Spine Readmissions and Reoperations

Definition and Prevalence

Readmissions among Medicare beneficiaries are prevalent and costly. In 2011, there were approximately 3.3 million adult readmissions in the United States. Hospital readmissions have a financial and clinical impact. The 30-day readmission costs in the Medicare population were reported to be $17 billion in 2009. In 2016, unplanned readmission costs were estimated at $41 billion. Readmission is defined as a subsequent hospitalization at any hospital within a specified period of time after being discharged. For Medicare, readmission is defined as any subsequent hospitalization within 30 days of a patient’s index stay.

Rates in Spine Surgery

Overall rates of readmission after spine surgery are difficult to predict. Large administrative databases lack granular information, whereas institutional databases are often underpowered. Thus, each source has inherent limitations, showing why, in the current literature, such a high degree of variability exists in reported rates of readmission. A systematic review conducted by Bernatz et al. found the 30-day readmission rate following spine surgery to be between 4.2% and 7.4%. The pooled readmission rate was 5.5%. Studies from single institutions have reported the highest rate 30-day readmission at 6.6%, and the lowest reported rate is 4.7% among multidisciplinary studies. Singh et al. reported a mean readmission rate of 7.2% looking at Medicare data from 2003 to 2007. Studies, including all spinal levels, had a higher 30-day readmission rate than exclusively lumbar studies, but the difference between the two rates was not statistically significant.

Several studies have looked at 90-day readmission rates. It has been reported that 34% of Medicare beneficiaries are readmitted within 90 days. This increased window duration will help further understand potential opportunities to improve and best practices. Data regarding 90-day spine surgery readmissions are also variable. Wadhwa et al. looked at data from the Quality and Outcomes Database Lumbar Spine Registry and reported a 6.3% 90-day readmission rate. A 2.5% 90-day readmission rate following elective lumbar spine surgery was reported in review of the 2014 Nationwide Readmission Database, and is one of lowest reported rates. Several studies have looked at institute data. Steinmetz et al. reported a 7.2% 90-day readmission rate after surgery for lumbar spinal stenosis, and Hill et al. reported a 5.6% rate at a single institute. Akamnonu et al. reported a 90-day readmission rate of 2.1% to 7.1%, depending on pathology, with an overall rate of 3.3%.

Risk Factors

Risk factors for readmission are often divided into 30- and 90-day intervals. Justification for this division includes the lack of presentation of some complications within a 30-day period and the fact that large administrative databases often do not include follow up after a 30-day period. Several risk factors for 30- and 90-day readmissions have been identified. The most frequently reported risk factors for 30-day readmission include higher American Society of Anesthesiology (ASA) score, longer operative duration, and the use of Medicare/Medicaid insurance. Other studies have reported strong risk factors for 30-day readmission to be wound dehiscence, weekend admission, coagulopathy, and incidental durotomy. The 90-day readmissions were associated with several significant factors, which included a diagnosis of surgical site infection (SSI), acute kidney injury, urinary tract infection, or congestive heart failure. Male sex was associated with decreased odds of readmission. Independent risk factors identified for 90-day readmission in a study that looked at the Nationwide Readmissions Database in 2014 for elective lumbar spine surgery were anemia, uncomplicated diabetes and diabetes with chronic conditions, surgical wound disruption, acute myocardial infarction, self-pay status, and anterior surgical approach. Older age was not linked to increase in 90-day readmission, as reported by prior studies looking at 30-day readmissions.

Reported causes for 30-day readmission include SSI, being the most common, followed by deep venous thrombosis and pulmonary embolus. ^{, , ,} Ninety-day readmission causes may be more related to implant and surgery.

Risks for spine SSI have been reported to include morbid obesity, coronary artery disease, increased duration of surgery, and increased length of stay (LOS). Risk of venous thromboembolism (VTE) within 30 days of surgery include history of VTE, estimated blood loss, fracture, history of pulmonary embolism (PE), transfusion, comorbid disease burden, and tumor surgery. Transfusion was also associated with reoperation, as there was an associated risk of epidural hematoma within 30 days. Studies have noted that transfusion and estimated blood loss are independent factors for VTE and are associated with numerous negative outcomes after spine surgery, including both readmission and reoperation.

Identifying the potential risk factors and timing will help with implementation of perioperative education and development of standardized protocols to help improve quality of care and decrease cost, thereby improving the value of spine care. Standardized protocols have been shown to improve outcomes surrounding several facets of spine care, including reduction of SSI and VTE prophylaxis.

Dural tear was reported to be the cause for 4.9% of 30-day readmissions. Although it may be a less significant cause for readmission, dural tear has been reported to be associated with a higher rate of in-hospital mortality and higher cost. Indeed, the cost was found to be $13,330 more than those without a dural tear. Therefore, it is worth highlighting, as it is potentially preventable. Wang et al. reported no variations in readmission rates among surgeons. There was also no correlation noted with readmission rates and LOS.