Ossification of the Posterior Longitudinal Ligament

Pathogenesis, Management, and Current Surgical Approaches: A Review

Zachary A. Smith, M.D.; Colin C. Buchanan, M.D.; Dan Raphael, P.A.-C.; and Larry T. Khoo, M.D.

Disclosures

Neurosurg Focus. 2011;30(3):e10 

In This Article

Anterior Cervical Corpectomy and Fusion

The majority of patients with OPLL present with multilevel cervical disease that often requires extensive decompression. Some controversy persists regarding the most appropriate method for treating cervical compression and myelopathy in these patients. Some authors argue that since the ossification in cases of OPLL remains ventral to the spinal cord and can continue to progress after surgery, posterior decompression fails to prevent "hill-shaped" and massive ossification in the years after a successful posterior decompression.[31] Furthermore, clinical myelopathy scores have been shown to improve most significantly with ACC. Several studies have shown better outcomes following anterior rather than posterior decompression for OPLL. Epstein[13] found superior clinical outcomes when comparing anterior versus posterior approaches in 51 patients treated for OPLL. Fessler et al.[20] found that patients treated by an anterior approach had an average improvement of 1.24 Nurick grades when compared with laminectomy patients who only improved by 0.07. In addition, laminectomy and fusion or laminoplasty is not appropriate in patients with poorly preserved cervical lordosis.

Several authors have noted the high incidence of complication with ACC. The rate of all surgical complications (including CSF leak, graft extrusion, or incomplete fusion) was 23%.[61] Approximately half of these patients would eventually require revision surgery. Pseudarthrosis requiring revision surgery was reported to occur in up to 15% of patients following ACC for OPLL in another series.[13] Soft-tissue morbidity, including permanent dysphagia or dysphonia, need for prolonged intubation, and less commonly vertebral artery or esophageal injury may additionally occur.[4] Postoperative C-5 palsy, a known complication of anterior and posterior approaches, may also occur.[57] In our own practice, we have found these complications to be especially of concern in patients with multiple comorbidities or advanced age.

Successful attempts to remove the ossified ligament from an anterior approach have at times been limited by significant bleeding from the epidural space or dural ossification. Advanced OPLL is commonly associated with thinning of the dura, and the dural membrane's integrity is commonly compromised as it merges with the ossified PLL. As a result, dural injuries causing a postoperative CSF leak as well as injury to the neural tissue become more likely.[24] In cases of severe dural ossification, we use an "anterior floating" method. With this method, central areas of densely ossified ligament and dura are detached laterally and superomedially from the surrounding PLL. This results in a "floating," ossified island of bone that will move freely and does not compress the cord (Fig. 4). This method has been previously advocated for patients in whom the ossified mass involves more than 60% of the cervical canal.[70] This method has made anterior decompression for cervical myelopathy associated with severe OPLL more efficient and safer.

Figure 4.

Postoperative CT scans demonstrating ventral decompression supplemented with anterior fusion with a plated cage and posterior laminectomy and fusion in the patient in Fig. 3. A central ossified bar was left in place following extensive lateral decompression. A: This "floating" bar can be seen on the sagittal midline CT (arrows). B and C: Axial image obtained at the C-3 level (B) demonstrating the extent of lateral decompression (black arrows) and remaining midline bar (white arrows in B and C). At C-5, a single pearl of ossified bone remains (C).

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