The Spine Journal 9 (2009) 454–463

Prospective assessment of axial back pain symptoms before and afterbariatric weight reduction surgery

Paul Khoueir, MDa,*, Mary Helen Black, MSb, Peter F. Crookes, MDc,Howard S. Kaufman, MDc, Namir Katkhouda, MDc, Michael Y. Wang, MDd

aDepartment of Neurological Surgery, Hopital Sacre-Coeur, Universite de Montreal, 5400 Boulevard, Gouin O., Montreal, Quebec H4J 1C5, CanadabDepartment of Preventive Medicine, Division of Biostatistics, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA

cDepartment of General Surgery, Keck School of Medicine, USC University Hospital, 1500 San Pablo Street,

University of Southern California, Los Angeles, CA 90033, USAdDepartment of Neurological Surgery, University of Miami Miller School of Medicine, 1095 NW 14th Terrace, Lois Pope LIFE Center, Miami, FL 33136, USA

Received 25 March 2008; accepted 6 February 2009

Abstract BACKGROUND: The prevalence of obesity i

FDA drug/device

Author disclosure

1529-9430/09/$ – see

doi:10.1016/j.spinee.2

n developed countries has reached alarming levels,doubling in the United States since 1980. Although obese patients with chronic low back pain arefrequently advised to lose weight, the association between these medical conditions remainsunproven.PURPOSE: This study prospectively assessed clinically reported changes in chronic axial lowback pain symptoms after weight reduction from bariatric surgery for morbid obesity.STUDY DESIGN: Prospective longitudinal study.PATIENT SAMPLE: Fifty-eight consecutive patients with morbid obesity and chronic axial lowback pain undergoing bariatric surgery over a period of 6 months. Patients were considered mor-bidly obese if they were 50% to 100% above their ideal body weight or having a body mass index(BMI) greater than 40.OUTCOME MEASURES: Visual Analog Scale (VAS) for axial low back pain, Short Form-36(SF-36) Health Survey, and Oswestry Disability Index (ODI).METHODS: Patients undergoing weight reduction surgery were assessed preoperatively and post-operatively at 12 months with validated clinical measures for axial back pain and disability (VAS,SF-36, and ODI). Bariatric surgery parameters included demographic data, weight, and BMI. Sta-tistical analysis included paired t tests and multiple regression techniques.RESULTS: Of the initial 58 patients, 38 (65%) completed both preoperative (Pre-Op) and postop-erative (Post-Op) questionnaires at 12 months. These 38 subjects included 30 women and 8 men,with an age range of 20 to 68 years (mean 48.4610.1). Overall, these patients showed a decreasein mean weight from 144.52641.21 kg Pre-Op to 105.59629.24 Post-Op (p!.0001) and BMI from52.25612.61 kg/m2 Pre-Op to 38.3269.66 Post-Op (p!.0001).

Patients demonstrated a statistically significant mean 44% decrease in axial back pain on the VASscale (p5.006; 5.263.35 Pre-Op, to 2.963.1 Post-Op). Analysis of the SF-36 major componentsrevealed that patients experienced significant increases in mean physical health by 58%(p!.0001; 44.5620.09 to 70.24626.84) and in median mental health by 6% (p5.03; 7067.14to 73.39611.78). Patients also showed statistically significant 24% decrease in Post-Op ODI scorefor physical disability (p5.05) from 26.75616.56 Pre-Op to 20.35618.71 Post-Op (p5.05).CONCLUSION: This study suggests that the substantial weight reduction after bariatric surgerymay be associated with moderate reductions in preexisting back pain at early-follow-up. This effectdid not appear to be the result only of an overall improvement in well-being associated with weightloss. However, larger randomized controlled clinical studies with longer-term follow-up are neededto definitively determine a causal relationship. � 2009 Elsevier Inc. All rights reserved.

status: not applicable.

s: none.

* Corresponding author. Department of Neurological Surgery, Hopital

Sacre-Coeur, Universite de Montreal, 5400 Boulevard Gouin O., Montreal,

Quebec H4J 1C5, Canada.

E-mail address: khoueir@hotmail.com (P. Khoueir)

front matter � 2009 Elsevier Inc. All rights reserved.

009.02.003

455P. Khoueir et al. / The Spine Journal 9 (2009) 454–463

Keywords: Lumbago; Chronic back pain; Obesity; Spondylosis; Bariatric surgery; Weight loss; Short Form-36; Oswestry

Disability Index; Body mass index; Spine

Introduction

The prevalence of obesity in developed nations hasreached alarming levels, affecting all socioeconomicgroups, irrespective of age, sex, or ethnicity. In the UnitedStates, the prevalence of obesity, defined as a body mass in-dex (BMI) greater than or equal to 30 kg/m2, has doubledsince 1980 [1–6]. Although the burden obesity places onsociety can be difficult to quantify, there is no question thatthis disorder leads to shorter life expectancies, limitationsin activities of daily living, reduced workforce productivity,and added medical costs [7–12].

