Arthroscopically‐assisted removal of an osteochondral fragment from the equine elbow using a caudo‐medial approach

An 8‐year‐old Polo pony mare was admitted for investigation of lameness related to swelling of the elbow. An intra‐articular fragment from the proximo‐medial radius was identified on radiographic examination. The fragment was removed arthroscopically under general anaesthesia via a caudo‐medial approach to the elbow joint.     

Developmental orthopaedic disease and early osteoarthritis of the temporomandibular joint in a 15-month-old Quarter Horse filly

A 15-month-old Quarter Horse filly presented for evaluation of hard swellings over the left temporomandibular joint (TMJ) and the right metatarsophalangeal joint (MTPJ). The TMJ swelling had been noted since she was weaned at 4 months of age and had slowly enlarged since then. Radiographs of both TMJs and the right MTPJ were performed, which revealed severe osteoarthrosis associated with osteochondrosis-like lesions. The filly was subjected to euthanasia due to the poor prognosis for performance. Computed tomography and post-mortem examination, including histopathology of the left TMJ, revealed early osteoarthritis (OA) associated with osteochondrosis-like lesions of the left TMJ and the right MTPJ, while the right hind proximal interphalangeal joint (PIPJ) was diagnosed with early OA.     

Comparison of skeletal scintigraphy and standing 18F-NaF positron emission tomography for imaging of the fetlock in 33 Thoroughbred racehorses

This retrospective, methods comparison study aimed to compare skeletal scintigraphy and ¹⁸F-NaF positron emission tomography (PET) for the detection of abnormalities in the fetlocks of Thoroughbred racehorses. Thirty-three horses (72 limbs) imaged with both scintigraphy and ¹⁸F-NaF PET, for investigation of lameness or poor performance related to the fetlock, were included. Seven observers, including experienced racetrack practitioners, surgery and imaging residents, and a board-certified veterinary radiologist, independently reviewed all data for evidence of increased radiopharmaceutical uptake in 10 different regions of interest. The interobserver agreement was higher for PET (Kappa-weighted (K-w) 0.73 (0.51–0.84)) (median (range)) than for scintigraphy (0.61 (0.40–0.77)) (P < 0.0001). When scintigraphy and PET were compared, the agreement was fair (K-w 0.29). More sites of increased uptake were identified using PET compared with scintigraphy. Agreement between the two modalities was higher for the palmar/plantar metacarpal/metatarsal condylar regions (K-w 0.59) than for the proximal sesamoid bones (K-w 0.25). Increased radiopharmaceutical uptake was detected in the medial proximal sesamoid bone in 6.9% and 22.2% of limbs with scintigraphy and PET, respectively. The high interobserver agreement for PET, despite the recent introduction of this technique, demonstrates the ease of clinical interpretation of PET scans. The higher number of lesions detected with PET compared with scintigraphy can be explained by the higher spatial resolution and cross-sectional nature of this modality. Study findings supported using PET in a clinical population of racehorses, in particular for the assessment of the proximal sesamoid bones.     

Osteochondral dysplasia of the coxofemoral joints in a Friesian foal: Clinical findings and methods of diagnosis

Diseases of the coxofemoral (hip) joint are infrequently diagnosed in horses. Most cases are presented as an unilateral condition and usually are of traumatic origin. This case report describes a Friesian foal with a clinically obvious thoracolumbar kyphosis, combined with a weight‐shifting stance and a shortened stride of both hindlimbs. General clinical and lameness examinations, computed tomographic examination of the pelvis, and macroscopic and histopathological examinations of the coxofemoral joints were performed. This revealed a final, phenotypical diagnosis of a primary osteochondral dysplasia of both coxofemoral joints with secondary osteoarthritis. Similar to the occurrence of this condition in other species and considering the small genetic basis of the Friesian horse breed, a genetic predisposing factor is suspected to play a key role in the developing mechanism of dysplastic coxofemoral joint disease in horses as illustrated with this case. Computed tomography scanning appears to be a useful imaging technique in the detection of coxofemoral joint disease in small horses and foals.     

