Addition of IPACK to Local Infiltration Analgesia for TKA significantly lowers pain scores

Local infiltration analgesia (LIA) is a popular analgesic technique commonly administered during total knee arthroplasty (TKA). Recent studies have demonstrated that the infiltration between the popliteal artery and the capsule of the posterior knee (IPACK) can be complementary to analgesic modalities. However, the combined and relative efficacy of LIA and IPACK is unclear.

X. Tang et al conducted a study to evaluate the analgesic and functional outcomes among LIA, IPACK, and LIA + IPACK. The study was conducted at Department of Orthopedics, Sichuan University, Orthopedic Research Institute, West China Hospital, Chengdu, People’s Republic of China. It has been published in ‘The Journal of Arthroplasty.’

A total of 120 patients undergoing primary TKA were randomly allocated to 1 of 3 groups:

• LIA (50 mL of 0.25% ropivacaine and 2.0 mg/mL epinephrine);

• IPACK (20 mL of 0.25% ropivacaine and 2.0 mg/ mL epinephrine); and

• LIA + IPACK

The primary outcome was the visual analog scale (VAS) pain score.

Secondary outcomes were opioid use, knee range of motion (ROM), quadriceps muscle strength, mobilization distance, timed up and go (TUG) test, and postoperative complications.

Key findings of the study were:

 The mean VAS pain scores were significantly higher after using IPACK alone than after using LIA + IPACK and LIA within 24 hours (all P＜.05).

 LIA + IPACK had lower mean VAS pain scores than LIA when the knees were at rest (within 12 hours, P < .05) and flexion (within 8 hours, P＜.05).

 Patients receiving LIA + IPACK and LIA had significantly lower morphine equivalents (ME) than those receiving IPACK alone within 24 hours (26.3, 28.9 versus 47.8, both P＜.05) and during hospitalization (98, 101.6, versus 128.4 both P＜.05).

 Both LIA + IPACK and LIA had higher ROM (within 2 days), higher level of muscle strength (within 12 hours), longer mobilization distances (within 1 day), and shorter TUG time (till discharge) compared with IPACK alone (all P＜.05), while LIA + IPACK only had a higher knee ROM than LIA on the first postoperative day (P＜.05).

 There was no significant difference in any other outcomes.

The authors’ concluding statements were - “We found that the differences between LIA + IPACK and IPACK were statistically significant and clinically meaningful, while the differences between LIA + IPACK and LIA were slightly different and failed to reach the MCID. Non-inferior test found IPACK -alone was inferior to LIA alone regarding VAS pain scores and morphine consumption. Additionally, the 20 mL IPACK and 50 mL LIA were safe, with no events of technique complications or local anesthetic toxicity”

Further reading:

Addition of Infiltration Between the Popliteal Artery and the Capsule of the Posterior Knee (IPACK) to Local Infiltration Analgesia for Total Knee Arthroplasty: A Prospective Randomized Controlled Trial X. Tang et al. The Journal of Arthroplasty 2023 https://doi.org/10.1016/j.arth.2022.02.009.