Obesity and Spine Surgery: A Qualitative Review About Outcomes and Complications. Is It Time for New Perspectives on Future Researches?

A retrospective analysis of perioperative complications of lateral approach lumbar interbody fusion in patients with prior abdominal surgery or a history of colonic inflammatory disease

BACKGROUND CONTEXT

Lateral approaches for lumbar interbody fusion (LIF) allow for access to the lumbar spine and disc space by passing through a retroperitoneal corridor either pre- or trans-psoas. A contraindication for this approach is the presence of retroperitoneal scarring that may occur from prior surgical intervention in the retroperitoneal space or from inflammatory conditions with fibrotic changes and pose challenges for the mobilization and visualization needed in this approach. However, there is a paucity of evidence on the prevalence of surgical complications following lateral fusion surgery in patients with a history of abdominal surgery.

PURPOSE

The primary aim of this study is to describe the association between surgical complications following lateral interbody fusion surgery and prior abdominal surgical.

STUDY DESIGN

Retrospective study.

PATIENT SAMPLE

Patients over the age of 18 who underwent lateral lumbar interbody fusion at a large, tertiary care center between 2011 and 2019 were included in the study.

OUTCOME MEASURES

The primary outcome included medical, surgical, and thigh-related complications either in the intraoperative or 90-day postoperative periods. Additional outcome metrics included readmission rates, length of stay, and operative duration.

METHODS

The electronic health records of 250 patients were reviewed for demographic information, surgical data, complications, and readmission following surgery. The association of patient and surgical factors to complication rate was analyzed using multivariable logistic regression. Statistical analysis was performed using R statistical software (R, Vienna, Austria).

RESULTS

Of 250 lateral interbody fusion patients, 62.8% had a prior abdominal surgery and 13.8% had a history of colonic disease. The most common perioperative complication was transient thigh or groin pain/sensory changes (n=62, 24.8%). A multivariable logistic regression considering prior abdominal surgery, age, BMI, history of colonic disease, multilevel surgery, and the approach relative to psoas found no significant association between surgical complication rates and colonic disease (OR 0.40, 95% CI 0.02-2.22) or a history of prior abdominal surgeries (OR 0.56, 95% CI 0.20-1.55). Further, the invasiveness of prior abdominal surgeries showed no association with overall spine complication rate, lateral-specific complications, or readmission rates (p>.05).

CONCLUSION

Though retroperitoneal scarring is an important consideration for lateral approaches to the lumbar spine, this study found no association between lateral lumbar approach complication rates and prior abdominal surgery. Further study is needed to determine the impact of inflammatory colonic disease on lateral approach spine surgery.

Obesity Does Not Negatively Affect Patient-perceived Outcomes After Cervical Disc Replacement for Disc Herniation

STUDY DESIGN

Retrospective review.

OBJECTIVE

To assess the impact of Body Mass Index (BMI) on patient-reported outcome measures (PROMs) after cervical disc replacement (CDR).

BACKGROUND

BMI may affect PROMs after spine surgery.

METHODS

Primary CDR recipients for herniated disc(s) with BMI <40 were retrospectively selected from a single-surgeon registry. Cohorts were divided into non-obese (BMI <30) and obese (BMI ≥30). Intercohort in-hospital complication rates were compared through independent samples t tests. Pre/postoperative PROMs were compared between cohorts through multivariable regression accounting for demographic differences. Final follow-up dates between patients averaged 11.8 ± 9.3 months. PROMs assessed included Patient-reported Outcomes Measurement Information System-Physical Function, Neck Disability Index, Visual Analog Scale-Neck, Visual Analog Scale-Arm, and the 9-item Patient Health Questionnaire. Improvements in PROMs were evaluated and compared at each follow-up within cohorts through paired t tests. The magnitude of improvement in PROMs from preoperative baseline at 6-week follow-up (∆PROM-6W) and final follow-up (∆PROM-FF) along with achievement rates of minimum clinically important differences were compared between cohorts through multivariable regression accounting for demographic differences.

