Posterior avulsion fracture at adjacent vertebral body during cervical disc replacement with ProDisc-C: a case report.

STUDY DESIGN: A case report. OBJECTIVE: To report posterior avulsion fractures at the adjacent vertebral bodies that occurred during cervical arthroplasty with ProDisc-C, which was thought to be related to design of the prosthesis and lack of the prudence in surgical technique. SUMMARY OF BACKGROUND DATA: There is no previous report on the avulsion fracture of the posterior vertebral body during cervical arthroplasty. METHODS: A 32-year-old-man presented with painful numbness and weakness of the right upper extremity for 2 months. On magnetic resonance imaging and computer tomography scans, a huge disc herniation at C6-C7 segment compressing the right C7 root and the spinal cord was identified. To prevent acceleration of degeneration of the C5-C6 segment, disc replacement of the C6-C7 with the ProDisc-C after anterior discectomy was planned. RESULTS: Nearing the end of the second chiseling with a box cutting chisel, and following further mallet impaction to insert the chisel a bit more, copious bleeding occurred. Hurried hemostasis was accomplished. The posterior central vertebral bodies of C6 and C7 were found to be fractured and avulsed bony fragments were displaced posteriorly compressing the spinal cord. The bony fragments were carefully removed and the ProDisc-C was inserted as planned. The patient recovered without neurologic deficit. CONCLUSIONS: Owing to keel design of the prosthesis, the possibility of posterior avulsion fracture of the vertebral body should always be appreciated in cervical disc arthroplasty with ProDisc-C, especially during chiseling with the box cutting chisel and inserting the prosthesis. Further, insertion of either of them beyond the posterior ends of the keel cuts made by a keel cutting chisel should not be tried.

CHARITE versus ProDisc: a comparative study of a minimum 3-year follow-up.

STUDY DESIGN: A retrospective study. OBJECTIVES: To evaluate and compare clinical and radiologic outcomes of the CHARITE and ProDisc. SUMMARY OF BACKGROUND DATA: There is no clinical report comparing CHARITE and ProDisc. METHODS: Among a total of 61 patients who underwent total disc replacement, 57 patients followed more than 3 years were enrolled. The CHARITE was used in 33 patients and ProDisc in 24. MRI follow-up was possible in 52 patients. Clinical and radiologic data including range of motion (ROM) and facet degeneration of the replaced segment, and degeneration of the disc at the adjacent level were evaluated. RESULTS: Mean percentage improvement of Oswestry Disability Index (ODI) score was 78.9% in the CHARITE group and 75.8% in ProDisc group. The mean improvement of the Visual Analogue Scale (VAS) pain score was 72% in the CHARITE and 74.2% in ProDisc. There was no statistical difference between 2 groups in improvement rates either of the ODI scores and VAS scores. Degradation of the facets was seen in 36.4% of the CHARITE and 32% of the ProDisc. Degradation of disc degeneration at the adjacent level above the index level was seen in 19.4% in the CHARITE and 28.6% in the ProDisc. The degradation rates of facet joints and disc at adjacent segment between the 2 groups were not significantly different. Segmental ROM of the replaced segments was well preserved, but ROM of L5-S1 of the ProDisc was significantly less than that of the CHARITE. CONCLUSIONS: While clinical outcomes of both CHARITE and ProDisc groups were fairly good, the facet joint of the index level and the disc at the adjacent level showed an aggravation of the degenerative process in a significant number of patients, regardless of the device used, raising concerns of possible late consequences of total disc replacement, especially regarding facet arthrosis and adjacent segment disease.