The Spine Blog

Friday, September 6, 2013

Readmission Rates Following Adult Deformity Surgery

As surgical and anesthetic technology advances, spine surgeons are performing more complex operations in increasingly older patients with greater comorbidity burdens than in the past. It is well established that long fusions for adult deformity including correction in the coronal and/or sagittal planes are associated with high rates of complications, readmission, and revision surgery. Given that readmission rate is being used as a proxy for quality of care by government and private payers, the spine surgery group at the University of California, San Francisco decided to review and report on their readmissions following surgery for adult deformity. They used administrative claims data to compile a cohort of 836 adult patients who underwent fusion for deformity from 2006 through 2011. While they did not explicitly define deformity, the majority of patients had fusions of four or more vertebrae, and nearly 40% had at least 9 vertebrae included in the fusion (defined as a “long fusion”).  The overall unplanned readmission rates were 8.4% at 30 days and 12.3% at 90 days.  Surgical site infection (SSI) was the most common cause for readmission, accounting for nearly 50% of the readmissions. Most of these occurred in the first 30 days following surgery. “Surgical complications” were the second most common cause of readmissions and included problems like proximal junctional kyphosis and iliac hardware failure. Medical complications and non-infected wound complications were less common causes of readmission. Risk factors for readmission included long fusions (> 9 vertebrae included in the fusion) and medical comorbidities. Patients undergoing long fusions had a threefold higher readmission rate compared to those undergoing short fusions (2 or 3 vertebrae included), and those with the highest grade of comorbidities had a twofold increase in reoperation rate compared to those without comorbidities. In the multivariate analysis, comorbidity burden was the strongest independent predictor of readmission—especially peripheral vascular disease, which increased the risk of readmission by a factor of four. Variables associated with the magnitude of surgery including length of fusion and duration of surgery were also predictive of readmission, but the strength of associations were weaker than for comorbidities. These results confirm that more extensive surgery in sicker patients results in relatively high readmission rates.


This study provides data that can serve as a good benchmark for expected readmission rates following adult deformity surgery and also indicates that risk adjustment based on magnitude of surgery and patient comorbidity burden is appropriate. The group that published the paper has extensive experience in adult deformity surgery, and it seems unlikely that one would expect lower rates of readmission than documented here. Nonetheless, a 17% 90 day readmission rate for long fusions is relatively high and raises the question of what type of patients should undergo such an operation. Currently there are no practice guidelines to help guide patient selection for deformity correction surgery, and the decision depends primarily on the judgment of the surgeon. Hopefully work in the future will allow for the creation of clinically useful models that can be used to predict the risks of complications, readmission, and reoperation based on the magnitude of the proposed surgery and patient characteristics. Knowing these numbers while going through the shared decision making process could affect whether or not patients elect to undergo such an operation. An important finding in this paper is that the most common reason for readmission is infection, with the authors reporting a 5.6% overall infection rate. They did not stratify infection rate based on length of fusion, though it seems likely that longer fusions would have a higher infection rate. This study included patients treated through 2011, so it seems unlikely that the authors would have been placing vancomycin powder in the wounds during this time frame. Given the marked improvement in infection rate that has been reported using this technique, it is possible that the infection and readmission rate will improve in the future.


Please read this important paper and let us know if it changes your perception of readmission following adult deformity surgery. Will it change how you approach these challenging cases? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor