Difference Between Femoral Nerve Block and Saphenous Block
Conditions
Keywords
Bilateral total knee replacement, Femoral Nerve Block, Saphenous Nerve Block
Brief summary
Currently, the regional anesthetic standard of care for total knee replacement surgery is combined spinal/epidural to provide long-lasting pain relief with or without a femoral nerve block (FNB). The femoral nerve block refers to a technique that your anesthesiologist can use to numb the thigh muscle for approximately 18 hours after surgery. While this technique offers significant pain relief, it is possible it may cause muscle weakness and increase patients' recovery times. Hence there is a need for an alterative anesthetic technique, one that may help minimize postoperative pain as effectively as a femoral nerve block, while not causing weakness of the thigh muscle. The saphenous nerve, a branch of the femoral nerve, provides sensation to the knee. Thus it is hypothesized 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 the femoral nerve block, the thigh muscle itself will still be able to function. For patients undergoing two total knee replacements at one time or bilateral total knee replacement, they will be randomly assigned to receive a femoral nerve block on one leg and a saphenous block on the other. Pain levels will be measured and thigh muscle strength will be tested using a dynamometer before surgery, 6-8 hours following anesthesia administration, and on postoperative days 1 and 2.
Interventions
PROCEDUREStudy Technique
One leg will receive the saphenous nerve block, at the level of the adductor canal (study technique). The block will be under ultrasound guidance. The local anesthetic will be 15 ml of 0.5% bupivacaine. All study patients, regardless of study arm will receive combined spinal epidural, with 3 ml of 0.5% bupivacaine as the spinal agent. Epidural local anesthetic, if needed, will consist of 2% lidocaine.
PROCEDUREControl Technique
The other leg will receive the femoral nerve block (control technique). The block will be under ultrasound guidance. The local anesthetic will be 30 ml of 0.25% bupivacaine. All study patients, regardless of study arm will receive combined spinal epidural, with 3 ml of 0.5% bupivacaine as the spinal agent. Epidural local anesthetic, if needed, will consist of 2% lidocaine.
Sponsors
Hospital for Special Surgery, New York
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
SUPPORTIVE_CARE
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
40 Years to 80 Years
Healthy volunteers
No
Inclusion criteria
* All patients ages 40-80 undergoing Bilateral Total Knee Replacement * Planned use of neuraxial anesthesia * Ability to follow study protocol
Exclusion criteria
* Contraindication to a spinal or epidural anesthestic * Not a candidate for bilateral total knee replacement * 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 pre-existing neuropathy on the operative limb * Contraindication to femoral nerve block or saphenous nerve block * Allergy to any of the study medications * American Society of Anesthesiologists (ASA) Class 4-5 * Non-English speaking patients
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Visual Analogue Scale Pain Score | Up to postoperative day 1 | The primary outcome is the postoperative pain in each leg within the first 24 hours postoperatively. VAS pain scores could range from 0 to 10. Higher values represent a worse outcome. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Tracking Total Opioid Usage | Up to postoperative day 2 | — |
| Preoperative and Postoperative Thigh Muscle Strength in Both Legs | Up to postoperative day 2 | This was measured with a dynamometer to gauge strength. |
| Patient Satisfaction With Nerve Blocks | Up to postoperative day 1 | Rated on a 0-10 scale, with a higher score representing greater satisfaction. |
| Duration of Motor and Sensory Blockade | Up to postoperative day 2 | — |
| Rating the Success of the Nerve Blocks | Up to postoperative day 2 | — |
| Postoperative Complications | Up to postoperative day 2 | — |
Countries
United States
Participant flow
Recruitment details
Recruitment was from the period of 4/16/12-9/4/13 at the Hospital for Special Surgery. Patients were identified on the day of surgery and randomized prior to the start of surgery.
Pre-assignment details
Patients were excluded prior to randomization if they had contraindications to spinal or epidural anesthesia, had chronic opioid use, pre-existing neuropathies in the limbs, allergies to pre-operative medications, contraindication to assigned nerve blocks, allergy to local anesthetic, American Society of Anesthesia 4-5, and non-English speaking.
