Saphenous Nerve Block Versus Femoral Nerve Block for Total Knee Arthroplasty

Not Applicable

Completed

Brief Summary: 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.

Recruitment & Eligibility

Inclusion Criteria

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

Arm && Interventions

Group	Intervention	Description
Control	Control Group	Femoral Nerve Block

Primary Outcome Measures

Name	Time	Method
Quadriceps Muscle Strength	48 hours following administration of anesthesia.	Measurements were made by a handheld dynamometer while patients perform isometric exercises. Results are presented in kilogram-force (kgF) units. One kgF is equal to 9.80665 N.

Secondary Outcome Measures

Name	Time	Method
Total Length of Hospital Stay	Total length of hospital stay
NRS Pain Scores at Rest	Postoperative day 4.	Patients rated pain on a scale of 0-10, with 0 representing no pain and 10 representing worst pain.
Total Opioid Usage	Postoperative day 4.	Opioid consumption data were collected and converted to oral morphine equivalents.
Patient Satisfaction With the Nerve Block.	24 hours following administration of anesthesia.	Patient satisfaction was measured on a 0-10 scale (0=not satisfied; 10=very satisfied).
Incidence of Postoperative Complications.	Postoperative day 4.