Preoperative Osteoarthritic Grade Affects Forgotten Joint Status and Patient Acceptable Symptom State After Robotic...

This retrospective observational study was designed to investigate the association between radiographic Ahlbäck osteoarthritis (OA) grade and postoperative joint perception in a cohort of patients undergoing medial robotic arm-assisted unicompartmental knee arthroplasty (RA-UKA), using the Forgotten Joint Status and Patient Acceptable Symptom State (PASS) as outcomes.

Between January 2014 and May 2019, 660 patients (719 knees) underwent medial RA-UKA at 2 centers. Ahlbäck OA grade was measured on preoperative knee radiographs. Postoperatively, patients were administered the Forgotten Joint Score-12 (FJS-12) and 5-level Likert scale to assess patients' satisfaction. Correlations were described among FJS-12, satisfaction, and Ahlbäck OA grade by means of logistic regression models.

A total of 547 patients (602 knees) were assessed at a mean follow-up of 3.5 years (standard deviation 1.4). A total of 293 cases were graded as Ahlbäck 1 (Group A) and 309 knees were graded as Ahlbäck>1 (Group B). Statistically significant difference was detected in mean FJS-12 (P < .001), but not in the postoperative satisfaction level (P = .06) between the 2 groups. Patients in Group B had a significantly higher probability of attaining a "forgotten knee" after the operation, compared to Group A (P < .05). Cases in Group A had a significantly lower probability of achieving the PASS (P < .01).

Patients with higher grades of OA (Ahlbäck>1) were more likely to attain a "forgotten knee," while patients with less severe OA (Ahlbäck 1) were less likely to achieve the PASS after RA-UKA. Although patients with less severe OA reported fairly good outcome, cases in which the results will be poorer are currently difficult to predict.