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Ultrasound-Guided Adductor Canal Block Versus Intraoperative Transarticular Saphenous Nerve Block: A Retrospective Analysis

Published:February 18, 2022DOI:https://doi.org/10.1016/j.arth.2021.11.033

      Abstract

      Background

      The ultrasound-guided adductor canal block (High-ACB) is an effective option for pain control in total knee arthroplasty (TKA), but its use can add substantial cost and preparatory time to a TKA procedure. An intraoperative adductor canal block (Low-ACB) performed by the operative surgeon has been described as an alternative. The hypothesis of this study is that the Low-ACB would achieve noninferior pain control and opioid utilization postoperatively when compared to the High-ACB.

      Methods

      This is a retrospective study of a prospectively maintained database comparing the High-ACB vs the Low-ACB. The primary outcome measure was morphine milligram equivalents consumed. Secondary outcome measures included Visual Analog Scale pain scores, postoperative outcomes (Patient-Reported Outcome Measurement Information System, Knee Injury and Osteoarthritis Outcome Score, knee range of motion), length of stay, postoperative speed of mobilization, and complications related to the type of block.

      Results

      There were 139 patients in the study. There was lower opioid use in the first 24 hours in the Low-ACB compared to the High-ACB group respectively (26.3 vs 30, P = .29) but this did not reach statistical significance. There was a statistically significant difference in Visual Analog Scale score on postoperative day 1 in the Low-ACB vs High-ACB groups respectively (4.6 vs 3.7, P = .02) but this did not reach the level of clinical significance. There was no statistical difference in the Patient-Reported Outcome Measurement Information System, Knee Injury and Osteoarthritis Outcome Score, or postoperative range of motion. There were no block-related complications in either group.

      Conclusion

      The Low-ACB is a safe, effective, and cost-saving alternative to the traditional High-ACB for pain control in TKA.

