Predicting SF-6D utility scores from the neck disability index and numeric rating scales for neck and arm pain

Contemporary utilization of three-column osteotomy techniques in a prospective complex spinal deformity multicenter database: implications on full-body alignment and perioperative course

BACKGROUND

Research has focused on the increased correction from a three-column osteotomy (3CO) during adult spinal deformity (ASD) surgery. However, an in-depth analysis on the performance of a 3CO in a cohort of complex spinal deformity cases has not been described.

STUDY DESIGN/SETTING

This is a retrospective study on a prospectively enrolled, complex ASD database.

PURPOSE

This study aimed to determine if three-column osteotomies demonstrate superior benefit in correction of complex sagittal deformity at the cost of increased perioperative complications.

METHODS

Surgical complex adult spinal deformity patients were included and grouped into thoracolumbar 3COs compared to those who did not have a 3CO (No 3CO) (remaining cohort). Rigid deformity was defined as ΔLL less than 33% from standing to supine. Severe deformity was defined as global (SVA > 70 mm) or C7-PL > 70 mm, or lumbopelvic (PI-LL > 30°). Means comparison tests assessed correction by 3CO grade/location. Multivariate analysis controlling for baseline deformity evaluated outcomes up to six weeks compared to No 3CO.

RESULTS

648 patients were included (Mean age 61 ± 14.6 years, BMI 27.55 ± 5.8 kg/m2, levels fused: 12.6 ± 3.8). 126 underwent 3CO, a 20% higher usage than historical cohorts. 3COs were older, frail, and more likely to undergo revision (OR 5.2, 95% CI [2.6-10.6]; p < .001). 3COs were more likely to present with both severe global/lumbopelvic deformity (OR 4), 62.4% being rigid. 3COs had greater use of secondary rods (OR 4st) and incurred 4 times greater risk for: massive blood loss (> 3500 mL), longer LOS, SICU admission, perioperative wound and spine-related complications, and neurologic complications when performed below L3. 3COs had similar HRQL benefit, but higher perioperative opioid use. Mean segmental correction increased by grade (G3-21; G4-24; G5-27) and was 4 × greater than low-grade osteotomies, especially below L3 (OR 12). 3COs achieved 2 × greater spinopelvic correction. Higher grades properly distributed lordosis 50% of the time except L5. Pelvic compensation and non-response were relieved more often with increasing grade, with greater correction in all lower extremity parameters (p < .01). Due to the increased rate of complications, 3COs trended toward higher perioperative cost ($42,806 vs. $40,046, p = .086).

CONCLUSION

Three-column osteotomy usage in contemporary complex spinal deformities is generally limited to more disabled individuals undergoing the most severe sagittal and coronal realignment procedures. While there is an increased perioperative cost and prolongation of length of stay with usage, these techniques represent the most powerful realignment techniques available with a dramatic impact on normalization at operative levels and reciprocal changes.

Developing a risk score to inform the use of rhBMP-2 in adult spinal deformity surgery

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has not shown superior benefit overall in cost-effectiveness during adult spinal deformity (ASD) surgery.

STUDY DESIGN/SETTING

Retrospective PURPOSE: Generate a risk score for pseudarthrosis to inform the utilization of rhBMP-2, balancing costs against quality of life and complications.

METHODS

ASD patients with 3-year data were included. Quality of life gained was calculated from ODI to SF-6D and translated to quality-adjusted life years (QALYs). Cost was calculated using the PearlDiver database and CMS definitions for complications and comorbidities. Established weights were generated for predictive variables via logistic regression to yield a predictive risk score for pseudarthrosis that accounted for frailty, diabetes, depression, ASA grade, thoracolumbar kyphosis and three-column osteotomy use. Risk score categories, established via conditional inference tree (CIT)-derived thresholds were tested for cost-utility of rhBMP-2 usage, controlling for age, prior fusion, and baseline deformity and disability.

RESULTS

64% of ASD patients received rhBMP-2 (308/481). There were 17 (3.5%) patients that developed pseudarthrosis. rhBMP-2 use overall did not lower pseudarthrosis rates (OR: 0.5, [0.2-1.3]). Pseudarthrosis rates for each risk category were: No Risk (NoR) 0%; Low-Risk (LowR) 1.6%; Moderate Risk (ModR) 9.3%; High-Risk (HighR) 24.3%. Patients receiving rhBMP-2 had similar QALYs overall to those that did not (0.163 vs. 0.171, p = .65). rhBMP-2 usage had worse cost-utility in the LowR cohort (p < .001). In ModR patients, rhBMP-2 usage had equivocal cost-utility ($53,398 vs. $61,581, p = .232). In the HighR cohort, the cost-utility was reduced via rhBMP-2 usage ($98,328 vs. $211,091, p < .001).

CONCLUSION

Our study shows rhBMP-2 demonstrates effective cost-utility for individuals at high risk for developing pseudarthrosis. The generated score can aid spine surgeons in the assessment of risk and enhance justification for the strategic use of rhBMP-2 in the appropriate clinical contexts.

LEVEL OF EVIDENCE

III.

An Economic Analysis of Early and Late Complications After Adult Spinal Deformity Correction

STUDY DESIGN/SETTING

Retrospective cohort.

OBJECTIVE

Adult spinal deformity (ASD) corrective surgery is often a highly invasive procedure portending patients to both immediate and long-term complications. Therefore, we sought to compare the economic impact of certain complications before and after 2 years.

METHODS

ASD patients with minimum 3-year data included. Complication groups were defined as follows: any complication, major, medical, mechanical, radiographic, and reoperation. Complications stratified by occurrence before or after 2 years postoperatively. Published methods converted ODI to SF-6D to QALYs. Cost was calculated using CMS.gov definitions. Marginalized means for utility gained and cost-per-QALY were calculated via ANCOVA controlling for significant confounders.

