AB165. SOH26AB_0415. Reproducibility of the femoral neck cut using a simple ruler technique in uncemented total hip arthroplasty

Background: Restoring limb-length equality remains a critical goal of total hip arthroplasty (THA); even moderate discrepancies can impair gait, cause discomfort, and prompt litigation. Errors in femoral neck osteotomy contribute to leg-length discrepancy (LLD). We aimed to investigate whether a simple ruler technique using the proximal flare of the lesser trochanter as a reference can reliably reproduce the templated neck cut and achieve accurate limb lengths.

Methods: In this prospective study, 56 consecutive patients (mean age, 59 years) underwent uncemented THA via a posterolateral approach. Preoperative digital templating determined the desired neck-cut height. Intra-operatively, a sterile ruler cut to the templated length was aligned with the lesser trochanter to mark the osteotomy. A calibration gauge assessed limb length before final implantation. Postoperative neck-cut height, LLD, and patient-reported outcomes [Oxford Hip Score (OHS) and EuroQol 5-Dimension 5-Level (EQ-5D-5L)] were evaluated at 6 weeks and 6 months. Paired t-tests, linear regression, and inter-observer reliability analyses were performed.

Results: Mean templated, intra-operative, and 6-week postoperative radiographic neck cuts were 12.73, 12.70, and 12.56 mm, respectively. There was no significant difference between templated and postoperative cuts (mean difference =−0.17 mm; P=0.5) or between intra-operative and postoperative cuts (P=0.6). Regression analysis showed a strong correlation between templated and postoperative values (R²=0.74), with 96% of cases within ±5 mm of the plan. Inter-observer reliability was excellent (Pearson r=0.993). LLD improved from −2.9 mm pre-operatively to 1.8 mm post-operatively (P<0.001). OHS improved from 13.5 to 43.1 and EQ-5D-5L from 0.20 to 0.79 (P<0.001).

Conclusions: A ruler-guided femoral neck cut referencing the lesser trochanter accurately reproduces the templated osteotomy and restores leg length in uncemented THA.

Keywords: Total hip arthroplasty (THA); leg length; templating; osteotomy; femoral neck length