Cut-off Value for Body Mass Index in Predicting Surgical Success in Patients with Lumbar Spinal Canal Stenosis

Impact of body mass index on outcomes after lumbar spine surgery

The impact of body mass index (BMI) on outcomes after lumbar spine surgery is currently unknown. Previous studies have reported conflicting evidence for patients with high BMI, while little research has been conducted on outcomes for underweight patients. This study aims to examine the impact of BMI on outcomes after lumbar spine surgery. This prospective cohort study enrolled 5622 patients; of which, 194, 5027, and 401 were in the low (< 18.5 kg/m²), normal (18.5-30), and high (≥ 30) BMI groups, respectively. Pain was assessed via the numerical pain rating scale (NPRS) for the lower back, buttock, leg, and plantar area. Quality of life was assessed via the EuroQol 5 Dimension (EQ-5D) and Oswestry Disability Index (ODI). Inverse probability weighting with propensity scores was used to adjust patient demographics and clinical characteristics between the groups. After adjustment, the 1-year postoperative scores differed significantly between groups in terms of leg pain. The proportion of patients who achieved a 50% decrease in postoperative NPRS score for leg pain was also significantly different. Obese patients reported less improvement in leg pain after lumbar spine surgery. The outcomes of patients with low BMI were not inferior to those of patients with normal BMI.

An Ensemble Learning Approach to Improving Prediction of Case Duration for Spine Surgery: Algorithm Development and Validation

BACKGROUND

Estimating surgical case duration accurately is an important operating room efficiency metric. Current predictive techniques in spine surgery include less sophisticated approaches such as classical multivariable statistical models. Machine learning approaches have been used to predict outcomes such as length of stay and time returning to normal work, but have not been focused on case duration.

OBJECTIVE

The primary objective of this 4-year, single-academic-center, retrospective study was to use an ensemble learning approach that may improve the accuracy of scheduled case duration for spine surgery. The primary outcome measure was case duration.

METHODS

We compared machine learning models using surgical and patient features to our institutional method, which used historic averages and surgeon adjustments as needed. We implemented multivariable linear regression, random forest, bagging, and XGBoost (Extreme Gradient Boosting) and calculated the average R², root-mean-square error (RMSE), explained variance, and mean absolute error (MAE) using k-fold cross-validation. We then used the SHAP (Shapley Additive Explanations) explainer model to determine feature importance.

RESULTS

A total of 3189 patients who underwent spine surgery were included. The institution's current method of predicting case times has a very poor coefficient of determination with actual times (R²=0.213). On k-fold cross-validation, the linear regression model had an explained variance score of 0.345, an R² of 0.34, an RMSE of 162.84 minutes, and an MAE of 127.22 minutes. Among all models, the XGBoost regressor performed the best with an explained variance score of 0.778, an R² of 0.770, an RMSE of 92.95 minutes, and an MAE of 44.31 minutes. Based on SHAP analysis of the XGBoost regression, body mass index, spinal fusions, surgical procedure, and number of spine levels involved were the features with the most impact on the model.

CONCLUSIONS

Using ensemble learning-based predictive models, specifically XGBoost regression, can improve the accuracy of the estimation of spine surgery times.

The Effects of Body Composition Characteristics on the Functional Disability in Patients with Degenerative Lumbar Spinal Stenosis

Several research studies suggest that obese patients are at a higher risk of developing lumbar spinal disorder, including degenerative lumbar spinal stenosis (LSS), compared to normal-weight individuals. However, there are few investigations of how obesity affects functional disability in activities of daily living (ADL) in patients who were diagnosed with LSS. This prospective observational study aimed to determine if an association exists between body composition parameters, such as body fat and skeletal muscle, and functional disability in ADL of LSS patients. In the results of the current study, there were significant differences in percent body fat between the mild/moderate and severe disability groups. However, there were no differences in skeletal muscle mass or index between the two groups. Furthermore, we found a positive linear relationship between percent body fat and functional disability in male sex. This study suggests that increased percent body fat predicts potential severe functional disability in ADL in LSS patients. Body composition analysis may provide useful information for predicting the disease severity of various lumbar spinal disorders in clinical practice.

A comparison study on patient-reported outcome between obese and non-obese patients with central lumbar spinal stenosis undergoing surgical decompression: 14,984 patients in the National Swedish Quality Registry for Spine Surgery

BACKGROUND AND PURPOSE

Obesity has been associated with inferior outcomes after laminectomy due to central lumbar spinal stenosis (CLSS); we evaluated whether this occurs in surgery on national bases.

