Intrinsically Strong to Avoid Complications: How Bone Quality Can Serve as Predictor of Pseudoarthrosis and Hardware Failure in Adult Spinal Deformity Correction Surgery.

Introduction: Bone quality is well described as a key factor when predicting surgical complications. Poor bone mineral density can be devastating for hardware placement, likely due to diminished pullout strength and insertional torque, resulting in higher rates of pseudoarthrosis and screw pullout. DEXA scans and Hounsfield units (HU) are commonly employed as evaluators of bone health. We used these parameters to investigate the association between bone quality and different forms of hardware failure (HF) in patients undergoing surgical correction for adult spinal deformity (ASD).

Methods: This is a single-institution retrospective review of patients who underwent surgery for ASD between 2016 and 2023. We collected data including patient demographics, DEXA T-scores and HU at the level of the upper instrumented vertebra (UIV) and UIV +1. Hardware outcomes were also collected including HF, pseudoarthrosis, rod fracture, screw fracture, and screw pullout. Statistics were performed using SPSS.

Results: Two hundred sixty-five patients undergoing surgical correction for ASD were identified. HU data was available and collected for 164 patients, while DEXA data was available and collected for 122 patients. Those who experienced HF complications were found to have significantly lower HU at the level of the UIV than those who did not (p=0.006). Specifically, HF presenting as either screw pullout or pseudoarthrosis showed a statistically significant difference of 30 HU at the UIV level (175.4 vs 145.4, p=0.005). Patients with HF also showed, although not statistically significant, lower mean T-scores (-0.5612 vs -0.8482, p=0.089).

Conclusion : Bone quality is a significant consideration when evaluating surgical candidates for ASD correction. Osteoporosis and any degree of osteopenia can lead to an augmented rate of HF, either pullout or pseudoarthrosis. Stability provided by healthy bone is particularly important in these patients, which is demonstrated by our case series. HU at the UIV remains a reliable evaluation tool for these patients.