Soo-Taek Lim1, Won-Joong Kim1, Sang-Ho Lee2, Sang-Hyuck Min1, Byungjoo Jung2

1Departments of Orthopedic Surgery, Wooridul Spine Hospital, Seoul, Korea
2Departments of Neurosurgery, Wooridul Spine Hospital, Seoul, Korea

Keywords: Intervertebral disk displacement/surgery; lumbar vertebrae/ surgery/radiography; neurodegenerative diseases/diagnosis; prostheses and implants; range of motion, articular; spinal fusion/methods/adverse effects.


Objectives: This prospective study was designed to determine the changes in the adjacent discs and the facet joints at the spinal segments following artificial disc replacement (ADR).
Patients and methods: Twenty-seven patients (7 men, 20 women; mean age 47.2 years; range 29-69 years) were treated with ADR for symptomatic degenerative disease (L4-5 in 10, L5-S1 in 8, L3-5 in 2, and L4-5-S1 in 7 patients). Radiologic evaluations were based on dynamic flexion-extension radiographs and magnetic resonance (MR) images obtained preoperatively and postoperatively at the end of a year. Disc degeneration was assessed on T2-weighted midsagittal MR images of upper (n=27) and lower (n=12) adjacent levels according to the classification by Pfirrmann et al. Osteoarthritic changes (cartilage degeneration, subchondral sclerosis and osteophytes) in the facet joints at the replaced level were rated on T2-weighted MR axial images according to the classification by Grogan et al. Flexion-extension range of motion (ROM) was measured on radiographs by the Cobb method. Clinical results were evaluated by the Oswestry Disability Index (ODI). The mean follow-up period was 14.6 months (range 12 to 19 months).
Results: No surgical failures or complications were encountered. The mean ODI score improved significantly at the last follow-up (p<0.01). Of 27 superior adjacent discs, four improved and 23 remained unchanged; of 12 lower adjacent discs, one improved, and 11 did not change. None of the adjacent discs showed worsening. Many of the adjacent discs became more hydrated. The high-intensity zone disappeared in three adjacent segments. The facet joints and the adjacent facets showed neither improvement nor aggravation. Flexion-extension ROM showed significant improvement at two operated levels (L4-5 and L5-S1; p<0.01).
Conclusion: Early results of ARD seem to be promising for the prevention of adjacent segment degeneration.