INTRODUCTION

Bone tumour resection and subsequent reconstruction remains challenging for the surgeon. Obtaining adequate margins is mandatory to decrease the risk of local recurrence. Improving surgical margins quality without excessive resection, reducing surgical time and increasing the quality of the reconstruction are the main goals of today's research in bone tumour surgical management. With the outstanding improvements in imaging and computerised planning, it is now a standard. However, surgical accuracy is essential in orthopaedic oncologic surgery (Grimmer 2005). Patient specific instruments (PSI) may greatly improve the surgeon's ability to achieve the targeted resection. Thanks to its physical support, PSI can physically guide the blade yielding to a better control over the cutting process (Wong, 2014). Surgical time might significantly be reduced as well when compared to conventional method or navigated procedure. Finally, reconstruction may gain in rapidity and quality especially when allograft is the preferred solution as PSI can be designed as well for allograft cutting (Bellanova, 2013). Since 2011, PSI have systematically been used in our institution for bone tumour resection and when applicable allograft reconstruction. This paper reports the mid- to long-term medical outcomes on a large series.

Purpose of the study: Resection of sarcomas from the pelvis is particularly difficult because of the risk of injury to the vascular and neurological structures and the complex helicoidal anatomy of the iliac bone. Salvage of the lower limb is preferable but raises the risk of an insufficient resection margin. Imaging procedures (CT scan, magnetic resonance) allow preoperative planning but intraoperative landmarks are not always easy to recognise. Navigation might be highly useful for this type of surgery.

Material and methods: Two patients with a sarcoma of the pelvis (chondrosarcoma and synovial sarcoma) underwent tumour resection using a navigation system. For the second patient, the cut for the bone graft was also navigated enabling reconstruction with a perfectly adjusted graft. The tumour was delimited on each magnetic resonance slice to produce a 3D reconstruction image. This volume was co-recorded on the scanner. The scan with the tumour limits was fed into the navigation machine. Resection planes were chosen taking into account the surgical approach, the type of reconstruction desired, and the healthy margin accepted. These planes were then transposed onto the allograft scan to enable an exactly adapted cut. Plaster prototypes were modelled from the scan of the patient’s pelvis and the allograft scan. The tumour resection and the allograft procedures were repeated on the prototypes using the navigation system.

Results: The navigation system was used successfully as planned preoperatively. The planes of the cuts were as planned. The healthy margin was sufficient in all cases and confirmed at the pathology exam.

Discussion: Navigation enables exact localisation in relation to the tumour throughout the operation. A healthy margin of one centimetre or more can be achieved safely. The allograft cut can be made by another surgeon simultaneously with the tumour resection, saving time. The allograft-host contact surface is improved giving a good congruency with the graft.

Conclusion: Navigation is a very useful tool for resection of pelvic tumours and their reconstruction.