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|Year : 2018 | Volume
| Issue : 5 | Page : 1400-1403
Cervical ossified posterior longitudinal ligament: Etiology and surgical perspectives
V V Ramesh Chandra, B CM Prasad, P Rajesh
Department of Neurosurgery, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
|Date of Web Publication||17-Sep-2018|
Dr. V V Ramesh Chandra
Department of Neurosurgery, Sri Venkateswara Institute of Medical Sciences, Tirupati - 517 507, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Chandra V V, Prasad B C, Rajesh P. Cervical ossified posterior longitudinal ligament: Etiology and surgical perspectives. Neurol India 2018;66:1400-3
Ossification of the posterior longitudinal ligament (OPLL) is a hyperostotic condition that results in ectopic calcification of the posterior longitudinal ligament leading to narrowing of the spinal canal and causing neurological impairment. The etiopathogenesis of OPLL is multifactorial [Table 1], is poorly understood, and results from systemic and local factors in combination with a genetic abnormality  The authors should be congratulated for throwing light on the etiological aspects of OPLL. It is surprising to know that there is only one study in the literature addressing the role of fluorosis and OPLL in endemic areas. The present study documents and quantifies this strong association between fluorosis and OPLL in endemic areas using 24-hour urine fluoride levels. A search for biomarkers/metabolic profiling has yielded some result without any clinical significance attached to them.
Prevalence of OPLL is more common in the Asian population (4%) as compared to the Non-Asian population (0.01 to 2%). In patients with myelopathy, the prevalence of OPLL is 23-27%. The disease presents in the fifth or sixth decade, and with a male-to-female ratio of 2:1. Patients with OPLL present with varying degrees of neurologic syndromes including both radiculopathy and myelopathy. The clinician should look for subtle signs of neurological involvement (Romberg sign, tandem walking) to unmask the small group (5%) of asymptomatic patients. The patients with OPLL are prone to spinal cord injury (central cord syndrome) and the risk factors include an old age, as well as the presence of a segmental type of OPLL and/or ossification of the anterior longitudinal ligament.
A lateral radiograph is used to classify OPLL into four subtypes: continuous (an ossified mass that spans several vertebral bodies and the intervening disk spaces), segmental (ossification behind each vertebral body), mixed (mixture of both continuous and segmental types), and localized (ossification is localized to the intervertebral disk).
Nonoperative management of cervical OPLL is reserved for patients without myelopathy; and, 71% of these patients remain progression-free at 30 years. The risk factors for developing myelopathy are its occurrence at a younger age, an increased cervical range of motion, the presence of a continuous or mixed type of OPLL, an OPLL occupancy ratio 30-60%, the space available for the cord of 6 to 9 mm, and OPLL fragments that are more laterally deviated as visible on an axial CT image.
Surgery for cervical OPLL is reserved for patients with progressive myelopathy or myeloradiculopathy that has not responded to nonoperative treatment, and for patients presenting with spinal cord injury following the occurrence of trauma.
Surgical management of OPLL, specifically the choice of the anterior or the posterior approach, is a controversial issue and depends on many factors [Table 2] like the degree of compression, sagittal alignment, number of compressed levels, and the patient's general status.
The anterior approach [Figure 1] provides a direct access to the offending pathology. It involves the procedure of corpectomies and fusion, thus making the procedure complex and technically demanding. Modifications in the anterior approach like the “anterior floating method,” (that is, leaving a thin shell of the drilled posterior cortical shell of the OPLL floating on the anterior surface of the dura in case it is not separable from the dura) and an oblique corpectomy (drilling the vertebral body in an oblique trajectory to access the posterior osteophytic bar with OPLL to preserve the anterior vertebral body segment and cervical spinal stability) try to offset the complications associated with the anterior approach. The ‘anterior floating method' obviates neurological deterioration in case the OPLL is causing significant cord compression and cannot be separated from the anterior dura; an oblique corpectomy prevents the occurrence of spinal instability due to the performance of corpectomy that includes the drilling of both anterior and posterior parts of the vertebral body from an oblique angulation, and therefore, obviates the need for a bone graft. Factors that influence adopting an anterior approach include the presence of a kyphotic angulation (K line negative), a younger age, less than 3 segment vertebral compression, and an OPLL occupancy ratio of more than 50-60%. Posterior approaches [Figure 2] provide indirect decompression as the OPLL remains untouched and the spinal cord drifts posteriorly. The posterior procedures include a laminectomy, laminoplasty and laminectomy with fusion, which are technically simple and familiar. The complications encountered in posterior approaches include axial neck pain, C5 palsy, instability and progression of OPLL. However, the effect of indirect decompression of the spinal cord is limited. Factors that influence adopting a posterior approach include a lordotic spine (K Line positive), an older age, more than 3 segments compression, and an OPLL occupancy ratio of less than 50-60%. The latest addition to the approaches available to treat cervical OPLL is the anterior controllable anti-displacement and fusion (ACAF) surgery that can achieve anterior direct decompression without cutting the OPLL, thus combining the advantages and avoiding shortcomings of anterior and posterior decompression surgery. This can be used even in patients with more than three segment compression.
|Figure 1: (a) Sagittal reconstructed image of CT scan showing the poor curvature of the cervical spine with focal calcification of the anterior and posterior longitudinal ligament. (b) X Ray of the forearm bones showing interosseous membrane calcification. (c) Sagittal T2 weighted MRI scan showing the segmental OPLL spanning four vertebral segments with thecal compression mainly at the C5 and C6 segments . (d) A lateral radiograph of the cervical spine showing the C5--6 corpectomy and cage and plate placement|
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|Figure 2: (a) X Ray of the cervical spine showing that the normal cervical lordosis is maintained. (b) MRI T2 sagittal image showing a multi--segmental OPLL from C2 to C5 vertebral levels causing thecal compression that is extending beyond three vertebral levels. (c) T2 axial image showing the significant thecal compression due to the OPLL. (d) A C3--5 laminectomy and lateral mass fixation is performed|
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Decision making in the surgical management of cervical OPLL depends on the comfort/experience of the treating surgeon and the patient characteristics. The broad guidelines derived from literature can be summarized as:,,
- Lordotic spine, no cord changes, an OPLL occupancy ratio <50-60%, more than 3 segments involved: Laminoplasty, or laminectomy with fusion if the spine is kyphotic
- Kyphotic spine, cord changes, less than 3 segment compression, OPLL occupancy ratio >50-60%: Anterior corpectomy and fusion, or ACAF if more than 3 segments are compressed.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]