骶髂螺钉的正确打法

Injury,Int.J.Care Injured(2004)35,S-A46—S-A56

0020–1383/$—see front matterß2004Published by Elsevier Ltd. doi:10.1016/j.injury.2004.05.010

For musculoskeletal tumor resections, it is rather difficult to define the exact resection line because normal and cancerous bone can hardly be differenti-ated in most cases. With exact resection, however, the preservation of osseous structures, eg, parts of the sacrum, is possible as well as preservation of nerve roots.

Navigation procedures based on CT data are well proven in spinal surgery. With reduced radiation exposure, the precision can be enhanced [3]. In our own clinical practice, CT-based navigation is part of the clinical routine for dorsal spine instrumenta-tion. Between May and December 2000, 124 out of 126 pedicle screws inserted in the thoracic spine were placed correctly [13]. Based on these good experiences, CT-based navigation was used in pelvic surgery as well.

Fluoroscopy-based n avigation o ffers t he a dvantage that the fluoroscope is already present in the operat-ing room (OR) and current images can be acquired whenever needed. Up to four C-arm projections can be displayed simultaneously on the navigation screen. Therefore, no intraoperative re-orientation of the fluoroscope is needed. After experimental definition of adequate fluoroscopy projections for five typical pelvic screws [12], fluoroscopy-based navigation was used in the clinical set-up. Modality-based navigation uses a specially de-signed and equipped CT-suite as an OR. Navigation is performed on the basis of the CT data with the possibility of immediate CT-control of the reduction and the navigation procedure as well.

The clinical experiences with the different naviga-tion techniques in pelvic surgery are described with a particular focus on indications, operative technique, and limitations.

Methods an d r e l e van t in d ica t i o n s Between June 1st, 2000 and December 31st, 2002 there were 41 percutaneous screw fixations per-formed with either CT- or fluoroscopy-based navi-gation.

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820836 n1121941 T able 1: Indications for navigated screw fixations.

Three musculoskeletal tumors were resected us-ing CT-based navigation. There were two chordomas of the sacrum and one Ewing sarcoma of the iliac wing.

CT-ba sed naviga t i o n

For CT-based navigation, the CT-based spine module of Medivision® can be used. CT data with at least 2mm slices was transferred to the workstation. Within the 3-D reconstruction, the reference points for the paired point matching have to be defined and the preoperative planning performed. For per-cutaneous procedures, we recommend positioning the reference points along the iliac crest, which is easily accessed with small skin incisions. In addition to the palpable anterior superior iliac spine, ad-ditional points in a defined distance along the iliac crest are recommended. Marker screws can be used but have the disadvantage of an additional operative procedure before the CT. For tumor resections, the reference points were defined within the operative area. For surface matching, 15–20 points were ac-quired with the pointer. These points were located in the area of the reference points or in the operative area as well. After successful matching and verifi-cation, the navigated procedure was started. The fluoroscope was left in the OR-setup for the whole procedure to enable intraoperative control of the position of the guided instruments.

Flu o r os c o py-ba sed naviga t i o n

A conventional fluoroscope was used (Ziehm®) and the C-arm navigation module was from Medivision®. Optoelectronic markers were mounted onto the instruments, the dynamic reference base, and the fluoroscope. An infrared camera assessed the posi-tion in space. Up to four fluoroscopy projections can be displayed simultaneously on the navigation screen. The direction and length of the navigated drill or drill sleeve can be followed on the screen and thus be controlled in all four projections without additional imaging.

S et-up(Fig.1)

All navigated procedures need to be planned in advance regarding the set-up in the OR. For navi-gated pelvic surgery, the optoelectronic camera is positioned at the feet of the patient with about 2 m distance to the dynamic reference base, mostly mounted in the iliac crest of the side to be operated