Alignment accuracy and functional outcomes between hand-held navigation and conventional instruments in TKA: a randomized controlled trial

Background This study assessed surgical accuracy and functional outcomes using hand-held accelerometer-based navigation following total knee arthroplasty (TKA). Question: (1) Does hand-held navigation (the iAssist system) improve surgical accuracy (assessed with five parameters commonly used to evaluate surgical alignment: the hip-knee-ankle angle (HKA), femoral coronal angle (FCA), tibial coronal angle (TCA), femoral sagittal angle (FSA), and tibial slope angle (TSA)) compared to conventional instruments in TKA? (2) Which surgical alignment parameters among HKA, FCA, TCA, FSA, and TSA can obtain the most advantage from the iAssist system? (3) Does the iAssist system lead to better functional outcomes at two years of follow-up after TKA? Methods This parallel-group double-blinded randomized controlled trial recruited 60 patients (30 patients each in the iAssist and conventional group) with osteoarthritis who underwent primary TKA by a single surgeon at Siriraj Hospital. There was no loss to follow-up in the study. All procedures in both groups were performed using similar surgical exposure, prosthesis implant, perioperative and postoperative protocols. Participants in the iAssist group received the iAssist system as an assistive technique, while those in the conventional group only had conventional instruments. Surgical alignments (HKA, FCA, TCA, FSA, and TSA) were recorded using CT scan at six weeks post-operation. Functional outcomes were assessed with knee ROM, KSS, and EQ-5D at 6 months, 1 year and 2 years post-operation. Baseline characteristics including age, sex, the affected knee side, and body mass index were comparable between the two groups, similar to preoperative ROM, KSS, and EQ-5D. Results The mean operative time was relatively longer in the iAssist than the conventional group, although not statistically significant (88.1 +/- 13.7 versus 83.4 +/- 21.3; p = 0.314). Among the surgical alignment parameters evaluated, FCA was the only radiographic parameter with a statistically significant difference between the two groups and was closer to 90o in the iAssist group (89.4 +/- 2.2 in the iAssist versus 87.2 +/- 2.1 in the conventional group; p = 0.003). Also, there was a higher proportion of outliers in the conventional than the iAssist group (23.3% versus 10%; p = 0.086). Nonetheless, HKA and TCA did not differ between the two groups (p = 0.25 and 0.096, respectively), although the percentages of outliers were higher in the conventional than the iAssist group (HKA: 26.7% vs. 13.3%; p = 0.101 and TCA: 6.7% versus 0%; p = 0.078). Likewise, we observed other radiographic parameters had no significant group differences, including FSA and TSA. Furthermore, at two years post-operation, we found no differences between the iAssist and the conventional group in knee ROM (106.7 +/- 14.6 versus 108.2 +/- 12.7; p = 0.324), KSS (82.5 +/- 6.4 versus 83.8 +/- 3.4; p = 0.324), and EQ-5D (0.9 +/- 0.2 versus 1.0 +/- 0.1; p = 0.217). All functional outcomes were also comparable at 6 months and 12 months of follow-up postoperatively. Conclusion The iAssist technology increase surgical precision by allowing for a more precise FCA with fewer outliers than conventional equipment. iAssist had longer operative time. Functional outcomes and quality of life were not different.