Ossification of the Posterior Longitudinal Ligament: Etiology, Diagnosis, and Outcomes of Nonoperative and Operative Management

Abstract

Study Design Narrative review. Objective To provide an overview on the diagnosis, natural history, and nonoperative and operative management of ossification of the posterior longitudinal ligament (OPLL). OPLL is a multifactorial condition caused by ectopic hyperostosis and calcification of the posterior longitudinal ligament. Familial inheritance and genetic factors have been implicated in the etiology of OPLL. The cervical spine is most commonly affected followed by the thoracic spine. The clinical manifestations range from asymptomatic to myelopathy or myeloradiculopathy. Methods Using PubMed, studies published prior to October 2014 with the keywords "OPLL, etiology"; "OPLL, genetics"; "OPLL, spinal cord injury"; "OPLL, natural history"; "OPLL, non-surgical management"; OPLL, surgical management"; "OPLL, surgical complications" were evaluated. Results The review addresses the etiology, epidemiology, classification, clinical presentation, imaging findings, and nonoperative and operative management of OPLL. Complications associated with surgical management of OPLL are also discussed. Conclusions OPLL commonly presents with myelopathy and radiculopathy. Spine providers should consider OPLL in their differential diagnosis and when reviewing images. If surgical intervention is pursued, imaging-based measurements and findings can help in choosing an anterior versus posterior surgical approach.

Keywords: OPLL; complications; diagnosis; management; natural history; ossification of the posterior longitudinal ligament; outcomes; surgery.

Fig. 1

(A) Sagittal computed tomography (CT) demonstrating continuous ossification of the posterior longitudinal ligament (OPLL) from C2 to C4. (B) Axial CT of C3 vertebral body demonstrating a continuous OPLL.

Fig. 2

(A) Sagittal computed tomography (CT) demonstrating segmental ossification of the posterior longitudinal ligament (OPLL) at C5 and C6. (B) Axial CT demonstrating segmental OPLL. (C) Sagittal T2-weighted magnetic resonance imaging demonstrating the segmental OPLL at C5 and C6.

Fig. 3

(A) Sagittal and axial computed tomography (CT) of the thoracic spine demonstrating beak ossification of the posterior longitudinal ligament (OPLL) in a patient with diffuse idiopathic skeletal hyperostosis. (B) Sagittal and axial CT of the thoracic spine demonstrating flat OPLL. (Images courtesy of Hideki Murakami, MD, Kanazawa University, Kanazawa, Japan.)

Fig. 4

An 82-year-old-man involved in a motor vehicle collision presented with left upper and lower extremity weakness. (A) Sagittal computed tomography demonstrated a mixed type of ossification of the posterior longitudinal ligament (OPLL; continuous at C3–C4 and segmental at C5). (B) Sagittal T2 fat-suppressed sequence demonstrated cord signal change predominantly on the left side. (C) The patient underwent an urgent laminectomy of C3 to C4 with instrumented posterior spinal fusion C2 to C4.

Fig. 5

Measurements used in surgical planning of ossification of the posterior longitudinal ligament (OPLL). (A) Occupancy ratio can be calculated to decide on an anterior versus posterior decompression . It is calculated by dividing a (distance between largest width of OPLL to posterior spinal canal) by b (spinal canal diameter) and multiplying by 100. Anterior decompression is recommended with a ratio of 60% and higher. (B). Effective lordosis measured by a line from the dorsal-caudal aspect of the C2 vertebral body to the dorsal-caudal aspect of C7. Effective lordosis is maintained in this case because no ventral structures such OPLL, vertebral body, or osteophytes are dorsal to the line. This patient would be a candidate for a posterior-based surgery. (C) The K-line on the lateral radiographs connects the midpoints of the spinal canal at C2 and C7. In K-line-positive cases, the OPLL is ventral to the line and in K-line-negative cases, the OPLL is dorsal to the line. In K-line-positive cases, a posterior approach is recommended. (D) Ossification-kyphosis angle (α) is measured on sagittal thoracic magnetic resonance imaging by drawing a Cobb angle from the cranial vertebrae to the caudal vertebrae that span the planned decompression site and centered over the largest OPLL fragment. An ossification-kyphosis angle > 23 degrees should undergo an anterior decompression.