Diagnosis, prevention, and management of canine hip dysplasia: a review

Abstract

Canine hip dysplasia (CHD) is a polygenic and multifactorial developmental disorder characterized by coxofemoral (hip) joint laxity, degeneration, and osteoarthritis (OA). Current diagnostic techniques are largely subjective measures of joint conformation performed at different stages of development. Recently, measures on three-dimensional images generated from computed tomography scans predicted the development of OA associated with CHD. Continued refinement of similar imaging methods may improve diagnostic imaging techniques to identify dogs predisposed to degenerative hip joint changes. By current consensus, joint changes consistent with CHD are influenced by genetic predisposition as well as environmental and biomechanical factors; however, despite decades of work, the relative contributions of each to the development and extent of CHD signs remain elusive. Similarly, despite considerable effort to decipher the genetic underpinnings of CHD for selective breeding programs, relevant genetic loci remain equivocal. As such, prevention of CHD within domestic canine populations is marginally successful. Conservative management is often employed to manage signs of CHD, with lifelong maintenance of body mass as one of the most promising methods. Surgical intervention is often employed to prevent joint changes or restore joint function, but there are no gold standards for either goal. To date, all CHD phenotypes are considered as a single entity in spite of recognized differences in expression and response to environmental conditions and treatment. Identification of distinct CHD phenotypes and targeting evidence-based conservative and invasive treatments for each may significantly advance prevention and management of a prevalent, debilitating condition in canine companions.

Keywords: canine hip dysplasia; joint; orthopedics; osteoarthritis.

Figure 1

Anatomy of canine hip dysplasia. Notes: (A–C) Canine hip-extended radiographs, and corresponding images of the joints (D–F) from different individuals demonstrating mild (A and D), moderate (B and E), and severe (C and F) joint changes. Light photomicrographs of normal (G) and fibrillated (H, arrow) articular cartilage.

Figure 2

Schematic illustration of the Ortolani test. Notes: Image demonstrates the coxofemoral joint prior to distraction (A), while force is applied from the stifle toward the hip along the axis of the femur to displace the femoral head (B), during abduction of the femur to reduce the joint (C), and with the femoral head snapping back into place with an audible click, ie, the Ortolani sign (D). Arrows indicate the direction of the applied force. Adapted from Chalman JA, Butler HC. Coxofemoral joint laxity and the Ortolani sign. Journal of American Animal Hospital Association. 1985;21:671–676.

Figure 3

Representations of anatomical landmarks and evaluation mechanisms to assess canine hip dysplasia. Notes: Coxofemoral joint anatomical characteristics considered by the Orthopedic Foundation for Animals (A): craniolateral acetabular rim (1), cranial acetabular margin (2), femoral head (3), fovea capitis (4), acetabular notch (5), caudal acetabular margin (6), dorsal acetabular margin (7), junction of femoral head and neck (8), and trochanteric fossa (9). (B) British Veterinary Association/Kennel Club canine coxofemoral joint characteristics scored during evaluation., Schematic superimposed on a hip-extended radiograph demonstrating the Norberg angle (C, arrow). Illustration of the Pennsylvania Hip Improvement Program (distraction index, the distance between the centers of the femoral head and acetabulum during distraction (D) divided by the radius (r) of the femoral head (d). Depiction of the dorsolateral subluxation score (E) calculated as 100 multiplied by the percentage of femoral head medial to the cranial acetabular rim (d) divided by the femoral head diameter (θ), d/θ ×100%). Abbreviations: AF, acetabular fossa; An, acetabular notch; CaAE, caudal acetabular edge; CrAE, cranial acetabular edge; CrEAR, cranial effective acetabular rim; DAE, dorsal acetabular edge; Fh, femoral head; Fv, foveal defect.

Figure 4

Measurements and three-dimensional models for evaluating the dysplastic canine hip. Notes: (A) Volume rendered model of the canine pelvis generated from two-dimensional computed tomography images (B and C). The blue line in (A) indicates the level of the cross-sectional image in (B) and (C). (B) and (C) Representative measures performed on two-dimensional computed tomographic images of the canine coxofemoral joint. Acetabular index is the ratio between the width and the depth of the acetabulum; d/w ×100. For further information see Lopez et al and Andronescu et al. For details on these measures see Lopez et al. Abbreviations: AAA, acetabular anteversion angle; AI, acetabular index; CEA, center edge angle; CPC, percentage of femoral head coverage; DASA, dorsal acetabular sector angle (dorsal coverage of the femoral head); HASA, horizontal acetabular sector angle (total acetabular coverage of the femoral head); HTEA, horizontal toit externe angle (orientation of the acetabulum); VASA, ventral acetabular sector angle (ventral coverage of the femoral head).

Figure 5

Radiograph illustrating a bilateral total hip replacement. Notes: Blue line indicates femoral implant, pink line indicates acetabular implant. Image courtesy of Dr Jeffrey D Brourman.