Following orthopaedic reconstruction and cranial neurosurgery, spine surgery is now entering its low invasive period. When, in 90’s, computer went routinely available in the surgical field, the main goal was to help surgeons operate on with more accuracy some difficult but standard procedures. The surgery was “computer aided”. The displayed tools on 2D or 3D images allowed surgeons to avoid permanent intra operative landmarks. Once patient personal anatomy was capture into the machine and the tools calibrated, the surgeon was able to plan and optimised ideal trajectories without direct vision to check tools position. “Navigation” starts to be more obvious to describe this intra operative control. Anyway, we still needed large exposure to get the full bone surface in order to build a 3D surface based model. This model optically localised was matched using rigid or elastic algorithm with preoperative CT scan model or bone morphing^®. Ultrasound recognition of the soft tissue/bone interface let think about trans cutaneous palpation. However, automatic segmentation of the bone surface never lead to commercially available soft. Only X-ray is commonly use during surgery to help surgeon to see tools and bone without surgical exposure. Fluoroscopy allows percutaneous trajectory as iliosacral screwing, vertebroplasty, fracture nailing et caetera. Radiation exposition could therefore be an issue for patient but also for surgeon. Fluoronavigation is a good response to percutaneous surgery. In spine no transversal view could be available. Surgeons should make mental reconstruction of the volume to perform the right trajectory. Industrial proposed intra operative tomography on C-arm with 3D reconstruction. It works well for limbs, but in thoracic and lumbar spine the large amount of surrounding soft tissues leads to low quality images. Flat panel X-ray receptor are a path to get more accurate images. Other perspectives are circular intra CT scan. The cost and the volume of machines stops the spread of such device.

Robots are used by knee surgeons but abandoned by hip surgeons. In spine tool holder robot are available in order to place a pedicular drill guide. Matching with bone is based on fluoroscopy.

Spine navigation could be useful to e-leaning and simulators too. The training of percutaneous surgery is long, because of mental matching between fluoroscopic 2D projections and the vertebra volume. We need a simulator allowing 3D virtual trajectory checked on AP and lateral view to short the learning curve.

Purpose of the study: We describe a surgery navigation system based on virtual fluoroscopy images established with a 3D optic localizer. The purpose of this work was to check the accuracy of the system for posterior spinal implants in comparison with conventional surgery. Duration of radiation and duration of surgery were compared.

Material and methods: A 3D optic localizer was used to monitor the position of the instruments in the operative field, as well as the fluoroscopy receptor. The surgeon took two views, ap and lateral, with a total exposure of two seconds. The C arm was then removed. After image correction, the ap and lateral views were displayed on the work station screen where the computer superimposed to tools on each image. Twenty osteosynthesis procedures for implantation of pedicular screws via a posterior approach to the thoracolumbar spine were performed with this virtual fluoroscopy technique (20 patients, 68 screws). During the same study period, twenty other procedures were performed with the conventional technique (ap and lateral x-ray with the C-arm after drilling the pedicle, 20 patients, 72 screws). The position of the spinal implants was compared between the two series on the ap and lateral views and postoperative CT. Similarly time of exposure to x-rays and duration of the surgical procedure were recorded.

Results: The rate of strictly intrapedicular implantation was less than 8% (5/68 screws) in the virtual fluoroscopy series versus 15% (11/72 screws) in the conventional series. Time of exposure to radiation was significantly lower in the virtual fluoroscopy series with a 1 to 3 improvement (3.5 s versus 11.5 s on average) over the conventional method. With training, this method is not more time consuming (10 min per screw for the conventional method versus 11.25 min for virtual fluoroscopy).

Discussion and conclusion: Compared with conventional fluoroscopy, the virtual technique enables real time navigation while significantly reducing the dose of radiation, both for the patient and the surgery team. There are two types of advantages of virtual fluoroscopy over CT-based systems: first virtual fluoroscopy is immediately available without specific preoperative imaging and secondly it provides real non-magnified images acquired once during the procedure, after which the C-arm is removed. 3D virtual fluoroscopy is probably the next step but requires further experience.

