Having a raised Body Mass Index (BMI) is known to lead to poorer patient outcomes in surgery for lower back problems. However, what impact does a raised BMI have on patients who undergo surgery on their neck for Degenerative Cervical Myelopathy (DCM)? A team of researches in Canada decided to investigate
What did they do?
The team looked at data collected from patients operated on for DCM in 26 centres located in America and Canada. 757 patients were included in the study and were split into groups based on their BMI: underweight, normal weight, overweight, and obese. The researchers then looked at how well the groups of patients faired after surgery on their neck for DCM.
Patient outcomes were assessed by looking at three outcome domains: function (using a scale called the mJOA), symptoms (using a scale called the NDI or neck disability index), and quality of life (using a scale called the SF-36).
They went on to control their results for many other factors such as the patient’s age, level and severity of DCM, surgical technique, which are known to affect how patients respond to surgery By doing this, any differences between the groups of patients post-surgery could be attributed solely to differences in their BMI (and not bias by other factors).
So what did they find?
The researchers found that the greater a patient’s BMI, the higher their Neck Disability Index i.e. symptoms would be after surgery. NDI is a measure of difficulties patients have in day-to-day life such as with personal care and reading that are caused by pain in their neck. The team also found strong trends but no significant relationship between patients’ BMI and their quality of life after surgery (MCS/PCS).
So, what does this all mean? Well, the researchers suggest that although patients with a raised BMI have good functional outcomes from surgery, this appear to be less likely to translate into practical improvements in their day to day activities.
However, the trouble with examining NDI in this setting is that it relates to disability caused by neck pain, a feature which DCM surgery does not specifically aim to improve. By the functional measures that surgery aims to improve or at least stabilise (mJOA), patients with BMI were no worse off post-op than those with normal weight.
What can we conclude?
We have recently described a study showing fat infiltration in neck muscles is associated with greater neck pain in myelopathy. Is this more evidence that obesity can worsen symptoms of DCM?
What remains to be seen, is whether efforts to counter obesity can help improve symptoms in DCM. However there is clearly a growing number of studies pointing towards a relationship and that requires further investigation.
Of course, weight loss in DCM will be easier said then done, given the functional impairments, but if it can make a positive impact, surely it is worth pursuing?
1.Jefferson et al. Impact of Elevated Body Mass Index and Obesity on Long-term Surgical Outcomes for Patients With Degenerative Cervical Myelopathy: Analysis of a Combined Prospective Dataset Feb 2017 Spine
By J Tempest Mitchell
When considering whether to undergo surgery for treatment of CSM, one of the biggest questions that people want answered is what the risks are, and how likely they are to occur. Well, they’re in luck- a team from China have just completed a large-scale study, looking at previous research on the topic, to try and find out exactly that (1)!
Overall, the researchers looked at over 100 previous studies, and more than 8500 patients who underwent surgery to treat CSM, and found that just over 20% experienced some degree of complications from the surgery: in other words, twenty out of every hundred patients had some form of issues afterwards. Whilst this percentage may initially seem quite high, it is important to remember that CSM surgery can be life-changing, and that many of these side effects may be only temporary or minor compared to the damage that the disease itself can cause.
So what sort of complications did patients experience?
The most common of the complications examined in the study was difficulty or pain on swallowing, which nearly 17% of the patients studied reported on the first day after surgery (although the data doesn’t tell us how long this effect lasted beyond that first day). The next most common complication was axial (neck) pain, which was reported by 15.6% of patients.
Other problems seen after surgery were:
· Damage to the nerve C5, which supplies part of the upper arm (5.3%)
· Hoarseness (4.0%)
· Graft subsidence, an issue where the graft sinks into the bones of the spine, causing distortion (3.7%)
· Dislodgement of the graft (3.4%)
· Infection (2.8%)
· Failure of the bones in the spine to fuse (2.6%).
Two rarer, but potentially more serious complications seen were infection of the CSF (the fluid surrounding the spinal cord) in 1.9% of patients and epidural haematoma (bleeding between the outer lining of the spinal cord and brain, and the skull) in 1.1%.
These complication rates varied slightly, depending on the subtype of myelopathy from which patients were suffering, and also the exact operation type. In particular, patients with myelopathy caused by OPLL (a condition in where a flexible structure known as the posterior longitudinal ligament thickens and become less elastic) had a higher risk of damage to the C5 nerve and CSF infection after surgery.
This information is useful to allow patients to make an informed decision. It should be remembered that despite these possible problems, overall surgery for CSM has been shown effective to stop disease progression.
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