RESULTS

244 patients included. Before 2Y, complication rates: 76% ≥1 complication, 18% major, 26% required reoperation. After 2Y, complication rates: 32% ≥1 complication, 4% major, 2.5% required reoperation. Major complications after 2 years had worse cost-utility (.320 vs .441, P = .1). Patients suffering mechanical complications accrued the highest overall cost ($130,482.22), followed by infection and PJF for complications before 2 years. Patients suffering a mechanical complication after 2 years had lower cost-utility ($109,197.71 vs $130,482.22, P = .041). Patients developing PJF after 2 years accrued a better cost-utility ($77,227.84 vs $96,873.57; P = .038), compared to PJF before 2 years.

CONCLUSION

Mechanical complications had the single greatest impact on cost-utility after adult spinal deformity surgery, but less so after 2 years. Understanding the cost-utility of specific interventions at certain timepoints may mitigate economic burden and prophylactic efforts should strategically be made against early mechanical complications.

Calculating ex-ante Utilities From the Neck Disability Index Score: Quantifying the Value of Care For Cervical Spine Pathology

STUDY DESIGN

General population utility valuation study.

OBJECTIVE

To develop a technique for calculating utilities from the Neck Disability Index (NDI) score.

METHODS

We recruited a sample of 1200 adults from a market research panel. Using an online discrete choice experiment (DCE), participants rated 10 choice sets based on NDI health states. A multi-attribute utility function was estimated using a mixed multinomial-logit regression model (MIXL). The sample was partitioned into a training set used for model fitting and validation set used for model evaluation.

RESULTS

The regression model demonstrated good predictive performance on the validation set with an AUC of .77 (95% CI: .76-.78). The regression model was used to develop a utility scoring rubric for the NDI. Regression results also revealed that participants did not regard all NDI items as equally important. The rank order of importance was (in decreasing order): pain intensity = work; personal care = headache; concentration = sleeping; driving; recreation; lifting; and lastly reading.

CONCLUSIONS

This study provides a simple technique for converting the NDI score to utilities and quantify the relative importance of individual NDI items. The ability to evaluate quality-adjusted life-years using these utilities for cervical spine pain and disability could facilitate economic analysis and aid in allocation of healthcare resources.

Are We Focused on the Wrong Early Postoperative Quality Metrics? Optimal Realignment Outweighs Perioperative Risk in Adult Spinal Deformity Surgery

BACKGROUND

While reimbursement is centered on 90-day outcomes, many patients may still achieve optimal, long-term outcomes following adult spinal deformity (ASD) surgery despite transient short-term complications.

OBJECTIVE

Compare long-term clinical success and cost-utility between patients achieving optimal realignment and suboptimally aligned peers.

STUDY DESIGN/SETTING

Retrospective cohort study of a prospectively collected multicenter database.

METHODS

ASD patients with two-year (2Y) data included. Groups were propensity score matched (PSM) for age, frailty, body mass index (BMI), Charlson Comorbidity Index (CCI), and baseline deformity. Optimal radiographic criteria are defined as meeting low deformity in all three (Scoliosis Research Society) SRS-Schwab parameters or being proportioned in Global Alignment and Proportionality (GAP). Cost-per-QALY was calculated for each time point. Multivariable logistic regression analysis and ANCOVA (analysis of covariance) adjusting for baseline disability and deformity (pelvic incidence (PI), pelvic incidence minus lumbar lordosis (PI-LL)) were used to determine the significance of surgical details, complications, clinical outcomes, and cost-utility.

RESULTS

A total of 930 patients were considered. Following PSM, 253 "optimal" (O) and 253 "not optimal" (NO) patients were assessed. The O group underwent more invasive procedures and had more levels fused. Analysis of complications by two years showed that the O group suffered less overall major (38% vs. 52%, p = 0.021) and major mechanical complications (12% vs. 22%, p = 0.002), and less reoperations (23% vs. 33%, p = 0.008). Adjusted analysis revealed O patients more often met MCID (minimal clinically important difference) in SF-36 PCS, SRS-22 Pain, and Appearance. Cost-utility-adjusted analysis determined that the O group generated better cost-utility by one year and maintained lower overall cost and costs per QALY (both p < 0.001) at two years.

CONCLUSIONS

Fewer late complications (mechanical and reoperations) are seen in optimally aligned patients, leading to better long-term cost-utility overall. Therefore, the current focus on avoiding short-term complications may be counterproductive, as achieving optimal surgical correction is critical for long-term success.

The Additional Economic Burden of Frailty in Adult Cervical Deformity Patients Undergoing Surgical Intervention

SUMMARY OF BACKGROUND DATA

The influence of frailty on economic burden following corrective surgery for the adult cervical deformity (CD) is understudied and may provide valuable insights for preoperative planning.

OBJECTIVE

To assess the influence of baseline frailty status on the economic burden of CD surgery.

STUDY DESIGN

Retrospective cohort.

MATERIALS AND METHODS

CD patients with frailty scores and baseline and two-year Neck Disability Index data were included. Frailty score was categorized patients by modified CD frailty index into not frail (NF) and frail (F). Analysis of covariance was used to estimate marginal means adjusting for age, sex, surgical approach, and baseline sacral slope, T1 slope minus cervical lordosis, C2-C7 angle, C2-C7 sagittal vertical axis. Costs were derived from PearlDiver registry data. Reimbursement consisted of a standardized estimate using regression analysis of Medicare payscales for services within a 30-day window including length of stay and death. This data is representative of the national average Medicare cost differentiated by complication/comorbidity outcome, surgical approach, and revision status. Cost per quality-adjusted life-year (QALY) at two years was calculated for NF and F patients.

