Periarticular Local Infiltrative Anesthesia and Regional Adductor Canal Block Provide Equivalent Pain Relief After Anterior Cruciate Ligament Reconstruction

Abstract

Purpose:

To compare postoperative pain and recovery after anterior cruciate ligament reconstruction (ACLR) in patients who received an adductor canal block (ACB) or periarticular local infiltrative anesthesia (LIA).

Methods:

A retrospective review of a prospectively collected ACL registry was performed. Patients underwent ACLR at a single institution between January 2015 and September 2020 and received long-acting local anesthesia with a pre-operative ultrasound-guided ACB or peri-articular LIA after surgery. Visual Analog Scale (VAS) pain scores, milligram morphine equivalents (MME) consumed in the post-anesthesia care unit (PACU), and total hospital recovery time were compared. Univariate analysis was used to compare VAS pain and MME totals between overall groups and groups propensity score matched for age, sex, BMI, graft type, and meniscal treatment. Results are presented as mean(95%CI) unless otherwise indicated.

Results:

There were 265 knees (253 patients) included (LIA, 157 knees; ACB, 108 knees). Overall, VAS pain scores before hospital discharge (LIA 2.6 (2.4-2.8) vs. ACB 2.4 (2.1-2.7), p=0.334) and total MMEs were similar (LIA 17.6 (16.4-18.8) vs. ACB 18.5 (17.2-19.8) (MME), p=0.134). Median time to discharge also did not significantly differ (LIA 137.5 (IQR:116-178) vs. ACB 147 (IQR:123-183) (min), p=0.118). Matched sub-analysis (LIA and ACB, n=94) did not reveal significant differences in VAS pain before discharge (LIA 2.4 (2.1-2.7) vs ACB: 2.7 (2.4-3.0), p=0.134) or total MMEs (LIA 18.6 (17.2-20.0) vs. ACB 17.9 (16.4-19.4), p=0.520).

Conclusion:

The use of ACB or LIA resulted in similar early pain levels, opioid consumption, and hospital recovery times after ACLR surgery.

Level of Evidence:

III, Retrospective Comparison Study

Introduction

Multimodal analgesia is critical for pain management, patient satisfaction, and successful early rehabilitation after anterior cruciate ligament reconstruction (ACLR).^1–3 Regional anesthesia provides targeted pain control after surgery and has been shown to reduce both hospital recovery time and opioid consumption.^{1, 4} A femoral nerve block (FNB) may provide more effective analgesia than standard medication regimens, but significant quadricep deficits with this method can negatively affect strength and risk of graft rupture early after ACLR surgery.⁵ In comparison to femoral nerve blocks, adductor canal blocks (ACB) target the femoral nerve distally with the goal of selectively blocking sensory innervation to better preserve quadriceps function.^{6, 7} However, potential disadvantages exist with ACB’s as well; for instance, if a large volume of local anesthetic is injected into the proximal adductor canal⁸, significant weakness of the quadriceps can also occur, which has been documented in case reports.⁹

Periarticular local infiltrative anesthesia (LIA) is another method that can provide effective postoperative pain relief after outpatient knee surgery.^10–12 Combining long-acting local anesthetic, opioid, and NSAID in a single-injection targets multiple receptors that mediate pain generation and peripheral transmission. There is a paucity of literature that directly compares postoperative pain control and hospital recovery after using LIA or ACB for ambulatory ACLR surgery. One study compared the analgesic efficacy of periarticular LIA to regional ACB for isolated ACLR surgery and found similar early postoperative pain levels without impairing functional outcomes.¹³ Additional studies are needed to investigate the analgesic efficacy of both ACB and LIA in patients undergoing ACLR surgery with concomitant procedures. The purpose of this study was to compare postoperative pain and recovery after anterior cruciate ligament reconstruction (ACLR) in patients who received an adductor canal block (ACB) or periarticular local infiltrative anesthesia (LIA). We hypothesized that patients who received peri-articular LIA would have similar early pain levels and total hospital recovery times in comparison to those who received an ACB.

