The purpose of this study is to compare the effects of a femoral nerve block vs. an adductor canal block on pain and quadriceps muscle strength for knee arthroscopy surgery.
Patients undergoing arthroscopic knee surgery (ACL and non-ACL surgery) typically receive an ultrasound-guided femoral nerve block or an adductor canal block in the pre-operative phase for post-operative pain control. While an effective method for post-operative analgesia, the femoral nerve block is associated with profound quadriceps weakness for the duration of the nerve block, which can impair ambulation, rehabilitation, and increase the risk of falls. The more distal adductor canal block, however, contains primarily sensory branches of the femoral nerve and has been been purported by small volunteer studies to provide equally effective analgesia with minimal motor block and quadriceps weakness (as compared to femoral nerve block). The investigators will prospectively randomize patients undergoing knee arthroscopy at the UCSF Orthopaedic Institute to receive either a single-shot femoral nerve or adductor canal block pre-operatively after taking baseline measurements of quadriceps strength (quantified by maximum voluntary isometric contraction). The quadriceps muscle strength will be checked 20 minutes after the nerve block to assess strength. All patients will subsequently undergo a general anesthetic. The primary outcome variable will be post-block quadriceps strength as a percentage of baseline from pre-block values. Secondary outcome variables that will also investigated include: VAS pain score in the post anesthesia recovery unit and post-operative day 1, duration of nerve blockade, and perioperative opioid consumption.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
132
Patients having ACL reconstruction, meniscus surgery and knee arthroscopy
Patients having ACL reconstruction, meniscus surgery and knee arthroscopy
UCSF Orthopedic Trauma Service
San Francisco, California, United States
Change in Quadriceps Strength Related to the Nerve Block
Quadriceps strength will be tested with a dynamometer before the nerve block and 20 minutes after the nerve block prior to surgery. The dynamometer measures the strength of the quadriceps muscles in the seated position while pushing against the device. We are trying to measure the effect of both femoral and adductor canal nerve blocks on quadriceps strength.
Time frame: Baseline and 20 minutes after the block prior to surgery
Numerical Pain Score From 0-10
As this is an outpatient surgery, we will collect Numerical Pain Scores from the recovery room medical record after surgery as well as from the patients for the first 24 hours after surgery by contacting them at home the following day. We will evaluate the difference in patient pain scores between the two nerve blocks under study. The highest pain score for the 24-hour post-op period was collected for each participant. The median is reported for all participants. A pain score of 10 represents the worst pain.
Time frame: worse pain in first 24 hours
Duration of Nerve Block
Patients will be contacted after surgery to determine when the nerve block wore off based on their increase in pain
Time frame: 8 to 24 hours
Opioid Consumption Reported at mg of Morphine Equivalence
Data on the amount of pain medication consumed for the 1st 24 hours after surgery will be collected based on medications that were administered during surgery, in the recovery room and medications that patients took at home after discharge from the recovery room. All pain medications will be converted to morphine equivalence in milligrams and reported that way. The comparison will be the difference in mg morphine equivalence consumption between the two nerve block groups.
Time frame: 2 days
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