Biomechanical Study On Different Both Anterior And Posterior Internal Fixation Methods Of Acetabular Transverse Fracture

Objectives To compare the biomechanical stability of acetabular transverse fracture which fixed with three both anterior and posterior internal fixation methods and two single column internal fixations. And by using pressure sensitive film technology, this research investigated the contact characteristics of hip joint by the changes on the loading area, mean pressure and peak pressure in the dome region after fixed with different internal fixation methods in transverse acetabular fracture models.To discuss the characteristics of the both anterior and posterior internal fixation methods as to provide theoretical basis for clinical application.Methods Pressure-sensitive films were used to measure the loading area, the mean pressure and the peak pressure in the dome region of twenty specimens. Prepared twenty adult antiseptic semi-pelvis specimens to this study then divided them into five groups randomly and acetabular transverse fractures were induced in those five groups. The anterior columns were fixed with locking reconstruction plates in group X1; The posterior columns were fixed with locking reconstruction plates in group X2.The anterior columns were fixed with locking reconstruction plates and the posterior columns were fixed with lag screws in group A; The anterior columns were fixed with lag screws and the posterior columns were fixed with locking reconstruction plates in group B; The double columns were fixed with lag screws in group C. When loading three times as much weight, measured each group of the loading area, the mean pressure and the peak pressure, the benched displacement and the fissured displacement by pressure-sensitive films and grating displacement transducer. The shear rigidity and axial rigidity were computed by the benched displacement and fissured displacement. To compare the differences of biomechanical stability between both anterior and posterior internal fixation method and single column internal fixation method and to evaluate the effect of the contact characteristics of hip joint.Results Under the load of three times as much weight, the loading area, the mean pressure and the peak pressure in the dome region in five intact specimen groups were undifferentiated. After induced acetabular transverse fracture models which were fixed by different internal fixation methods, the loading area, the mean pressure and the peak pressure in the dome region in five groups were differentiated, among them, in the groups of internal fixation specimens,the loading area of A, B and C were larger than X1, X2(P< 0.05), after the intact specimens and internal fixation specimens measured by pair t test, the loading area of five internal fixation groups were smaller than their intact specimens(P< 0.05), in the groups of internal fixation specimens, the mean pressure of A, B and C were smaller than X1, X2(P< 0.05), after the intact specimens and internal fixation specimens measured by pair t test, the mean pressure of five internal fixation groups were larger than their intact specimens(P< 0.05), in the groups of internal fixation specimens, the peak pressure of A, B and C were smaller than X1,X2(P< 0.05), after the intact specimens and internal fixation specimens measured by pair t test, in the groups of internal fixation specimens, the peak pressure of X1,X2 and A were larger than their intact specimens(P< 0.05). When loading three times as much weight, both benched displacement and fissured displacement of different internal fixation specimens were differentiated(P< 0.05), X2 were larger than X1(P< 0.05), X1, X2 were larger than A, B and C(P< 0.05); both shear rigidity and axial rigidity of different internal fixation specimens were differentiated(P<0.05), A, B and C were larger than X1, X2(P< 0.05).Conclusions 1. For acetabular transverse fractures, the contact characteristics of hip joint could not recovery even the fractures were anatomical reduction. 2. Anterior column locking reconstruction plate and posterior column locking reconstruction plate had similar contact characteristics of hip joint, the biomechanical stability of anterior column locking reconstruction plate were better than posterior column locking reconstruction plate. 3. Anterior column locking reconstruction plate plus posterior column lag screw, anterior column lag screw plus posterior column locking reconstruction plate and double columns lag screws had similar contact characteristics of hip joint and biomechanical stability. 4. Compared the single column fixation method, both anterior and posterior fixation method could offer the most close to normal of contact characteristics of hip joint and better biomechanical stability.