The effects of an increased body mass on the musculoskel-etal system have primarily been studied in the lower extrem-ity joints. In a retrospective review, among 204 subjects whoreceived either a total hip or knee replacement, 72% wereobese compared with only 26% of obese in the general pop-ulation [13]. Similarly, in another population-based casecontrol study, the authors determined odds ratio for a BMIless than 20 kg/m2 and greater than 36 kg/m2 relative to a nor-mal BMI of 24–25 kg/m2. They found that the risk of knee os-teoarthritis increased from 0.1 for a BMI !20 kg/m2 to 13.6for a BMI of 36 kg/m2 or higher [14].

However, the effects of obesity on the lumbar spine aremore controversial [15,16]. Some studies have reported anassociation between obesity and lumbar spondylosis[15,17–19], whereas others have shown no association[20–22]. Chronic axial low back pain, such as obesity, iscommon, affecting more than 70% of adults episodicallyand 2% to 7% chronically [23,24]. The etiology of lumbagois diverse, and investigations into its risk factors have failedto identify factors with a strong correlative impact. Conse-quently, it is still unclear what types of strategies could bedeveloped to prevent or alleviate axial pain symptoms.

As obese patients are at risk for osteoarthritis in weightbear-ing joints, such as knee, hip, and feet, the concept that obesitypredisposes a patient to lumbar spondylosis and back pain mayseem intuitive [13,14,25]. Casual recommendations made byclinicians that obese patients with chronic back pain loseweight to ameliorate their symptoms may be prudent [26].However, there has been little scientific evidence to substanti-ate the notions that obesity contributes to the onset of back paineither acutely or chronically; and weight loss results in a reduc-tion of the severity or periodicity of these complaints.

There have been several studies that have examined theassociation between radiographic evidence of lumbar spon-dylosis and obesity. In a longitudinal prospective study,O’Neill et al., recruited 681 women and 499 men older than50 years to study the association between the presence ofanterior osteophytes on lateral lumbar radiographs and riskfactors such as obesity and physical activity levels [17].They noted that increasing BMI was associated with more

frequent findings of osteophytes at the lumbar spine [17].Biering-Sorensen and colleagues noted that the absoluteweight and BMI are significantly higher among patientsin their seventh decade with spondylosis [18]. However,other reports have shown no association between BMIand low back–related problems [20–22]. In one study, Man-chikanti et al. found that the incidence of clinically evidentfacet joint disease mediating pain was similar betweenobese and nonobese patients [16].

This study attempts to explore the association betweenchanges in BMI and clinical symptoms of axial low backpain. Because patients undergoing bariatric surgeryfrequently experience dramatic and reliable weight loss ofbetween 30 and 60 kg in the first year after operative inter-vention, they are an ideal longitudinal cohort for assessingthe effects of weight reduction on low back pain. Thus,a cohort of morbidly obese patients undergoing bariatricsurgery with mechanical low back pain was followed overa period of 12 months to assess the effect of weight loss ontheir chronic axial back pain and disability.

Methods

Study design

After Institutional Board Review approval, 58 patientswith chronic axial low back pain scheduled to undergoa bariatric surgery at the University of Southern California,were consecutively and prospectively enrolled in the studyover a period of 6 months. To be eligible, patients had to beat least 18 years of age, and needed to have a BMI greaterthan 40 kg/m2. Patients with a BMI between 35 and39.9 kg/m2 were also included if they were 50% to 100%more than their ideal weight. They also had to reporta two-year history of chronic mechanical low back painwith or without radiculopathy that causes significantdisability. Patients were excluded from the study if theyunderwent a successful diet or exercise program in the lastfive years, if they suffered mainly from radicular pain withminimal low back pain, or had prior lumbar or bariatric sur-gery. Preoperative data were collected one week before un-dergoing their bariatric surgery. Demographic data includedage, height, medical comorbidities, weight, and BMI. Out-come measures included the Visual Analog Scale (VAS)scored for axial low back pain, the Short Form-36 (SF-36) standard quality-of-life questionnaire, and OswestryDisability Index (ODI) as a measure of lumbar symptoms.Postoperative demographic data were collected from thepatients’ visit to their bariatric surgeon at 12 months. Also,an independent observer helped in gathering the responsesto the outcome measures questionnaires by contacting thepatients at the end of this 12-month period.

Table

Demographic data for subjects with a completed questionnaire at

12 months post-operation

Data Mean (SD)

Number of subjects 38

Age (y) 48.4 (10.1)

Gender

Men (%) 8 (21)

Women (%) 30 (79)

Height (m) 1.66 (0.09)

Pre-Op weight (kg) 144.5 (41.21)

Pre-Op BMI (kg/m2) 52.3 (12.6)

BMI, body mass index; Pre-Op, preoperative; SD, standard deviation.

