Comparative strength of three methods of fixation of transverse acetabularfractures

With the advent of percutaneously placed lag screws for fixation of acetabu lar fractures, this study evaluated the strength of lag screw fixation comp ared with traditional fixation techniques of transverse acetabular fracture s. Ten formalin-treated human, cadaveric pelvic specimens with bilateral, t ranstectal transverse acetabular fractures were used for this study. The ri ght acetabular fractures were fixed with a five-hole plate and four screws with the central hole spanning the posterior fracture site. The left acetab ular fractures were fixed with two lag screws, one each in the anterior and posterior columns, or with a screw and wire construct stabilizing both col umns. The specimens were loaded to implant failure. Stiffness, yield streng th, maximum load at failure, and site of failure was recorded. The plate an d screw construct showed significantly greater yield and maximum strength w hen compared with the two lag screws. The stiffness of the lag screw method was 39% higher than that of the plating method, but this result was not st atistically significant. In addition, the plate and screw method provided s ignificantly greater maximum strength than the screw and wire technique. Th e quadrilateral plate seemed to be the weakest area of fixation because 83% of the implant failures occurred in this region. In patients in whom the r isks of formal open reduction and internal fixation of acetabular fractures outweigh the possible benefits, such as in patients with burns or degloved skin, the advent of computer-assisted and fluoroscopically guided percutan eous surgical techniques have been instrumental. This study showed there is greater strength of fixation with a plate and screw construct, possibly se condary to supplementary fixation distal to the quadrilateral plate. Howeve r, lag screw fixation provided relatively greater stiffness, which may acco unt for its clinical success. Percutaneous lag screw fixation of appropriat e transverse acetabular fractures is a viable option.