[Long-term effectiveness of total hip arthroplasty for Crowe type Ⅳ developmental dysplasia of the hip].

Objective: To investigate the long-term effectiveness of primary total hip arthroplasty (THA) in treatment of Crowe type Ⅳ developmental dysplasia of the hip (DDH).

Methods: A clinical data of Crowe type Ⅳ DDH patients treated with primary THA between January 2002 and August 2008 and followed up more than 13 years was retrospectively analyzed. Forty-two patients (45 hips) met the selection criteria and were enrolled in this study. There were 13 males and 29 females with an average age of 43.5 years (range, 18-65 years). There were 39 patients of unilateral hip and 3 of bilateral hips. The preoperative Harris score was 38.3±10.7 and leg length discrepancy of the patients treated with unilateral THA was (50.52±24.51) mm. During operation, 19 hips underwent subtrochanteric shortening osteotomy, with an average length of 25 mm (range, 15-35 mm). The Harris score, subjective satisfaction, prosthesis survival rate, complications, and related imaging indicators were summarized.

Results: All patients were followed up 13.0-19.6 years (mean, 15.0 years). The complications included 1 hip of femoral nerve palsy, 2 hips of dislocation, 1 hip of periprosthetic fracture, 1 hip of periprosthetic joint infection. At last follow-up, the Harris score was 82.1±9.3, which significantly improved when compared with preoperative one ( t =-21.885, P =0.000). The subjective satisfaction was evaluated as very dissatisfactory in 3 hips, dissatisfactory in 1 hip, generally in 4 hips, satisfactory in 17 hips, and very satisfactory in 20 hips. X-ray films showed that the height of the greater trochanter of affected side was 3.01-51.60 mm (mean, 23.22 mm); the descending distance of greater trochanter was 3.95-98.06 mm (mean, 48.20 mm); the affected limb lengthened 3.95-61.63 mm (mean, 34.92 mm); the leg length discrepancy of patients treated with unilateral THA was (12.61±8.56) mm, which was significantly shorter than that before operation ( t =11.721, P =0.000). The vertical distance between the center of rotation of the affected side and the teardrop line was (14.65±6.16) mm, and the difference was not significant when compared with (15.60±4.99) mm of the healthy side ( t =-0.644, P =0.525); the horizontal distance was (22.21±5.14) mm, and the difference was significant when compared with (34.48±5.63) mm of the healthy side ( t =-12.973, P =0.000). Except for the non-union of 1 hip subtrochanteric shortening osteotomy, the other subtrochanteric osteotomies healed well. During follow-up, all the femoral stems obtained bone ingrowth fixation without radiolucent line or radiopaque line. With any reoperation and aseptic loosening as the endpoint, the prosthetic survival rates were 88.64% [95% CI (63.73%, 96.82%)] and 89.19% [95% CI (65.61%, 96.94%)], respectively.

Conclusion: For Crowe type Ⅳ DDH patients, primary THA combined with subtrochanteric shortening osteotomy if necessary, can obtain satisfactory long-term effectiveness and prosthetic survival rate.