gms | German Medical Science

Objectives: The MAKO Stryker robotic system provides an alternative to conventional surgical techniques in knee arthroplasty and allows precise realization of CT-based prosthesis planning. This study depicts long term data on clinical outcome, patient satisfaction and comorbidity of robot-assisted TKA/UKA (Total/Unicompartmental Knee Arthroplasty) aiming to identify patient groups that benefit most.

Methods: In this prospective longitudinal study, n=61 patients (mean age 68.33 years) underwent UKA (n=20) or TKA (n=41) surgery. Preoperative (t=0), short term (t=3 months) and long term (t=12 months) outcome was evaluated including clinical examination and collection of Patient Reported Outcome Measures (PROMs) to access pain, mobility and problems in daily life activities. PROMs used were the EQ VAS (visual analogue scale), EQ5D5L, OKS (Oxford Knee Score) and FJS (Forgotten Joint Score). The ASA (American Society of Anesthesiologists) score was collected from administrative data. Radiological results were recorded (e.g. Caton-Deschamps-Index (CDI). TKA patients were operated according to the theory of kinematic alignment, in UKA patients a mechanical alignment was implemented.

Results and conclusion: UKA showed statistically significant improvement in (Mean t=0/12): OKS 33.15/24.55, EQ VAS 61.55/72.0, FJS 13.93/48.13. Statistically significant improvement long vs. short term outcome was observed in mean EQVAS (+7.05) and OKS (-7.9). TKA showed statistically significant improvement in (Mean t=0/12): OKS 34.39/20.59, EQ VAS 61.44/77.02, FJS 17.68/60.82 EQ5D5L-Index 0,75/0,89. Statistically significant improvement short vs. long term outcome in EQVAS (+8.78), OKS (- 8.61) and FJS (+24.64). ROM (t=12) was significantly better than preoperative and in the short term follow-up (t=0/3/12:TKA 112.44/105.73/125.95 °; UKA 115.75/114.74/127.22 °). With respect to ASA-Classification (ASA1/2/3 n= 5/46/10) patients categorized ASA1 performed better in long term outcome compared to ASA2 and 3 with respect to FSJ (ASA1/3: 66.25/41.87) and EQVAS (ASA1/3: 86.6/64.7). Early rehabilitation of ASA1 in EQVAS and FJS was significantly better.

CDI in TKA patients met preoperative patellar positions in the long term (t=0/3/12: 0.87/0.79/0.89) after early patellar depression in the short term.

All patients showed strong improvements of function and satisfaction, even in scores and measurements, that did not significantly improve shortly after the intervention such as EQVAS (UKA), CDI (TKA) and ROM. TKA showed better improvements in the long term, which could be attributable to kinematic alignment. With increasing ASA score, a slower rehabilitation of the functionality of the new joint and the associated patient satisfaction in FJS and EQVAS could be observed. Less comorbid patients showed better results faster than others which may indicate that they benefit more from the intervention. Further research is needed to understand predisposing factors for outcome after robot-assisted knee arthroplasty.