Association between paraspinal muscle quality and surgery for adjacent segment disease

Adjacent segment disease (ASD) is one of the most common complications after spinal fusion. There are several risk factors for ASD, but recently the quality of the paraspinal musculature has been implicated as a potential risk factor. The purpose of this study is to examine the association between paraspinal muscle degeneration and risk of surgery for ASD.

We conducted a retrospective review of spinal fusion patients at our institution from 2009 to 2022 who underwent subsequent surgery for ASD. Inclusion criteria included patients aged 18 and older at time of index operation. Control cohort included patients who did not undergo subsequent surgery for adjacent segment disease with a minimum one year follow up. Patients were matched based on age, gender, and BMI. We measured paraspinal fat percentage and circumferential surface area (CSA) at L3 and at the proximal end of their future construct. Paraspinal fat percentage and CSA were measured using ImageJ (National Institutes of Health, Bethesda, Maryland, USA). Student T-test was used to evaluate for statistically significant differences with p-value ≤ .05.

A total of 154 patients were reviewed with 77 patients in each cohort. The average age and BMI in the control group was 61.3 and 30.0 versus 61.2 and 29.6 in patients who underwent subsequent surgery. Overall, patients who underwent surgery for adjacent segment disease had 24% higher paraspinal fat percentage at L3 (13.8 ± 7.7% vs. 11.1 ± 6.5%, p-value = .02) and 22% higher paraspinal fat percentage at the top end of their construct (16.0 ± 9.0% vs. 13.1 ± 7.1%, p-value = .03).

Our study found that patients who undergo surgery for adjacent segment disease have 24% higher fat percentage in their paraspinal musculature at L3 and 22% higher fat percentage at the proximal end of their fusion construct.