use of a digital protractor and a spirit level to determine the intraoperative anteversion of femoral component during cemented hip hemiarthroplasty: a prospective clinical trial

Background: femoral stem anteversion during hip arthroplasty is generally estimated by eye intraoperatively and hasproven to be different from targeted values. this study aims to determine the accuracy of a novel technique using adigital protractor and a spirit level to improve surgeons’ estimation of stem anteversion.methods: a prospective non-randomized study was conducted among 93 patients with femoral neck fracture who underwent cemented hemiarthroplasty via posterolateral approach. in the control group (n=62), five experienced surgeons assessed stem anteversion related to the posterior femoral condylar plane using visual estimation with atarget angle of 15°-25°. in the study group (n=31), another two surgeons assessed stem anteversion with the sametarget angle by placing a digital protractor on the femoral stem inserter handle while the assistant held the leg in the trulyvertical position, verified by a spirit level that was attached to the shin with cable ties. stem anteversion was measuredblind, postoperatively, on 2d-ct and compared with the intraoperative results.results: the mean postoperative anteversion was 22.4° (-4.2° to 51.3°, sd 11.1°) in the control group and 23.0° (16.0° to 29.9°, sd 3.6°) in the study group (p=0.810). the study group had more stems positioned in 15°-25° anteversion (71.0% vs 32.3%, p=0.001) and the mean absolute value of surgeon error was -0.2° (-5.4° to 7.0°, sd 3.0°). twenty eightstems of the study group (90.3%) had an error within 5°. surgeon overestimation >5° was found in 1 hip (3.2%)and underestimation >5° was found in 2 hips (6.4%).conclusion: using a digital protractor and a spirit level was reliable with high accuracy and precision to improve theintraoperative estimation of cemented stem anteversion.level of evidence: ii