      Keywords

      Modern total knee arthroplasty (TKA) has become a highly successful operation when treating patients with end-stage osteoarthritis [
      • Memtsoudis S.G.
      • Yoo D.
      • Stundner O.
      • Danninger T.
      • Ma Y.
      • Poultsides L.
      • et al.
      Subsartorial adductor canal vs femoral nerve block for analgesia after total knee replacement.
      ,
      • Sogbein O.A.
      • Sondekoppam R.V.
      • Bryant D.
      • Johnston D.F.
      • Vasarhelyi E.M.
      • MacDonald S.
      • et al.
      Ultrasound-guided motor-sparing knee blocks for postoperative analgesia following total knee arthroplasty: a randomized blinded study.
      ]. As the population of the United States continues to rise, so too does the number of projected TKA procedures performed annually [
      • Kurtz S.
      • Ong K.
      • Lau E.
      • Mowat F.
      • Halpern M.
      Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030.
      ]. Although outcomes and patient satisfaction continue to improve, there has been a great deal of recent interest in perioperative pain control [
      • Kurtz S.
      • Ong K.
      • Lau E.
      • Mowat F.
      • Halpern M.
      Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030.
      ,
      • Jenstrup M.T.
      • Jaeger P.
      • Lund J.
      • et al.
      Effects of adductor-canal-blockade on pain and ambulation after total knee arthroplasty: a randomized study.
      ,
      • Schumer G.
      • Mann 3rd, J.W.
      • Stover M.D.
      • Sloboda J.F.
      • Cdebaca C.S.
      • Woods G.M.
      Liposomal bupivacaine utilization in total knee replacement does not decrease length of hospital stay.
      ]. Toward this end, a variety of multimodal pain management strategies designed to disrupt the perception of pain via different mechanisms have been developed [
      • Dalury D.F.
      • Lieberman J.R.
      • MacDonald S.J.
      Current and innovative pain management techniques in total knee arthroplasty.
      ,
      • Kelley T.C.
      • Adams M.J.
      • Mulliken B.D.
      • Dalury D.F.
      Efficacy of multimodal perioperative analgesia protocol with periarticular medication injection in total knee arthroplasty: a randomized, double-blinded study.
      ]. In addition to the combination of oral and intravenous (IV) pain medications and anti-inflammatories, spinal anesthesia, peripheral nerve blocks, and periarticular injection protocols have dramatically improved perioperative pain control [
      • Dalury D.F.
      • Lieberman J.R.
      • MacDonald S.J.
      Current and innovative pain management techniques in total knee arthroplasty.
      ,
      • Kapoor R.
      • Adhikary S.D.
      • Siefring C.
      • McQuillan P.M.
      The saphenous nerve and its relationship to the nerve to the vastus medialis in and around the adductor canal: an anatomical study.
      ,
      • Perlas A.
      • Kirkham K.R.
      • Billing R.
      • Tse C.
      • Brull R.
      • Gandhi R.
      • et al.
      The impact of analgesic modality on early ambulation following total knee arthroplasty.
      ,
      • Wang Y.
      • Klein M.S.
      • Mathis S.
      • Fahim G.
      Adductor canal block with bupivacaine liposome versus ropivacaine pain ball for pain control in total knee arthroplasty: a retrospective cohort study.
      ].
      While effective, some of these modalities are not without their own set of limitations. Femoral nerve blockade provides reproducible pain relief to the anterior and medial aspect of the knee, but may miss the lateral and posterior aspects of the knee [
      • Memtsoudis S.G.
      • Yoo D.
      • Stundner O.
      • Danninger T.
      • Ma Y.
      • Poultsides L.
      • et al.
      Subsartorial adductor canal vs femoral nerve block for analgesia after total knee replacement.
      ,
      • Sogbein O.A.
      • Sondekoppam R.V.
      • Bryant D.
      • Johnston D.F.
      • Vasarhelyi E.M.
      • MacDonald S.
      • et al.
      Ultrasound-guided motor-sparing knee blocks for postoperative analgesia following total knee arthroplasty: a randomized blinded study.
      ,
      • Pepper A.M.
      • North T.W.
      • Sunderland A.M.
      • Davis J.J.
      Intraoperative adductor canal block for augmentation of periarticular injection in total knee arthroplasty: a cadaveric study.
      ,
      • Koh I.J.
      • Choi Y.J.
      • Kim M.S.
      • Koh H.J.
      • Kang M.S.
      • In Y.
      Femoral nerve block versus adductor canal block for analgesia after total knee arthroplasty.
      ,
      • Wang Q.
      • Yue Y.
      • Li D.
      • Yang Z.
      • Yeersheng R.
      • Kang P.
      Efficacy of single-shot adductor canal block combined with posterior capsular infiltration on postoperative pain and functional outcome after total knee arthroplasty: a prospective, double-blind, randomized controlled study.
      ]. Femoral nerve blockade may also cause quadriceps weakness which can delay mobilization and increase the risk of postoperative falls [
      • Memtsoudis S.G.
      • Yoo D.
      • Stundner O.
      • Danninger T.
      • Ma Y.
      • Poultsides L.
      • et al.
      Subsartorial adductor canal vs femoral nerve block for analgesia after total knee replacement.
      ,
      • Sharma S.
      • Iorio R.
      • Specht L.M.
      • Davies-Lepie S.
      • Healy W.L.
      Complications of femoral nerve block for total knee arthroplasty.
      ]. The adductor canal block (ACB) was developed to mitigate the motor sequelae of femoral nerve blocks [
      • Lund J.
      • Jenstrup M.T.
      • Jaeger P.
      • Sorensen A.M.
      • Dahl J.B.
      Continuous adductor-canal-blockade for adjuvant post-operative analgesia after major knee surgery: preliminary results.
      ]. Recent anatomic studies have demonstrated the presence of some motor branches to the vastus medialis within the adductor canal [
