Tumeurs malignes osseuses du genou : exérèse et reconstruction

Both the distal femur and the proximal tibia are the preferential site of primitive malignant bone tumours, particularly adolescents' osteosarcomas. Total knee replacement is the gold standard when the tumour spreads to the epiphysis, when it is aggressive and extracompartimental. The prosthesis used in such case is the cemented press-fit of which the long centromedullar stems rest onto the healthy side of the isthmus. The joint is a hinge which may be rotational or not. In femoral lesions without joint invasion, in case of subtotal excision of the quadriceps, an extensor mechanism must be reconstructed, by transfer of the ischii and leg muscles. Surgery by antero-medial access allows controlling the vasculonervous pedicle. In tibial tumours, special attention must be paid to soft tissues, for the front prosthesis coverage (made using a medial gastrocnemius flap) and the extensor kinematization as well. If a part of the patellar ligament has been preserved, it is sutured on the biceps tendon after transferring both the osteotomized fibula and the medial gastrocnemius. If full excision of the patellar ligament has been performed, a combined composite prosthesis is used, that permits re-inserting the patient's extensor mechanism on the extensor mechanism of the allograft. In case of joint invasion, arthrectomy is necessary, using a total composite prosthesis with extensor allografting. After two decades of such reconstructive prostheses use, their long-lasting and satisfactory functional results following extensor reconstruction are confirmed and allow considering this therapeutic procedure even in young and active subjects. Biological reconstruction is recommended in patients with preserved epiphysis and joint (chondrosarcomas, metaphysis limited osteosarcomas). In femoral tumours, medial vascularized fibulas are used for reconstruction, with complementary lateral allografting. Plating is used for osteosynthesis. In tibial tumours, maintaining the allograft by a fixed nail may be effective. Arthrodeses are limited to some rare cases such as athletes, hard-working subjects, or major infectious risk. Today, prostheses are far more frequently used than arthrodeses. Owing to long-lasting effects, biological therapy is recommended provided it is compatible with satisfactory carcinologic excision. Such exeresis and reconstruction surgical procedures showed good oncologic and functional results, but interventions were complex, necessitating frequent resumptions. This surgery can be undertaken only by trained surgical teams, familiar with this type of prostheses, flap use, and vascularized bone transfers.