Effect modifiers for patient-reported outcomes in operatively and nonoperatively treated patients with adult symptomatic lumbar scoliosis: a combined analysis of randomized and observational cohorts

View More View Less
  • 1 Department of Orthopedic Surgery, Washington University School of Medicine, St. Louis, Missouri;
  • | 2 Department of Medicine, Dartmouth Medical School, Hanover, New Hampshire;
  • | 3 Denver International Spine Center, Denver, Colorado;
  • | 4 Department of Neurological Surgery, University of Virginia, Charlottesville, Virginia;
  • | 5 Hospital for Special Surgery, New York, New York; and
  • | 6 Department of Orthopedic Surgery, Columbia University, New York, New York
Free access

OBJECTIVE

Adult symptomatic lumbar scoliosis (ASLS) is a common and disabling condition. The ASLS-1 was a multicenter, dual-arm study (with randomized and observational cohorts) examining operative and nonoperative care on health-related quality of life in ASLS. An aim of ASLS-1 was to determine patient and radiographic factors that modify the effect of operative treatment for ASLS.

METHODS

Patients 40–80 years old with ASLS were enrolled in randomized and observational cohorts at 9 North American centers. Primary outcomes were the differences in mean change from baseline to 2-year follow-up for the SRS-22 subscore (SRS-SS) and the Oswestry Disability Index (ODI). Analyses were performed using an as-treated approach with combined cohorts. Factors examined were prespecified or determined using regression tree analysis. For each potential effect modifier, subgroups were created using clinically relevant cutoffs or via regression trees. Estimates of within-group and between-group change were compared using generalized linear mixed models. An effect modifier was defined as a treatment effect difference greater than the minimal detectable measurement difference for both SRS-SS (0.4) and ODI (7).

RESULTS

Two hundred eighty-six patients were enrolled and 256 (90%) completed 2-year follow-up; 171 received operative treatment and 115 received nonoperative treatment. Surgery was superior to nonoperative care for all effect subgroups considered, with the exception of those with nearly normal pelvic incidence−lumbar lordosis (PI–LL) match (≤ 11°). Male patients and patients with more (> 11°) PI–LL mismatch at baseline had greater operative treatment effects on both the SRS-SS and ODI compared to nonoperative treatment. No other radiographic subgroups were associated with treatment effects. High BMI, lower socioeconomic status, and poor mental health were not related to worse outcomes.

CONCLUSIONS

Numerous factors previously related to poor outcomes with surgery, such as low mental health, lower socioeconomic status, and high BMI, were not related to outcomes in ASLS in this exploratory analysis. Those patients with higher PI–LL mismatch did improve more with surgery than those with normal alignment. On average, none of the factors considered were associated with a worse outcome with operative treatment versus nonoperative treatment. These findings may guide future prospective analyses of factors related to outcomes in ASLS care.

ABBREVIATIONS

ASLS = adult symptomatic lumbar scoliosis; BMD = bone mineral density; GLMM = generalized linear mixed model; HRQOL = health-related quality of life; LL = lumbar lordosis; MCID = minimum clinically important difference; MCS = mental component summary; MDMD = minimum detectable measurement difference; NRS = numeric rating scale; ODI = Oswestry Disability Index; PCS = physical component summary; PI = pelvic incidence; PRO = patient-reported outcome; SRS-SS = SRS-22 subscore.

OBJECTIVE

Adult symptomatic lumbar scoliosis (ASLS) is a common and disabling condition. The ASLS-1 was a multicenter, dual-arm study (with randomized and observational cohorts) examining operative and nonoperative care on health-related quality of life in ASLS. An aim of ASLS-1 was to determine patient and radiographic factors that modify the effect of operative treatment for ASLS.

METHODS

Patients 40–80 years old with ASLS were enrolled in randomized and observational cohorts at 9 North American centers. Primary outcomes were the differences in mean change from baseline to 2-year follow-up for the SRS-22 subscore (SRS-SS) and the Oswestry Disability Index (ODI). Analyses were performed using an as-treated approach with combined cohorts. Factors examined were prespecified or determined using regression tree analysis. For each potential effect modifier, subgroups were created using clinically relevant cutoffs or via regression trees. Estimates of within-group and between-group change were compared using generalized linear mixed models. An effect modifier was defined as a treatment effect difference greater than the minimal detectable measurement difference for both SRS-SS (0.4) and ODI (7).

RESULTS

Two hundred eighty-six patients were enrolled and 256 (90%) completed 2-year follow-up; 171 received operative treatment and 115 received nonoperative treatment. Surgery was superior to nonoperative care for all effect subgroups considered, with the exception of those with nearly normal pelvic incidence−lumbar lordosis (PI–LL) match (≤ 11°). Male patients and patients with more (> 11°) PI–LL mismatch at baseline had greater operative treatment effects on both the SRS-SS and ODI compared to nonoperative treatment. No other radiographic subgroups were associated with treatment effects. High BMI, lower socioeconomic status, and poor mental health were not related to worse outcomes.

CONCLUSIONS

Numerous factors previously related to poor outcomes with surgery, such as low mental health, lower socioeconomic status, and high BMI, were not related to outcomes in ASLS in this exploratory analysis. Those patients with higher PI–LL mismatch did improve more with surgery than those with normal alignment. On average, none of the factors considered were associated with a worse outcome with operative treatment versus nonoperative treatment. These findings may guide future prospective analyses of factors related to outcomes in ASLS care.

ABBREVIATIONS

ASLS = adult symptomatic lumbar scoliosis; BMD = bone mineral density; GLMM = generalized linear mixed model; HRQOL = health-related quality of life; LL = lumbar lordosis; MCID = minimum clinically important difference; MCS = mental component summary; MDMD = minimum detectable measurement difference; NRS = numeric rating scale; ODI = Oswestry Disability Index; PCS = physical component summary; PI = pelvic incidence; PRO = patient-reported outcome; SRS-SS = SRS-22 subscore.

In Brief

Data from a prospective study were used to determine patient-level factors associated with postoperative outcomes, which will ultimately improve results and value in adult spinal deformity surgery.

Adult symptomatic lumbar scoliosis (ASLS) is increasingly prevalent as the US population ages. Patients frequently seek treatment for ASLS because it is a disabling condition similar to diabetes and heart disease in severity.5 The ASLS-1 was a prospective, dual-arm study of ASLS comparing nonoperatively and operatively treated patients to determine the effectiveness of surgery.15 ASLS-1 found that surgical intervention was, on average, associated with greater improvement in health-related quality of life (HRQOL) than nonoperative care. Improvement was not universal in the surgical groups and many nonoperative patients did improve over the first 2 years of study.

