1. List concerns with neuraxial anesthesia and analgesia in patients with prior back surgery

Elective total knee arthroplasty (TKA) is a safe, common, and rapidly growing orthopedic procedure, performed more than 600,000 times per year in the United States [1]. In the coming decades, further exponential growth is expected, with estimations of well over 6 million procedures to be performed annually by 2030 [2]. While multiple anesthetic options are available to this population, peripheral nerve and neuraxial blocks are often offered. A shift from epidural toward peripheral nerve blocks for postoperative analgesia has occurred and peripheral nerve blocks are often complemented intraoperatively with general or spinal anesthesia [3–4].

Long considered a contraindication to neuraxial anesthesia, a history of prior spine surgery does not necessarily preclude safe and effective use of spinal or epidural techniques. Many patients live with persistent pain after spine surgery. Understandably, they fear the introduction of medications or needles to this area, potentially worsening symptoms or introducing infection. All concerns must be addressed prior to initiation of any neuraxial anesthetic in these individuals.

Following posterior spine surgery, patients may have a number of postoperative anatomic changes. These include damage to the ligamentum flavum, obliteration or scarring of the epidural space, or the addition of hardware or bone-graft material. These factors may increase the risk for inadvertent dural puncture, false loss of resistance, or the inability to pass small-gauge spinal needles. Further, scarring of the epidural space may lead to “patchy” epidural blockade and this can occur with prior intervertebral disc rupture, even in the absence of surgical repair [5–7]. Patients with a history of spinal surgery from an anterior approach, with no manipulation of the epidural space, would seemingly be at decreased risk for these complications. Whenever possible, an accurate surgical history, including operative report, and post-procedure imaging, should be obtained. Understanding the extent and location of the prior surgical intervention can guide the anesthesiologist in avoiding undue complications during placement of neuraxial anesthesia.

2. Evaluate if epidural or spinal anesthesia has a higher incidence of complications following spine surgery

Many studies of epidural placement in patients with a history of prior spine surgery come from the obstetric anesthesia literature. Feldstein et al. reported on three cases of labor epidural anesthesia placed in patients with a history of posterior lumbar fusion to treat kyphoscoliosis [8]. The authors noted no difficulty in locating the epidural space or threading the epidural catheter; notably, in all cases, the anesthesiologist’s needle approach was from below the lowest fused spinal segment. They found no differences between effectiveness and dose requirements of the lumbar fusion patients when compared to patients without fusion; although no statistical analysis was performed. No post-procedure neurologic complications were noted.

Crosby and Halpern undertook a five-year retrospective study of nine patients, with a prior history of Harrington rod instrumentation for idiopathic scoliosis, undergoing labor epidural anesthesia. None of these patients had antepartum neurologic dysfunction [9]. In five of these patients, the experienced anesthesiologists were successful on their first attempt at placement of the epidural catheter. The other patients experienced complications such as multiple attempts prior to successful placement, blood encountered during placement, and inadvertent dural puncture. Of note, one of the patients with uncomplicated catheter placement had an unsatisfactory analgesic result. During replacement of the catheter, the dura was punctured and no further attempts were made.

Another review, of 52 patients, revealed successful placement of the epidural catheter on first attempt in only 47% of laboring patients with a history of Harrington rod instrumentation. Additionally, 55% of patients described their analgesia as satisfactory, and dural puncture and subdural catheter placement each occurred in 4% of patients. Notably, the rates of difficult placement and complications from epidural catheterization were noted to be higher when attempts were made to pass through surgically scarred levels. When passing caudal to the surgical incision, 59% of patients had successful first-attempt placement of the epidural catheter, but still only 56% of patients rated their labor analgesia as satisfactory. The rates of dural puncture when passing below the surgical scar were no different than when passing directly through the surgical incision [10].

Bauchat et al. reported on a prospective case-controlled observational study looking at hourly labor epidural bupivacaine consumption in 42 women with a history of prior discectomy surgery [11]. Most patients had undergone microdiscectomy (58%), whereas 21% had discectomy with or without laminectomy. No difference in time-to-placement of epidural catheter in study and control groups was found. Seventeen percent of prior discectomy patients had attempts made at greater than one interspace compared with 2% of controls. Hourly bupivacaine consumption was equivalent in both groups.

3. Discuss if these concerns change based on the extent of surgery (i.e., discectomy, laminectomy, fusion, instrumentation)

In 1980, Berkowitz and Gold performed 42 spinal anesthetics in 33 elderly patients with a history of lumbar laminectomy with and without spinal fusion undergoing urologic procedures [12]. The authors noted success in all but one intrathecal injection and concluded that these patients can safely receive spinal anesthesia. No long-term follow-up was performed. Similarly, in 2010, Hebl et al. performed a 15-year retrospective study that looked at 207 patients with a history of prior spine surgery undergoing spinal, epidural, continuous intrathecal catheter, or combined spinal–epidural anesthesia for a variety of indications [13]. There was no statistical difference in block efficacy or technical complications between those with and without a history of prior spinal surgery.

Although all neuraxial anesthetics have some associated risk, patients with pre-existing symptomatic spinal stenosis or lumbar disc disease, regardless of prior spine surgery, appear to be at greater risk for worsening of these symptoms or developing new symptoms postoperatively. In at least one study, patients with a history of spine surgery but without radicular features, peripheral neuropathy, or motor deficits had a similar risk of complications from neuraxial anesthesia as patients who had not undergone spine surgery [5, 13]. A full preoperative history and neurologic exam is prudent in any patient with prior spine surgery before deciding to proceed with neuraxial anesthesia.

In summary, the literature involving neuraxial techniques after spine surgery is contradictory, but some conclusions can be supported. Epidural anesthesia and analgesia appear to have a higher incidence of failure and complications if performed at the level of prior posterior fusion surgery; epidural techniques after simple discectomy may be less problematic. Spinal anesthesia is generally possible and effective. In the described patient, the authors would proceed with the same technique as in the general population, a preoperatively placed femoral or adductor canal nerve perineural catheter and a single-injection sciatic nerve block with a spinal for intraoperative anesthesia.