Bariatric Surgery Lowers Rates of Spinal Symptoms and Spinal Surgery in a Morbidly Obese Population : Clinical Spine Surgery

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Bariatric Surgery Lowers Rates of Spinal Symptoms and Spinal Surgery in a Morbidly Obese Population

Passias, Peter G. MD*; Fernandez, Laviel MD*; Horn, Samantha R. BA*; Ihejirika, Yael U. BA*; Wang, Erik BA*; Vasques-Montes, Dennis MS*; Shepard, Nicholas MD*; Segreto, Frank A. BS*; Bortz, Cole A. BA*; Brown, Avery E. BS*; Pierce, Katherine E. BS*; Alas, Haddy BS*; Lafage, Renaud MS; Neuman, Brian J. MD; Sciubba, Daniel M. MD; Afthinos, John MD§; Lafage, Virginie PhD; Schoenfeld, Andrew J. MD

Author Information
doi: 10.1097/BSD.0000000000001346

Abstract

Obesity is a growing public health concern with rapidly increasing prevalence in the United States, affecting an estimated one-third of the population.1 As the prevalence of obesity has increased, so has the number of overweight or obese patients undergoing spine surgery.2 While obesity has been associated with higher rates of low back pain and changes in spinopelvic alignment, the role of obesity in the development of spinal pathology remains controversial.3–6 Several studies have noted a significant association, though recent evidence suggests that fat rather than body mass index (BMI) may be of greater clinical significance.3,7

Bariatric surgery (BS) has now become an integral part in the treatment algorithm for morbid obesity. Various techniques for BS have been described and rates of surgery have increased in the past 2 decades.8 Surgery is typically indicated in patients with BMI >35 kg/m2 with obesity-related conditions or an isolated BMI >40 kg/m2.9,10 While BS has been found to improve weight loss outcomes and weight associated comorbidities, its role in spine surgery and effect on spine-related conditions remains largely unknown.

Therefore, the purpose of this study was to assess the impact of BS on reported spinal disorders. Using the large-scale, multi-institutional New York State Inpatient Database (NYSID), we compared reported rates for spinal conditions before and after BS. In addition, we sought to analyze the potential impact of BS on rates of surgical intervention for spine-related disorders.

MATERIALS AND METHODS

Data Source

The NYSID was developed by the Healthcare Cost and Utilization Project with support from the Agency for Healthcare Research and Quality. NYSID contains patient information from billing codes and captures patients who are covered under Medicare, Medicaid or private insurance. It includes over 100 clinical and nonclinical variables that are derived from a hospital discharge abstract, including primary and secondary diagnoses and procedures, admission and discharge status, demographics including age, sex, race, payment source, charges, and hospital length of stay. The database utilizes International Classification of Diseases Ninth Revision Clinical Modification codes (ICD-9-CM) to identify diagnoses and procedures. Unique patient linkage codes allow identification of multiple and return inpatient stays over time.

Patient Grouping

Patients over the age of 18 years old were included from NYSID years 2004–2013. Morbidly obese patients (ICD-9-CM code 278.01) who underwent BS were included (ICD-9-CM procedure codes 43.11, 43.19, 43.7, 43.82, 43.89, 44.31, 44.38, 44.39, 44.68, 44.69, 44.95, 45.51, 45.91, 44.5, 44.96, 44.97, 44.98, 44.99). Using the patient linkage codes supplied with NYSID, patients were tracked across the full 10-year period to assess any occurrence of spinal complaints (assessed by spine-related diagnoses) and/or spinal surgery (ICD-9-CM procedure codes 81.01, 81.02, 81.03, 81.31, 81.32, 81.33, 81.04, 81.05, 81.06, 81.07, 81.08, 81.34, 81.35, 81.36, 81.37, 81.38, 81.39). For the control group, morbidly obese patients without BS were isolated using ICD-9 code 278.01 (Appendix 2, Supplemental Digital Content 2, https://links.lww.com/CLINSPINE/A230).

