantly different. None of the associations between ratios for fractured tibias and grades of lameness or performance outcomes were significant. CONCLUSIONS AND CLINICAL RELEVANCE: Tibial stress fracture scintigrams can be quantitatively analyzed. A prospective study with a controlled rehabilitation period is necessary to evaluate the possible applications of this method.     

Subchondral cystic lesions of the proximal extremity of the tibia in horses: 12 cases (1983-2000)

OBJECTIVE: To determine clinical and radiographic features of subchondral cystic lesions (SCL) of the proximal extremity of the tibia in horses that could be used to classify these lesions as being related to osteochondrosis or osteoarthritis and to evaluate results of surgical debridement. DESIGN: Retrospective study. ANIMALS: 12 horses with 14 SCL. PROCEDURE: Medical records and radiographs obtained before and after treatment were reviewed. RESULTS: In 6 young horses (8 lesions), SCL were considered to be related to osteochondrosis; all involved the lateral tibial condyle. The remaining 6 horses were mature and had radiographic evidence of osteoarthritis in addition to SCL. Arthroscopic debridement was performed in 4 horses in which lesions were considered to be a result of osteochondrosis and in 3 horses with osteoarthritis. Three horses in which SCL were considered to be a result of osteochondrosis performed athletically after debridement. Two horses with moderate osteoarthritis returned to work after arthroscopic debridement but at a lower level of athletic performance. One horse with SCL related to osteochondrosis responded to medical treatment and went on to race. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that arthroscopic debridement of SCL is feasible in horses in which lesions involve the cranial portion of the lateral or medial tibial condyle, and that treated horses may be able to perform athletically.     

Surgical and nonsurgical management of sagittal slab fractures of the third carpal bone in racehorses: 32 cases (1991-2001)

OBJECTIVE: To compare results (ie, return to racing and earnings per race start) of surgical versus nonsurgical management of sagittal slab fractures of the third carpal bone in racehorses. DESIGN: Retrospective study. ANIMALS: 32 racehorses (19 Thoroughbreds, 11 Standardbreds, and 2 Arabians). PROCEDURE: Medical records and radiographs were reviewed to obtain information regarding signalment and treatment. Follow-up information was obtained from race records. Robust regression analysis was performed to evaluate earnings per start in horses that raced at least once before and after injury. RESULTS: 22 (69%) horses raced at least once after treatment of the fracture. All 7 horses treated by means of interfragmentary compression raced after treatment, and horses that underwent interfragmentary compression had significantly higher earnings per start after the injury than did horses treated without surgery. Eight of 9 horses treated by means of arthroscopic debridement of the damaged cartilage and bone raced after treatment, but only 7 of 16 horses treated without surgery (ie, stall rest) were able to return to racing after treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that racehorses with sagittal slab fractures of the third carpal bone have a favorable prognosis for return to racing after treatment. Horses treated surgically were more likely to race after treatment than were horses treated without surgery.     

An association between complete and incomplete stress fractures of the humerus in racehorses.

Twenty-one horses had a complete unilateral humeral fracture during race training or racing at a California racetrack during the period 24 February 1990 to 10 July 1991. Fractures occurred approximately equally in left and right limbs, and in males and females. Most fractures occurred during training, and in 2- and 3-year-old horses. Only 5 of 16 Thoroughbred horses with known racing records had previously raced more than once, and their mean time between races was less than the time between their last race and fracture (P = 0.07). Ten of 13 humeri studied further had gross evidence of periosteal callus bridging one portion of the fracture line, indicative of a pre-existing stress fracture.     

Qualitative and quantitative documentation of the racing performance of 461 Thoroughbred racehorses after arthroscopic removal of dorsoproximal first phalanx osteochondral fractures (1986-1995)

The purpose of this study was to examine the longevity of postoperative careers and quality of performance of 461 Thoroughbred racehorses after arthroscopic removal of dorsoproximal first phalanx (P1) osteochondral fractures. Six hundred and 59 dorsoproximal P1 chip fractures were removed arthroscopically from 574 joints in 461 horses presented for lameness or decreased performance attributed to the chip fractures. Radiological and arthroscopic examination revealed an average of 1.43 fragment sites/horse, 1.15 fragment sites/joint and 1.25 affected joints/horse. Eighty-nine percent of the horses (411/461) raced after surgery and 82% (377/461) did so at the same or higher class. Fifty horses did not race after surgery. Sixty-eight percent of the horses raced in a Stake or Allowance race postoperatively. Data, previously undocumented, establishes that the quantity and quality of performance is not diminished after arthroscopic treatment of dorsoproximal P1 fragmentation. Surgical removal of chip fractures is a means of preserving the economic value of an injured Thoroughbred, allowing a rapid and successful return to racing at the previous level of racing performance.     