Participants by arm
| Arm | Count |
|---|---|
| All Study Participants | 60 |
| Total | 60 |
Withdrawals & dropouts
| Period | Reason | FG000 | FG001 |
|---|---|---|---|
| Overall Study | Lost to Follow-up | 1 | 0 |
Baseline characteristics
| Characteristic | All Study Participants |
|---|---|
| Age, Customized Age | 64.41 years STANDARD_DEVIATION 7.36 |
| Region of Enrollment United States | 60 participants |
| Sex: Female, Male Female | 33 Participants |
| Sex: Female, Male Male | 27 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | — / — | — / — |
| other Total, other adverse events | 1 / 60 | 0 / 60 |
| serious Total, serious adverse events | 0 / 60 | 0 / 60 |
Outcome results
Primary
Visual Analogue Scale Pain Score
The primary outcome is the postoperative pain in each leg within the first 24 hours postoperatively. VAS pain scores could range from 0 to 10. Higher values represent a worse outcome.
Time frame: Up to postoperative day 1
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Study Technique: Saphenous Nerve Block | Visual Analogue Scale Pain Score | 2.81 units on a scale | Standard Deviation 2.42 |
| Control Technique: Femoral Nerve Block | Visual Analogue Scale Pain Score | 2.47 units on a scale | Standard Deviation 2.38 |
Secondary
Duration of Motor and Sensory Blockade
Time frame: Up to postoperative day 2
Population: The duration of motor and sensory blockade was not calculated and analyzed, because accurate data regarding block resolution time could not be acquired from patients.
Secondary
Patient Satisfaction With Nerve Blocks
Rated on a 0-10 scale, with a higher score representing greater satisfaction.
Time frame: Up to postoperative day 1
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Study Technique: Saphenous Nerve Block | Patient Satisfaction With Nerve Blocks | 8 units on a scale | Standard Deviation 2.4 |
| Control Technique: Femoral Nerve Block | Patient Satisfaction With Nerve Blocks | 8.4 units on a scale | Standard Deviation 2.3 |
Secondary
Postoperative Complications
Time frame: Up to postoperative day 2
Population: Analysis of postoperative complications was not performed because sufficient data could not be collected regarding the secondary outcome
Secondary
Preoperative and Postoperative Thigh Muscle Strength in Both Legs
This was measured with a dynamometer to gauge strength.
Time frame: Up to postoperative day 2
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Study Technique: Saphenous Nerve Block | Preoperative and Postoperative Thigh Muscle Strength in Both Legs | Baseline | 17.06 kilogram-force unit | Standard Deviation 10.65 |
| Study Technique: Saphenous Nerve Block | Preoperative and Postoperative Thigh Muscle Strength in Both Legs | 6-8 h postoperative | 2.86 kilogram-force unit | Standard Deviation 3.55 |
| Study Technique: Saphenous Nerve Block | Preoperative and Postoperative Thigh Muscle Strength in Both Legs | 24 h postoperative | 5.00 kilogram-force unit | Standard Deviation 3.68 |
| Study Technique: Saphenous Nerve Block | Preoperative and Postoperative Thigh Muscle Strength in Both Legs | 48 postoperative | 3.35 kilogram-force unit | Standard Deviation 2.62 |
| Control Technique: Femoral Nerve Block | Preoperative and Postoperative Thigh Muscle Strength in Both Legs | 48 postoperative | 3.76 kilogram-force unit | Standard Deviation 3.35 |
| Control Technique: Femoral Nerve Block | Preoperative and Postoperative Thigh Muscle Strength in Both Legs | Baseline | 17.24 kilogram-force unit | Standard Deviation 14.37 |
| Control Technique: Femoral Nerve Block | Preoperative and Postoperative Thigh Muscle Strength in Both Legs | 24 h postoperative | 5.08 kilogram-force unit | Standard Deviation 4.06 |
| Control Technique: Femoral Nerve Block | Preoperative and Postoperative Thigh Muscle Strength in Both Legs | 6-8 h postoperative | 2.45 kilogram-force unit | Standard Deviation 3.31 |
Secondary
Rating the Success of the Nerve Blocks
Time frame: Up to postoperative day 2
Population: The success of nerve blocks was not collected or analyzed. Instead, muscle strength was collected (data are presented in another table).
Secondary
Tracking Total Opioid Usage
Time frame: Up to postoperative day 2
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Study Technique: Saphenous Nerve Block | Tracking Total Opioid Usage | 133.11 milligrams | Standard Deviation 114.53 |