RADIOGRAPHIC EVALUATION OF COXOFEMORAL JOINT LAXITY IN DOGS PART I : NEW STRESS - RADIOGRAPHIC POSITIONING TECHNIQUES

Abstract

Two new stress-radiographic positioning techniques, namely 60O and 90O stress techniques, were introduced for quantifying hip joint laxity in dogs. The comparative characteristics and efficiency of these new techniques with angled hindlimbs were evaluated relative to the standard hip-extended radiographic technique. Forty, healthy, mongrel dogs with normal hip joint conformation were anesthetized and placed in dorsal recumbency before 3 radiographs of the standard, 60O, and 90O stress techniques were taken. For the 60O stress technique, hindlimbs were extended in parallel to each other at 60O angled to the table top and stifles were slightly rotated inward; femoral heads were manually pushed in a craniodorsal direction during exposure. For the 90O stress technique, femurs were positioned perpendicular to the table top; stifles were 90O flexed
and adducted and femoral heads were manually pushed in a craniodorsal direction during exposure. The subluxation index (SI) and dorsolateral subluxation score (DLS score) were calculated from 3 radiographic views for both hip joints to quantitate the relative degree of joint laxity. Results of the study indicated that the 60O (SI = 0.20 ± 0.045; DLS score = 62.5 ± 7.96%) and 90O (SI = 0.23 ± 0.044; DLS score = 61.2 ± 9.47%) stress-radiographs yielded significantly (p < 0.001) higher degree of hip joint laxity than the standard technique (SI = 0.17 ± 0.035; DLS score = 66.9 ± 8.09%). The 90O
stress technique is the most sensitive technique for measurement of the hip joint laxity as the SI values of the 90O stress technique were significantly (p < 0.001) higher than those of the 60O technique. The findings suggested that the 60O and 90O stress-radiographic positioning techniques, oriented similarly to those of a standing dog are more practical and efficient than the standard hip-extended technique for demonstrating maximal coxofemoral joint laxity in dogs with normal hip joint conformation. Both new techniques may prove useful in studies of hip joint laxity or subluxation related to canine hip dysplasia in more susceptible dogs.