Abstract
INTRODUCTION
Recently, the short stem has become popular in total hip arthroplasty (THA). The advantages of the short stem are that it preserves femoral bone stock, possibly results in less thigh pain, and is suitable for minimally invasive THA. However, because of the short stem, malposition may happen during surgery. The purpose of this study was to compare the stem alignment, which was measured by CT, between the standard tapered round stem and the shorter tapered round stem.
MATERIALS AND METHODS
CT evaluation was performed in 28 patients (29 joints) who underwent primary THA. The standard tapered round stem (Bicontact D stem) was used in 13 patients. The shorter stem (Bicontact E stem) was used in 16 patients (17 joints). The proximal shapes of these two stems have almost the tame curvature. The mean age at surgery was 68 years. The mean BMI at surgery was 23.3 kg/m2. Eighteen patients had osteoarthrosis, 3 patients had osteonecrosis, and 1 patient had femoral neck fracture. All surgeries were performed in the supine position with the direct anterior approach. The OrthoPilot imageless navigation system was used during surgery. Evaluation of the stem antetorsion angle (AA), flexion angle (FA), and varus angle (VA) were carried out.
RESULTS
The mean AA was 27.5±8.2 degrees [range 12.3–43.1 degrees] in the standard stem and 21.6±5.9 degrees [range 12.7–31.9 degrees] in the shorter stem. The standard stem showed significantly higher AA compared to the shorter stem. The mean FA was −2.3±1.2 degrees [−4.8 to 1.1 degrees] in the standard stem and −3.2±1.8 degrees [range −6.5–0.1 degrees] in the shorter stem. The mean VA was −0.3±1.2 degrees [−1.7 to 2.5 degrees] in the standard stem and −1.0±2.0 degrees [range −4.4–2.8 degrees] in the shorter stem. There was no significant difference in FA and VA between the standard stem and the shorter stem.
DISCUSSION
This study demonstrated that there was no difference in FA and VA between the standard stem and the shorter stem. The standard stem showed relatively higher AA compared to the shorter stem. The shorter stem may have another advantage in control of the stem antetorsion angle during surgery.