      • Pepper A.M.
      • North T.W.
      • Sunderland A.M.
      • Davis J.J.
      Intraoperative adductor canal block for augmentation of periarticular injection in total knee arthroplasty: a cadaveric study.
      ,
      • Lund J.
      • Jenstrup M.T.
      • Jaeger P.
      • Sorensen A.M.
      • Dahl J.B.
      Continuous adductor-canal-blockade for adjuvant post-operative analgesia after major knee surgery: preliminary results.
      ,
      • Shah N.A.
      • Jain N.P.
      Is continuous adductor canal block better than continuous femoral nerve block after total knee arthroplasty? Effect on ambulation ability, early functional recovery and pain control: a randomized controlled trial.
      ]. Study results have been mixed, but there has been found to be up to an 8%-9% rate of quadriceps weakness [
      • Jenstrup M.T.
      • Jaeger P.
      • Lund J.
      • et al.
      Effects of adductor-canal-blockade on pain and ambulation after total knee arthroplasty: a randomized study.
      ,
      • Koh I.J.
      • Choi Y.J.
      • Kim M.S.
      • Koh H.J.
      • Kang M.S.
      • In Y.
      Femoral nerve block versus adductor canal block for analgesia after total knee arthroplasty.
      ,
      • Lund J.
      • Jenstrup M.T.
      • Jaeger P.
      • Sorensen A.M.
      • Dahl J.B.
      Continuous adductor-canal-blockade for adjuvant post-operative analgesia after major knee surgery: preliminary results.
      ,
      • Shah N.A.
      • Jain N.P.
      Is continuous adductor canal block better than continuous femoral nerve block after total knee arthroplasty? Effect on ambulation ability, early functional recovery and pain control: a randomized controlled trial.
      ,
      • Jin S.Q.
      • Ding X.B.
      • Tong Y.
      • et al.
      Effect of saphenous nerve block for postoperative pain on knee surgery: a meta-analysis.
      ]. The ACB is typically performed under ultrasound guidance as a separate perioperative procedure, but this may add up to $2000 to the cost of a TKA [
      • Memtsoudis S.G.
      • Yoo D.
      • Stundner O.
      • Danninger T.
      • Ma Y.
      • Poultsides L.
      • et al.
      Subsartorial adductor canal vs femoral nerve block for analgesia after total knee replacement.
      ,
      • Sogbein O.A.
      • Sondekoppam R.V.
      • Bryant D.
      • Johnston D.F.
      • Vasarhelyi E.M.
      • MacDonald S.
      • et al.
      Ultrasound-guided motor-sparing knee blocks for postoperative analgesia following total knee arthroplasty: a randomized blinded study.
      ,
      • Perlas A.
      • Kirkham K.R.
      • Billing R.
      • Tse C.
      • Brull R.
      • Gandhi R.
      • et al.
      The impact of analgesic modality on early ambulation following total knee arthroplasty.
      ,
      • Wang Y.
      • Klein M.S.
      • Mathis S.
      • Fahim G.
      Adductor canal block with bupivacaine liposome versus ropivacaine pain ball for pain control in total knee arthroplasty: a retrospective cohort study.
      ,
      • Pepper A.M.
      • North T.W.
      • Sunderland A.M.
      • Davis J.J.
      Intraoperative adductor canal block for augmentation of periarticular injection in total knee arthroplasty: a cadaveric study.
      ,
      • Lund J.
      • Jenstrup M.T.
      • Jaeger P.
      • Sorensen A.M.
      • Dahl J.B.
      Continuous adductor-canal-blockade for adjuvant post-operative analgesia after major knee surgery: preliminary results.
      ,
      • Lee S.
      • Rooban N.
      • Vaghadia H.
      • Sawka A.N.
      • Tang R.
      A randomized non-inferiority trial of adductor canal block for analgesia after total knee arthroplasty: single injection versus catheter technique.
      ].
      Several authors have recently described an intraoperative ACB performed by the operating surgeon from within the joint [
      • Pepper A.M.
      • North T.W.
      • Sunderland A.M.
      • Davis J.J.
      Intraoperative adductor canal block for augmentation of periarticular injection in total knee arthroplasty: a cadaveric study.
      ,
      • Kavolus J.J.
      • Sia D.
      • Potter H.G.
      • Attarian D.E.
      • Lachiewicz P.F.
      Saphenous nerve block from within the knee is feasible for TKA: MRI and cadaveric study.
      ,
      • Greenky M.R.
      • McGrath M.E.
      • Levicoff E.A.
      • et al.
      Intraoperative surgeon administered adductor canal blockade is not inferior to anesthesiologist administered adductor canal blockade: a prospective randomized trial.
      ,
      • Peterson J.R.
      • Steele J.R.
      • Wellman S.S.
      • Lachiewicz P.F.
      Surgeon-performed high-dose bupivacaine periarticular injection with intra-articular saphenous nerve block is not inferior to adductor canal block in total knee arthroplasty.
      ]. To date, there have only been 2 published clinical studies comparing the efficacy of “High-ACB” performed under ultrasound guidance in the subsartorial adductor canal to “Low-ACB” performed intraoperatively through the existing arthrotomy [
      • Greenky M.R.
      • McGrath M.E.
      • Levicoff E.A.
      • et al.
      Intraoperative surgeon administered adductor canal blockade is not inferior to anesthesiologist administered adductor canal blockade: a prospective randomized trial.
      ,
      • Peterson J.R.
      • Steele J.R.
      • Wellman S.S.
      • Lachiewicz P.F.
      Surgeon-performed high-dose bupivacaine periarticular injection with intra-articular saphenous nerve block is not inferior to adductor canal block in total knee arthroplasty.
      ]. The literature has yet to reach a consensus on the effectiveness and safety of the Low-ACB block. The hypothesis of this study is that the Low-ACB will demonstrate noninferior postoperative pain control when compared to the more traditional High-ACB based on morphine equivalents.

