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.

Introduction. Following bone tumour resection, lower limb reconstruction results in leg-length discrepancy in skeletally immature patients. Previously, minimally invasive endoprostheses have been associated with a high risk of complications including joint stiffness, nerve injury, aseptic loosening and infection. The purpose of this study was to examine the outcome of the Stanmore non-invasive extendible endoprostheses used in our institution between 2002 and 2009 and compare them with implants used in the past. Methods. Fifty-five children with a mean age of 11.4 years (5 to 16) underwent limb reconstruction with thirty-three distal femoral, two total femoral, eight proximal femoral and twelve proximal tibial implants. Forty-six endoprostheses were lengthened in clinic without anaesthesia using the principle of electromagnetic induction. Patients were assessed using the Musculoskeletal Tumour Society Score (MSTS) and the Toronto Extremity Salvage Score (TESS). Results. Ten children (18.2%) died of disseminated disease. One child underwent amputation for infected prosthesis. Forty-four patients were reviewed after a mean follow-up of 41 months (16 to 98). The mean MSTS score was 80.7% (26.7-100) and the TESS score was 92.3% (55.2-99). There was no local tumour recurrence. Complications developed in sixteen patients (29.1%). Seven patients (12.7%) underwent ten revision procedures. The mean length gained per patient was 38.6mm (3.5 to 161.5) requiring a mean of 11.3 (1-40) extensions. Ten component exchanges were performed in nine patients (16.4%) after attaining the maximum lengthening capacity of the implant. Eleven patients (20%) were skeletally mature at follow-up, of which ten had equal leg-lengths and nine had full range of hip and knee movement. Overall our outcomes compared favourably with minimal endoprostheses and other non-invasive designs. Discussion. This is the largest reported series of non-invasive extendible endoprostheses, demonstrating good functional outcome with prevention of limb-length discrepancy at skeletal maturity