Use of a curved needle to facilitate four-in-one nerve block performance after total knee arthroplasty in elderly patients: a randomized clinical trial.

Background: Peripheral nerve block is the main analgesic technique for total knee arthroplasty (TKA) in elderly patients. Accurate delivery of the needle tip to the target nerve under ultrasound-guided is a prerequisite for successful nerve block. Failed needle-tip positioning in sciatic nerve (SN) or medial femoral cutaneous nerve (MFCN) block can be due to anatomical structure shadow. The aim of the study was to compare curved and straight needles in regard to the time needed to perform the nerve block for TKA in elderly patients.

Methods: One hundred patients aged 65 to 80 years and ASA II-III, BMI 18-30 kg/m, who underwent general anesthesia for unilateral TKA received the nerve block under ultrasound guidance after surgery, were included in this study. All patients were randomly divided into two groups (N.=50): straight needle group (Group S) and curved needle group (Group C). The primary outcome measure was the time needed to successfully perform the nerve block. Secondary outcomes included the number of attempts and needle redirections to achieve nerve blockade, as well as the satisfaction of patients and anesthesiologists.

Results: Compared with group S, the performance time was shorter in group C (488.0±44.9 vs. 517.8±42.1 P=0.001). The procedural pain score was less in group C (1.8±0.4 vs. 2.4±0.6, P=0.000). The satisfaction score of the anesthesiologist (3.4±0.8 vs. 2.4±0.6, P=0.000) and patients (3.4±0.7 vs. 1.9±0.6, P=0.000) were higher in the curved needle group compared with the straight needle group.

Conclusions: The use of a curved needle can reduce the time required to perform the nerve block, with reduction in the number of attempts and needle redirections. Curved needle also resulted in lesser procedural pain and higher satisfaction compared with the straight needle.