RELATIONSHIP BETWEEN DEGENERATIVE JOINT DISEASE AND HIP-JOINT LAXITY BY USE OF DISTRACTION INDEX AND NORBERG ANGLE MEASUREMENT IN A GROUP OF CATS

Objective-To determine the relationship between degenerative joint dis ease (DJD) and passive laxity of the hip joint in a group of cats. Des ign-Prospective study. Animals-A select (nonrandomized) group of 78 ca ts. Procedure-Standard hip-extended radiographic views and compression and distraction views of the pelvis were obtained from cats during se dation. Radiographs were evaluated, using an Orthopedic Foundation for Animals (OFA)-like scoring system for dogs. Passive joint laxity was measured, using Norberg angle (NAI and distraction index (DI). Hip lax ity in cats with DJD was compared with hip laxity in cats without DJD. Results-Hip dysplasia (HD) was subjectively diagnosed radiographicall y in 25 of 78 (32%) cats using the OFA-like scoring system. Nineteen c ats had mild HD, 4 had moderate HD, and 2 had severe HD. Fifteen of th e 25 cats with HD had DJD. The NA ranged from 56 to 105. The mean NA i n cats with DJD was (84 degrees) significantly lower than in cats with out DJD (95 degrees). The DI ranged from 0.2 to 0.84. The mean DI for cats with DJD was (0.6) significantly higher than that for cats withou t DJD 10.49). Cats with a DI < 0.4 did not have DJD. Cats had an incre ased likelihood of having DJD with increased laxity in the coxofemoral joint, as measured by NA or DI. Clinical Implications-The mean NA for radiographically normal cats (92.4 degrees) was lower than that in ra diographically normal dogs (103 degrees). The overall mean DI for cats in this group (0.51) is similar to dogs of breeds with high joint lax ity, such as the Labrador Retriever (0.5). As in dogs, there is a rela tionship between DJD and laxity in the hip joint of cats.