Abstract
Introduction: Secondary hip osteoarthritis (OA) potentially occurs as a consequence of the combined effects of acetabular dysplasia and age-related changes in lumbar alignment. The purpose of this study was to examine the effects of age-related spinal changes on the onset of secondary hip OA from the viewpoint of “total alignment” including both spinal and pelvic morphologic angles.
Methods: Seventy-three patients with unilateral end-stage secondary hip OA and accompanying acetabular dysplasia underwent total hip arthroplasty. The study subjects were classified into a “middle-aged” group composed of 25 patients aged less than 60 years, and an “elderly” group composed of 48 patients aged 60 years or greater, respectively. Radiographs were taken in the full spine lateral view with the patients standing with fingers crossed in front of the pelvis. Sagittal spinal alignment was measured according to the methods proposed by Jackson et al and Wiltse et al.
Results: The results indicated that the C7 plumb line shifted anteriorly and the pelvis rotated posteriorly in the elderly group, while the PR-S1 values were smaller in the elderly group.
Conclusion: Middle-aged patients appear to possess a compensatory mechanism by maintaining sagittal lumbo-pelvic alignment when compensating for acetabular dysplasia. Conversely, the onset of secondary OA in elderly patients is likely a consequence of degenerative changes in lumbar alignment attributable to aging.
