Alignment in total knee arthroplasty A comparison of patient specific implants with the conventional technique

Background: Incorrect positioning and malalignment of total knee arthroplasty (TKA) components can result in implant loosening. Restoration of neutral alignment of the leg is an important factor affecting the long-term results of TKA. The aim of our retrospective study was to compare mechanical axis in patients with conventional and patient-specific TKAs. Methods: 232 patients who underwent TKA between January 2013 and December 2014 were included to compare postoperative mechanical axis. 125 patients received a patient-specific TKA (iTotal CR (R), Conformis) and 107 a conventional TKA (TriathlonCR (R), Stryker). Standardized pre- and postoperative long-leg standing radiographs were retrospectively evaluated to compare the two patient cohorts. Results: 113 (90%) radiographs of patient-specific TKA and 88 (82%) of conventional TKA were available for comparison. The preoperative deviation from neutral limb axis was 9.0 (0.1-27.3) in the patient-specific TKA cohort and 8.2 (0.2-18.2) in the conventional TKA group. Postoperatively the patient-specific TKA group showed 3.2 (0.1-8.4) and the conventional TKA cohort 2.3 (0.1-12.5) deviation. However, the rate of +3 outliers from neutral limb axis was 16% in the patient-specific TKA cohort and 26% in the conventional TKA group. Conclusions: Patient-specific TKA demonstrated fewer outliers from neutral leg alignment compared to conventional technique. Potential benefits in the long-term outcome and functional improvement require further investigation. (C) 2018 Elsevier B.V. All rights reserved.