Development of a mapping function ("crosswalk") for the conversion of scores between the Oswestry Disability Index (ODI) and the Core Outcome Measures Index (COMI).

INTRODUCTION: The Oswestry Disability Index (ODI) and the Core Outcome Measures Index (COMI) are two commonly used self-rating outcome instruments in patients with lumbar spinal disorders. No formal crosswalk between them exists that would otherwise allow the scores of one to be interpreted in terms of the other. We aimed to create such a mapping function. METHODS: We performed a secondary analysis of ODI and COMI data previously collected from 3324 patients (57 ± 17y; 60.3% female) at baseline and 1y after surgical or conservative treatment. Correlations between scores and Cohen's kappa for agreement (κ) regarding achievement of the minimal clinically important change (MCIC) score on each instrument (ODI, 12.8 points; COMI, 2.2 points) were calculated, and regression models were built. The latter were tested for accuracy in an independent set of registry data from 634 patients (60 ± 15y; 56.8% female). RESULTS: All pairs of measures were significantly positively correlated (baseline, 0.73; 1y follow-up (FU), 0.84; change-scores, 0.73). MCIC for COMI was achieved in 53.9% patients and for ODI, in 52.4%, with 78% agreement on an individual basis (κ = 0.56). Standard errors for the regression slopes and intercepts were low, indicating excellent prediction at the group level, but root mean square residuals (reflecting individual error) were relatively high. ODI was predicted as COMI × 7.13-4.20 (at baseline), COMI × 6.34 + 2.67 (at FU) and COMI × 5.18 + 1.92 (for change-score); COMI was predicted as ODI × 0.075 + 3.64 (baseline), ODI × 0.113 + 0.96 (FU), and ODI × 0.102 + 1.10 (change-score). ICCs were 0.63-0.87 for derived versus actual scores. CONCLUSION: Predictions at the group level were very good and met standards justifying the pooling of data. However, we caution against using individual values for treatment decisions, e.g. attempting to monitor patients over time, first with one instrument and then with the other, due to the lower statistical precision at the individual level. The ability to convert scores via the developed mapping function should open up more centres/registries for collaboration and facilitate the combining of data in meta-analyses.

What level of symptoms are patients with adult spinal deformity prepared to live with? A cross-sectional analysis of the 12-month follow-up data from 1043 patients.

INTRODUCTION: Previous studies suggest that a meaningful and easily understood measure of treatment outcome may be the proportion of patients who are in a "patient acceptable symptom state" (PASS). We sought to quantify the score equivalent to PASS for different outcome instruments, in patients with adult spinal deformity (ASD). METHODS: We analysed the following 12-month questionnaire data from the European Spine Study Group (ESSG): Oswestry Disability Index (ODI; 0-100); Numeric Rating Scales (NRS; 0-10) for back/leg pain; Scoliosis Research Society (SRS) questionnaire; and an item "if you had to spend the rest of your life with the symptoms you have now, how would you feel about it?" (5-point scale, dichotomised with top 2 responses "somewhat satisfied/very satisfied" being considered PASS+, everything else PASS-). Receiver operating characteristics (ROC) analyses indicated the cut-off scores equivalent to PASS+. RESULTS: Out of 1043 patients (599 operative, 444 non-operative; 51 ± 19 years; 84% women), 42% reported being PASS+ at 12 months' follow-up. The ROC areas under the curve were 0.71-0.84 (highest for SRS subscore), suggesting the questionnaire scores discriminated well between PASS+ and PASS-. The scores corresponding to PASS+ were > 3.5 for the SRS subscore (> 3.3-3.8 for SRS subdomains); ≤ 18 for ODI; and ≤ 3 for NRS pain. There were slight differences in cut-offs for subgroups of age, treatment type, aetiology, baseline symptoms, and sex. CONCLUSION: Most interventions for ASD improve patients' complaints but do not totally eliminate them. Reporting the percentage achieving a score equivalent to an "acceptable state" may represent a more stringent and discerning target for denoting treatment success in ASD. These slides can be retrieved under Electronic Supplementary Material.

