In a multi-institutional, 10-year study1 of almost half a million dogs in the United States, hip dysplasia was the most commonly identified hip joint condition, comprising 67.4% of all conditions described for that joint. Hip dysplasia is associated with joint pain and loss of joint function.
Sensory innervation of the hip joint in dogs consists of the cranial gluteal, sciatic, femoral, and obturator nerves,2–4 although the contribution of the obturator nerve may be inconsistent.2,4,5 It has been reported6 that the craniolateral area of the hip joint capsule is innervated by articular branches of the cranial gluteal nerve, the caudolateral area is innervated by articular branches of the sciatic nerve, and the ventral area is innervated by articular branches of the femoral nerve and articular branches of the obturator nerve. Articular branches innervate distinct areas of the joint capsule directly or indirectly via periosteal branches from the periarticular muscles covering the acetabulum.7–9 The abundance of sensory nerve endings in the hip joint capsule provides the possibility that interruption of these fibers might eliminate pain in the joint.10
Denervation of the hip joint capsule has been described as a treatment to alleviate pain associated with hip dysplasia and osteoarthritis in dogs.9–17 This technique is based on surgical removal of the periosteum in a semicircular manner, beginning at the craniodorsal margin (as far caudally as possible) of the acetabulum and progressing to the cranioventral margin (ventral aspect of the body of the ilium), thereby transecting the sensory nerve fibers (articular branches) innervating the hip joint.8,12,16,17 Originally, periostectomy was achieved through a limited craniolateral open approach10–14; however, percutaneous techniques involving the use of Steinman pins have also been described.18,a
Denervation has resulted in clinical improvement in > 90% of treated dogs, as determined on the basis of owner assessment and results of observational gait analysis in various studies.12–14,16,19 The quality of evidence yielded by most of these studies is diminished by the retrospective nature of the studies, lack of control subjects, small numbers of dogs in some studies, and subjective nature of the assessments. An additional limitation is that it is unclear whether the reported change in gait following denervation was a beneficial effect of the denervation procedure or a reflection of resolving lameness commonly seen in young dogs with hip dysplasia.
To our knowledge, the effect of denervation of the hip joint on objective gait characteristics has not been described for dogs. Dogs with hip dysplasia of various degrees of severity have been evaluated before and after treatment, but not before and after the onset of lameness. Gait characteristics are difficult to assess in dogs with naturally occurring disease, and a standardized method for induction of hip joint pain could help to determine the effect of denervation on gait and the efficacy of denervation in the treatment of joint pain.
In a recent study20 of healthy dogs, investigators described the development of a novel method for inducing acute synovitis of the hip joint by intra-articular injection of sodium urate crystals. Observational and instrumented gait variables (temporospatial, kinetic, and kinematic) were recorded before and 4, 8, and 24 hours after induction of synovitis. Gait changes were similar to those reported for dogs with hip dysplasia. The inflammatory response after intra-articular injection of sodium urate crystals caused a detectable clinical effect and lameness after 1 to 2 hours, which reached maximal intensity at 4 hours and subsided by 24 hours after injection. That study20 highlighted the objectivity of instrumented gait analysis because it allowed the comparison of gait characteristics at various points.
The objective of the study reported here was to use the aforementioned synovitis induction method and assessment modalities to assess effects on gait characteristics of dogs. The hypotheses tested were that selective percutaneous denervation of the hip joint (defined as minimally invasive denervation) would not result in gait abnormalities and that selective denervation of the hip joint of dogs would abolish joint pain.
This manuscript represents a portion of a thesis submitted by Dr. Hassan to the Department of Surgery, Anesthesiology and Radiology at Cairo University as partial fulfillment of the requirements for a PhD degree.
Supported by the Egyptian Government as part of the Joint Supervision Program between Cairo University and Purdue University.
The authors thank Kris Kazmierczak and Dr. Darryl Dickerson for technical assistance and Drs. Ahmed S. Ahmed and Ashraf A. Shamaa for academic support of the Joint Supervision Program.
Coefficient of variation
Peak vertical force
Lincoln JD, Martinez SA, McCormick DJ, et al. Partial sensory denervation. A treatment for the clinical signs of coxofemoral osteoarthritis (abstr), in Proceedings. 34th Ann Conf Vet Orthop Soc 2007;54.
3/4-inch black LP SAT dots, Velcro USA Inc, Manchester, NH.
Animal Walkway System, Tekscan Inc, South Boston, Mass.
GL2- digital camcorder, Canon Inc, Melville, NY.
Walkway System Software, version 7.0, Tekscan Inc, South Boston, Mass.
MaxTRAQ, Innovision Systems Inc, Columbiaville, Mich.
Microsoft Office Excel 2007, Microsoft Corp, Redmond, Wash.
MATLAB, version 126.96.36.1999 (R2010a), MathWork Inc, Natick, Mass.
Torbutrol, Zoetis Inc, Kalamazoo, Mich.
Propofol, Abbott Laboratories, Abbott Park, Ill.
Isoflurane, Piramal Healthcare Ltd, Andhra Pradesh, India.
Cefazolin, Sandoz Inc, Princeton, NJ.
Positioning board assembly (10-010), BioMedtrix, Boontown, NJ.
Monocryl, Ethicon Inc, West Somerville, NJ.
Hydromorphone HCL 2 mg/mL, Baxter Healthcare Corp, Deerfield, Ill.
Rimadyl 100-mg caplets, Zoetis Inc, Orion Corp, Exton, Pa.
Tramadol, Amneal Pharmaceuticals LLC, Bridgewater, NJ.
Dexdomitor, Orion Corp, Espoo, Finland.
Antisedan, Orion Corp, Espoo, Finland.
Beuthanasia-D Special, Intervet/Schering-Plough Animal Health Corp, Kenilworth, NJ.
SPSS, version 21.0, IBM Corp, Armonk, NY.
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