Spinal disorders and surgeries were assessed for included individuals before and after the BS and rates were compared. Common comorbidities in a morbidly obese population were also surveyed including musculoskeletal conditions, rheumatoid arthritis, myocardial infarction, congestive heart failure, peripheral vascular disease, neurologic dysfunction, hypertension, asthma, mental health issues, high cholesterol, sleep apnea and diabetes (controlled or uncontrolled, with and without various complications including ketoacidosis, hyperosmolarity and renal manifestation).

Statistical Analyses

Preliminary analysis assessed spinal complaints, spine procedures, and comorbidity rates before and after BS using χ2 tests for categorical variables. Multivariable logistic regression analysis was used to compare rates in a BS population and morbidly obese non-BS control population. Logistic analysis controlled for common comorbidities, age and biological sex, as these rates were different across the 2 cohorts. SPSS version 23.0 was used for all analyses. Significance was set at P<0.05 with 95% confidence intervals (CI).

RESULTS

Patient Sample

A total of 73,046 BS patients were included (mean age 67.88±17.66 y, 56.1% female). The most common bariatric surgeries performed were gastrectomy (73.9%), laparoscopic sleeve gastrectomy (65.9%), and gastric band with gastric bypass (19.9%). For the multivariable logistic regression analysis, 299,504 nonbariatric, morbidly obese patients were included (mean age 53.45±16.52 y, 65.6% female).

Spinal Disorders Pre-BS and Post-BS

Overall, the rates of spinal disorders decreased following BS (7.40%–5.14%, P<0.001). 77.1% of patients with a spinal disorder before BS that became asymptomatic following BS had this complaint disappear between 2 months and 2 years after the BS. The rate of encounters for cervical spine disorders decreased from 3.28% to 2.99% (P<0.001), with the most marked reductions in cervical spontaneous compression fractures (1.14%–0.78%), cervical disc herniation (0.44%–0.30%), and cervical spondylosis with myelopathy (0.38%–0.21%, all P<0.001, Table 1). Likewise, thoracic diagnoses also decreased after BS from 2.91% to 2.57%, most commonly thoracic radicular pain (0.46%–0.27%), and spontaneous thoracic compression fracture (1.14%–0.78%, all P<0.001, Table 2). Encounters for lumbar disorders also decreased after BS (5.39%–3.92%), with substantial reductions in events associated with lumbar compression fractures (1.14%–0.68%), lumbar spinal stenosis (1.41%–0.68%) and lumbar spondylosis (0.87%–0.47%, all P<0.001, Table 3).

TABLE 1 - Cervical Spine Complaint Rates Prebariatric and Postbariatric Surgery
Cervical Spine Complaints Prebariatric (%) Postbariatric (%) P
Any cervical 3.28 2.99 <0.001*
Cervical neck pain 0.43 0.37 <0.001*
Cervical fracture 0.01 0.01 0.983
Cervical spontaneous compression fracture 1.14 0.78 <0.001*
Cervical fracture—paralysis to upper spine 0.02 0.01 <0.001*
Cervical fracture—paralysis to lower spine 0.01 0.00 0.991
Cervical disc degeneration 0.28 0.17 <0.001*
Cervical disc herniation 0.44 0.30 <0.001*
Cervical disc herniation with myelopathy 0.20 0.08 <0.001*
Cervical disc space infection 0.06 0.05 <0.001*
Cervical vertebra dislocation 0.00 0.00
Cervical instability 0.02 0.01 0.980
Cervical radiculitis 0.24 0.11 <0.001*
Cervical vertebra infection 0.42 1.12 <0.001*
Cervical postlaminectomy syndrome 0.01 0.01 0.983
Cervical spinal stenosis 0.00 0.00
Cervical spondylosis without myelopathy 0.00 0.00
Cervical spondylosis with myelopathy 0.38 0.21 <0.001*
*Significance was set at P<0.05.