Numerous patient-level predictors of outcome have been proposed to affect outcomes, including body habitus, socioeconomic factors such as education and income, and mental health.2–4,8,9,12,17,19 Estimating the effect of these variables on outcomes in ASLS was difficult in prior studies due to loss to follow-up and lack of a nonoperative treatment comparison. An aim of the ASLS-1 study was to analyze patient and radiographic data to determine factors that modify the effect of operative and nonoperative care on patient outcomes. We hypothesized that age, sex, socioeconomic status, education level, mental health, BMI, and bone mineral density (BMD) would affect outcomes during the treatment of ASLS.

Methods

Study Population

The ASLS-1 study was conducted at 9 centers in North America and included randomized and observational patient cohorts.15 All sites obtained IRB approval. This study was registered with the ClinicalTrials.gov database (http://clinicaltrials.gov), and its registration no. is NCT00854828. Eligible patients were 40–80 years old with ASLS, defined as a lumbar curve with a coronal Cobb measurement ≥ 30° and Oswestry Disability Index (ODI) score of ≥ 20 or Scoliosis Research Society-22 (SRS-22) score ≤ 4.0 in pain, function, and/or self-image domains. All patients presented to a spinal deformity surgeon. The SRS-22 is a disease-specific instrument for spinal deformity and the ODI is a disease-specific instrument for lumbar spine disability. Patients with prior spinal fusion or multilevel decompression surgery were excluded.

Patients were offered enrollment in the randomized cohort if they met inclusion criteria and were deemed surgical candidates by the treating physician and patient. Eligible patients who declined randomization were offered enrollment in the concurrent observational cohort. Enrollment began in April 2010 and ended July 2014 (Fig. 1). Details of the operative and nonoperative treatments have been described previously.15

FIG. 1.
FIG. 1.

Flow diagram of combined randomized and observational cohorts to 2-year follow-up. *Withdrawal counts include deaths. F/U = follow-up.

Outcomes of Interest

Primary outcomes were differences in mean change from baseline to 2-year follow-up between the operative and nonoperative groups (mean difference) for two patient-reported outcomes (PROs): the SRS-22 subscore (SRS-SS) and the ODI.6,11 The SRS-22 comprises five domains with scores ranging from 1 to 5, with greater scores indicating a better quality of life. The SRS-SS is the average of these domains excluding satisfaction. Scores for the ODI range from 0 to 100 with greater scores indicating more disability. Assessments were made at enrollment and every 3 months thereafter until 2 years. Enrollment data served as the baseline for patients in the nonoperative cohort, whereas baseline data for surgical patients were updated if necessary within 4 months of surgery. The present analysis includes follow-up data until the first of: 1) patient withdrawal from the study, 2) death, 3) 2 years posttreatment, or 4) January 2017.

Statistical Analysis

Baseline characteristics were compared between patients who did or did not receive operative treatment during the first 2 years of follow-up. Differences were evaluated using chi-square tests for categorical variables (Fisher’s exact test for counts < 5) and Wilcoxon rank-sum tests for continuous variables.

All outcome analyses were performed using an as-treated approach, in which treatment type was considered a time-varying covariate. A number of baseline characteristics were prespecified as potential effect modifiers. These characteristics included demographic and behavioral variables (age, sex, education, income, and BMI), clinical variables (baseline SF-12 Mental Component Summary [MCS, mental health]), and BMD. Additionally, regression tree analysis was conducted to determine important predictors of 2-year SRS and ODI scores that may also modify treatment effects.18 This analysis additionally identified pelvic incidence (PI)−lumbar lordosis (LL) mismatch (PI–LL), stenosis levels, and baseline numeric rating scale (NRS) leg and back pain scores as potential effect modifiers of 2-year outcomes.

For each potential effect modifier, subgroups of patients were defined either by using clinically meaningful cutoffs (i.e., the BMI threshold for overweight [≥ 25 kg/m2]), or informed by cutoffs generated by regression tree analyses. To evaluate the effect of treatment over 2 years, generalized linear mixed models (GLMMs) were used, accounting for correlation among the repeated outcome measures using a heterogeneous autoregressive covariance matrix. Because patients included in the observational cohort chose their treatment and many randomized patients did not adhere to their originally assigned treatment arm, a number of characteristics differed between the treatment groups at baseline.15 To account for confounding resulting from these differences, baseline characteristics were considered for inclusion in the GLMMs if they were defined a priori as important outcome predictors or significantly associated with receipt of operative treatment during the first 2 years of study follow-up (p < 0.10). However, some of these characteristics were excluded from the final GLMMs if they were not associated with treatment or outcomes (2-year ODI score and SRS-SS) in multivariable models with a p value < 0.20. GLMMs stratified by the chosen effect modifier categories were used to estimate mean PRO changes over 2 years following operative and nonoperative treatment for each subgroup of patients. The same models were used to produce estimates of the mean difference in PROs between treatment groups at 2 years posttreatment (and corresponding 95% confidence intervals).

For each effect modifier, a p value for heterogeneity was calculated to determine whether results differed between the subgroups.1 A p value < 0.05 was considered evidence of significant heterogeneity in the treatment effect. All statistical tests were 2-sided. Superiority was defined as a treatment effect greater than or equal to the minimum detectable measurement difference (MDMD) for both the ODI (7) and the SRS-SS (0.4).14 For a covariate to be deemed an effect modifier, the treatment effect difference must be greater than or equal to the MDMD for both the SRS-SS and ODI, as well as significant for both. The MDMD was chosen rather than the minimum clinically important difference (MCID) because the MCID is not meant for comparison of means between groups, but rather for within-patient change.10 When comparing between groups, the MDMD offers a threshold to ensure a difference exists.

Results

Patient Characteristics

Two hundred eighty-six patients were enrolled in the study: 63 in the randomized cohort and 223 in the observational cohort. Two hundred fifty-six (90%) patients completed exactly 2 years of follow-up. There were 12 withdrawals, including 1 death (12/286, 4.2%) at 2 years.

Operative treatment was assigned or chosen at baseline by 142 patients. Six people, assigned to operative treatment, chose to pursue nonoperative care. Nonoperative care was assigned or chosen at baseline by 144 patients. Among these nonoperative patients, 35 underwent surgery within 2 years. As a result of these crossovers, by 2 years 171 patients had received operative treatment, while 115 had only received nonoperative treatment (Fig. 1).

When comparing the baseline characteristics of patients who received operative treatment by 2 years to those who only received nonoperative treatment, operative patients had significantly younger age, higher BMI, higher prevalence of psychiatric disorders, larger lumbar Cobb angles, less LL, greater PI–LL mismatch, and more levels of stenosis (Table 1). Operative patients also had more pain and disability at baseline as measured by the SRS-SS, ODI, NRS back and leg pain, and SF-12 physical component summary (PCS) score. BMD testing using dual-energy x-ray absorptiometry was available for 87% of the patients. The rate of missing data between groups for BMD was not different.

TABLE 1.