RESULTS

Of 153 patients, 53 patients were noted as obese. Demographic differences included age, prevalence of hypertension and diabetes, and comorbidity burden scores ( P ≤ 0.011, all). No significant variations in in-hospital complications were found. The non-obese cohort demonstrated improvements in all PROMs at 6 weeks and final follow-up periods ( P ≤ 0.005, all). The obese cohort demonstrated improvements in all postoperative PROMs besides 9-item Patient Health Questionnaire at 6 weeks ( P ≤ 0.015, all). After accounting for age and comorbidity variations, there were no significant intercohort differences in raw PROM scores, ∆PROM-6W, ∆PROM-FF, or minimum clinically important difference achievement rates.

CONCLUSIONS

Regardless of BMI, patients experience significant improvements in physical function, disability, pain, and mental health after CDR for disc herniation. Patients with obesity do not suffer inferior patient-perceived outcomes after CDR. These findings may help surgeons counsel patients in the preoperative period.

Does obesity and varying body mass index affect the clinical outcomes and safety of biportal endoscopic lumbar decompression? A comparative cohort study

BACKGROUND

Endoscopic spine surgery has recently grown in popularity due to the potential benefits of reduced pain and faster recovery time as compared to open surgery. Biportal spinal endoscopy has been successfully applied to lumbar disc herniations and lumbar spinal stenosis. Obesity is associated with increased risk of complications in spine surgery. Few prior studies have investigated the impact of obesity and associated medical comorbidities with biportal spinal endoscopy.

METHODS

This study was a prospectively collected, retrospectively analyzed comparative cohort design. Patients were divided into cohorts of normal body weight (Bone Mass Index (BMI)18.0-24.9), overweight (BMI 25.0-29.9) and obese (BMI > 30.0) as defined by the World Health Organization (WHO). Patients underwent biportal spinal endoscopy by a single surgeon at a single institution for treatment of lumbar disc herniations and lumbar spinal stenosis. Demographic data, surgical complications, and patient-reported outcomes were analyzed. Statistics were calculated amongst treatment groups using analysis of variance and chi square where appropriate. Statistical significance was determined as p < 0.05.

RESULTS

Eighty-four patients were followed. 26 (30.1%) were normal BMI, 35 (41.7%) were overweight and 23 (27.4%) were obese. Patients with increasing BMI had correspondingly greater American Society of Anesthesiologist (ASA) scores. There were no significant differences in VAS Back, VAS Leg, and ODI scores, or postoperative complications among the cohorts. There were no cases of surgical site infections in the cohort. All cohorts demonstrated significant improvement up to 1 year postoperatively.

CONCLUSIONS

This study demonstrates that obesity is not a risk factor for increased perioperative complications with biportal spinal endoscopy and has similar clinical outcomes and safety profile as compared to patients with normal BMI. Biportal spinal endoscopy is a promising alternative to traditional techniques to treat common lumbar pathology.

The impact of being overweight or obese on 12 month clinical recovery in patients following lumbar microdiscectomy for radiculopathy

BACKGROUND CONTEXT

The proportion of patients who undergo lumbar microdiscectomy due to lumbar radiculopathy who are also overweight or obese is high. However, whether high body mass index (BMI) affects clinical outcomes is not well-studied.

PURPOSE

To investigate the difference in the clinical course between normal weight, overweight, and obese patients with radiculopathy who underwent lumbar microdiscectomy followed by physical therapy and to evaluate whether high BMI is associated with poor recovery.

STUDY DESIGN/SETTING

A prospective cohort study with a 12-month follow-up was conducted in a multidisciplinary clinic.

PATIENT SAMPLE

We included 583 patients (median [IQR] age: 45 [35-52] years; 41% female) with clinical signs and symptoms of lumbar radiculopathy, consistent with magnetic resonance imaging findings, who underwent microdiscectomy followed by postoperative physical therapy.

OUTCOME MEASURES

Outcomes were leg pain and back pain intensity measured with a visual analogue scale, disability measured with the Roland Morris Disability Questionnaire at 3 and 12-month follow-ups, and complications.

METHODS

Patients were classified as being normal weight (46.9%), overweight (38.4%), or obese (14.7%). A linear mixed-effects model was used to assess the difference in the clinical course of pain and disability between the three BMI categories. The association between BMI and outcomes was evaluated using univariable and multivariable logistic regression analyses.

