Favorable Clinical and Radiographic Results of Transtrochanteric Anterior Rotational Osteotomy for Collapsed Subchondral Insufficiency Fracture of the Femoral Head in Young Adults

Background: Subchondral insufficiency fracture of the femoral head (SIF) occurs infrequently in young adults. As the collapsed SIF lesion is usually located at the anterior portion of the femoral head, young adults with SIF are considered to be candidates for transtrochanteric anterior rotational osteotomy, similar to patients with osteonecrosis of the femoral head (ON). In the present study, we assessed the clinical and radiographic results of anterior rotational osteotomy for the treatment of SIF as compared with ON. Methods: We retrospectively reviewed 28 consecutive patients who underwent anterior rotational osteotomy for the treatment of unilateral SIF (7 patients) or unilateral ON (21 patients). The mean duration of follow-up was 3.7 years (range, 2.0 to 6.2 years). Clinical and radiographic assessments were performed with use of the Harris hip score (HHS), sequential radiographs, and single-photon emission computed tomography/computed tomography (SPECT/CT) with ^99mTc-hydroxymethylene diphosphonate performed 5 weeks after surgery. Results: The mean HHS (and standard deviation) in the SIF group improved significantly from 51.6 ± 11.7 preoperatively to 91.9 ± 7.1 at 1 year after surgery and to 96.9 ± 3.8 at the time of the latest follow-up (p = 0.0010 and 0.0002, respectively). Similarly, the mean HHS in the ON group improved significantly from 52.4 ± 13.7 preoperatively to 80.7 ± 10.0 at 1 year after surgery and to 88.2 ± 12.6 at the time of the latest follow-up (p < 0.0001 for both). The HHS was significantly higher in the SIF group than in the ON group at 1 year after surgery (p = 0.019), but there was no significant difference between the groups at the time of the latest follow-up (p = 0.10). A postoperative intact ratio (calculated as the intact area of the femoral head divided by the weight-bearing area of the acetabulum on an anteroposterior radiograph) of >80% was achieved in association with smaller femoral neck-shaft varus angles in the SIF group (10.0 ± 4.2) as compared with the ON group (15.3 ± 8.2). Postoperative progression of collapse at the anteriorly rotated subchondral lesion was observed in 5 patients (23.8%) in the ON group but no patients in the SIF group. SPECT/CT images showed that rate of increased tracer uptake at the collapsed lesions in the SIF group was significantly higher than that in the ON group (p < 0.0001). Conclusions: The present study suggested that the absence of progression of collapse and a sufficient postoperative intact ratio without the need for marked varus realignment may be associated with favorable results following anterior rotational osteotomy for the treatment of SIF in young adults. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.