Intraoperative Sequential Evaluation of the Rotational Stability of a Cementless Stem in Total Hip Arthroplasty—A Preliminary Study

Abstract Background: In cementless total hip arthroplasty (THA), the rotational stability of the stem is generally confirmed in a one-time manual evaluation by the surgeon. This study evaluates the intraoperative sequential changes of rotational stability using a torque wrench.Methods: Primary THA was performed on 65 consecutive hips. The stem design was a single-wedge for 52 hips and metaphyseal-filling for 13 hips. Intraoperative evaluation of rotational stability was uniformly performed using a torque wrench to prevent individual surgeons’ variances. The evaluation was performed immediately after insertion of the broach and before stem insertion.Results: Immediately after insertion of the broach, rotational stability was confirmed using a torque wrench in all cases, which was maintained for 17 of 52 (33%) single-wedge broaches and 4 of 13 (31%) metaphyseal-filling broaches before stem insertion. Among the hips showing instability, 11 of 35 (31%) single-wedge broaches and 6 of 9 (67%) metaphyseal filling broaches were upsized; the remaining hips were stabilized through deeper insertion. Conclusions: Rotational stability achieved immediately after the insertion of the broach was not necessarily maintained during surgery.