Methods

The following study was performed with approval from the Institutional Review Board at the University of Iowa (UI-IRB 1 no. 201201715). A retrospective review of a prospectively collected ACL registry was performed. Registry participants included in the present study underwent ACLR at a single institution between January 2015 and September 2020 and received an adductor canal block (ACB group) or peri-articular local infiltrative anesthesia (LIA group) for immediate post-operative pain control. Those who received ACLR with concomitant meniscus or cartilage treatments were included in analyses. Registry participants who received an alternative nerve block (femoral) or those who did not receive LIA were excluded. Primary outcomes of interest were Visual Analog Scale (VAS) pain levels, milligram morphine equivalents (MME) consumed in the post-anesthesia care unit (PACU), and total hospital recovery time before hospital discharge. In addition, pain levels from the early post-operative period and Knee Injury and Osteoarthritis Outcome Score¹⁴ (KOOS) pain scores at 6 weeks after surgery were collected and compared between groups.

Procedure Details

Both ACB and LIA were used in addition to general anesthesia for postoperative pain control. Staff anesthesiologists performed regional ACB’s preoperatively with long-acting local anesthetic (Bupivacaine 0.5% or Ropivacaine 0.5%, 15-20mL). All ACB’s were performed as single injections into the adductor canal under ultrasound visualization. For patients in the LIA group, the surgeon performed the peri-articular LIA in the operating room after the incisions were closed. The knee joint was injected intra-articularly, and sites of surgical exposure and subcutaneous tissue were infiltrated with a long-acting local anesthesia cocktail consisting of 300 mg of 0.5% Ropivacaine, 30 mg of 30mg/mL Ketorolac, 0.6 mg of 1mg/mL Epinephrine, and 5 mg of 0.5mg/mL Morphine mixed in 100 mL 0.9% sodium chloride. All ACLR procedures were performed by four board-certified orthopedic surgeons fellowship-trained in sports medicine (KRD, BRW, and RWW). Autologous graft harvest of hamstrings, bone-patellar tendon-bone and quadriceps tendons were performed via standard open or mini-open techniques. ACLR was then performed with arthroscopic-assisted technique, utilizing both anteromedial portal and retrograde drilling techniques based on surgeon preference and graft type. When encountered, meniscus pathology was treated by meniscectomy or meniscus repair using a variety of techniques based on surgeon preference. All patients received a standardized perioperative oral pain (PO) medication protocol. In the preoperative area, patients received 5 mg oxycodone, 975 mg acetaminophen, and 600 mg gabapentin. In the PACU, patients received PO oxycodone and acetaminophen when tolerating PO intake dose at 5-10 mg and 650 mg, respectively. Breakthrough IV analgesia included 0.1 mg hydromorphone. Homegoing postoperative prescriptions were provided and included 15 mg meloxicam taken scheduled once daily for 2 weeks, gabapentin 300 mg taken scheduled every 8 hours for 2 weeks, acetaminophen 650 mg taken as needed every 4 hours for 2 weeks, oxycodone 5-10 mg taken as needed every 4 hours (40 prescribed). For skeletally mature patients, aspirin 325 mg daily x 2 weeks was prescribed for deep vein thrombosis (DVT) chemoprophylaxis and was not utilized as an analgesic. Prescriptions were modified only based on verified patient allergies and/or medical comorbidities including hepatic or renal failure.

Data Collection

Demographic variables collected included age, sex, body mass index (BMI), race, and smoking status. Surgical data included primary or revision ACLR, operative side, type of meniscus treatment (meniscus debridement, partial medial or lateral meniscectomy, meniscus repair, meniscal root repair, or meniscus allograft transplant), and type of cartilage procedure (i.e., microfracture, chondroplasty). To measure immediate postoperative pain levels, VAS pain scores (scaled 1-10, where 10 indicated most severe pain) were collected by nursing staff at 20-minute time intervals in the post-anesthesia care unit (PACU) and 2^nd stage recovery room. The first and final VAS scores in the PACU and final scores reported in 2^nd stage recovery (before hospital discharge) were used for analysis. Total recovery times were recorded, including total time in the (PACU), second stage recovery, and total time to discharge (Time in PACU + 2^nd stage). The number, type, and dose of as-needed opioid medications given throughout hospital recovery were directly compared using milligram morphine equivalents (MME). Conversion factors from the Centers for Disease Control (CDC) were used.¹⁵ In addition, routine day-after hospital discharge phone interviews were conducted by nursing staff according to hospital protocol. Telephone records were reviewed to collect VAS pain scores reported by patients. These scores were recorded as Mild (VAS 0-3), Moderate (VAS 4-7), or Severe (VAS 8-10). Data from one interview was used; if the patient did not answer the phone call, a second attempt was made the following day. Lastly, Knee Injury and Osteoarthritis Outcome Score (KOOS) pain subscale scores at pre-operative baseline and 6-weeks were collected. KOOS pain scale questionnaires were distributed by research staff and completed electronically according to the ACL registry Institutional Review Board protocol. The number of patients in both groups who reached the patient acceptable symptom state (PASS) and minimal important change (MIC) for KOOS pain scores were also determined.¹⁶

