Perineural Methylprednisolone Depot Formulation Decreases Opioid Consumption After Total Knee Arthroplasty

Abstract

Purpose: Opioid consumption after total knee arthroplasty (TKA) remains a challenge with single injection nerve blocks even with common local anesthetic adjuvants dexamethasone (DEX). This study aimed to investigate the effects of adding methylprednisolone acetate (MPA) to adductor canal blocks (ACB) and interspace between the popliteal artery and capsule of the posterior knee (iPACK) blocks on postoperative opioid consumption.

Methods: A retrospective analysis was conducted on 100 consecutive TKA patients equally assigned into two groups, with one group receiving DEX through ACB and iPACK block and the other group receiving DEX and methylprednisolone acetate (DEX/MPA) through the same nerve blocks. The primary outcome was cumulative opioid consumption (oral milligram morphine equivalent, OME) during hospitalization for up to three days. Secondary outcomes included daily opioid consumption, highest rest and active pain scores, prosthetic knee joint active range of motion (AROM), laboratory studies including fasting serum glucose (FSG) and white blood cell count (WBC) on each postoperative day (POD), and length of hospital stay.

Results: Cumulative opioid consumption was significantly lower in the DEX/MPA group vs DEX group (median difference (95% CI) = -45.3 (-80.5 to -10), P = 0.011). The highest rest and active pain scores were both significantly lower in the DEX/MPA group than in DEX group on POD 2 (least square mean difference (95% CI) = -1.3 (-2.3 to -0.4), P = 0.005 and -0.9 (-1.8 to -0.1), P = 0.031, respectively). Except on POD 1, FSG values were significantly lower in the DEX/MPA group (median difference (95% CI) = -22.5 (-36 to -8.9), P = 0.001). AROM, WBC, and length of stay were comparable between both groups.

Conclusion: Compared to perineural DEX alone, the addition of MPA further decreases postoperative opioid consumption without clinically significant changes on FSG and WBC.

Level of evidence: III.

Keywords: PNB; TKA; arthroplasty; glucocorticoids; methylprednisolone acetate; perineural; peripheral nerve block; total knee arthroplasty.