The role of obesity in the biomechanics and radiological changes of the spine: an in vitro study

Obesity increases the odds of intervertebral disc herniation and spinal stenosis; an MRI study of 1634 low back pain patients

PURPOSE

The objective of this study was to examine the relationships between BMI and intervertebral disc degeneration (DD), disc herniation (DH) and spinal stenosis (SS) using a large, prospectively recruited and heterogeneous patient population.

METHODS

Patients were recruited through the European Genodisc Study. An experienced radiologist scored MRI images for DD, DH and SS. Multivariate linear and logistic regression analyses were used to model the relationship between these variables and BMI with adjustment for patient and MRI confounders.

RESULTS

We analysed 1684 patients with a mean age of 51 years and BMI of 27.2 kg/m2.
The mean DD score was 2.6 (out of 5) with greater DD severity with increasing age (R2 = 0.44). In the fully adjusted model, a 10-year increase in age and a 5 kg/m2 increase in BMI were associated, respectively, with a 0.31-unit [95% CI 0.29,0.34] and 0.04-unit [CI 0.01,0.07] increase in degeneration. Age (OR 1.23 [CI 1.06,1.43]) and BMI (OR 2.60 [CI 2.28,2.96]) were positively associated with SS. For DH, age was a negative predictor (OR 0.70 [CI 0.64,0.76]) but for BMI (OR 1.19 [CI 1.07,1.33]), the association was positive. BMI was the strongest predictor of all three features in the upper lumbar spine.

CONCLUSIONS

While an increase in BMI was associated with only a slight increase in DD, it was a stronger predictor for DH and SS, particularly in the upper lumbar discs, suggesting weight loss could be a useful strategy for helping prevent disorders associated with these pathologies.

Sensitivity of subject-specific upper body musculoskeletal model predictions to mass scaling methods

Accurate predictions of spinal loads in subject-specific musculoskeletal models require precise body segment parameters, including segment mass and center of mass (CoM) locations. Existing upper body models often assume a constant percentage of total body mass to calculate segmental masses, disregarding inter-individual variability and limiting their predictive capacity. This study evaluated the sensitivity of subject-specific upper body musculoskeletal model predictions to body mass scaling methods. The upper body segmental masses and corresponding CoM of six male subjects with varying body mass indices were computed using two mass scaling methods: the constant-percentage-based (CPB) scaling method, commonly used in AnyBody software; and our recently developed body-shape-based (BSB) method. Subsequently, these values were used by a validated musculoskeletal model to predict the muscle and disc forces in upright and flexed postures. The discrepancies between the results of the two scaling methods were compared across subjects and postures. Maximum deviations in thorax masses reached up to 7.5% of total body weight (TBW) in overweight subjects, while maximum CoM location differences of up to 35 mm were observed in normal weight subjects. The root mean squared errors (RMSE) of the CPB results, calculated with the BSB results as baseline, showed that the muscle and shear forces of the two scaling methods were quite similar (<4.5% of TBW). Though, there were small to moderate differences in compressive forces (6.5-16.0% of TBW). Thus, the compressive forces predicted with CPB method should be used with caution, particularly for overweight and obese subjects.

Relationship between body mass index and spinal pathology in community-dwelling older adults

PURPOSE

To clarify the relationship between body mass index (BMI) and spinal pathologies including spinal sagittal balance, back extensor strength (BES), paraspinal muscle mass, prevalent vertebral fracture, disc degeneration, Modic changes, low back pain, and quality of life (QOL) in community-dwelling older adults.

METHODS

This study included 380 participants (age: ≥ 65 years, male/female: 152/228) from the Shiraniwa Study. Multivariate nonlinear regression analysis was used to investigate the relationship between BMI and sagittal vertical axis (SVA), BES, paraspinal muscle mass, visual analog scale (VAS) for low back pain, Oswestry Disability Index (ODI), and EuroQoL-5 Dimension (EQ5D) score after adjusting for sex, age, Hospital Anxiety and Depression Scale score, and Charlson Comorbidity Index. In addition, multiple logistic regression analysis was used to investigate the association between BMI and prevalent vertebral fracture, disc degeneration, and Modic changes.

RESULTS

BMI was significantly correlated with SVA, BES, paraspinal muscle mass, VAS, ODI, and EQ5D score. The increase in BMI was associated with the deterioration of all outcomes, which accelerated when the BMI increased from approximately 22-23 kg/m². Moreover, overweight/obesity was significantly correlated with disc degeneration and Modic changes.

CONCLUSION

Increased BMI is significantly associated with spinal pathologies such as SVA, BES, paraspinal muscle mass, VAS, QOL, disc degeneration, and Modic changes. The findings suggest that measures for controlling overweight and obesity among older adults can play an important role in the prevention and treatment of spinal pathologies.

