Obesity and Its Implications for Cervical Spine Surgery

SUMMARY:The unique requirements created by cervical spine surgery on the obese patient are discussed in this article. For successful outcomes, obese patients need to be optimized medically during the pre-operative period, especially with regard to diabetes, hypertension, cardiac issues, and pulmonary concerns. Postoperatively, the risks of wound infection and blood clots (deep venous thromboses) are preventable complications, among others, that are correlated with obesity. As the US population trends toward progressive obesity, it becomes increasingly important to maximize care for this challenging group of patients.

Over time, the incidence of obesity (defined as a body mass index > 30) has become a national and a global concern that impacts all surgical specialties, including those performing cervical spine surgery. The incidence of obesity in the US has risen to well over 40% and is associated with a whole host of numerous chronic conditions, including diabetes, cardiovascular disease, pulmonary disorders, and hypertension. Included in this list is a dramatically elevated incidence of osteoarthritis in the spine. This is thought to be the result of two mechanisms: the mechanical destruction of cartilage between the spinal segments as well as systemic inflammation due to various agents produced by the adipose tissue itself. These processes lead to degeneration of the cervical discs and ligaments, promoting bone spur formation that eventually compress the spinal cord and nerve roots. When severe, the ultimate effect is cervical radiculopathy and cervical myelopathy.

When conservative measures failure, surgery on the obese patient is an option, although with increased risk (see below). Studies have shown obese patients still experience significant symptomatic benefit from operative intervention although with increased risk.

Bariatric surgery and the use of GLP-1 medications show promising benefits, but they do not entirely mitigate the higher risks of cervical spine surgery in the obese individual. Recent studies indicate lowered rates of spinal disorders, including cervical disc herniations, as well as a lowered risk of medical complications after spinal spinal surgery in patients who have undergone successful bariatric surgery.

A BMI > 40 has been shown by numerous studies to be an independent predictor of early complications after spine surgery, including cardiac and pulmonary issues, deep venous thrombosis, pulmonary embolism, kidney dysfunction, wound infection, and sepsis. Most surgeons regard the patient with a BMI > 40 as presenting a risk that is “”too high” for semi-elective spine surgery, especially if it involves a fusion and instrumentation. It is therefore essential that special considerations be taken into account (pre-, intra-, and post-operatively) to provide an optimal outcome for the obese patient.

1. As discs degenerate and the covering of the disc tears (“annular tears”), release of chemical agents can cause inflammation and irritation of adjacent pain-sensitive structures (“discogenic pain”). Disc collapse can lead to hypermobility and mechanical pain.
2. Abnormal motion due to degeneration of the facet joints can also lead to hypermobility of the joints, irritate the facet nerves, and cause additional local pain that remains midline (“facet-mediated pain”).
3. Muscle spasm and fatigue resulting from attempts to combat the hypermobility and the effects of gravity can add to the resultant chronic pain syndrome or, over time, result in chronic postural abnormalities like kyphosis (“myofascial pain”).Additionally, in the face of multiple disc herniations with multiple levels of degeneration, pain may stem from a combination of processes at multiple levels involving multiple pain generators, making diagnosis and treatment even more complex.

Clinical evaluation of axial neck pain includes:

1. A careful history and physical exam focusing on the location, severity, duration, character, radicular nature (if any) and precipitating factors, including aggrevating and alleviating factors. The physical exam is focused on determining unrecognized weakness and
   sensory abnormalities, focal tenderness, and provocative testing in attempt to identify a particular level or levels responsible for generating the pain syndrome.
2. Imaging Studies:
   • A)MRI Remains the gold standard to determine the number, extent, and severity of the levels of degeneration and to evaluate for cord compression.
   • B). Dynamic (flexion-extension) x-ray films are critical to rule out instability (to much or “sloppy” movement).
   • C). CT scanning is used to evaluate facet joint pathology and to examine bone details; this is useful to rule out fractures that may not be apparent on plain x-rays.
   • D). Bone Scan. The authors have found bone scanning with SPECT imaging to be especially useful in patients with axial neck pain of undetermined etiology. A bone scan will light up as an area of abnormal uptake of the radiotracer where bone is being metabolized (i.e., active arthritis). The scan will also be abnormal in the region of a small fracture that would be difficult to visualize by other methods.
   • E). Diagnostic Blocks. Selective injections into a particular facet joint or selective nerve root blocks associated with pain diaries are often very useful as both therapeutic and diagnostic measures to localize a particular pain generator. Note that injection of multiple levels simultaneously is of questionable value as it does not pinpoint the source of the pain. Discograms (injection of dye into a cervical disc space in attempt to recreate the patient’s pain syndrome) are mentioned only to be discouraged; studies have shown them to be nonspecific with high false positive findings and subject to significantly inconsistent interpretation.