      Methods

      This study is a retrospective analysis of a prospectively maintained database performed by 2 surgeons at a large academic hospital. Prior to initiating the study, Institutional Review Board approval was obtained by our institution’s Institutional Review Board. Consecutive adults over the age of 18 years of age scheduled to undergo elective primary unilateral TKA for osteoarthritis were enrolled between March 2020 and December 2020 and randomized to one of the 2 study groups. Exclusion criteria included >90 consecutive days of narcotic use in the 6 months prior to surgery, bilateral procedure, nonprimary arthroplasty, workman’s compensation status, inability to have spinal anesthesia, failure of attempted spinal anesthesia, inflammatory or post-traumatic arthritis, American Society of Anesthesiologists score of 4, and pregnancy [
      • Greenky M.R.
      • McGrath M.E.
      • Levicoff E.A.
      • et al.
      Intraoperative surgeon administered adductor canal blockade is not inferior to anesthesiologist administered adductor canal blockade: a prospective randomized trial.
      ,
      • Peterson J.R.
      • Steele J.R.
      • Wellman S.S.
      • Lachiewicz P.F.
      Surgeon-performed high-dose bupivacaine periarticular injection with intra-articular saphenous nerve block is not inferior to adductor canal block in total knee arthroplasty.
      ,
      • Saleh K.
      • Nelson C.
      • Kassim R.
      • Yoon P.
      • Haas S.
      Total knee arthroplasty in patients on workers' compensation: a matched cohort study with an average follow-up of 4.5 years.
      ,
      • Wilt Z.T.
      • Tan T.L.
      • Rondon A.J.
      • Wang W.L.
      • Foltz C.
      • Beredjiklian P.K.
      • et al.
      Preoperative sedative use and other risk factors for continued narcotic use after total knee arthroplasty: a comprehensive analysis of a mandatory database.
      ,
      • Oh T.K.
      • Jeon Y.T.
      • Choi J.W.
      Trends in chronic opioid use and association with five-year survival in South Korea: a population-based cohort study.
      ]. Patients who met inclusion criteria and agreed to participate were provided with detailed description of the risks, benefits, and alternatives to each intervention and gave signed informed consent during their preoperative clinic visit.

      Standard Perioperative Protocol

      All patients received the same perioperative regimen regardless of which arm of the study they were randomized to. Prior to leaving the preoperative area, all patients received 30 mg of IV ketorolac (15 mg if history of renal disease) and 1000 mg of oral acetaminophen. In the operating room (OR), standard monitoring equipment was used by anesthesia staff and a thigh tourniquet was applied. Patients received spinal anesthesia using 5-10 mL of 0.5% bupivacaine as well as 8 mg IV dexamethasone (4 mg in diabetic patients). Light sedative and anxiolytic agents (propofol and midazolam) were used at the discretion of anesthesia staff throughout the procedure. During the procedure, all patients received a cocktail described by Dalury et al [
      • Dalury D.F.
      • Lieberman J.R.
      • MacDonald S.J.
      Current and innovative pain management techniques in total knee arthroplasty.
      ] containing ropivacaine, epinephrine, ketorolac, and clonidine infiltrated in the posterior capsule and along the distal femur and proximal tibia. Postoperatively, patients received 30 mg (15 mg for patients older than 60 or with renal disease) IV ketorolac Q6 hours for 4 doses. Patients who discharged within 24 hours of surgery only received ketorolac until the time of discharge. Patients also received 1000 mg scheduled oral acetaminophen Q8 hours, tramadol 50 mg oral Q8 hours pro re nata, meloxicam 7.5 mg daily, and cryotherapy. Narcotics included oral oxycodone, hydrocodone/acetaminophen, or tramadol based on patient pain levels and medication allergies. Additionally, patients were given a proton pump inhibitor beginning 1 week prior to surgery until they were off all non-steroidal anti-inflammatory drugs and deep vein thrombosis prophylaxis, a probiotic also beginning 1 week preoperatively until 3 weeks postoperatively, and a stool softener (docusate) until off all narcotics.