Characteristics of operative and nonoperative patients at enrollment in the ASLS cohort

Combined (Randomized + Observational) As-Treated*
CharacteristicOperative (n = 171)Nonoperative (n = 115)p Value
Median age (IQR)60 (53–65)64 (54–70)0.029
Female sex, n (%)152 (88.9)106 (92.2)0.359
Race, n (%)0.148
 White164 (95.8)104 (90.7)
 Black5 (3.0)9 (7.6)
 Other2 (1.2)2 (1.7)
Ethnicity, n (%)0.280
 Hispanic3 (1.8)0 (0)
 Non-Hispanic161 (98.2)109 (100)
 Did not report76
Education, n (%)0.217
 Less than high school7 (4.1)2 (1.7)
 High school diploma or GED41 (24.0)35 (30.4)
 Technical or associate’s degree34 (19.9)16 (13.9)
 Bachelor’s degree38 (22.2)34 (29.6)
 Graduate degree51 (29.8)28 (24.4)
Income per year, n (%)0.758
 <$20,00010 (7.1)7 (6.7)
 $20,000–$39,99919 (13.5)12 (11.5)
 $40,000–$74,99931 (22.0)29 (27.9)
 ≥$75,00081 (57.5)56 (53.9)
Did not report3011
Smoking, n (%)0.967
 Current10 (5.8)7 (6.0)
 Former53 (31.0)34 (29.6)
 Never108 (63.2)74 (64.4)
Median BMI (IQR), kg/m226 (23–30)25 (22–29)0.038
Osteopenia/osteoporosis, n (%)0.562
 BMD not measured21 (12.3)17 (14.8)
 No osteopenia/osteoporosis45 (26.3)29 (25.2)
 T-score −1 to −1.550 (29.2)25 (21.7)
 T-score −1.6 to −2.443 (25.2)32 (27.8)
 T-score −2.5 or worse (or vertebral compression fracture)12 (7.0)12 (10.4)
Hypertension uncontrolled or requiring medications, n (%)0.248
 No100 (58.5)71 (61.7)
 Yes, controlled w/ diet/exercise8 (4.7)1 (0.9)
 Yes, controlled w/ medication62 (36.3)43 (37.4)
 Yes, poorly controlled w/ medication1 (0.6)0 (0)
Diabetes uncontrolled or requiring medications, n (%)0.709
 No161 (94.2)111 (96.5)
 Yes, controlled w/ diet1 (0.6)1 (0.9)
 Yes, controlled w/ oral hypoglycemics7 (4.1)2 (1.7)
 Yes, insulin-dependent2 (1.2)1 (0.9)
Depression/anxiety/psychiatric disorder, n (%)56 (32.7)21 (18.3)0.042
Median duration of back symptoms (IQR), mos30 (0–96)24 (1–120)0.662
Median duration of leg symptoms (IQR), mos0 (0–24)0 (0–8)0.199
Median lumbar Cobb angle (IQR), °55 (44–67)49 (40–57)0.003
Median LL, T12-sacrum (IQR), °−37 (−50 to −25)−45 (−55 to −30)0.009
Median sagittal balance absolute value (IQR), mm28 (13–57)33 (16–57)0.669
Median coronal balance absolute value (IQR), mm19 (9–32)15 (9–29)0.222
Median PI–LL mismatch (IQR), °18 (4–32)13 (1–31)0.023
Median no. of stenosis levels (IQR)1 (0–2)0 (0–1)<0.001
Listhesis, n (%)156 (91.2)98 (85.2)0.114
Median baseline PROs (IQR)
 SRS-SS3.0 (2.7–3.5)3.4 (3.1–3.7)<0.001
 SRS pain2.8 (2.3–3.2)3.0 (2.6–3.6)<0.001
 SRS function3.2 (2.6–3.6)3.4 (3.2–4.0)<0.001
 SRS self-image2.7 (2.2–3.2)3.2 (2.7–3.5)<0.001
 SRS mental health3.8 (3.0–4.2)3.8 (3.4–4.4)0.267
 SRS satisfaction3.0 (2.0–3.0)3.0 (2.5–3.5)0.037§
 ODI score38 (26–50)30 (20–40)<0.001
 NRS back pain7 (5–8)5 (4–7)<0.001
 NRS leg pain4 (1–7)2 (0–5)0.002
 MCS50 (41–60)52 (45–59)0.429
 PCS33 (26–39)39 (29–45)<0.001

GED = General Educational Development; SRS = Scoliosis Research Society.

Includes all patients enrolled in either the randomized cohort or observational cohort. Patients who had an operation within 2 years of study entry are categorized as operative, whereas those who had not had an operation within that time were categorized as nonoperative. Five patients had later operations, but were categorized as nonoperative; 173 total patients had operative treatment in the study.

Information on sagittal and coronal balance was missing in 1 patient assigned to operative treatment in the randomized cohort because baseline images were obtained at an outside facility and did not include scales to permit linear measurements.

Information on PI–LL mismatch was missing for 17 patients, because femoral heads were not visible on radiographs. This included 9 patients in the nonoperative treatment group and 8 patients in the operative treatment group.

While the medians for SRS Satisfaction scores were the same for the combined cohort treatment groups, the overall distribution for the nonoperative group was skewed towards higher scores, resulting in a statistically significant higher rank sum than the operative group.

Outcomes

Operative treatment was significantly associated with superior outcomes in all evaluated subgroups, with the exception of patients with a PI–LL mismatch ≤ −11 (nearly normal LL relative to the PI; Tables 24). In no subgroup of patients did we observe superior outcomes associated with nonoperative treatment.

TABLE 2.

