Stress fracture in acetabular roof due to motocross: case report

[Contact characteristics research of acetabular weight-bearing area with different internal fixation methods after compression fracture of acetabular dome]

Objective

To establish the model of compression fracture of acetabular dome, and to measure the contact characteristics of acetabular weight-bearing area of acetabulum after 3 kinds of internal fixation.

Methods

Sixteen fresh adult half pelvis specimens were randomly divided into 4 groups, 4 specimens each group. Group D was the complete acetabulum (control group), and the remaining 3 groups were prepared acetabular dome compression fracture model. The fractures were fixed with reconstruction plate in group A, antegrade raft screws in group B, and retrograde raft screws in group C. The pressure sensitive films were attached to the femoral head, and the axial compression test was carried out on the inverted single leg standing position. The weight-bearing area, average stress, and peak stress were measured in each group.

Results

Under the loading of 500 N, the acetabular weight-bearing area was significantly higher in group D than in other 3 groups ( P<0.05), and the average stress and peak stress were significantly lower than in other 3 groups ( P<0.05). The acetabular weight-bearing area were significantly higher in group B and group C than in group A, and the average stress and peak stress were significantly lower than in group A ( P<0.05). There was no significant difference in the above indexes between group B and group C ( P>0.05).

Conclusion

For the compression fracture of the acetabular dome, the contact characteristics of the weight-bearing area can not restore to the normal level, even if the anatomical reduction and rigid internal fixation were performed; compared with the reconstruction plate fixation, antegrade and retrograde raft screws fixations can increase the weight-bearing area, reduce the average stress and peak stress, and reduce the incidence of traumatic arthritis.