Impact of Prosthetic Angle Variations in Combined Anteversion Technique on Surgical Failure Rates in Developmental Dysplasia of the Hip: A 12-Year Follow-Up Study.

OBJECTIVES

The combined anteversion technique was introduced to guide prosthesis orientation in patients with developmental dysplasia of the hip and has achieved favorable short-term results in a previously published series. However, excessive variations in implant orientation may increase the risk of accelerated polyethylene wear and lead to revision THA. This study aimed to report whether the variation in implant orientation caused by the combined anteversion technique would result in an increased surgical failure rate and the mid- to long-term clinical outcome in total hip arthroplasty for patients with hip dysplasia.

MATERIALS AND METHODS

This retrospective study reviewed patients with hip dysplasia who underwent total hip arthroplasty with the combined anteversion technique between 2007 and 2012 at our center. The surgical protocol prioritized the combined anteversion principle, requiring maintenance of the combined anteversion within the 25°-50° range while permitting physiological variation in individual femoral or acetabular component positioning. In total, 55 patients (80 hips) were included, with an average follow-up period of 12.7 years (range, 11 to 16). Ceramic fragmentation, periprosthetic radiolucencies, and osteolysis around the cup and stem were evaluated based on the immediate postoperative pelvic anteroposterior radiographs and the last follow-up. Femoral, acetabular, and combined anteversions pre-and postoperatively were measured using CT-based models. The Harris hip score at the latest follow-up was used for comparison with the score before surgery.

RESULTS

The average Harris hip score increased from 28.3 ± 10.1 preoperatively to 91.2 ± 6.7 (p < 0.01) at the last follow-up. The mean femoral, acetabular, and combined anteversions were 25.6° ± 11.1° and 23.7° ± 10.6°, 23.2° ± 7.4° and 19.8° ± 8.3°, and 48.7° ± 12.9° and 43.1° ± 6.8° preoperatively and postoperatively, respectively. By the last follow-up, one patient developed periprosthetic osteolysis 11 years after primary surgery without obvious periprosthetic loosening and migration of the femoral head rotation center. Two patients experienced prosthesis dislocation, one of whom received a revision 4 years after primary surgery, and the other underwent manual reduction under anesthesia 8 years after primary surgery. Two patients underwent revision and internal fixation due to prosthesis loosening caused by a periprosthetic fracture 10 years and 12 years after primary surgery.

CONCLUSION

The combined anteversion technique in total hip arthroplasty for patients with hip dysplasia yielded reliable mid-to-long-term results. This technique's changes in prosthesis angle did not significantly increase the surgical failure rate.