Navigated and nonnavigated total hip arthroplasty: results of two consecutive series using a cementless straight hip stem.

The purpose of this study was to compare conventional and navigated technique and a recently developed straight hip stem for uncemented primary total hip arthroplasty. The results of two consecutive implantation series of 42 patients (nonnavigated) and 42 patients (navigated) were analysed for implant positioning and complications. All surgeries were performed by the investigator. Radiographic analysis of cup position showed a significant improvement with reduced radiologic inclination (53 degrees nonnavigated /44 degrees navigated; P < .001) and higher anteversion (7 degrees nonnavigated /12 degrees navigated; P <.001). The mean postoperative limb length difference was 6.2 mm (SD, 9.0 for nonnavigated) and 4.4 mm (SD, 6.4 for navigated). Intraoperative and early postoperative complications were not different. No dislocation occurred in either group. There was one intraoperative trochanter fracture that was not revised (nonnavigated) and one revision because of a periprosthetic fracture caused by fall down during rehabilitation (navigated). We conclude that acetabular implant positioning can be significantly improved by the use of navigated surgery technique. The data for postoperative limb length difference were still similar but within the expected range in both groups. The effect of improved cup positioning on mid and longterm results for both groups has to be investigated further.