Angular stable plate fixation provides favorable biomechanical stability in simulated T-shaped acetabular fractures: a biomechanical study.

Background and purpose:  The treatment of acetabular fractures remains technically demanding. In the case of reduced bone quality or fracture morphology reducing the amount of bone available for fixation, locking plates should provide considerable advantages. The aim of the present study was to compare conventional and locking plate fixation. It was hypothesized that locking plate fixation provides less displacement and higher construct stiffness.

Methods:  A T-shaped acetabular fracture was simulated in 16 synthetic pelvic models. The fracture was addressed with a biplanar 10-hole 2-column plate buttressing the medial acetabular wall. Optical markers were attached to the fracture sites for motion tracking. Standardization of the acetabulum loading mechanism was performed using a unipolar hemiarthroplasty. The primary outcome measure was displacement at the fracture sites. The secondary outcome measure was the construct stiffness (N/mm).

Results:  Fracture displacement was less in the group of angular stable implants compared with the group fixed with conventional non-locking implants. Under cyclic loading displacement was less in the group of locking plate fixation. No differences in mean initial axial stiffness were detected between locking plate fixation (407 N/mm) and conventional plating (308 N/mm, ∆ 99 N/mm, 95% confidence interval -48 to 245).

Conclusion:  We showed that locking plate fixation buttressing the medial acetabular wall achieved less fracture displacement but showed no differences in axial stiffness compared with conventional plating.