Single-Shot Adductor Canal Block vs Peri-Articular Local Anesthetic Infiltration in TKA

We reviewed eleven randomized clinical trials, which represented the best available evidence, including ten high quality and one moderate quality study to evaluate the effectiveness of regional nerve blocks and peri-articular local anesthetic infiltration to reduce pain and/or opioid consumption following primary TKA.[3, 7, 8, 12, 55-61] Because the workgroup recommends the use of an adductor canal block over alternative regional nerve blocks, these recommendations only focused on a single-shot adductor canal block. Among the included studies, the following comparisons were made in the recommendations: 1. single-shot adductor canal block versus peri-articular local anesthetic infiltration, 2. combined single-shot adductor canal block and peri-articular local anesthetic infiltration versus peri-articular local anesthetic infiltration alone, 3. combined single-shot adductor canal block and peri-articular local anesthetic infiltration versus single-shot adductor canal block alone. Although direct meta-analysis was utilized to evaluate the individual comparisons, network meta-analysis would have provided more clarity to the potential differences or similarities between combined single-shot adductor canal block and peri-articular local anesthetic or either procedure in isolation. However, network meta-analysis must rely on the assumption of transitivity to compare between treatments not directly compared in a study.[62] Because of the variability in multimodal analgesic protocols, network meta-analysis cannot control for differences in multimodal analgesic protocols as well as direct meta-analysis. Therefore, no network meta-analysis was performed in the formulation of the recommendations. 

Compared to periarticular local anesthetic infiltration, single-shot adductor canal block demonstrated (with limited heterogeneity in direct meta-analysis) no significant difference in postoperative pain with activity at 72 hours (-0.21 SMD; 95% CI -0.55 to 0.13; I2 = 7%) or opioid consumption at 12 hours (-0.03 SMD; 95% CI -0.36 to 0.30; I2 = 0%) or 72 hours (0.24 SMD; 95% CI -0.04 to 0.53; I2 = 0%) following primary TKA.[7, 56, 58, 60] Although the quantitative analysis that included four studies shows no significant difference between a single-shot adductor canal block or peri-articular local anesthetic infiltration, the qualitative analysis of all eight studies demonstrates conflicting results with the quantitative analysis.[7, 55-61] Of the eight studies reporting on postoperative pain, five studies favored single-shot adductor canal block, two studies favored peri-articular local anesthetic infiltration, and one study had no difference in pain following primary TKA.[7, 55-61] Of the seven studies reporting on opioid consumption, three studies favored single-shot adductor canal block, one study favored peri-articular local anesthetic infiltration, and three studies had no difference in opioid consumption following primary TKA.[7, 55, 56, 58-61] The workgroup chose to downgrade the strength of the recommendation from strong to moderate strength based on the inconsistency between the quantitative and qualitative analysis. Because a strong recommendation represents future research is not likely to change the recommendation, the workgroup believes additional research has the potential to clarify the discordance in the analyses.

Combined single-shot adductor canal block and peri-articular local anesthetic infiltration demonstrated (with no heterogeneity in direct meta-analysis) reduced postoperative pain at 24 hours (-0.38 SMD; 95% CI -0.65 to -0.10; I2 = 0%) but no difference in opioid consumption at 24 hours (-0.07 SMD; 95% CI -0.34 to 0.20; I2 = 0%), 48 hours (0.05 SMD; 95% CI -0.22 to 0.32; I2 = 0%), or 72 hours (-0.06 SMD; 95% CI -0.34 to 0.21; I2 = 0%) following primary TKA compared to peri-articular local anesthetic infiltration alone.[3, 7] However, the qualitative analysis among the four studies show the potential for reduced pain and opioid consumption for combined singleshot adductor canal block and peri-articular local anesthetic infiltration.[3, 7, 8, 12] Similar to the prior recommendation, the workgroup chose to downgrade the strength of the recommendation from strong to moderate based on the inconsistency between the quantitative and qualitative analysis. When comparing combined single-shot adductor canal block and peri-articular local anesthetic infiltration to single-shot adductor canal block alone, qualitative analysis demonstrated reduced pain and opioid consumption following primary TKA for the combination treatment.[7, 61]

The workgroup recommends routine use of either a single-shot adductor canal block or peri-articular local anesthetic infiltration for patients undergoing primary TKA.  Although the current available evidence does not suggest the combination of a single-shot adductor canal block and peri-articular local anesthetic infiltration is necessary in primary TKA, it could provide additional reduction in postoperative pain and opioid consumption compared to either alone.