Purpose: The purpose of this work was to evaluate clinical and radiological results of surgical treatment of 80 calcaneum fractures involving the posterior talar process using 1/4 tubes used for triangulation fixation.

Material and methods: The series involved 73 patients (seven bilateral fractures), 56 men and 17 women, average age 39.6 years (15–67) who were treated between 1990 and 1999. Patients were victims of 34 home accidents (46.6%), 19 sports accidents (26%), 14 occupational accidents (19.2%), and six traffic accidents (8.2%). The Duparc classification was: type 2 (n=2) type 3 (n=17), type 4 (n=51), and type 5 (n=10). Junior surgeons performed most of the procedures who used seven ‘inverted-V’ assemblies and 73 triangular assemblies. Forty-two patients (47 fractures) were reviewed (58.8% of fractures) clinically and radiologically to assess stability of the fixation (Boehler angle and talocalcaneal angle) and search for osteoarthritis.

Results: Mean follow-up was six years (1.5–11.5). There were few complications: four late healing (5%), five reflex dystrophy (6.3%) and two infections (2.5%) (Met-S Staphylococcus aureus and Bacterium bovis corineus. Subjectively, 93.5% of patients were satisfied or very satisfied. At last follow-up, the Boehler angle was 27.5±6.7°. The subtalar space was normal or nearly normal in 46.8% and narrowed or destroyed (osteoarthritis) in 53.2%. The Kitaoka function score (AOFAS) was 73.2 points on average with 44.7% excellent or good results and 44.8% fair results. The SOFCOT score was very good, good, or rather good in 63.8% and fair in 10.3%; it was also noted that among the 25.5% poor results, three patients required secondary subtalar arthrodesis. 86% of the patients resumed their occupational activities and 63% of the patients practicing sports resumed their activities.

Conclusion: Osteosynthesis of calcaneum fractures using 1/4 tubes used in a triangular configuration provides stable fixation (little secondary loss of Boehler angle) with a satisfactory cutaneous impact (few cases of skin necrosis). The subjective outcome is very satisfactory. Objective outcome may appear disappointing but is generally related to the severity of the fracture (76% types 4 and 5) or type of fixation configuration.

Purpose: The purpose of this work was to study the reliability and the precision of a lumber vertebra reconstruction method using images obtained from a 3D statistical model and two calibrated radiograms. The technique is designed for surgical approach to the lumbar spine and implantation of osteosynthesis material using enhanced-reality technology.

Material and methods: A lumbar vertebra was reconstructed on several specimens using images issuing from a 3D statistical model and two calibrated radiograms. The images obtained from the model of this lumbar vertebra to be reconstructed constituted the preoperative images. Intra-operative images corresponded to two calibrated radiograms acquired with a fluoroscope using advanced technology (silicium receptor). The model was equipped with reflecting patches which can be detected in space using a 3D optical system. Correspondence between the 3D statistical model and the two calibrated radiograms was achieved with appropriate software. Navigation views were displayed on the screen to guide surgical tools at the vertebral level. Pedicular screws were implanted into several anatomic specimens to evaluate the reliability and precision of the system. The exact position of the implanted screws was established with computed tomography.

Results: This system demonstrated its reliability and precision for the reconstruction of a lumbar vertebra from a 3D statistical model and two calibrated radiograms. All the implanted screws were perfectly positioned in the pedicles. Precision was to the order of 1 mm.

Discussion: This method is a passive system not requiring intraoperative intervention. Reconstruction of a lumbar vertebra from a preoperative 3D statistical model and two intra-operative calibrated radiograms avoids the need to identify anatomic landmarks and/or surface points on the vertebra to be reconstructed. The level of precision is very similar to that obtained with CT-based systems. Preoperative CT is not needed for navigation.

Conclusion: With this system, new generation fluoroscopic equipment should appear in the operating room, allowing acquisition of successive calibrated images. The digital data could then be matched with statistical anatomic data, avoiding the need for preoperative imaging (CT or MRI). Progressive introduction of intra-operative ultrasound to replace the calibrated radiograms should open a new approach for percutaneous surgery of the lumbar spine.