      Randomization

      Patients were randomized in a consecutive grouped fashion. The first half of the patients operated on by each surgeon received the High-ACB. The second half of the patients operated on by each surgeon received the Low-ACB. This randomization method was chosen after discussion with the anesthesia department in order to prevent confusion and to prevent the possibility of a patient receiving both High-ACB and Low-ACB.

      Surgeon-Administered Group (Low-Adductor Canal Block)

      In the intraoperative cohort, the block was administered after the final components were in place and cement debris was removed. The knee joint was irrigated with dilute betadine followed by pulsatile lavage per institutional protocol. A periarticular and posterior capsular block was then administered as above. The location of the saphenous nerve as it exits the adductor canal was estimated to be 1.5× the transepicondylar axis proximal to the medial epicondyle in men and 1.3× the transepicondylar axis proximal in women as described by Kavolus et al [
      • Kavolus J.J.
      • Sia D.
      • Potter H.G.
      • Attarian D.E.
      • Lachiewicz P.F.
      Saphenous nerve block from within the knee is feasible for TKA: MRI and cadaveric study.
      ]. A blunt tip 1.5 in 18 gauge needle was then used to administer 15 cc of 0.5% ropivacaine. This was injected through the vastus medialis musculature in a field extending from 1 cm proximal to 1 cm distal to the assumed location of the nerve with the needle directed in approximately 30° laterally (Fig. 1, Fig. 2, Fig. 3, Fig. 4). The wound was then irrigated with pulsatile lavage one final time and closed in a layered fashion.
      Figure thumbnail gr1
      Fig. 1Surgeon measures medially one fingerbreadth above the anterior flange of the femoral component.
      Figure thumbnail gr2
      Fig. 2The needle is inserted down to the hub at the appropriate location and directed approximately 30° laterally.
      Figure thumbnail gr3
      Fig. 3The syringe is aspirated to ensure the needle has not violated the vasculature.
      Figure thumbnail gr4
      Fig. 4The contents of the syringe are emptied surrounding the saphenous nerve.

      Anesthesia-Administered Group (High-Adductor Canal Block)

      In the preoperative cohort, the ACB was administered by either board-eligible or board-certified anesthesia staff immediately prior to patient transport to the OR. This was a single shot, with no catheter left in place after the injection. The thigh was prepped with chlorhexidine at the midpoint between the anterior superior iliac spine and the patella and sterile drapes were applied. An ultrasound probe was then used to localize the adductor canal and confirm that the femoral artery, femoral vein, and saphenous nerve could be visualized deep to the sartorius. The probe was moved proximally or distally until the neurovascular bundle was centered under the sartorius. A 20 cc syringe with a blunt tip 1.5 in 18 gauge needle was then used to inject 15 cc of 0.5% ropivacaine. Following this, the wound was prepped and draped in usual sterile fashion for the arthroplasty procedure.

      Study Population

      One hundred forty patients were enrolled in the study and 1 patient was dropped due to the unsuccessful administration of spinal anesthesia. Patient enrollment began in March 2020 and was completed in December 2020. Seventy patients received the High-ACB and 69 patients received the Low-ACB. Patients were followed for 6 weeks postoperatively. There was no statistical difference in the demographics between the 2 study groups (Table 1).
      Table 1Patient Demographics Compared Between High-ACB and Low-ACB Cohorts.
      Patient DemographicsHigh-ACBLow-ACBP-Value
      Number of patients7069
      Gender.31
       Female71.0%63.0%
       Male29.0%37.0%
      Age (y)70.0 ± 8.071.5 ± 8.3.26
      BMI (kg/m2)31.3 ± 4.230.6 ± 4.9.38
      ASA score2.5 ± 0.52.4 ± 0.6.58
      Coronary artery disease29.0%27.1%.81
      Pulmonary disease36.2%25.7%.18
      Diabetes mellitus24.6%30.0%.48
      Chronic kidney disease8.7%10.0%.79
      ACB, adductor canal block; BMI, body mass index; ASA, American Society of Anesthesiologists.

