Prosthetic orientation, limb alignment, and soft tissue balance with bi-cruciate stabilized total knee arthroplasty: a comparison between the handheld robot and conventional techniques

PURPOSE: This study aimed to examine the prosthetic orientations, limb alignment, intraoperative soft tissue balance, and early clinical outcomes associated with the use of the relatively new handheld robot technique compared to those associated with the use of the conventional alignment guide for bi-cruciate stabilized total knee arthroplasty (TKA). METHODS: This retrospective cohort study compared the prosthetic orientation and limb alignment of 35 patients who underwent TKA using robotic assistance (robot group) with those of patients who underwent TKA using a conventional alignment guide (control group). The coronal femoral component alignment (FCA), coronal tibial component alignment (TCA), and the hip-knee-ankle (HKA) angle were compared between groups. Intraoperative soft tissue balance, including the joint component gap and varus/valgus balance assessed by an offset-type tensor, were also compared between groups. One year postoperatively, the clinical outcomes, including the range of motion and 2011 Knee Society Score (KSS), were compared between groups. RESULTS: The HKA angle and FCA were 0.1° varus and 0.1° varus, respectively, in the robot group and 1.3° varus and 1.3° varus, respectively, in the control group. The difference in the HKA angle and the FCA, but not the TCA, between groups was statistically significant (p < 0.05). The intraoperative soft tissue balance showed more stable joint component gaps and varus/valgus balances throughout the range of motion in the robot group than in the control group. Clinical outcomes of the robot group showed superior 2011 KSS subscales compared to those of the control group. CONCLUSION: The accuracy of the implantations and stable soft tissue balance in the robot group were superior to those of the control group. The robot group also had superior patient-reported scores for early clinical outcomes.