RESULTS

All three patient groups experienced a significant improvement in leg pain, back pain, and disability over 3 and 12-month follow-up. Patients who were overweight, obese, or normal weight experienced comparable leg pain (p=.14) and disability (p=.06) over the clinical course (p=.14); however, obese patients experienced higher back pain (MD=-6.81 [95%CI: -13.50 to -0.14]; p=.03). The difference in back pain scores was not clinically relevant.

CONCLUSIONS

In the first year following lumbar microdiscectomy, patients demonstrated clinical improvements and complications that were unrelated to their preoperative BMI.

Influence of body mass index on severity of rotator cuff tears

BACKGROUND

Research on the relationship between obesity and rotator cuff tears (RCTs) has been limited to the impact of obesity on the results of arthroscopic repair of RCTs; thus, a need for rigorous research controlling for other factors affecting RCTs is warranted, especially to better understand the impact of body mass index (BMI) on RCT severity.

METHODS

A retrospective study of admission records contained in electronic medical records pertaining to patients who were admitted for RCT repair on 1 shoulder between January 2018 and July 2022 was conducted. In total, 386 patients were included. In accordance with guidance regarding obesity from Taiwan's Ministry of Health and Welfare, patients were divided into three groups: underweight or normal weight (BMI <24.0 kg/m2), overweight (BMI 24.0-26.9 kg/m2), or obese (BMI ≥27.0 kg/m2). Magnetic resonance imaging was used to assess RCT severity in terms of four parameters: Patte stage (PS), fatty infiltration (FI), anteroposterior tear size (AP), and retraction size. Multinomial logistic regression analysis was performed on PS and FI grade data, and multiple linear regression analysis was performed on AP tear size and retraction size in order to analyze impact.

RESULTS

Our results revealed that the average age of the 386 patients was 63.41 years (SD = 9.29) and the mean BMI was 25.88 (SD = 3.72) kg/m2. We found significant differences in PS (P = .003), FI (P < .001), retraction size (P = .001), and AP tear size (P = .001) among patients who were underweight or normal weight, overweight, and obese. After controlling for other risk factors, including age, gender, RCT-prone occupation, duration of shoulder pain prior to surgery, history of shoulder injury, and tobacco use, we found that obese patients had higher severity levels in PS (B = 1.21, OR = 3.36, P = .029), FI (B = 1.38, OR = 3.96, P < .001), retraction size (β = 0.18, P = .001), and AP tear size (β = 0.18, P = .001) compared to underweight or normal weight patients.

CONCLUSIONS

Our study demonstrates that a correlation exists between BMI-measured obesity and RCT severity. We therefore suggest that adults control their weight given that maintaining a healthy weight is highly associated with better shoulder health.

Minimally Invasive Bilateral Decompressive Lumbar Laminectomy with Unilateral Approach Among Obese versus Nonobese Patients

OBJECTIVE

Decompressive lumbar laminectomy (DLL) is a common procedure for lumbar stenosis. A unilateral approach, unlike the traditional open approach, spares the posterior elements to mitigate the risk of iatrogenic instability associated with a DLL. Various minimally invasive techniques have been described but little attention has been aimed toward this specific microsurgical approach, particularly regarding obese patients. We aimed to compare operative details, perioperative outcomes, and complication profiles between obese and nonobese patients.

METHODS

One hundred and ninety-four patients who underwent bilateral laminectomy with a unilateral approach by the study surgeon from July 2013 to June 2018 were included. Of these patients, 105 were classified as obese, with body mass index (BMI) ≥30.0 kg/m2, and 89 were nonobese, with BMI <30.0 kg/m2. The obese and nonobese groups were compared; operative time, blood loss, and complications were assessed.

RESULTS

Operative time was nonsignificantly increased in the obese group (177 vs. 166 minutes; P = 0.21) and estimated blood loss was nonsignificantly lower (91 mL vs. 97 mL; P = 1.00) in the obese group. Durotomy rates (3 [2.9%] obese vs. 2 [2.2%] nonobese; P = 0.789) and postoperative wound drainage rates (4 [3.8%] obese vs. 2 [3.8%] nonobese; P = 0.92) did not significantly differ between the 2 groups. Length of stay was significantly longer in the obese group (1.5 vs. 1.0 days; P = 0.0005).

CONCLUSIONS

Compared with the nonobese group, the obese group had significantly longer length of hospitalization, as well as nonsignificantly increased length of operation and decreased blood loss. The 2 groups had similar perioperative complication rates.

