Manipulation Under Anesthesia is Safe After Cementless Total Knee Arthroplasty: A Multicenter Study

Cementless total knee arthroplasty (TKA) is thought to facilitate durable, biological fixation between the bone and implant. However, the 4-12 weeks required for osseointegration coincides with the optimal timeframe to perform a manipulation under anesthesia (MUA) if a patient develops postoperative stiffness. This study aims to determine the impact of early MUA on cementless fixation by comparing functional outcomes and survivorship of cementless and cemented TKAs. A consecutive series of patients who underwent MUA for postoperative stiffness within 90 days of primary, unilateral TKA at 2 academic institutions between 2014 and 2018 were identified. Cases involving extensive hardware removal were excluded. Cementless TKAs undergoing MUA (n = 100) were propensity matched 1:1 to cemented TKAs undergoing MUA (n = 100) using age, gender, body mass index, and year of surgery. Both groups had comparable baseline Knee Injury and Osteoarthritis Outcome Scores (KOOS), Short Form (SF)-12 Physical, and SF-12 Mental scores. MUA-related complications as well as postoperative KOOS and SF-12 scores were compared. MUA-related complications were equivalently low in both groups (P = .324), with only 1 patella component dissociation in the cementless group. No tibial or femoral components acutely loosened in the perioperative period. Postoperative KOOS (P = .101) and SF-12 Mental scores (P = .380) were similar between groups. Six-year survivorship free from any revision after MUA was 98.0% in both groups (P = 1.000). Early postoperative MUA after cementless TKA was not associated with increased MUA-related complications or worse patient-reported outcomes compared to cemented TKA. Short-term survivorship was also comparable, suggesting high durability of the bone-implant interface.