Outcomes in subgroups determined by demographic and behavioral characteristics

ODI ScoreSRS Subscore
Mean Change at 2 yrs (SE)Mean Change at 2 yrs (SE)
SubgroupNonoperativeOperativeDifference in Average Change (95% CI)NonoperativeOperativeDifference in Average Change (95% CI)
Baseline MCS score
 <44, n = 80−2 (3)−16 (2)−14 (−21 to −7)0.2 (0.1)0.8 (0.1)0.6 (0.3–0.8)
 ≥44, n = 206−3 (1)−16 (1)−13 (−17 to −10)0.1 (0.1)0.7 (0.1)0.6 (0.5–0.8)
 p value0.8350.8620.9530.4040.7210.666
Education
 Bachelor’s degree or higher, n = 151−3 (2)−17 (1)−14 (−19 to −10)0.2 (0.1)0.8 (0.1)0.6 (0.4–0.7)
 Less than bachelor’s degree, n = 135−1 (2)−14 (2)−13 (−18 to −8)0.1 (0.1)0.7 (0.1)0.6 (0.5–0.8)
 p value0.4490.1490.7210.3360.7500.616
Income
 ≥$75,000, n = 137−2 (2)−15 (2)−13 (−17 to −8)0.2 (0.1)0.7 (0.1)0.5 (0.3–0.7)
 <$75,000, n = 108−2 (2)−20 (2)−19 (−24 to −13)0.1 (0.1)0.8 (0.1)0.8 (0.6–1.0)
 p value0.9390.0120.1120.1320.1920.052
Smoking
 Ever, n = 104−2 (4)−12 (3)−10 (−20 to −1)0.1 (0.1)0.6 (0.1)0.4 (0.1–0.8)
 Never, n = 182−3 (1)−16 (1)−13 (−17 to −10)0.2 (0.1)0.8 (0.04)0.6 (0.5–0.7)
 p value0.8150.2310.5650.6880.0770.412
BMI
 <25 kg/m2, n = 158−4 (2)−13 (2)−9 (−13 to −4)0.2 (0.1)0.7 (0.1)0.5 (0.3–0.6)
 ≥25 kg/m2, n = 128−1 (2)−18 (1)−17 (−22 to −13)0.1 (0.1)0.8 (0.1)0.7 (0.6–0.9)
 p value0.1760.0060.0060.1730.0410.021
Age
 ≤60 yrs, n = 136−2 (2)−14 (1)−13 (−17 to −8)0.2 (0.1)0.7 (0.1)0.5 (0.4–0.7)
 >60 yrs, n = 150−3 (2)−18 (2)−15 (−20 to −11)0.1 (0.1)0.8 (0.1)0.7 (0.5–0.8)
 p value0.7170.0990.4340.3460.6820.336
Sex
 Male, n = 287 (4)−22 (3)−28 (−40 to −17)*−0.2 (0.2)1.1 (0.1)1.3 (0.9–1.8)*
 Female, n = 258−2 (1)−16 (1)−14 (−18 to −10)*0.2 (0.1)0.7 (0.04)0.6 (0.5–0.7)*
 p value0.0480.1020.019*0.0310.0050.003*

Based on generalized linear mixed effects models adjusting for ODI and SRS score (respectively) at date of intervention, and accounting for the correlation among repeated measures using a heterogeneous autoregressive covariance matrix. Follow-up time was categorized as operative or nonoperative on an as-treated basis. Models are adjusted for baseline ODI, baseline SRS subscore, age, BMI, depression/anxiety/psychiatric disorder, lumbar Cobb angle, LL, stenosis levels, education, osteoporosis, NRS back pain, and PCS. The p values represent the “P” value for heterogeneity, as described by Altman and Bland, 2003.

Determined to be an effect modifier based on mean differences that are greater than or equal to the MDMD and are statistically significant for both the ODI score and the SRS subscore.

TABLE 3.

Outcomes in subgroups determined by radiographic characteristics

ODI ScoreSRS Subscore
Mean Change at 2 yrs (SE)Mean Change at 2 yrs (SE)
SubgroupNonoperativeOperativeDifference in Average Change (95% CI)NonoperativeOperativeDifference in Average Change (95% CI)
Lumbar Cobb angle
 ≤50°, n = 140−3 (2)−19 (2)−16 (−21 to −12)0.1 (0.1)0.9 (0.1)0.8 (0.6–0.9)
 >50°, n = 145−1 (2)−14 (1)−13 (−18 to −9)0.2 (0.1)0.7 (0.1)0.5 (0.3–0.7)
 p value0.4250.0180.3720.2840.0200.024
PI–LL mismatch
 ≤−11, n = 29−1 (3)−5 (4)−4 (−13 to 5)*0.3 (0.1)0.4 (0.2)0.1 (−0.3 to 0.5)*
 >−11, n = 257−3 (1)−17 (1)−14 (−18 to −11)*0.1 (0.1)0.8 (0.04)0.6 (0.5–0.8)*
 p value0.6820.0020.033*0.2280.0180.012*
Coronal balance, absolute value
 ≤15 mm, n = 128−2 (2)−16 (2)−13 (−18 to −9)0.2 (0.1)0.8 (0.1)0.6 (0.4–0.7)
 >15 mm, n = 156−3 (2)−16 (1)−13 (−18 to −9)0.1 (0.1)0.8 (0.1)0.6 (0.4–0.8)
 p value0.9220.8890.9860.5580.9800.680

Determined to be an effect modifier based on mean differences that are greater than or equal to the MDMD and are statistically significant for both the ODI score and the SRS subscore.

TABLE 4.

Outcomes in subgroups determined by clinical characteristics

ODI ScoreSRS Subscore
Mean Change at 2 yrs (SE)Mean Change at 2 yrs (SE)
SubgroupNonoperativeOperativeDifference in Average Change (95% CI)NonoperativeOperativeDifference in Average Change (95% CI)
Baseline ODI
 <36, n = 148−2 (1)−11 (1)−10 (−13 to −7)*0.2 (0.04)0.7 (0.1)0.4 (0.3–0.6)*
 ≥36, n = 138−1 (3)−20 (2)−19 (−25 to −13)*0.0 (0.1)0.8 (0.1)0.8 (0.6–1.1)*
 p value0.773<0.0010.006*0.0210.0350.002*
Baseline SRS-SS
 <3, n = 931 (4)−18 (2)−19 (−27 to −11)−0.1 (0.1)1.0 (0.1)1.0 (0.7–1.3)
 ≥3, n = 193−3 (1)−15 (1)−12 (−15 to −9)0.2 (0.04)0.6 (0.04)0.5 (0.3–0.6)
 p value0.3110.1250.0980.122<0.001<0.001
Stenosis levels
 0 levels, n = 154−2 (1)−13 (1)−12 (−15 to −8)0.2 (0.1)0.7 (0.1)0.5 (0.4–0.7)
 1+ levels, n = 132−1 (2)−20 (2)−19 (−25 to −14)0.1 (0.1)0.9 (0.1)0.79 (0.6–1.0)
 p value0.7580.0010.0260.2890.0400.040
Baseline NRS leg pain
 <7, n = 227−2 (1)−14 (1)−12 (−15 to −8)0.2 (0.1)0.7 (0.1)0.5 (0.4–0.7)
 ≥7, n = 59−2 (3)−23 (2)−21 (−29 to −13)0.1 (0.1)1.0 (0.1)0.8 (0.5–1.2)
 p value0.929<0.0010.0370.8210.0050.094
Baseline NRS back pain
 <6, n = 113−2 (1)−15 (1)−12 (−16 to −9)0.1 (0.1)0.7 (0.1)0.5 (0.4–0.7)
 ≥6, n = 173−1 (2)−17 (1)−16 (−21 to −12)0.2 (0.1)0.8 (0.1)0.7 (0.5–0.8)
 p value0.5510.1740.1900.8160.1040.368
BMD
 No diagnosed osteopenia/osteoporosis, n = 112−2 (2)−18 (1)−17 (−21 to −13)0.1 (0.1)0.8 (0.1)0.7 (0.5–0.9)
 Osteopenia/osteoporosis, T-score <−1 or history of vertebral fracture, n = 174−3 (2)−14 (2)−11 (−16 to −7)0.2 (0.1)0.7 (0.1)0.5 (0.4–0.7)
 p value0.5610.0460.0890.6460.0730.137

Determined to be an effect modifier based on mean differences that are greater than or equal to the MDMD and are statistically significant for both the ODI score and the SRS subscore.

