INFLUENCE OF PRE-OPERATIVE DEFORMITY ON SURGICAL ACCURACY AND TIME IN ROBOTIC-ASSISTED TKA

Introduction We evaluated the utility of imageless computer-navigation coupled with a miniature robotic-cutting guide for managing large deformities in TKA. We asked what effect did severe pre-operative deformities have on post-operative alignment and surgery time using the system. We also report on the early functional outcomes of this group of patients. Methods This was a retrospective cohort study of 128 TKA9s performed by a single surgeon (mean age: 71y/o [range 53–93], BMI: 31.1 [20–44.3], 48males). Patients were stratified into three groups according to their pre-operative coronal plane deformity: Neutral or mild deformity Results Pre-operative coronal alignment ranged from 27(varus to 22(valgus and from 23° flexion to −17° hyperflexion. Postoperative alignment across all patients ranged from 2(valgus to 3.5(varus, and from 4(flexion to −4 (hyperextension. Mean post-operative alignment was 1.4(varus in the control group, 0.4(varus in the severe valgus group (p=0.004), and 1.8(varus in the severe varus group (p=0.111). Preoperative flexion, obesity, and gender had no significant effect on alignment accuracy or final extension. Mean tourniquet time for the control group was 48.8 minutes [95% CI: 45.3–52.4]. Severe varus knees took 4.8 minutes longer (p=0.006), while valgus knees took 2.9 minutes longer (p=0.260). Flexion contractures ≥10(and ≥15(increased tourniquet time by 3.8 minutes (p=0.152) and 10 minutes (p=0.033), respectively. Tourniquet time was slightly longer in obese patients by 3.2 minutes (p = 0.048) and was 6.3 minutes shorter for females than males (p Conclusions We have shown that in one surgeon9s hands severe coronal deformities and flexion contractures can be consistently corrected to within 3° and 4° of neutral, respectively, when using computer navigation. The additional time required for managing these more difficult cases using this technology was typically 3–5 minutes.