Saphenous Nerve Block Versus Femoral Nerve Block for Total Knee Arthroplasty

• The first secondary outcome is tracking total opioid usage. [ Time Frame: Up to postoperative day 4. ] [ Designated as safety issue: No ]
• The second secondary outcome is recording NRS pain scores. [ Time Frame: Up to postoperative day 4. ] [ Designated as safety issue: No ]
• The third secondary outcome is recording patient satisfaction with the nerve block. [ Time Frame: Up to 24 hours following administration of anesthesia. ] [ Designated as safety issue: No ]
• The fourth secondary outcome is rating the success of the nerve block. [ Time Frame: Up to 48 hours following administration of anesthesia. ] [ Designated as safety issue: No ]
• Another secondary outcome is tracking the duration of motor and sensory blockade. [ Time Frame: On average, up to 48 hours after administration of anesthesia. ] [ Designated as safety issue: No ]
• Another secondary outcome is tracking the incidence of postoperative complications (if any). [ Time Frame: Up to postoperative day 4. ] [ Designated as safety issue: No ]
• Another secondary outcome is tracking patients' ability to reach physical therapy milestones. [ Time Frame: Up to postoperative day 4. ] [ Designated as safety issue: No ]
• The final secondary outcome is total length of hospital stay (in hours). [ Time Frame: Up to postoperative day 4. ] [ Designated as safety issue: No ]

• Total morphine consumption [ Time Frame: On average, up to 4 days. ] [ Designated as safety issue: No ]
  Oral and IV opioids will be converted to oral morphine equivalents, then totaled.
• NRS pain scores [ Time Frame: On average, up to 4 days. ] [ Designated as safety issue: No ]
  Measured on a scale of 0-10
• Patient satisfaction with nerve block [ Time Frame: Up to 24 hours following administration of anesthesia. ] [ Designated as safety issue: No ]
  Patients will rate their satisfaction with their nerve blocks on a scale of 1 to 10, with 1=very dissatisfied and 10=very satisfied.
• Success of nerve block [ Time Frame: Up to 48 hours following administration of anesthesia. ] [ Designated as safety issue: No ]
  Rated as none, partial or complete.
• Duration of motor and sensory blockade [ Time Frame: On average, up to 48 hours after administration of anesthesia. ] [ Designated as safety issue: No ]
• Incidence of complications (if any) [ Time Frame: On average, up to 4 days. ] [ Designated as safety issue: No ]
  Including postoperative nausea and vomiting, neurologic symptoms and local anesthetic toxicity
• Ability to reach physical therapy milestones [ Time Frame: On average, up to 4 days. ] [ Designated as safety issue: No ]
• Total length of hospital stay (in hours) [ Time Frame: On average, up to 4 days. ] [ Designated as safety issue: No ]

Currently, the regional anesthetic standard of care for total knee replacement surgery is combined spinal/epidural, with or without a femoral nerve block, or FNB. Lasting approximately 18 hours, the FNB works by numbing the femoral nerve (and its branches), which is the major nerve controlling the knee joint. The femoral nerve also provides movement and sensation. While this regional anesthetic technique offers significant postoperative pain relief, it is possible that it may cause muscle weakness and increase patients' recovery time. Hence there is a need for an alternative technique, one that may help minimize postoperative pain as effectively as the FNB, while not causing weakness of the quadriceps muscle.

The saphenous nerve, a branch of the femoral nerve, provides sensation to the knee. Thus it is hypothesized that by "blocking" or anesthetizing the saphenous nerve with local anesthetic closer to where it branches off, the area around and below the knee will feel numb. Yet unlike with the FNB, the quadriceps muscle itself will still be able to function.

Patients will be randomized to receive FNB or saphenous nerve block. Quadriceps strength will be tested using a dynamometer before surgery (baseline), 6-8 hours following anesthesia administration, and on postoperative days 1 and 2. It is hypothesized that patients who receive FNB will experience a 50% decrease in quadriceps strength compared to baseline.

• Procedure: Study Group: Experimental
  The study group will receive the saphenous nerve block, at the level of the adductor canal. The block will be under ultrasound guidance. The local anesthetic will be 15 ml of 0.5% bupivicaine. The study group will also receive a combined spinal epidural, with 2.5 ml of 0.5% bupivacaine as the spinal agent. Additional drugs include anti-emetics, specifically Ondansetron (4 mg).
  Other Name: Saphenous (Adductor Canal) Nerve Block
• Procedure: Control Group
  The control group will receive the femoral nerve block. The block will be under ultrasound guidance. The local anesthetic will be 30 ml of 0.25% bupivicaine. The control group will also receive a combined spinal epidural, with 2.5 ml of 0.5% bupivacaine as the spinal agent. Additional drugs include anti-emetics, specifically Ondansetron (4 mg).
  Other Name: Femoral Nerve Block

• Experimental: Experimental
  Saphenous (Adductor Canal) Nerve Block
  Intervention: Procedure: Study Group: Experimental
• Active Comparator: Control
  Femoral Nerve Block
  Intervention: Procedure: Control Group

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Inclusion Criteria:

• All patients ages 18-90 undergoing primary unilateral total knee arthroplasty
• Planned use of neuraxial anesthesia
• Ability to follow study protocol
• American Society of Anesthesiology (ASA) Class 1-3

Exclusion Criteria:

• Contraindication to a spinal or epidural anesthetic
• Chronic opioid use (defined as daily or almost daily use of opioids for >3 months)
• Hypersensitivity and/or allergy to local anesthetics
• Intraoperative use of any volatile anesthetic
• Patients with a pre-existing neuropathy on the operative limb
• Contraindication to a femoral nerve block or saphenous nerve block
• Allergy to any of the study medications
• Non-English speaking patients