RESULTS

There were 126 patients included. There were 68 NF patients and 58 classified as F. Frailty groups did not differ by overall complications, instance of distal junctional kyphosis, or reoperations (all P >0.05). These groups had similar rates of radiographic and clinical improvement by two years. NF and F had similar overall cost ($36,731.03 vs. $37,356.75, P =0.793), resulting in equivocal costs per QALYs for both patients at two years ($90,113.79 vs. $80,866.66, P =0.097).

CONCLUSION

F and NF patients experienced similar complication rates and upfront costs, with equivocal utility gained, leading to comparative cost-effectiveness with NF patients based on cost per QALYs at two years. Surgical correction for CD is an economical healthcare investment for F patients when accounting for anticipated utility gained and cost-effectiveness following the procedure.

LEVEL OF EVIDENCE

III.

Economics of Cervical Disc Replacement

BACKGROUND

Although extensive reports of clinical outcome after cervical disc replacement (CDR) and anterior cervical discectomy and fusion exist, few reviews of the cost-effectiveness research in cervical spine surgery exist. The purpose of this study was to review the concepts of cost-effectiveness research, the various approaches to cost-effectiveness studies in the context of cervical spine surgery, and some of the literature results.

METHODS

Review article describing cost-effectiveness research concepts, methodology, and results. The article reviews the concept of value, cost, utility, incremental cost-effectiveness ratio, and recent research.

RESULTS

Mixed data on cost-effectiveness of CDR compared with fusion exist. Notably, several studies performed within the last 5 years that use prospectively collected utility scores, costs, and adverse event calculations demonstrate a significant cost savings associated with CDR compared with fusion.

CONCLUSIONS

The recent literature confirms that, in properly selected patients, CDR is more effective and less costly over a 7-year time horizon for patients with symptomatic degenerative disc disease. The primary driver of the differential in cost effectiveness is the difference in secondary surgery rates.

LEVEL OF EVIDENCE

Level 5 CLINICAL RELEVANCE: In properly selected patients, CDR is more effective and less costly over a 7-year time horizon for patients with symptomatic degenerative disc disease.

A General Population Utility Valuation Study for Metastatic Epidural Spinal Cord Compression Health States

STUDY DESIGN

General population utility valuation study.

OBJECTIVE

This study obtained utility valuations from a Canadian general population perspective for 31 unique metastatic epidural spinal cord compression (MESCC) health states and determined the relative importance of MESCC-related consequences on quality-of-life.

SUMMARY OF BACKGROUND DATA

Few prospective studies on the treatment of MESCC have collected quality-adjusted-life-year weights (termed "utilities"). Utilities are an important summative measure which distills health outcomes to a single number that can assist healthcare providers, patients, and policy makers in decision making.

METHODS

We recruited a sample of 1138 adult Canadians using a market research company. Quota sampling was used to ensure that the participants were representative of the Canadian population in terms of age, sex, and province of residence. Using the validated MESCC module for the "Self-administered Online Assessment of Preferences" (SOAP) tool, participants were asked to rate six of the 31 MESCC health states, each of which presented varying severities of five MESCC-related dysfunctions (dependent; non-ambulatory; incontinent; pain; other symptoms).

RESULTS

Participants equally valued all MESCC-related dysfunctions which followed a pattern of diminishing marginal disutility (each additional consequence resulted in a smaller incremental decrease in utility than the previous). These results demonstrate that the general population values physical function equal to other facets of quality-of-life.

CONCLUSION

We provide a comprehensive set of ex ante utility estimates for MESCC health states that can be used to help inform decision making. This is the first study reporting direct utility valuation for a spinal disorder. Our methodology offers a feasible solution for obtaining quality-of-life data without collecting generic health status questionnaire responses from patients.

LEVEL OF EVIDENCE

4.

An Updated Systematic Review of Studies Mapping (or Cross-Walking) Measures of Health-Related Quality of Life to Generic Preference-Based Measures to Generate Utility Values

BACKGROUND

Mapping is an increasingly common method used to predict instrument-specific preference-based health-state utility values (HSUVs) from data obtained from another health-related quality of life (HRQoL) measure. There have been several methodological developments in this area since a previous review up to 2007.

OBJECTIVE

To provide an updated review of all mapping studies that map from HRQoL measures to target generic preference-based measures (EQ-5D measures, SF-6D, HUI measures, QWB, AQoL measures, 15D/16D/17D, CHU-9D) published from January 2007 to October 2018.

DATA SOURCES

A systematic review of English language articles using a variety of approaches: searching electronic and utilities databases, citation searching, targeted journal and website searches.

STUDY SELECTION

Full papers of studies that mapped from one health measure to a target preference-based measure using formal statistical regression techniques.

DATA EXTRACTION

Undertaken by four authors using predefined data fields including measures, data used, econometric models and assessment of predictive ability.

RESULTS

There were 180 papers with 233 mapping functions in total. Mapping functions were generated to obtain EQ-5D-3L/EQ-5D-5L-EQ-5D-Y (n = 147), SF-6D (n = 45), AQoL-4D/AQoL-8D (n = 12), HUI2/HUI3 (n = 13), 15D (n = 8) CHU-9D (n = 4) and QWB-SA (n = 4) HSUVs. A large number of different regression methods were used with ordinary least squares (OLS) still being the most common approach (used ≥ 75% times within each preference-based measure). The majority of studies assessed the predictive ability of the mapping functions using mean absolute or root mean squared errors (n = 192, 82%), but this was lower when considering errors across different categories of severity (n = 92, 39%) and plots of predictions (n = 120, 52%).

CONCLUSIONS

The last 10 years has seen a substantial increase in the number of mapping studies and some evidence of advancement in methods with consideration of models beyond OLS and greater reporting of predictive ability of mapping functions.

Cost-utility of revisions for cervical deformity correction warrants minimization of reoperations

Background

Cervical deformity (CD) surgery has become increasingly more common and complex, which has also led to reoperations for complications such as distal junctional kyphosis (DJK). Cost-utility analysis has yet to be used to analyze CD revision surgery in relation to the cost-utility of primary CD surgeries. The aim of this study was to determine the cost-utility of revision surgery for CD correction.