The 6 degrees-of-freedom range of motion of the L1-S1 vertebrae in young and middle-aged asymptomatic people

STUDY DESIGN

Controlled laboratory study.

OBJECTIVE

To determine the 6 degrees of freedom of lumbar vertebra in vivo during different functional activities in young and middle-aged asymptomatic subjects.

METHODS

A total of 26 asymptomatic subjects (M/F, 15/11; age, 20-55 years) were recruited in this study. They were divided into two groups: young group (number: 14; age: 20-30 years old) and middle-aged group (number: 12; age: 45-55 years old). The lumbar segment of each subject was scanned by computed tomography for the construction of three-dimensional (3D) models of the vertebra from L1 to S1. The lumbar spine was imaged by using a dual fluoroscopic system when the subjects performed different trunk postures. The 3D models of vertebrae were matched to two fluoroscopic images simultaneously in software. The range of motion (ROM) of vertebrae in the young and middle-aged groups was compared by using multiway analysis of variance, respectively.

RESULTS

During the supine to the upright posture, vertebral rotation of the L1-S1 occurred mainly around the mediolateral axis (mean: 3.9 ± 2.9°). Along the mediolateral axis, vertebral translation was significantly lower at L1-2 (7.7 ± 2.4 mm) and L2-3 (8.0 ± 3.5 mm) than at L3-4 (1.6 ± 1.2 mm), L4-5 (3.3 ± 2.6 mm), and L5-S1 (2.6 ± 1.9 mm). At the L4-5 level, the young group had a higher rotational ROM than the middle-aged group around all three axes during left-right bending. Along the anteroposterior axis, the young group had a lower translational ROM at L4-5 than the middle-aged group during left-right bending (4.6 ± 3.3 vs. 7.6 ± 4.8 mm; P < 0.05). At L5-S1, the young group had a lower translational ROM than the middle-aged group during flexion-extension, left-right bending, and left-right torsion.

CONCLUSION

This study explored the lumbar vertebral ROM at L1-S1 during different functional postures in both young and middle-aged volunteers. There were higher coupled translations at L3-4 and L4-5 than at the upper lumbar segments during supine to upright. The vertebral rotation decreased with age. In addition, the older subjects had a higher anteroposterior translation at the L4-5 segment and higher mediolateral translation at the L5-S1 segment than the young group. These data might provide basic data to be compared with spinal pathology.

Does minimally invasive spine surgery improve outcomes in the obese population? A retrospective review of 1442 degenerative lumbar spine surgeries

OBJECTIVE

The effect of obesity on outcomes in minimally invasive surgery (MIS) approaches to posterior lumbar surgery is not well characterized. The authors aimed to determine if there was a difference in operative variables and complication rates in obese patients who underwent MIS versus open approaches in posterior spinal surgery, as well as between obese and nonobese patients undergoing MIS approaches.

METHODS

A retrospective review of all consecutive patients who underwent posterior lumbar surgery from 2013 to 2016 at a single institution was performed. The primary outcome measure was postoperative complications. Secondary outcome measures included estimated blood loss (EBL), operative time, the need for revision, and hospital length of stay (LOS); readmission and disposition were also reviewed. Obese patients who underwent MIS were compared with those who underwent an open approach. Additionally, obese patients who underwent an MIS approach were compared with nonobese patients. Bivariate and multivariate analyses were carried out between the groups.

RESULTS

In total, 423 obese patients (57.0% decompression and 43.0% fusion) underwent posterior lumbar MIS. When compared with 229 obese patients (56.8% decompression and 43.2% fusion) who underwent an open approach, patients in both the obese and nonobese groups who underwent MIS experienced significantly decreased EBL, LOS, operative time, and surgical site infections (SSIs). Of the nonobese patients, 538 (58.4% decompression and 41.6% fusion) underwent MIS procedures. When compared with nonobese patients, obese patients who underwent MIS procedures had significantly increased LOS, EBL, operative time, revision rates, complications, and readmissions in the decompression group. In the fusion group, only LOS and disposition were significantly different.

CONCLUSIONS

Obese patients have poorer outcomes after posterior lumbar MIS when compared with nonobese patients. The use of an MIS technique can be of benefit, as it decreased EBL, operative time, LOS, and SSIs for posterior decompression with or without instrumented fusion in obese patients.

Minimally invasive posterior lumbar surgery in the morbidly obese, obese and non-obese populations: A single institution retrospective review

BACKGROUND

There is a paucity of information regarding outcomes in minimally invasive surgical (MIS) approaches to posterior lumbar surgery in morbidly obese patients. We seek to determine if there are differences in operative variables and early complication rates in morbidly obese patients undergoing MIS posterior lumbar surgery compared to obese and non-obese patients.