TABLE 2 - Thoracic Spine Complaint Rates Prebariatric and Postbariatric Surgery
Thoracic Spine Complaints Prebariatric (%) Postbariatric (%) P
Any thoracic 2.91 2.57 <0.001*
Thoracic radicular pain 0.46 0.27 <0.001*
Thoracic pain 0.02 0.01 0.967
Thoracic costochondritis 0.41 0.19 <0.001*
Thoracic disc degeneration 0.05 0.03 0.919
Thoracic disc herniation 0.05 0.03 0.919
Thoracic disc herniation with myelopathy 0.03 0.01 0.963
Thoracic disc space infection 0.03 0.03 0.938
Thoracic vertebra dislocation 0.00 0.00
Thoracic fracture 0.33 0.14 0.243
Thoracic spontaneous compression fracture 1.14 0.78 <0.001*
Thoracic fracture—paralysis to upper spine 0.00 0.00 0.996
Thoracic fracture—paralysis to lower spine 0.02 0.00 0.990
Thoracic disc space infection 0.03 0.03 0.938
Thoracic vertebra infection 0.42 1.12 <0.001*
Thoracic postlaminectomy syndrome 0.07 0.05 <0.001*
Thoracic spinal stenosis 0.05 0.02 0.941
Thoracic spondylosis 0.09 0.04 0.875
Thoracic sprain 0.00 0.01 0.992
*Significance was set at P<0.05.

TABLE 3 - Lumbar Spine Complaint Rates Prebariatric and Postbariatric Surgery
Lumbar Spine Complaints Prebariatric (%) Postbariatric (%) P
Any lumbar 5.39 3.92 <0.001*
Lumbar coccygodynia 0.01 0.01 0.986
Lumbar disc degeneration 0.83 0.51 <0.001*
Lumbar disc herniation 0.00 0.00
Lumbar disc herniation with myelopathy 0.10 0.04 0.863
Lumbar disc space infection 0.18 0.11 0.032
Lumbar fracture 0.48 0.20 0.404
Lumbar fracture with paralysis 0.01 0.00 0.990
Lumbar spontaneous compression fracture 1.14 0.78 <0.001*
Lumbar vertebra infection 0.42 1.12 <0.001*
Lumbar postlaminectomy syndrome 0.07 0.05 <0.001*
Lumbar radiculitis 0.46 0.27 <0.001*
Lumbar spinal stenosis 1.41 0.68 <0.001*
Lumbar spondylolisthesis 0.35 0.21 <0.001*
Lumbar spondylolisthesis—congenital 0.09 0.06 <0.001*
Lumbar spondylosis without myelopathy 0.87 0.47 <0.001*
Lumbar spondylosis with myelopathy 0.07 0.03 0.905
*Significance was set at P<0.05.

Spinal Surgery Pre-BS and Post-BS

Rates of spine surgery in bariatric patients were low overall, but significantly decreased following BS, including all posterior fusions (0.88%–0.57%), anterior fusions (1.05%–0.57%), and decompression procedures (1.55%–0.85%, all P<0.001, Table 4).

TABLE 4 - Spine Procedure Rates Prebariatric and Postbariatric Surgery
Spine Procedures Prebariatric (%) Postbariatric (%) P
Posterior fusion 0.88 0.57 <0.001*
Anterior fusion 1.05 0.57 <0.001*
Combined approach fusion 0.55 0.27 <0.001*
Corpectomy 0.06 0.07 0.865
Two to three levels fused 0.94 0.66 <0.001*
Four to eight levels fused 0.35 0.19 <0.001*
Nine or more levels fused 0.03 0.02 0.949
Interbody 0.67 0.54 <0.001*
Decompression 1.55 0.85 <0.001*
Revision fusion 0.13 0.12 <0.001*
Prior history of spinal fusion 0.51 0.75 <0.001*
*Significance was set at P<0.05.

Adjusted Analysis

Multivariable logistic regression testing revealed that patients who did not have BS were more likely to have encounters associated with several cervical, thoracic or lumbar spinal diagnoses and procedures, relative to patients who received BS (Table 5). This was especially observed for cervical spontaneous compression fracture (95% CI: 2.182; P<0.001), cervical disc degeneration (95% CI: 4.037; P<0.001), cervical neck pain (95% CI: 2.489; P<0.001), thoracic radicular pain (95% CI: 4.646; P<0.001), thoracic fracture (95% CI: 3.646; P<0.001), lumbar spondylosis (95% CI: 6.207; P<0.001), lumbar spinal stenosis (95% CI: 7.029; P<0.001), and posterior procedures (95% CI: 3.670; P<0.001).

