The Interspace Between Popliteal Artery and Posterior Capsule of the Knee (IPACK) Block in Knee Arthroplasty: A Prospective Randomized Trial.

BACKGROUND

Optimal analgesia following knee surgery is essential for early mobilization and rehabilitation and minimizing morbidity.

OBJECTIVES

We compared the addition of the interspace between the popliteal artery and the posterior capsule of the knee (IPACK) block to the adductor canal block (ACB) versus ACB alone on postoperative analgesia and ambulation ability in patients undergoing total knee arthroplasty (TKA).

STUDY DESIGN

A prospective randomized study.

SETTING

An academic medical center.

METHODS

Eighty patients undergoing TKA were randomly allocated to receive either ACB or combined ACB-IPACK block at the end of surgery. ACB was performed using 20 mL bupivacaine 0.25% in both groups, while IPACK block using 30 mL bupivacaine 0.25% was added in the ACB-IPACK group only. Visual analog scale (VAS) was evaluated at rest and with 45° knee flexion at 4, 6, 12, and 24 hours postoperatively. The quadriceps muscle power and mobilization ability were assessed at 12 hours and 24 hours postoperative. Total 24 hour postoperative morphine consumption, time to first rescue analgesic request, and patient satisfaction were documented.

RESULTS

The mean postoperative morphine consumption was higher in the ACB group (20.93 ± 7.17 mg) than the ACB-IPACK group (9.68 ± 3.56 mg) (P < 0.001, 95% CI; 8.71; 13.79). The time to 1st rescue analgesic consumption was longer in the ACB-IPACK group (645 ± 254 min) than ACB group (513 ± 247 min) (P = 0.021, 95% CI; 20.4; 243.6). At 4 hours, 6 hours, and 12 hours postoperative, the median postoperative VAS scores were higher in the ACB group than those of the ACB-IPACK group at rest (P = 0.003, 0.001 and 0.007) and on 45° knee flexion (P = 0.001, 0.001, 0.002) respectively. At 24 hours, the median VAS score was comparable between both groups both at rest and on 45° knee flexion (P = 0.358 & 0.054), respectively. The TUG test and the straight leg raise (MRC) scales at 12 hours, and 24 hours postoperative were comparable between both groups (P > 0.05).

LIMITATIONS

This study was limited by its small sample size.

CONCLUSION

The addition of IPACK to the ACB significantly reduced the postoperative morphine consumption and postoperative pain scores compared to the ACB alone without significant difference in mobilization ability in patients undergoing TKA.