The era of minimally-disruptive spine surgery. Part 1: Failed Back Surgery Syndrome
When I first started my neurosurgery practice roughly a decade ago, many of my first patients were those who had essentially been discarded by other surgeons in the area. Most of those patients were told “there was nothing more that could be done” for them. The typical story was that a patient had gone in with a complaint of back pain and maybe some sciatica, and 3 or 4 invasive fusion surgeries later, had ended up worse off than they started. Often times, these patients would have intractable back pain, leg pain, or worse yet, neurological deficits such as foot drop, weakness, or numbness in their legs, inability to walk, or urinary, bowel, or bladder dysfunction. Many times these patients were also told that their imaging studies such as X-rays or MRIs “looked fine.”
This gave rise to the term “failed back surgery syndrome, or FBSS,” which is a Medicare-recognized diagnosis. It gave spine surgery in general a bad name, but also opened the door to innovative therapies and new approaches to spine surgery. This innovation forked in two directions, neuromodulation and complex spine surgery.
Neuromodulation in the setting of failed back surgery syndrome (also called failed laminectomy syndrome) most commonly refers to spinal cord stimulation (SCS). In spinal cord stimulation, electrical signals are delivered in the epidural space to modulate pain signals traveling through the spinal cord before they reach the brain and are experienced by a patient. For patients with low back and leg pain, these devices are placed in the thoracic spine. There is a trial, or test drive, with a temporary device before a permanent implant. These surgeries are performed on an outpatient basis and are covered by most insurances and Medicare. Originally, the devices were indicated for the treatment of leg pain associated with FBSS, but new data suggests these can also be effective for back pain as well (see the Nevro HF10 Senza trial). Roughly 70–80 percent of patients acheive at least 50 percent pain relief with this intervention.
While SCS is a great therapy for many patients, it is often not effective in patients with mechanical back pain (such as arthritis, instability, or “flat back syndrome) and tends to be more effective for patients with “neuropathic” or nerve related pain. But in short, the limitation of spinal cord stimulation is that the therapy is maturing independently of understanding why patients are failing back surgery in the first place. Was it a nerve injury during previous surgery? Is there a sagittal balance problem? Is there an adjacent segment problem? These are questions the waste basket term of “failed back surgery syndrome” does not have the granularity to handle.
Complex spine surgery is the second fork in the road, and much of this is concerned with dissecting out why certain patients fail back surgery. The concept that has gained the most traction is the idea of “sagittal balance.” Essentially, this means that the ideal biomechanics of the spine are such that the head remains centered over the pelvis. This is accomplished by a series of complementary curves in the spine. In the native spine, a backwards curve, or lordosis, is present in the cervical (neck) and lumbar (low back) spine, and an opposite kyphotic curve is present in the thoracic spine.
In many of the “old school” lumbar (and to some extent, cervical) fusions, the natural lordotic curve was reduced, leading to “flat back syndrome.” This caused increased pain and workload on the rest of the spine because non-fused segments needed to accommodate the curvature lost by surgery. This leads to adjacent spinal segments failing over time, and a “domino effect” leading to more surgeries. This is called adjacent segment disease. To make matters worse, over two-thirds of the lordosis in the lumbar spine is present from L4-S1 which are the most commonly operated levels.
Corrective surgeries for flat-back syndrome have historically been large, morbid surgeries, called deformity corrections, that ultimately lead to improved outcomes if a patient could tolerate the surgery magnitude. Nowadays, innovations in this space such as hyperlordotic implants and lateral access surgery, have made these surgeries more palatable. However, many “old school” spine surgeons brush off sagittal balance, most likely because the topic seems daunting.
With that in mind, it is always easier to prevent problems in the first place rather than fix them after the fact. I heard once from another spine surgeon that we all are deformity surgeons, some of us are in the business of fixing and others are in the business of creating. In order to avoid flat back syndrome, we measure the relationship between the lumbar spine and the pelvis (lumbopelvic parameters). This is done to ensure that if we must fuse a patient, we do so in a way where the lumbar lordosis matches the forward tilt of the pelvis, thus keeping the spine aligned. I also apply these principles to the cervical spine, and I am a proponent of total disc replacement surgery (cervical arthroplasty, Mobi-C) in the neck to maintain motion in deteriorated segments of the cervical spine.
That being said, I am most excited about the technologies that allow us to treat patients without altering the biomechanics of the spine. These include early use of spinal cord stimulation (before fusion surgeries), minimally invasive laminotomies, microdiscectomies and other ways to take pressure off nerves, endoscopic spine surgery, and minimally-disruptive treatment of spinal stenosis such as the Superion device (Vertiflex). Some initial data is promising for regenerative therapies such as the injection of Platelet-Rich Plasma (PRP) into discs of the lumbar spine. These are all therapies I use in my practice.
Part 2 of this series regarding “minimally-disruptive spine surgery” can be read here. Part 3 of this series will discuss advancements in neuromodulation for spine-related pain. Part 4 will discuss regenerative therapies.