Statistical Analysis

Descriptive statistics were performed. Continuous variables were evaluated for normality using the Shapiro-Wilk test and through evaluation of Q-Q plots and histograms. Continuous variables without normal distributions were described using means and 95% confidence intervals or median and interquartile ranges (IQR) if not, and categorical variables were presented as frequencies and percentages. The primary outcome was VAS pain in 2^nd stage recovery right before hospital discharge. Between group comparisons for ACB vs LIA and for individual demographic variables (males vs females,) and procedural variables (primary vs revision surgeries, patellar vs hamstring tendon autograft, and meniscectomy vs meniscal repair) were analyzed with independent two-tailed t-tests for normally distributed continuous variables or Wilcoxon Rank Sum tests if not, and chi-square tests for categorical variables. The proportion of participants with mild, moderate, severe or no pain at one-week post-op was compared between groups using the exact test as well as the Cochrane-Armitage test to assess for potential between-group differences in pain severity trend. Hospital recovery times (time in PACU, 2^nd stage recovery, and total time to discharge) and post-op KOOS pain were not normally distributed and were evaluated with the Wilcoxon rank-sum test. Due to baseline differences in age and previously reported risk factors for higher postoperative pain¹⁷, patients were also matched by age, sex, BMI, graft type (hamstring autograft, bone-patellar-bone autograft, other), meniscal treatment (meniscal repair, partial meniscectomy/debridement, no treatment) in sub-analyses, and between-group differences in pain scores and MME totals were evaluated using independent t-tests. Propensity score matching was completed using a greedy 1:1 match with a caliper width of 0.2 standard deviations. Analyses were completed using SAS statistical software version 9.4 (SAS Institute, Inc., Cary, NC).

Results

In total, 426 total ACLR procedures were reviewed, and 265 knees (263 patients) were included (LIA, 157 knees; ACB, 108 knees). There were 161 knees excluded for receiving an alternate nerve block or not receiving LIA. The mean age of patients in the ACB group was significantly older than the LIA group (27.5 (25.5-29.5)vs. 23.4 (21.9-24.9), p=0.002). There was also a higher proportion of overweight patients¹⁸ in the ACB group (BMI ≥25 kg/m²: 61.1% vs. 47.8%, p=0.033). A higher proportion of patellar tendon autografts were used in the LIA group (46.5% vs. 31.5%, p=0.014), while a higher proportion of hamstring tendon autografts were used in the ACB group (58.3% vs. 45.8%, p=0.036). In addition, the percentage of patients who received concurrent partial meniscectomy was significantly higher in the ACB vs. LIA group (50% vs 33.8%, p=0.008) (Table 1).

Table 1.

Baseline Characteristics

	LIA (n=157)	ACB (n=108)	P-value
Knees, n (%)	157 (59.2)	108 (40.7)	-
Male sex, n (%)	80 (51.0)	54 (50)	0.879
Age (years) (95% CI)	23.4 (21.9-24.9)	27.5 (25.5-29.5)	0.002
Age > 25 (n, %)	44 (28.0)	48 (44.4)	0.006
BMI (kg/m2) (95% CI)	25.8 (24.9-26.6)	26.5 (25.5-27.4)	0.277
BMI ≥25 (n, %)	75 (47.8)	66 (61.1%)	0.033
Race, n (%)			0.098
Caucasian	147 (93.6%)	92 (85.2%)
Black/AA	2 (1.3%)	4 (3.7%)
Asian	2 (1.3%)	7 (6.5%)
Other	6 (3.8%)	5 (4.6%)
Smoking status, n (%)			0.099
Current	7 (4.4)	4 (3.7)
Former	4 (2.5)	9 (8.3)
Never	146 (92.9)	95 (88.0)
Surgeon			<0.0001
1	137 (87%)	29 (27%)
2	0	9 (8%)
3	0	28 (26%)
4	20 (13%)	42 (38%)
Operative side, n (% right)	75 (47.8)	57 (52.8)	0.423
Revision ACLR, n (%)	29 (18.5)	13 (12.0)	0.152
Graft Type, n (%)
Bone-patellar-bone	73 (46.5)	34 (31.5)	0.014
Hamstring tendon	72 (45.8)	63 (58.3)	0.036
Quadriceps tendon	12 (7.64)	8 (7.4)	0.943
Ant. tibialis allograft	0	3 (2.8)	0.067
Concurrent Procedures*, n (%)
MCLR	4	1	0.340
LCLR	2	4	0.191
Meniscus Debridement	43 (27.4)	40 (37.0)	0.096
Partial Meniscectomy	53 (33.8)	54 (50.0)	0.008
Meniscal Repair	42 (26.8)	27 (25)	0.750
Meniscal Root Repair	12 (7.6)	3 (2.8)	0.092
MAT	0	1 (0.9)	0.408
Microfracture	11 (7.0)	6 (5.6)	0.636
Chondroplasty	15 (9.6)	4 (3.7)	0.070

