Low accuracy of stem implantation in THR using the CASPAR-system

We studied 10 patients by means of pre- and postoperative CT who underwent computer-assisted total hip replacement using the CASPAR-system (OrthoMaquet GmbH, Rastatt, Germany).The anteversion angles of the stem and translational deviations measured after surgery were compared to the preoperatively planned ones as a quality control. We found an average difference of 7.8° (SD 6.3°; 95% CI 3.3°–12.3°) in the angles and an average difference of 1.8 (SD 1.7; 95% CI 0.6–3.0) mm and 1.2 (SD 1.4: 95% CI 0.25–2.2), respectively, in the medial and lateral deviation.In conclusion, we could not confirm the same accuracy of implant position as that claimed by the manufacturer.