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Abstract

Background:

There is no pain management standard for anterior cruciate ligament reconstruction (ACLR) or one that addresses posterior capsule pain from hamstring autograft collection. IPACK (Infiltration of local anesthetic between the Popliteal Artery and Capsule of the Knee) is a novel peripheral nerve block designed as an analgesic for the posterior capsule. IPACK use has been beneficial in decreasing reported pain and medications needed for adult total knee arthroplasty; thus, it may be helpful for ACLR.

Hypothesis:

We hypothesized that adding IPACK to the adductor canal block (ACB) would decrease pain levels and opioids provided for adolescents who undergo ACLR with hamstring autografts as compared with local infiltration analgesia (LIA) or ACB only.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A retrospective chart review was conducted for 153 adolescent patients, aged 10 to 18 years, who underwent ACLR with hamstring autografts at a single hospital over 17 months. The type of regional block was determined by the surgeon’s preference, and patients received LIA only, ACB only, or IPACK + ACB. They were compared across these groups to identify the efficacy of each analgesic.

Results:

Patients across the entire cohort received a mean of 31.6 ± 12.9 morphine milligram equivalents (MME); the MME did not differ significantly based on regional blocks of LIA only, ACB only, and IPACK + ACB (P = .234). Pain levels in the postanesthesia care unit (PACU) were not significantly different from the first (P = .293), last (P = .845), highest (P = .816), or lowest (P = .235) pain scores. Patients who received both opioids and non-steroidal anti-inflammatory drugs (NSAIDs) received more MME than patients who only received opioids (10.7 ± 7.1 vs 7.8 ± 4) (P = .003) in the PACU but received similar MME overall (P = .38). In the PACU, patients who received opioids + NSAIDs had a higher highest pain score than those who received opioids only (7 ± 2.1 vs 5.5 ± 2.4) (P < .001).

Conclusion:

Overall, the amount of MME used at this institution was relatively low; however, the use of IPACK + ACB did not decrease opioid usage or pain levels after ACLR as compared with LIA or ACB only for the adolescent population. Use of any regional block was not superior to LIA for MME or reported pain levels. Given that IPACK + ACB did not decrease MME, it is not recommended to add an IPACK block for ACLR in adolescent patients.

Keywords

anesthesia techniques anterior cruciate ligament children IPACK pain management regional blocks

The standard of care for perioperative pain management in anterior cruciate ligament reconstruction (ALCR) has not been established, with adductor canal blocks (ACB), femoral nerve blocks, and local infiltration analgesics (LIA) used with variable efficacy.^1,24,31 The ACB provides coverage medially along the saphenous nerve, and the femoral nerve block covers the same, plus the anterior thigh; nonetheless, neither of these regional blocks assists in pain from hamstring autograft harvests.¹³ Alternatively, the IPACK (Infiltration of local anesthetic between the Popliteal Artery and Capsule of the Knee) focuses on the posterior knee capsule (Figure 1).

Figure 1.

An anterior view demonstrates ACB distribution on the left. The posterior view demonstrates IPACK distribution on the right. Adapted from Complete Anatomy. ACB, adductor canal blocks; IPACK, Infiltration of local anesthetic between the Popliteal Artery and Capsule of the Knee.

As the IPACK anesthetizes the posterior capsule—including the articular sciatic and obturator nerves—it could aid in providing improved postoperative analgesia by targeting some elements of the hamstring autograft harvest site. This is particularly important as hamstring autografts are still used in >50% of autograft ACLR surgeries for children with open or closing physes and at an equal frequency to quadriceps autografts.^3,26 Both the ACB and IPACK blocks are typically delivered to patients in a supine position, with their affected leg externally rotated, making it easy to add the IPACK without a large amount of time added to the operating room duration.

