Surgical decision-making for ossification of the posterior longitudinal ligament versus other types of degenerative cervical myelopathy: anterior versus posterior approaches

Abstract

Background: The debate between anterior or posterior approach for pathologies such as cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament (OPLL) have drawn heated debate but are still inconclusive. A narrative review was performed specifically to study the differences pertaining to OPLL and other causes of degenerative cervical myelopathy (DCM). Current evidence suggests that anterior approach is preferred for K-line (-) OPLL, K-line (+) with canal occupying ratio > 60% and DCM with pre-existing cervical kyphosis. Posterior approach is preferred for K-line (+) OPLL with canal-occupying ratio < 50-60%, and multi-level CSM. No particular advantage for either approach was observed for DCM in a lordotic cervical spine. Anterior approach is generally associated with more complications and thus needs to be weighed carefully during decision-making. The evidence is not convincing for comparing single versus multi-level involvement, and the role of patients' co-morbidity status, pre-existing osteoporosis and co-existent spinal pathologies in influencing patient outcome and surgical options. This should be a platform for future research directives.

Conclusion: From this review, evidence is still inconclusive but there are some factors to consider, and DCM and OPLL should be considered separately for decision-making. Anterior approach is considered for pre-existing cervical kyphosis in DCM, for K-line (-) regardless of canal-occupying ratio, and K-line (+) and canal-occupying ratio > 60% for OPLL patients. Posterior approach is considered for patients with multi-level pathology for DCM, and K-line (+) and canal-occupying ratio < 50-60% for OPLL.

Keywords: CSM; Cervical myelopathy; Cervical spine; Cervical spondylotic myelopathy; DCM; Degenerative cervical myelopathy; OPLL; Ossification of the posterior longitudinal ligament.

Fig. 1

T2 weighted MRI image showing a patient with cervical spondylotic myelopathy involving C5-C6 and C6-C7 levels (left) who underwent an anterior cervical corpectomy and fusion from C5-C7. Post-operative AP (middle) and lateral (right) x-ray images show a cage with bone graft stabilizing the C5-C7 segments

Fig. 2

Pre-operative lateral x-ray of a patient with multi-level ossification of the posterior longitudinal ligament (left) and significant narrowing of spinal canal with myelomalacia at C5-C6 as seen on the T2-weighted MRI (middle). A laminoplasty fixed with miniplates was performed (right)

Fig. 3

Spinal canal-occupying ratio calculated by dividing maximal ossification thickness (a) by the anteroposterior spinal canal diameter (b) on axial CT imaging

Fig. 4

Lateral x-ray of a patient with an ossification of the posterior longitudinal ligament. The black line demonstrates the K-line drawn by linking the mid-point of anteroposterior canal diameter at C2 and C7