Examination of the influence of ossification of the anterior longitudinal ligament on symptom progression and surgical outcome of ossification of the thoracic ligamentum flavum: a multicenter study

Clinical article

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The purpose of this study was to provide the first evidence for the influence of an ossified anterior longitudinal ligament (OALL) on the clinical features and surgical outcomes in an ossified ligamentum flavum (OLF) in the thoracic region.


Sixty-three patients who underwent surgery for a 1-level thoracic OLF were identified, and preoperative symptoms, severity of symptoms and myelopathy, disease duration, MR imaging and CT findings, surgical procedure, intraoperative findings, complications, and postoperative recovery were investigated in these patients. Entities of OALLs were found on sagittal CT images to be adjacent to or at the same vertebral level as the OLF were classified into 4 types: no discernible type (Type N), one-sided (Type O), discontinuous (Type D), and continuous (Type C).


The duration of symptoms was especially long for Types D and C OALLs. Patients with Type D OALLs had a significantly worse percentage of recovery, as well as worse preoperative JOA scores.


The authors' results showed that a Type D OALL had strong associations with preoperative severity of symptoms and surgical outcomes. These findings may allow surgeons to determine the severity of preoperative symptoms and the probable surgical outcomes from the OALL classifications. Moreover, surgery with instrumentation for Type D OALLs may produce better surgical outcomes.

Abbreviations used in this paper: ALL = anterior longitudinal ligament; CSM = cervical spondylosis myelopathy; DISH = diffuse idiopathic skeletal hypertrophy; JOA = Japanese Orthopaedic Association; OALL = ossified ALL; OLF = ossified ligamentum flavum; OPLL = ossified posterior longitudinal ligament.

Article Information

Address correspondence to: Kei Ando, M.D., Department of Orthopedic Surgery, Nagoya University School of Medicine, 65 Tsurumai Showa-ward, Aichi 466-8550, Japan. email: keikeiando@hotmail.co.jp.

Please include this information when citing this paper: published online November 11, 2011; DOI: 10.3171/2011.10.SPINE11296.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Axial CT classification of OLFs, with scans obtained at the middle of the facet joint. A: Lateral type. The OLF is located only in the capsular portion of the ligamentum flavum, which can be detected at the lateral edge of the spinal canal. B: Extended and enlarged type. The OLF is located at the surface of the ligamentum flavum and protrudes into the spinal canal. C: Fused type. Bilateral OLFs fuse at the middle of the OLF. D: Tuberous type. Fused OLFs make a tuberous mass at the middle of the spinal canal.

  • View in gallery

    Sagittal CT classification of OALLs at the OLF level. A: Type N, showing no OALL around the OLF level. B: Type O, in which the OALL exists at the rostral or caudal end of the OLF level but not at the OLF level. C: Type D, in which OALL exists at both the rostral and caudal ends of the OLF level but none at the OLF level. D: Type C, in which an OALL exists from the rostral to caudal level including the OLF level.

  • View in gallery

    Bar graph showing the number of OLF levels at each joint.

  • View in gallery

    Bar graph showing the relationship between OLFs and OALLs. The OLFs and OALLs tend to progress at a similar rate.



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