Surgical Accuracy with the Mini-Subvastus Total Knee Arthroplasty : A Computer Tomography Scan Analysis of Postoperative Implant Alignment

A total of 50 total knee arthroplasty (TKA) patients, 25 traditional and 25 minimally invasive surgical (MIS), underwent computed tomography scans to determine if a loss of accuracy in implant alignment occurred when a surgeon switched from a traditional medial parapatellar arthrotomy to a mini-subvastus surgical technique. Surgical accuracy was determined by comparing the computed tomography measured implant alignment with the surgical alignment goals. There was no loss in accuracy in the implantation of the tibial component with the mini-subvastus technique. The mean variance for the tibial coronal alignment was 1.03° for the traditional TKA and 1.00° for the MIS TKA (P = .183). Similarly, there was no difference in the mean variance for the posterior tibial slope (P = .054). Femoral coronal alignment was less accurate with the MIS procedure, mean variance of 1.04° and 1.71° for the traditional and MIS TKA, respectively (P = .045). Instrumentation and surgical technique concerns that led to this loss in accuracy were determined.