Does Robotic-Assisted Functional Knee Positioning Result in Better Functional Outcomes One Year After Surgery.

Introduction: Robotic-assisted total knee arthroplasty (TKA) allows surgeons to individualize implant placement based on soft tissue and bony anatomy, called functional knee positioning (FKP). We aimed to compare patient-reported outcome measures (PROMs) of mechanically aligned total knee arthroplasty (MA-TKA) with functionally positioned total knee arthroplasty (FP-TKA).

Materials and methods: Patients who underwent primary MA-TKA and FP-TKA were propensity score matched 1:1 (145 MA-TKA: 145 FP-TKA cases) using a prospectively collected institutional dataset. For FP-TKA cases, the surgeon followed functional positioning principles, individualizing planned implant position to balance the knee prior to bone cuts while minimizing the need for soft tissue releases. For MA-TKA, cases were mechanically aligned and gap balanced using standard techniques. The postoperative reduced Western Ontario and McMaster Arthritis Score (r-WOMAC) Pain and Function scores were compared at six months and one year using average and t-tests. The length of stay (LOS), as well as knee extension and flexion at six weeks were compared.

Results: There was no statistically significant difference in the r-WOMAC pain and r-WOMAC function scores between both groups at six months; however, both trended towards the FP-TKA group. At one year, the r-WOMAC function scores significantly improved for the FP-TKA group compared to controls (2.94 vs. 4.38; p=0.02). There was no significant difference in the r-WOMAC pain scores at one year. The FP-TKA cohort required a shorter LOS compared to those who had MA-TKA (1.75 vs. 2.36; p<0.0001). There was no significant difference in flexion or extension at six weeks between groups (p=0.77 and 0.18, respectively).

Conclusion: We demonstrate that patients who underwent FP-TKA trended toward functional improvements at six months and significant improvements in function at one year (which did not reach minimally clinical important difference). Functional positioning strategies may improve patient-reported outcomes due to minimizing dissection and personalizing implant position.