[Fixation of acetabular fractures. a novel method of pre-operative Omega plate contouring].

PURPOSE OF THE STUDY The aim of the study was to describe a novel Omega plate and the procedure for obtaining an accurate pelvic inlet view, the mode of pre-operative plate contouring, the surgical procedure used and the evaluation of results in the first 15 patients treated using this method. MATERIAL AND METHODS In the period 2009-2011, a total of 232 patients underwent osteosynthesis for pelvic fractures. Out of them, 52 were treated by the modified Stoppa approach and 12 with the original Omega plate. Between July 2010 and January 2014, a novel 3.5-mm Omega plate was used in 12 men and 3 women. The average duration of follow-up was 8.5 months in 11 patients; four were shortly after surgery. The multi-functional Omega plate is described in detail. An exact pelvic inlet projection, named the "computer tomography-defined (CTD) view", was based on pre-operative CT examination. It facilitates pre-operative contouring of the plate according to a mirror image of the uninjured half of the pelvis. The surgical procedure enables us to apply the contoured plate to the correct position; the plate completes reduction, restores normal pelvic anatomy and makes operative time shorter. The radiographic evaluation of post-operative results was done using the Matta classification and functional outcome was assessed by the Harris Hip Score. RESULTS Surgery using the isolated Stoppa approach was carried out in 11 patients and a procedure combining the Stoppa approach with another method was used in four patients. All operations were successfully completed, during two of them the external iliac vein was injured and treated by vascular suturing. No other vascular or nerve injury occurred. One deep wound infection successfully healed was recorded. The post-operative radiographic results were excellent or satisfactory in 12 and poor in three patients. At follow-ups of 6 to 12 months, no failure of fracture reduction or osteosynthesis was recorded in 11 patients. Neither avascular necrosis of the femoral head nor heterotopic ossification was found. One patient showed signs of post-injury arthritis at 6 months after surgery. The functional result assessed by the Harris Hip Score was excellent in seven patients, good in two (one of them with gonarthrosis), satisfactory in one patient with contralateral total hip replacement and ipsilateral gonarthrosis, and poor in one patient with hemiparesis after a stroke. DISCUSSION Shape and size variability in CTD pelvic inlet views do not allow us to create a unified anatomically correct implant. Contouring during the operative procedure may not be accurate enough and significantly prolongs the time of surgery. Therefore, a custom-made plate for each patient seems to be an optimal method. It has been demonstrated on a group of 50 patients that CTD images of the right and left halves of the pelvis are identical in 68% and very similar (variation in length up to 5 mm and in curvature up to 3 mm) in 18%. At present plate contouring according to a mirror image of the acetabulum, which will be obtained by 3D printing, is prepared. CONCLUSIONS Pre-operative contouring of an Omega plate based on a post-injury CT scan of the uninjured half of the pelvis is over 80% accurate or almost accurate. The multi-functional 3.5-mm pelvic plate Omega allows us to stabilise complicated fractures of the superior ramus of the pubic bone, anterior acetabular column or quadrilateral plate as well as fractures above the linea arcuata or uncomplicated fractures of the posterior column. The stabilisation of all fragments of the anterior column and quadrilateral plate is very firm and the Omega plate is resistant to fragment redisplacement. Also, it is its advantage that it can remain in situ if total hip arthroplasty is required later.