Can native offset be restored in total hip arthroplasty? A contralateral-based evaluation from the FP-UCBM Hip Study...

Area of Science:

• Orthopedic surgery
• Biomechanics
• Radiographic analysis

Background:

• Accurate coronal-plane biomechanics restoration in total hip arthroplasty (THA) requires assessing global offset (GO) and leg-length discrepancy (LLD).
• The SGL index combines ΔGO and LLD for a comprehensive evaluation of THA coronal restoration.
• Previous methods often evaluated GO and LLD independently, potentially missing combined effects.

Purpose of the Study:

• To evaluate the SGL index for assessing coronal-plane restoration after THA.
• To determine the accuracy of SGL restoration within ±5 mm.
• To analyze the contribution of femoral versus acetabular components to GO restoration.

Main Methods:

• Retrospective analysis of 256 unilateral THA cases using standardized AP pelvic radiographs.
• Measurements included preoperative and postoperative femoral offset (FO), acetabular offset (AO), GO, LLD, and SGL.
• Accuracy defined as within ±5 mm, using the contralateral healthy hip as a reference.

Main Results:

• SGL restoration (≤5 mm) was achieved in 64.5% of hips.
• SGL-restored hips showed higher postoperative FO compared to non-restored hips (p=0.050).
• No significant difference in AO was observed between restored and non-restored groups; preoperative offsets were similar.

Conclusions:

• The SGL index is a valid parameter for evaluating coronal-plane restoration following THA.
• Femoral offset (FO) is the most sensitive single indicator for achieving global offset restoration in THA.
• Understanding the interplay of FO and AO is crucial for optimizing THA outcomes.