Residual hip dysplasia as a risk factor for osteoarthritis in 45 years follow-up of late-detected hip dislocation

Abstract

Purpose: The aim of the study was to assess the role of residual hip dysplasia as a risk factor for osteoarthritis (OA) in developmental dysplasia of the hip (DDH).

Methods: Fifty-one patients (60 hips) with late-detected DDH were studied. Reduction had been performed at a mean age of 19 months (range 4-65 months). On radiographs at age 8-10 years, at skeletal maturity, and at long-term follow-up, femoral head coverage was assessed using the migration percentage (MP) and centre-edge (CE) angle. OA was diagnosed if the minimum joint space width of the upper part of the joint was <2.0 mm.

Results: The mean age at the last follow-up was 45 years (range 43-49 years) in patients who had not undergone total hip replacement (THR). Ten patients had developed OA and eight of them had undergone THR at a mean age of 40 years (range 32-47 years). There was a clear association between OA and residual hip dysplasia. At the last follow-up, 37 hips had normal CE angles (20° or higher) and OA had developed in only two of them (5%; 95% confidence interval [CI] 1-18%). Hip dysplasia without subluxation (CE angle 10-19°) was seen in 18 hips, of which 14 hips had good outcome and four had OA (22%; 95% CI 6-48%). Subluxation occurred in five hips, of which one had a good long-term outcome and four had OA (80%; 95% CI 28-99%). In patients without late reconstructive surgery, MP increased from the age of 10 years to skeletal maturity; thereafter, no significant change occurred. The CE angle did not change significantly between the age of 10 years and the last follow-up.

Conclusion: Hip dysplasia without subluxation has a relatively good long-term prognosis. Subluxation is a risk factor for osteoarthritis. Thus, children with MP above 33% and CE angle under 10° should be evaluated for reconstructive surgery in order to improve the long-term outcome.

Keywords: Developmental hip dislocation; Long-term follow-up; Osteoarthritis of the hip; Residual hip dysplasia.

Fig. 1

Flowchart of 60 hips, showing long-term outcome related to treatment and radiographic measurements. HD residual hip dysplasia, OA osteoarthritis

Fig. 2

Radiographs of a girl with dislocation of her left hip. a Radiograph at the time of diagnosis at the age of 14 months. b Radiograph at the age of 9 years, showing acetabular dysplasia of the left hip with centre-edge (CE) angle 16° and migration percentage (MP) 25%. c Radiograph at the last follow-up at patient age 45 years, showing no osteoarthrosis in the left hip (CE angle 15° and MP 33%)

Fig. 3

Radiographs of a girl with dislocation of her left hip. a Radiograph at the time of diagnosis at the age of 18 months. b Radiograph at skeletal maturity at the age of 15 years, showing subluxation of the left hip, with CE angle 8° and MP 38%. c Radiograph at the last follow-up at patient age 45 years, showing osteoarthrosis in the left subluxated hip (CE angle −1° and MP 45%)