Lumbar interbody expanding cage: a preliminary study on an animal model

Interbody fusion devices are used in human medicine
for treating degenerative diseases of the spine. Currently, there is not a universally accepted assessment tool for determining fusion, and the definitive criteria for diagnosing a successful interbody fusion remain
controversial. The aim of this study was to describe
microscopic and helical computed tomography (CT) imaging in the assessment of lumbar interbody fusion
using cylindrical threaded titanium expanding cage in
sheep. One cylindrical threaded expanding titanium
cage (Proconcept – SA, Orange, France) was inserted
through a transperitoneal approach after radical discectomy and packed with cancellous bone autograft in five adult sheep. The subjects were euthanatized after three, six, 12, 18 and 24 months. CT images revealed lumbar fusion at 12 months post operation, whereas microscopic evaluations indicated the presence of lumbar fusion at 18 months. CT and histological grades were the same in 65% of the cases observed. There were not
a significant difference between CT, histological and
micro radiographic grades. Helical CT scanning can be
considered to be a suitable method for the monitoring
of lumbar fusion as it enables observation of the deposition of bony bridging within the cage.