Bariatric Surgery Before Spine Surgery is Associated With Fewer Postsurgical Complications: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

To perform a systematic review and meta-analysis investigating the rate of adverse events after spine surgery in patients who underwent bariatric surgery (BS).

SUMMARY OF BACKGROUND DATA

Obesity is an established risk factor for postoperative complications after spine surgery. BS has been associated with improvements in health in patients with severe obesity. However, it is not known whether undergoing BS before spine surgery is associated with reduced adverse outcomes.

MATERIALS AND METHODS

PubMed, EMBASE, Scopus, and Web-of-Science were systematically searched according to "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" guidelines. The search included indexed terms and text words from database inception to the date of the search (May 27, 2022). Data and estimates were pooled using the Mantel-Haenszel method for random-effects meta-analysis. Risk of bias was assessed using the Joanna Briggs Institute risk of bias tool. The primary outcome was an all-cause complication rate after surgery. Relative risks for surgical and medical complications were assessed.

RESULTS

A total of 4 studies comprising 177,273 patients were included. The pooled analysis demonstrated that the all-cause medical complication rate after spine surgery was lower in patients undergoing BS (relative risk: 0.54, 95% CI: 0.39, 0.74, P < 0.01). There was no difference in rates of surgical complications and 30-day hospital readmission rates between the cohort undergoing BS before spine surgery and the cohort that did not.

CONCLUSION

These analyses suggest that obese patients undergoing BS before spine surgery have significantly lower adverse event rates. Future prospective studies are needed to corroborate these findings.

LEVEL OF EVIDENCE

4.

The effect of subcutaneous fat and skin-to-lamina distance on complications and functional outcomes of minimally invasive lumbar decompression

PURPOSE

Minimally invasive lumbar decompression (MIS) in obese pzatients is technically challenging due to the use of longer tube retractors. The purpose of this study was to evaluate the impact of the thickness of the soft tissue and subcutaneous fat on complications, revisions, and patient-reported functional outcomes after MIS.

METHODS

This is a retrospective analysis of 148 consecutive patients who underwent minimally invasive lumbar decompression at our institute between 2013 and 2017 and had at least one year of follow-up. Analysis was performed five times, each time the study group was defined by another measure of adiposity: BMI > 30, skin to lamina distance at the site of surgery and at L4 > 6 cm, and subcutaneous fat thickness at the site of surgery and at L4 > 3 cm. Outcomes included intraoperative complications (durotomy or neurological deficit), possibly inadequate decompression (residual disc, reoperation), length of stay, return to the emergency room or readmission, postoperative medical complications, and functional outcomes: visual analog scores for back and leg pain, and Oswestry Disability Index (ODI).

RESULTS

Patients with a thicker layer soft tissue had a significantly higher burden of comorbidities than controls, including higher prevalence of cardiovascular disease (p = 0.002), diabetes (p < 0.001), hypertension (p < 0.001) and higher ASA scores (p = 0.002). Nevertheless, there was no significant difference between the patient groups in surgical and medical complications, functional outcomes, and other assessed outcomes.

CONCLUSION

Our results indicate that minimally invasive lumbar decompression is safe and effective for patients with a thick layer of soft tissue and subcutaneous fat.

Clinical outcomes, MRI evaluation and predictive factors of indirect decompression with lateral transpsoas approach for lumbar interbody fusion: a multicenter experience

Introduction

Evaluating the effects of indirect decompression obtained through lateral lumbar interbody fusion (LLIF) by clinical improvements and radiological parameters on MRI scans. Identifying predictors of better decompression and clinical outcome.

Materials and methods

From 2016 to 2019, patients who underwent single- or double-level indirect decompression LLIF were consecutively reviewed. Radiological signs of indirect decompression were evaluated in preoperative and follow-up MRI studies and were subsequently correlated to clinical data, expressed as axial/radicular pain (VAS back/leg), index of disability (Oswestry Disability Index) and clinical severity of lumbar stenosis (Swiss Spinal Stenosis Questionnaire).

