Does Computed Tomography-Based Navigation Contribute to Achieving the Target of Intact Ratio in Surgery for Osteonecrosis of the Femoral Head? A Mean 9-Year Retrospective Study.

Abstract

This study evaluated postoperative radiological outcomes of transtrochanteric osteotomy using a computed tomography (CT)-based navigation system in patients who have osteonecrosis of the femoral head. This study included 16 patients who had a mean age of 28 ± 10 years and a mean follow-up of nine ± 5 years. There were four, five, and seven patients who underwent transtrochanteric anterior rotational osteotomy, transtrochanteric posterior rotational osteotomy, and curved varus osteotomy with a CT-based navigation system to achieve an intact ratio of ≥ 34%, respectively. According to the Japanese Investigation Committee classification, 14 and two hips were stage 3A and 3B, whereas 12 and four hips were type C1 and C2, respectively. There were two types of cumulative survival rates evaluated: one based on progression to collapse and the other based on conversion to total hip arthroplasty (THA) as the end point. The intact ratio, tip-to-apex distance, femoral offset, leg length, and neck-shaft angle were calculated via radiography and compared between the THA and non-THA groups according to whether conversion to THA was required. Collapse occurred in two cases, whereas four cases required THA. The cumulative survival rate among those who experienced collapse and required THA was 88 and 75%, respectively. The reasons for conversion to THA in the four cases were collapse (one case), deep infection (one case), and failures at the osteotomy site (two cases). All patients had a postoperative intact ratio of ≥ 34% (mean value, 49 ± 10%). No differences in the postoperative intact ratio were found between the groups. The tip-to-apex distance was greater in the THA group (39 ± 8 mm) than in the non-THA group (28 ± 10 mm; P = 0.04). Transtrochanteric osteotomy using a CT-based navigation system achieved a postoperative intact ratio of ≥ 34%. Further investigation may be necessary to reduce osteotomy site complications.