Demographic and Behavioral Subgroups

Overweight patients (BMI ≥ 25 kg/m2) had greater average improvements after surgery compared with normal or underweight patients (ODI, p = 0.006, SRS-SS, p = 0.04; Table 2). As a result, overweight patients experienced greater treatment effects of operative versus nonoperative treatment than did normal/underweight patients as measured by both the ODI and SRS-SS: ODI mean difference of −17 (95% CI −22 to −13) for overweight and −9 (95% CI −13 to −4) for normal/underweight; and an SRS-SS mean difference of 0.7 (95% CI 0.6–0.9) for overweight and 0.5 (95% CI 0.3–0.6) for normal/underweight (Table 2). However, the differences in treatment effects as measured by SRS-SS were below the MDMD threshold.

Men made up a small portion of the study population (N = 28). Nonoperative outcomes were worse for men than women. Men also experienced more improvement with surgery, compared to nonoperative treatment, than women (ODI mean difference −28 [95% CI −40 to −17] for men and −14 [95% CI −18 to −10] for women; SRS-SS mean difference of 1.3 [95% CI 0.9–1.8] for men and 0.6 [95% CI 0.5–0.7] for women). Age, MCS, education, income level, and smoking (current or past) were not significant effect modifiers.

Radiographic Subgroups

Operative patients with a lumbar Cobb angle ≤ 50° reported greater mean improvements in their SRS-SS over 2 years than those with a lumbar Cobb angle > 50° (mean change in SRS-SS = 0.9 for lumbar Cobb ≤ 50° and 0.7 for lumbar Cobb > 50°, p = 0.020; Table 3). Correspondingly, greater effects of operative treatment compared with nonoperative treatment were observed among patients with a lumbar Cobb angle ≤ 50° (SRS-SS mean difference of 0.8 [95% CI 0.6–0.9] for Cobb angles ≤ 50° and 0.5 [95% CI 0.3–0.7] for Cobb angles > 50°; Table 3). While a similar pattern was observed for the 2-year ODI, treatment effects based on this measure did not differ significantly between those with a smaller versus larger lumbar Cobb angle (p = 0.372). Patients with smaller curves had somewhat more stenosis and leg pain than those with larger curves, although not to a significant extent (stenosis p value = 0.180, leg pain p value = 0.160).

The 2-year operative treatment effect was greater among patients with a PI–LL mismatch > −11 (less LL relative to PI) compared to patients with PI–LL mismatch ≤ −11 (more LL relative to PI; ODI mean difference −14 [95% CI −18 to −11] for PI–LL mismatch > −11 and −4 [95% CI −13 to 5] for ≤ −11; SRS-SS mean difference 0.6 [95% CI 0.5–0.8] for PI–LL mismatch > −11 and 0.1 [95% CI −0.3 to 0.5] for ≤ −11). This difference appeared mainly driven by larger improvements in operative patients with greater PI–LL mismatch (Table 3). Treatment effects did not significantly differ between groups with different levels of coronal balance for either the ODI or the SRS-SS.

Clinical Subgroups

The effect of operative treatment also differed significantly based on a patient’s baseline PROs, specifically for the ODI, SRS-SS, and NRS leg pain (Table 4). Operative patients with a baseline ODI of ≥ 36 had greater improvements in both their ODI and SRS-SS scores over 2 years compared to operative patients with a baseline ODI < 36 (ODI, p < 0.001, SRS-SS, p = 0.035), while nonoperative patients with a baseline ODI of ≥ 36 had less improvement in their SRS-SS compared to nonoperative patients with baseline ODI < 36 (p = 0.021). Similar patterns were observed for the SRS-SS, in which differences in the treatment effect reached the MDMD for both the SRS-SS and ODI, but were not significant for the ODI. Similarly, patients with worse leg pain or more stenosis at baseline reported greater benefits from operative treatment, but these did not reach the MDMD threshold for both PROs (Table 4). Treatment effects did not differ for patients based on their level of back pain as measured by the NRS or for baseline BMD (Table 4).

Discussion

ASLS is a disabling condition and surgical treatment is effective in improving quality of life, while nonoperative care is generally not associated with HRQOL improvement.7,12,15 Surgery is costly, however, and improvement after surgery is not universal. In a value-driven healthcare economy, knowledge of both fixed and modifiable patient factors that affect outcomes in ASLS is needed to maximize patient benefit and value. We sought to determine which effect modifiers were associated with a change in PROs at 2-year follow-up in a multicenter, dual-arm study of patients treated with operative and nonoperative care for ASLS.

The only patient demographic effect modifier was male sex, with superior operative outcomes in both PRO measures. We interpret these findings with caution, however, due to the small number of men enrolled in the study. An appropriate interpretation may be that males do not do worse with ASLS surgery, a finding consistent with prior adult deformity studies.8 Patients with higher BMI (≥ 25 kg/cm2) did not have inferior outcomes compared to patients with lower BMI and had higher average improvements, although we do not classify BMI as a formal effect modifier as the observed differences were less than the MDMD. Our observations may reflect the postoperative metabolic needs of ASLS patients, with a greater caloric reserve offering the opportunity for greater PRO improvement, but we have no current data to verify that hypothesis. Socioeconomic factors, such as education and income, did not modify treatment effects. Lower MCS scores did not adversely affect improvement after surgery, an encouraging finding as more operative patients reported a history of a mental health diagnosis.

Radiographic characteristics were not associated with differences in outcomes after nonoperative care. With operative treatment, however, patients with more PI–LL mismatch (≥ 11°) had superior outcomes compared to those with less mismatch. Smaller coronal Cobb angle measurements (≤ 50°) were not inferior to larger measurements. These patients had more leg pain and more levels of stenosis, although not to a significant extent. These data suggest that pain secondary to neural compression may improve more than surgery performed solely for progressive deformity or axial pain. These findings are distinctly different from an analysis of a heterogeneous cohort of primary and revision adult deformity cases, in which patients with predominant leg pain fared worse in terms of overall improvement.20 The pathology causing leg pain in a revision setting may be different from a primary deformity causing radiculopathy and/or claudication. Overall, worse baseline PROs (ODI more than SRS-SS) were associated with more improvement after surgery. This result is perhaps not unexpected because those patients with worse PROs have the greatest potential for improvement.