Results

72 patients were enrolled. The mean follow-up was 24 months. Differences in vertebral canal area (p &lt; 0.001), height of the foramina (p &lt; 0.001), thickness of the yellow ligament (p = 0.001) and anterior height of the interbody space (p = 0.02) were observed. Older age (p = 0.042), presence of spondylolisthesis (p = 0.042), presence of intra-articular facet effusion (p = 0.003) and posterior height of the implanted cage (p = 0.020) positively affected the increase of the canal area. Change in root canal area (p &lt; 0.001), height of the implanted cage (p = 0.020) and younger age (p = 0.035) were predictive factors of root pain relief, while increased vertebral canal area (p = 0.020) and height of the interbody fusion cage (p = 0.023) positively affected the severity of clinical stenosis.

Conclusions

LLIF indirect decompression showed both clinical and radiological improvements. Presence and degree of spondylolisthesis, presence of intra-articular facet effusion, age of the patient and height of the cage were predictive factors of major clinical improvements.

Impact of obesity on complications and surgical outcomes after adult degenerative scoliosis spine surgery

OBJECTIVE

To compare perioperative outcomes of obese versus non-obese adult patients who underwent degenerative scoliosis spine surgery.

METHODS

235 patients who underwent thoracolumbar adult spinal deformity (ASD) surgery (≥4 levels) were identified and categorized into two cohorts based on their body mass indices (BMI): obese (BMI ≥30 kg/m²; n = 81) and non-obese (BMI <30 kg/m²; n = 154). Preoperative (demographics, co-morbidities, American Society of Anesthesiologists (ASA) score and modified frailty indices (mFI-5 and mFI-11)), intraoperative (estimated blood loss (EBL) and anesthesia duration), and postoperative (complication rates, Oswestry Disability Index (ODI) scores, discharge destination, readmission rates, and survival) characteristics were analyzed by student's t, chi-squared, and Mann-Whitney U tests.

RESULTS

Obese patients were more likely to be Black/African-American (p < 0.05, OR:4.11, 95% CI:1.20-14.10), diabetic (p < 0.05, OR:10.18, 95% CI:4.38-23.68) and had higher ASA (p < .01) and psoas muscle indices (p < 0.0001). Furthermore, they had greater pre- and post-operative ODI scores (p < 0.05) with elevated mFI-5 (p < 0.0001) and mFI-11 (p < 0.01). Intraoperatively, obese patients were under anesthesia for longer time periods (p < 0.05) with higher EBL (p < 0.05). Postoperatively, while they were more likely to have complications (OR:1.77, 95% CI:1.01 - 3.08), had increased postop days to initiate walking (p < .05) and were less likely to be discharged home (OR:0.55, 95% CI:0.31-0.99), no differences were found in change in ODI scores or readmission rates between the two cohorts.

CONCLUSIONS

Obesity increases pre-operative risk factors including ASA, frailty and co-morbidities leading to longer operations, increased EBL, higher complications and decreased discharge to home. Pre-operative assessment and systematic measures should be taken to improve peri-operative outcomes.

The Impact of Cognitive Impairment on Postoperative Complications After Spinal Surgery: A Matched Analysis

OBJECTIVE

The coprevalence of age-related comorbidities such as cognitive impairment and spinal disorders is increasing. No studies to date have assessed the postoperative spine surgery outcomes of patients with mild cognitive impairment (MCI) or severe cognitive impairment (dementia) compared with those without preexisting cognitive impairment.

METHODS

Using all-payer claims database, 235,123 persons undergoing either cervical or lumbar spine procedures between January 2010 and October 2020 were identified. Exact 1:1:1 matching based on baseline patient demographics and comorbidities was used to create a dementia group, MCI group, and control group without MCI/dementia (n = 3636). The primary outcome was the rate of any 30-day major postoperative complications. Secondary outcomes included the rates of revision surgery, readmission rates within 30 days, and health care costs within 1 year postoperatively.

RESULTS

Compared with the control group, patients with dementia had an 8-fold and 5.4-fold increase in all-cause 30-day complications after undergoing cervical and lumbar spine procedures, respectively. Similarly, patients with MCI had a 3.1-fold and 2.2-fold increase in all-cause 30-day complications, respectively. Patients with either MCI or dementia had increased rates of pneumonia and urinary tract infection after either spine procedure compared with control (P < 0.01). Odds of revision surgery were increased in the lumbar surgery cohort for dementia (3.43; 95% confidence interval, 1.69-6.95) and for MCI (2.41; 95% confidence interval, 1.14-5.05).

