The development of new image techniques enables the early detection of bone tumors in the extremities in the past two decades. In addition, new advance of adjuvant therapy improves the long-term survival of patients with primary bone malignancies. Since the primary bone malignancy frequently occurs at the metaphysis of long bones of pediatric patients in the first and second decade, many patients have to face the late problems of limb length discrepancy after the limb salvage operation. Since the inevitable limb length discrepancy will interfere the functional outcomes and cosmetic appearance, the reconstruction of limb defect after limb salvage remains a challenge. Several options of reconstruction are available for these patients, including resection arthrodesis, rotationplasty, osteochondral allograft reconstruction, and endoprosthetic reconstruction. All these methods are difficult to address the limb length discrepancy. The development of expandable endoprosthetic reconstruction makes limb-salvage surgery feasible in the skeletally immature and provides another choice of solution. This article presents the current status of custom-expandable endoprosthetic reconstruction in the skeletally immature patients after wide resection of primary bone malignancies in the extremity. The surgical options, complications and functional results will be emphasized. Basically these expandable endoprostheses can be classified according to the expansion design. Recent reports demonstrated that the results of expandable prosthesis in the growing children are rather acceptable. Some patients can regain the equal limb length after expansion of the prosthesis. However these patients have to take several expansion procedures for the equality of limb length during the growing period. A rather high complication rate of either endoprosthesis-related or disease-associated still needs to be settled in the near future. These include mechanical failure of the expansion mechanism, extensive metallosis, aseptic loosening, fatigue fracture, flexion contracture, local recurrence, delayed wound healing, fat embolism, local overgrowth of counterpart bone, nerve palsy, infection, and bone fracture. Some patients even require an amputation even after expandable endoprosthesis reconstruction because of difficult reconstruction or severe functional impairment. However, with regard to difficult rehabilitation for patients under 8 years, amputation or alternative options need to be considered. A comprehensive discussion with the parents and patient about the detailed treatment protocol is needed before performing reconstruction using expandable endoprosthesis.
Non-invasive distal femoral expandable endoprosthesis for limb-salvage surgery in paediatric tumours