Shape-matching

Background: Shape-matching technology provides preoperative three-dimensional templating of total knee arthroplasty (TKA) placement to restore optimal kinematics for the native prearthritic knee. Despite an accurate preoperative plan to construct cutting jigs for placement of the femoral and tibial implants in a TKA, it is hypothesized that the actual implementation or reproduction of this placement of implants remains suboptimal. Methods: A retrospective radiographic review of 67 primary unilateral TKAs performed using the OtisMed™ (OM, Stryker, Kalamazoo, MI) shape-matching technology was conducted to determine how closely the computer-generated OM preoperative plan resembled the postoperative femoral and tibial implant position in both the coronal and sagittal planes. Results: Preoperative and postoperative measurements were correlated in the coronal (r=0.407, P=0.001), but not the sagittal plane (r=−0.124, P=0.329). Postoperative coronal alignment differed from the preoperative plan more than 3° in 33.3% of cases, while sagittal alignment differed more than 3° in 56.3% of cases. Conclusions: A significant number of cases did not achieve precise placement of the implants per the OM plan, most notably in the sagittal plane. While these differences are noteworthy, the limiting factor still remains our ability to precisely execute the plan.