METHODS

A single institution retrospective review of patients undergoing MIS posterior lumbar surgery (decompression and/or fusion) between 2013 and 2016 was performed. Morbidly obese patients (BMI ≥ 40) were compared to obese (BMI 30-39.9) and non-obese (BMI < 30) cohorts. Postoperative complication rates and perioperative variables including estimated blood loss, operative time, and outcome measures including length of stay (LOS), in-hospital complications, readmission, and disposition were assessed.

RESULTS

47 morbidly obese, 135 obese and 224 non-obese patients underwent posterior MIS instrumented fusion. 59 morbidly obese, 182 obese and 314 non-obese patients underwent posterior MIS decompression. The morbidly obese group experienced a greater rate of deep vein thrombosis and had an increased hospital LOS (p < 0.05). Morbidly obese patients who underwent MIS decompression experienced increased postoperative complications (p < 0.01), and increased LOS (p < 0.0001) compared to obese and non-obese patients. There were no differences in revision rates, readmissions, and other complications including surgical site infection. Morbid obesity was an independent predictor of overall complications and increased LOS on multivariate analysis.

CONCLUSION

Morbidly obese patients undergoing posterior MIS fusion had a higher rate of complications and increased LOS. While weight loss should be encouraged, complication rates remains acceptably low in morbidly obese patients and MIS posterior lumbar surgery should still be offered.

Spinal segment ranges of motion, movement coordination, and three-dimensional kinematics during occupational activities in normal-weight and obese individuals

Measurements of spinal segment ranges of motion (RoMs), movement coordination, and three-dimensional kinematics during occupational activities have implications in occupational/clinical biomechanics. Due to the large amount of adipose tissues, obese individuals may have different RoMs, lumbopelvic coordination, and kinematics than normal-weight ones. We aimed to measure/compare trunk, lumbar, and pelvis primary RoMs in all anatomical planes/directions, lumbopelvic ratios (lumbar to pelvis rotations at different trunk angles) in all anatomical planes/directions and three-dimensional spine kinematics during twelve symmetric/asymmetric statics load-handling activities in healthy normal-weight and obese individuals. Kinematics/motion data were collected from nine healthy young male normal-weight and nine age/height/sex matched obese individuals via a ten-camera Vicon motion capture system. Obese individuals had significantly smaller (p < 0.05) lumbar flexion (~9° in average) and larger pelvis right lateral bending (~5°) RoMs as well as smaller lumbopelvic ratios (~37%) in lateral bending and axial rotation movements as compared to normal-weight individuals. Moreover, the two groups had generally non-significant different segmental orientations (<20° and in most cases < 10°) in load-handling tasks that depended on the magnitude of load asymmetry angle (p < 0.05). Differences were larger for tasks performed near the floor, away from body, and at larger load asymmetry angles. Biomechanical models simulating pure lateral bending, axial rotation, or tasks involving large load asymmetry may therefore need subject-specific, rather than population-based, motion analysis due to the effects from body weight. In clinical applications, it should be noted that healthy obese individuals may have different RoMs and lumbopelvic rhythms than healthy normal-weight individuals in some anatomical planes/directions.

Mild and Severe Obesity Reduce the Effectiveness of Lumbar Fusions: 1-Year Patient-Reported Outcomes in 8171 Patients

BACKGROUND

Elevated body mass index (BMI) is a well-known risk factor for surgical complications in lumbar surgery. However, its effect on surgical effectiveness independent of surgical complications is unclear.

OBJECTIVE

To determine increasing BMI's effect on functional outcomes following lumbar fusion surgery, independent of surgical complications.

METHODS

We retrospectively analyzed a prospectively built, patient-reported, quality of life registry representing 75 hospital systems. We evaluated 1- to 3-level elective lumbar fusions. Patients who experienced surgical complications were excluded. A stepwise multivariate regression model assessed factors independently associated with 1-yr Oswestry Disability Index (ODI), preop to 1-yr ODI change, and achievement of minimal clinically important difference (MCID).

RESULTS

A total of 8171 patients met inclusion criteria: 2435 with class I obesity (BMI 30-35 kg/m2), 1328 with class II (35-40 kg/m2), and 760 with class III (≥40 kg/m2). Increasing BMI was independently associated with worse 12-mo ODI (t = 8.005, P < .001) and decreased likelihood of achieving MCID (odds ratio [OR] = 0.977, P < .001). One year after surgery, mean ODI, ODI change, and percentage achieving MCID worsened with class I, class II, and class III vs nonobese cohorts (P < .001) in stepwise fashion.

CONCLUSION

Increasing BMI is associated with decreased effectiveness of 1- to 3-level elective lumbar fusion, despite absence of surgical complications. BMI ≥ 30 kg/m2 is, therefore, a risk factor for both surgical complication and reduced benefit from lumbar fusion.

