Abstract
PurposeMalalignment of implants is a major source of failure during total knee arthroplasty. To achieve more accurate 3D planning and execution of the osteotomy cuts during surgery, the Signature (Biomet, Warsaw) patient-specific instrumentation (PSI) was used to produce pin guides for the positioning of the osteotomy blocks by means of computer-aided manufacture based on CT scan images. The research question of this study is: what is the transfer accuracy of osteotomy planes predicted by the Signature PSI system for preoperative 3D planning and intraoperative block-guided pin placement to perform total knee arthroplasty procedures?MethodsThe transfer accuracy achieved by using the Signature PSI system was evaluated by comparing the osteotomy planes predicted preoperatively with the osteotomy planes seen intraoperatively in human cadaveric legs. Outcomes were measured in terms of translational and rotational errors (varus, valgus, flexion, extension and axial rotation) for both tibia and femur osteotomies.ResultsAverage translational errors between the osteotomy planes predicted using the Signature system and the actual osteotomy planes achieved was 0.8 mm (± 0.5 mm) for the tibia and 0.7 mm (± 4.0 mm) for the femur. Average rotational errors in relation to predicted and achieved osteotomy planes were 0.1° (± 1.2°) of varus and 0.4° (± 1.7°) of anterior slope (extension) for the tibia, and 2.8° (± 2.0°) of varus and 0.9° (± 2.7°) of flexion and 1.4° (± 2.2°) of external rotation for the femur.ConclusionThe similarity between osteotomy planes predicted using the Signature system and osteotomy planes actually achieved was excellent for the tibia although some discrepancies were seen for the femur. The use of 3D system techniques in TKA surgery can provide accurate intraoperative guidance, especially for patients with deformed bone, tailored to individual patients and ensure better placement of the implant.
Highlights
Malalignment or an incorrectly sized implant is the major cause of failure in total knee arthroplasty (TKA) [12]
In conventional TKA preoperative planning, patients are assessed on the basis of standing anteroposterior and lateral radiographs, sunrise view of the patella or standing wholeleg radiographs to determine the mechanical and anatomical
Preoperative planning based on 2D radiographs was the recommended method to prepare for total knee arthroplasty (TKA)
Summary
Malalignment or an incorrectly sized implant is the major cause of failure in total knee arthroplasty (TKA) [12]. The aim of preoperative planning and assessment of the tibia and femur is to determine the quality of bone stock, to estimate correct relative axial rotational and translational alignment and the position of the joint line and to select a correctly sized implant. Preoperative planning based on 2D radiographs was the recommended method to prepare for total knee arthroplasty (TKA). Recent studies have shown that 2D preoperative methods are not always reliable for TKA [1,2,3, 14, 16]. More accurate 3D computer-assisted techniques are being employed; for example, the navigation techniques in computer-assisted surgery (CAS) help increase alignment accuracy [5, 9]
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