A study presented at the American Orthopaedic Foot & Ankle Society Specialty Day during the AAOS 2019 Annual Meeting found that in patients who had foot and ankle surgery, acute postoperative pain was significantly better among those receiving gabapentin compared to those who were not. By two weeks post-surgery, those taking gabapentin required less opioids for postoperative pain than those who did not receive gabapentin.

The study, presented by Jamal Ahmad, MD, of NorthShore Orthopaedic Institute and the University of Illinois at Chicago, was conducted prospectively over four months within the primary author’s surgical patient population. Inclusion criteria were adult patients who underwent orthopaedic foot and/or ankle surgery and used neither opioids nor gabapentinoids (i.e., gabapentin, pregabalin [Lyrica]) chronically before surgery. Patients taking opioids and/or gabapentinoids chronically before surgery were excluded, as were any patients who received nonsurgical treatment for their orthopaedic conditions.

Of the 150 patients included in the study, 75 received 45 pills of oxycodone/acetaminophen 10/325 mg every eight hours as needed without gabapentin for post-surgical pain in the first two weeks after surgery between May 2017 and January 2018. There were 32 men and 43 women in that group, with a mean age of 48 years (range, 18–81 years). The right and left lower extremities were involved in 44 and 31 patients, respectively. Sites of surgery were leg (n = 3), ankle (n = 31), hindfoot (n = 8), midfoot (n = 9), and forefoot (n = 24).

From February 2018 through August 2018, 75 patients received 45 pills of oxycodone/acetaminophen 10/325 mg every eight hours as needed with 30 pills of gabapentin 300 mg every 12 hours regularly for post-surgical pain. There were 35 men and 40 women in that group, with a mean age of 47 years (range, 18–87 years). The right and left lower extremities were involved in 41 and 34 patients, respectively. Sites of surgery were leg (n = 5), ankle (n = 39), hindfoot (n = 6), midfoot (n = 6), and forefoot (n = 19).

The study recorded postoperative pain at two days, two weeks, and three months in both study groups. A validated 10-point visual analog scale (VAS) pain score assessed pre- and post-surgical pain. At two weeks after surgery, patients in both study groups also were assessed for any number of unused opiates and the need for continued opioids to manage post-surgical pain.

For the 75 patients without gabapentin, the mean VAS pain score decreased from 8.0 to 6.4 to 1.9 at two days, two weeks, and three months, respectively (Table 1). Eighteen patients (24 percent) without gabapentin had unused opiates at two weeks after surgery. Twelve patients (16 percent) without gabapentin required additional opiates for pain two weeks after surgery. Twenty, 23, 22, and 10 patients rated their satisfaction with postoperative pain relief at two weeks after surgery as excellent, good, fair, and poor, respectively.

For the 75 patients with gabapentin, the mean VAS pain score decreased from 6.7 to 3.8 to 1.7 at two days, two weeks, and three months, respectively (Table 1). The mean pain scores at two weeks were significantly lower than those among patients without gabapentin (P = 0.03). Forty-two patients (56 percent) with gabapentin had unused opiates at two weeks after surgery, which was significantly higher than the percentage among those not taking gabapentin (P = 0.02). Five patients (6.7 percent) with gabapentin required additional opiates for pain two weeks after surgery, which was significantly lower than the percentage among those not taking gabapentin (P = 0.03). Satisfaction with post-surgical pain relief two weeks after surgery was significantly higher (P = 0.03) among those taking gabapentin, with 33, 25, 13, and four of those patients rating their satisfaction as excellent, good, fair, and poor, respectively. None of the study patients who received gabapentin after surgery developed adverse events (AEs) that prevented them from completing a two-week course of the medicine twice daily.

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Gabapentin is an analog of the neurotransmitter gamma-aminobutyric acid and interacts with certain voltage dependent calcium channels at synapses within the central and peripheral nervous system. This cellular mechanism of action translates into anticonvulsant and analgesic properties, and the medication is traditionally used to treat conditions such as convulsions, seizures, neuropathic pain, and diabetic neuropathy.

Dr. Ahmad noted that little research has been conducted on the use of gabapentin for managing postoperative pain after orthopaedic foot and ankle surgery. A 2007 prospective, comparative, placebo-controlled, double-blinded study by Montazeri et al., measured pain relief and morphine consumption in 70 patients who did and did not receive a single dose of gabapentin immediately before foot and/or ankle surgery. The investigators found that patients who received gabapentin had significantly less pain and morphine consumption than those who did not receive gabapentin. However, pain scores and amounts of morphine consumed were not measured beyond 24 hours after surgery. In addition, patients received only one dose of gabapentin preoperatively rather than a regular dosage in the acute post-surgical period. To date, Dr. Ahmad said, no investigations have included patients who were prescribed gabapentin after foot and ankle surgery and assessed pain values beyond 24 hours after surgery.

Dr. Ahmad noted the limitations of his study. “As patients were not blinded for their disuse and use of gabapentin after surgery,” he wrote, “they may have had preconceived notions regarding differences between opioids and opioids with adjuvant gabapentin for managing postoperative pain. If this was the case, this may have an effect on patient-reported outcomes between the study groups.”

Another shortcoming of the study involved its enrollment and duration. “We acknowledge that the study populations that did not receive and received gabapentin were limited in size,” Dr. Ahmad wrote. “A larger number of patients for both study groups are needed to confirm or refute our results. In addition, it can be argued that both patient populations require longer follow-up than three months after surgery to fully assess their final pain scores. In time, more patients may develop different levels of pain. Ultimately, longer follow-up for both patient populations without and with adjuvant gabapentin may be required to support or deny our results.”

Dr. Ahmad commented: “I conducted this study because of the need to decrease opioid abuse and misuse among postoperative patients. Before this study, I prescribed gabapentin as needed when patients would complain of postoperative neuropathic pain. It had good results, so I considered using it regularly for adjuvant postoperative pain management.”

He said he was “pleasantly surprised” that no patients on gabapentin developed AEs that warranted stopping the medicine. Since conducting the study, he has added a five-day course of ketorolac for adjuvant pain relief. “I don’t know yet if that makes a significant difference compared to gabapentin alone,” he said. “I would infer that adding a nonsteroidal anti-inflammatory drug for two weeks may augment the pain relief provided by gabapentin.”

Terry Stanton is the senior science writer for AAOS Now. He can be reached at tstanton@aaos.org.

References:

1. Saini S, McDonald EL, Shakked R, et al: Prospective evaluation of utilization patterns and prescribing guidelines of opioid consumption following orthopedic foot and ankle surgery. Foot Ankle Int 2018;39:1257-65.
2. Gupta A, Kumar K, Roberts MM, et al: Pain management after outpatient foot and ankle surgery. Foot Ankle Int 2018;39:149-54.