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Efficacy of a simple intraoperative stem-anteversion measuring device in total hip arthroplasty


 Background Background: Stem anteversion is important in reducing postoperative complications in total hip arthroplasty (THA). THA utilizing the combined-anteversion theory requires stem anteversion angle (SAA) measurement intraoperatively; however, intraoperative SAA estimation is difficult for surgeons without computer-assisted navigation system. We evaluated the accuracy of the SAA measured intraoperatively using a newly developed device by comparing the three-dimensional measurements using postoperative computed tomography (CT).Materials & Methods In 127 hips in 127 patients who underwent unilateral THA at our hospital, we used our newly developed device that can be easily attached to rasping broach handles for measuring the SAA intraoperatively, which required the addition of the correction angle obtained in the preoperative epicondylar view. Postoperative SAA and its discrepancies from the measured intraoperative SAA with or without adding the correction angle were compared between the groups to evaluate the usefulness of the device.Results The intraoperative SAA measured by the device was 17.93 ± 7.53°. The true SAA measured on postoperative CT was 26.40 ± 9.73°. The discrepancy between the intraoperative SAA and true SAA was 8.94 ± 5.44° (without the correction angle), and 4.93 ± 3.85° (with the correction angle). Accuracy with a discrepancy of <5 degrees was achieved in 77 (60.6%) and <10 degrees was achieved in 113 (89.0%). The accuracy was unaffected by the stem placement angle (varus/valgus, or flexion/extension), or ipsilateral knee osteoarthritis.Conclusion The SAA measuring device, easily attachable to various rasping handles, is useful to measure the intraoperative SAA in a simple, economical, and noninvasive manner during THA.Level of Evidence Therapeutic Level IV.