Abstract
Background
Adductor canal block (ACB) is an alternative method to femoral nerve block (FNB) for post-operative analgesia for anterior cruciate ligament reconstruction (ACLR) in pediatric and adolescent patients. Prior studies have suggested that FNB is associated with persistent strength deficits at 6 months after ACLR in this population. Proponents of the ACB consider that this method may result in a decreased incidence of quadriceps strength deficits during post-operative rehabilitation. The purpose of this study was to compare knee strength and function at 6 and 9 months after ACLR in pediatric and adolescent patients who received FNB versus ACB peri-operatively.
Methods
Patients 18 years or younger who underwent primary ACLR between 2002 and 2017 at a single institution were identified. ACLR was performed with either a patellar tendon autograft or hamstring autograft. A transphyseal ACLR was performed in patients with open physes. All patients participated in a comprehensive rehabilitation program which included isokinetic strength testing and functional testing at 6 and/or 9 months postoperatively. Patients were excluded if they underwent multiligamentous knee reconstruction, concomitant cartilage restoration procedures, did not receive perioperative FNB or ACB, or if they did not complete isokinetic strength and functional testing at 6 or 9 months. The included cohort was separated into FNB group and ACB group for comparison. Isokinetic extension and flexion strength deficits and functional deficits in vertical jump, single hop, and triple hop between the two groups were compared at both time points. A strength deficit of 15% or less and a functional deficit of 10% or less compared to the contralateral side were considered satisfactory. Univariate analysis was performed to assess for differences in patient demographics and surgical variables. A 1:1 matched subgroup analysis between the two groups was performed to account for possible differences in outcomes associated to graft types, concomitant meniscus repair, and BMI.
Results
Of the 240 patients identified, 85 patients (64 FNB, 21 ACB) with a mean age of 15.9 years (Range: 11-18) met inclusion criteria for comparison at 6 months and 76 patients (40 FNB, 36 ACB) with a mean age of 15.5 years (Range: 12-17) met inclusion criteria for comparison at 9 months. Univariate analysis showed significantly greater deficits at 6 months in the FNB with respect to fast isokinetic flexion strength (7.7% vs. -4.9%; p = .03). There were no differences in slow isokinetic flexion (10.5% vs. 6.8%; p = .79) and fast isokinetic extension (11.9% vs. 13.9%; p = .68) strength deficits between the groups. There were clinically relevant greater deficits in the FNB group with respect to slow isokinetic extension (19.3% vs. 12.0%; p = .24), but this did not reach statistical significance. This clinical difference in satisfactory scores between the groups with respect to slow isokinetic extension was accentuated with the 1:1 matched outcome trial (23.9% vs. 12.1%; p = .20). With respect to function, there were no differences in deficits for vertical jump (8.4% vs. 4.3%; p = .55), single hop (7.4% vs. 9.3%; p = .65), or triple hop (6.0% vs. 7.1%; p = .77) between the two groups. Univariate analysis showed significant greater deficits at 9 months in the FNB with respect to slow isokinetic flexion strength (9.6% vs. 0.4%; p = .01). There were no differences in fast isokinetic flexion (-0.2% vs. 0.7%; p = .87) and fast isokinetic extension (6.0% vs. 2.7%; p = .51) strength deficits between the groups. There were clinically relevant greater deficits in the FNB group with respect to slow isokinetic extension (17.3% vs -14.0%, p = .19), but this did not reach statistical significance. With respect to function, there were no differences in deficits for vertical jump (5.2% vs. 6.5%, p = .85), single hop (7.7% vs. 6.2%; p = .79), or triple hop (1.9% vs. 3.9%; p = .35) between the two groups.
Conclusion
Because previous studies have shown a significant delay in return of strength with FNB, ACB began to be employed at our center for post-operative pain control following ACLR in pediatric and adolescent patients. This study showed that pediatric and adolescent patients treated with FNB as a method of post-operative analgesia after ACLR had significantly greater deficits in fast isokinetic flexion at 6 months and slow isokinetic flexion at 9 months compared to those who received ACB. These differences may or may not have clear clinical relevance. However, patients treated with FNB showed clinically relevant greater deficits in slow isokinetic extension strength at 6 and 9 months postoperatively compared to those who received ACB if 85% strength return is used as criteria to return to sport. Pediatric and adolescent patients could benefit from undergoing perioperative analgesia with ACB instead of FNB, but comparison between these two methods of regional anesthesia may require a prospective trial.
Level of Evidence
Retrospective cohort study, Level IV
Isokinetic and Functional Testing 6 Months after Anterior Cruciate Ligament Reconstruction*
| Femoral Nerve Block (n = 64) | Adductor Canal Block (n = 21) | p value | ||
|---|---|---|---|---|
| Slow-Flexion Deficit | 10.5% | 6.8% | .79 | |
| Fast-Flexion Deficit | 11.9% | -4.9% | .03 | |
| Slow-Extension Deficit | 19.3% | 12.0% | .24 | |
| Fast-Extension Deficit | 11.9% | 13.9% | .68 | |
| Vertical-Jump Deficit | 8.4% | 4.3% | .55 | |
| Single-Hop Deficit | 7.4% | 9.3% | .65 | |
| Triple-Hop Deficit | 6.0% | 7.1% | .77 | |
*Values represent percentage deficit as compared to contralateral side
Isokinetic and Functional Testing 9 Months after Anterior Cruciate Ligament Reconstruction*
| Femoral Nerve Block (n =40) | Adductor Canal Block (n = 36) | p value | ||
|---|---|---|---|---|
| Slow-Flexion Deficit | 9.6% | 0.4% | .01 | |
| Fast-Flexion Deficit | -0.2% | 0.7% | .87 | |
| Slow Extension Deficit | 17.3% | -14.0% | .19 | |
| Fast-Extension Deficit | 6.0% | 2.7% | .51 | |
| Vertical-Jump Deficit | 5.2% | 6.5% | .85 | |
| Single-Hop Deficit | 7.7% | 6.2% | .79 | |
| Triple-Hop Deficit | 1.9% | 3.9% | .35 | |
*Values represent percentage deficit as compared to contralateral side