OPERATIVE TECHNIQUE AND TECHNICAL POINTS OF COMPUTER ASSISTED PELVIC RECONSTRUCTION

Abstract

Surgical treatment of pelvic injuries is one of the most challenging tasks in trauma surgery. Intra-operative two-dimensional imaging technology can often not cope with the complex requirements of the three-dimensional anatomy of the pelvis. A registration, which is difficult to achieve with minimal invasive techniques, is obligatory for the CT-based navigation. Changes in the reduction can only be visualized inadequately. The intra-operative imaging after completed osteosynthesis has significantly enhanced since the introduction of three-dimensional image amplifiers. The three-dimensional data can be used directly for the visualization of the osteosynthesis material by linking it to a navigation system.

Since January 2001 the Trauma Center Ludwig-shafen has the ability to perform the registration-free three-dimensional navigation by linking the 3D image intensifier to a navigation system. From January 2002 to January 2005 30 patients with a pelvic injury, where the intra-operative navigation was carried out with the 3D image intensifier, were included in a prospective study. A complete neurological status, conventional fluoroscopic diagnosis, and CT-images were available pre-operatively for all patients. This information formed the basis for the classification and indication for surgery. Patients were positioned on a metal-free carbon table. Due to the registration-free navigation, and thus without the need for a manual registration of landmarks, a tissue-saving preparation could be performed. The postoperative assessment of the implant position was carried out by an independent radiologist.

Screw placement on the pelvic ring was performed in 23 patients (IS lag screws), in 3 patients on both sides. Periacetabular screws were implanted in 7 patients with acetabular fractures. A prerequisite was that the closed repositioning and a temporary fixation could be carried out before the recording of the 3D dataset. 7 surgeons participated in this study. The 3D image intensifier and the navigation system were always operated by the same person. In total 66 screws were implanted (49 IS screws, 17 periacetabular screws). One misplacement of a IS screw with a penetration of the neuroforamen was found during post-operative check-ups. The screw position was corrected during revision surgery. The mean fluoroscopy time for the recording of the 3D scans and the 2D check-ups was 1.78 (+/− 0.4) min. The mean operating time was 105 (+/− 24) min.

This prospective study demonstrated the clinical use of navigation in a three-dimensional dataset from the 3D image intensifier with automatic registration on the pelvis. A relatively high misplacement ratio during IS lag screw placement in the traditional, percutaneous technique according to Matta up to 30% is described in literature. The 3D image intensifier navigation facilitates a standardized working process in the operating room. This is reflected in the low range in fluoroscopy and operating time. The limiting factor in pelvic surgery is the relatively small image volume of the 3D image intensifier of 12 cm3 and the low image quality compared to a CT.