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Abstract
Primary malignant bone tumours account for approximately 6% of all cancers in children younger than 20 years of age. The two predominant primary bone malignancies are Osteosarcoma which accounts for 60% of newly diagnosed cases, and Ewing’s sarcoma, which accounts for an additional 34%. Over the past two decades, amputations have been performed less frequently for upper and lower extremity bone tumors and have provided the oncologic surgeon with the challenge of reconstructing large segmental bone and/or joint deficicts created by limb sparing tumor resections.(14)
The success of limb salvage is the result of advances in the understanding of the biology and staging of tumours, improvement in the reconstructive techniques, and the development of effective adjuvant chemotherapy for the primary tumors. The patients can be expected to have long-term survival, which is due, in particular, to the advances in chemotherapy.(8)
Many elements can affect successful outcome in pediatric orthopaedic oncologic care, including patient age, diagnosis, anatomic location, stage of disease, and socioeconomic factors. A proper management strategy can be devised only after careful deliberation by all members of the treatment team as well as the patient and family. In these discussions, prioritizing the goals of a multidisciplinary program is essential. These goals, in order, are (1) life, (2) limb function, (3) limb (4) leg-length equalization, and (5) cosmetic appearance. Because of the complex nature of the decision-making process and the risky nature of the surgery, referral of pediatric patients with a malignant neoplasm to oncologic centers is strongly recommended.(1)
The challenge of preserving the limb of a skeletally immature patient with primary bone sarcoma includes:
a) maintenance of limb length after resection of one or more major growth plates as appositional and longitudinal bone growth is expected in the immature skeleton. The amount of bone growth that can be expected from each growth plate has been estimated. Generally, about 60% to 70% of lower limb growth occurs around the knee and about 80% of total growth of the humerus occurs in the proximal physis of the humerus. The severity of limb length discrepancy after excision of a major growth plate depends on the patient’s bone age.(5)
b) the need to use a durable reconstruction that can cope with the high functional and recreational demands of young patients, particularly now that most of the patients are expected to survive their disease because of the availability of effective chemotherapy.(5)
Limb length discrepancy in children is generally progressive until skeletal maturity. Treatment decisions depend on the predicted limb-length discrepancy at skeletal maturity. Accurate prediction of the discrepancy is therefore important. The multiplier method allows for a quick calculation of the predicted limb-length discrepancy at skeletal maturity. This method is independent of percentile groups and is the same for prediction of femoral, tibial, and total limb lengths. The multiplier values are also independent of generation , height , socioeconomic class, ethnicity, and race.(19)
Options for reconstruction in the skeletally immature patients include:
1) Expandable prosthesis: where the lengthening occurs through activation of an internal device by an external electromagnetic field, thus eliminating the need for an open surgical procedure.(Michael D. Neel, et al, 2001).
2) Various types of bone grafts: either allograft or autograft.
3) Rotationplasty: where the tibia is rotated 180o and fused to the femur, with the ankle joint placed at the level of the contralateral knee. It creates a functional below-knee amputation.(Matthew R.Dicaprio et al.,2003).
4) Contralateral epiphysiodesis: which is the controlled arrest of the growth in the physis of a skeletally immature patient for management of discrepancies 2-5 cm.(20)