      Outcomes

      The primary outcome measure was morphine equivalents of pain medicine consumed postoperatively. The time the patient arrived to the post-anesthesia care unit was recorded as time 0 for purposes of calculating narcotic utilization. Pain scores and narcotic utilization after discharge from the hospital were recorded by patients with the use of a pain journal. Patients were instructed to record their pain scores within 30 minutes of waking up in the morning beginning on the day after discharge home. Secondary outcomes included Visual Analog Scale pain scores (VAS), Knee Injury and Osteoarthritis Outcome Score, Patient-Reported Outcome Measurement Information System, distance walked in postoperative physical therapy, knee range of motion, and postoperative hospital length of stay. All patients were also monitored for any complications related to the block including falls, intravascular injection, and allergic reaction.

      Statistical Analysis

      A power analysis was performed prior to enrolling patients. Prior studies specifically evaluating narcotic utilization following ACB for TKA demonstrated a standard deviation of 20 mg of morphine equivalent consumption at 24 hours postoperatively [
      • Jenstrup M.T.
      • Jaeger P.
      • Lund J.
      • et al.
      Effects of adductor-canal-blockade on pain and ambulation after total knee arthroplasty: a randomized study.
      ,
      • Perlas A.
      • Kirkham K.R.
      • Billing R.
      • Tse C.
      • Brull R.
      • Gandhi R.
      • et al.
      The impact of analgesic modality on early ambulation following total knee arthroplasty.
      ,
      • Lee S.
      • Rooban N.
      • Vaghadia H.
      • Sawka A.N.
      • Tang R.
      A randomized non-inferiority trial of adductor canal block for analgesia after total knee arthroplasty: single injection versus catheter technique.
      ]. A 10 mg morphine equivalent reduction at 24 hours has been demonstrated to be clinically relevant and a previous noninferiority study of ACB in TKA has used 30 mg morphine equivalent as their noninferiority margin which we adopted as our cut off [
      • Lee S.
      • Rooban N.
      • Vaghadia H.
      • Sawka A.N.
      • Tang R.
      A randomized non-inferiority trial of adductor canal block for analgesia after total knee arthroplasty: single injection versus catheter technique.
      ]. Assuming a type I error rate of α = 0.05 and a type II error rate of β = 0.2 (80% power), a minimum sample size of 50 patients per group was needed. Due to the longitudinal nature of postoperative outcome measures and to account for loss to follow-up or incomplete data collection, we opted to recruit 70 patients per group for a total of 140 patients enrolled. This was to ensure an adequately powered cohort even with a 30% attrition rate.
      Patient characteristics were summarized using descriptive statistics for the Low-ACB and High-ACB groups, respectively. Numerical variables were presented as mean (standard deviation) or median (interquartile range), with t-test or Mann-Whitney U-test for comparison. Categorical variables were reported as percentages, with chi-squared test or Fisher’s exact test for comparison. t-Test and linear regressions were used to compare the postoperative narcotic utilization between the 2 groups of patients. Linear mixed-effect models were used to compare the pain score, knee function, and patient-reported outcomes between the 2 groups of patients over time. Statistical analysis was performed using SAS version 9.4 (SAS Institute, Cary, NC) and R version 4.0 (R-Foundation, Vienna, Austria).

