Validation of a surgical invasiveness index in patients with lumbar spinal disorders registered in the Spine Tango registry

Introduction: Being able to quantify the invasiveness of a surgical procedure is important to weigh up its associated risks, since invasiveness governs the blood loss, operative time and likelihood of complications. Mirza et al. (Spine (Phila Pa 1976) 33:2651–2661, 2008) published an invasiveness index for spinal surgery. We evaluated the validity of a modified version of the Mirza invasiveness index (mMII), adapted for use with registry data. Methods: A cross-sectional analysis was performed with data acquired from the Spine Tango registry including 21,634 patients. The mMII was calculated as the sum of six possible interventions on each vertebral level: decompression, fusion and stabilization either on anterior or posterior structures. The association between the mMII and blood loss, operative time and complications was evaluated using multiple regression, adjusting for possible confounders. Results: The mean (± SD) mMII was 3.9 ± 5.0 (range 0–40). A 1-point increase in the mMII was associated with an additional blood loss of 12.8% (95% CI 12.6–13.0; p < 0.001) and an increase of operative time of 10.4 min (95% CI 10.20–10.53; p < 0.001). The R$^{2}$ for the blood loss model was of 43% and for operative time, 47%. The mean mMII was significantly (p < 0.001) higher in patients with surgical complications (4.5 ± 5.6) and general medical complications (6.5 ± 7.0) compared to those without (3.8 ± 4.9). Our results were comparable to those reported in the original publication of Mirza et al. Conclusion: The mMII appeared to be a valid measure of surgical invasiveness in our study population. It can be used in predictor models and to adjust for surgical case-mix when comparing outcomes in different studies or different hospitals/surgeons in a registry

Ratings of global outcome at the first post-operative assessment after spinal surgery: how often do the surgeon and patient agree?

Patient-orientated questionnaires are becoming increasingly popular in the assessment of outcome and are considered to provide a less biased assessment of the surgical result than traditional surgeon-based ratings. The present study sought to quantify the level of agreement between patients’ and doctors’ global outcome ratings after spine surgery. 1,113 German-speaking patients (59.0 ± 16.6 years; 643 F, 470 M) who had undergone spine surgery rated the global outcome of the operation 3 months later, using a 5-point scale: operation helped a lot, helped, helped only little, didn’t help, made things worse. They also rated pain, function, quality-of-life and disability, using the Core Outcome Measures Index (COMI), and their satisfaction with treatment (5-point scale). The surgeon completed a SSE Spine Tango Follow-up form, blind to the patient’s evaluation, rating the outcome with the McNab criteria as excellent, good, fair, and poor. The data were compared, in terms of (1) the correlation between surgeons’ and patients’ ratings and (2) the proportions of identical ratings, where the doctor’s “excellent” was considered equivalent to the patient’s “operation helped a lot”, “good” to “operation helped”, “fair” to “operation helped only little” and “poor” to “operation didn’t help/made things worse”. There was a significant correlation (Spearman Rho = 0.57, p < 0.0001) between the surgeons’ and patients’ ratings. Their ratings were identical in 51.2% of the cases; the surgeon gave better ratings than the patient (“overrated”) in 25.6% cases and worse ratings (“underrated”) in 23.2% cases. There were significant differences between the six surgeons in the degree to which their ratings matched those of the patients, with senior surgeons “overrating” significantly more often than junior surgeons (p < 0.001). “Overrating” was significantly more prevalent for patients with a poor self-rated outcome (measured as global outcome, COMI score, or satisfaction with treatment; each p < 0.001). In a multivariate model controlling for age and gender, “low satisfaction with treatment” and “being a senior surgeon” were the most significant unique predictors of surgeon “overrating” (p < 0.0001; adjusted R2 = 0.21). Factors with no unique significant influence included comorbidity (ASA score), first time versus repeat surgery, one-level versus multilevel surgery. In conclusion, approximately half of the patient’s perceptions of outcome after spine surgery were identical to those of the surgeon. Generally, where discrepancies arose, there was a tendency for the surgeon to be slightly more optimistic than the patient, and more so in relation to patients who themselves declared a poor outcome. This highlights the potential bias in outcome studies that rely solely on surgeon ratings of outcome and indicates the importance of collecting data from both the patient and the surgeon, in order to provide a balanced view of the outcome of spine surgery