Variables presented as mean (95% confidence interval) or frequency (n) and percentage (%). P-values in bold indicate statistical significance (p < 0.05).

LIA, Local infiltrative anesthesia. ACB, Adductor canal block. ACLR, Anterior cruciate ligament reconstruction. BMI, Body mass index. MCLR, Medial collateral ligament reconstruction. LCLR, Lateral collateral ligament reconstruction. MAT, Meniscal allograft transplant.

Early Postoperative Pain

All patients had VAS pain scores from hospital recovery available for analysis. VAS pain scores did not significantly differ upon PACU admission, PACU discharge, or 2^nd stage recovery discharge (2^nd stage discharge VAS pain, mean(95%CI): LIA 2.6 (2.4-2.8) vs. ACB 2.4 (2.1-2.7), p= 0.339) (Table 2).

Table 2.

Comparison of post-operative pain and opioid use after ACL reconstruction

	LIA (n=157)	ACB (n=108)	P-value
VAS Pain - Hospital Recovery 1
PACU Admission	4.3 (3.9-4.8)	4.4 (3.9-4.9)	0.916
PACU Discharge	3.6 (3.4-3.9)	3.5 (3.2-3.8)	0.853
2nd Stage Discharge	2.6 (2.4-2.8)	2.4 (2.1-2.7)	0.340
Delta VAS	1.7 (1.3-2.2	2.0 (1.5-2.5)	0.255
VAS Pain – TelephoneFollow-up
No pain (0)	26 (22.2)	13 (16.7)	Overall: 0.441
Mild (1-3)	60 (51.3)	39 (50)	Trend2: 0.185
Moderate (4-7)	31 (26.5)	25 (32.1)
Severe (8-10)	0 (2.6)	1 (1.3)
Total MME, n (%)	17.6 (16.4-18.8)	18.5 (17.2-19.8)	0.134
KOOS Pain Score 3	Pre-op: 67.8 (64.9-70.6)	Pre-op: 63.3 (59.7-66.8)	0.044
	6-week: 78.2 (76.1-80.3)	6-week: 76.6 (74.0-79.3)	0.250
	Delta: 10.3 (7.3-13.4)	Delta: 13.6 (10.1-17.1)	0.070

¹Mean (95% confidence interval) VAS scores, Delta = PACU Admission VAS – 2^nd stage Discharge VAS.

²Results of Cochrane-Armitage test to assess for potential between-group differences in pain severity trend.

³Mean Knee Injury and Osteoarthritis Outcome Score (KOOS) pain scores at baseline (pre-op) and 6-weeks.

LIA, Local Infiltrative Anesthesia. ACB, Adductor canal block. VAS, Visual Analog Scale. PACU, Post-anesthesia care unit. MME, Milligram morphine equivalent. Delta VAS = 6-week score - pre-operative score.

In total, 73.6% of participants (knees) had VAS pain scores available from day-after discharge telephone follow-up interviews. VAS pain scores reported during phone interviews were not significantly different (p=0.441). In addition, 96.6% of patients had 6-week follow-up KOOS pain scores available. The ACB group reported a lower preoperative KOOS pain score (ACB, mean(95%CI): 63.3 (59.7-66.8) vs LIA 67.8 (64.9-70.6), p=0.044), but the amount of improvement in KOOS pain scores at 6 weeks did not differ between groups (LIA, mean(95%CI): 10.3 (7.3-13.4) vs. ACB 13.6 (10.1-17.1), p=0.070) (Table 2). Twenty-six patients (17.3%) in the LIA group achieved PASS for KOOS pain at 6 weeks, compared to 15 patients in the ACB group (14.4%, p=0.535). In the LIA group, 46 patients (30.9%) reached the MIC for KOOS pain at 6 weeks compared to 44 patients (42.7%) in the ACB group (p=0.054).