PATIENTS AND METHODS

We retrieved pre- and 1-year postoperative data from the National Swedish Quality Registry for Spine Surgery regarding patients aged ≥ 50 with laminectomy due to CLSS in 2005-2018. 4,069 patients had normal weight, 7,044 were overweight, 3,377 had class I obesity, 577 class II obesity, and 94 class III obesity ("morbid obesity"). Patient-reported outcome included satisfaction after 1 year, leg pain (Numerical Rating Scale [NRS], rating 0-10), disability (Oswestry Disability Index [ODI], rating 0-100). Complications were also retrieved.

RESULTS

1-year postoperatively, 69% of patient of normal weight, 67% who were overweight, and 62% with obesity (classes I-III aggregated) were satisfied (p < 0.001) and 62%, 60%, and 57% in obese groups I-III, respectively (p = 0.7). NRS leg pain improved in normal-weight patients by 3.5 (95% CI 3.4-3.6), overweight by 3.2 (CI 3.1-3.2), and obese by 2.6 (CI 2.5-2.7), and 2.8 (CI 2.7-2.9), 2.5 (CI 2.2-2.7), and 2.6 (CI 2.0-3.2) in obese classes I-III, respectively. ODI improved in normal weight by 19 (CI 19-20), overweight by 17 (CI 17-18), and obese by 14 (CI 13-15), and 16 (CI 15-17), 14 (CI 13-16), 14 (CI 11-18) in obese classes I-III, respectively. 8.1% of normal weight, 7.0% of overweight, and 8.1% of obese patients suffered complications (p = 0.04) and 8.1%, 7.0%, and 17% among obese classes I-III, respectively (p < 0.01).

CONCLUSION

Most obese patients are satisfied after laminectomy due to CLSS, even if satisfaction rate is inferior compared with normal-weight patients. The morbidly obese have more complications than patients with lower BMI.

Application of enhanced recovery after surgery care protocol in the perioperative care of patients undergoing lumbar fusion and internal fixation

Background

To explore the effects and deficiencies of the enhanced recovery after surgery (ERAS) care protocol on patients undergoing lumbar fusion and internal fixation in perioperative care.

Methods

A total of 166 patients with lumbar fusion and internal fixation were collected and divided into two groups, among which 86 patients received ERAS care protocol were attributed into ERAS group, while the other 80 patients received traditional perioperative care protocol were assigned to control group. Then, the degree of pain, self-care ability and the degree of recovery were assessed using the visual analogue scale (VAS), Barthel index (BI) rating scale and the Sino-version Oswestry Disability Index (ODI) questionnaire, respectively. Moreover, further analysis was performed based on patients’ different age, gender, body mass index (BMI) and education of patients in ERAS group.

Results

The hospitalization time and the incidence of complication in the ERAS group were obviously lower than those in control group (both, P < 0.05). There was no significant difference in hospitalization expenses between the two groups (P > 0.05). The BI score of the ERAS group was higher than that of the control group (P < 0.05), and the percentage of ODI score in ERAS group was significantly downregulated in comparison with that in control group (P < 0.05). Intra-group analysis in ERAS showed that, compared with older patients, younger patients had higher BI scores (P < 0.05) and lower ODI scores (P < 0.05); meanwhile, overweight patients had lower BI scores (P < 0.05), and the ODI score decreased with the increase in education level of the patients.

Conclusions

ERAS care protocol can significantly shorten the hospitalization time and reduce the occurrence of postoperative complications of patients, significantly enhance the self-care ability of patients after discharge and promote the rapid recovery of patients after surgery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03099-0.

Physical Predictors of Favorable Postoperative Outcomes in Patients Undergoing Laminectomy or Laminotomy for Central Lumbar Spinal Stenosis: Secondary Analysis of a Randomized Controlled Trial

Study Design

Secondary analysis of a randomized controlled trial.

Objective

To identify preoperative physical variables associated with favorable postoperative outcome in individuals undergoing laminectomy or laminotomy for degenerative central lumbar spinal stenosis.

Summary of Background Data

Clinical or condition specific variables have most commonly been studied as predictors of postoperative outcome in lumbar spinal stenosis. If associated to favorable postoperative outcome, modifiable physical variables would inform prehabilitation interventions for patients with degenerative central lumbar spinal stenosis.

Methods

Patients awaiting surgery for central lumbar spinal stenosis were recruited to participate in a randomized controlled trial. Following baseline data collection of demographics, clinical portrait and physical testing, participants were randomized to either 6-week active prehabilitation program or hospital standard care. Complete baseline and postoperative data were obtained from 58 participants which were included in the present analysis. Favorable postoperative outcome was determined based on two outcome measures. Favorable outcome was defined as a decrease of ≥30% on the Numerical Rating Scale for leg pain intensity and a decrease of ≥30% on the Oswestry Disability Index for low back disability. Baseline physical variables were used to conduct binary logistic regression.

