33rd Annual Scientific Meeting proceedings

Introduction
Few case reports describe equine coxarthrosis. The aim of this large case series was to evaluate diagnostic findings, outcome and to provide a score facilitating radiographic assessment.

Material and Methods
Anamnesis, clinical signs, ultrasonographic, radiographic and intraarticular analgesia findings, treatments, outcome and necropsy results of horses with coxarthrosis presented between 2002 and 2021 were recorded. Radiographic findings were categorized to develop a radiographic score which was applied by two blinded examiners. Inter-observer reliability was determined using quadratic weighted Cohen’s kappa, the association between radiographic and ultrasound findings investigated by means of Spearman correlation coefficient. Significance was set as p<0.05.

Results
The study included 24 chronically lame horses (median age 14 years). Frequent clinical signs included ipsilateral stride lengthening (12/18) and locomotion on three tracks (14/19). Both imaging modalities enabled evaluation of periarticular osteophytes (correlation coefficient r=0.66; p=0.0038). Additionally, radiography allowed detection of irregular joint spaces, subchondral bone opacity changes or flattening/conification of the femoral head. Cohen’s kappa was 0.844 (p<0.001). If treated, mostly intraarticular corticosteroids were administered (16/18). Five were euthanized. Four of 6 horses presented for control examinations were also euthanized due to persistent lameness. Commonly, the ligamentum capitis ossis femoris was found ruptured during necropsy.

Discussion
Due to typical clinical signs, such as ipsilateral stride lengthening, the clinical examination may already indicate coxarthrosis. Standardized evaluation of ventro-dorsal radiographs using the new score enables a definitive and detailed diagnosis. Joint instability, indicated by necropsy finings, may explain poor prognosis and resistance to medical therapy of the disorder.