TABLE 5 - Spine Diagnoses and Procedure Odds Ratios for Nonbariatric Morbidly Obese Population
Spine Diagnoses and Procedures Odds Ratio Lower CI Upper CI P
Any cervical, thoracic, or lumbar
 Cervical spontaneous compression fracture 2.182 1.920 2.480 <0.001*
 Cervical disc herniation 2.587 2.171 3.083 <0.001*
 Cervical spondylosis with myelopathy 2.973 2.384 3.708 <0.001*
 Cervical neck pain 2.489 2.122 2.919 <0.001*
 Cervical disc degeneration 4.037 3.229 5.046 <0.001*
 Cervical radiculitis 4.132 3.166 5.395 <0.001*
 Thoracic radicular pain 4.646 3.922 5.503 <0.001*
 Thoracic spontaneous compression fracture 2.182 1.920 2.480 <0.001*
 Thoracic fracture 3.646 2.769 4.802 <0.001*
 Thoracic disc degeneration 6.881 4.114 11.58 <0.001*
 Lumbar spontaneous compression fracture 2.182 1.920 2.480 <0.001*
 Lumbar spondylosis 6.207 5.444 7.076 <0.001*
 Lumbar spinal stenosis 7.029 6.283 7.865 <0.001*
 Lumbar disc degeneration 5.604 4.943 6.353 <0.001*
 Lumbar radiculitis 4.646 3.922 5.503 <0.001*
 Lumbar spondylolisthesis 5.862 4.798 7.162 <0.001*
 Decompression 4.260 3.840 4.726 <0.001*
 Anterior only 3.385 2.862 4.002 <0.001*
 Posterior only 3.670 3.091 4.358 <0.001*
 Combined 5.876 4.946 6.981 <0.001*
 Two to three levels fused 3.682 3.267 4.150 <0.001*
*Significance was set at P<0.05.
CI indicates confidence interval.

Obesity-Related Comorbidities Pre-BS and Post-BS

In looking at other comorbidities affected by high body mass, we found that BS significantly lowered the comorbidity burden for many specific factors (Appendix 1, Supplemental Digital Content 1, https://links.lww.com/CLINSPINE/A228). These include hypertension rates (69.8%–67.1%), high cholesterol (23.1%–12.6%), musculoskeletal conditions (37.7%–30.9%), asthma (13.1%–11.3%), osteoarthritis (10.9%–7.1%), uncontrolled diabetes (9.1%–8.2%), and rheumatoid arthritis (3.0%–2.6%, all P<0.001).

DISCUSSION

According to some recent estimations, the vast majority (nearly 80%) of patients treated for spinal disorders in the United States can be classified as obese.11 This demographic has a high comorbidity burden, wide variety of degenerative spinal conditions and is at elevated risk of complications following treatment.12,13 BS has been used as an intervention that promotes preoperative weight loss in order to reduce the risk of morbidity following other types of surgery in obese patients.14 Patients with history of BS were found to have lower overall complication rates after spine surgery than morbidly obese patients who did not receive BS.15 However, not much is known about the effects of BS on rates of symptomatic spinal disorders and spine surgery. As the obese population is at increased risk of spinal conditions and BS is being utilized more frequently,16 further investigation into the effects of BS on spinal disorders is required. Our findings contribute to the literature on the impact of BS on comorbidities, and support the recommendation that BS can successfully be used preoperatively to mitigate spinal ailments.

