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Oncology

LONG TERM RESULTS OF AN ELECTROMAGNETIC NON-INVASIVE EXPANDABLE PROSTHESE, AFTER RESECTION OF THE KNEE IN 27 CHILDREN

The European Musculo-Skeletal Oncology Society (EMSOS)



Abstract

Expandable prostheses were designed to allow progressive growth after tumour resection in children. The aim of this study was to report the late results of the non-invasive growing prostheses designed by A Soubeyran (Phenix prosthesis or Wright Repiphysis).

From 1994 to January 2006, 27 children aged 4 to 12 (mean 8.5), underwent a resection of the knee for a bone tumour, with reconstruction by a non invasive expandable prosthesis. There were 16 boys and 11 girls. The tumours were 25 osteosarcomas and 2 Ewing tumours. All patients received pre and post-operative chemotherapy. There were 18 distal femur, 7 proximal tibia, and 2 femur + tibia resections.

There were different successive designs based on the same electro-magnetic growing mechanism using a pre bent spring, released by eating in an induction coil.

After, 7.2 years mean follow-up (4 months to 15 years), 20 patients had no evidence of disease and 7 were deceased. Two with a local recurrence were amputated. Mean lengthening was 5.1 centimeters (0 to 8), after 3 to 11 lengthening procedures. Mean limb-length discrepancy was 1.8 cm. Two patients had a secondary infection. Eleven had a revision for arthrofibrosis. All surviving patients were revised to a conventional hinged prosthesis. The mean MSTS functional score of the definitive prosthesis was 82% (63 to 96%).

Theses prostheses showed many mechanical complications as loosening, fracture of the growing mechanism, and arthrofibrosis. The positive outcome was the possibility to perform a progressive lengthening, without surgery limiting the risk of infection. Theses prostheses should be considered as temporary until reconstruction with a conventional hinged prosthesis. Patients with multiple revisions had a tendency to show less favourable late functional results than with primary implanted hinged prosthesis.