Diet-induced obesity leads to behavioral indicators of pain preceding structural joint damage in wild-type mice

Introduction

Obesity is one of the largest modifiable risk factors for the development of musculoskeletal diseases, including intervertebral disc (IVD) degeneration and back pain. Despite the clinical association, no studies have directly assessed whether diet-induced obesity accelerates IVD degeneration, back pain, or investigated the biological mediators underlying this association. In this study, we examine the effects of chronic consumption of a high-fat or high-fat/high-sugar (western) diet on the IVD, knee joint, and pain-associated outcomes.

Methods

Male C57BL/6N mice were randomized into one of three diet groups (chow control; high-fat; high-fat, high-sugar western diet) at 10 weeks of age and remained on the diet for 12, 24, or 40 weeks. At endpoint, animals were assessed for behavioral indicators of pain, joint tissues were collected for histological and molecular analysis, serum was collected to assess for markers of systemic inflammation, and IBA-1, GFAP, and CGRP were measured in spinal cords by immunohistochemistry.

Results

Animals fed obesogenic (high-fat or western) diets showed behavioral indicators of pain beginning at 12 weeks and persisting up to 40 weeks of diet consumption. Histological indicators of moderate joint degeneration were detected in the IVD and knee following 40 weeks on the experimental diets. Mice fed the obesogenic diets showed synovitis, increased intradiscal expression of inflammatory cytokines and circulating levels of MCP-1 compared to control. Linear regression modeling demonstrated that age and diet were both significant predictors of most pain-related behavioral outcomes, but not histopathological joint degeneration. Synovitis was associated with alterations in spontaneous activity.

Conclusion

Diet-induced obesity accelerates IVD degeneration and knee OA in mice; however, pain-related behaviors precede and are independent of histopathological structural damage. These findings contribute to understanding the source of obesity-related back pain and the contribution of structural IVD degeneration.

Increasing BMI increases lumbar intervertebral disc deformation following a treadmill walking stress test

High body mass index (BMI) and obesity have been implicated as risk factors for lumbar degenerative disc disease and low back pain. Despite this, there is limited in vivo data to quantify how obesity influences the mechanical function of intervertebral discs (IVD) in response to activities of daily living. Recently, our lab has developed methodologies to non-invasively measure in vivo IVD deformation resulting from activities of daily living using magnetic resonance (MR) imaging and solid modeling techniques. This pilot study expands on these methodologies to assess how BMI influences IVD deformation following treadmill walking in eight asymptomatic individuals. Ordinary least squares regression analyses revealed a statistically significant relationship between BMI and compressive deformation (strain (%)) in the L5-S1 IVD (R² = 0.61, p < 0.05). This relationship was weaker in the L3-L4 (R² = 0.28, p > 0.05) and L4-L5 IVDs (R² = 0.28, p > 0.05). Importantly, no relationship between pre-exercise disc height and BMI was identified (p > 0.05). Therefore, the results of this study suggest that BMI may alter the mechanical response of lumbar spine IVDs, particularly at the L5-S1 level. Furthermore, the observed relationship between increased BMI and IVD compressive deformation, in the absence of a detected relationship between pre-exercise disc height and BMI, suggests that changes in IVD mechanical function may be more sensitive to alterations in disc health than static clinical imaging alone. This finding highlights the importance of quantifying disc mechanical function when examining the relationship between BMI and IVD degeneration.

Risk Factors of Intervertebral Disc Pathology-A Point of View Formerly and Today-A Review

Intervertebral disc pathology is a common disorder that can be caused by genetic, mechanical, and behavioral factors; however, it is possible to slow its progression. Although environmental and behavioral factors were previously considered to be the sole causes of intervertebral disc pathologies such as disc herniation, recent studies have shown that genetic factors also play an important role. This review compares the perception of major risk factors from the last and present centuries. It also examines individual genetic and non-genetic factors acting as risk factors, as well as some approaches for preventing intervertebral disc pathologies, and compares available statistics regarding disc herniation.

Muscle-driven and torque-driven centrodes during modeled flexion of individual lumbar spines are disparate

Lumbar spine biomechanics during the forward-bending of the upper body (flexion) are well investigated by both in vivo and in vitro experiments. In both cases, the experimentally observed relative motion of vertebral bodies can be used to calculate the instantaneous center of rotation (ICR). The timely evolution of the ICR, the centrode, is widely utilized for validating computer models and is thought to serve as a criterion for distinguishing healthy and degenerative motion patterns. While in vivo motion can be induced by physiological active structures (muscles), in vitro spinal segments have to be driven by external torque-applying equipment such as spine testers. It is implicitly assumed that muscle-driven and torque-driven centrodes are similar. Here, however, we show that centrodes qualitatively depend on the impetus. Distinction is achieved by introducing confidence regions (ellipses) that comprise centrodes of seven individual multi-body simulation models, performing flexion with and without preload. Muscle-driven centrodes were generally directed superior–anterior and tail-shaped, while torque-driven centrodes were located in a comparably narrow region close to the center of mass of the caudal vertebrae. We thus argue that centrodes resulting from different experimental conditions ought to be compared with caution. Finally, the applicability of our method regarding the analysis of clinical syndromes and the assessment of surgical methods is discussed.