ContextThe relationship between obesity and back pain is likely

complex with multiple contributing factors including

culture, emotional health, physical fitness and biome-

chanics. The more focused relationship between weight

loss and reduction in low back pain is commonly as-

sumed but remains scientifically unclear. This study

aims to provide some insight using a prospective assess-

ment of patients undergoing bariatric surgery.

ContributionThe authors found that substantial weight reduction fol-

lowing bariatric surgery may be associated with moder-

ate reductions in pre-existing low back pain one year

after surgery.

ImplicationsThe findings are interesting and the authors do a good

job of recognizing the limitations of the study. There

is no control group; the natural history of low back pain

in this obese population is unclear; the relevant clinical

effect is undefined; only 65% of patients had complete

follow-up; the follow-up is relatively short; and the pa-

per should not be taken to suggest that reduction in low

back pain should be an indication for bariatric surgery.

The real strength of the paper rests in its providing

a framework for more rigorous examination of this

topic.

dThe Editors

456 P. Khoueir et al. / The Spine Journal 9 (2009) 454–463

The SF-36 Health Survey is a 36-item questionnaire thatmeasures two domains of reported health status to assess qual-ity of life: physical and mental. Each of these domains is com-posed of four distinct subcategories. The physical healthcomponent comprises pain, physical functioning, role limita-tions because of physical problems, and general health percep-tion, whereas social functioning, role limitations because ofemotional problems, mental health/emotional well-being,and vitality describe the mental health component [27]. Itemanswers are coded, and raw scores are transformed to a scalefrom 0 to 100, where a higher score indicates better health sta-tus. The transformed scores for each group of items withineach component or category are then averaged to yield a com-posite component or category score.

The ODI is a 10-item questionnaire that is used to assesslow back pain by determining its impact on daily activities.Each item is coded on a scale from 0 to 5, where higher valuesindicate more severe impact of back pain on daily living. Item

scores are then summed and divided by 50, yielding a percentdisability score. An ODI score of 0% to 20% indicates mini-mal disability, 21% to 40% moderate disability, 41% to 60%severe disability, and 61% to 100% most severe disability [28].

Statistical analysis

Statistical analysis was performed to assess preoperativeand postoperative differences in subject characteristics, aswell as differences in outcome measures indicated by the vi-sual analog scale, SF-36, and ODI questionnaires. Paired ttests were used to analyze preoperative versus postoperativedifferences in weight (kg), BMI, and perceived pain scale.For SF-36 and ODI reported outcomes, analyses were per-formed with two-tailed paired t tests and mean differenceswith standard deviations were reported. If paired responsedifferences were not approximately normally distributed,the Wilcoxon sign rank test was used, and median differenceswith seventy-fifth percentile upper ranges were reported.For examination of age as a possible effect modifier, agewas dichotomized at the median (46.5 y). Generalized linearmodels were used to assess the magnitude and significance ofassociation between preoperative/postoperative change inBMI and change in VAS, as well as change in SF-36 andODI outcomes. Change in BMI is defined as (postoperative[Post-Op] BMI � preoperative [Pre-Op] BMI) and changein pain scale, SF-36 and ODI measured outcomes are alsodefined as simple differences (Post-Op � Pre-Op).

All models were adjusted for age, sex, and number ofmonths since surgery. The association between change inBMI and change in perceived health outcomes is shownas model-predicted delta outcome versus delta BMI, afteradjustment for age, gender and number of months sincesurgery. The level of statistical significance was set atp5.05 for all tests. All statistical analyses were performedwith SAS (v 9.1; SAS Institute, Cary, NC, USA).

Results

Patient demographics

The patient population consisted of 58 subjects, 38 ofwhom have successfully completed the questionnaires at

Fig. 1. Preoperative (Pre-Op) versus postoperative (Post-Op) mean (Top)

BMI (kg/m2) and (Bottom) weight (kg) shown with standard deviation

(n534). ***p!.0001 for difference between mean Pre-Op and Post-Op

BMI or weight.

Fig. 2. Preoperative (Pre-Op) versus postoperative (Post-Op) differences

(Top) Short Form-36 (SF-36) physical and mental components, (Middle)

SF-36 physical and mental components stratified by age, and (Bottom) SF-

36 physical and mental components stratified by gender. Scaled scores are

shown as mean (standard deviation) or median (þ) (seventy-fifth percentile);

**p!.05 for difference in mean or median Pre-Op versus Post-Op SF-36 com-

ponent outcomes; ***p!.01 for difference in mean or median Pre-Op versus

Post-Op SF-36 component outcomes; and ****p!.001 for difference in mean

or median Pre-Op versus Post-Op SF-36 component outcomes.

