Reduced postoperative inflammation and blood loss after robotic arm-assisted unicompartmental compared with total knee arthroplasty: A propensity score-matched analysis.

Abstract

Robotic arm-assisted unicompartmental knee arthroplasty (raUKA) offers potential advantages over robotic arm-assisted total knee arthroplasty (raTKA), but its biological benefits remain unclear. Superior early recovery after raUKA may be related to reduced systemic inflammation and blood loss. It was hypothesised that raUKA would elicit a lower systemic inflammatory response and result in reduced perioperative blood loss compared with raTKA. Patients undergoing raUKA with the Mako® system were 1:1 propensity score-matched to raTKA patients based on age, gender, body mass index, and ASA score, yielding two balanced cohorts (n = 162 each). Blood samples were collected preoperatively, 6 h postoperatively, and on postoperative Days 3 and 5. Primary outcomes were C-reactive protein (CRP) and white blood cell (WBC) levels; secondary outcomes included operative time and calculated blood loss. CRP increases were significantly lower after raUKA on Day 3 (1.6 vs. 4.6 mg/dL, p < 0.001) and Day 5 (0.8 vs. 3.7 mg/dL, p = 0.031). WBC counts were lower at 6 h in raUKA (3.8 vs. 4.5 G/L, p = 0.041) but not significantly different on Days 3 or 5. Median operative time was shorter with raUKA (81 vs. 95 minutes, p < 0.001). Haemoglobin decrease and estimated blood loss were reduced in raUKA compared with raTKA (532 vs. 669 mL, p < 0.001). This is the first study to directly compare inflammatory response and blood loss between raUKA and raTKA. raUKA was associated with lower CRP and early WBC elevations, reduced blood loss, and shorter operative times. These results provide clinically relevant biomarker reference values and highlight perioperative advantages of raUKA. Collectively, they support raUKA as a less invasive alternative to raTKA in appropriately selected patients. Level III, retrospective comparative study.