Analgesia and functional outcome after total knee arthroplasty: periarticular infiltration vs continuous femoral nerve block.

BACKGROUND: Capacity to ambulate represents an important milestone in the recovery process after total knee arthroplasty (TKA). The purpose of this study was to determine the analgesic effect of two analgesic techniques and their impact on functional walking capacity as a measure of surgical recovery.

METHODS: Forty ASA II-III subjects undergoing TKA were enrolled in a randomized, double-blind, single-centre study receiving 48 h postoperative analgesia with either periarticular infiltration of local anaesthetic (Group I) or continuous femoral nerve block (Group F). Breakthrough pain relief was achieved with patient-controlled analgesia (PCA) morphine. The main outcome was postoperative morphine consumption. Early (postoperative days 1-3) and late (6 weeks) functional walking capacity (2 and 6 min walk tests, 2MWT and 6MWT, respectively), degree of physical activity (CHAMPS), health-related quality of life (SF-12), and clinical indicators of knee function (WOMAC, Knee Society evaluation, and range of motion) were measured.

RESULTS: Patients in Group F used the PCA less (P=0.02) to achieve adequate analgesia. Postoperative 2MWT was similar in both groups (P=0.27). Six weeks after surgery, recovery of 6MWT, physical activity, and knee function were significantly improved in Group F (P<0.05). Preoperative walking capacity, physical activity and early total walking time were the independent predictors of early recovery. Distance and time spent walking were the predictors of functional walking exercise capacity at 6 weeks after surgery.

CONCLUSIONS: Femoral block is associated with lower opioid consumption and a better recovery at 6 weeks than periarticular infiltration. Early postoperative activity measures (2MWT and walking time) were proved to be possible indicators of knee function recovery at 6 weeks after surgery.