Early studies have found that the addition of IPACK to an ACB has been effective in pain management for total knee arthroplasty (TKA) in adults—including faster discharge and decreased usage of opioids.^30,32 Given that ACLRs occur in the same compartment, it is reasonable that IPACK will have improved analgesia for this operation as well. The ACB and IPACK combination has been seen in adult ACLR and an adolescent case series to significantly decrease pain in the first 3 days postoperatively.^17,20,21

ACLR block protocols still rely on oral analgesics after discharge, such as opioids and non-steroidal anti-inflammatory drugs (NSAIDs). It has been found that surgical pain management for ACLR is a frequent introduction to the medication class and increases the risk of opioid use disorders in adolescents.⁶ For the adolescent population, 4.8% of postoperative patients have persistent opioid use after the surgical event, in contrast to an opioid naïve population of children at¹² only 0.1%. With the ongoing opioid crisis, clinicians should be working to decrease prescriptions for these medications via more effective forms of perioperative analgesia.¹⁶

This study aimed to determine the benefits of adding an IPACK to the ACB regimen for hamstring autograft ACLRs using patients who had LIA as controls. The primary aim was to identify whether less narcotic was utilized perioperatively, with reduced calls to triage nursing for pain in the first week postoperatively. A secondary aim was to demonstrate that regional anesthesia produced fewer narcotic needs than a local infiltrate of anesthetic. We hypothesized that the ACB + IPACK would reduce narcotic utilization compared with ACB alone in the setting of ACLRs with hamstring autografts in adolescents.

Methods

After institutional review board approval, a retrospective review of patients managed at a single children’s hospital who underwent an arthroscopically assisted hamstring autograft ACLR between January 1, 2022, and June 12, 2023, was performed. Patients were identified using a search of the electronic medical records billing, as identified by the Current Procedural Terminology code 29888. Patients were excluded for the reasons outlined in Figure 2. Patients were not excluded for concurrent meniscal surgeries. The remaining patients were then placed into 1 of the 3 cohorts: LIA, ACB, and ACB + IPACK. IPACK was not used as a solo treatment arm given earlier TKA studies with IPACK used in conjunction with ACB, and it therefore had not been proven effective alone.

Figure 2.

Distribution of the exclusion criteria.

The surgeries were performed by 2 surgeons, one of whom used regional anesthesia (E.W.E.) and the other preferred LIA. Both surgeons had completed additional training in pediatric orthopaedics and sports medicine, with >13 years in practice. The LIA was performed with 20 to 40 mL of ropivacaine that was injected after the surgery but before the formal closure of the incisions. It was directed around each incision, and then within the overlying fascial planes involved in the surgery, being sure to inject along the hamstring harvest track. Effectively, the careful placement of local anesthetic during the LIA procedure was a peri-genicular block and not a regional block. Therefore, it was included as the primary control cohort for the present study. The other 2 regional blocks were performed by the anesthesiologist via ultrasound guidance at the start of the case after general anesthesia but before the onset of surgery. The standard of care at the start of the study collection period was ACB, but it switched to ACB + IPACK in the middle of the collection period. No randomization or choice of regional anesthesia was introduced, as much as a protocol shift within the anesthesia group. However, occasionally, some local ropivacaine was placed in the hamstring harvest site after an ACB, but not after ACB + IPACK per the anesthesiologist’s directive/preference. This local ropivacaine was placed before the closure of that incision.

The ACB was performed with the patient in the supine position, with the thigh abducted and externally rotated to allow access to the medial thigh with the ultrasound probe and needle. Under ultrasound visualization, the needle tip was placed just anterior to the femoral artery, deep to the sartorius muscle, and adjacent to the nerve. Infiltration of local ropivacaine (2 mg/mL) was undertaken until its spread around the artery was confirmed. The IPACK was completed similarly but at a different starting point, more distal on the thigh, wherein the needle was advanced within the interspace between the popliteal artery and femur until the needle tip extended 2 cm beyond the lateral border of the artery. Up to 40 mL of an amide local anesthetic was then deposited within the interspace as the needle was slowly withdrawn toward the skin. Some patients had additives of clonidine, dexamethasone, and/or dexmedetomidine in their nerve block, which was not analyzed as part of this study but may have had a small effect on analgesic duration.⁵

Data were retrospectively collected for all patients meeting the criteria at 3 time points: intraoperatively, post-anesthesia care unit (PACU) stay, and nurse triage line encounters. The time from the moment the patients entered the operating room until they were taken to the recovery room was recorded as the total case time. The tourniquet time was then recorded to be a close approximation of the surgical time (only excluding skin preparation and sterile dressing placement). The tourniquet time was then subtracted from the total case time to provide the nonoperative time, which included the anesthesia time (intravenous catheter placement, general anesthesia induction, and regional block, if performed), patient positioning, and patient transport to the recovery room. The duration of time to place the LIA was not discernible from the chart review.

