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[Effect of the surgical time and coronalmechanical alignment after total knee arthroplasty using computer navigation system, traditionalor 3D printing patient-specific instruments].

Objective: To compare the surgical time and postoperative coronal mechanical axis alignment in patients with osteoarthritis who were treated with three different total knee arthroplasty (TKA) techniques: computer-assisted navigation surgery (CAS), patient specific instrumentation(PSI) and traditional instrumentation. Methods: A total of 96 patients with severe knee osteoarthritis who underwent unilateral primary TKA by the same surgeon were included in this retrospective study.The patients were divided into CAS-TKA group (34 patients), PSI-TKA group (29 patients) and control group (33 patients) based on surgical techniques used in the operations.The surgical time and postoperative coronal mechanical axis alignment were compared between the three groups.One-way ANOVA was used to detect the differences between three groups, and LSD test was used for the post-hoc test. Results: The overall mean surgical time of the patients was (79±16) min.CAS-TKA group had significantly longer surgical time when compared with those in the other two groups [CAS-TKA vs PSI-TKA: (90±10) min vs (80±14) min, LSD-t=3.458, P<0.05; CAS-TKA vs control: (90±10) min vs (66±11) min, LSD-t=8.350, P<0.05; PSI-TKA vs control: (80±14) min vs (66±11) min, LSD-t=4.582, P<0.05]. The overall mean postoperative coronal mechanical alignment varus/valgus deformity was 2.4° and 2.0°, respectively.The overall outliers (varus/valgus>3°) represented 22.9% of cases and were distributed as followed: 11.8% in CAS-TKA group, 27.6% in PSI-TKA group, 30.3% in control group; and no significant differences was found among the three groups (χ(2)=3.771, P=0.151). Conclusions: The use of CAS or PSI in TKA costs a significant longer surgical time.These two techniques results in acceptable postoperative coronal alignment and both demonstrated a potential benefit in reducing outliers when compared with the traditional instruments.