Analgesic efficacy of popliteal plexus block versus infiltration between the popliteal artery and capsule of the posterior knee block combined with femoral triangle block after total knee arthroplasty: a randomized non-inferiority trial and cadaveric evaluation.

BACKGROUND

Both popliteal plexus block and infiltration between the popliteal artery and capsule of the posterior knee (IPACK) block can alleviate posterior knee pain after total knee arthroplasty (TKA) while preserving motor function. We aimed to assess whether popliteal plexus block is non-inferior to IPACK block in reducing posterior knee pain after TKA.

METHODS

Eighty-six participants undergoing elective TKA were randomized to receive popliteal plexus block or IPACK block combined with femoral triangle block. The primary outcome was moderate-to-severe posterior knee pain at eight postoperative hours. Secondary outcomes included pain scores, fentanyl consumption, sensorimotor function, range of motion, block performance time, quality of recovery, and participant satisfaction. Injectate spread in popliteal plexus block was also assessed in seven cadaveric legs.

RESULTS

The lower bound of the 90% CI for the between-group difference (IPACK - popliteal plexus block) in moderate-to-severe posterior knee pain did not exceed the 17% non-inferiority margin (difference=4.7, (90% CI -5.6 to 14.9; p<0.001)), demonstrating that popliteal plexus block was non-inferior to IPACK block. The block performance time (median (IQR)) was significantly shorter in the popliteal plexus block group (3 (3-5) min) than in the IPACK group (5 (5-6) min; p<0.0001). No significant difference in the preservation of motor function was observed. The posterior articular branches were stained in all the cadaveric specimens.

CONCLUSIONS

Compared with the IPACK block, popliteal plexus block provides non-inferior posterior knee analgesia following TKA while maintaining ankle muscle strength, with the additional advantage of having a shorter block performance time.

TRIAL REGISTRATION NUMBER: UMIN000052472; URL: https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000059848.