Analysis of hypertrophy of the posterior longitudinal ligament of the cervical spine, on the basis of clinical and experimental studies.

OBJECTIVE

The goal of this study was to elucidate the pathophysiological features and treatment of hypertrophy of the posterior longitudinal ligament (HPLL) of the cervical spine. HPLL is defined as a pathological thickening of the posterior longitudinal ligament (PLL), causing spinal cord compression. Incomplete decompression via removal of only coexisting herniated intervertebral discs or spondylotic spurs might be performed, resulting in unsatisfactory surgical outcomes, when the PLL becomes abnormally thickened and contributes to myelopathy.

METHODS

Patients with HPLL who underwent cervical decompression surgery were selected. Medical records and radiographs were retrospectively reviewed, to obtain data on the pre- and postoperative clinical conditions of the patients. Autopsy cases with HPLL proven by low-energy x-ray examinations were chosen for assessment of the pathological characteristics.

RESULTS

Seventeen men and three women with HPLL underwent treatment via an anterior approach, with direct removal of HPLL. Nineteen patients developed myelopathy, whereas one patient developed radiculopathy. Radiologically, all HPLL cases exhibited coexisting herniated intervertebral discs and 10 exhibited small segmental ossifications of the PLL. Magnetic resonance imaging or computed tomographic myelography revealed extensive cord compression across the vertebral endplate level. The average preoperative Benzel modified Japanese Orthopaedic Association score was 10.8, and the average postoperative score was 13.2. Histological examinations revealed thickening of the PLL with proliferation of chondrocytes, together with various degenerative changes.

CONCLUSION

Patients with HPLL can benefit from an anterior approach with direct removal of the HPLL and associated herniated intervertebral discs or ossification of the PLL. Cervical polytomography, computed tomography, and magnetic resonance imaging are useful in establishing a diagnosis of HPLL.