1. Physical therapy focused on neck stabilization exercise, postural training, and range of motion. High acceleration-deceleration chiropractic manipulation is, in general,contraindicated.
2. Facet injections, trigger point injections, selective nerve root blocks, and epidural steroid injections
3. Medications like non-steroidal anti-inflammatory agents, muscle relaxants, neuromodulators like pregabalin and gabapentin, antidepressants like amitriptiyine, etc.
4. Injection of neuro biologics like platelet-rich plasma.
5. Use of a transcutaneous nerve stimulator (TENS unit).
6. If pain can be localized to a particular facet joint, a percutaneous radiofrequency facet rhizotomy may be indicated. This procedure involves placing a special needle into the facet joint and destroying just the nerve fibers mediating pain supply to that facet joint with an electrical current without damaging the spinal nerves. Unfortunately, the procedure may not produce permanent results.
7. Lifestyle modifications, including weight loss, exercise, ergonomic adjustments, smoking cessation, etc

At least 6 weeks of intense conservative measures are warranted before considering
surgery.

Surgery is a reasonable option when:

1. Persistent disabling neck pain exists despite exhausting conservative measures.
2. Development of progressive neurologic deficits.
3. Significant structural pathology is evident (such as a massive disc herniation with cord deformation).
4. Progressive spinal deformity occurs over time.
5. A definitive pain generator (e.g., a degenerated facet joint) can be identified that does not respond to appropriate conservative treatment.
6. Overt spinal instability is present.

1. Anterior cervical discectomy with instrumentation and fusion (ACDIF). The benefits include decompression of neural elements, recreation of cervical alignment and stabilization of the diseased segments at the expense of loss of normal mobility at the fused levels. Careful selection of the levels to be fused is necessary to avoid limitation of motion and avoid development of degeneration at the levels above and below the fused segments (“adjacent segment disease”). See the multiple articles on this website regarding the risks and benefits of ACDIF.
2. Cervical disk arthroplasty (“artificial” cervical disc replacement) (CDA). This procedure seems to be most appropriate for the younger patient with advanced degeneration or instability. It theoretically preserves motion, potentially reducing the risk of adjacent segment disease. However, due to structural constraints, it is not ideal to provide for distraction or recreate cervical lordosis in the face of existing kyphosis. In addition, many CDA’s end up fusing, with the end result being an overall worse outcome after 10 years compared to an ACDIF. See the multiple articles on this website regarding CDA’s for additional information.
3. Hybrid approaches. This construct combines ACDIF at markedly degenerated levels with CDA at healthier levels to optimize the balance between stability and motion preservation in selected patients with a spectrum of pathologies.
4. Posterior cervical decompression with instrumentation and fusion (PCDIF). This procedure is especially useful if a particular facet joint is identified as the pain generator. However, it is generally contraindicated in the face of significant cervical kyphosis. See additional articles on this website regarding PCDIF for more information.

Surgical outcomes for treatment of axial neck pain in the absence of spinal cord or nerve root symptoms are less predictable than those for radiculopathy or myelopathy and remain with success rates (good or excellent outcomes) of 60-82%. Careful patient selection with demonstration of a definitive pain generator is critical to maximizing the chance of success. Care should be taken to avoid fusing more levels than necessary to minimize the changes associated with altering the sagittal balance of the spine and increasing the risks associated with adjacent segment disease. Challenges associated with surgical treatment include the difficulty in many cases of identifying the true pain generator among multiple affected segments and the risks associated with accelerating adjacent segment disease. As a result, recurrent or residual pain is more common after cervical fusion surgery for axial neck pain than with operations directed for cervical myeloradiculopathy.

Management of multiple cervical disc herniations presenting primarily with axial neck pain requires a conservative approach initially and a careful, thoughtful analysis before surgery is recommended. When indicated, surgery should be designed to treated the pain generator, preserve motion, and minimize development of adjacent segment disease to improve long-term outcomes. Careful patient selection, targeted treatment, and realistic counseling are the pertinent aspects to optimizing results. Remember — the surgery needs to be worth the risks; and “we can always operate— we can never unoperate!”

If you or a loved one is suffering from chronic neck pain and cervical spine surgery has been recommended, a second opinion is always a good idea. Call us today if we can be of assistance at 1-855-854-7274 — ask about our free MRI review!