The impact and distinction of 'lipid healthy but obese' and 'lipid abnormal but not obese' phenotypes on lumbar disc degeneration in Chinese

Background

Lipid abnormality and obesity have been proposed to be associated with lumbar disc degeneration, but little is known about the effect of ‘lipid healthy but obese’ (LH-O) and ‘lipid abnormal but not obese’ (LA-NO) phenotypes on lumbar disc degeneration in Chinese. The study aims to determine the impact and distinction of LH-O and LA-NO phenotypes on lumbar disc degeneration in Chinese, and to identify the association of related factors with risk of lumbar disc degeneration.

Methods

A total of 678 individuals were included with lumbar magnetic resonance imaging, serum lipid levels and anthropometric measurements. Obesity was defined on the basis of body mass index or waist to hip ratio (WHR). Pfirrmann score and Weishaupt’s scale were utilized to assess the degree of disc degeneration and facet joint degeneration.

Results

The incidence of the LH-O and LA-NO phenotypes were 11.4% and 18.1%, respectively. LA-NO phenotype demonstrates a high incidence for disc degeneration (P < 0.05), while LH-O phenotype confers a severe disc degeneration grade (P < 0.05). No statistical difference in the percentage of severe facet joint degeneration grade in each group (P > 0.05). Elevated triglycerides and greater WHR may be the risk factors for lumbar disc degeneration in Chinese.

Conclusion

LH-O and LA-NO phenotypes are common with different status of disc degeneration in Chinese. Elevated triglycerides and abdominal obesity appear to play crucial roles in the development of lumbar disc degeneration.

Variations Among Human Lumbar Spine Segments and Their Relationships to In Vitro Biomechanics: A Retrospective Analysis of 281 Motion Segments From 85 Cadaveric Spines

Background

Biomechanical properties of intact spinal motion segments are used to establish baseline values during in vitro studies evaluating spinal surgical techniques and implants. These properties are also used to validate computational models (ie, patient-specific finite element models) of human lumbar spine segments. Our laboratory has performed a large number of in vitro mechanical studies of lumbar spinal segments, using a consistent methodology. This provides extensive biomechanical data for a large number of intact motion segments, along with donor demographic variables, bone mineral density (BMD) measurements, and geometric properties. The objective of this study was to analyze how donor demographics, BMD, and geometric properties of cadaveric lumbar spine segments affect motion segment flexibility, including the range of motion (ROM), lax zone (LZ), and stiff zone (SZ), to help improve our understanding of spinal biomechanics.

Methods

A retrospective study examined the relationships between the biomechanical properties of 281 lumbar motion segments from 85 human cadaveric spines, donor demographic variables (age, sex, weight, height, and body mass index), and specimen measurements (vertebral body height, intervertebral disc height, and BMD).

Results

Statistical correlation and regression analyses showed that the flexibility of a lumbar motion segment is affected by lumbar level, donor age, sex, and weight as well as the intervertebral disc height, vertebral body height, and bone quality. Increased disc height was associated with decreased ROM (axial rotation), decreased LZ (flexion-extension and axial rotation), and increased SZ (flexion-extension and lateral bending) in the male group, but increased ROM (lateral bending) in the female group. Increased vertebral body height correlated with increased LZ (lateral bending) in the female group. Increased BMD correlated with decreased ROM overall.

Conclusions

Biomechanical measurements from flexibility testing of cadaveric lumbar spine segments are significantly correlated with donor demographics and specimen measurements. Many of these correlations are sex-dependent.

Prior bariatric surgery is associated with lower complications, in-hospital mortality, and healthcare utilization after elective spine fusion surgery

BACKGROUND

Grade 3 obesity could potentially increase postoperative complications after spinal fusion surgery. However, the relationship between prior bariatric surgery (BS) and postoperative complications after spinal fusion surgery is not well-established.

SETTING

Inpatient hospital admissions from the Nationwide Inpatient Sample.

METHODS

Patients with a primary procedure of spinal fusion surgery discharged between 2006 and 2014 were identified. In-hospital outcomes included postoperative complications, mortality, cost, and length of stay were compared between patients with prior BS and grade 3 obesity.