In the present study we found that cervical, thoracic and lumbar spinal conditions, ranging from spondylosis to compression fractures, decreased significantly following BS. These results held when controlling for age, sex, comorbidities and in a control group of morbidly obese with no history of bariatric procedures. Our findings suggest that, among the overweight and obese populations, many spinal disorders may be ameliorated or frankly obviated through BS-induced weight loss. Aside from the reduction in mechanical load,6 a possible mechanism behind the relationship between BS-induced weight-loss and consequent symptom reduction in spinal disorders, like thoracic radicular back pain, is the suppression of adipose-induced systemic inflammation.17 The chronic, low-grade inflammation characteristic of obesity contributes to insulin and leptin resistance, dyslipidemia, lipotoxicity, increased oxidative stress, and impaired antioxidant defense through a myriad of mechanisms.18

Although the weight loss and spine symptom reduction resulting from BS are well documented and further supported by our results, the evidence that BS may have long-term adverse effects on bone health must be considered.19,20 It is reported that a third of BS patients suffer from malnutrition because of malabsorption, likely the product of the decreased gastrointestinal surface areas created by BS procedures.16 A recent study found that obese patients lost considerable weight following BS but also experienced a great reduction in muscle mass, bone mineral density and vitamin D levels.21 Other studies have reported similar findings.19,20 Moreover, a study found that roux-en-Y gastric bypass, a type of BS procedure, caused increased risk of bone metabolic disease, the most common of which is osteoporosis, whose morbidity is substantial.22 Low bone mineral density and vitamin D deficiency has been shown to be predictive of fractures.23 As such, it is suggested that fracture may be seen as a delayed complication of BS.16 Further investigation into the impact of BS on bone health and fracture risk is critical, as bone metabolic disease and fractures cause a high morbidity and mortality in many populations, especially the elderly.

Consistent with the well-established positive impact of BS on overall health, our results showed a reduction in a number of obesity-related comorbidities including musculoskeletal conditions, osteoarthritis, asthma, and rheumatoid arthritis. These findings provide further evidence of the health benefits of BS.

The results presented here hold important meaning for physicians, surgeons, patients, and insurers. This study was performed in a large population of bariatric patients from the state of New York using a dataset that allows linked surveillance over multiple hospitalizations and health care encounters. We believe that the sociodemographic characteristics of the population of New York, as well as the size of the sample we consider, enable translation of these findings to a broader American context.

Our findings indicate substantial reductions in symptomatic spinal disorders following BS, including most degenerative disorders involving the cervical, thoracic, and lumbar spine. It is unlikely that BS is resulting in structural changes to the degenerative spine, rather meaningful improvements in BMI and reduced systemic inflammation associated with weight loss are leading to these underlying disorders proving less symptomatic. Consequently, this appears to culminate in meaningful reductions in spine surgical interventions overall and improvements in comorbidity profiles that may render spinal surgery safer should it ultimately be warranted. On the basis of this work, we believe that BS for qualifying individuals should be considered before recommendations for elective spine surgical interventions. In some instances, the need for spine surgery may be eliminated following BS and in others the surgery itself may be rendered safer and less likely to result in postsurgical morbidity.

The results of this effort should not be accepted without acknowledging several limitations. This study utilized the NYSID, a New York state database that collects patient data across multiple visits to New York hospitals using billing codes. As such, there is limited granularity in the data. Errors in coding cannot be quantified but may have an influence on our estimation regarding the incidence of spinal disorders and other attendant conditions, both before and after BS. As NYSID is a claims-based registry, we are limited to consider only the variables captured by NYSID mandate, and the exact symptoms associated with each diagnosis, as well as the factors that play into the recommendation for surgery, cannot be characterized. We realize that there is the potential for residual confounding to influence or final conclusions to some extent. In addition, as this dataset only collects information regarding hospital encounters that occur within New York State, any out-of-state visits would not be captured, potentially impacting our ability to capture a patient’s full course of care. This effort is also unable to characterize any of the adverse long-terms effects of BS on bone health in general or cost utility for such interventions in a spine surgical population. These realities suggest viable lines of research going forward.

This study found that the rate of health care encounters for both spinal disorders and spine surgical procedures were reduced following BS in a morbidly obese patient population. These findings support the value of BS as a means to reduce the need for spine surgical interventions overall, while simultaneously rendering those that are necessary less prone to postsurgical complications.

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Keywords:

bariatric surgery; spine surgery; morbid obesity; spinal symptoms

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