Pieter H. L. Ramzan

Background: Carpal lameness is a common cause of wastage in Thoroughbred racehorses, with the middle carpal joint most frequently affected. Evaluation of the dorsoproximal–dorsodistal oblique (DPr–DDiO) radiographic projection of the third carpal bone (C3) is fundamental in clinical and pre‐purchase assessment of Thoroughbred racehorses. A standardised grading system is needed to improve consistency of diagnosis and reporting between clinicians. Objectives: To develop and assess inter‐rater reliability of a novel grading system for evaluating radiological features of the third carpal bone on the C3 skyline projection. Study Design: Retrospective multi‐rater agreement study. Methods: The novel grading system assessed bone radiopacity changes (Grades 0–4) and lucency characteristics (Grades A–C). Bone density ranged from Grade 0 (even trabecular distribution) to Grade 3 (severe radiopacity), with Grade 4 indicating overt evidence of fracture. Lucencies were classified as A (small, dorsal), B (linear or curvilinear, central), or C (extensive). Six observers independently graded 250 radiographs from a first‐opinion Thoroughbred racehorse caseload. Inter‐rater agreement was determined using Kappa statistics. Results: Category‐specific bone density grading revealed moderate agreement for Grades 0, 1, and 3 ( κ = 0.45, 0.41, and 0.53), fair agreement for Grade 2 ( κ = 0.36), and moderate to substantial agreement for Grade 4 ( κ = 0.68). Inter‐rater agreement on lucency classification ranged from fair (Grade B, κ = 0.28; Grade A, κ = 0.39) to moderate (Grade C, κ = 0.52). Unweighted kappa for bone density grading was 0.44 and 0.47 for presence of lucency grading. Weighted kappa for bone density grading was 0.59, indicating moderate agreement. Main Limitations: All observers were highly experienced clinicians and intra‐observer reliability was not assessed. Conclusions: Inter‐rater agreement using a novel grading system for the evaluation of the C3 ‘skyline’ radiographic projection was generally moderate, and substantial for fracture. Adoption of this grading system in clinical practice will assist standardisation of diagnostic and prognostic evaluation of this important injury site.

Background: Catastrophic injury has a low incidence but leads to the death of many Thoroughbred racehorses. Objectives: To determine sensitivity, specificity, and reliability for third metacarpal condylar stress fracture risk assessment from digital radiographs (DR) and standing computed tomography (sCT). Study design: Controlled ex vivo experiment. Methods: A blinded set of metacarpophalangeal joint DR and sCT images were prepared from 31 Thoroughbreds. Four observers evaluated the condyles and parasagittal grooves (PSG) of the third metacarpal bone for the extent of dense bone and lucency/fissure and assigned a risk assessment grade for condylar stress fracture based on imaging features. Sensitivity and specificity for detection of subchondral structural changes in the condyles and PSG, and for risk assessment for condylar stress fracture were determined by comparison with a reference assessment based on sCT and joint surface examination. Agreement between observers and the reference assessment and reliability between observers were determined. Intra‐observer repeatability was also assessed. Results: Sensitivity for detection of structural change was lower than specificity for both imaging methods and all observers. For agreement with the reference assessment of structural change, correlation coefficients were generally below 0.5 for DR and 0.49–0.82 for sCT. For horses categorised as normal risk on reference assessment, observer assessment often agreed with the reference. Sensitivity for risk assessment was lower than specificity for all observers. For horses with a reference assessment of high risk of injury, observers generally underestimated risk. Diagnostic sensitivity of risk assessment was improved with sCT imaging, particularly for horses categorised as having elevated risk of injury from the reference assessment. Assessment repeatability and reliability was better with sCT than DR. Main limitations: The ex vivo study design influenced DR image sets. Conclusions: Risk assessment through screening with diagnostic imaging is a promising approach to improve injury prevention in racing Thoroughbreds. Knowledge of sensitivity and specificity of fetlock lesion detection provides the critical guidance needed to improve racehorse screening programs. We found improved detection of MC3 subchondral structural change and risk assessment for condylar stress fracture with sCT ex vivo.

