Aim. The use of megaprostheses for knee reconstruction after distal femur resection in young bone sarcoma patients has become popular since early ′80. The authors reviewed their experience with different distal femur megaprostheses in children. Method. Clinico-radiographic evolution in a consecutive series of 113 children, that had implanted below age 15 (range 6-14) a distal femur megaprosthesis in the period 1984-2007, was analized. A modular implant was used in 97 cases with uncemented femoral stem (three different models along the period). The implant presented fixed-hinge joint in 78 cases while rotating-hinge knee was utilized in 19 cases. In 39 cases the fixed-hinge joint had a tibial component with a polished stem to allow the residual growth of proximal tibia; in two cases a mechanically extendable prosthesis was used. A custom-made noninvasive extendable prosthesis with cemented femoral stem and smooth uncemented tibial stem was used in 15 cases since 2002. Radiological and functional results were analysed and a statistical comparison of implant outcome according different stems was obtained. Results. At a 74 months follow-up (29-294), 72 patients are alive; but 43 of them (60%) had further surgery related to primary implant. Surgical revision rate was 88% (39% for mechanical failure) in long survivors treated before 1995 and 50% (14% with mechanical failure) in more recent cases (p< 0.05). Three long survivors progressed in time to total femur megaprostheses. Five out the 15 cases treated by custom made expandable prostheses were revised before completion of skeletal growth because of implant failure. Conclusion. In limb-salvage for bone sarcoma, megaprostheses are the preferred method to reconstruct distal femur in growing children, but a durable reconstruction is not easy to be achieved. The use of new devices specially addressed to younger patients deserves a serious scientific survey by musculoskeletal oncology community

In skeletally immature patients, resection of bone tumours and reconstruction of the lower limb often results in leg-length discrepancy. The Stanmore non-invasive extendible endoprosthesis, which uses electromagnetic induction, allows post-operative lengthening without anaesthesia. Between 2002 and 2009, 55 children with a mean age of 11.4 years (5 to 16) underwent reconstruction with this prosthesis; ten patients (18.2%) died of disseminated disease and one child underwent amputation due to infection. We reviewed 44 patients after a mean follow-up of 41.2 months (22 to 104). The mean Musculoskeletal Tumor Society score was 24.7 (8 to 30) and the Toronto Extremity Salvage score was 92.3% (55.2% to 99.0%). There was no local recurrence of tumour. Complications developed in 16 patients (29.1%) and ten (18.2%) underwent revision.

The mean length gained per patient was 38.6 mm (3.5 to 161.5), requiring a mean of 11.3 extensions (1 to 40), and ten component exchanges were performed in nine patients (16.4%) after attaining the maximum lengthening capacity of the implant. There were 11 patients (20%) who were skeletally mature at follow-up, ten of whom had equal leg lengths and nine had a full range of movement of the hip and knee.

This is the largest reported series using non-invasive extendible endoprostheses after excision of primary bone tumours in skeletally immature patients. The technique produces a good functional outcome, with prevention of limb-length discrepancy at skeletal maturity.