Factors associated with good and bad outcomes have been studied in several other spinal deformity registries.2,3,9,12,17 Despite biases against lower mental health scores, multiple studies have failed to show worse treatment effects in these patients.4,16,19 It is important to recognize that patients with worse mental health tend to start with worse baseline scores (more so with ODI than SRS-SS in our study) and finish with worse scores, but the relative improvement is maintained. Analyses of socioeconomic status in total joint arthroplasty are consistent with our findings, which may allay concerns when treating lower socioeconomic strata patients.13,21 Predictive models for PRO scores found that worse baseline PROs were associated with the greatest improvements and found little significance for age, depression, and other patient characteristics.2

Our analysis is limited by selection bias associated with enrollment in the ASLS-1 study. All patients were evaluated by a surgeon and deemed candidates for surgery. Thus, those patients believed to have traits that would result in poor surgical outcomes were not included. For example, there is a paucity of patients with non–insulin-dependent diabetes mellitus in our cohort, despite the prevalence of this disease in the US. Statistical models did not account for clustering by study site as standardized protocols were followed across all study sites. However, some clustering of outcomes by study site may have remained. Also, the ASLS-1 study was not powered to determine factors associated with improvement or failure, thus these conclusions should be considered hypothesis-generating. To account for multiple comparisons, we have employed a strict definition for effect modifier and may miss relevant findings, such as BMI. The choice of using the MDMD rather than the MCID may be a noninferiority margin that is too lenient. However, MCID measures within-patient change and is not for comparisons between means, and we believed it an inappropriate choice for noninferiority.10 Finally, our analyses do not account for unanticipated revision surgeries beyond 2 years, which may affect PROs with longer follow-up. Despite these limitations, we believe that the strengths of the design and high rates of follow-up for both nonoperative and operative care offer data to assist in shared decision-making.

Conclusions

This exploratory study found the factors that were predictive of greater treatment effect favoring operative over nonoperative treatment were greater PI–LL mismatch, and worse symptoms and disability (especially ODI) at baseline. Male sex and greater BMI were not predictive of a worse outcome for the operatively treated patients. Factors that were not modifiers of treatment effect for operative care were mental health, socioeconomic class, smoking, larger Cobb angle, more preoperative back pain, and patient age. No evaluated subgroups were associated with a worsening of patient outcomes with operative treatment. Future studies investigating the effect of patient and surgical factors on PROs are required to confirm the findings of our analysis.

Acknowledgments

We would like to thank the following physicians for contributing work and/or patients to the study: Oheneba Boachie-Adjei, MD; Jacob M. Buchowski, MD; Leah Y. Carreon, MD, MSc; Charles H. Crawford III, MD; Charles Edwards II, MD; Thomas J. Errico, MD; Steven D. Glassman, MD; Munish C. Gupta, MD; Stephen J. Lewis, MD, MSc, FRCSC; Han Jo Kim, MD; Tyler Koski, MD; Stefan Parent, MD, PhD; Justin S. Smith, MD, PhD; and Lukas P. Zebala, MD. Funding was provided by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the US NIH from 2010 to 2017 (“A Multicenter NIH-Sponsored Prospective Study of Quality of Life in Adult Scoliosis [ASLS]”) by grant no. R01AR055176; and the Scoliosis Research Society from 2017 to the present.

Disclosures

Dr. Shaffrey reports being a consultant to Medtronic, NuVasvive, and SI Bone; having direct stock ownership in NuVasive; and being a patent holder for Medtronic, NuVasive, and Zimmer Biomet. Dr. Schwab reports being a consultant for K2 Medical LLC, Zimmer Biomet, and Globus Medical Inc,; receiving royalties from Medtronic Sofamor Danek, Zimmer Biomet, and Medicrea USA Corp.; receiving honoraria from Zimmer Biomet; and having ownership in the International Spine Study Group. Dr. Bess reports being a consultant to Stryker and Mirus; being a patent holder for K2M; receiving clinical or research support for this study from ISSGF; and receiving support of non–study-related clinical or research effort from ISSGF. Dr. Lenke reports being a paid consultant to, and receiving royalties from, Medtronic; receiving reimbursement for travel expenses from Broadwater, the Seattle Science Foundation, the Scoliosis Research Society, Stryker Spine, The Spinal Research Foundation, and AOSpine; receiving grant support from the Scoliosis Research Society, EOS, Setting Scoliosis Straight Foundation, and AOSpine; being an expert witness for Fox Rothschild LLC; receiving royalties from Quality Medical Publishing; receiving philanthropic research funding from a grateful patient/family from the Evans Family and the Fox Family Foundation; receiving fellowship support from AOSpine; and being a paid consultant to EOS Technologies and Acuity Surgical.

Author Contributions

Conception and design: all authors. Acquisition of data: Kelly, Yanik, Baldus, Shaffrey, Schwab, Bess, Lenke, LaBore, Bridwell. Analysis and interpretation of data: Kelly, Yanik, Lurie, Baldus, Bridwell. Drafting the article: Kelly, Bridwell. Critically revising the article: Kelly, Yanik, Lurie, Bridwell. Reviewed submitted version of manuscript: Yanik, Lurie, Baldus, Shaffrey, Schwab, Bess, Lenke, LaBore, Bridwell. Approved the final version of the manuscript on behalf of all authors: Kelly. Statistical analysis: Yanik, Baldus.

References

  • 1

    Altman DG, Bland JM: Interaction revisited: the difference between two estimates. BMJ 326:219, 2003

  • 2

    Ames CP, Smith JS, Pellisé F, Kelly MP, Gum JL, Alanay A, et al. : Development of deployable predictive models for minimal clinically important difference achievement across the commonly used health-related quality of life instruments in adult spinal deformity surgery. Spine (Phila Pa 1976) 44:11441153, 2019

    • Search Google Scholar
    • Export Citation
  • 3

    Ayhan S, Yuksel S, Nabiyev V, Adhikari P, Villa-Casademunt A, Pellise F, et al. : The influence of diagnosis, age, and gender on surgical outcomes in patients with adult spinal deformity. Global Spine J 8:803809, 2018

    • Search Google Scholar
    • Export Citation
  • 4

    Bakhsheshian J, Scheer JK, Gum JL, Hostin R, Lafage V, Bess S, et al. : Impact of poor mental health in adult spinal deformity patients with poor physical function: a retrospective analysis with a 2-year follow-up. J Neurosurg Spine 26:116124, 2017

    • Search Google Scholar
    • Export Citation
  • 5

    Bess S, Line B, Fu KM, McCarthy I, Lafage V, Schwab F, et al. : The health impact of symptomatic adult spinal deformity: comparison of deformity types to United States population norms and chronic diseases. Spine (Phila Pa 1976) 41:224233, 2016

    • Search Google Scholar
    • Export Citation
  • 6

    Bridwell KH, Cats-Baril W, Harrast J, Berven S, Glassman S, Farcy JP, et al. : The validity of the SRS-22 instrument in an adult spinal deformity population compared with the Oswestry and SF-12: a study of response distribution, concurrent validity, internal consistency, and reliability. Spine (Phila Pa 1976) 30:455461, 2005

