The CT-based fractal analysis of trabecular bone structure may help in detecting decreased quality of bone prior to urgent spinal procedures

Marcin Czyz^{a, b}, Arion Kapinas^b, James Holton^a, Renata Pyzik^c, Bronek M. Boszczyk^b, Nasir A. Quraishi^b

^a Spinal Service, The Royal Orhopaedic Hospital NHS Trust, Birmingham, UK; ^b The Centre for Spinal Studies and Surgery, Nottingham University Hospitals NHS Trust, Nottingham, UK; ^c Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, USA.

DOI: 10.1016/j.spinee.2017.04.014

Background context

To date no reliable method is available to determine the parameters of bone density based on the routine spinal CT in the emergency setup. We propose the use of fractal analysis to detect patients with poor quality of bone prior to urgent or semi-urgent spinal procedures.

Purpose

To validate the hypothesis that the CT-based fractal analysis of the trabecular bone structure may help in detecting patients with poor quality of bone prior to urgent spinal procedures.

Study design

Retrospective analysis of prospectively collected data.

Methods

Patients in whom the DEXA scan and lumbar spine CT were performed at an interval of no more than three months were randomly selected from a prospectively collected database. Diagnostic axial CT scans of L2, L3 and L4 vertebrae were processed to determine the fractal dimension (FD) of the trabecular structure of each spinal level. Box-count method and ImageJ 1.49 software were used. The FD was compared to the results of the DEXA scan: bone mineral density (BMD) and T-score by mean of correlation coefficients. ROC curve analysis was later performed in order to determine cut-of value of FD.

Results

A total of 102 vertebral levels obtained from 35 patients (mean age 60 ± 18 years; 29 female) were analysed. The FD was significantly higher in the group of patients with decreased bone density [DBD] (T-score < -1.0) (1.67 vs. 1.43; P < 0.0001) and negatively correlated with BMD (R-Spearman -0.53; P < 0.0001) and T-score (-0.49; P < 0.0001). ROC curve analysis revealed cut-off value of FD > 1.53 indicating DBD (P < 0.0001; AUC 0.84; 95%CI, 0.76-0.91).

Conclusion

This study shows that fractal analysis of the lumbar spine CT images may be used to determine bone density prior to spinal instrumentation (e.g. metastatic/traumatic cord compression). Further prospective studies are warranted comparing results of the fractal analysis of CT scans with qCT.