457P. Khoueir et al. / The Spine Journal 9 (2009) 454–463

12 months post-op. Thirty-five percent of patients eitherrefused to continue adhering to the study or were out ofreach after three attempts made by the independentobserver.

These 38 subjects included 30 women and 8 men, in theage range 20 to 68 years (mean, 48.4610.1 y). Demo-graphic data included age (y), gender, weight (kg), andBMI, shown in the Table.

Four different procedures were performed by three sur-geons specializing in bariatric surgery, with the majority(N536) receiving a laparoscopic Roux-en-Y gastric bypass.Fourteen patients had an open Roux-en-Y gastric bypass, fivehad a duodenal switch gastric bypass (DS), and four under-went a sleeve gastrectomy. All four procedures produced sig-nificant reductions in weight after the intervention. Overall,the mean change in weight at one-year follow-up was from144.52641.21 kg (Pre-Op) to 105.59629.24 kg (Post-Op;p!.0001). This translated into a change in mean BMI from52.25612.61 kg/m2 (Pre-Op) to 38.3269.66 kg/m2 (Post-Op) which was statistically significant (p!.0001) as shownin Fig. 1. The range of weight loss at 12 months was between30 to 100 kg per patient. On average, the BMI and raw weightdecreased 26.9% and 27.1%, respectively, one year aftersurgery.

Statistical analysis between patients having responded toPost-Op questionnaires (n538) and those who were lost tofollow-up (n520), have shown that the two groups

significantly differed on age (p5.0016), but not sex(p5.7319), delta weight (p5.7458), or delta BMI(p5.5283). Patients having responded to the Post-Op surveywere older with a mean difference of 9 years.

General health measures

Analysis of the SF-36 major components revealed thatpatients experienced significant improvements in both thephysical health from 44.5620.09 to 70.24626.84 (p!.0001)and mental health from 7067.14 to 73.39611.78 (p5.03)categories (Fig. 2, top). The median mental health score

Fig. 3. Preoperative (Pre-Op) versus postoperative (Post-Op) differences in (Top) Short Form-36 (SF-36) subcategories, (Middle) SF-36 subcategories strat-

ified by age, and (Bottom) SF-36 subcategories stratified by gender. Scaled scores are shown as mean (standard deviation) or medians (þ) (seventy-fifth

percentile). **p!.05 for difference in mean or median Pre-Op versus Post-Op SF-36 component outcomes; ***p!.01 for difference in mean or median

Pre-Op versus Post-Op SF-36 component outcomes; and ****p!.001 for difference in mean or median Pre-Op versus Post-Op SF-36 component outcomes.

458 P. Khoueir et al. / The Spine Journal 9 (2009) 454–463

Fig. 4. (Top) Preoperative (Pre-Op) versus postoperative (Post-Op) mean

Visual Analog Pain Scale for axial low back symptoms shown with stan-

dard deviation (n530). ***p5.006 for mean difference between Pre-Op

and Post-Op pain scale. (Bottom) Number of patients improved, remained

stable, or deteriorated in their mean pain scale from Pre-Op to Post-Op.

459P. Khoueir et al. / The Spine Journal 9 (2009) 454–463

increased 6%, and the mean aggregate physical health pa-rameter increased approximately 58%. These changes dif-fered by age and gender, with improvements in the medianmental health score significantly higher with men (p5.008)and younger patients (p5.03), but not significantly differentwith women or among older individuals (Fig. 2, middle andbottom). The SF-36 physical component differences re-mained significant whether stratified by age or gender.

Patients showed a statistically significant improvementin five of the eight SF-36 quality-of-life categories: bodilypain (p5.015), physical functioning (p!.0001), role-physical (p5.001), general health perception (p!.0001),and vitality (p5.001) as shown in Fig. 3, top. Analysis ofdifferential effects by age and gender revealed a significant

Fig. 5. Preoperative (Pre-Op) versus postoperative (Post-Op) Oswestry

Disability Index (ODI) mean percent shown with standard deviation

(n538). ***p5.05 for mean difference between Pre-Op and Post-Op

percent disability index.

improvement in relief from pain (p5.01) and role-physical(p5.009) in the older age group that was not observed inthe younger age group. Similarly, men reported an improve-ment in relief from pain (p5.01) and social function(p5.02) that was not observed in women, and women re-ported an improvement in role-physical (p5.009), whereasmen did not (Fig. 3, middle and bottom).

