The Impact of Type 2 Diabetes on Bone Metabolism and Growth after Spinal Fusion

Publication date: Available online 7 December 2018

Source: The Spine Journal

Author(s): Neil Bhamb, Linda E.A. Kanim, Ruben C. Maldonado, Trevor J. Nelson, Khosrowdad Salehi, Juliane D Glaeser, Melodie F. Metzger

ABSTRACT

Background context

Some clinical reports suggest diabetes may have a negative effect on spinal fusion outcomes, although no conclusive experimental research has been conducted to investigate the causality, impact, and inherent risks of this growing patient population.

Purpose

To analyze the hypothesis that type II diabetes (T2DM) inhibits the formation of a solid bony union after spinal fusion surgery by altering the local microenvironment at the fusion site through a reduction in growth factors critical for bone formation.

Study Design/Setting

In vivo rodent model of type II diabetes

Methods

Twenty control (Sprague Dawley, SD) and 30 diabetic (Zucker Diabetic Sprague Dawley, ZDSD) rats underwent posterolateral and laminar fusion surgery using a tailbone autograft implanted onto the L4/L5 transverse processes. A subset of animals was sacrificed 1-week post-surgery for growth factor analysis. Remaining rats were sacrificed 3-months post-surgery for fusion evaluation via manual palpation, microCT, and histology.

Results

There was no significant difference in the manual palpation fusion rate between ZDSD rats and SD control rats. Growth factor assay of fusion site explants at early sacrifice demonstrated PDGF was upregulated in the ZDSD rats. TGFB, IGF, and VEGF were not statistically different between groups. Bone mineral density (BMD) as determined by micro CT was significantly lower in ZDSD rats compared to SD controls and was a significant function of HbA1c.

Conclusion

Data generated in this in vivo rat model of T2DM demonstrate that the metabolic dysregulation associated with the diabetic condition negatively impacts the quality and density of the formed fusion mass. Increased measures of diabetic status, as determined by blood glucose and HbA1c, were correlated with decreased quality of formed fusion, highlighting the importance of diabetic status monitoring and regulation to bone health, particularly during bone healing.

Clinical Relevance

T2DM rats demonstrated increased rates of infection, metabolic dysregulation, and a reduction in spinal fusion consolidation. Clinicians should consider these negative effects during pre-operative care and treatment of this growing patient population.

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