postoperative pain and analgesic consumption between the first and the second surgery would be compared in patients undergoing staged bilateral total knee arthroplasty (BTKA).

postoperative pain and analgesic consumption is compared between the first and second total knee arthroplasty (TKA) operation.

Inclusion Criteria:

• patients undergoing elective bilateral staged total knee arthroplasty at a 1-week interval under spinal anesthesia,
• age <=85
• American Society of Anesthesiologists physical status of I to II

Exclusion Criteria: any contraindication to spinal anesthesia or femoral nerve block such as coagulopathy; conversion to general anesthesia; preexisting pain syndrome; abnormal liver function or renal test results; severe heart, liver, or renal disease; history of stroke or neurologic deficits; psychiatric disorder; chronic opioid use; drug dependency; allergy to study medications; inflammatory joint disease; previous surgery on or trauma of the knee; difference in preoperative VAS score of ≥ 20 (at rest and at maximum knee flexion) between each side of the knee; body mass index of ≥ 40 kg/m2; and inability to comprehend the VAS or to use patient-controlled analgesia (PCA.

patients undergoing elective bilateral staged total knee arthroplasty