RESULTS

A total of 3,132,192 patients who underwent elective spinal fusion surgery were identified. There were 33,936 (1.1%) patients with a diagnosis of prior BS. The prevalence of prior BS increased significantly from .1% in 2006 to 1.5% in 2014. Compared with patients with grade 3 obesity, patients with prior BS were younger, more likely to be female, had less co-morbidities, and higher proportion of cervical surgery. Multivariable analysis indicated that patients with prior BS had lower risk of overall complications (odds ratio [OR]: .44; 95% confidence interval [CI]: .38-.49), neurologic (OR: .55; 95%CI: .35-.84), respiratory (OR: .30; 95%CI: .23-.37), cardiac (OR: .38; 95%CI: .24-.60), gastrointestinal (OR: .61; 95%CI: .44-.84), urinary and renal (OR: .34; 95%CI: .26-.44), venous thromboembolism (OR: .35; 95%CI: .19-.63), wound-related complications (OR: .67; 95%CI: .53-.85), and in-hospital mortality (OR: .12; 95%CI: .02-.88). Prior BS was also related to 13% shorter length of stay and 2% lower cost.

CONCLUSIONS

Among patients undergoing spinal fusion surgery, prior BS is associated with lower complications, in-hospital mortality, and healthcare utilization. BS might mitigate risk of worse outcomes associated with grade 3 obesity after spine fusion surgery.

Effect of Obesity on the Development, Management, and Outcomes of Spinal Disorders

Obesity is a major public health issue in the United States, and rates of obesity continue to increase across the population. The association of obesity with degenerative spinal pathology underlies the observation that a substantial number of patients undergoing spine surgery are either overweight or obese. Obesity is a notable independent risk factor for both surgical and medical complications in the perioperative period and an important consideration in preoperative planning, intraoperative strategies, and postoperative management. Despite these increased risks, surgery in obese patients for a variety of degenerative conditions results in improvement in outcomes. Although obese patients may undergo gains that are absolutely lower than their nonobese counterparts, they still experience a positive treatment effect with surgery appropriate for their condition. An evidence-based approach to both preoperative and perioperative management of patients with obesity is not well established. The purpose of this article is to review the effect of obesity on the development, management, and outcomes of patients with spinal disorders and to provide data that may guide an evidence-based approach to care in this expanding patient population.

Effect of Obesity on Radiographic Alignment and Short-Term Complications After Surgical Treatment of Adult Cervical Deformity

OBJECTIVE

We investigated the 30-day complication incidence and 1-year radiographic correction in obese patients undergoing surgical treatment of cervical deformity.

METHODS

The patients were stratified according to World Health Organization's definition for obesity: obese, patients with a body mass index of ≥30 kg/m²; and nonobese, patients with a body mass index of <30 kg/m². The patients had undergone surgery for the treatment of cervical deformity. The patient baseline demographic, comorbidity, and radiographic data were compared between the 2 groups at baseline and 1 year postoperatively. The 30-day complication incidence was stratified according to complication severity (any, major, or minor), and type (cardiopulmonary, dysphagia, infection, neurological, and operative). Binary logistic regression models were used to assess the effect of obesity on developing those complications, with adjustment for patient age and levels fused.

RESULTS

A total of 124 patients were included, 53 obese and 71 nonobese patients. The 2 groups had a similar T1 slope minus cervical lordosis (obese, 37.2° vs. nonobese, 36.9°; P = 0.932) and a similar C2-C7 (-5.9° vs. -7.3°; P = 0.718) and C2-C7 (50.1 mm vs. 44.1 mm; P = 0.184) sagittal vertical axis. At the 1-year follow-up examination, the T1 pelvic angle (1.0° vs. -3.1°; P = 0.021) and C2-S1 sagittal vertical axis (-5.9 mm vs. -35.0 mm; P = 0.036) were different, and the T1 spinopelvic inclination (-1.0° vs. -2.9°; P = 0.123) was similar. The obese patients had a greater risk of overall short-term complications (odds ratio, 2.5; 95% confidence interval, 1.1-6.1) and infectious complications (odds ratio, 5.0; 95% confidence interval, 1.0-25.6).

CONCLUSIONS

Obese patients had a 5 times greater odds of developing infections after surgery for adult cervical deformity. Obese patients also showed significantly greater pelvic anteversion after cervical correction.

Lumbar Microdiscectomy in Obese Patients: A Multicenter Observational Study

OBJECTIVE

To evaluate the association between obesity and outcomes after microdiscectomy for lumbar disc herniation.

METHODS

The primary outcome measure was change in Oswestry Disability Index (ODI) at 1 year after surgery. Obesity was defined as body mass index (BMI) ≥30. Prospective data were retrieved from the Norwegian Registry for Spine Surgery.