Changes in axial low back pain and related disability

Patients showed a decrease from 5.263.35 to 2.963.1 inmean reported VAS scores for axial low back pain whichrepresents a 44% overall decrease from Pre-Op to Post-Op (p5.006) (Fig. 4, top). Of the patients, 68.4% improved,13% remained stable, and 18.4% deteriorated in their VASscores one year after the bariatric surgery (Fig. 4, bottom).None of these patients subsequently underwent spine sur-gery for their residual low back pain during this 12-monthobservation period. Patients also showed marginally signi-ficant 24% decrease in Post-Op ODI score for physicaldisability from 26.75616.56 Pre-Op to 20.35618.71Post-Op (p5.05) (Fig. 5).

The extent to which the pre- and postoperative painscale, SF-36, and ODI differences can be attributed tochanges in patient weight and BMI are shown in Fig. 6.Although not found to be statistically significant, deltaBMI shows an increasing trend for association with theVAS (correlation coefficient [corr. coeff.]50.047, p5.78),a decreasing trend for association with SF-36 measuredphysical (corr. coeff.5�1.615, p5.10) and mental compo-nents (corr. coeff.5�0.4638, p5.60), and a decreasingtrend for association with the ODI score (corr. coeff.5�0.3917; p5.45).

Discussion

Obesity is frequently cited as one of the more pressinghealth problems in the United States. Known risk factorsfor obesity include female gender, lower socioeconomic sta-tus, and living in an urban lifestyle [29]. The World HealthOrganization adult BMI database indicates that on average,women are more obese than men, whereas men are morelikely to be pre-obese than women [30,31]. Similarly, in thisstudy, women were predominantly more represented thanmen in a proportion of 3.3:1. Although disparity exists be-tween men and women, the general trend in obesity is gener-ally upward in both sexes over the last 30 years [31].

Bariatric surgery is one intervention that can reliably in-duce a significant weight loss in obese patients [32]. In onereview, for instance, the BMI decreased significantly from53.4 kg/m2 (preoperatively) to 31.2 kg/m2 (postoperatively)and was maintained for up to 5 years [33]. Similarly, in thispresent study, there was a statistically significant decreasein BMI from 52.25 kg/m2 to 38.32 kg/m2, and weight from144.52 kg to 105.59 kg (Fig. 1).

Fig. 6. The association between change in body mass index (BMI) and change in perceived health outcomes shown as model-predicted delta (Top) Visual

Analog Scale versus delta BMI (correlation coefficient [corr. coeff.] 5 0.047, p5.78); (Middle) SF-36 physical (corr. coeff.5�1.615, p5.10) and mental

score versus delta BMI (corr. coeff.5�0.4638, p5.60); and (Bottom) Oswestry Disability Index (ODI) versus delta BMI (corr. coeff.5� 0.3917; p5.45), after

adjustment for age, gender, and number of months since surgery.

460 P. Khoueir et al. / The Spine Journal 9 (2009) 454–463

Effect of weight loss on general health

This procedure is associated with not only weight lossbut also overall improvement in physical and mentalwell-being. Both physical and mental health SF-36 compo-nents significantly increased postoperatively. Although

weight loss seems to significantly influence both categories;postoperative physical health scores increased by 58%while mental health only by 6% (Fig. 2, top). When phys-ical and mental health scores were further subdivided intodifferent subcategories, all categories related to physicalhealth (bodily pain, physical function, role-physical,

461P. Khoueir et al. / The Spine Journal 9 (2009) 454–463

general health) significantly improved Post-Op, whereas vi-tality was the only mental health category that significantlyincreased (Fig. 3, top). Other studies in the literature haveobtained similar results. Velcu et al., for instance, noted thatdisability related to obesity and SF-36 scores improved sig-nificantly after such procedures [33]. In another report,Gorman et al. after completing 35 Roux-en-Y proceduresfor morbidly obese patients found significant increase inmental and physical health components of the SF-12 ques-tionnaire [34]. From baseline, physical status improved by21.2 points while the mental health score improved by only9.3 points at the 12 months follow-up. Thus, weight reduc-tion associated with bariatric surgery seems to have a largerimpact on the physical wellness of an individual than men-tal well-being.

Effect of weight loss on axial low back pain

Weight loss associated with gastric bypass surgery notonly produces improvement in general health but alsoreduces physical pain. In our study, low back pain–specificvisual analog scale scores (Fig. 4, top) were statisticallysignificantly reduced by 44% from the preoperative to thepostoperative setting.

Reduction in chronic low back pain after gastric bypasssurgery has also been achieved and shown in other reports.Melissas et al. studied a European cohort and noted that of29 obese patients suffering from low back pain, only 10patients continued to have symptoms after their bariatricsurgery [35]. The VAS, Roland Morris, ODI, and WaddellDisability Index scores were all statistically improved twoyears after surgery [36]. They concluded that surgicalweight loss significantly improved the degree of functionaldisability of morbidly obese patients suffering from lowback pain.

