SLR - September 2018 - T. Craig Wirt

The Importance of the Saphenous Nerve Block for Analgesia Following Major Ankle Surgery: A Randomized, Controlled, Double-Blind Study

Reference: Bjørn S, Wong WY, Baas J, Nielsen KK, Børglum J, Hauritz RW, Bendtsen TF. The Importance of the Saphenous Nerve Block for Analgesia Following Major Ankle Surgery: A Randomized, Controlled, Double-Blind Study. Reg Anesth Pain Med. 2018 Jul;43(5):474–479.

Scientific Literature Review

Reviewed By: T. Craig Wirt, DPM
Residency Program: Mercy Hospital and Medical Center, Chicago, Illinois

Podiatric Relevance: With the increasing prevalence of surgical success being measured by patient-reported outcomes, the amount of pain experienced by the patient in the immediate postoperative period would seem to play an important role in how patients view their surgery. Along with modalities, such as oral analgesics, many foot and ankle surgeons utilize perioperative regional blocks, often popliteal, to decrease postoperative pain. The positive impact of popliteal blocks on decreasing postoperative pain is well documented in literature; however, the effect of an adjuvant saphenous block on patient-experienced levels of pain is less known. This study examined the effect of a saphenous nerve block on postoperative pain in patients who underwent major ankle surgery.

Methods: Eighteen patients were enrolled in this prospective, controlled, double-blind study, and all received a preoperative popliteal block prior to a total ankle arthroplasty, ankle arthrodesis, subtalar arthrodesis or triple arthrodesis. Patients were randomized into two groups—those who received a placebo saline injection and those who received a saphenous nerve block with bupivacaine. Postoperatively, patients were asked to score their pain on a numerical rating scale (NRS) from 0 to 10. The effect of the sciatic nerve block was evaluated with a sensory test to rule out any confounding effect of an incomplete sciatic block. Pain scores were evaluated at 30, 45, 60, 75, 90, 105 and 120 minutes from the conclusion of surgery. The primary outcome of this study was the frequency of patients experiencing significant clinical pain at rest (NRS>3) at any time during observation.

Results: All 18 patients achieved successful popliteal blocks, defined as cessation of sensation in the distal sciatic nerve territory. The number of patients experiencing significant clinical pain was eight of nine in the placebo group versus one of nine in the bupivacaine group (P=0.003). All of the patients who reported pain localized it to the medial and/or anterior side of the ankle joint. The maximal reported pain score during the observation period was lower in the bupivacaine group compared to the placebo group (median 0 vs 5, P=0.001). Six of the eight patients in the placebo group experienced NRS greater than three on arrival to the PACU.

Conclusions: The authors suggest that a saphenous nerve block, as a supplement to a popliteal sciatic nerve block, can markedly reduce the amount of pain a patient experiences after major ankle surgery and should be routinely used. The randomized, controlled, double-blind study design is a major strength of this research and lends weight to the results. One potential shortcoming is the limited amount of time clinical pain levels were documented. A window of 24 to 48 hours after surgery would provide greater insight into the wider effects of the additional saphenous nerve block. A second area that could be expanded upon is the influence that decreased levels of pain have on important factors, such as opioid usage postoperatively as well as the level of patient satisfaction as it relates to postoperative pain.

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