[Comparison of different vertebral body prosthesis with reference to migration and primary stability in dorsoventral spondylodesis after corporectomy with and without laminectomy].

In order to allow speedy mobilization after vertebral body replacement, high primary stability as well as prevention of implant dislocation are required. It is unclear whether differences between common vertebral body replacement systems exist and whether spreadable implants improve primary stability. Migration characteristics of 3 different vertebral body replacement systems were determined using human lumbar spine specimens. Primary stability was assessed by loading specimens successively in 5 conditions: native, after dorsal spondylodesis, after laminectomy and after vertebral body replacement. Migration was shown to depend on cage design and spike shape. Dorsal spondylodesis in combination with vertebral body replacement reduced flexion/extension movement effectively independent of cage design. Stabilization potential in lateral bending was limited. None of the cages limited movement under torsional loading effectively. The possibility to spread the cage had a positive effect on stabilization.