Methods

Retrospective review of a multicenter prospective CD database. CD was defined as at least one of the following: C2-C7 Cobb >10°, cervical lordosis (CL) >10°, cervical sagittal vertical axis (cSVA) >4 cm, chin-brow vertical angle (CBVA) >25°. Quality-adjusted life year (QALY) were calculated by EuroQol Five-Dimensions questionnaire (EQ-5D) and Neck Disability Index (NDI) mapped to SF-6D index and utilized a 3% discount rate to account for residual decline to life expectancy (men: 76.9 years, women: 81.6 years). Medicare reimbursement at 30 days assigned costs for index procedures (9+ level posterior fusion, 4-8 level posterior fusion with anterior fusion, 2-3 level posterior fusion with anterior fusion, 4-8 level anterior fusion) and revision fusions (2-3 level, 4-8 level, or 9+ level posterior refusion). Cost per QALY gained was calculated.

Results

Eighty-nine CD patients were included (61.6 years, 65.2% female). CD correction for these patients involved a mean 7.7±3.7 levels fused, with 34% combined approach surgeries, 49% posterior-only and 17% anterior-only, 19.1% three-column osteotomy. Costs for index surgeries ranged from $20,001-55,205, with the average cost for this cohort of $44,318 and cost per QALY of $27,267. Eleven revision surgeries (mean levels fused 10.3) occurred up to 1-year, with an average cost of $41,510. Indications for revisions were DJK (5/11), neurologic impairment [4], infection [1], prominent/painful instrumentation [1]. Average QALYs gained was 1.62 per revision patient. Cost was $28,138 per QALY for reoperations.

Conclusions

CD revisions had a cost of $28,138 per QALY, in addition to the $27,267 per QALY for primary CD surgeries. For primary CD patients, CD surgery has the potential to be cost effective, with the caveats that a patient livelihood extends long enough to have the benefits and durability of the surgery is maintained. Efforts in research and surgical technique development should emphasize minimization of reoperation causes just as DJK that significantly affect cost utility of these surgeries to bring cost-utility to an acceptable range.

Assessment of health-related quality of life in spine treatment: conversion from SF-36 to VR-12

BACKGROUND CONTEXT

Health-related quality-of-life outcomes have been collected with the Medical Outcomes Study (MOS) Short Form 36 (SF-36) survey. Boston University School of Public Health has developed algorithms for the conversion of SF-36 to Veterans RAND 12-Item Health Survey (VR-12) Physical Component Summary (PCS) and Mental Component Summary (MCS) scores.

PURPOSE

The purpose of the present study is to investigate the conversion of the SF-36 to VR-12 PCS and MCS scores.

STUDY DESIGN

Preoperative and postoperative SF-36 were collected from patients who underwent lumbar or cervical surgery from a single surgeon between August 1998 and January 2013.

METHODS

Short Form 36 PCS and MCS scores were calculated following their original instructions. The SF-36 answers were then converted to VR-12 PCS and MCS scores following the algorithm provided by the Boston University School of Public Health. The mean score, preoperative to postoperative change, and proportions of patients who reach the minimum detectable change were compared between SF-36 and VR-12.

RESULTS

A total of 1,968 patients (1,559 lumbar and 409 cervical) had completed preoperative and postoperative SF-36. The values of the SF-36 and VR-12 mean scores were extremely similar, with score differences ranging from 0.77 to 1.82. The preoperative to postoperative improvement was highly significant (p<.001) for both SF-36 and VR-12 scores. The mean change scores were similar, with a difference of up to 0.93 for PCS and up to 0.37 for MCS. Minimum detectable change (MDC) values were almost identical for SF-36 and VR-12, with a difference of 0.12 for PCS and up to 0.41 for MCS. The proportions of patients whose change in score reached MDC were also nearly identical for SF-36 and VR-12. About 90% of the patients above SF-36 MDC were also above VR-12 MDC.

CONCLUSIONS

The converted VR-12 scores, similar to the SF-36 scores, detect a significant postoperative improvement in PCS and MCS scores. The calculated MDC values and the proportions of patients whose score improvement reach MDC are similar for both SF-36 and VR-12.

Which Domains of the ODI Best Predict Change in Physical Function in Patients After Surgery for Degenerative Lumbar Spondylolisthesis?

STUDY DESIGN

A retrospective review.

OBJECTIVE

The purpose of this study is to determine the differential improvement of the various individual items of the Oswestry Disability Index (ODI) and to determine their relationship to other measures of Health Related Quality of Life (HRQOL).

SUMMARY OF BACKGROUND DATA

The ODI is an easily scored, common, 10-item questionnaire about symptoms relevant to lumbar spine pathology. It is not clear if all of the items can be reliably applied to spine surgery. The purpose of this study is to determine the differential improvement of the various individual items of the ODI and to determine their relationship to other measures of HRQOL.

METHODS

Analysis of a prospective registry of patients treated at an academic medical center was undertaken. At baseline, standardized outcome measures including ODI and SF12 PCS were collected on all patients undergoing elective fusion surgery for degenerative spondylolisthesis. Multiple linear regressions were performed using change in SF12 PCS as the dependent variable and change in ODI components as the independent variables.

RESULTS

Baseline and 1-year follow-up data were collected on 196 patients (mean age 60.4 years). There were statistically significant differences in improvement among ODI items. Surprisingly, the most improvement after surgery was noted in the standing, sex life, and social life domains. The least improvement was noted in the personal care, sleeping, and sitting domains. Linear regression for change in ODI components versus change in SF-12 PCS revealed a significant correlation (R = 0.353, P ≤ 0.001). The only retained domains in the final model were change in lifting, standing, and traveling as predictors for ΔPCS.

