[Biomechanical comparison of different stabilisation devices for transforaminal sacral fracture. Is an interlocking device advantageous?]

Abstract

Background: Reliable osteosynthesis for fractures in the different regions of the human pelvis are described in the literature while there is no common and satisfying treatment for unstable sacral fractures. Because of the posterior pelvic rings special anatomic conditions a local plate osteosynthesis seems to be advantageous. In many fields of modern fracture treatment locking implants show superior results. The prototype of a local locking plate osteosynthesis was compared to a common local plate and two sacroiliac screws.

Methods: The implants were tested using six plastic models of the pelvis and three embalmed human specimens. A Tile C1 fracture was created by disruption of the pubic symphysis and a transforaminal osteotomy. The specimens were exposed to axial loading in an upright single-leg stance with a maximum of 800 N for the plastic models and 200 N for the human specimens. An ultrasonic-based measuring system recorded translations (X, Y, Z) and rotations (alpha, beta, gamma). Parameters such as pattern of motion, translation/rotation, load to failure and remaining dislocation were evaluated.

Results: Concerning most of the evaluated parameters the local plate osteosynthesis was inferior compared with two sacroiliac screws. There were no significant differences between the locking implant and the local plate osteosynthesis. Compared with the two sacroiliac screws the locking implant shows biomechanically equal results but allows greater anterior rotation and remaining dislocation. Because of the lower bone quality, the results from the anatomic specimen tested were not utilisable.

Conclusions: The locking implant is biomechanically an alternative compared with two sacroiliac screws. Problems occurred due to the preset direction of the locking head screws.