Comorbidities and surgical complication linked to increased readmission after revision lumbar fusion

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Thomas C Hydrick

Relevant patient comorbidities and surgical complications are associated with increased readmission within 90 days of elective revision lumbar fusion surgery, a retrospective study published in the Global Spine Journal has found. Readmission within 90 days is also linked to significant increases in hospital costs, the team behind the study concluded.

The review of data from the US Nationwide Readmissions Database, authored by Thomas C Hydrick (Mayo Clinic Alix School of Medicine, Scottsdale, USA) and colleagues, sought to determine the total incidence and rate of readmission within 90 days after elective revision of lumbar fusion. The study also aimed to identify risk factors associated with readmission, and to evaluate the cost associated with these readmissions within a 90-day window of care.

Compared with primary lumbar fusion surgery, revision lumbar fusion has been associated with increased complications and morbidity, Hydrick and colleagues note, adding that additional studies have borne out the increased risk of complications, such as site infections, in comparison to primary procedures.

The study team used 2014 data from the US Nationwide Readmissions Database (NRD)—an aggregate of inpatient databases from 27 states, estimated to represent 56.8% of all hospitalisations in the US—to identify patients undergoing elective revision lumbar fusion. The NRD allows the tracking of patients, and their subsequent readmissions within the same year and the same state as their index admission. However, this meant that patients who were readmitted in a different state, or different year than their index admission, were not recorded as a readmission within the study.

All patients within the NRD undergoing revision lumbar fusion were identified using International Classification of Diseases, ninth revision, clinical modification (ICD-9-CM) procedure codes. Patients younger than 18 years; those who died during initial admission; or were non-elective admissions, were excluded from the study.

The patient characteristics for both groups were analysed with a student’s t-test and χ2 test. Continuous variables were analysed with an independent student’s t-test, while categorical variables were analysed with a χ2 test. Multivariate logistic regression analysis was then used to examine associations between demographic characteristics and comorbidities with 90-day readmissions. There was no significant difference in the Elixhauser Comorbidity Index between patients who were readmitted and those who were not, Hydrick and colleagues found.

The analysis suggested that an estimated 14,378 patients underwent elective revision lumbar fusion surgery in 2014, with a readmission rate of 3.1% (n=446) within 90 days, and an average of 37.8 days to readmission. Of the 29 comorbidities that were assessed, only diabetes with chronic complications was found to be a significant predictor of readmission in both univariate and multivariate analyses (OR 1.57, CI 1.31-1.89; P=0 .001). Due to an increasing number of Americans living with diabetes, Hydrick and colleagues wrote, it is important for surgeons to identify and medically optimise glycemic levels in patients undergoing elective revision lumbar surgery.

Additional complications associated with increased odds of readmission, Hydrick and the study team found, include deep vein thrombosis (OR 1.78, CI 1.23-2.57; P=0.002), disruption of surgical wound (OR 2.39, CI 1.08-5.30; P=0.032), hematoma/seroma (OR 2.24, CI 1.20-4.18; P=0.011), and pneumonia (OR 3.84, CI 2.21-6.67; P<0.001). Hydrick and colleagues also found that when assessing strictly anterior and posterior surgical approaches, an anterior approach was associated with increased odds of readmission (OR 1.40, CI 1.12-1.75; P=0.003). Diagnoses on readmission were assessed by identifying the ICD-9 diagnosis codes associated with each readmission, which found that the three most common of these diagnoses on readmission were: implant-related complications (n=67, 15.0%); postoperative infection (n=39, 8.74%); and, disc herniation (n=36, 8.07%).

On the treatment cost, Hydrick and colleagues estimated that the average total hospital cost for patients who were readmitted within 90 days was US$136,087 compared with US$39,935 for patients who were not readmitted.

Concluding, Hydrick and colleagues note that there are relevant patient comorbidities and perioperative complications that have an independent, significant association with increased odds of readmission within the 90-day window following elective revision lumbar fusion. Additionally they state that readmissions within the 90-day window have been shown to incur immense total cost to the hospital in comparison to those patients who were not readmitted. “Implementation of strategies to mitigate the impact of these comorbidities and complications will help improve outcomes and reduce hospital costs within this population”, they suggest.

In discussing their findings, authors suggest that the study is the first to examine 90-day readmissions characteristics in the population on a national level. This, they suggest, could enable physicians to recognise patients who are at increased risk of readmission, in order for perioperative risk-reduction strategies to be implemented to increase positive outcomes and minimise any associated health care costs in the future. They suggest that differences in readmission rate from those reported in existing literature likely reflect the exclusion of non-elective cases and serial readmissions. However, they suggest that these latter differences are likely small and difficult to measure. “Further studies would be warranted to identify specific causes for disparity between rates of readmission,” the study team note.

On the significance of the findings, Hydrick commented to Spinal News International: “There is a wealth of 30-day readmissions data, but not much is available regarding readmissions outside this window. Given the previous success of implementing bundled payments for 90-day episodes of care following other common orthopaedic procedures, it is likely that additional bundled payment models may one day be implemented for lumbar surgeries. Therefore, it is important that risk factors for 90-day readmissions be studied in order to optimise outcomes and reduce hospital costs. While it is not surprising to our team that diabetes was found to be a risk factor for readmission following elective revision lumber surgery, this study identifies diabetes as a possible target for new investigations into reducing 90-day readmissions following elective revision lumbar surgery, and approximates the economic impact that these readmissions carry.”


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