    • Search Google Scholar
    • Export Citation
  • 7

    Bridwell KH, Glassman S, Horton W, Shaffrey C, Schwab F, Zebala LP, et al. : Does treatment (nonoperative and operative) improve the two-year quality of life in patients with adult symptomatic lumbar scoliosis: a prospective multicenter evidence-based medicine study. Spine (Phila Pa 1976) 34:21712178, 2009

    • Search Google Scholar
    • Export Citation
  • 8

    Bumpass DB, Lenke LG, Gum JL, Shaffrey CI, Smith JS, Ames CP, et al. : Male sex may not be associated with worse outcomes in primary all-posterior adult spinal deformity surgery: a multicenter analysis. Neurosurg Focus 43(6):E9, 2017

    • Search Google Scholar
    • Export Citation
  • 9

    Carreon LY, Glassman SD, Shaffrey CI, Fehlings MG, Dahl B, Ames CP, et al. : Predictors of health-related quality-of-life after complex adult spinal deformity surgery: a Scoli-RISK-1 secondary analysis. Spine Deform 5:139144, 2017

    • Search Google Scholar
    • Export Citation
  • 10

    Chung AS, Copay AG, Olmscheid N, Campbell D, Walker JB, Chutkan N: Minimum clinically important difference: current trends in the spine literature. Spine (Phila Pa 1976) 42:10961105, 2017

    • Search Google Scholar
    • Export Citation
  • 11

    Fairbank JC, Pynsent PB: The Oswestry Disability Index. Spine (Phila Pa 1976) 25:29402952, 2000

  • 12

    Fujishiro T, Boissière L, Cawley DT, Larrieu D, Gille O, Vital JM, et al. : Decision-making factors in the treatment of adult spinal deformity. Eur Spine J 27:23122321, 2018

    • Search Google Scholar
    • Export Citation
  • 13

    Keeney BJ, Koenig KM, Paddock NG, Moschetti WE, Sparks MB, Jevsevar DS: Do aggregate socioeconomic status factors predict outcomes for total knee arthroplasty in a rural population? J Arthroplasty 32:35833590, 2017

    • Search Google Scholar
    • Export Citation
  • 14

    Kelly MP, Kim HJ, Ames CP, Burton DC, Carreon LY, Polly DW Jr, et al. : Minimum detectable measurement difference for health-related quality of life measures varies with age and disability in adult spinal deformity: implications for calculating minimal clinically important difference. Spine (Phila Pa 1976) 43:E790E795, 2018

    • Search Google Scholar
    • Export Citation
  • 15

    Kelly MP, Lurie JD, Yanik EL, Shaffrey CI, Baldus CR, Boachie-Adjei O, et al. : Operative versus nonoperative treatment for adult symptomatic lumbar scoliosis. J Bone Joint Surg Am 101:338352, 2019

    • Search Google Scholar
    • Export Citation
  • 16

    Mmopelwa T, Ayhan S, Yuksel S, Nabiyev V, Niyazi A, Pellise F, et al. : Analysis of factors affecting baseline SF-36 mental component summary in adult spinal deformity and its impact on surgical outcomes. Acta Orthop Traumatol Turc 52:179184, 2018

    • Search Google Scholar
    • Export Citation
  • 17

    Smith JS, Shaffrey CI, Lafage V, Schwab F, Scheer JK, Protopsaltis T, et al. : Comparison of best versus worst clinical outcomes for adult spinal deformity surgery: a retrospective review of a prospectively collected, multicenter database with 2-year follow-up. J Neurosurg Spine 23:349359, 2015

    • Search Google Scholar
    • Export Citation
  • 18

    Strobl C, Malley J, Tutz G: An introduction to recursive partitioning: rationale, application, and characteristics of classification and regression trees, bagging, and random forests. Psychol Methods 14:323348, 2009

    • Search Google Scholar
    • Export Citation
  • 19

    Theologis AA, Ailon T, Scheer JK, Smith JS, Shaffrey CI, Bess S, et al. : Impact of preoperative depression on 2-year clinical outcomes following adult spinal deformity surgery: the importance of risk stratification based on type of psychological distress. J Neurosurg Spine 25:477485, 2016

    • Search Google Scholar
    • Export Citation
  • 20

    Verma R, Lafage R, Scheer J, Smith J, Passias P, Hostin R, et al. : Improvement in back and leg pain and disability following adult spinal deformity surgery: study of 324 patients with 2-year follow-up and the impact of surgery on patient-reported outcomes. Spine (Phila Pa 1976) 44:263269, 2019

    • Search Google Scholar
    • Export Citation
  • 21

    Waldrop LD II, King JJ III, Mayfield J, Farmer KW, Struk AM, Wright TW, et al. : The effect of lower socioeconomic status insurance on outcomes after primary shoulder arthroplasty. J Shoulder Elbow Surg 27 (6S):S35S42, 2018

    • Search Google Scholar
    • Export Citation

Image from van Bilsen et al. (pp 51–57).

Contributor Notes

Correspondence Michael P. Kelly: Washington University School of Medicine, St. Louis, MO. kellymi@wustl.edu.

INCLUDE WHEN CITING Published online March 6, 2020; DOI: 10.3171/2020.1.SPINE191288.

Disclosures Dr. Shaffrey reports being a consultant to Medtronic, NuVasvive, and SI Bone; having direct stock ownership in NuVasive; and being a patent holder for Medtronic, NuVasive, and Zimmer Biomet. Dr. Schwab reports being a consultant for K2 Medical LLC, Zimmer Biomet, and Globus Medical Inc,; receiving royalties from Medtronic Sofamor Danek, Zimmer Biomet, and Medicrea USA Corp.; receiving honoraria from Zimmer Biomet; and having ownership in the International Spine Study Group. Dr. Bess reports being a consultant to Stryker and Mirus; being a patent holder for K2M; receiving clinical or research support for this study from ISSGF; and receiving support of non–study-related clinical or research effort from ISSGF. Dr. Lenke reports being a paid consultant to, and receiving royalties from, Medtronic; receiving reimbursement for travel expenses from Broadwater, the Seattle Science Foundation, the Scoliosis Research Society, Stryker Spine, The Spinal Research Foundation, and AOSpine; receiving grant support from the Scoliosis Research Society, EOS, Setting Scoliosis Straight Foundation, and AOSpine; being an expert witness for Fox Rothschild LLC; receiving royalties from Quality Medical Publishing; receiving philanthropic research funding from a grateful patient/family from the Evans Family and the Fox Family Foundation; receiving fellowship support from AOSpine; and being a paid consultant to EOS Technologies and Acuity Surgical.

  • View in gallery

    Flow diagram of combined randomized and observational cohorts to 2-year follow-up. *Withdrawal counts include deaths. F/U = follow-up.

