EXPANDABLE ENDOPROSTHETIC RECONSTRUCTION OF THE SKELETALLY IMMATURE AFTER MALIGNANT BONE-TUMOR RESECTION

The mainstay of local control of primary bone malignancies in the skel etally immature has been amputation or, in selected cases, rotationpla sty. The development of expandable endoprostheses has permitted an alt ernative approach for local control in the growing child. Between Janu ary 1985 and December 1987, 12 skeletally immature patients with prima ry malignant bone tumors were treated with extremity reconstruction wi th cemented custom-expandable endoprostheses after wide resection of t heir lesions. All patients were observed until death (four) or revisio n (two) with a minimum two-year follow-up period for the survivors (av erage, 3.1 years). Seven patients have undergone a total of 11 expansi ons and one patient was lengthened with a revision-expandable prosthes is. Four patients have not needed expansion. Eight patients have had a total of ten complications. Seven of the ten complications (70%) were prosthesis related and associated with failure of the expansion mecha nism. The Musculoskeletal Tumor Society (MSTS) overall rating was good to excellent in seven patients (58%), fair in three (25%), and poor i n two (17%). In five distal femoral arthroplasties and one total femor al arthroplasty where the tibial bearing component was cemented throug h the physis, tibial and epiphyseal growth was observed to be normal a nd equal to the nonoperative side. This suggests that partial central epiphyseal and physeal ablation does not cause physeal arrest. Althoug h the high rate of expansion mechanism failure necessitates redesign, preliminary results suggest that expandable endoprostheses do offer an alternative to amputation and rotationplasty as a means of local cont rol and extremity reconstruction in children with primary malignant bo ne tumors.