CONCLUSION

All domains of the ODI do not improve equally after surgery for degenerative spondylolisthesis. Some of the domains that improve most (e.g., sex life) have no discernible relationship to the known pathophysiology of degenerative spondylolisthesis. Based upon these results, we conclude that the item bank and composite scoring of the ODI are inappropriate for evaluating quality of life in studies of surgically treated degenerative spondylolisthesis patients.

LEVEL OF EVIDENCE

3.

Tapentadol extended release for the management of chronic neck pain

Background

The role of opioids in the management of chronic neck pain is still poorly investigated. No data are available on tapentadol extended release (ER). In this article, we present 54 patients with moderate-to-severe chronic neck pain treated with tapentadol ER.

Patients and methods

Patients received tapentadol ER 100 mg/day; dosage was then adjusted according to clinical needs. The following parameters were recorded: pain; Douleur Neuropathique 4 score; Neck Disability Index score; range of motion; pain-associated sleep interference; quality of life (Short Form [36] Health Survey); Patient Global Impression of Change (PGIC); Clinician GIC; opioid-related adverse effects; and need for other analgesics.

Results

A total of 44 of 54 patients completed the 12-week observation. Tapentadol ER daily doses increased from 100 mg/day to a mean (standard deviation) dosage of 204.5 (102.8) mg/day at the final evaluation. Mean pain intensity at movement significantly decreased from baseline (8.1 [1.1]) to all time points (P<0.01). At baseline, 70% of patients presented a positive neuropathic component. This percentage dropped to 23% after 12 weeks. Tapentadol improved Neck Disability Index scores from 55.6 (18.6) at baseline to 19.7 (20.9) at the final evaluation (P<0.01). Tapentadol significantly improved neck range of motion in all three planes of motion, particularly in lateral flexion. Quality of life significantly improved in all Short Form (36) Health Survey subscales (P<0.01) and in both physical and mental status (P<0.01). Based on PGIC results, approximately 90% of patients rated their overall condition as much/very much improved. Tapentadol was well tolerated: no patients discontinued due to side effects. The use of other analgesics was reduced during the observed period.

Conclusion

Our results suggest that tapentadol ER, started at 100 mg/day, is effective and well tolerated in patients with moderate-to-severe chronic neck pain, including opioid-naïve subjects. Patients can expect a decrease in pain, an improvement in neck function, and a decrease in neuropathic symptoms.

Impact of old age on patient-report outcomes and cost utility for anterior cervical discectomy and fusion surgery for degenerative spine disease

PURPOSE

With growing older population and increasing rates of cervical spinal surgery, it is vital to understand the value of cervical surgery in this population. We set forth to determine the cost utility following anterior cervical decompression and fusion (ACDF) for degenerative disease in older patients.

METHODS

Patients undergoing ACDF for degenerative diseases were enrolled into prospective longitudinal registry. Patient-reported outcomes (PROs) were recorded at baseline, 1-year, and 2-year postoperatively. Two-year medical resource utilization, missed work, and health-state values [quality-adjusted life years (QALYs)] were assessed to compute cost per QALY gained. Patients were dichotomized based on age: <65 years (younger) and ≥65 years (older) to compare the cost utility in these age groups.

RESULTS

Total 218 (87%) younger patients and 33 (13%) older patients who underwent ACDF were analyzed. Both the groups demonstrated a significant improvement in PROs 2-year following surgery. The older patients had a lower mean cumulative gain in QALYs compared to younger patients at 1 year (0.141 vs. 0.28, P = 0.05) and 2 years (0.211 vs. 0.424, P = 0.04). There was no significant difference in the mean total 2-year cost between older [$21,041 (95% CI $18,466-$23,616)] and younger [$22,669 (95% CI $$21,259-$24,079)] patients (P = 0.27). Two-year cost per QALY gained in older vs. younger patients was ($99,720/QALYs gained vs. ($53,464/QALYs gained, P = 0.68).

CONCLUSION

ACDF surgery provided a significant gain in health-state utility in older patients with degenerative cervical pathology, with a mean cumulative 2-year cost per QALY gained of $99,720/QALY. While older patients have a slightly higher cost utility compared to their younger counterparts, surgery in the older cohort does provide a significant improvement in pain, disability, and quality-of-life outcomes.

Comparing Utility Scores in Common Spinal Radiculopathies: Results of a Prospective Valuation Study

Study Design Prospective observational study. Objective To determine whether preference-based health utility scores for common spinal radiculopathies vary by specific spinal level. Methods We employed a standard gamble study using the general public to calculate individual preference-based quality of life for four common radiculopathies: C6, C7, L5, and S1. We compared utility scores obtained for each level of radiculopathy with analysis of variance and t test. Multivariable regression was used to test the effects of the covariates age, sex, and years of education. We also reviewed the literature for publications reporting EuroQol-5 Dimensions (EQ-5D) scores for patients with radiculopathy. Results Two hundred participants were included in the study. Average utility for the four spinal levels fell within a narrow range (0.748 to 0.796). There were no statistically significant differences between lumbar and cervical radiculopathies, nor were there significant differences among the different spinal levels (F = 0.0850, p = 0.086). Age and sex had no significant effect on utility scores. There was a significant correlation between years of education and utility values for S1 radiculopathy (p = 0.037). On review of the literature, no study separated utility values by specific spinal level. EQ-5D utilities for both cervical and lumbar radiculopathy were considerably lower than the results of our study. Conclusions Utility values associated with the most common levels of cervical and lumbar radiculopathy do not significantly differ from each other, validating the current practice of grouping utility by spinal segment rather than by specific root levels. The discrepancy in average utility values between our study and the EQ-5D highlights the need to be mindful of the underlying instruments used when assessing outcomes studies from different sources.