RESULTS

We enrolled 4932 patients, 4018 nonobese and 914 obese. For patients with complete 1-year follow-up (n = 3381) the mean improvement in ODI was 31.2 points (95% confidence interval 30.4-31.9, P < 0.001). Improvement in ODI was 31.4 points in nonobese and 30.1 points in obese patients (P = 0.182). Obese and nonobese patients were as likely to achieve a minimal clinically important difference (84.2 vs. 82.7%, P = 0.336) in ODI (≥10 points improvement). Obesity was identified as a negative predictor for ODI improvement in a multiple regression analysis (BMI 30-34.99; P < 0.001, BMI ≥35; P = 0.029). Obese and nonobese patients experienced similar improvement in Euro-Qol-5 scores (0.48 vs. 0.49 points, P = 0.441) as well as back pain (3.7 vs. 3.5 points, P = 0.167) and leg pain (4.7 vs. 4.8 points, P = 0.654), as measured by the Numeric Rating Scale. Duration of surgery was shorter for nonobese patients (55.7 vs. 65.3 minutes, P ≤ 0.001). Nonobese patients experienced fewer complications compared with obese patients (6.1% vs. 8.3%, P = 0.017). Obese patients had slightly longer hospital stays (2.0 vs. 1.8 days, P = 0.004).

CONCLUSIONS

Although they had more minor complications, obese individuals experienced improvement after lumbar microdiscectomy for lumbar disc herniation similar to that of nonobese individuals.

The impact of obesity on compensatory mechanisms in response to progressive sagittal malalignment

BACKGROUND CONTEXT

Obesity's impact on standing sagittal alignment remains poorly understood, especially with respect to the role of the lower limbs. Given energetic expenditure in standing, a complete understanding of compensation in obese patients with sagittal malalignment remains relevant.

PURPOSE

This study compares obese and non-obese patients with progressive sagittal malalignment for differences in recruitment of pelvic and lower-limb mechanisms.

STUDY DESIGN/SETTING

Single-center retrospective review.

PATIENT SAMPLE

A total of 554 patients (277 obese, 277 non-obese) were identified for analysis.

OUTCOME MEASURES

Upper body alignment parameters: sagittal vertical axis (SVA) and T1 spinopelvic inclination (T1SPi). Compensatory lower-limb mechanisms: pelvic translation (pelvic shift [PS]), knee (KA) and ankle (AA) flexion, hip extension (sacrofemoral angle [SFA]), and global sagittal angle (GSA).

METHODS

Inclusion criteria were patients ≥18 years who underwent full-body stereographic x-rays. Included patients were categorized as non-obese (N-Ob: body mass index [BMI]<30 kg/m²) or obese (Ob: BMI≥30 kg/m²). To control for potential confounders, groups were propensity score matched by age, gender, and baseline pelvic incidence (PI), and subsequently categorized by increasing spinopelvic (pelvic incidence minus lumbar lordosis [PI-LL]) mismatch: <10°, 10°-20°, >20°. Independent t tests and linear regression models compared sagittal (SVA, T1SPi) and lower limb (PS, KA, AA, SFA, GSA) parameters between obesity cohorts.

RESULTS

A total of 554 patients (277 Ob, 277 N-Ob) were included for analysis and were stratified to the following mismatch categories: <10°: n=367; 10°-20°: n=91; >20°: n=96. Obese patients had higher SVA, KA, PS, and GSA than N-Ob patients (p<.001 all). Low PI-LL mismatch Ob patients had greater SVA with lower SFA (142.22° vs. 156.66°, p=.032), higher KA (5.22° vs. 2.93°, p=.004), and higher PS (4.91 vs. -5.20 mm, p<.001) than N-Ob patients. With moderate PI-LL mismatch, Ob patients similarly demonstrated greater SVA, KA, and PS, combined with significantly lower PT (23.69° vs. 27.14°, p=.012). Obese patients of highest (>20°) PI-LL mismatch showed greatest forward malalignment (SVA, T1SPi) with significantly greater PS, and a concomitantly high GSA (12.86° vs. 9.67°, p=.005). Regression analysis for lower-limb compensation revealed that increasing BMI and PI-LL predicted KA (r²=0.234) and GSA (r²=0.563).

CONCLUSIONS

With progressive sagittal malalignment, obese patients differentially recruit lower extremity compensatory mechanisms, whereas non-obese patients preferentially recruit pelvic mechanisms. The ability to compensate for progressive sagittal malalignment with the pelvic retroversion is limited by obesity.

