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In the course of the treatment of inflammatory and degenerative disc diseases, fractures and
tumors of the vertebrae, the intervertebral spondylodesis gained more and more clinical
relevance in the last years. This therapy is aimed at a stable vertebral fusion. For decades,
the tricortical iliac crest bone graft was considered as golden standard for interbody fusion of
the cervical spine. The necessary biopsy of autologous material, however, often results in a
significant morbidity among the patients. Subsidence, collapse or migration of the implant
occur as well. This might result in kyphotic deformity or nonunion. These complications
require a development of alternative intervertebral disc implants.
The goal of this study was a radiological examination of the spondylodesis using an
interbody titan-cage for stabilizing the intervertebral space. This implant was filled with four
different concentrations of modified parathyroid hormone TGplPTH1-34 (0.2 mg/ml, 0.4
mg/ml, 0.7 mg/ml, 1.0 mg/ml). Three groups were used for monitoring: a group with an
empty cage, a group implanted with cancellous bone graft and a group with fibrin.
For this purpose fifty-six adult female merino-mix sheep underwent discectomy of segment
C3/C4. Each monitoring group consisted of eight animals. After standing for twelve weeks,
the animals were euthanized and the vertebrae C3 and C4 were removed. Utilizing the plain
X-ray images that were taken preoperatively, postoperatively, after 8 weeks and post
mortem after twelve weeks, the disc space height and the intervertebral angle were
determined. The CT images for the subsequent bone density measurements were performed
on the isolated cervical vertebrae. Based on the plain X-ray images and CT scans a fusion
score was defined which describes the status of fusion after the twelve weeks.
For the most part the radiological evaluation of all collected parameters showed significant
differences between the monitoring groups. However, it was not possible to conclude a clear
statement on the basis of radiographic data, because no group consistently dominated.
There were crucial differences in the results of the groups in terms of the various
examinations. In comparison to the monitoring group “empty cage” and “fibrin” the levels of
PTH-groups were more promising and should be aligned with the results of histomorphology,
histomorphometry and biomechanics.