Achieving precise open reduction and fixation of acetabular fractures by using a plate osteosynthesis is a complex procedure. Increasing availability of affordable 3D printing devices and services now allow to actually print physical models of the patient's anatomy by segmenting the patient's CT image. The data processing and printing of the model however still take too much time and usually the resulting model is rigid and doesn't allow fracture reduction on the model itself.

Our proposed solution automatically detects relevant structures such as the fracture gaps and cortical bone while eliminating irrelevant structures such as debris and cancellous bone. This is done by approximating a sphere to the exterior surface of a classic segmented STL model. Stepwise, these approximated vertices are projected deeper into any structure such as the acetabular socket or fractures, following a specific set of rules. The resulting surface model finally is adapted precisely to the primary segmented model.

Creating an enhanced surface reconstruction model from the primary model took a median time of 42 sec. The whole workflow from DICOM to enhanced printable 3D file took a median time of 13:25 min. The median time and material needed for the prints without the process was 32:25:36 h and 241,04 g, with the process 09:41:33 h and 65,89 g, which is 70% faster. The price of material was very low with a median of 2,18€ per case. Moreover, fracture reduction becomes possible, allowing a dry-run of the procedure and allowing more precise plate placement.

Pre-contouring of osteosynthesis plates by using these 3D printouts was done for eleven patients prior to surgery. These printouts were validated to be accurate by three experiences surgeons and compared to classic segmented models regarding printing time, material cost and reduction ability. The pre-contouring of the plates was safely achievable. Our results show that improving the operative treatment with the help of enhanced 3D printed fracture models seems feasible and needs comparably little time and cost, thus making it a technique that can easily integrated into the clinical workflow.

Introduction: Percutaneous iliosacral screws are commonly used for the fixation of the posterior pelvis. The procedure is technically demanding because of the limitations of radiological visualisation of the relevant landmarks. There have been several reports of misplaced screws and other complications, occasionally with serious consequences. To achieve a secure surgical procedure we routinely use a CT-guided technique for percutaneous pelvic screw fixation since 2004.

Methods: Between September 2004 and January 2009, 39 patients were treated using CT-guided screw fixation. Under general anaesthesia patients were placed on a vacuum mattress in a stable lateral position within the CT gantry (Siemens SOMATOM definition; i-Fluoro: 20mAs; Hand CARE mode). The scanner bed was on a calibrated track so the same images could be used and repeated throughout the procedure. Gantry and patient were draped under sterile conditions. The laser sights of the CT indicated the cutaneous site which corresponded to the underlying osseous level (first or second sacral pedicle). At this the CT scan trajectory in the CT-fluoro mode indicated the extrapolated position of the guide-wire. A 3.2mm guide-wire was inserted using battery-powered equipment or hammer blows. When the guide-wire was in a correct position a self-drilling cannulated lag screw was placed (6.5mm DePuy). Two screws were inserted in sacral fractures, one screw in sacroiliac ligament ruptures.

Results: 19 of 39 patients were polytraumatized. In 10 cases there were both side injures. Overall 71 screws were placed. Median time for the procedure was 36 minutes in unilateral lesions and 48 min in bilateral lesions. There were no cases of infection, non-union or neurological deficit. Postoperative CT revealed correct screw positions in all cases. Screw removal was done routinely in the patients younger than sixty years to resolve the blocked sacroiliac joint.

Conclusions: CT-guided is a safe and feasible treatment option in patient with instable pelvic ring lesions. A close collaboration between interventional radiologist and surgeon is essential. Compared to other procedures g.e. internal plate fixation or fluoroscopic guided procedures CT-guided screw insertion seems to be more secure and could strongly be advocated.