The Hemipelvic Muscle Mass in Small to Medium Size Dogs and its Association with Canine Hip Dysplasia: A Cadaveric Study

Abstract

Canine hip dysplasia (CHD) is among the most common orthopedic diseases in dogs. In large breed dogs, increase in pelvic muscle mass is associated with decreased incidence of CHD. The aim of this study was to characterize individual hip joint muscle contributions to the pelvic muscle mass, and evaluate the suitability of the parameters previously shown to identify large-breed dogs predisposed to CHD to small to medium sized dogs. Fifteen cadavers of mixed-breed dog (age range, 1-4 years; body weight range 6-28 kg) were used. Twenty-four muscles, directly acting on the hip joint were identified during dissection. Each muscle was dissected from surrounding tissues and weighed. These muscles were divided into five groups based on their innervation. The hip joint and surrounding bone were visually examined for cartilage damage and articular osterophyte formation. The hemipelvic muscle weight, as a percentage of body weight, was 4.85%±0.81. The contributions of the muscles innervated by the sciatic, femoral, obturator and the gluteal nerves were 35.73%±1.21, 28.45%±1.49, 21.28%±0.73 and 14.54%±1.17 of the entire pelvic muscle mass, respectively. Based on the previously published criteria for large breed dogs, as many as 67% of dogs in this study would have been expected to be predisposed to CHD; however, all the hip joints of these dogs were free of pathology. It was concluded that hemipelvic muscle mass relationship parameters applied to large breed dogs predisposed to CHD might be unsuitable for small to medium size dogs.

Keywords: Hip joint; Musculature; Degenerative Joint Disease.