Abstract

BackgroundThe femoral component anteversion during surgery is traditionally assessed by a visual assessment of the surgeon and has proven to be imprecise. We sought to determine the accuracy of a digital protractor and a spirit level to measure the stem anteversion during cementless THA.MethodsA prospective study was conducted among 107 patients (114 hips) who underwent primary cementless THA via posterolateral approach. A pipe with a spirit level was attached to the tibial tubercle and intermalleolar midpoint. While the leg was held perpendicularly to the floor, stem anteversion was estimated by 3 methods: method A by visual assessment; method B by a digital protractor alone; and method C by a digital protractor combined with a spirit level. The angles were compared with the true anteversion measured by postoperative CT scan.ResultsThe average anteversion by method C (22.8° ± 6.9°, range -2° to 40°) was significantly lower than method A (24.6° ± 5.2°, range 0° to 30°) (p=0.033), but not different from the true anteversion (22.1° ± 8.2°, range -5.4° to 43.1°) (p=0.445). There were no significant differences between method B (23.2° ± 8.2°, range -4° to 45°) and method A, C or the true anteversion. The mean deviation of the intraoperative estimation from the true anteversion was 0.8° ± 3.7° (range -7.1° to 8.0°) by method C; 1.2° ± 5.1° (range -8.8° to 14.3°) by method B; and 2.5° ± 7.4° (range -19.0° to 16.0°) by method A. Estimation error within 5° was found in 107 hips (93.9%) with method C; 86 hips (75.4%) with method B; and 59 hips (51.8%) with method A.ConclusionAccurate estimation of stem anteversion during cementless THA can be determined intraoperatively by the use of a digital protractor and a spirit level.Trial registrationThai Clinical Trials Registry (TCTR 20180326003). Registered on 20 March 2018. Retrospectively registered.

Highlights

  • Successful total hip arthroplasty (THA) depends on an accurate placement of the femoral and acetabular components [1, 2]

  • We sought to determine the validity of a digital protractor and a spirit level to measure the femoral stem anteversion during cementless THA

  • We hypothesized that our method could achieve this goal in 90% of hips

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Summary

Introduction

Successful total hip arthroplasty (THA) depends on an accurate placement of the femoral and acetabular components [1, 2]. The femoral component anteversion during the surgery is traditionally assessed by a visual estimation of the surgeon for the angle between the leg axis and the femoral stem axis after flexing the knee and placing the leg vertically. This technique has proven to be imprecise. We sought to determine the validity of a digital protractor and a spirit level to measure the femoral stem anteversion during cementless THA.

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