Background: Catastrophic injury has a low incidence but leads to the death of many Thoroughbred racehorses annually. Effective screening for injury risk needs to solve the false negative diagnostic sensitivity problem. Objectives: To determine sensitivity, specificity, and reliability for condylar stress fracture risk assessment from fetlock digital radiographs (DR) and standing computed tomography (sCT) imaging (Asto CT Equina ^® ). Study design: Controlled ex vivo experiment. Methods: A blinded set of DR and sCT images of the thoracic limb fetlock were prepared from 31 Thoroughbred racehorses and reviewed by four veterinarians. Observers evaluated the condyles and parasagittal grooves (PSG) of the third metacarpal subchondral bone (MC3) for the extent of dense bone and lucency/fissure and assigned a risk assessment grade for condylar stress fracture based on imaging findings. Sensitivity and specificity for detection of subchondral structural changes in the condyles and PSG of the third metacarpal bone and for risk assessment for condylar stress fracture were determined by comparison with a reference assessment. Agreement between each observer and the reference assessment and reliability between observers were determined. Intra-observer repeatability was also assessed. Results: Intra-observer repeatability was identified for both DR and sCT imaging. Sensitivity for detection of structural change was lower than specificity for both imaging methods and all observers. For horses with a normal level of risk, observer assessment often agreed with the reference assessment. Sensitivity for risk assessment was lower than specificity for all observers. For horses with a high risk of serious injury, observers generally underestimated the level of risk. Diagnostic sensitivity of risk assessment was improved with sCT imaging, particularly for horses with elevated risk of injury. Assessment reliability was better with sCT than DR. Main limitations: The ex vivo study design influenced DR image sets regarding limb positioning and image contrast compared with in vivo DR imaging. Conclusions: Risk assessment through screening with diagnostic imaging is a promising approach to improve injury prevention in racing Thoroughbreds. Knowledge of sensitivity and specificity of fetlock lesion detection by DR and sCT provides critical guidance regarding development of improved screening programs for racehorses using diagnostic imaging. We found improved detection of MC3 subchondral structural change and risk assessment for condylar stress fracture with sCT ex vivo .

Background: Rib fractures in adult horses are poorly documented. Objectives: To describe the presenting signs, diagnosis, treatment and outcome of horses diagnosed with rib fracture. Study design: Retrospective case series. Method: The clinical records and diagnostic images of all adult horses diagnosed with a rib fracture at three referral centres over a 15‐year period were reviewed. Results: Seventy‐three horses met the inclusion criteria. Horses presented due to either resistance to ridden work and poor performance (n = 41), lameness (n = 21) or trauma (n = 7). In four horses, the presenting complaint was not recorded. Clinical assessment and palpation localised the site of injury in 18/47 cases where recorded. Nuclear scintigraphic examination identified all fracture sites in which it was performed (59/59). In 10/24 horses, radiographic examination confirmed rib fracture. Ultrasonographic examination confirmed rib fracture in 58/59 horses (98%; 95% CI 92‐100). Six horses underwent surgery due to ongoing clinical signs and non‐healing fracture; all other horses were managed conservatively. Fifty‐five horses were available for long‐term follow up (>1 year), of which 28 (51%; 95% CI 38‐64) returned to their previous level of exercise. Twelve horses did not return to their previous level of exercise due to lameness unrelated to the rib fracture and seven horses were subjected to euthanasia, of which three were as a result of the rib fracture. Eight horses did not return to their previous level of exercise for other reasons. Main limitations: Incomplete data set due to retrospective case series. Conclusions: Although uncommon, rib fractures should be considered in cases of reduced performance or resistance during ridden exercise. Palpation may be unrewarding. Scintigraphy and ultrasonography are useful in identifying the fracture site. Rib fractures in horses carry a fair prognosis and can be managed conservatively in most cases.

Background: Arthroscopy has been advocated as the treatment of choice for dorsal osteochondral chip fracture of the metacarpo/metatarsophalangeal (MCP/MTP) joint. However, there is no published research on racing performance outcomes of horses with this pathology managed nonsurgically.Objectives: To compare racing career outcomes of Thoroughbred racehorses with nonsurgically (non‐SX) or surgically (SX) managed MCP/MTP dorsal osteochondral chip fracture alongside a cohort of horses with no dorsal osteochondral chip fracture (unexposed).Study design: Retrospective cohort study conducted between 2006 and 2014.Methods: Radiographs of Thoroughbred racehorses were reviewed to identify MCP/MTP dorsal osteochondral chip fractures. Unexposed horses under the care of the same practice were recruited randomly from training records. Racing outcomes were analysed using survival analysis and logistic, linear and negative binomial regression techniques.Results: Dorsal osteochondral chip fractures were identified in 98 (70 non‐SX, 28 SX) horses and compared with 648 unexposed horses. There was no significant difference among non‐SX, SX, and unexposed horses in respect of total career starts, or likelihood of ever winning, placing, or earning money in a race (P > .05). SX horses had a significantly higher rate of wins/start than non‐SX horses (rate ratio 1.6, CI 1.1‐2.4, P = .02) and unexposed horses (rate ratio 1.9, CI 1.3‐2.8, P = .001). Total career earnings for the SX horses were 4.1 times that of the unexposed horses (95% CI 1.2‐14.5, P = .03), although total career earnings did not differ significantly between non‐SX and unexposed horses (P = .8).Main limitations: Retrospective observational study where management technique was not randomised or blinded. Small number of surgically managed horses and potential selection bias for surgical management.Conclusions: Nonsurgical management of this injury appears to be a valid management choice given that it was not associated with significant effects on racing career performance relative to a large unexposed cohort in this study population.