Associations between Obesity and Spinal Diseases: A Medical Expenditure Panel Study Analysis

Background: The link between body weight status and spinal diseases has been suggested by a number of cross-sectional and cohort studies with a limited range of patient populations. No population-representative samples have been used to examine the link between obesity and spinal diseases. The present study is based on a nationally representative sample drawn from the Medical Expenditure Panel Survey. Methods: Using the cross-sectional sample of the 2014 Medical Expenditure Panel Study, we built four weighted logistic regression analyses of the associations between body weight status and the following four spinal diseases: low back pain, spondylosis, other cervical disorders and intervertebral disc disorder (IDD). Each respondent's body weight status was used as the key independent variable with three categories: normal/underweight, overweight, and obese. We controlled for marital status, gender, age, smoking status, household income, health insurance coverage, educational attainment and the use of health services for other major categories of diseases. Results: A total sample of 23,048 respondents was used in our analysis. Overweight and obese respondents, as compared to normal/underweight respondents, were more likely to develop lower back problems (Overweight: logged odds = 0.218, p < 0.01; Obese: logged odds = 0.395, p < 0.001) and IDD (Overweight: logged odds = 0.441, p < 0.05; Obese: logged odds = 0.528, p < 0.001). The associations between bodyweight status and spondylitis were statistically insignificant (Overweight: logged odds = 0.281, p = 0.442; Obese: logged odds = 0.680, p = 0.104). The associations between body weight status and other cervical disorders (Overweight: logged odds = -0.116, p = 0.304; Obese: logged odds = -0.160, p = 0.865) were statistically insignificant. Conclusions: As the first study using a national sample to study bodyweight and spinal diseases, our paper supports the hypothesis that obesity adds to the burden of low back pain and IDD. Longitudinal and interventional studies are needed to understand the specific mechanisms behind these positive associations.

Comparison of outcomes between minimally invasive transforaminal lumbar interbody fusion and traditional posterior lumbar intervertebral fusion in obese patients with lumbar disk prolapse

Objective

The aim of this study was to compare the curative effect between minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) and the posterior lumbar interbody fusion (PLIF) in obese patients with lumbar disk prolapse.

Patients and methods

In this study, 72 patients who underwent lumbar disk prolapse therapy in the Third Hospital of Hebei Medical University between March 2011 and 2015 were retrospectively analyzed and were divided into two groups, MIS-TLIF group (n=35) and PLIF group (n=37), according to different surgical procedures. Several clinical parameters were compared between these two groups.

Results

Compared with PLIF, MIS-TLIF was associated with longer operative time, less blood loss, less postoperative drainage and shorter postoperative time in bed; moreover, patients in the MIS-TLIF group had lower levels of serum creatine kinase on 1, 3 and 5 postoperative days. At the 3- and 6-month follow-up, Visual Analog Scale (VAS) scores of low back pain of patients in the MIS-TLIF group were significantly reduced and Japanese Orthopaedic Association (JOA) scores were increased, whereas the Oswestry Disability Index (ODI) showed no significant difference between the two groups.

Conclusion

Obese patients can achieve good efficacy with MIS-TLIF or PLIF treatment, but MIS-TLIF surgery showed longer operative time, fewer traumas and bleeding volume, less incidence of short-term pain, low complication rate and faster postoperative recovery.

Analysis of the clinical effects of transforaminal endoscopic discectomy on lumbar disk herniation combined with common peroneal nerve paralysis: a 2-year follow-up retrospective study on 32 patients

Background

Very few studies have discussed transforaminal endoscopic discectomy (TED) in the treatment of common peroneal nerve paralysis induced by lumbar disk herniation (LDH). This study aimed to evaluate the efficacy of TED in the treatment of LDH combined with common peroneal nerve paralysis.

Materials and methods

The clinical and follow-up data of 32 patients with common peroneal nerve paralysis induced by LDH undergoing TED from March 2011 to April 2014 were retrospectively analyzed in this study. Follow-up was conducted immediately after the surgery, as well as 3, 12, and 24 months postoperatively. The parameters (including muscle strength recovery of the anterior tibial muscle, leg pain visual analog scale score, neurological function Japanese Orthopaedic Association [JOA] score, MacNab scores in the last follow-up, and the intraoperative and postoperative complications) were recorded.

Results

Three patients (9.4%) had the anterior tibial muscle strength recovered to ≥ grade 4 immediately after the surgery. The anterior tibial muscle strength of patients recovered to basically stable form in the 6-month postoperative follow-up and that in the last follow-up were as follows: one case of grade 1, one case of grade 2, 28 cases of grade 4, and two cases of grade 5. The visual analog scale scores of leg pain were significantly reduced immediately after the surgery and also on 3, 12, and 24 months compared with preoperative period (all P<0.05). The postoperative JOA scores in the last follow-up were significantly higher than the preoperative JOA scores (P<0.05), and there were nine excellent cases (28.2%), 21 good cases (65.6%), one fair case (3.1%) and one poor case (3.1%) in the last follow-up, with an overall excellent and good rate of 93.8%.

Conclusion

TED, which can offer sufficient decompression of the nerve root, has excellent overall clinical effects in treating common peroneal nerve paralysis induced by LDH.