The number of narcotics delivered during surgery and throughout the PACU stay was recorded. The morphine milligram equivalents (MMEs) were then calculated for each area and patient, as different medications were utilized based on the patient’s need and the anesthesia provider’s preferences.^8,23,33 The whole MME was utilized for comparisons, but another MME calculation was performed wherein the values of meperidine were excluded, as this medication was often delivered in the PACU for reasons unrelated to pain, such as shivering.²⁹ Other data points collected during the PACU stay included patient-reported PACU pain scores (first, last, highest, and lowest), and medication types and dosages (analgesics, antiemetics, and anxiolytics). ACLRs at this site are conducted as outpatient surgeries; thus, patients were not monitored after their PACU stay. The data recorded for the triage line in the first week included reasons for the call, and if pain-related, then the outcome of that call. Data on opioid usage and prescriptions after discharge were not recorded. Patient satisfaction was not assessed. Furthermore, self-reported data on sex, race, ethnicity, and body mass index (BMI) at the time of surgery were collected.

Basic descriptive statistics are presented. The unit of analysis was the patient. Continuous data were evaluated for normality using the Shapiro-Wilk test. All continuous data were found to be nonparametric and were evaluated with the Kruskal-Wallis H and the Mann-Whitney U tests. Categorical data were evaluated with the Pearson chi-square test. No a priori power analysis was performed. Statistical analysis was conducted using SPSS Version 28 (IBM). The threshold for statistical significance was set at P < .05.

Results

Out of 297 patients who underwent an ACLR during this period, 153 met the criteria. The mean age at surgery was 16.2 ± 1.5 years (range, 10.8-18.9 years), with a BMI of 25.2 ± 5.4 kg/m² (range, 16-42.4 kg/m²). The majority of our cohort were men (58%) and Caucasian (81%), with English being the primary language for 88% of the included patients. Cohort characteristics are demonstrated in Table 1.

Table 1

Cohort Characteristics by Regional Block^a

		No Regional	ACB Only	IPACK + ACB	Total
		(n = 31)	(n = 74)	(n = 48)	(n = 153)
Age, y	Mean ± SD	16.6 ± 1.3	16.2 ± 1.6	16 ± 1.4	16.2 ± 1.5
	Median	16.9	16.4	16.3	16.4
	Range	13.8 to 18.7	10.8 to 18.9	12.3 to 18.6	10.8 to 18.9
BMI, kg/m²	Mean ± SD	24.9 ± 4.5	24.8 ± 5.3	25.9 ± 6	25.2 ± 5.4
	Median	23.6	23.5	24.1	23.8
	Range	19-35.1	16-39.1	17.8-42.4	16-42.4
Sex, n (%)	Male	20 (65)	40 (54)	28 (58)	88 (58)
	Female	11 (35)	34 (46)	20 (42)	65 (42)
Race, n (%)	Asian	1 (3)	8 (11)	1 (2)	10 (7)
	Black	3 (10)	6 (8)	1 (2)	10 (7)
	Caucasian	27 (87)	53 (72)	44 (92)	124 (81)
	Mixed-other	0 (0)	7 (9)	1 (2)	8 (5)
	Not reported^b	0 (0)	0 (0)	1 (2)	1 (1)
Ethnicity, n (%)	Hispanic	14 (45)	29 (39)	20 (42)	63 (41)
	Non-Hispanic	17 (55)	44 (27)	27 (56)	88 (58)
	Not reported^b	0 (0)	1 (1)	1 (2)	2 (1)
Primary language, n (%)	English	29 (94)	65 (88)	41 (85)	135 (88)
	Non-English	2 (6)	9 (12)	7 (15)	18 (12)

ACB, adductor canal block; BMI, body mass index; IPACK, Infiltration between the Popliteal Artery and the posterior Capsule of the Knee.

Excluded from the race and ethnicity analysis.

Patients who identified as Asian had a significantly higher lowest PACU score (mean, 1.2 ± 1.8; range, 0-5) than Caucasians (mean, 0.2 ± 1; range, 0-6) (P < .001). Overall, patients who identified as Hispanic had a significantly higher BMI than non-Hispanic patients (mean, 26.6 ± 5.6 vs 24.1 ± 5 kg/m²) (P = .004). Hispanic patients made a similar number of pain-related phone calls to the nursing helpline compared with non-Hispanics (P = .697) but made fewer nonpain-related phone calls to the nurse helpline (P = .01). Of the 18 patients who did not speak English as their primary language, 16 (89%) made no nonpain-related phone calls to the nurse line, but 1 patient made 2 phone calls. Of the 135 patients who spoke English as their primary language, 88 (65%) made nonpain-related phone calls to the nurse line, with 3 patients making as many as 4 calls. This difference was not found to be statistically significant (P = .052). We also found no significant difference in the number of pain-related phone calls among English and non-English-speaking patients (P = .771).

