Abstract
In the literature, inter-vertebral MRI signal intensity changes (Modic changes) were associated with corresponding histological observations on endplate biopsies. However, tissue-level studies were limited. No quantitative histomorphometric study on bone biopsies has yet been conducted for Modic changes. The aim of this study was to characterise the bone micro-architectural parameters and bone remodelling indices associated with Modic changes. Forty patients suffering from disabling low back pain, undergoing elective spinal surgery, and exhibiting Modic changes on MRI (Modic 1, n = 9; Modic 2, n = 25; Modic 3, n = 6), had a transpedicular vertebral body biopsy taken of subchondral bone. Biopsies were first examined by micro-CT, for 3D morphometric analysis of bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular separation, trabecular number, and structure model index. Then, samples underwent histological analysis, for determination of bone remodelling indices: osteoid surface to bone surface ratio (OS/BS), eroded surface to bone surface (ES/BS) and osteoid surface to eroded surface ratio (OS/ES). Micro-CT analysis revealed significantly higher BV/TV (up to 70% increase, p < 0.01) and Tb.Th (up to +57%, p < 0.01) in Modic 3 biopsies, compared to Modic 1 and 2. Histological analysis showed significantly lower OS/BS in Modic 2 biopsies (more than 28% decrease, p < 0.05) compared to 1 and 3. ES/BS progressively decreased from Modic 1 to 2 to 3, whereas OS/ES progressively increased with significantly higher values in Modic 3 (up to 159% increase, p < 0.05) than in Modic 1 and 2. Significant differences were found in bone micro-architectural parameters and remodelling indices among Modic types. Modic 1 biopsies had evidence of highest bone turnover, possibly due to an inflammatory process; Modic 2 biopsies were consistent with a reduced bone formation/remodelling stage; Modic 3 biopsies suggested a more stable sclerotic phase, with significantly increased BV/TV and Tb.Th compared to Modic 1 and 2, linked to increased bone formation and reduced resorption.
Highlights
Low back pain linked to disc degeneration is one among the leading causes of functional incapacitation and chronic disability
Forty patients suffering from disabling low back pain, undergoing elective spinal surgery, and exhibiting Modic changes on magnetic resonance imaging (MRI) (Modic 1, n = 9; Modic 2, n = 25; Modic 3, n = 6), had a transpedicular vertebral body biopsy taken of subchondral bone
The aim of this study is to quantify and compare amongst samples of different Modic types the three-dimensional (3D) bone micro-architecture by means of microcomputed tomography, and bone remodelling characteristics by means of histology, in vertebral bone biopsies taken from adults undergoing spinal surgery and exhibiting Modic changes on preoperative MRI images
Summary
Low back pain linked to disc degeneration is one among the leading causes of functional incapacitation and chronic disability. Eur Spine J (2015) 24:1926–1934 classified characteristic magnetic resonance imaging (MRI) changes in the vertebral body bone marrow and endplates, adjacent to degenerating intervertebral discs. Type 3 changes (low T1 and T2 signals) were assumed to correlate with subchondral bone sclerosis [1, 2]. Their occurrence appears to increase with age and is associated with low back pain [3, 4]. To the best of the authors’ knowledge, no quantitative comparison among the three Modic types, in micro-architectural and remodelling characteristics of the trabecular bone adjacent to the endplates, has yet been published. A quantitative analysis of bone micro-architectural parameters and bone remodelling indices would contribute to the characterisation of Modic changes, important for a better understanding of the pathological process involved
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