THE EFFECT OF SEQUENCE SELECTION AND FIELD STRENGTH ON DETECTION OF OSTEOCHONDRAL DEFECTS IN THE METACARPOPHALANGEAL JOINT

Six cadaver forelimbs were imaged in two high‐field magnetic resonance (MR) systems and one low‐field MR system following the creation of osteochondral defects on the palmar distal aspect of the third metacarpal bone. The following sequences were performed using all three systems: proton density (PD) turbo spin echo, T2^* gradient echo (GRE), T2‐weighted fast spin echo, and short tau inversion recovery. In addition, 3D T1 GRE sagittal standard and motion insensitive sequences were obtained using the low‐field system. PD fat saturated and 3D T1‐weighted spoiled GRE images with and without fat suppression were acquired with the high‐field systems. Lesions were measured and assigned a confidence score. The images obtained using high‐field systems (1.0 and 1.5 T) more accurately represented the osteochondral defects when compared with low‐field system (0.27 T) images. The largest difference was observed when evaluating articular cartilage defects, which were not identified on the low‐field images. Sequence selection affected the appearance of the lesions. On all systems the turbo and fast spin echo sequences more accurately represented the lesion size and shape when compared with the GRE sequences. The T1 GRE sequence is the only sequence that appears to allow visualization of the articular cartilage on the low‐field images, but is limited in providing adequate cartilage visualization. Confidence scores were greater on the high‐field systems when compared with the low‐field system.     

Arthroscopic removal of axial osteochondral fragments of the proximoplantar aspect of the proximal phalanx using electrocautery probes in 23 standardbred racehorses

OBJECTIVES: To describe the outcome after arthroscopic electrosurgical excision of axial osteochondral (OC) fragments of the proximal plantar aspect of the 1st phalanx (P1) in horses. STUDY DESIGN: Retrospective study. POPULATION: Twenty-three Standardbred racehorses. METHODS: Medical records of Standardbred racehorses that had arthroscopic dissection of axial OC fragments of the proximal plantar aspect of P1 with electrocautery probes were reviewed. Horses were positioned in dorsal recumbency; a 1.5% glycine solution was used to maintain joint distension. The arthroscope portal was in the proximal plantar joint pouch and OC fragments were approached using either an ipsilateral or a contralateral triangulation technique. Dissection of the fibrous attachments was performed using loop and hook electrocautery probes. Follow-up was obtained by telephone questionnaire of owners or trainers and examination of race summary records. RESULTS: Thirty-three axial OC fragments were removed from 28 metatarsophalangeal joints (left, 14; right, 14). No major operative or postoperative complications occurred. Seven of 8 (79%) of horses that raced before surgery raced after surgery. Thirty-six percent (n=4) of horses that had not raced before surgery raced after surgery. CONCLUSION: Intra-articular electrosurgery is a safe, easy alternative to conventional excision of axial OC fragments of the proximal plantar aspect of P1. CLINICAL RELEVANCE: Arthroscopic excision using electrocautery probes is a valid alternate method for removal of axial OC fragments of the proximal plantar aspect of P1. In addition, the dorsal recumbency position facilitates removal of several fragments and multiple joint surgery.     

Osteochondrosis and osteochondral fragments in Standardbred trotters: prevalence and relationships

Reasons for performing study: Developmental orthopaedic diseases (DOD) such as osteochondrosis (OC)/osteochondrosis dissecans (OCD), palmar/plantar osteochondral fragments (POF), ununited palmar/plantar eminences (UPE) and dorsoproximal first phalanx fragments are well recognised in the horse. Aetiopathogeneses are controversial and molecular genetic screening of DNA has recently been employed for their elucidation. Precise phenotypic definition and knowledge of breed‐specific prevalence and interrelations are essential for the interpretation of following genomic studies in Standardbred trotters. Objectives: To assess the prevalence, trend of development and interrelation of DOD in tarsocrural, metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints in Standardbred trotters. Methods: The tarsocrural and MCP/MTP joints of 464 Norwegian Standardbred yearlings were radiographed and the prevalence and interrelation of osteochondral lesions calculated. Results: Osteochondral lesions were diagnosed in 50.7% of the horses. The prevalence of tarsocrural OC/OCD at the distal intermediate ridge of the tibia (DIT) and the lateral trochlear ridge of the talus (LTT) was 19.3%. The prevalence of OC/OCD in MCP joints was 3.6%, whereas those of POF and UPE in MCP/MTP joints were 23.1 and 3.9%, respectively. Interrelation was evident for 1) most equivalent lesions in joint homologues, 2) OCD DIT and OCD LTT and 3) POF and UPE. Lesions in hock and fetlock joints were generally not significantly associated. Conclusions: The prevalence of tarsocrural OC/OCD in Norwegian Standardbreds is apparently increasing, whereas that of other articular DOD appears stable. Association analyses verify bilateralism for most equivalent lesions and suggest aetiological resemblance also between other lesions. The absence of a significant association between tarsocrural OCD and POF implies that the lesions must be considered statistically different disorders. Potential relevance: The prevalence results emphasise that DOD should be considered in Standardbred breeding regimens (e.g. by sire selection subsequent to progeny testing). Also, improved phenotypic definitions will help elucidate the true causal genes in following genomic studies.     