Summary: Background: Arthroscopy is considered the treatment of choice for dorsal osteochondral chip fractures of the metacarpo/metatarsophalangeal (MCP/MTP) joints in the racehorse; however, there is no published research on non‐surgical management of this injury. Objectives: To compare clinical features, intra‐articular medication use and return to racing in Thoroughbred racehorses with non‐surgically (non‐SX) or surgically (SX) managed MCP/MTP dorsal chip fracture. Study design: Retrospective observational study conducted between 2006 and 2014. Methods: Radiographs of Thoroughbred racehorses were reviewed to identify MCP/MTP dorsal osteochondral chip fractures. Clinical and intra‐articular medication data were obtained from veterinary records, and return to racing data from a public online resource. Results: A total of 98 MCP/MTP horses with dorsal chip fractures were identified (70 non‐SX, 28 SX). Median age was 2 years (range 2–7 years). Osteochondral chip fractures predominantly involved the forelimbs (n = 92, 93.9%) and the majority were considered by the treating clinician to be clinically active (n = 85, 86.7%). Significantly more SX horses had a reported ongoing problem associated with the affected joint than non‐SX horses (P = 0.002), however there was no significant difference between non‐SX and SX horses in the number of intra‐articular medications of affected joint per month of follow‐up (P = 0.22). The proportion of horses racing post‐diagnosis was not significantly different between non‐SX (55/70; 78.6%, 95% CI 69.0, 88.2%) and SX horses (24/28; 85.7%, 95% CI 72.8, 98.73%) (P = 0.57). Median time to first start following diagnosis for non‐SX (106 days, range 1–326) was significantly shorter than for SX horses (203 days, range 9–559) (P = 0.002). Main limitations: Management technique was not randomised or blinded, with few surgically managed horses. Conclusions: The results contribute to the current evidence base used to guide management of osteochondral chip fractures of the MCP/MTP joints in the racehorse, and indicate that non‐surgical management may be a valid treatment option for some injuries.

Summary: Background: There are few observational studies regarding the potentially serious complication of synovial sepsis following intrasynovial medication in general equine practice. Quantification of risk is fundamental to fully inform decision‐making and owner consent prior to undertaking procedures. Objectives: To describe the occurrence of synovial sepsis following intrasynovial injections in a large ambulatory equine practice between 2006–2011. Study design: Retrospective cohort study. Methods: Medication records were cross‐referenced against synovial cytology submissions and hospital admissions for synovial sepsis. The occurrence of synovial sepsis within strata of interest, including horse age, sex and product used were described as proportions with corresponding 95% confidence intervals, and measures of attributable risks. Results: In the study period, 9456 intrasynovial medications were performed in 4331 sessions. The most frequently used medications were: corticosteroids (3869/4331, 89.3% [95% CI 88.4, 90.3%]), hyaluronate (3617/4331, 83.5% [95% CI 82.4, 84.6%]) and amikacin sulphate (4044/4331, 93.4% [95% CI 92.6, 94.1%]). Overall four horses developed post medication synovial sepsis (0.04% [95% CI 0.0, 0.08%] of all medications), two of these cases were given polysulphated glycosaminoglycans and hyaluronate (2/14, 14.3% [95% CI 0.0, 32.6%]), two were given triamcinolone acetonide (2/3592, 0.1% [95% CI 0.0, 0.1%]), and hyaluronate (2/3617, 0.06% [95% CI 0.0, 0.1%]). One of these cases had received concurrent medication with amikacin sulphate (1/4044, 0.02% [95% CI 0.0, 0.1%]). All four cases returned to racing following joint lavage. Main limitations: Due to the low frequency of cases multivariable statistical analysis was not performed. Although the study was conducted in an ambulatory setting, the population included a high number of racehorses, limiting application to the general horse population. Conclusions: The frequency of synovial sepsis in this population of horses was 0.04%. These data may be helpful in informing clients regarding the potential risks of adverse complications resulting from intrasynovial medication.

Summary: Background: Some sagittal plane fractures of the equine third carpal bone are difficult to detect with conventional radiographic projections. Objectives: To describe a novel radiographic projection for the detection of sagittal plane slab fractures of the equine third carpal bone. Study design: Retrospective study of radiological records. Methods: From a first opinion Thoroughbred racehorse caseload, cases were included for analysis if sagittal fracture of the third carpal bone was evident on a dorsoproximal lateral‐palmarodistal medial oblique ( DP rL‐ PD i MO ) projection of the distal row of carpal bones and not visible on the standard dorsoproximal‐dorsodistal oblique ( DP r‐ DD iO) projection. Results: Eight cases in which radiological identification of fracture was dependent on the DP rL‐ PD i MO projection were identified from August 2013 to August 2017. Main limitations: Unblinded study. Conclusions: Conventional radiographic projections can fail to detect some serious fractures of the equine third carpal bone. The DP rL‐ PD i MO projection has a role in the investigation of suspected carpal injury in racehorses.