Factor analysis of the SRS-22 outcome assessment instrument in patients with adult spinal deformity.

PURPOSE: Designed for patients with adolescent idiopathic scoliosis, the SRS-22 is now widely used as an outcome instrument in patients with adult spinal deformity (ASD). No studies have confirmed the four-factor structure (pain, function, self-image, mental health) of the SRS-22 in ASD and under different contexts. Factorial invariance of an instrument over time and in different languages is essential to allow for precise interpretations of treatment success and comparisons across studies. This study sought to evaluate the invariance of the SRS-22 structure across different languages and sub-groups of ASD patients. METHODS: Confirmatory factor analysis was performed on the 20 non-management items of the SRS-22 with data from 245 American English-, 428 Spanish-, 229 Turkish-, 95 French-, and 195 German-speaking patients. Item loading invariance was compared across languages, age groups, etiologies, treatment groups, and assessment times. A separate sample of SRS-22 data from 772 American surgical patients with ASD was used for cross-validation. RESULTS: The factor structure fitted significantly better to the proposed four-factor solution than to a unifactorial solution. However, items 14 (personal relationships), 15 (financial difficulties), and 17 (days off work) consistently showed weak item loading within their factors across all language versions and in both baseline and follow-up datasets. A trimmed SRS (16 non-management items) that used the four least problematic items in each of the four domains yielded better-fitting models across all languages, but equivalence was still not reached. With this shorter version there was equivalence of item loading with respect to treatment (surgery vs conservative), time of assessment (baseline vs 12 months follow-up), and etiology (degenerative vs idiopathic), but not age (< vs ≥50 years). All findings were confirmed in the cross-validation sample. CONCLUSION: We recommend removal of the worst-fitting items from each of the four domains of the SRS-instrument (items 3, 14, 15, 17), together with adaptation and standardization of other items across language versions, to provide an improved version of the instrument with just 16 non-management items.

The Core Outcome Measures Index (COMI) is a responsive instrument for assessing the outcome of treatment for adult spinal deformity.

INTRODUCTION: The Core Outcome Measures Index for the back (COMI-back) is a very brief instrument for assessing the main outcomes of importance to patients with back problems (pain, function, symptom-specific well-being, quality of life, disability). However, it might be expected to be less responsive than a disease-specific instrument when evaluating specific pathologies. In patients with adult spinal deformity, we compared the performance of COMI-back with the widely accepted SRS-22 questionnaire. METHODS: At baseline and 12 months after non-operative (N = 121) and surgical (N = 83) treatment, patients (175 F, 29 M) completed the following: COMI-back, SRS-22, Oswestry Disability Index (ODI) and SF-36 PCS. At 12 months' follow-up, patients also indicated on a 15-point Global Rating of Change Scale (GRCS) how their back problem had changed relative to 1 year ago. Construct validity for the COMI-back was assessed by the correlation between its scores and those of the comparator instruments; responsiveness was assessed with receiver operating characteristics (ROC) analysis of COMI-back change scores versus the criterion 'treatment success' (dichotomized GRCS). RESULTS: Baseline values for the COMI-back showed significant (p < 0.0001) correlations with SRS-22 (r = -0.85), ODI (r = 0.83), and SF-36 PCS (r = -0.82) scores; significantly worse scores for all measures were recorded in the surgical group. The correlation between the change scores (baseline to 12 months) for COMI and SRS-22 was 0.74, and between each of these change scores and the external criterion of treatment success were: COMI-back, r = 0.58; SRS-22, r = -0.58 (each p < 0.0001). The ROC areas under the curve for the COMI-back and SRS-22 change scores were 0.79 and 0.82, respectively. CONCLUSION: Both baseline and change scores for the COMI-back correlated strongly with those of the SRS-22, and differed significantly in surgical and non-operative patients, suggesting good construct validity. With the "change in the back problem" serving as external criterion, COMI-back showed similar external responsiveness to SRS-22. The COMI-back was well able to detect important change. Coupled with its brevity, which minimizes patient burden, these favourable psychometric properties suggest the COMI-back is a suitable instrument for use in registries and can serve as a valid instrument in clinical studies emerging from such data pools.