Hooper et al., in a similar study, determined the preva-lence of painful musculoskeletal conditions in obese sub-jects before and after weight loss after bariatric surgery.Musculoskeletal complaints had been present in 100% ofobese subjects before and 23% after weight loss. The great-est improvement occurred in the cervical and lumbar spine,the foot, and fibromyalgia symptoms, which decreased by90%, 83%, 83% and 92%, respectively. These findingswere, however, subjectively reported with no reference toVAS scores [37].

Improved sense of well-being versus improvementsin musculoskeletal pain?

It is unclear from the studies mentioned here if thepatient’s improvement in back pain as assessed subjectivelyor with VAS scores was the result of mechanical or muscu-loskeletal changes, or as a result of the overall improvementin well-being that accompanies such dramatic weight loss.In this study, an attempt was made to determine if there wasan independent association between reduced complaints of

chronic low back pain and weight loss. This was accom-plished by assessing the eight subcomponents of the SF-36 scores. Using this approach, it was found that scoresspecifically related to bodily pain in the SF-36 question-naire (Fig. 3, top) were statistically improved in Post-op.By using generalized linear models analysis, a trend inthe expected direction was observed between BMI, weightloss, VAS, and SF-36 scores (Fig. 6, top and middle). Aspatients lost more weight, the VAS further decreasedwhile the SF-36 scores increased. Although it is hard todraw definite conclusion from these results because noneof the associations were found to be statistically significant(probably because of the error generated from small samplesize), they may suggest that both improved general healthand axial low back pain could be related to significantweight loss measures in morbidly obese patients.

Effect of weight loss on disability indices

Reduced levels of disability after bariatric surgery forobese patients have been well documented in the literature.A study by Hawkins et al. evaluated the impact of bariatricsurgery on the ability to work and the effect on state-fundedbenefit claims. Among 79 patients treated with a Roux-en-Ygastric bypass, there was a 32% increase in the number of re-spondents in paid work after surgery (p!.05) [38]. However,few reports discuss the impact of gastric bypass and weightloss on axial low back pain–related disability. In this study,disability related to low back pain significantly decreasedin Post-Op ODI scores compared with Pre-Op (p5.05)(Fig. 5). This is similar to the findings by Melissas et al.who reported improvements in the Roland Morris, ODI,and Waddell Disability Index scores two years after surgery[36]. According to these results, surgical weight loss seems todecrease the degree of functional disability of morbidlyobese patients, especially in improving their overall physicalhealth and in reducing musculoskeletal pain, such as lowback pain.

Subgroups more responsive to weight loss

Although this study represents a small patient cohort, anattempt was made to identify a subgroup of patients whosequality of life better responded to weight reduction. Patientsolder than the median 46 years of age experienced greaterimprovement in SF-36 subcategories, particularly in thephysical health category, including bodily pain (Fig. 3,middle). Differences in SF-36 outcomes were also notedbetween the genders, with the female population experienc-ing less improvement in the mental health subcategory.However, it is difficult to draw definite conclusions fromthese results as only eight male patients partook in thestudy, resulting in higher variances (Figs. 2, bottom and3, bottom).

462 P. Khoueir et al. / The Spine Journal 9 (2009) 454–463

Study limitations

There are several limitations to this study that shouldbe considered. First, the patient sample was small and thefollow-up was for a short duration. Thus, the durability ofthese improvements in pain symptoms as well as thelong-term effects of obesity surgery has not been ade-quately assessed. Second, there was a 35% loss in patientfollow-up because of lack of total patient collaboration incompletely filling-up the questionnaires. Although patientsresponding to Post-op surveys showed similar weight lossand BMI reduction to nonresponders, this loss in patientfollow-up may influence patient outcome and results.Third, the natural history of low back pain remains largelyunknown. We know from certain studies that more than twothirds of patients treated with conservative therapy willeventually improve [39]. Thus, it is difficult to completelydistinguish between patients improved as part of the naturalhistory of their disease, and those improved secondary toweight loss. Fourth, it remains difficult to quantitate thepowerful effect weight reduction has on a patient’s overallperception of well-being, and it is even more difficult toascertain the impact on self-reporting of physical painsymptoms. This study cannot discern the etiology ofpain reduction. Various theories have been proposed toexplain this observation, including changes in spinal bio-mechanics; a reduction in local inflammatory processesfrom mechanical loading; decreased muscular fatigue;and off-loading of the intervertebral disc or facet joints.An ideal follow-up study to investigate these mechanismswould incorporate pre- and postoperative spinal imaging,including magnetic resonance imaging (to assess soft tis-sues) and dynamic radiographs (to assess spinal mechanicsand loading).