Recovery Times

The median time to discharge (PACU + 2^nd stage recovery time) did not significantly differ between groups (LIA: 137.5 (IQR:116-178) vs. ACB: 147 (IQR:123-183) minutes), p=0.118) (Table 3).

Table 3.

Comparison of hospital recovery times

	LIA	ACB	P-Value
PACU Time	68 (54-88)	72 (56-88)	0.454
2nd Stage Recovery Time	75 (60-100)	67.5 (53-93)	0.094
Total Time to Discharge	137.5 (116-178)	147 (123-183)	0.118

Data presented as Median with Interquartile range (minutes).

LIA, Local infiltrative anesthesia. ACB, Adductor canal block. PACU, Post-anesthesia care unit. Total time to discharge = PACU + 2^nd Stage Recovery.

Matched Sub-Analysis of LIA vs. ACB

Ninety-four patients remained in LIA and ACB groups after matching for age, sex, BMI, graft type, and meniscal treatment (Table 4). VAS pain at the time of 2^nd stage discharge was equivalent (LIA, mean(95% CI): 2.4 (2.1-2.7) vs ACB: 2.7 (2.4-3.0), p=0.134). Patients in the ACB group reported lower pre-op KOOS pain scores (ACB, mean(95% CI): 62.8 (59.0-66.7) vs. LIA 68.3 (64.9-71.7), p= 0.037), but no other significant differences were found (Table 4).

Table 4.

Matched comparison of LIA and ACB groups

	LIA (n=94) Mean(95%CI)	ACB (n=94) Mean(95%CI)	P-value
PACU Admission VAS Pain	4.4 (3.8-4.9)	4.3 (3.7-4.9)	0.875
PACU Discharge VAS Pain	3.5 (3.1-3.8)	3.8 (3.5-4.1)	0.164
2nd Stage Discharge VAS Pain	2.4 (2.1-2.7)	2.7 (2.4-3.0)	0.134
Delta VAS	2.0 (1.4-2.6)	1.6 (1.0-2.2)	0.367
Total MME	18.6 (17.2-20.0)	17.9 (16.4-19.4)	0.520
VAS Pain – Telephone Follow-up
n available	51	51
			0.530
No pain (0)	11 (21.6%)	10 (19.6%)	Trend:0.385
Mild (1-3)	29 (56.9%)	25 (49.0%)
Moderate (4-7)	11 (21.6%)	16 (31.4%)
Severe (8-10)	0	0
KOOS Pain – Pre-op	68.3 (64.9-71.7)	62.8 (59.0-66.7)	0.037
KOOS Pain – 6 weeks	75.8 (72.7-78.8)	77.1 (74.3-79.9)	0.563
KOOS Improvement	13.6 (9.7-17.6)	9.4 (5.5-13.4)	0.153

Results of matched comparison of LIA and ACB group.

LIA, Local infiltrative anesthesia. ACB, Adductor canal block. VAS, Visual Analog Scale. KOOS, Knee Injury and Osteoarthritis Outcome Score.

Discussion

The principal finding of this study was that using both LIA and ACB as long-acting regional anesthesia for ACLR were associated with similar postoperative pain levels and total opioid consumption in the immediate postoperative period. The results of overall and matched-group comparisons revealed VAS pain scores did not significantly differ at all timepoints, including at the time of PACU admission, hospital discharge, and up until 5 days postoperatively. Pain levels and recovery times were similar despite including patients with other concomitant pathology. Patients also received different type of grafts, the majority being bone-patellar-bone and hamstring tendon autografts. After controlling for various baseline differences (age, BMI, sex, type of autograft and meniscal treatment) between overall groups, we found that patients who received LIA reported similar VAS pain levels before hospital discharge. Patients also reported similar pain levels during day-after discharge telephone follow-up. Preoperatively, those in the ACB group reported lower KOOS pain scores (higher pain). A higher proportion of patients in the ACB group reached MIC for KOOS pain at 6 weeks (42.7% vs. 30.9%), but this difference did not reach statistical significance (p=0.054). The proportion of patients who achieved PASS for KOOS pain at 6 weeks was similar (LIA 17.3% vs. ACB 14.4%, p=0.535). Furthermore, the results from our matched sub-analysis suggest outcomes measuring pain (2^nd stage VAS pain, total MME, delta-VAS, and KOOS pain) were similar between the two study groups.