Mapping the neck disability index to SF-6D in patients with chronic neck pain

Background

This study sought to statistically map the neck disability index (NDI) to the six-dimension health state short form (SF-6D) to estimate algorithms for use in economic analyses in patients with chronic neck pain (CNP).

Methods

The relationships between NDI and SF-6D scores were estimated by using data from a cohort of patients with chronic neck pain (n = 272). By using ordinary least squares (OLS), generalized linear modeling (GLM), censored least absolute deviations (CLAD) and Tobit regression, scores from all 10 items of the NDI instruments were univariately tested against SF-6D values and retained in a multivariate regression model, if statistically significant. The predictive ability of the model was assessed by mean absolute error (MAE), root mean square error (RMSE) and normalized RMSE.

Results

The mean age of the 272 CNP patients was 39.9 ± 12.3 years; 57.8 % of the CNP patients were female. An OLS regression equation that included recreation item of NDI was optimal, with a MAE of 0.04and 0.04 and an RMSE of 0.06and 0.05in the derivation set and validation set, respectively. Predicted utilities accurately represented the observed ones.

Conclusions

We have provided algorithms for the estimation of health state utility values from the response of NDI. Future economic evaluations of the interventions for chronic neck pain could be informed by these algorithms.

Quality of Life and General Health After Elective Surgery for Cervical Spine Pathologies

BACKGROUND:

As part of the Affordable Care Act, health utility metrics are being investigated to define a cost-effective, value-based health care model. EuroQOL-5D (EQ-5D) and Short Form-6D (SF-6D) are commonly used quality-of-life instruments. Domains in the EQ-5D questionnaire are thought to be less responsive in measuring quality of life after cervical surgery.

OBJECTIVE:

To evaluate the validity and responsiveness of SF-6D and EQ-5D in determining health and quality of life after elective cervical spine surgery.

METHODS:

A total of 420 patients undergoing elective cervical spine surgery over a period of 2 years were enrolled in a prospective longitudinal registry. Patient-reported outcomes Neck Disability Index (NDI), EQ-5D, and SF-12 were recorded. Based on previously published equations, SF-6D was calculated using NDI and SF-12 scores. Patients were asked whether “surgery met their expectations” (meaningful improvement). The validity and relative responsiveness of SF-6D (NDI), SF-6D (SF-12), and EQ-5D to discriminate between meaningful and nonmeaningful improvement were calculated.

RESULTS:

Sixty-six percent of patients (277) reported a level of improvement after surgery that met their expectations (meaningful improvement). SF-6D (NDI) (area under the curve [AUC] = 0.69) was a more valid discriminator of meaningful improvement compared with the SF-6D (SF-12) (AUC = 0.65) and EQ-5D (AUC = 0.62). SF-6D (NDI) was also a more responsive measure compared with SF-6D (SF-12) and EQ-5D (standardized response mean difference: 0.66, 0.48, and 0.44, respectively).

CONCLUSION:

SF-6D is a more valid and responsive measure of general health and quality of life compared with EQ-5D. SF-6D derived from disease-specific disability scores was more valid and responsive than that derived from the generic preference-based SF-12. Cost-effective studies should use SF-6D as a measure of QALY after cervical spine surgery.

Estimating EQ-5D values from the Neck Disability Index and numeric rating scales for neck and arm pain

OBJECT

The Neck Disability Index (NDI) and numeric rating scales (0 to 10) for neck pain and arm pain are widely used cervical spine disease-specific measures. Recent studies have shown that there is a strong relationship between the SF-6D and the NDI such that using a simple linear regression allows for the estimation of an SF-6D value from the NDI alone. Due to ease of administration and scoring, the EQ-5D is increasingly being used as a measure of utility in the clinical setting. The purpose of this study is to determine if the EQ-5D values can be estimated from commonly available cervical spine disease-specific health-related quality of life measures, much like the SF-6D.

METHODS

The EQ-5D, NDI, neck pain score, and arm pain score were prospectively collected in 3732 patients who presented to the authors' clinic with degenerative cervical spine disorders. Correlation coefficients for paired observations from multiple time points between the NDI, neck pain and arm pain scores, and EQ-5D were determined. Regression models were built to estimate the EQ-5D values from the NDI, neck pain, and arm pain scores.

RESULTS

The mean age of the 3732 patients was 53.3 ± 12.2 years, and 43% were male. Correlations between the EQ-5D and the NDI, neck pain score, and arm pain score were statistically significant (p < 0.0001), with correlation coefficients of -0.77, -0.62, and -0.50, respectively. The regression equation 0.98947 + (-0.00705 × NDI) + (-0.00875 × arm pain score) + (-0.00877 × neck pain score) to predict EQ-5D had an R-square of 0.62 and a root mean square error (RMSE) of 0.146. The model using NDI alone had an R-square of 0.59 and a RMSE of 0.150. The model using the individual NDI items had an R-square of 0.46 and an RMSE of 0.172. The correlation coefficient between the observed and estimated EQ-5D scores was 0.79. There was no statistically significant difference between the actual EQ-5D score (0.603 ± 0.235) and the estimated EQ-5D score (0.603 ± 0.185) using the NDI, neck pain score, and arm pain score regression model. However, rounding off the coefficients to fewer than 5 decimal places produced less accurate results.

CONCLUSIONS

The regression model estimating the EQ-5D from the NDI, neck pain score, and arm pain score accounted for 60% of the variability of the EQ-5D with a relatively large RMSE. This regression model may not be sufficient to accurately or reliably estimate actual EQ-5D values.

Cost-utility analysis modeling at 2-year follow-up for cervical disc arthroplasty versus anterior cervical discectomy and fusion: A single-center contribution to the randomized controlled trial

BACKGROUND

Patients with cervical disc herniations resulting in radiculopathy or myelopathy from single level disease have traditionally been treated with Anterior Cervical Discectomy and Fusion (ACDF), yet Cervical Disc Arthroplasty (CDA) is a new alternative. Expert suggestion of reduced adjacent segment degeneration is a promising future result of CDA. A cost-utility analysis of these procedures with long-term follow-up has not been previously reported.

