The round femoral stem provides a similar clinical outcome but more serious proximal stress shielding compared to the rectangular stem in cementless total hip arthroplasty without a shortening osteotomy in patients with Crowe type 2 or 3 hip dysplasia

Abstract

Objectives This study aims to compare clinical and radiological follow-up results of a rectangular (SL-Plus®) or a round (Synergy®) femoral component in patients with Crowe type 2 or 3 hip dysplasia operated with total hip arthroplasty (THA) without a shortening osteotomy. Patients and methods Between January 2012 and December 2017, a total of 34 hips of 30 female patients (mean age: 42.9±11.6 years; range, 24 to 66 years) were retrospectively analyzed. All patients were evaluated using the Harris Hip Score (HHS) and Visual Analog Scale (VAS) for pain pre- and postoperatively. Intra- and postoperative complications were noted. Evaluation criteria included leg length discrepancy, stem subsidence, bone atrophy or hypertrophy around the stem according to Gruen zones, operative time, and intraoperative blood loss. Correlation analysis of radiological, clinical findings, and stem size was performed. Results The mean follow-up was 61.3±27.2 months. The mean postoperative HHS was 89.3±6.2 vs. 93.1±9.1, and the mean VAS score 1±0.6 vs. 1±0.8 in round and rectangular stem groups at the final follow-up. No significant differences were detected between the groups in any of the evaluated parameters, except for a more severe degree of stress shielding observed in the round stem group. Round stem size was positively correlated with a more severe stress shielding (r=0.55, p=0.020). No patient had to be revised during the follow-up period. The overall complication rate was 9%. Conclusion Successful and comparable results can be obtained with cementless THA in patients with high riding dysplastic hips implanting either of the femoral components, a rectangular or a round stem. Although the round stem was associated with more common proximal stress shielding, this was not associated with worse clinical outcomes.