Characterization of bone marrow pathologies in modic changes of the human lumbar spine — ASN Events
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Characterization of bone marrow pathologies in modic changes of the human lumbar spine (#171)

Julia S Kuliwaba 1 2 , Adnan Mulaibrahimovic 1 2 , Brian JC Freeman 1 2 3 , Orso L Osti 4
  1. Adelaide Medical School, The University of Adelaide, Adelaide, South Australia, Australia
  2. Adelaide Centre for Spinal Research, SA Pathology, Adelaide, South Australia, Australia
  3. Spinal Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia
  4. Calvary Health Care, North Adelaide, South Australia, Australia

Introduction

Magnetic resonance imaging (MRI) identified vertebral Modic changes (MC) are associated with low back pain and disc degeneration. However, the aetiology and pathobiology of MC remain elusive. Clinical imaging studies of MC suggest disc/endplate damage and persistence of an inflammatory stimulus as a disease model. Since Modic’s 1988 case report on the histopathology of MC type 1 and 2 (n=3 per MC), there have been no further reports detailing bone marrow pathology of MC. Thus, the study aim was to characterize bone marrow pathologies associated with the spectrum of MC.

Methods

Forty-one patients (17 women, 24 men; mean age 55±13 years) underwent lumbar spine surgery with pedicle screw instrumentation and showed MC on pre-operative lumbar MRI. Cases were subdivided: MC type 1 (MC1; n=11), MC type 2 (MC2; n=23), MC type 3 (MC3; n=7). For all patients, a transpedicular vertebral subchondral bone biopsy (10-20mmx3mm) was harvested from the MC region and processed for undecalcified histology. Three trained assessors scored the presence and percentage tissue extent of bone marrow pathologies: inflammation (+/- neutrophil aggregates), fibrosis, oedema, and necrosis. Inter-observer reproducibility for pathology scoring was high (intraclass correlation coefficient 0.82).

Results

Inflammation was present at a moderate extent (20-50%) for all three MC types. MC1 bone marrow was fibrotic (20-50%) compared to MC2 (<5%) and MC3 (<5%), p<0.005. Oedema and adipocyte necrosis were minimal (<5%) for all MC types. There was no evidence of infection present in MC1, MC2, or MC3 bone marrow.

Conclusion

The predominant bone marrow pathology common to MC1, MC2, and MC3 is inflammation. Increased bone marrow fibrosis in MC1 distinguishes this MC type from MC2 and MC3. These observations are consistent with MC1 representing a bone marrow healing response to disc/endplate injury, whereas MC2 and MC3 appear to represent a chronic inflammatory process.