Effectiveness of adductor canal block combined with posterior capsular infiltration on pain and return to walking after total knee arthroplasty: comparative analysis with femoral and popliteal sciatic nerves blocks.

Introduction: Perioperative analgesia after total knee arthroplasty (TKA) reduces morphine consumption and speeds up rehabilitation. The primary objective of this study was to compare the pain experienced by patients with an adductor canal and posterior capsule block with those with a continuous femoral nerve block combined with a popliteal sciatic nerve block. The secondary objectives were to analyze the time to recovery from early walking, length of hospital stay, and block-related complications between the two groups.

Hypothesis: Patients with an adductor canal block and posterior capsular infiltration had less pain 24 h after TKA.

Material and methods: This single-center retrospective study included 774 TKA between January 2020 and March 2023. Two types of locoregional blocks were evaluated: patients who had a continuous femoral nerve block with a single-shot popliteal sciatic nerve block (FN-PSN group) operated on before March 2022 and those who had a single-shot adductor canal block combined with posterior capsular infiltration (ACB-PI group) operated on after March 2022. One patient in the ACB-PI group was matched to two patients in the NF-BS group according to sex, age, and BMI. A total of 725 TKA were included: 500 in the FN-PSN group and 225 in the ACB-PI group. The primary endpoint was pain assessed using the numerical pain rating scale (NPRS) and opioid consumption at 24 h after TKA. Resumption of walking, defined as getting up for the first time and walking ten steps until discharge from the hospital, and complications between the two groups were also assessed. The study population consisted of 471 women (64.9%) with a mean age of 72.2 ± 8.2 years and a mean BMI of 28.2 ± 4.6.

Results: Patients in the FN-PSN group had less pain at NPRS (1.3 versus 1.9; p < 0.001), and fewer patients required morphine titration (13.8% versus 6.8%, p = 0.02) within the first 8 h of surgery with no difference at 24 h, 48 h and 72 h. The mean doses of morphine administered were similar between the groups. Resumption of walking was significantly longer in the FN-PSN group (1.5 versus 2.0 days, p = 0.003), and hospitalization times and complications were similar between the groups.

Conclusion: Adductor canal block combined with posterior capsular infiltration did not reduce postoperative pain compared with femoral and popliteal sciatic block at 24 h after TKA. Opioid consumption and pain were similar between the groups, with more patients requiring morphine in the first eight hours in the ACB-PI group but with a faster return to walking.

Level of evidence: III; comparative study.