Regional ACB’s for outpatient knee surgery were introduced as an alternative to FNB due to reports of quadriceps weakness and increased risk of falls.^{9, 19, 20} However, quadriceps weakness can also occur after an ACB; if the local anesthestic is not injected in the midportion of the adductor canal, motor weakness of the quadriceps (via the nerve to vastus medialis) or foot and ankle weakness (via the sciatic nerve) could inadvertently occur.^{8, 9, 19, 20} Persistent postoperative quad strength asymmetry after ACLR can potentially impede recovery and negatively influence the ability to safely return to sports.²¹ Although functional outcomes were not evaluated in this study, our outcomes suggest that using a postoperative peri-articular LIA produces similar postoperative pain relief as ACB, presumably without risking femoral nerve palsy and related motor deficits.

Early studies of periarticular LIA of the knee report that it provides more effective analgesia in comparison to placebo.¹⁰ In a recent randomized controlled trial, Stebler et al.¹³ compared ACB versus LIA for regional anesthesia after ACLR, and they also found patients in both treatment groups had equivalent postoperative pain. The choice between the two techniques did not impact functional outcomes up to 8 months after surgery. However, all of the patients in the trial received hamstring autografts for isolated ACLR, and they performed the ACB in the operating room after surgery. Additionally, the preparation of the LIA injection differed between our studies. The volume and number of active constituents of the LIA injection used in the present study is higher than other preparations described in the literature.^{11, 12} There is variability reported for LIA injection volume (20 – 350 mL) as well as the type and number of additives (i.e., morphine vs. fentanyl, corticosteroids vs. non-steroidal anti-inflammatories).¹¹ Despite these differences in study design and LIA injection, the results from our study align with their findings.

There are additional considerations when deciding between regional ACB versus periarticular LIA, including adequate training in ultrasound guided ACB procedures. For an adequate block, it is essential to use ultrasound guidance, so that local anesthetic can fill up the narrow adductor canal to properly anesthetize the saphenous nerve and nerve to vastus medialis. This procedure is typically performed by an anesthesiologist. Furthermore, a recent randomized trial also found that no difference in post-operative pain scores between an ACB performed using ropivacaine and an ACB performed using saline.²² In the absence of adequate training or hospital resources, periarticular LIA may be more appropriate to use for early postoperative pain control. In addition, time spent outside of the operating room potentially increases with preoperative ACB, which can increase cost. These associated factors may limit more widespread use of ACB’s as regional anesthesia for ACLR surgery. Future studies comparing the efficacy of ACB versus LIA should aim to evaluate time spent outside of the operating room, and they could assess whether an ACB combined with LIA results in additional pain relief to an ACB or LIA alone. Surgeons may weigh the benefits and risks of each pain control method with patients when deciding on optimal pain control after ACLR.

Limitations

The present study has several limitations in addition to its retrospective nature. Postoperative pain levels and opioid consumption were not compared to placebo. Therefore, we cannot conclude that pain levels and total postoperative MMEs were decreased with either ACB or LIA. Since the patients included were treated by four orthopedic surgeons, criteria for choosing an ACB vs. LIA were not standardized. There was also a baseline difference in the distribution of patients treated between the four surgeons. These factors may confer possible selection bias, but since the sample size was relatively small, we did not feel an analysis of potential surgeon impact on the results would have provided meaningful results. This study also did not evaluate for differences in postoperative functional recovery between groups. Conclusions regarding post-operative pain in patients with concomitant pathology (collateral ligament repair, meniscus repair, etc.) also could not be definitively made due to insufficient sample sizes. Possible performance and recording bias exist as information regarding how many clinicians performed the adductor canal blocks as well as who recorded PACU pain scores was not collected. Also, data regarding the timing of post-operative phone calls was not collected. There is some risk of transfer bias because not all patients had VAS pain scores recorded after discharge. Other potential confounders that were not adjusted for also include the duration of surgery, tourniquet time, and intra-operative analgesia.

Conclusion

The use of ACB or LIA resulted in similar early pain levels, opioid consumption, and hospital recovery times after ACLR surgery.