Hemangiosarcoma in cats: 53 cases (1992-2002)

OBJECTIVE: To characterize the biological behavior and prognostic factors associated with hemangiosarcoma in cats. DESIGN: Retrospective case series. ANIMALS: 53 cats with hemangiosarcoma. PROCEDURES: Data were retrieved from a state veterinary diagnostic laboratory, 3 veterinary colleges, and a private practice. RESULTS: Cutaneous and subcutaneous tumor locations were more common than visceral (abdominal and thoracic) and oral locations. Surgical excision was the primary treatment in 47 cats. Tumor-free surgical margins were more likely in cutaneous than subcutaneous lesions and were associated with longer survival times. Local recurrence was observed in 6 of 12 cats with subcutaneous lesions for which follow-up was available. Metastatic disease was detected in 5 of 13 cats with adequate staging at initial diagnosis. A sixth cat had pulmonary metastases at the time of euthanasia. In 4 of 10 cats with visceral hemangiosarcoma, the diagnosis was made at necropsy or they were euthanized at the time of diagnosis. Adjuvant therapy was uncommonly used. Eighteen of the 21 known deaths or euthanasias were tumor-related. Higher mitotic counts (> 3 in 10 hpfs) were associated with shorter survival times. CONCLUSIONS AND CLINICAL RELEVANCE: Subcutaneous hemangiosarcoma was more biologically aggressive than the cutaneous form and was more likely to recur locally and result in euthanasia or death of the cat. Metastatic potential of the cutaneous and subcutaneous forms may be greater than previously reported. Visceral hemangiosarcoma is associated with a grave prognosis.     

Palmar carpal osteochondral fragments in racehorses: 31 cases (1994-2004)

OBJECTIVE: To evaluate records of racehorses with palmar carpal osteochondral fragments and determine whether the fragments were indicators of the severity of pathologic joint changes or prognosis. DESIGN: Retrospective case series. ANIMALS: 31 racehorses. PROCEDURES: Medical records, radiographs, and videos of arthroscopic procedures were reviewed. Information gathered included signalment; location, number, and size of the primary lesion; number and size of palmar carpal fragments; and details pertaining to surgical procedures. Outcome variables were obtained from race records. RESULTS: 31 horses met the selection criteria. Multiple palmar fragments were diagnosed in 58% of horses; small fragments (< 3 mm in diameter) were most common (52% of horses). Fifty-two percent of the horses returned to racing, 48% returned to racing and earned money, and 32% had at least 5 more starts. Horses with multiple fragments had significantly less earnings per start and lower performance index values after surgery than those with 1 fragment. Horses with palmar fragments < 3 mm in diameter were significantly less likely to return to racing and have 5 starts or to win money after surgery than horses with larger fragments. CONCLUSIONS AND CLINICAL RELEVANCE: Palmar carpal osteochondral fragments can be used as an indicator of clinically important joint pathology and as a prognostic indicator in racehorses. Horses with multiple small fragments were less likely to successfully return to racing than horses with only dorsally located carpal fragments or horses with 1 or 2 large palmar fragments. When possible, removal of palmar carpal osteochondral fragments should be considered.     

Outcome following surgical removal of nonvisceral soft tissue sarcomas in cats: 42 cases (1992-2000)

OBJECTIVE: To identify factors associated with outcome of cats with nonvisceral soft tissue sarcomas treated with surgery alone. DESIGN: Retrospective study. ANIMALS: 42 cats. PROCEDURE: Medical records were reviewed for clinically relevant data, and histologic samples were examined. Follow-up information was obtained by means of physical examination or through telephone conversations with referring veterinarians and owners. The Kaplan-Meier method was used to construct survival curves. RESULTS: Median survival time was 608 days (range, 85 to 2,291 days), although 24 cats were still alive at the time of the study. Tumor size (ie, diameter) and histologic type were significantly associated with survival time. Median survival time was significantly longer in cats with tumors that were < 2 cm in diameter, compared with cats in which tumors were > 2 cm. Median survival times for cats with a fibrosarcoma or nerve sheath tumor were significantly longer than median time for cats with a malignant fibrous histiocytoma. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that tumor size and type are significantly associated with survival time in cats with nonvisceral soft tissue tumors.     

Endoscopic assessment of airway function as a predictor of racing performance in Thoroughbred yearlings: 427 cases (1997-2000)

OBJECTIVE: To compare endoscopic findings of the upper portion of the respiratory tract in Thoroughbred yearlings with their subsequent race records to determine whether subjective assessment of airway function may be used as a predictor of future racing performance. DESIGN: Retrospective study. ANIMALS: 427 Thoroughbred yearlings. PROCEDURES: Endoscopic examination findings were obtained from the medical records and the videoendoscopic repository of the Keeneland 1996 September yearling sales. Racing records were requested for the yearlings through the end of their 4-year-old racing season (1997-2000). Twenty-nine measures of racing performance were correlated with endoscopic findings. Subjective arytenoid cartilage movement grades were determined, using a 4-point grading scale (grade 1 = symmetrical synchronous abduction of the arytenoid cartilages; grade 4 = no substantial movement of the left arytenoid cartilage). RESULTS: Of the 427 Thoroughbred yearlings included in this study, 364 established race records, and 63 did not. Opinions regarding suitability for purchase, meeting conditions of the sale, and the presence of epiglottic abnormalities had no significant association with racing performance. Arytenoid cartilage movement grades were significantly associated with many of the dependent variables. However, palatine abnormalities were not predictive of inferior racing performance. CONCLUSIONS AND CLINICAL RELEVANCE: Thoroughbred yearlings with grade-1 and -2 arytenoid cartilage movements had significantly better racing performance as adults, compared with yearlings with grade-3 arytenoid cartilage movements. In contrast, epiglottic and palatine abnormalities were not predictive of inferior racing performance. Therefore, evaluation of laryngeal function, but not epiglottic or palatine abnormalities, using the 4-point grading system, should be the major factor in developing recommendations for prospective buyers.