Thoracic Ossification of the Ligamentum Flavum―Neuroradiologic and Pathologic Findings Based on Our Operative Experience and a Literature Review―

Abstract

Purpose We experienced 10 cases of ossification of the ligamentum flavum OLF and report the neuroradiologic and pathologic findings. The pathogenesis of OLF is discussed, and a literature review is provided. Materials and Methods We treated 10 cases of thoracic OLF between 2010 and 2016. Neurologic symptoms and the Japanese Orthopaedic Association JOA score were evaluated. The postoperative recovery rate and JOA score RR% were calculated and compared with the preoperative results. Computed tomography CT and magnetic resonance imaging MRI were performed, and all 10 cases underwent laminectomy. Pathologic findings were evaluated. Results The age range of patients was 34 82 years, with 8 male and 2 female patients. All 10 cases developed myelopathy at the thoracic cord level. CT showed beak like ossification extending to the intervertebral foramen. Pathologic findings demonstrated laminar ossification in the ligamentum flavum. Preoperative JOA scores ranged from 3 to 19 mean 9.3 5.1. One year postoperative JOA scores ranged from 17 to 29 mean 23.4 4.7 , and the RR% increased from 53.8 to 100 mean: 71.3 11.5. Pathologic findings demonstrated laminar deposition of calcium phosphate in the intervertebral foramen. Chondrocytes enclosed by calcification and laminar hyaline cartilage were observed. Osteoblasts were observed in deposits of calcium phosphate. Conclusions OLF is independent of spondylotic change and calcification of spinal ligaments. The neuroradiologic and pathologic findings suggested that chronic mechanical stimulation compression and tension of the ligament leads to gene expression and induction of transforming growth factors e.g., bone morphogenetic growth factors, etc. , resulting in chondral ossification. Laminectomy for appropriate levels was effective.

The Symptomatic Calcification and Ossification of the Ligamentum Flavum in the Spine: Our Experience and Review of the Literature

“…OLF: There were spondylotic changes in 17 cases, developmental narrowing of the spinal canal in 7 cases, disc herniation in 7 cases, ossification of the longitudinal ligament in 4 cases, diffuse idiopathic skeletal hyperostosis (DISH) in 4 cases, and ankylotic spinal hyperostosis (ASH) in 3 cases [ 31 , 51 , 52 ]. Two-dimensionally reconstructed CT images showed beak-like ossification extending into the intervertebral foramen ( Figure 5 ) ( Table 3 ).…”

“…The prevalence of OLF requiring surgery in spondylotic changes was 22 (1.2%) out of the 1,800 cases who presented to MIMH and OMUH between April 2010 and March 2022 for spinal surgery due to neurological symptoms and spondylotic changes, which was similar to the rates reported in previous studies [ 32 , 36 , 39 ]. The neurological symptoms and signs were characterized by gradually progressive myelopathy ( Table 1 and Table 2 ) [ 32 , 36 , 37 , 39 , 51 ]. These symptoms and signs developed gradually due to ossified mass lesions compressing the spinal cord, but in some cases, rapid development occurred due to disc herniation and instability ( Table 1 and Table 2 ).…”

“…In some cases, OLF was associated with DISH and ASH, indicating a more generalized ossification pattern ( Table 3 ). Previous reports have reported the association of DISH and ASH in OLF, but the specific features of this association were unclear [ 51 , 52 ]. In both CLF and OLF, spondylotic changes were the most common associated condition, followed by disc herniation and instability.…”

“…A gutter with a similar width to the spinal canal was created, and the OLF was drilled out from the laminae. In cases where OLF was severely adherent to the dura mater, part of the OLF was intentionally left behind ( Figure 2 ) [ 50 , 51 ]. For cases with instability, single-stage laminectomy with PLF was performed [ 49 ].…”

Analysis of Influencing Factors on Short-Term Efficacy of Percutaneous Transforaminal Endoscopic Lumbar Discectomy in the Treatment of Lumbar Disc Herniation

“…The adhesion of nerve root may limit the movement of spinal cord and nerve root, generate the corresponding local change and finally cause the residual or recurrent phenomenon of patient's symptoms [8] . While the transforaminal endoscopic surgical system (TESSYS) technique in the percutaneous transforaminal endoscopic lumbar discectomy addresses this problem, the TESSYS technique is based on refinement of a special spiral burr, grinding along the nerve root and removal of the ventral nucleus pulposus of the nerve root, hypertrophic calcified tissue, ligamentum flavum of the dorsal aspect, scar tissue, etc., to achieve complete never root release [9,10] .…”