METHODS

We reviewed single institution prospective data from a randomized trial comparing single-level ACDF and CDA in cervical disc disease. Both Medicare reimbursement schedules and actual hospital cost data for peri-operative care were separately reviewed and analyzed to estimate the cost of treatment of each patient. QALYs were calculated at 1 and 2 years based on NDI and SF-36 outcome scores, and incremental cost effectiveness ratio (ICER) analysis was performed to determine relative cost-effectiveness.

RESULTS

Patients of both groups showed improvement in NDI and SF-36 outcome scores. Medicare reimbursement rates to the hospital were $11,747 and $10,015 for ACDF and CDA, respectively; these figures rose to $16,162 and $13,171 when including physician and anesthesiologist reimbursement. The estimated actual cost to the hospital of ACDF averaged $16,108, while CDA averaged $16,004 (p = 0.97); when including estimated physicians fees, total hospital costs came to $19,811 and $18,440, respectively. The cost/QALY analyses therefore varied widely with these discrepancies in cost values. The ICERs of ACDF vs CDA with Medicare reimbursements were $18,593 (NDI) and $19,940 (SF-36), while ICERs based on actual total hospital cost were $13,710 (NDI) and $9,140 (SF-36).

CONCLUSIONS

We confirm the efficacy of ACDF and CDA in the treatment of cervical disc disease, as our results suggest similar clinical outcomes at one and two year follow-up. The ICER suggests that the non-significant added benefit via ACDF comes at a reasonable cost, whether we use actual hospital costs or Medicare reimbursement values, though the actual ICER values vary widely depending upon the CUA modality used. Long term follow-up may illustrate a different profile for CDA due to reduced cost and greater long-term utility scores. It is crucial to note that financial modeling plays an important role in how economic treatment dominance is portrayed.

Towards an expanded definition of value

Much of the change being sought in the United State's health-care system is predicated on improving value. Value is most simply defined as quality divided by cost, and physicians increasingly rely on the quality-adjusted life year as the numerical measure to justify their services. However, there are many other definitions of value being advocated by various stakeholders in the health-care reform effort. Incentive programs and pilot studies implemented by private and public payers are steering much of the current change. Expanding our understanding of how value is defined by health-care economists and policy makers can help spine providers navigate the evolving health-care landscape.

Surgically treated cervical myelopathy: a functional outcome comparison study between multilevel anterior cervical decompression fusion with instrumentation and posterior laminoplasty

BACKGROUND CONTEXT

Multilevel cervical myelopathy can be treated with anterior cervical discectomy and fusion (ACDF) or corpectomy via the anterior approach and laminoplasty via the posterior approach. Till date, there is no proven superior approach.

PURPOSE

To elucidate any potential advantage of one approach over the other with regard to clinical midterm outcomes in this study.

STUDY DESIGN

A prospective, 2-year follow-up of patients with cervical myelopathy treated with multilevel anterior cervical decompression fusion and plating and posterior laminoplasty.

PATIENT SAMPLE

In total, 116 patients were studied. Sixty-four patients underwent ACDF two levels and above or anterior cervical corpectomy and fusion one level and above. Fifty-two patients underwent posterior cervical surgery (laminoplasty C3-C6 and C3-C7).

OUTCOME MEASURES

Self-report measures: Japan Orthopedic Association (JOA) score, JOA recovery rate, visual analog scale for neck pain (VASNP), neck disability index (NDI), and American Academy of Orthopaedic Surgeons (AAOS) neurogenic symptom score (AAOS-NSS). Physiologic measures: range of motion (ROM) flexion and extension of neck. Functional measures: short-form 36 (SF-36) score comprising physical functioning, physical role function, bodily pain, general health, vitality, social role function, emotional role function, and mental health scales.

METHODS

Comparison of the JOA scores, JOA recovery rates, NDI scores, SF-36 scores, VASNP, and ROM preoperatively to 2 years. Chi-square and two-sided Student t tests were used to analyze the variables.

RESULTS

Posterior surgery took an hour shorter (p<.05) and had better improvement in JOA scores at early follow-up of 6 months (p=.025). Anterior surgery group had better improvement of NDI scores at early follow-up of 6 months (p=.024) and was associated with less blood loss intraoperatively compared with posterior surgery. There was no statistical difference between the two groups for JOA scores, JOA recovery rates, SF-36 quality-of-life scores, NDI, AAOS-NSS, VAS neck pain, and ROM at 2 years. Complications were higher for anterior surgery group: two hematoma postoperation, one vocal cord paresis, and one new onset C6/C7 dermatome numbness versus one dura leak in posterior surgery group.

CONCLUSIONS

Our study showed that patients with multilevel disease treated with laminoplasty do well and compare favorably with patients treated with an anterior approach. Notably, posterior surgery was associated with shorter operating time, better improvement in JOA scores at 6 months, and a tendency toward lesser complications. Posterior surgery was not associated with increased neck disability and neck pain at 2 years. Anterior surgery had better NDI improvement at early follow-up. There is a need for a larger study that is prospectively randomized with long-term follow-up before we can confidently advocate one approach over the other in the management of cervical myelopathy.

Cost-effectiveness of single-level anterior cervical discectomy and fusion five years after surgery

STUDY DESIGN

Longitudinal cohort. OBJECTIVE.: The purpose of this study is to determine the cost per quality-adjusted life year (cost/QALY) gained for single-level instrumented anterior cervical discectomy and fusion (ACDF) over 5 years.

SUMMARY OF BACKGROUND DATA

Economic value is an increasingly important component of health care policy decision making.

