Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Mar 18, 2015; 6(2): 221-235
Published online Mar 18, 2015. doi: 10.5312/wjo.v6.i2.221
Fractal lacunarity of trabecular bone and magnetic resonance imaging: New perspectives for osteoporotic fracture risk assessment
Annamaria Zaia
Annamaria Zaia, Gerontologic and Geriatric Research Department, Italian National Research Center on Aging, I-60121 Ancona, Italy
Author contributions: Zaia A designed and performed the study, analyzed data, designed and wrote the paper.
Conflict-of-interest: The author has no conflict of interest to report.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Annamaria Zaia, PhD, Gerontologic and Geriatric Research Department, Italian National Research Center on Aging, Via Birarelli 8, I-60121 Ancona, Italy.
Telephone: +39-071-8004204 Fax: +39-071-206791
Received: June 18, 2014
Peer-review started: June 19, 2014
First decision: July 10, 2014
Revised: November 5, 2014
Accepted: December 16, 2014
Article in press: December 17, 2014
Published online: March 18, 2015

Osteoporosis represents one major health condition for our growing elderly population. It accounts for severe morbidity and increased mortality in postmenopausal women and it is becoming an emerging health concern even in aging men. Screening of the population at risk for bone degeneration and treatment assessment of osteoporotic patients to prevent bone fragility fractures represent useful tools to improve quality of life in the elderly and to lighten the related socio-economic impact. Bone mineral density (BMD) estimate by means of dual-energy X-ray absorptiometry is normally used in clinical practice for osteoporosis diagnosis. Nevertheless, BMD alone does not represent a good predictor of fracture risk. From a clinical point of view, bone microarchitecture seems to be an intriguing aspect to characterize bone alteration patterns in aging and pathology. The widening into clinical practice of medical imaging techniques and the impressive advances in information technologies together with enhanced capacity of power calculation have promoted proliferation of new methods to assess changes of trabecular bone architecture (TBA) during aging and osteoporosis. Magnetic resonance imaging (MRI) has recently arisen as a useful tool to measure bone structure in vivo. In particular, high-resolution MRI techniques have introduced new perspectives for TBA characterization by non-invasive non-ionizing methods. However, texture analysis methods have not found favor with clinicians as they produce quite a few parameters whose interpretation is difficult. The introduction in biomedical field of paradigms, such as theory of complexity, chaos, and fractals, suggests new approaches and provides innovative tools to develop computerized methods that, by producing a limited number of parameters sensitive to pathology onset and progression, would speed up their application into clinical practice. Complexity of living beings and fractality of several physio-anatomic structures suggest fractal analysis as a promising approach to quantify morpho-functional changes in both aging and pathology. In this particular context, fractal lacunarity seems to be the proper tool to characterize TBA texture as it is able to describe both discontinuity of bone network and sizes of bone marrow spaces, whose changes are an index of bone fracture risk. In this paper, an original method of MRI texture analysis, based on TBA fractal lacunarity is described and discussed in the light of new perspectives for early diagnosis of osteoporotic fractures.

Keywords: Osteoporosis, Fracture risk, Trabecular bone microarchitecture, Fractal analysis, Fractal lacunarity

Core tip: High-resolution magnetic resonance imaging emerges as a useful tool for in vivo characterization of trabecular bone architecture (TBA). However, texture analysis is not frequently used as the large number of calculated parameters makes difficult their interpretation. Dealing with complexity and fractal properties of living beings, it is possible to quantify morpho-functional changes in aging and pathology with a limited number of parameters. In this context, fractal lacunarity appears the most suitable approach to TBA texture analysis as it describes discontinuity of bone network and sizes of bone marrow spaces, changes of which are an index of increased fracture risk.