Accuracy of the preoperative planning for cementless total hip arthroplasty. A randomised comparison between three-dimensional computerised planning and conventional templating

SummaryIntroductionA high accuracy was recently reported for the three-dimensional (3D) computerised planning of total hip arthroplasty (THA), comparing well with navigation regarding leg length and femoral offset. However, there is no randomised study comparing 3D preoperative planning with conventional 2D templating in terms of accuracy and clinical relevance.HypothesisThe 3D preoperative planning has a higher accuracy than the conventional 2D preoperative templating regarding the implants size and their positioning.Patients and methodsA prospective comparative randomised study was carried out from 2008 to 2009, including two groups of 30 patients who underwent THA for primary osteoarthritis. One surgeon performed all the surgical procedures using a minimally invasive direct anterior approach. In one group, the planning was made on calibrated X-rays using 2D templates. In the other group, a CT-scan based 3D computerised planning was performed with dedicated software. The reconstructed hip final anatomy was compared postoperatively to the preoperative planning and the accuracy was expressed as the mean difference (±SD) between the planned positioning and the final positioning of the implants.ResultsThe prediction rate for the stem and the cup sizes were respectively of 100% and 96% in the 3D group versus 43% for both components in the 2D group. When combining both components, the prediction rate was 96% in the 3D group versus 16% in the 2D group. In the 3D group, a high accuracy was achieved for the planning of the leg length (−1.8±3.6mm ranging from −8 to+4mm) and the femoral offset (−0.07±2.7mm ranging from −5 to+4mm) versus 1.37±6.4mm ranging from −9 to 13mm and 0.33±5.7mm (−16 to 11mm) in the 2D templating group (P