Functional Outcome and Analgesia in TKA: Radiofrequency vs Continuous Adductor Canal Block

The aim of this study is to compare the efficacy of two analgesia techniques in patients undergoing Total Knee Arthroplasty (TKA) on the functional recovery and pain control: Pulsed and Continuous Radiofrequency (PRF and TRF) applied respectively to the saphenous nerve and to the genicular nerves of the knee (femoral and sciatic branches) compared with Continuous adductor canal block with local anesthetics (CACB).

The Null Hypothesis is that no difference exists in the functional recovery, in pain medication consumption and in postoperative exercise and physical performance between two groups of patients submitted to TKA with the two different modalities of analgesia.

To test the null hypothesis we hypothesize as clinically relevant:

• a reduction of 30% in the time needed to perform the Timed Up and Go test at 2 days after surgery
• a reduction of 30% in pain medication consumption in the first 24 ore after surgery.

To test the null Hypothesis, 40 patients are needed (20 for each group).

The primary outcome measures will be:

• the time required in the two groups (CACB-group and RF-group) to perform the Timed-Up and Go (TUG) test on the second postoperative day (POD2). TUG measures the time that a person takes to rise from a chair, walk three meters, turn around, walk back to the chair, and sit down. During the test, the person is expected to use any mobility aids that they would normally require.
• the total morphine consumption by means of the patient-controlled analgesia pump over the first 24-h after surgery, which can be measured precisely through the record of the dose delivered by the PCA pump. With an alpha error of 0.05, a power of 80% and a standard deviation of 7 mg of morphine consumption per 24 h, 20 patients (10 in each group) will be required for the study to detect a mean difference of 10 mg of morphine between the two groups

Secondary outcome measures include: Pain evaluation with the use of VAS at rest, VAS on walking and on knee flexion; functional outcome evaluation with the 6 min walk tests, degree of knee flexion, Scores obtained in self-assessment questionaire (WOMAC-Western Ontario and McMaster University questionaire for knee osteoarthritis and CHAMPS-Community Healthy Activities Model Program for Seniors). These values will be compared with baseline values recorded before surgery.

It is hypothesized that PRF and TRF of the saphenous nerve and genicular nerves to the knee joint can improve the early and late functional recovery and the pain control after TKA when compared with the CACB

Inclusion criteria

• Diagnosis of knee Osteoarthritis requiring Total Knee Arthroplasty (TKA)

Exclusion criteria

• Previous TKA (revision surgery)
• ASA (American Society of Anesthesiology) Classification > 3
• Known Rheumatologic disease
• Morbid Obesity (BMI > 45)
• Inability to perform simple physical tasks (6 minutes walk test, Timed-Up and Go test)
• Organ transplant, Allergy to opioids, to local anesthetics or other medications used in the study,
• Chronic use of opioids or sedatives, Contraindication to receive regional anesthesia (e.g. coagulation defect), contraindication to Patient Controlled Analgesia pump (PCA) or inability to use PCA or to comprehend pain scales