[Biomechanical stability study on different internal fixation for acetabular fracture].

OBJECTIVE: To investigate the biomechanical stability of the acetabular fracture with three different internal fixation methods.

METHODS: Sixteen both-column acetabular fracture models were randomly divided into three groups:The specimens of 16 hip joints were randomly divided into 4 groups. Among them, 1 group of complete acetabulum were used as normal control group, and the other 3 groups simulated two column fracture models and were fixed in the following methods, respectively: anterior wall with screw and posterior with plate(SP), anterior wall with plate and posterior wall with screw(PS) and both wall with plate (PP). The degree of fracture displacement and the contact characteristics of the acetabulum were recorded by continuous vertical loading.

RESULTS: The mean longitudinal displacement under the load 800 N of SP, PS and PP three groups were (1.92±0.81), (2.09±1.13) and (3.44±0.75) mm, there was significant difference between SP and PP group ( P= 0.033). And the mean horizontal displacement of SP, PS and PP three groups were(0.63±0.33), (0.77±0.45) and (1.44±0.56) mm, there was significant difference between SP and PP group( P= 0.047).Compared with normal control group in the acetabular area under the loading 800 N, the contact area of SP, PS and PP groups were increased by 6%, 9% and 27%, there was significant difference between PP and normal control group ( P= 0.027). Meanwhile, the mean stress of SP, PS and PP groups were increased by 4%, 29% and 39%, there was significant difference between PP and intact acetabulum group ( P= 0.003).

CONCLUSIONS: Anterior column screw combined with posterior column plate has better biomechanical stability and contact characteristics than other two methods.