The total case time and the tourniquet time for each of the analgesic procedures (LIA, ACB, and ACB + IPACK) are presented in Table 2. The duration of nonoperative time was significantly lower in the LIA cohort compared with both the ACB and ACB + IPACK cohorts (P < .001). The ACB + IPACK cohort had significantly longer nonoperative periods compared with the ACB-only cohort (P = .016).

Table 2

Anesthesia and Tourniquet Times by Regional Block^a

		No Regional	ACB Only	IPACK + ACB	Total
		(n = 31)	(n = 74)	(n=48)	(n = 153)
Total case time	Mean ± SD	102.8 ± 10	100.1 ± 12.2	107.2 ± 17.2	102.9 ± 13.9
min	Median	102	97.5	104	101
	Range	87-128	77-129	76-174	76-174
Tourniquet time	Mean ± SD	69.2 ± 9.8	55.8 ± 11.3	60.1 ± 15.4	59.9 ± 13.4
min	Median	68	56	57.5	58
	Range	45 to 94	36 to 85	35 to 120	35 to 120
Nonoperative time	Mean ± SD	33.7 ± 2.9	44.2 ± 5.7	47.2 ± 5.9	43 ± 7.6
min	Median	34	44	46	44
	Range	23-50	28-61	38-69	23-69

ACB, adductor canal block; IPACK, Infiltration between the Popliteal Artery and the posterior Capsule of the Knee.

Regarding peripheral nerve block composition, 112 patients received 0.2% ropivacaine while 11 received 0.125% or 0.25% bupivacaine with epinephrine. Moreover, 87 patients received 2 to 8 mL of dexamethasone, 63 received 20 to 100 mL of clonidine, and 9 received 20 to 40 mL of dexmedetomidine in their blocks. No patients who received LIA or ACB + IPACK reported posterior knee or saphenous nerve numbness at 1 week postoperatively. In the ACB-only cohort, 4 patients reported >1 month of saphenous nerve distribution paresthesia, inclusive of the length of the tibia. There were no significant differences in total MME dosage between the 3 cohorts (P = .234). The overall total MME mean was 31.6 ± 12.9 MME—including all 3 cohorts. There were no significant differences in the first (P = .293), last (P = .845), highest (P = .816), or lowest (P = .235) PACU pain scores between cohorts. Patients who underwent LIA had a higher time under tourniquet (mean, 69.2 ± 9.8 min; range, 45-94 min) than patients who received regional blocks (ACB only, mean 55.8 ± 11.3 min; range, 36-85 min; IPACK + ACB, mean 60.1 ± 15.4 min; range, 35-120 min) (P < .001). The distribution of MME and pain scores is presented in Table 3.

