Abstract
Nowadays 80% of patients with bone sarcomas can benefit from limb salvage. Their disease-free life expectancy is not jeopardised by conservative surgery as long as safe margins are obtained. For this reason, the oncological result relies on the accuracy of pre-operative and per-operative surgical measurements. Pre-operative evaluation of tumours is now quite accurate with digital margins (computed tomography, MNR, digital angiography). However, surgeons are still using centimeters or conventional radiographs with their own technical limitations for per-operative evaluation. A more accurate technique is needed.
The system is composed of three components: 1) a color, graphic computer workstation with software to calculate and present the location of the surgical instrument on a three-dimensional, reconstructed bone image, 2) a complete set of hand-held instruments containing infrared emitters, 3) an infrared receiver linked to the work station. This measuring system enables determination of the position and incidence of a surgical instrument in real time during surgery, with an accuracy of less than one mm.
The system requires four steps: 1) recording data with C.T., N.M.R. or angiography, 2) creating a three-dimensional image displayed on the computer screen for preoperative simulation of a virtual operation, 3) recording the very important anatomical points of the patient and optimal incidences of the surgical instruments, 4) preoperative location of surgical instruments and control of their location on bone.
This system is very useful for resection of bone tumours when the conventional location is uncertain (innonimate bone, rib), when very sharp accuracy is needed to preserve the growth plate of the distal femur in young children, and to avoid medullary damage in a spinal tumour.
The frameless stereotactic device is also very accurate in the reconstructive phase of limb salvage. After an internal hemipelvectomy, the device permits localisation of the acetabular prosthesis in the precise location before resection.
In our practice, the accuracy of the video guiding system is always within two mm as compared to conventional measurements usually between one or two cm for long bones and three to five cm for innominate bone.
The use of a video guidance system is very beneficial for limb salvage surgery for pelvic bone tumours.
The abstracts were prepared by David P. Davlin. Correspondence should be addressed to him at the Orthopedic Clinic Bulovka, Budínova 2, 18081 Prague 8, Czech Republic.
