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The computed tomography-based fractal analysis of trabecular bone structure may help in detecting decreased quality
Marcin Czyz1, Arion Kapinas2, James Holton3
1Spinal Service, The Royal Orhopaedic Hospital NHS Trust, Birmingham, UK; The Centre for Spinal Studies and Surgery, Nottingham University Hospitals NHS Trust, Nottingham, UK.
Background Context:
To date, no reliable method is available to determine the parameters of bone density based on the routine spinal computed tomography (CT) in the emergency setup. We propose the use of fractal analysis to detect patients with poor quality of bone before urgent or semi-urgent spinal procedures.
Purpose:
This study aimed 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 before urgent spinal procedures.
Study Design:
This is a retrospective analysis of prospectively collected data.
Methods:
Patients in whom the dual-energy x-ray absorptiometry (DEXA) scan and lumbar spine CT were performed at an interval of no more than 3 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 with the results of the DEXA scan: bone mineral density (BMD) and T-score by mean of correlation coefficients. Receiver operating characteristic curve analysis was later performed to determine the cutoff value of FD.
Results:
A total of 102 vertebral levels obtained from 35 patients (mean age 60±18 years; 29 female) were analyzed. 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<.0001) and negatively correlated with BMD (R Spearman, -0.53; p<.0001) and T-score (-0.49; p<.0001). Receiver operating characteristic curve analysis revealed that a cutoff value of FD>1.53 indicates DBD (p<.0001; area under the ROC curve [AUC], 0.84; 95% confidence interval [CI], 0.76-0.91).
Conclusions:
This study shows that fractal analysis of the lumbar spine CT images may be used to determine bone density before spinal instrumentation (eg, metastatic or traumatic cord compression). Further prospective studies comparing results of the fractal analysis of CT scans with quantitative CT (qCT) are warranted.