Late surgery for spinal deformities in children previously treated for neural tumors.

BACKGROUND/AIM: Surgery for neural tumors occasionally involves opening of the neural canal and/or costovertebral resection that may be followed by radiotherapy. Spinal deformities (SD) may occur in these cases. This study investigated the incidence, surgical indications and results of repair of late SD in a large series of patients with neural tumors. METHODS: A retrospective review of neural tumors treated between 1991 and 2009 at our institution identified children with SD who subsequently required spinal surgery. SD was meaÂ-sured using Cobb's angle. Instrumentation of the spine was indicated in patients with a Cobb's angle of more than 60° or rapidly progressing SD. The operation was adapted to the location, type and degree of SD. Patients were followed up and the remaining deviations were measured annually. RESULTS: Out of a series of 188 patients with neural tumors, 5 of 173 patients with neuroblastomas/ganglioneuromas (NB/GN) and 3 of 15 patients with PNET/Askin tumors developed SD over time. NB/GN children had intraspinal tumors requiring laminotomy (n=3) or laminectomy (n=2). PNET/Askin tumor patients had undergone largescale rib and partial vertebral body resection and radiotherapy. Scoliosis or kyphosis were located in the thoracic spine in 4, in the thoracolumbar spine in 3 and in the cervicothoracic spine in 1. The median preoperative Cobb's angle was 65° (50°-90°) prior to spinal surgery performed 2.9 (0.4-11) years after tumor removal. 3 growth bars, 2 vertical expandable prosthetic titanium ribs, 1 pediatric ISOLA device and anterior instrumentation were used. Arthrodesis was necessary in 3 patients. Median post-instrumentation deformity after 3.1 (0.2-12.2) years was 40° (20°-50°), giving an improvement of 38.4%. CONCLUSIONS: With increasing numbers of children surviving cancer, attention must focus on sequelae. A sizeable number of survivors of NB/GN and PNET/Askin tumors develop serious SD requiring surgical correction. Pediatric surgeons, patients and relatives must be aware of these possible sequelae.

The low lumbar spine below Cotrel-Dubousset instrumentation: long-term findings.

STUDY DESIGN: Retrospective review of long instrumented fusions down to the low lumbar spine for the treatment of adolescent idiopathic scoliosis. OBJECTIVES: To evaluate whether the use of instrumentation systems that preserve the sagittal profile could reduce the incidence of early degenerative changes. SUMMARY OF BACKGROUND DATA: Long fusions and distractive Harrington instrumentation in the surgical treatment of adolescent idiopathic scoliosis (AIS) are known to produce pain and degenerative changes in the free lumbar segments. Reports on the use of Cotrel-Dubousett instrumentation (CDI) confirm that the instrumentation maintains physiologic lumbar lordosis, but the evolution of the spine below the fusion is not addressed. METHOD: Thirty-five patients with AIS and CDI were studied. Their spines were fused to L3 or lower, and they had a minimum follow-up of 10 years. Radiologic measurements were recorded from frontal and lateral radiographs. At the time of last examination, lateral flexion-extension dynamic radiographs and magnetic resonance imaging evaluated the health of the disks below the fusion. Clinical outcome was assessed with the Scoliosis Research Society instrument. A control group consisting of 35 peers without scoliosis served as a reference for the outcome questionnaire. RESULTS: Surgery kept the sagittal profile in a physiologic range. All but two patients were satisfied with the results of surgery. There were no differences between patients and control group insofar as pain, self-image, general function, and daily activity were concerned. Eleven patients showed instability signs in dynamic radiographs and more than half of patients showed incipient degeneration on magnetic resonance images. These findings are similar to those found in the general population, according to the literature, and could evidence normal aging processes. CONCLUSIONS: Cotrel-Dubousset instrumentation maintains the physiologic sagittal contour. Although there are some degenerative changes in magnetic resonance images and dynamic radiographs, the quality of life and daily activities of the patients after surgery are similar to those of a normal population of the same age.