RESTORATION OF FEMORAL OFFSET AND FUNCTION: RANDOMIZED STUDY COMPARING TOTAL HIP RESURFACING AND TOT

Abstract

Purpose: Femoral offset restoration is recognised as an important part of THA procedure to reduce the joint reactive force and improve stability. In SRA, femoral offset is often reduced due to the femoral component valgus position. The main objective of this study was to correlate the clinical function of SRA and THA patients with their different biomechanical hip reconstruction (femoral offset).

Methods: 156 patients aged 23 to 65 years old and suffering from advanced hip joint degeneration were randomly assigned to two treatment groups: the THA or SRA group. All surgeries were performed through a posterior approach. Standardized pre and post operative antero-posterior radiographs of the pelvis were made and clinical scores were assessed.

Results: Compared to the normal contra lateral side, the femoral offset increased on average 4.85mm (range -2.77 to 11.59mm, SD 3.31) for THA and decreased an average of 3.42mm (range −7.78 to 1.96, SD 2.12) for SRA (p=0.0001). In addition, offset restoration was within lees than 4 mm in 60.0% of the SRA group and 21.8% in the THA group (p=0.0001). There were no differences between the both groups in terms of clinical and subjective scores: the PMA and SF-36 scores were, respectively, in average 17.1 (SD 0.4) and 101 (SD 1.25) for THA and 17.0 (SD 0.4) and 101 (SD 1.14) for SRA. No relation was found between offset restoration and clinical scores for both groups.

Conclusions: In this study, surgeons were less precise reconstructing the femoral offset in the THA group compared to the SRA group. However, femoral offset was lower (reduced) in the SRA in comparison to THA. This significant decreased femoral offset in SRA, seems inherent to the preferential valgus positioning of the femoral component in that technique. The excellent clinical outcome reported with SRA does not suggest that restoring normal offset is as crucial for the success of SRA because no correlation was found between femoral offset and the clinical scores used.