Low Accuracy of Stem Implantation in THR Using the CASPAR-system: Anteversion Measurements in 10 Hips

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 degrees (SD 6.3 degrees; 95% CI 3.3 degrees-12.3 degrees) 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.