Results

Sixty percent of participants were determined as having a favorable postoperative outcome. None of the included physical variables were found to be predictors of a favorable postoperative outcome based on leg pain intensity and low back pain-associated disability [trunk flexors muscle strength (OR = 0.73; 95%CI (0.02–27.12)] lumbar extensors muscle endurance [OR= 1.09; 95%CI (0.95–1.24)] total ambulation time [OR = 1.00 95%CI (0.99–1.01)] lumbar active range of motion in extension [OR = 1.08; 95%CI (0.95–1.23)] and knee extensors muscle strength [OR=1.02; 95%CI (0.98–1.06)].

Conclusion

Results show that none of the investigated variables, all related to low back and lower limbs physical capacity, were predictors of postoperative recovery. Further testing in larger cohort is needed to assess the full potential of physical outcome measures as predictors of postoperative recovery.

Effect of BMI on the clinical outcome following microsurgical decompression in over-the-top technique: bi-centric study with an analysis of 744 patients

PURPOSE

Decompression is one of the most common interventions in spinal surgery. Obesity has become an increasing issue in surgical patients. Therefore, the aim of this study was to analyze the clinical outcome following lumbar microsurgical decompression in correlation with the patient's body mass index (BMI).

MATERIALS AND METHODS

A toal of 744 patients with spinal claudication that were seen at two specialized spine centers were included in this study. All patients underwent a bilateral microsurgical decompression in over-the-top technique. Patients were allocated in 4 groups based in their BMI category: 18.5-24.9 (n = 204), 25.0-29.9 (n = 318), 30.0-34.9 (n = 164) and ≥ 35 (n = 58). Clinical outcome data were recorded at baseline as well as 3, 12 and 24 months thereafter within a prospective study framework. The minimum follow-up was 12 months. For statistical analysis, data were adjusted for age, length of surgery and ASA and were analyzed by generalized linear gamma-based models.

RESULTS

Postoperative changes in all outcome parameters were clearly dependent on BMI. Patients with higher BMI were characterized by inferior baseline values for VAS Back (p < 0.05). Over the follow-up period, the groups with BMI 30-34.9 and BMI ≥ 35 benefitted significantly less from the surgery than the two slimmer groups (p < 0.05).

CONCLUSION

The data obtained from this large, homogenous cohort demonstrate that the quality of life improved substantially in all patients that were treated microsurgically for spinal stenosis. However, a BMI ≥ 30 may be considered as a negative predictor for a significantly inferior clinical outcome.

Predicting recovery after lumbar spinal stenosis surgery: A protocol for a historical cohort study using data from the Canadian Spine Outcomes Research Network (CSORN)

Background: Symptomatic lumbar spinal stenosis (SLSS) is a condition in which narrowing of the spinal canal results in entrapment and compression of neurovascular structures. Decompressive surgery, with or without spinal fusion, is recommended for those with severe symptoms for whom conservative management has failed. However, significant persistent pain, functional limitations, and narcotic use can affect up to one third of patients postsurgery. Aims: The aim of this study will be to identify predictors of outcomes 1-year post SLSS surgery with a focus on modifiable predictors. Methods: The Canadian Spine Outcomes Research Network (CSORN) is a large database of prospectively collected data on pre- and postsurgical outcomes among surgical patients. We include participants with a primary diagnosis of SLSS undergoing their first spine surgery. Outcomes are measured at 12 months after surgery and include back and leg pain, disability (Oswestry Disability Index, ODI), walking capacity (ODI item 4), health-related quality of life, and an overall recovery composite outcome (clinically important changes in pain, disability, and quality of life). Predictors include demographics (education level, work status, marital status, age, sex, body mass index), physical activity level, smoking status, previous conservative treatments, medication intake, depression, patient expectations, and other comorbidities. A multivariate partial least squares model is used to identify predictors of outcomes. Conclusion: Study results will inform targeted SLSS interventions, either for the selection of best candidates for surgery or the identification of targets for presurgical rehabilitation programs.

Long-term impact of obesity on patient-reported outcomes and patient satisfaction after lumbar spine surgery: an observational study

OBJECTIVE

Obese body habitus is a challenging issue to address in lumbar spine surgery. There is a lack of consensus on the long-term influence of BMI on patient-reported outcomes and satisfaction. This study aimed to examine the differences in patient-reported outcomes over the course of 12 and 24 months among BMI classifications of patients who underwent lumbar surgery.