Because of these limitations, one should be aware beforesuggesting a bariatric surgery for obese patients solely onlow back pain–related problems. This intervention shouldbe reserved for morbidly obese patients with BMI greaterthan 40 kg/m2 or BMI greater than 35 kg/m2 with serioussecondary comorbidities, such as diabetes, hypertension,cardiovascular disease, and sleep apnea [40]. There are alsoserious complications to bariatric surgery, such as pulmo-nary embolus, anastomotic leakage, abscess, dehiscence;respiratory complications, including prolonged mechanicalventilation; cardiac complications, including acute myocar-dial infarction and cardiac arrest [41]. The mortality rate isestimated to be around 0.08%, and together, pulmonaryemboli, anastomotic leaks, and respiratory failure accountfor 80% of all deaths in the first 30 days after bariatricsurgery. Symptomatic cholelithiasis, dumping syndrome,persistent vomiting, and nutritional deficiencies maypresent as long-term complications [42].

Because of these serious potential complications withsurgery, nonsurgical treatments, such as diet and exerciseprograms, need to be investigated to determine their bene-ficial effects on low back pain in obese patients. This study

shows that important weight loss over a short period of timecould result in reduction in chronic axial back pain. How-ever, it is difficult to extrapolate those results to nonsurgicaltreatments, as they probably do produce less drastic andefficient weight loss over a longer period of time.

Conclusion

This study provides evidence that substantial weightreduction seen after bariatric surgery may result in moder-ate but early reductions in preexisting back pain. Further-more, this effect did not appear to be solely the result ofthe overall improvements in well-being associated withsignificant weight loss. However, larger randomized studieswith longer-term follow-up will be necessary to prove thistreatment effect.

References

[1] Parikh NI, Pencina MJ, Wang TJ, et al. Increasing trends in incidence

of overweight and obesity over 5 decades. Am J Med 2007;120:

242–50.

[2] Christakis NA, Fowler JH. The spread of obesity in a large social

network over 32 years. N Engl J Med 2007;357:370–9.

[3] Garson A Jr, Engelhard CL. Attacking obesity: lessons from

smoking. J Am Coll Cardiol 2007;49:1673–5.

[4] Kosti RI, Panagiotakos DB. The epidemic of obesity in children and

adolescents in the world. Cent Eur J Public Health 2006;14:151–9.

[5] Ogden CL, Carroll MD, Curtin LR, McDowell MA, Tabak CJ,

Flegal KM. Prevalence of overweight and obesity in the United

States, 1999-2004. JAMA 2006;295:1549–55.

[6] Ogden CL, Yanovski SZ, Carroll MD, Flegal KM. The epidemiology

of obesity. Gastroenterology 2007;132:2087–102.

[7] Weighing in on obesity: America’s growing health epidemic. Issue

brief. Grantmakers Health 2001;11:1–32.

[8] Birmingham CL, Muller JL, Palepu A, Spinelli JJ, Anis AH. The cost

of obesity in Canada. CMAJ 1999;160:483–8.

[9] Houston DK, Stevens J, Cai J, Morey MC. Role of weight history on

functional limitations and disability in late adulthood: the ARIC

study. Obes Res 2005;13:1793–802.

[10] Peeters A, Bonneux L, Nusselder WJ, De Laet C, Barendregt JJ.

Adult obesity and the burden of disability throughout life. Obes

Res 2004;12:1145–51.

[11] Seidell JC, Verschuren WM, van Leer EM, Kromhout D. Overweight,

underweight, and mortality. A prospective study of 48,287 men and

women. Arch Intern Med 1996;156:958–63.

[12] Zhao L, Zhou B, Wu Y, Li Y, Yang J. [A prospective study on body

mass index and mortality]. Zhonghua Liu Xing Bing Xue Za Zhi

2002;23:24–7.

[13] Harms S, Larson R, Sahmoun AE, Beal JR. Obesity increases the

likelihood of total joint replacement surgery among younger adults.

Int Orthop 2007;31:23–6.

[14] Coggon D, Reading I, Croft P, McLaren M, Barrett D, Cooper C. Knee

osteoarthritis and obesity. Int J Obes Relat Metab Disord 2001;25:622–7.

[15] Liuke M, Solovieva S, Lamminen A, et al. Disc degeneration of the lum-

bar spine in relation to overweight. Int J Obes (Lond) 2005;29:903–8.

[16] Manchikanti L, Pampati V, Singh V, Beyer C, Damron K, Fellows B. Eval-

uation of the role of facet joints in persistent low back pain in obesity: a con-

trolled,prospective, comparativeevaluation.PainPhysician2001;4:266–72.

[17] O’Neill TW, McCloskey EV, Kanis JA, et al. The distribution, deter-

minants, and clinical correlates of vertebral osteophytosis: a popula-

tion based survey. J Rheumatol 1999;26:842–8.

463P. Khoueir et al. / The Spine Journal 9 (2009) 454–463

[18] Biering-Sorensen F, Hansen FR, Schroll M, Runeborg O. The relation

of spinal x-ray to low-back pain and physical activity among 60-year-

old men and women. Spine 1985;10:445–51.