Table 3

Distribution of MME and Pain Score^a

		No Regional	ACB Only	IPACK + ACB	Total
		(n = 31)	(n = 74)	(n = 48)	(n = 153)
PACU MME w/o meperidine	Mean ± SD	9.2 ± 4.9	8.1 ± 6	8.1 ± 3.2	8.3 ± 5.1
	Median	8.66	8.1	8.2	8.3
	Range	0-23.6	0-42.26	0-14.62	0-42.26
PACU MME total	Mean ± SD	9.7 ± 5.1	8.6 ± 6.3	8.2 ± 3.2	8.7 ± 5.3
	Median	8.86	0.5	8.34	8.54
	Range	0-25.15	0-42.26	0-14.62	0-42.26
Anesthesia MME total	Mean ± SD	24.1 ± 11.4	22.5 ± 11.7	22 ± 11.9	22.9 ± 11.7
	Median	25	24.5	20	22
	Range	5 to 60	0 to 70	0 to 60	0 to 70
Total MME w/o meperidine	Mean ± SD	34.3 ± 14	30.6 ± 13	30.1 ± 11.7	31.2 ± 12.8
	Median	33.54	30.08	28.16	30
	Range	10-83.36	6.28-79.58	8.78-69.1	6.28-83.36
Total MME	Mean ± SD	34.7 ± 14.2	31.1 ± 13	30.2 ± 11.6	31.6 ± 12.9
	Median	33.54	30.4	28.16	30
	Range	10-83.86	6.28- 80.83	8.78-69.1	6.28- 83.36
Total antinausea, mg	Mean ± SD	7.8 ± 4.4	7.7 ± 3.8	8.2 ± 6.2	7.9 ± 4.7
	Median	4	8	6.75	8
	Range	4 to 19.9	4 to 14.7	0 to 40	0 to 40
First PACU pain score	Mean ± SD	0.7 ± 2	0.9 ± 2.2	04 ± 1.7	07 ± 2
	Median	0	0	0	0
	Range	0-9	0-8	0-8	0-9
The last PACU pain score	Mean ± SD	2.7 ± 1.7	2.8 ± 2.1	2.9 ± 1.8	2.8 ± 1.9
	Median	3	3	3	3
	Range	0-6	0-8	0-7	0-8
Highest PACU pain score	Mean ± SD	5.8 ± 2.5	6.1 ± 2.3	5.9 ± 2.5	5.9 ± 2.4
	Median	6	6.5	6	6
	Range	0-10	0-10	0-10	0-10
Lowest PACU pain score	Mean ± SD	0.3 ± 1.1	0.4 ± 1.3	0.1 ± 0.7	0.3 ± 1.1
	Median	0	0	0	0
	Range	0-5	0-6	0-5	0-6

ACB, adductor canal block; IPACK, Infiltration between the Popliteal Artery and the posterior Capsule of the Knee; MME, morphine milligram equivalence; PACU, postanesthesia care unit; w/o, without.

A total of 30% (46/153) of our cohort received NSAIDs in addition to opioids. The distribution of NSAIDs was similar among our 3 cohorts (P = .236). Patients who were administered opioids + NSAIDs were dosed with a higher MME in the PACU (mean, 10.7 ± 7.1; range, 0-42.3) compared with those who received opioids only (mean, 7.8 ± 4; range, 0-25.2) (P = .003). However, the 2 groups were similar in total MME (P = .38). The opioids + NSAIDs group had a higher highest PACU pain score (7 ± 2.1 vs 5.5 ± 2.4) (P < .001). There were no significant differences between opioids only and opioids + NSAIDs in the first PACU pain score (P = .786), the last PACU pain score (P = .397), the lowest PACU pain score (P = .743), or the number of postdischarge calls to the registered nurse (RN) for pain (P = .862). Additional information regarding the distribution of MMEs, pain scores, and phone calls broken down by whether or not the patient received NSAIDs is presented in Table 4.

Table 4

Distribution of MMEs, Pain Scores, and Phone Calls by the NSAID Group^a

		Opioids Only	Opioids + NSAIDs	Total
		(n = 107)	(n = 46)	(n = 153)
PACU MME w/o meperidine	Mean ± SD	7.5 ± 3.8	10.2 ± 6.8	8.3 ± 5.1
	Median	8	9.2	8.3
	Range	0-22.65	0-42.26	0-42.26
PACU MME total	Mean ± SD	7.8 ± 4	10.7 ± 7.1	8.7 ± 5.3
	Median	8.1	9.2	8.5
	Range	0-25.15	0-42.26	0-42.26
Anesthesia MME total	Mean ± SD	23.3 ± 10.1	21.9 ± 14.8	22.9 ± 11.7
	Median	25	20	22
	Range	5-60	0-70	0-70
Total MME w/o meperidine	Mean ± SD	30.8 ± 10.6	32.1 ± 17	31.2 ± 12.8
	Median	30.5	28.14	30
	Range	6.28-69.1	8.78-83.36	6.28-83.36
Total MME	Mean ± SD	31.2 ± 10.6	32.6 ± 17.1	31.6 ± 12.9
	Median	31.3	28.525	30
	Range	6.28-69.1	8.78-83.36	6.28-83.36
Total antinausea, mg	Mean ± SD	8.1 ± 5.1	7.2 ± 3.8	7.9 ± 4.7
	Median	8	4.75	8
	Range	4-40	0-14.7	0-40
First PACU pain score	Mean ± SD	0.7 ± 1.9	0.7 ± 2.2	0.7 ± 2
	Median	0	0	0
	Range	0-8	0-9	0-9
The last PACU pain score	Mean ± SD	2.7±1.9	3 ± 2	2.8 ± 1.9
	Median	3	3	3
	Range	0-8	0-7	0-8
Highest PACU pain score	Mean ± SD	5.5 ± 2.4	7 ± 2.1	5.9 ± 2.4
	Median	6	8	6
	Range	0-10	0-10	0-10
Lowest PACU pain score	Mean ± SD	0.3 ± 1	0.4 ± 1.3	0.3 ± 1.1
	Median	0	0	0
	Range	0-5	0-6	0-6
No. of pain calls to RN	Mean ± SD	0.1 ± 0.3	0.1 ± 0.5	0.1 ± 0.3
	Median	0	0	0
	Range	0-1	0-3	0-3
No. of nonpain calls to RN	Mean ± SD	0.5 ± 0.9	0.4 ± 0.9	0.5 ± 0.9
	Median	0	0	0
	Range	0-4	0-4	0-4

