Expanding prostheses in conservative surgery for lower limb sarcoma.

Conservative resection of bone sarcoma in the lower limbs in children is very likely to be followed by a progressive problem of leg length inequality resulting from removal of the growth cartilage. To overcome this we have been using an expanding prosthesis and we report our experiences during the period 1985-1996. The prostheses are made of titanium and comprise 3 parts: an articular component, an expanding mechanism, and tibial and femoral stems. The degree of possible lengthening of the prostheses is virtually unlimited, and they can be inserted in children of 5 or more years of age. We report the use of 28 prostheses in patients aged from 5 to 18 years, of which 4 were tibial, 5 total femur, and 16 distal femur. There were 6 Ewing's sarcoma, 21 osteosarcoma, and 1 synovial sarcoma. The average follow-up was for 5 years. Five patients died from their disease, and 21 benefited from an average lengthening of 2.6 cm (range: 2 mm-120 mm). Using the Société Européenne des Tumeurs Osseouses (EMSOS) criteria, the functional results were excellent or very good in 16, fair in 7 and bad in 5. Five patients developed an infection; one required amputation and the others received a new expanding prosthesis. We conclude that an expanding prosthesis is an excellent alternative to amputation in young children. However, the risk of infection associated with repeat surgery has led us to develop a prosthesis which can be lengthened externally, without the need for reopening the wound.