[Selectively upward placement of acetabular implants in patients with anatomically abnormal acetabulum during total hip arthroplasty].

OBJECTIVE

To investigate the method and effectiveness of selectively upward placement of acetabular implants in patients with anatomically abnormal acetabulum during total hip arthroplasty (THA).

METHODS

Twenty-six cases (26 hips) of anatomically abnormal acetabulum received THA between January 2005 and December 2010, including 22 cases of developmental dysplasia of the hip, 3 cases of osteonecrosis of the femoral head, and 1 case of post-traumatic arthritis. There were 5 males and 21 females with an average age of 52.3 years (range, 35-67 years). The left hip was involved in 11 cases and the right hip in 15 cases. The preoperative Harris score was 45.85 +/- 10.04. The anteroposterior X-ray films and CT scan of the pelvis, anteroposterior and lateral X-ray films of the femur, and TraumaCad analysis were performed routinely before operation. The principles of acetabular implants were that more than 70% of the bone-implant interface was covered, and the upward distance of acetabular implant was less than 15 mm.

RESULTS

Acetabular implants were placed within 5 mm from the anatomical rotation center in 11 cases. The upward distance of acetabular implant was 5-10 mm in 8 cases and was 10-15 mm in 7 cases. No bone fracture or nerve injury was observed intraoperatively. All incisions healed by first intention, and no infection or lower limb deep venous thrombosis occurred. One case had dislocation at 3 days after operation, and was cured after reduction and conservative treatment. The follow-up time ranged from 15 to 71 months (mean, 34 months). The Harris score was 91.42 +/- 3.59, showing significant difference when compared with preoperative score (t = 20.099, P = 0.000). The Harris scores were 92.09 +/- 4.04 in patients having less than 5 mm upward distance, 91.25 +/- 2.82 in patients having 5-10 mm upward distance, and 90.57 +/- 3.95 in patients having 10-15 mm upward distance, showing no significant difference (F = 0.377, P = 0.690). No loosening or subsidence of the implant was observed by X-ray film during the follow-up.

CONCLUSION

The acetabular implants should be placed as close to anatomical rotation center as possible according to the principle. However, appropriate upward distance of the acetabular implants (< or = 15 mm) could be acceptable to meet 70% coverage of bone-implant interface and the implant stability. A satisfactory mid-term effectiveness can be obtained, but long-term effectiveness should be further investigated.