CONCLUSIONS

This is the first study to characterize the postoperative complications profile of patients with preexisting dementia or MCI undergoing cervical and lumbar spine surgery. Both dementia and MCI are associated with increased postoperative complications within 30 days.

Clinical outcomes after surgery for cervical radiculopathy performed in public and private hospitals : a nationwide relative effectiveness study

AIMS

The number of patients undergoing surgery for degenerative cervical radiculopathy has increased. In many countries, public hospitals have limited capacity. This has resulted in long waiting times for elective treatment and a need for supplementary private healthcare. It is uncertain whether the management of patients and the outcome of treatment are equivalent in public and private hospitals. The aim of this study was to compare the management and patient-reported outcomes among patients who underwent surgery for degenerative cervical radiculopathy in public and private hospitals in Norway, and to assess whether the effectiveness of the treatment was equivalent.

METHODS

This was a comparative study using prospectively collected data from the Norwegian Registry for Spine Surgery. A total of 4,750 consecutive patients who underwent surgery for degenerative cervical radiculopathy and were followed for 12 months were included. Case-mix adjustment between those managed in public and private hospitals was performed using propensity score matching. The primary outcome measure was the change in the Neck Disability Index (NDI) between baseline and 12 months postoperatively. A mean difference in improvement of the NDI score between public and private hospitals of ≤ 15 points was considered equivalent. Secondary outcome measures were a numerical rating scale for neck and arm pain and the EuroQol five-dimension three-level health questionnaire. The duration of surgery, length of hospital stay, and complications were also recorded.

RESULTS

The mean improvement from baseline to 12 months postoperatively of patients who underwent surgery in public and private hospitals was equivalent, both in the unmatched cohort (mean NDI difference between groups 3.9 points (95% confidence interval (CI) 2.2 to 5.6); p < 0.001) and in the matched cohort (4.0 points (95% CI 2.3 to 5.7); p < 0.001). Secondary outcomes showed similar results. The duration of surgery and length of hospital stay were significantly longer in public hospitals. Those treated in private hospitals reported significantly fewer complications in the unmatched cohort, but not in the matched cohort.

CONCLUSION

The clinical effectiveness of surgery for degenerative cervical radiculopathy performed in public and private hospitals was equivalent 12 months after surgery.Cite this article: Bone Joint J 2023;105-B(1):64-71.

Obesity and Workers' Compensation in the Setting of Minimally Invasive Lumbar Decompression

OBJECTIVE

To investigate the influence of body mass index (BMI) on perioperative outcomes, postoperative patient-reported outcome measures (PROMs), and minimal clinically important difference (MCID) achievement among workers' compensation (WC) claimants undergoing minimally invasive lumbar decompression (MIS-LD).

METHODS

WC patients diagnosed with herniated nucleus pulposus undergoing single-level MIS-LD were identified. Patients were divided into 3 groups: Non-obese (<30 kg/m²), Obese I (≥30 and <35 kg/m²), and Obese II/III (≥35 kg/m²). PROMs were collected preoperatively and at 6 weeks, 12 weeks, 6 months, 1 year, and 2 years postoperatively. The predictive influence of BMI grouping on mean PROM scores was computed using simple linear regression. To compare PROMs between groups, post hoc pairwise comparisons of adjusted means were utilized. MCID achievement was compared between groups with χ² analysis.

RESULTS

A total of 81 patients were in the Non-obese cohort, and 43 and 45 in the Obese I and Obese II/III cohorts, respectively. Visual analog scale (VAS) leg, Oswestry Disability Index (ODI), and 12-Item Short Form Physical Composite Score (SF-12 PCS) were worse in the Obese I cohort at 12 weeks, and SF-12 PCS was lower in the Obese I vs. Obese II/III subgroup analysis (P ≤ 0.045, all). MCID achievement rates for ODI were higher for the Non-obese group at 12 weeks and overall (P ≤ 0.049, both). MCID attainment for VAS back was higher among the Non-obese cohort at 6-weeks (P = 0.022).

CONCLUSIONS

Patients with higher levels of obesity were more likely to experience longer length of stay and delayed discharge following MIS-LD. Increasing BMI was generally not a significant predictor of postoperative pain, disability, or physical health PROMs at most timepoints. MCID achievement rates for disability relief were significantly higher for non-obese patients.