      Results

      There was no statistical difference in the median 24-hour postoperative narcotic consumption between the High-ACB and Low-ACB groups (30 [7.5-46.9] Meq vs 26.3 [15-47.5] Meq, P = .29) (Table 2). The High-ACB group had significantly lower mean VAS pain score on postoperative day 1 (POD 1) compared to the Low-ACB group (3.7 vs 4.6, P = .02), but this did normalize on POD 2. There was no statistical difference between the groups with physical therapy participation on the day of surgery and the distance ambulated during the initial physical therapy visit. There was a statistically significant difference in length of stay, with the Low-ACB group discharging sooner (Table 3). There were no statistical differences in patient outcomes postoperatively (Table 4). There were no block-related complications in either study group.
      Table 2Narcotic and Visual Analog Scale Use Compared Between High-ACB and Low-ACB Cohorts.
      Narcotics Use and VAS Postoperative DayHigh-ACBLow-ACBP-Value
      Narcotics (24-h postop)30.0 (7.5-46.9) Meq26.3 (15-47.5) Meq.29
      VAS postoperative day 13.7 ± 2.04.6 ± 2.1.02
      Bolded values indicate statistical significance.
      VAS postoperative day 26.0 ± 1.85.3 ± 2.3.20
      ACB, adductor canal block; VAS, Visual Analog Scale.
      a Bolded values indicate statistical significance.
      Table 3Physical Therapy and Length of Stay Compared Between High-ACB and Low-ACB Cohorts.
      Physical Therapy Use, Feet Walked, and Length of StayHigh-ACBLow-ACBP-Value
      Physical therapy on day of surgery? (Yes)97.1%95.7%.99
      Feet walked during initial physical therapy visit126.5 ± 85.8145.6 ± 105.24
      Hospital length of stay<.01
      The Low-ACB block was performed on patients later in the study timeline. Departmental procedures regarding same-day discharge changed due to the COVID-19 pandemic, which likely accounts for the difference in hospital length of stay. Bolded values indicate statistical significance.
       0-23 h2.9%21.4%
       24-48 h85.5%71.4%
       >48 h11.6%7.1%
      ACB, adductor canal block.
      a The Low-ACB block was performed on patients later in the study timeline. Departmental procedures regarding same-day discharge changed due to the COVID-19 pandemic, which likely accounts for the difference in hospital length of stay. Bolded values indicate statistical significance.
      Table 4Patient-Reported Outcome Measures Compared Between High-ACB and Low-ACB Cohorts.
      PROMIS, KOOS, and ROM ParameterHigh-ACBLow-ACBP-Value
      PROMIS (Physical)
       Preoperatively42.1 ± 5.242.7 ± 6.5.85
       2-wk postoperatively43 ± 6.243.3 ± 6.7.92
       6-wk postoperatively46.9 ± 6.447.5 ± 6.8.68
      PROMIS (Mental)
       Preoperatively49.5 ± 6.248.6 ± 7.7.88
       2-wk postoperatively52.1 ± 6.653 ± 8.6.90
       6-wk postoperatively50.9 ± 6.152.9 ± 6.6.76
      Knee injury and Osteoarthritis Outcome Score
       Preoperatively48.7 ± 10.650 ± 12.4.78
       2-wk postoperatively63.7 ± 8.560.7 ± 10.68
       6-wk postoperatively68.5 ± 15.868.2 ± 12.90
      Range of motion
       Preoperatively100.8 ± 12.3102.2 ± 7.7.76
       2-wk postoperatively98.9 ± 16.698.4 ± 14.1.83
       6-wk postoperatively113.1 ± 13.8112.7 ± 12.3.74
      ACB, adductor canal block; PROMIS, Patient-Reported Outcomes Measurement Information System.

