Continuous vs. Single-Shot Adductor Canal Block in TKA
Continuous adductor canal block could reduce postoperative pain and opioid consumption without an increase in adverse events compared to a single-shot adductor canal block following primary total knee arthroplasty.
Anesthesia and Analgesia in Total Joint Arthroplasty (2021)
Developed by: American Association of Hip and Knee Surgeons, American Society of Regional Anesthesia and Pain Medicine, American Academy of Orthopaedic Surgeons, The Hip Society, and The Knee Society

Rationale

We reviewed twenty-nine randomized clinical trials, which represented the best available evidence, including twenty high quality and nine moderate quality studies to evaluate the effectiveness of a single-shot or continuous femoral nerve block or adductor canal block or infiltration between Popliteal Artery and Capsule of Knee (iPACK) to reduce pain and/or opioid consumption following primary TKA.[2-30] Among the included studies comparing a regional nerve block to control, thirteen studies investigated a single-shot femoral nerve block, eight studies investigated a continuous femoral nerve block, six studies investigated a single-shot adductor canal block, four studies investigated a continuous adductor canal block, and one study investigated iPACK.[2-30] Although additional regional nerve blocks have been studied with randomized clinical trials following primary TKA, the workgroup excluded these alternative regional nerve blocks because of limited evidence or lack of clinical relevance. For instance, a combined femoral and sciatic nerve block effectively provides total analgesia of the lower extremity, but it causes significant motor weakness not conducive to early postoperative mobilization. Similar to prior clinical practice guidelines on postoperative analgesia, only a limited number of meta-analyses were capable of being performed to support the recommendations.[31-34] Inconsistencies in the reporting of outcomes and timepoint for reporting of outcomes frequently resulted in substantial heterogeneity in the metaanalyses. Despite the numerous high and moderate quality studies on single-shot or continuous femoral nerve blocks, the meta-analyses related to pain and opioid consumption were omitted from consideration in the recommendations due to the presence of substantial heterogeneity. However, qualitative analyses of studies on singleshot or continuous femoral nerve block consistently demonstrate a significant reduction in postoperative pain and opioid consumption for both types of blocks compared to controls.[4, 9-11, 13, 14, 16-19, 22-30] In direct meta-analysis and with no heterogeneity single-shot adductor canal block demonstrate reduced opioid consumption compared to controls (-0.46 standard mean difference [SMD]; 95% confidence interval [CI] -0.78 to - 0.13; I2 = 0%).[3, 21] Similarly, continuous adductor canal block demonstrated with no heterogeneity in direct meta-analysis to reduce opioid consumption compared to controls (-0.54 SMD; 95% CI -0.81 to -0.27; I2 = 0%).[6, 15, 20] Because meta-analysis was not available to evaluate postoperative pain, qualitative assessment demonstrated evidence of a reduction in postoperative pain for a single-shot or continuous adductor canal block compared to controls.[3, 5-8, 12, 15, 20, 21] Among the fifteen studies reporting on adverse events, the studies consistently demonstrate no increase in adverse events with a single-shot or continuous femoral nerve block or adductor canal block compared to controls.[3, 9, 12-16, 19-23, 26-28] One study evaluated the iPACK block. In this high quality randomized clinical 69 patients, iPACK reduced postoperative pain but not opioid consumption following primary TKA.[2] The workgroup chose to downgrade the strength of the recommendation from moderate to limited strength based on the inconsistency in the results of the reported outcomes on postoperative visual analogue scale pain with and without activity.

Although strong evidence demonstrated that single-shot and continuous femoral nerve and adductor canal blocks are safe and effective methods to reduce postoperative pain and opioid consumption following primary TKA, we reviewed twenty-three high and moderate quality randomized clinical trials comparing the efficacy and safety between regional nerve blocks.[4, 5, 16, 35-54] Among the included studies, the following comparisons were made between regional nerve blocks: 1. single-shot femoral nerve block versus continuous femoral nerve block, 2. single-shot femoral nerve block versus single-shot adductor canal block, 3. continuous femoral nerve block versus continuous adductor canal block, and 4. continuous adductor canal block versus singleshot adductor canal block. The qualitative analysis demonstrated no difference in postoperative pain, opioid consumption, or adverse events between single-shot and continuous femoral nerve blocks following primary TKA.[4, 16, 36, 48] Single-shot femoral nerve and adductor canal blocks demonstrated (with no heterogeneity in direct meta-analysis) no difference in postoperative pain at 24 hours (-0.10 SMD; 95% CI -0.40 to 0.19; I2 = 0%), pain at 48 hours (0.08 SMD; 95% CI -0.21 to 0.38; I2 = 0%) or opioid consumption (-0.06 SMD; 95% CI -0.35 to 0.24; I2 = 0%) following primary TKA.[39, 41, 43, 44, 51, 54] However, the five studies reporting on motor function consistently demonstrated decreased quadriceps strength persisting as long as 24 hours with a singleshot femoral nerve block.[39, 41, 43, 51, 54] Similarly, continuous femoral nerve and adductor canal blocks demonstrated (with no heterogeneity in direct meta-analysis) no difference in rescue opioid consumption on the first postoperative day (1.5 SMD; 95% CI -0.51 to 4.44; I2 = 0%) while qualitative analysis demonstrated no difference in pain following primary TKA, but continuous femoral nerve block was associated with the presence of decreased quadriceps strength persisting up to 24 hours.[37, 40, 47, 49, 53] Continuous adductor canal block demonstrated (with limited heterogeneity in direct meta-analysis) reduced postoperative pain at 8 hours (-1.26 SMD; 95% CI -1.56 to -0.96; I2 = 0%) and at 36 hours (-0.59 SMD; 95% CI -0.89 to -0.29; I2 = 0%) and reduced 48 hour opioid consumption (-0.32 SMD; 95% CI -0.64 to -0.001; I2 = 23%) following primary TKA compared to single-shot adductor canal block.[5, 35, 38, 42, 45, 46, 50, 52] Despite the evidence demonstrating improved efficacy for continuous compared to single-shot adductor canal block, the workgroup downgraded the recommendation from strong to moderate due to concerns regarding the associated cost, increased resource utilization, and risk of retained catheters with a continuous adductor canal block. Based on the best available evidence, the workgroup believes a femoral nerve block has a limited role in primary TKA due to the association of quadriceps weakness and demonstrated efficacy of an adductor canal block. We recommend the use of a single-shot adductor canal block when regional anesthesia is used in primary TKA; however, the workgroup would recommend consideration of a continuous adductor canal block in patients at risk for poor postoperative pain control.