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The Spine Blog

Friday, June 7, 2019

Bone Density and Adult Deformity Surgery

Spinal hardware is subject to very high loads following adult deformity surgery, and the bone-screw interface is essential in order to prevent loss of fixation. Additionally, fracture within the fusion construct or adjacent to it can also occur in patients with low bone density. The deformity literature and anecdotal surgeon experience have made it clear that osteoporosis is a major risk factor for failure following adult deformity surgery, yet surgeons have little to no evidence-based guidance about how to determine if bone density is sufficient for a planned surgery. Additionally, there are no guidelines addressing which patients need bone density evaluation or treatment of low bone density pre-operatively. Given this void in the literature, Dr. Kuprys and colleagues from New York retrospectively reviewed a cohort of 314 patients undergoing spinal fusion of five or more levels. They performed a chart review to determine how many patients had bone density was documented in the pre-operative evaluation, how many underwent evaluation with DEXA or vitamin D level analysis, how many were treated with vitamin D, calcium, or medications to increase bone density, and how many were referred to a bone density specialist. They studied trends in these outcomes over time from 2012-2017. The average age of the cohort was 63, and 65% were female, indicating that a high proportion of their cohort was at risk for osteoporosis. In general, rates of bone health evaluation and treatment did not change significantly over time other than documenting bone health in the record, which increased form 12% in 2012-2014 to 26% in 2016-2017. Overall, 24% had a pre-operative DEXA scan documented in the record, which did not increase significantly over the study period. The rate of DEXA in men did increase over time, from 0% in 2012-2014 to 19% in 2016-2017. Not surprisingly, the rates of bone density evaluation and treatment were higher for females and those over 65.

This paper does not offer guidelines for how to consider low bone density while planning adult deformity surgery or how to evaluate and treat it pre-operatively. However, it does shine a light on the glaring lack of guidelines and knowledge in this field. The study demonstrates relatively low rates of work-up for low bone density in this population, which is probably not appropriate. Overall, 29% of women had pre-operative DEXA scans documented, as did 32% of patients over age 65. Given the high rate of low bone density in these populations and the importance of good bone density to have a successful outcome with major deformity surgery, a higher proportion of female and elderly patients should have probably undergone bone density evaluation. Currently, surgeons are left to practice the art of medicine without evidence-based guidance when determining who to work-up and treat for low bone density and how to determine if bone density if sufficient for a given surgery. Is it reasonable to perform a pedicle subtraction osteotomy and scoliosis correction in a 65 year old female with a T-score of -2.8 at her femoral neck? No one knows the answer to this question, though the chance of failure is higher than in the same patient with a T-score of -1.8. If low bone density is being treated, to what level does the bone density have to improve prior to going ahead with surgery? Do patients need to be off their antiresorptive therapy perioperatively, and, if so, for how long pre- and post-operatively? Surgeons currently do not have guidelines to allow them to answer these questions, and they are important questions encountered daily in a busy spine practice. Hopefully this article and others will serve as an impetus for spine societies to produce guidelines for the evaluation and management of bone density in spine fusion surgery.

Please read Dr. Kuprys's article on this topic in the June 15 issue. How do you consider bone density when planning adult deformity surgery? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS
Associate Web Editor