METHODS

A search was performed using the Quality Outcomes Database (QOD) Spine Registry from 2012 to 2018 to identify patients who underwent lumbar surgery and had either a 12- or 24-month follow-up. Patients were categorized based on their BMI as normal weight (≤ 25 kg/m2), overweight (25-30 kg/m2), obese (30-40 kg/m2), and morbidly obese (> 40 kg/m2). Outcomes included the Oswestry Disability Index (ODI) and the visual analog scale (VAS) for back pain (BP) and leg pain (LP), and patient satisfaction was measured at 12 and 24 months postoperatively.

RESULTS

A total of 31,765 patients were included. At both the 12- and 24-month follow-ups, those who were obese and morbidly obese had worse ODI, VAS-BP, and VAS-LP scores (all p < 0.01) and more frequently rated their satisfaction as "I am the same or worse than before treatment" (all p < 0.01) compared with those who were normal weight. Receiver operating characteristic curve analysis revealed that the BMI cutoffs for predicting worsening disability and surgery dissatisfaction were 30.1 kg/m2 and 29.9 kg/m2 for the 12- and 24-month follow-ups, respectively.

CONCLUSIONS

Higher BMI was associated with poorer patient-reported outcomes and satisfaction at both the 12- and 24-month follow-ups. BMI of 30 kg/m2 is the cutoff for predicting worse patient outcomes after lumbar surgery.

Obesity negatively affects cost efficiency and outcomes following adult spinal deformity surgery

BACKGROUND CONTEXT

Obesity has risen to epidemic proportions within the United States. As the rates of obesity have increased, so has its prevalence among patients undergoing adult spinal deformity (ASD) surgery. The effect of obesity on the cost efficiency of corrective procedures for ASD has not been effectively evaluated.

PURPOSE

To investigate differences in cost efficiency of ASD surgery for patients stratified by body mass index (BMI).

STUDY DESIGN/SETTING

Retrospective review of a single-center ASD database.

PATIENT SAMPLE

Five hundred five ASD patients.

OUTCOME MEASURES

Complications, revisions, costs, EuroQol-5D (EQ5D), quality-adjusted life years (QALYs), cost per QALY.

METHODS

ASD patients (scoliosis≥20°, SVA≥5 cm, PT≥25°, or TK ≥60°) ≥18, undergoing ≥4 level fusions were included. Patients were stratified into NIH-defined obesity groups based on their preoperative BMI: underweight 18.5< (U), normal 18.5 to 24.9 (N), overweight 25.0 to 29.9 (O), obese I 30.0 to 34.9 (OI), obese II 35.0 to 39.9 (OII), and obesity class III 40.0+ (OIII). Total surgery costs for each ASD obesity group were calculated. Costs were calculated using the PearlDiver database, which reflects both private insurance and Medicare reimbursement claims. Overall complications and major complications were assessed according to CMS definitions. QALYs and cost per QALY for obesity groups were calculated using an annual 3% discount up to life expectancy (78.7 years).

RESULTS

In all, 505 patients met inclusion criteria. Baseline demographics and surgical details were: age 60.8±14.8, 67.6% female, BMI 28.8±7.30, 81.0% posterior approach, 18% combined approach, 10.1±4.2 levels fused, op time 441.2±146.1 minutes, EBL 1903.8±1594.7 cc, and LOS 8.7±10.7 days. There were 17 U, 154 N patients, 151 O patients, 100 OI, 51 OII, and 32 OIII patients. Revision rates by obesity group were: 0% U, 3% N patients, 3% O patients, 5% OI, 4% OII, and 6% for OIII patients. The total surgery costs by obesity group were: $48,757.86 U, $49,688.52 N, $47,219.93 O, $50,467.66 OI, $51,189.47 OII, and $53,855.79 OIII. In an analysis of patients with baseline and 1 Y EQ5D follow-up, the cost per QALY by obesity group was: $153,737.78 U, $229,222.37 N, $290,361.68 O, $493,588.47 OI, $327,876.21 OII, and $171,680.00 OIII. If that benefit was sustained to life expectancy, the cost per QALY was $8,588.70 U, $12,805.72 N, $16,221.32 O, $27,574.77 OI, $18,317.11 OII, and $9,591.06 for OIII.

CONCLUSIONS

Among adult spinal deformity patients, those with BMIs in the obesity I, obesity II, or obesity class III range had more expensive total surgery costs. When assessing 1 year cost per QALY, obese patients had costs 32% higher than nonobese patients ($224,440.61 vs. $331,048.23). Further research is warranted on the utility of optimizing modifiable preoperative health factors for patients undergoing corrective adult spinal deformity surgery.