  • 1

    Altman DG, Bland JM: Interaction revisited: the difference between two estimates. BMJ 326:219, 2003

  • 2

    Ames CP, Smith JS, Pellisé F, Kelly MP, Gum JL, Alanay A, et al. : Development of deployable predictive models for minimal clinically important difference achievement across the commonly used health-related quality of life instruments in adult spinal deformity surgery. Spine (Phila Pa 1976) 44:11441153, 2019

    • Search Google Scholar
    • Export Citation
  • 3

    Ayhan S, Yuksel S, Nabiyev V, Adhikari P, Villa-Casademunt A, Pellise F, et al. : The influence of diagnosis, age, and gender on surgical outcomes in patients with adult spinal deformity. Global Spine J 8:803809, 2018

    • Search Google Scholar
    • Export Citation
  • 4

    Bakhsheshian J, Scheer JK, Gum JL, Hostin R, Lafage V, Bess S, et al. : Impact of poor mental health in adult spinal deformity patients with poor physical function: a retrospective analysis with a 2-year follow-up. J Neurosurg Spine 26:116124, 2017

    • Search Google Scholar
    • Export Citation
  • 5

    Bess S, Line B, Fu KM, McCarthy I, Lafage V, Schwab F, et al. : The health impact of symptomatic adult spinal deformity: comparison of deformity types to United States population norms and chronic diseases. Spine (Phila Pa 1976) 41:224233, 2016

    • Search Google Scholar
    • Export Citation
  • 6

    Bridwell KH, Cats-Baril W, Harrast J, Berven S, Glassman S, Farcy JP, et al. : The validity of the SRS-22 instrument in an adult spinal deformity population compared with the Oswestry and SF-12: a study of response distribution, concurrent validity, internal consistency, and reliability. Spine (Phila Pa 1976) 30:455461, 2005

    • Search Google Scholar
    • Export Citation
  • 7

    Bridwell KH, Glassman S, Horton W, Shaffrey C, Schwab F, Zebala LP, et al. : Does treatment (nonoperative and operative) improve the two-year quality of life in patients with adult symptomatic lumbar scoliosis: a prospective multicenter evidence-based medicine study. Spine (Phila Pa 1976) 34:21712178, 2009

    • Search Google Scholar
    • Export Citation
  • 8

    Bumpass DB, Lenke LG, Gum JL, Shaffrey CI, Smith JS, Ames CP, et al. : Male sex may not be associated with worse outcomes in primary all-posterior adult spinal deformity surgery: a multicenter analysis. Neurosurg Focus 43(6):E9, 2017

    • Search Google Scholar
    • Export Citation
  • 9

    Carreon LY, Glassman SD, Shaffrey CI, Fehlings MG, Dahl B, Ames CP, et al. : Predictors of health-related quality-of-life after complex adult spinal deformity surgery: a Scoli-RISK-1 secondary analysis. Spine Deform 5:139144, 2017

    • Search Google Scholar
    • Export Citation
  • 10

    Chung AS, Copay AG, Olmscheid N, Campbell D, Walker JB, Chutkan N: Minimum clinically important difference: current trends in the spine literature. Spine (Phila Pa 1976) 42:10961105, 2017

    • Search Google Scholar
    • Export Citation
  • 11

    Fairbank JC, Pynsent PB: The Oswestry Disability Index. Spine (Phila Pa 1976) 25:29402952, 2000

  • 12

    Fujishiro T, Boissière L, Cawley DT, Larrieu D, Gille O, Vital JM, et al. : Decision-making factors in the treatment of adult spinal deformity. Eur Spine J 27:23122321, 2018

    • Search Google Scholar
    • Export Citation
  • 13

    Keeney BJ, Koenig KM, Paddock NG, Moschetti WE, Sparks MB, Jevsevar DS: Do aggregate socioeconomic status factors predict outcomes for total knee arthroplasty in a rural population? J Arthroplasty 32:35833590, 2017

    • Search Google Scholar
    • Export Citation
  • 14

    Kelly MP, Kim HJ, Ames CP, Burton DC, Carreon LY, Polly DW Jr, et al. : Minimum detectable measurement difference for health-related quality of life measures varies with age and disability in adult spinal deformity: implications for calculating minimal clinically important difference. Spine (Phila Pa 1976) 43:E790E795, 2018

    • Search Google Scholar
    • Export Citation
  • 15

    Kelly MP, Lurie JD, Yanik EL, Shaffrey CI, Baldus CR, Boachie-Adjei O, et al. : Operative versus nonoperative treatment for adult symptomatic lumbar scoliosis. J Bone Joint Surg Am 101:338352, 2019

    • Search Google Scholar
    • Export Citation
  • 16

    Mmopelwa T, Ayhan S, Yuksel S, Nabiyev V, Niyazi A, Pellise F, et al. : Analysis of factors affecting baseline SF-36 mental component summary in adult spinal deformity and its impact on surgical outcomes. Acta Orthop Traumatol Turc 52:179184, 2018

    • Search Google Scholar
    • Export Citation
  • 17

    Smith JS, Shaffrey CI, Lafage V, Schwab F, Scheer JK, Protopsaltis T, et al. : Comparison of best versus worst clinical outcomes for adult spinal deformity surgery: a retrospective review of a prospectively collected, multicenter database with 2-year follow-up. J Neurosurg Spine 23:349359, 2015

    • Search Google Scholar
    • Export Citation
  • 18

    Strobl C, Malley J, Tutz G: An introduction to recursive partitioning: rationale, application, and characteristics of classification and regression trees, bagging, and random forests. Psychol Methods 14:323348, 2009

    • Search Google Scholar
    • Export Citation
  • 19

    Theologis AA, Ailon T, Scheer JK, Smith JS, Shaffrey CI, Bess S, et al. : Impact of preoperative depression on 2-year clinical outcomes following adult spinal deformity surgery: the importance of risk stratification based on type of psychological distress. J Neurosurg Spine 25:477485, 2016

    • Search Google Scholar
    • Export Citation
  • 20

    Verma R, Lafage R, Scheer J, Smith J, Passias P, Hostin R, et al. : Improvement in back and leg pain and disability following adult spinal deformity surgery: study of 324 patients with 2-year follow-up and the impact of surgery on patient-reported outcomes. Spine (Phila Pa 1976) 44:263269, 2019

    • Search Google Scholar
    • Export Citation
  • 21

    Waldrop LD II, King JJ III, Mayfield J, Farmer KW, Struk AM, Wright TW, et al. : The effect of lower socioeconomic status insurance on outcomes after primary shoulder arthroplasty. J Shoulder Elbow Surg 27 (6S):S35S42, 2018

    • Search Google Scholar
    • Export Citation

Metrics

All Time Past Year Past 30 Days
Abstract Views 291 210 0
Full Text Views 162 109 18
PDF Downloads 109 65 9
EPUB Downloads 0 0 0