Adductor Canal Block for Total Knee Arthroplasty
Condition: Arthroplasty, Replacement, Knee; Pain, Postoperative
MeSH terms: Pain, Postoperative
Study type: Interventional

Summary: 
      Total knee arthroplasty (TKA) can be associated with a large amount of postoperative pain.
      This pain can oftentimes be severe enough to limit participation in physical therapy and
      ultimately delay discharge resulting in increased cost. Several strategies have been
      developed in an effort to decrease postoperative pain following TKA while maintaining lower
      extremity strength and maximizing participation in physical therapy. Recently, adductor canal
      blockade has gained popularity as it is reported to provide analgesia to the anterior knee
      without resulting in significant quadriceps muscle weakness. However, few studies have
      carefully evaluated the impact of volume of injection of local anesthetic into the adductor
      canal on motor weakness or pain control. The ability to achieve similar pain control with
      decreased volumes of local anesthetic would allow the surgery team to apply more local
      anesthetic to posterior knee structures. Decreased volumes of local anesthetic may also be
      associated with a decreased risk of local anesthetic toxicity. This study aims to carefully
      evaluate this relationship using a physical therapy evaluation method that relies on both
      motor strength and pain control. In addition, the investigators hope to carefully evaluate
      motor strength using a novel method of strength measurement in an effort to further evaluate
      the impact of volume of injection of local anesthetic into the adductor canal on motor
      strength.
    

Detailed description: 
      Postoperative analgesia for total knee arthroplasty (TKA) is incredibly important as it
      allows for effective physical therapy and ultimately ensures proper function of the implanted
      joint hardware. Unfortunately, TKA is oftentimes associated with pain severe enough to limit
      participation in physical therapy which can ultimately result in prolonged hospitalizations
      and perhaps decreased joint function. A number of strategies have been reported to decrease
      the pain associated with TKA. Opioids are commonly utilized but they can be associated with a
      number of potential side effects including nausea, itching, respiratory depression, tolerance
      and the potential for abuse. Epidural analgesia has been utilized for postoperative analgesia
      but this strategy requires urinary catheterization (potential source of increased incidence
      of urinary tract infections), causes significant vasodilation with resulting hypotension and
      can cause bilateral lower extremity weakness that can undermine efforts at early physical
      therapy and rehabilitation. Femoral nerve blockade and femoral nerve catheters have the
      potential to decrease pain in the anterior knee but use of this technique is limited by
      incomplete analgesia and quadriceps motor weakness. Some groups have advocated for the
      substitution or addition of sciatic or obturator nerve blocks to femoral nerve blockade but
      this is at the expense of increased lower extremity weakness and little potential clinical
      benefit.1-5

      In an effort to balance the need for effective postoperative analgesia with the need to
      maintain lower extremity muscle strength for active participation in physical therapy, a
      number of groups have begun to evaluate the adductor canal block. The adductor canal is
      located in the middle 1/3 of the thigh and includes the saphenous nerve and nerve to the
      vastus medialis. The primary advantage to adductor canal blockade versus femoral nerve
      blockade is a potential sparing of the nerves to the quadriceps muscle and therefore
      preservation of lower extremity motor strength.6-8 Kwofie et al reported in a study of 16
      volunteers that there was no change in quadriceps strength or hip adduction following the
      injection of 15 ml of local anesthetic. This is interesting as the obturator nerve is
      reported to travel within the adductor canal and is responsible for hip adduction. Kwofie et
      al also reported that SSACNB resulted in significantly decreased impairments with balance
      compared to a SSFNB.9

      To this point, the majority of studies evaluating adductor canal blockade have focused on
      continuous techniques and little has been done to evaluate single shot techniques. Continuous
      techniques have the potential to extend analgesia but this is at the expense of increased
      cost, effort, resource utilization and potentially increased risk of infection.

      The safety of CACNB technique was highlighted by a study by Henningsen et al where no cases
      of nerve injury related to analgesic technique were reported in a series of 97 patients.10
      Andersen et al compared a CACNB vs control in 40 patients and found that the intervention
      group reported decreased pain and sleep disturbances while retaining the ability to ambulate
      soon after surgery.11 Mudumbai et al evaluated 180 patients undergoing TKA and discovered
      that continuous adductor canal nerve blockade (CACNB) relative to continuous femoral nerve
      blockade (CFNB) resulted in greater ability to ambulate (37 m vs 6 m) on POD 1 and similar
      pain scores.8 Jaeger et al examined a similar group of 54 patients presenting for TKA and
      found that CACNB relative to CFNB resulted in decreased quadriceps weakness and no difference
      in pain, opioid consumption or weakness.12 Jenstrup et al reported that, compared to placebo,
      CACNB resulted in decreased pain with flexion and opioid consumption.13 Only recently has a
      study comparing SSACNB and SSFNB been published. This study demonstrated that SSACNB resulted
      in decreased postoperative quadriceps weakness and similar pain control to SSFNB.14 Of
      interest, previous research has demonstrated that 15 ml 0.5% ropivacaine is required to
      produce ultrasound guided femoral nerve blockade (including sensory and quadriceps motor
      weakness) but no such study has yet been done for the adductor canal block.15 It is possible
      that larger volumes of local anesthetic injected into the adductor canal could result in
      proximal spread of local anesthetic and increase quadriceps weakness and difficulty
      ambulating. It is also possible that decreased volumes of injection may result in inferior
      pain control and difficulties participating in physical therapy.
    

Intervention name(s): Adductor Canal Block; Adductor Canal Block
Intervention type(s): Procedure; Drug
Intervention description(s): Following negative aspiration, SSACNB volume will be randomized and subjects will receive 5, 10 or 20 ml of 0.5% bupivacaine will be incrementally injected. Randomization of the volume of bupivacaine will be determined by opening a sequential, pre-sealed envelope with the group assignment designated within. All studied volumes are well within the acceptable range for SSACNB.; Following negative aspiration, SSACNB volume will be randomized and subjects will receive 5, 10 or 20 ml of 0.5% bupivacaine will be incrementally injected. Randomization of the volume of bupivacaine will be determined by opening a sequential, pre-sealed envelope with the group assignment designated within. All studied volumes are well within the acceptable range for SSACNB.
Other intervention name(s): Bupivacaine
Intervention MeSH terms: Bupivacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Other
Keywords: Anesthesia; Analgesia