METHODS

Control patients who had undergone ACDF with complete 5-year follow-up data who were part of the Investigational Device Exemption trials for cervical disc arthroplasty were identified. Direct costs for each intervention reported as part of the trial were determined using the 2012 Medicare Fee schedule. Health utility was determined using the Short Form-6D, calculated by transformation from the Short Form-36.

RESULTS

There were 352 patients (182 women, 170 men), mean age was 44.6 years (22-73 yr). Cost per patient for the index ACDF was $15,714. Over 5 years, 41 repeat ACDFs, 15 posterior fusions, 6 foraminotomies, 2 implant removals, 2 hematoma evacuations, and 1 esophageal fistula repair were performed. Mean QALY gained in each year of follow-up was 0.16, 0.18, 0.17, 0.18, and 0.18 for a cumulative 0.88 QALY gain over 5 years. The resultant cost/QALY gain at 1 year was $104,831; $53,074 at year 2; $37,717 at year 3; $28,383 at year 4; and $23,460 at year 5. In this cohort, 11 nerve releases and 26 rotator cuff repairs were done within 5 years after the index ACDF. Subanalysis to include upper extremity procedures was performed. The cost/QALY gained at 1 year including upper extremity procedures was $106,256; $54,622 at year 2; $38,836 at year 3; $29,454 at year 4; and $24,479 at year 5.

CONCLUSION

Increasing health care costs call for demonstration of cost-effectiveness in order to justify payment for interventions, including ACDFs. This study indicates that at 5-year follow-up, single-level instrumented ACDF is both effective and durable resulting in a favorable cost/QALY gained as compared to other widely accepted health care interventions.

The development of a model for translation of the Neck Disability Index to utility scores for cost-utility analysis in cervical disorders

BACKGROUND CONTEXT

The Neck Disability Index (NDI) is a commonly used disease-specific instrument for cervical spine disorders with good responsiveness and psychometric properties compared with general health status measures. However, NDI scores are unitless and do not have an intrinsic value that is comparable to other health status measures, and these scores have limited value in cost-utility analysis. The translation of disease-specific measures to Short Form-6 Dimensions (SF-6D) utility scores may be useful in cost-utility analysis.

PURPOSE

The purpose of this study is to present a model for translating the NDI to SF-6D utility scores, permitting the use of NDI scores in the cost-utility analysis of cervical disorders.

STUDY DESIGN/SETTING

A secondary analysis of a multicenter prospective clinical trial of the Synthes ProDisc-C (Synthes, West Chester, PA, USA) was performed.

PATIENT SAMPLE

Patients included were randomized to receive either a total disc arthroplasty or anterior cervical discectomy and fusion for treatment of symptomatic cervical disc disease involving one vertebral level between C3 and C7. All subjects completed NDI and 36-Item Short Form Health Survey (SF-36) self-assessments at preoperative and postoperative follow-ups of 6 weeks, 3, 6, 12, 18, and 24 months.

OUTCOME MEASURES

The NDI is a validated and widely used self-reported questionnaire designed to assess patient-determined disability resulting from neck pain, including pain level and effects on activities of daily living. The SF-6D is a preference-based health state classification system derived from six health dimensions of the SF-36 self-reported questionnaire, including the domains of physical functioning, role limitation, social functioning, bodily pain, mental health, and vitality.

METHODS

The collected data points were divided into two cohorts: one for model formation and one for the assessment of model validity. SF-36 scores were converted to SF-6D utilities via three previously published methods. Correlation analyses and linear regression modeling between SF-6D and NDI created the models for translating scores. For validation, Spearman and Pearson correlations were calculated between the observed and predicted SF-6D utilities, and prediction errors were calculated.

RESULTS

Four hundred thirty patients with 2,137 time points were used for creation and validation of the model. Pearson and Spearman correlation coefficients between the NDI and the SF-6D derived from each conversion method were found to be between -0.8255 and -0.8504 (p<.01). R(2) values ranged from 0.68 to 0.71 and root mean squared error (RMSE) from 0.092 to 0.084. Correlations between estimated and observed SF-6D scores ranged from 0.8325 to 0.8372 (p<.01). The mean prediction error was less than 0.006, with standard deviation (SD) between 0.082 and 0.093.

DISCUSSION

Correlations between NDI and SF-6D utility scores are strong and statistically significant. The model has a large R(2) and small RMSE. The prediction models produce a small mean prediction error, but the SD of the prediction errors is large. High correlations between NDI and SF-6D permit these models to be used to calculate overall utilities, changes in utilities, and quality-adjusted life-years for large data samples. However, the relatively large observed prediction error SDs may limit the accuracy of translation of individual data points or small sample sizes.

Reflecting on whiplash associated disorder through a QoL lens: an option to advance practice and research

PURPOSE

To examine the constructs of quality of life (QoL) as applied to whiplash associated disorder (WAD), its current state of measurement and suggestions for future application.

METHOD

Narrative literature review.

RESULTS

The burden of WAD on the healthcare system is substantive. Assessment of QoL issues for people with WAD may provide a broader understanding of the patient experience. No consistent framework for QoL in WAD has been adopted, nor has preference for any QoL instrument been established. Inconsistent use of terminology for what is being measured, and the measures themselves hamper clarity on the issue. Options for assessing QoL currently include a meaningful condition-specific scale that has not undergone sufficient psychometric evaluation (Whiplash Disability Questionnaire (WDQ), or generic scales with strong psychometric properties that have not undergone sufficient relevancy evaluation (e.g. SF-36, WHOQOL BREF). Generic measures can measure overlapping constructs including heath status, utility, health-related quality of life or generic QoL. The inter-relationships between these in WAD have not been defined.

CONCLUSIONS

Given the impact of WAD on QoL, additional clarity on tools and approaches are needed. There is a need for research on the relevance and clinical measurement properties of available condition-specific and generic tools to define a preferred measurement approach in WAD.