The objective of this study was to determine the peak contact pressure with varying degrees of articular cartilage step-off in a transtectal acetabular fracture model.
Five fresh frozen cadaveric hip joints were potted in a custom loading fixture. The five specimens were then tested at loads of 445 N (newton) (100 lb) and 1,335 N (300 lb) intact and after a transverse osteotomy at step-off levels from 0 to 5 mm in 1-mm increments.
Articular cartilage step-off of greater than 1 mm led to significantly increased contact stress at the loaded acetabular articular surface. Mean peak pressure measured at 1,335 N of loading in all intact specimens before the osteotomy was approximately 10 MPa. Peak pressure after a transverse acetabular fracture did not change when the fracture was perfectly reduced. At 1 mm of step-off, the peak pressure increased by approximately 20% but was not statistically significant. With step-off of > 2 mm or greater, the peak pressure increase was approximately 50% and was statistically significant.
On the basis of our study, transverse acetabular fractures with greater than 1 mm of displacement can lead to significant increase in peak pressure at the articular surface.