Gas arthroscopy for removal of osteochondral fragments of the palmar/plantar aspect of the metacarpo/metatarsophalangeal joint in horses

Objective— To evaluate the use of carbon dioxide (CO₂) gas for joint distention during arthroscopy for removal of osteochondral (OC) fragments of the palmar/plantar aspect of the metacarpo (MCP)/metatarsophalangeal (MTP) joints in horses.
Study Design— Clinical study.
Animals— Horses (26) with OC fragment(s) of palmar/plantar aspect of 1 or 2 MCP/MTP joint(s).
Methods— OC fragments were removed using arthroscopic technique. Joint distention was maintained by isotonic Ringer's acetate at the beginning and at the end of the procedure but during fragment removal, CO₂ was used for joint distention. After surgery, fragment removal was confirmed by radiography. Horses were discharged the day after surgery, and outcome was determined by telephone contact 3–24 months later.
Results— CO₂ joint distention resulted in a sharp image without villi obscuring the operative field. Fragments were identified and completely removed in all horses except one where a 1 mm × 3 mm radiodense body was seen on postoperative radiographs. In 5 horses, bleeding from the arthroscopic or instrument portal precluded optimal visualization when the joint was distended by gas; however, repeatedly rinsing the tip of the arthroscope with Ringer's acetate solution delivered from the fluid ingress line easily restored joint visualization. No specific complications were observed postoperatively.
Conclusions— Joint distention by CO₂ permitted optimal visualization of the palmar/plantar aspect of the MCP/MTP joints, which facilitated fragment removal.
Clinical Relevance— Gas arthroscopy is a useful technique for removal of OC fragments of the palmar/plantar aspect of the MCP/MTP joints in horses.     

Patterns of scintigraphic uptake in the fetlock joint of Thoroughbred racehorses and the effect of increased radiopharmaceutical uptake in the distal metacarpal/tarsal condyle on performance

Reasons for performing study: The effect of palmar osteochondral disease lesions on performance of Thoroughbred (TB) racehorses is unclear. There is a need to describe patterns of radiopharmaceutical uptake (IRU) in fetlock joints of TB racehorses and to evaluate post scintigraphy performance. Hypotheses: IRU in the metacarpal (MC) and metatarsal (MT) condyles is more common than IRU in the parasagittal grooves and is associated with poorer post diagnosis performance than controls. Methods: Location of IRU within the fetlock region was identified and graded subjectively in TB racehorses. Performance variables were determined from race records for horses with moderate/marked MC/MT condylar IRU (cases), other horses undergoing scintigraphy (scintigraphy controls) and age/sex matched controls from the last race in which a case participated (controls). Statistical analyses included quantile regression, Fisher's exact test, Kaplan‐Meier survival curves, log‐rank test and Cox regression. Results: Metacarpal/MT condylar IRU was identified in 103/220 horses with only 3/220 having parasagittal IRU. Moderate/marked IRU was identified in the MC and MT condylar regions in 62 and 39 horses, respectively, with palmaromedial and plantarolateral IRU most common. Fore‐ and hindlimb cases had fewer starts, reduced earnings (P<0.001) and reduced earnings/start than controls respectively. Cases were more likely to return to racing later than controls following a rest period. Cases were older than scintigraphy controls. Conclusions: In TB racehorses presenting for lameness MC/MT condylar IRU is the most common abnormality identified within the fetlock joint. Racehorses with moderate/marked condylar IRU have a shortened racing career, are less successful than age/sex matched controls and are older than other racehorses presented for scintigraphy. Potential relevance: Overload of the MC/MT condyles is a common and significant problem in TB racehorses that is readily identified with scintigraphy. Scintigraphy of horses that are lame or performing poorly is less useful for screening for potential condylar fractures.