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 f eatures 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 compress ion. Incomplete decompression via removal of only coexisting herniated inte rvertebral discs or spondylotic spurs might be performed, resulting in unsa tisfactory surgical outcomes, when the PLL becomes abnormally thickened and contributes to myelopathy. METHODS: Patients with HPLL who underwent cervical decompression surgery we re selected. Medical records and radiographs were retrospectively reviewed, to obtain data on the pre- and postoperative clinical conditions of the pa tients. Autopsy cases with HPLL proven by low-energy x-ray examinations wer e 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 develope d myelopathy, whereas one patient developed radiculopathy. Radiologically, all HPLL cases exhibited coexisting herniated intervertebral discs and 10 e xhibited small segmental ossifications of the PLL. Magnetic resonance imagi ng or computed tomographic myelography revealed extensive cord compression across the vertebral endplate level. The average preoperative Benzel modifi ed Japanese Orthopaedic Association score was 10.8, and the average postope rative 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 d irect 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.