Cervical adjacent segment degenerative disease ; Is it a natural history or fusion disease? -comparison between adjacent level of fusion and non-fusion segment- Byung-Wan Choi, M.D., Byung-Ryeul Choi M.D., * Kyung-Jin Song, M.D. * and Kwang-Bok Lee, M.D. * Departments of Orthopedic Surgery Gwangju Veterans Hospital, Chonbuk National University Hospital * -We have no financial relationships to disclose-

The purpose of this study was to evaluate the fusion itself can affect the adjacent segment degeneration or disease formation by comparing the radiological and clinical findings between adjacent to fusion segment and non- fusion segment in single level anterior fusion cases. PURPOSE

Demographic Data

Adjacent to fusion level (Group A) Fusion level Adjacent above level Adjacent below level

Adjacent to non fusion level (Group B) Fusion level Natural Segment

Radiological criteria of degeneration (Criteria I) 1. Modified Hilibrand`s adjacent segmental disc degeneration. -JBJS Grade Disease Plain Radiography I None Normal II Mild Narrowing of disc space (<50%), no posterior osteophytes III Moderate 50< X<75% of normal disc height, posterior osteophyte IV Severe > 75% of disc height posterior osteophyte

Radiological criteria of degeneration (Criteria II) 2. Development of adjacent-level ossification - Park et al, JBJS Grade I : none Grade II : extended across < 50% of the disc space Grade III : across > 50 % of the disc space Grade IV : complete bridging

Radiological criteria of degeneration (Criteria III) 3. Segmental instability - More than 3mm displacement in flexion/extension - Abnormal motion -Dvorak et al, 1988 Spine- 62 Ms Flex Ext

Adjacent segment disease - interbody fusion may lead to increases in mechanical stress at adjacent disc levels, thereby accelerating degenerative changes and producing clinical symptoms with time: the so-called ‘adjacent segment disease’. - Clinical evaluation of new radicular or myelopathic symptom occurrence for evaluation of ‘adjacent segment disease’. → Follow up MRI was performed.

RESULTS

Incidence of radiological degenerative change 1. The percentage of the cases showed degenerative change (according to fusion or not) 38/457(8%) Group AGroup B

Incidence of radiological degenerative change 2. The number of the cases showed degenerative change (in the cases of adjacent to fusion) Group A

Analysis according to radiographic criteria (Criteria I)(Criteria II)(Criteria III)

Incidence of degenerative disease Total: 4 cases/ 87 patient (4%) In group A: 2/174 segment(1%) → 1 re-operation (58ms) 58 Ms

Incidence of degenerative disease Total: 4 cases/ 87 patient (4%) In group B: 2/283 segment(0.7%) → 1 re-operation(64ms) p= Ms

Fusion itself can accelerate the severity of adjacent level degeneration as compared with non-fusion. But there was no correlation in the incidence of symptomatic adjacent segment diseases according to the fusion in single level anterior cervical arthrodesis for the degenerative cervical diseases. Adjacent segment disease is more a result of the natural history. CONCLUSION