ACB, adductor canal block; IPACK, Infiltration between the Popliteal Artery and the posterior Capsule of the Knee; MME, morphine milligram equivalence; NSAID, non-steroidal anti-inflammatory drugs; PACU, postanesthesia care unit; RN, registered nurse; w/o, without.

Discussion

Adolescent patients undergoing ACLRs with hamstring autografts have options regarding perioperative analgesia via either local or regional infiltration of short-duration anesthetic.³¹ It appears that the delivery method of this anesthetic, whether as a local peri-geniculate block or true regional block in the form of ACB or ACB + IPACK, does not change the amount of MME utilized in the operating room or during the PACU stay (Table 3). Moreover, it does not appear to affect the number of nursing triage calls for pain during the early postoperative period. Therefore, not only do the outcomes of this study not support the hypothesis that the ACB + IPACK reduces narcotic utilization compared with ACB alone, but it also seems to indicate that a local infiltrate of anesthetic is similar to either regional anesthesia studied when placed throughout the surgical site.^19,25

The present study did identify a few factors that resulted in differences in the outcomes being measured. One of these was related to the ethnicity of the patient population. Although Hispanic patients did have a higher mean BMI, this did not affect their received analgesics or reported pain levels. Therefore, as BMI is most often associated with a higher percentage of adipose tissue in this age group, it appears that a higher BMI was not related to the block effectiveness. Moreover, Hispanics had a decreased number of nonpain-related calls to the nurse triage line. Race was also evaluated in this study, as there are known variations in pain management based on implicit biases. Nevertheless, the sample size of races other than Caucasian was small in this study, and thus, it was difficult to conclude race and pain management.² Despite the sample size issue, the present study did find that Asian patients had a higher lowest PACU pain score than Caucasian patients, meaning their pain was not as well controlled as other races. However, their final PACU score was the same as others before discharge home.

Although not a focus of the present study, some indication of complications related to the 3 anesthetic cohorts was evaluated. None of the patients who received an ACB + IPACK block reported posterior numbness at their initial follow-up visit, indicating that IPACK does not cause additional difficulties for patients in their first week postoperatively. This lack of functional deficits is consistent with IPACK findings for TKA.²⁷ There were a few patients in the ACB cohort who noted anterior saphenous nerve distribution numbness compared with none in the LIA cohort, indicating that there could be a residual effect on sensation function after infiltrating the major nerve branches during regional anesthesia. There is also mounting evidence that the ACB regional anesthesia— although intended to be improved related to femoral nerve blocks regarding motor control function—still may have some motor effects that inhibit early gains with quadriceps function.^7,34 These longer-term functional outcomes were not evaluated in the present study.

Another significant difference noted between anesthetic cohorts was a slight difference in tourniquet times (Table 2). Although this may be purely related to the surgeon’s technique or the presence of trainees, one of the differences between the cohorts was when the anesthetic was delivered to the patient. Given that the regional blocks were delivered before the tourniquet started, it would be reasonable to expect that the ACB and ACB + IPACK cohorts would have similar tourniquet times, which they did, as it did not include the time to deliver the regional anesthetic. The additional time needed to administer a higher volume of ropivacaine via the LIA technique could contribute to the few minutes that allowed for statistical and yet not likely clinically significant differences in tourniquet times. At the same time, the present study also noted a significant difference in the nonoperative time, with the LIA cohort having the shortest duration (Table 2). If all else is a constant between the cases, then the difference in these recorded durations should be the time it takes to place the regional block, 10 minutes for an ACB, and an additional 2 minutes for the IPACK. Much like the difference in tourniquet time, the duration of time for regional anesthesia placement, although statistically different, may not be clinically meaningful. These durations of pain management need to be weighed against the risks (possible saphenous nerve injury) and benefits (improved analgesia), especially considering that some studies (including this one) have found similar pain outcomes.^22,32

