Abstract
Introduction
Total hip arthroplasty (THA) for a highly dislocated hip can be problematic and technically challenging. Our previous study on cemented THA with subtrochanteric femoral shortening osteotomy revealed a high incidence (20%) of non-union. Therefore, in 2008, we introduced reverse hybrid THA using S-ROM stem for the treatment of a highly dislocated hip. The purpose of this study was to assess the short-term clinical outcomes of this new method.
Patients and methods
Between 2008 and 2014, 13 consecutive reverse hybrid THAs were performed on nine female patients with highly dislocated hips. The average age at the time of operation was 66 years (range, 55–85 years). The acetabular component was fixed in the true acetabulum with bone cement. Transverse osteotomy was performed below the lesser trochanter to shorten the femur and to prevent over-lengthening. The proximal sleeve of the S-ROM stem was then fixed within the proximal fragment, and the distal fin provided rotational stability of the distal fragment. Thus, the two fragments were fixed to each other with the S-ROM stem, and the resected segment was longitudinally cut for grafting at the junction. The postoperative follow-up period was an average of 4 years (range, 1–7 years), and no patients were lost. Preoperative and final Japanese Orthopaedic Association (JOA) hip score, operation time, bleeding amount, intraoperative and postoperative complications, bone healing at the osteotomy site, implant loosening, and revision surgery were retrospectively investigated.
Results
The mean JOA hip score improved from 56 points preoperatively to 82 points postoperatively. The operation time and amount of bleeding were an average of 208 min and 643 g, respectively. The mean length of femoral resection was 4 cm (range, 2–6 cm), and the tip of the greater trochanter migrated an average distance of 7 cm (range, 5–9 cm) distally. The calculated limb lengthening was an average of 3 cm (range, 2–4 cm). Intraoperative fracture was seen in two patients, but no repeat operation was required. Two patients experienced postoperative dislocation in their hips, but additional surgery was not necessary. Postoperative nerve palsy did not occur in any patient, and all the osteotomy sites showed complete bone union. There was no implant loosening seen in any patient, and there was also no need for revision surgery.
Discussion and conclusions
To achieve satisfactory outcomes with this method, resection of necessary and sufficient length of femur and accomplishment of adequate fixation between the proximal and distal fragments are necessary. In this study, dislocation occurred in two patients, and no nerve palsy was seen. Larger femoral heads may be recommended to eradicate dislocations. In cases where metaphysis of the femur is hypoplastic or the medullary canal is wide, reaming and stem insertion should be carefully performed. In this series, no additional surgery was required for the intra- and post-operative complications, and the osteotomy sites achieved bone union in all patients. Therefore, we recommend the use of this method, although longer follow-up periods are necessary.
