Using a multivariate analysis on a prospectively collected data registry, a study (published in The Spine Journal) has found that elevated surgical invasiveness increases the risk of cardiovascular, pulmonary, neurologic, haematological and urological complications.
Although elevated surgical invasiveness would seem to be an obvious risk factor for post-surgical complications, it has been poorly evaluated in prior studies. Lead investigator Michael Lee, Department of Orthopaedics and Sports Medicine, University of Washington Medical Centre, Seattle, Washington, USA, and his fellow investigators reported that this was “largely because of the lack of a standard metric” However, they added that in their study they used a new classification system (The Surgical Invasiveness Index, Mirza et al) that uses a scoring system for each level of decompressed, fused, or instrumented anterior and posteriorly.
Lee et al found that in a univariate analysis, elevated surgical invasiveness (score 0–5) significantly increased the risk of complications in all six of the organ systems evaluated (cardiac, pulmonary, gastrointestinal, neurologic, haematological, and urological). Using a multivariate analysis, it was not found to be a significant risk factor for gastrointestinal complications but remained a significant risk factor for the other organ systems. In particular, elevated surgical invasiveness was associated with a 3.81 (p<0.0001) relative risk of neurologic complications.
Another important aspect of the design of the study, as well as the use of The Surgical Invasiveness Index, was that it evaluated data from a prospective, rather than retrospective, cohort study. Lee et al reported their study, to their knowledge, is the largest study using prospectively collected data (from 1,591 patients) to examine complications after cervical, thoracic, and lumbar spinal surgery. They wrote: “Although, there have been larger studies performed, they have been limited by the retrospective nature of data collection and inadequate analysis of all possible cofounding covariates.”
They found that increased age (≥65 years) was a significant risk factor for all of the organ systems evaluated both in the univariate and the multivariate analysis. Additionally, they found that patients with cardiac complications were 4.11 times more likely to die within the study period (at least two years) and patients with pulmonary complications were 10.76 times more likely to die in this timeframe than patients without these complications. As Lee et al report, that the presence of cardiac or pulmonary complications increases the risk of death is not surprising but they claim that the new study quantifies these risks with relative risk data and 95% confidence intervals. They wrote: “These data and statistical values can greatly equip providers and patients on decision making when considering surgical and non-surgical treatment options.”
Concluding their findings, Lee et al wrote: “The present study provides an exhaustive multivariate analysis of numerous risk factors for medical complications after spinal surgery.”
Lee told Spinal News Interational: “Enhanced understanding of complications and the safety of spinal surgery is of paramount importance to the clinician and patient when deciding if surgery is the optimal treatment. While relative risks and their confidence intervals are of great value, my ultimate goal is to create and validate a predictive model for complication after surgery so that each patient can individualise their own risk based on the presence or absence of an array of known risk factors.”