Interestingly, patients who received both opioids and NSAIDs had higher pain scores than patients who only received opioids (Table 4). The patients who received both forms of analgesics additionally received a higher total MME. It is unclear whether these patients were given more types of analgesics due to greater difficulty controlling pain, or whether the first line of pain management in our PACU was opiates, and then NSAIDs were added when pain remained relatively uncontrolled. Further studies would benefit from evaluating PACU analgesics in relation to standardized regional block protocols and by exploring the timing and chronological order of administered medications, especially as nonopioid analgesics have been seen to decrease the overall MME needed.^11,14 Moreover, a review of institutional pain management protocols could perhaps improve the number of opiates administered in the peri-anesthesia period.

The primary aim of this study was to evaluate the benefit of adding the IPACK to the ACB in the setting of hamstring autografts for ACLRs in adolescents. However, there was no association with MME usage between types of regional blocks. It is unclear whether this was due to opioids being delivered prophylactically after the surgery, regardless of pain experienced by the patient, or whether the IPACK block itself did not provide sufficient additional analgesia to comfortably decrease postoperative pain. Previous studies found that the use of regional blocks, such as ACB, decreased reported pain and opioid usage for adolescent ACLR.^11,15,18 The existing literature shows mixed results regarding opioid usage and pain levels (or both) with the use of IPACK.^22,28 Although these studies were predominately for TKA, it does support the idea that perhaps our institutional PACU opiate protocol limits our ability to test the efficacy of IPACK—either because our institution already limits the opiate use in the perioperative setting,^1,4,9,10 or that opiates are used for something other than pain management, such as in the case of meperidine. Per the Centers for Disease Control and Prevention guidelines, opioid-naive patients should receive <50 MME per day, notably higher than our total mean of 31.6 ± 12.9 MME. Another possibility is that age is a factor in the benefit of the IPACK, in that the older mean age in TKA affects the utility of that regional block compared with the younger age in the present cohort. Either way, as this study found no differences regarding the number of calls for pain to the nurse triage line in the week after surgery, it seems reasonable to conclude that LIA, ACB, and ACB + IPACK perform equally regarding pain management of adolescents who had ACLRs with hamstring autografts.

Limitations

Limitations of this study are related to the retrospective nature of the review. As discussed, there are some limits to understanding the need for opiates in either the perioperative period or the immediate postoperative period. As neither the pain management protocol of the anesthesiologist nor the PACU nursing staff was standardized, it is challenging to determine why perioperative opiates were given to each patient. This has influenced our institution to initiate a quality initiative to determine the best practices for the future care of adolescent patients. Future studies would benefit from a randomized clinical trial, standardized block composition, and standardized PACU medications to create clearer comparisons between groups.

Conclusion

In contrast to the proposed hypothesis, the addition of an IPACK did not affect postoperative patient-reported pain or the number of nurse triage phone calls as compared with ACB alone, or, interestingly, LIA. Future studies should focus on pain management with NSAIDs before using opioids in this youthful population undergoing ACLRs. With equivalency across anesthetic options seen in this study, it is reasonable to consider any of the options studied. However, although the IPACK appeared to be without complications, it does add to the general anesthesia time, even though it does not add to the tourniquet time, therefore, we recommend ACB over ACB + IPACK. While future studies will need to look at the longer-term follow-up outcomes related to motor function and sensation deficits, or the development of pain syndromes such as pain amplification or complex regional pain that may be related to these studied anesthetics, the present study indicates that the narcotic need in the perioperative timeframe and the first week postoperative is minimal as long as one of these options are utilized.

Footnotes

Final revision submitted November 4, 2024; accepted December 6, 2024.

One or more of the authors has declared the following potential conflict of interest or source of funding: E.W.E. has received support for education from Elevate Surgical; speaking fees from Arthrex; and research support from RTI Surgical. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Ethical approval for this study was obtained from the University of California, San Diego (192008).

ORCID iDs

Eric W. Edmonds

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