      Discussion

      The High-ACB is commonly utilized in TKA to improve pain control and reduce opioid use. Although it has been shown to be effective for pain relief, its use can lead to significantly increased costs for the patients, increased resources required, decreased efficiency for the surgical team, and a risk of quadriceps weakness. Depending on the institution and payment structures the High-ACB can increase costs from $1000 to $2000, which in the era of bundled payments is not insignificant [
      • Greenky M.R.
      • McGrath M.E.
      • Levicoff E.A.
      • et al.
      Intraoperative surgeon administered adductor canal blockade is not inferior to anesthesiologist administered adductor canal blockade: a prospective randomized trial.
      ]. The Low-ACB has been proposed as a low cost and efficient alternative to the High-ACB, while still effectively reducing pain. The technique used for the Low-ACB in our study is based on the descriptions from previous cadaveric and magnetic resonance imaging studies [
      • Pepper A.M.
      • North T.W.
      • Sunderland A.M.
      • Davis J.J.
      Intraoperative adductor canal block for augmentation of periarticular injection in total knee arthroplasty: a cadaveric study.
      ,
      • Kavolus J.J.
      • Sia D.
      • Potter H.G.
      • Attarian D.E.
      • Lachiewicz P.F.
      Saphenous nerve block from within the knee is feasible for TKA: MRI and cadaveric study.
      ]. This technique is efficient, low cost, and easily reproducible by the operative surgeon with a very simple learning curve.
      This study showed no statistical difference in narcotic consumption between the High-ACB and Low-ACB groups over the first 24 hours after surgery. The results did show a statistically significant lower VAS pain score for the High-ACB vs the Low-ACB on POD 1. Although this was statistically significant, the small actual difference (3.7 vs 4.6) does not reach the level of clinical significance of 1.2-1.3 difference as defined by the literature [
      • Gallagher E.J.
      • Liebman M.
      • Bijur P.E.
      Prospective validation of clinically important changes in pain severity measured on a visual analog scale.
      ,
      • Kelly A.M.
      The minimum clinically significant difference in visual analogue scale pain score does not differ with severity of pain.
      ]. The other secondary outcomes did not show any statistical differences except for the postoperative length of stay. The Low-ACB group did have a significantly shorter length of stay when compared to the High-ACB group. The data for this study were collected during the first year of the COVID-19 pandemic, and there were institutional and departmental changes regarding same-day discharge which did affect these results. Based on the nature of these changes though, they were not felt to have any effect on the other study parameters. The High-ACB data were collected on the first 70 patients of the study, and the Low-ACB data were collected on the subsequent 70 patients. Over this period of time the perioperative and postoperative protocols regarding early discharge did continue to evolve and improve. Based on these facts, while the improvement in early discharge is encouraging, it is not felt to be related to the block type.
      Our study is in agreement with the current literature regarding clinical comparisons of the Low-ACB and the High-ACB. Peterson et al retrospectively compared a surgeon-administered intra-articular saphenous nerve block and high-dose periarticular injection with an anesthesia-administered continuous adductor canal catheter. They found that the group with the surgeon-administered block had significantly lower pain scores and required fewer narcotic pain medications on the day of surgery. There was no difference in POD 1 pain scores, overall opioid use, length of stay, or complications. Greenky et al prospectively compared an anesthesia-administered with a surgeon-administered saphenous nerve block. This study found that opioid use was equal on POD 0, 1, or 2 between the groups. The group with the anesthesia-administered block did have statistically less pain on POD 1, but this did not reach clinical significance. Our study does have larger patient cohorts than any previously published study on this topic. Although this is a retrospective study, the database was maintained in a prospective manner.
      Our study does have several limitations. Although our database was prospectively maintained, this is a retrospective cohort study rather than a prospective randomized trial. In addition, we did not record VAS pain scores on POD 0 due to an inability to control for the time after surgery that it was recorded. We felt this could skew results if some patients had pain scores recorded while spinal anesthesia was still in effect. On the other hand, the duration of effect of ropivacaine when used peripherally is between 18 and 24 hours [
      • Sogbein O.A.
      • Sondekoppam R.V.
      • Bryant D.
      • Johnston D.F.
      • Vasarhelyi E.M.
      • MacDonald S.
      • et al.
      Ultrasound-guided motor-sparing knee blocks for postoperative analgesia following total knee arthroplasty: a randomized blinded study.
      ,
      • Koniuch K.L.
      • Buys M.J.
      • Campbell B.
      • Gililland J.M.
      • Pelt C.E.
      • Pace N.L.
      • et al.
      Serum ropivacaine levels after local infiltration analgesia during total knee arthroplasty with and without adductor canal block.
      ,
      • Jaeger P.
      • Grevstad U.
      • Koscielniak-Nielsen Z.
      • Sauter A.R.
      • Sørensen J.K.
      • Dahl J.B.
      Does dexamethasone have a perineural mechanism of action? A paired, blinded, randomized, controlled study in healthy volunteers.
      ]. Our first VAS pain score was recorded the morning after surgery and depending on the time of surgery and the length of effect of the ropivacaine it is possible that the ACB may no longer have an effect on pain control at that time. Another limitation is the fact that the patients who discharge home on the day of surgery recorded their own pain scores on POD 1. Based on patient compliance, the variability in VAS score collection could affect the data. Finally, our study was only powered to detect noninferiority of morphine equivalents. The strength of our data would be improved if the study was powered to detect differences in the other study parameters.

      Conclusion

      Based on these findings, the surgeon administered Low-ACB provides noninferior perioperative pain control relative to a more traditional anesthesia administered High-ACB based on morphine equivalents. Performing the block intraoperatively has the potential to substantially decrease OR turnaround time in institutions where the block was previously performed by anesthesia in the OR. Utilizing this technique may also be associated with substantial cost savings per TKA procedure.

      Appendix A. Supplementary Data

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