ORIGINAL ARTICLE The Innervation of Canine Hip Joint Capsule: An Anatomic Study C. H. Huang 1 , S. M. Hou 2 and L. S. Yeh 1 * Addresses of authors: 1 Institute of Veterinary Clinical Sciences, School of Veterinary Medicine, National Taiwan University, No. 1, Sec 4, Roosevelt Rd., Taipei 106, Taiwan; 2 Department of Orthopedic Surgery, Shin Kong Wu Ho-Su Memorial Hospital, No.95, Wenchang Rd., Shilin Dist, Taipei 111, Taiwan *Correspondence: Tel.: +886 913800907; fax: +886 2 27323817; e-mail: lsyeh@ntu.edu.tw With 5 figures and 1 table Received September 2011; accepted for publication December 2012 doi: 10.1111/ahe.12033 Summary To clarify the contributions of the nerves supplying the canine hip joint capsule for clinical application, cadaver study of six healthy mongrel dogs was performed. The pelvises and hindlimbs of cadavers were dissected and fixed in formaldehyde. Innervation of the joint capsule was investigated with the aid of an operative microscope. As a result, the canine hip joint capsule receives mul- tiple innervations from articular branches of four nerves. They are articular nerve fibres of femoral, obturator, cranial gluteal and sciatic nerves from the cranioventral, caudoventral, craniolateral and dorsolateral directions of the joint, respectively. No branch originating from the caudal gluteal nerve was observed innervating the hip joint capsule. Our data provides useful informa- tion for research on the canine hip joint, including pain analysis with hip disorders and surgical nerve blockade to relieve pain. Introduction Osteoarthritis is a common long-term disorder leading to pain and dysfunction in geriatric dogs (Beale, 2005). The pain associated with osteoarthritis may be due to the chemical stimuli of inflammatory reactions including prostaglandin mediators, leukotrienes, and substance P and due to mechanical stimuli (Johnston, 1997). Occa- sionally, it is the pain, instead of structural deformation, that precludes joints from being used efficiently. Surgical procedures including arthrodesis, arthroplasty, and joint replacement may provide relief of pain (Zimmermann, 1989; Beale, 2005). However, they are either expensive, functionally unfavourable, or with increased risk due to prolonged anaesthesia, which renders elderly dogs to be unfavourable candidates for these surgical treatments. In addition to the aforementioned procedures, solely reliev- ing or blocking the sensation of pain may restore certain degrees of joint function and improve the quality of life (Johnston, 1997; Renberg, 2005). In humans with advanced osteoarthritis, denervation of hip and wrist joints has been established for decades as one of the palli- ative treatment options (Obletz et al., 1949; Sander and Hall, 1962). Denervation of canine hip joint capsule was also attempted in dogs with hip dysplasia and arthrosis (Kawaguchi et al., 2001). To perform accurate denerva- tion without the risk of iatrogenic injuries to functional nerve trunks, precise anatomic knowledge of canine hip joint innervation is essential. Numerous investigations of hip joint structures, hip pain mechanisms and their therapeutic implications have been carried out in humans and animals. The distribu- tions of nerves to the human hip joint and a number of hip joint pain patterns have been described (Gardner, 1948; Wertheimer, 1952; Hodges et al., 1987; Ferreres et al., 2002; Kinzel et al., 2002). These pain patterns are the reflex manifestations of sensory nerve irritations to the hip joints, which directly correspond to the anatomic distribution of articular nerves (Wertheimer, 1952; Hod- ges et al., 1987; Kinzel et al., 2002). Groin and thigh pain are believed arising from articular branches of the obtura- tor nerve, with trochanteric and gluteal pain mainly from articular branches of the femoral nerve and sciatic nerve, respectively (Sander and Hall, 1962; Ferreres et al., 2002). No literature has addressed the relationships between innervation and topographic distribution of canine hip pain. Even anatomic data of canine hip joint innervation is scarce and with various conflicting findings (Kitchell © 2013 Blackwell Verlag GmbH Anat. Histol. Embryol. 1 Anatomia, Histologia, Embryologia