[19] Lean ME, Han TS, Seidell JC. Impairment of health and quality of life

in people with large waist circumference. Lancet 1998;351:853–6.

[20] Mirtz TA, Greene L. Is obesity a risk factor for low back pain? An

example of using the evidence to answer a clinical question. Chiropr

Osteopat 2005;13:2.

[21] Symmons DP, van Hemert AM, Vandenbroucke JP, Valkenburg HA.

A longitudinal study of back pain and radiological changes in the

lumbar spines of middle aged women. II. Radiographic findings.

Ann Rheum Dis 1991;50:162–6.

[22] Verbunt JA, Seelen HA, Vlaeyen JW, et al. Disuse and deconditioning

in chronic low back pain: concepts and hypotheses on contributing

mechanisms. Eur J Pain 2003;7:9–21.

[23] van Tulder M, Koes B, Bombardier C. Low back pain. Best Pract Res

Clin Rheumatol 2002;16:761–75.

[24] van Tulder MW, Koes BW, Assendelft WJ, Bouter LM, Maljers LD,

Driessen AP. [Chronic low back pain: exercise therapy, multidisci-

plinary programs, NSAID’s, back schools and behavioral therapy

effective; traction not effective; results of systematic reviews]. Ned

Tijdschr Geneeskd 2000;144:1489–94.

[25] Felson DT. Weight and osteoarthritis. Am J Clin Nutr 1996;63

(3 Suppl):430S–2S.

[26] Singla AK, Stojanovic M, Barna S, Meyer MA, Carragee EJ.

Persistent low back pain/Dr. Carragee replies. N Eng J Med

2005;353:956–7.

[27] Ware JE Jr, Sherbourne CD. The MOS 36-item short-form health sur-

vey (SF-36). I. Conceptual framework and item selection. Medical

Care 1992;30:473–83.

[28] Fairbank JC, Couper J, Davies JB, O’Brien JP. The Oswestry low

back pain disability questionnaire. Physiotherapy 1980;66:271–3.

[29] Wardle J, Waller J, Jarvis MJ. Sex differences in the association of

socioeconomic status with obesity. Am J Public Health 2002;92:

1299–304.

[30] Martin KS, Ferris AM. Food insecurity and gender are risk factors for

obesity. J Nutr Educ Behav 2007;39:31–6.

[31] Mascie-Taylor CG, Goto R. Human variation and body mass index:

a review of the universality of BMI cut-offs, gender and urban-rural

differences, and secular changes. J Physiol Anthropol 2007;26:

109–12.

[32] Averbukh Y, Heshka S, El-Shoreya H, et al. Depression score predicts

weight loss following Roux-en-Y gastric bypass. Obes Surg 2003;13:

833–6.

[33] Velcu LM, Adolphine R, Mourelo R, Cottam DR, Angus LD.

Weight loss, quality of life and employment status after Roux-en-Y

gastric bypass: 5-year analysis. Surg Obes Relat Dis 2005;1:413–6;

discussion 417.

[34] Gorman RS, Stern DL, Inclan DV, Presutti RJ, Swain JM, Hentz JG.

Outcomes, health status, and medical resource utilization after bariat-

ric surgery. Compr Ther 2006;32:34–8.

[35] Melissas J, Volakakis E, Hadjipavlou A. Low-back pain in morbidly

obese patients and the effect of weight loss following surgery. Obes

Surg 2003;13:389–93.

[36] Melissas J, Kontakis G, Volakakis E, Tsepetis T, Alegakis A,

Hadjipavlou A. The effect of surgical weight reduction on functional

status in morbidly obese patients with low back pain. Obes Surg

2005;15:378–81.

[37] Hooper MM, Stellato TA, Hallowell PT, Seitz BA, Moskowitz RW.

Musculoskeletal findings in obese subjects before and after weight

loss following bariatric surgery. Int J Obes (Lond) 2007;31:114–20.

[38] Hawkins SC, Osborne A, Finlay IG, Alagaratnam S, Edmond JR,

Welbourn R. Paid work increases and state benefit claims decrease

after bariatric surgery. Obes Surg 2007;17:434–7.

[39] Smith SE, Darden BV, Rhyne AL, Wood KE. Outcome of unoperated

discogram-positive low back pain. Spine 1995;20:1997–2000;

discussion 2000–1.

[40] Monteforte MJ, Turkelson CM. Bariatric surgery for morbid obesity.

Obes Surg 2000;10:391–401.

[41] Weller WE, Hannan EL. Relationship between provider volume and

postoperative complications for bariatric procedures in New York

State. J Am Coll Surg 2006;202:753–61.

[42] Virji A, Murr MM. Caring for patients after bariatric surgery. Am

Fam Physician 2006;73:1403–8.