Modes of Failure of Custom Expandable Repiphysis Prostheses

Abstract

Limb preservation surgery for patients with sarcomas of the extremity is recognized as a valid, safe, and effective means of treating local disease1. However, one of the major dilemmas in lower limb preservation in skeletally immature children is the ability to maintain leg-length equality as the child ages and grows. Many prosthetic designs that allow expansion of the internal prosthesis and consequent limb-lengthening, either noninvasively or through a minor surgical procedure, have evolved2,3. One of the latest of the noninvasive expandable implants is the Repiphysis expandable limb salvage system (Wright Medical Technology, Arlington, Tennessee), originally called the Phenix prosthesis (Phenix Medical, Paris, France)4,5. Although used in Europe since the early 1990s, the first Phenix prosthesis was implanted in the United States in 1998, and in 2002, the device became approved by the Food and Drug Administration. While this system offers many advantages over earlier expandable limb salvage implants, we observed three failures among sixteen Repiphysis prostheses implanted (in fourteen patients) between 2003 and 2010 by the senior author (R.M.H.). The patients and their parents were informed that the data concerning these cases would be submitted for publication, and they consented. Case 1. An eight-year-old girl was diagnosed as having stage-IIB osteosarcoma, according to the Musculoskeletal Tumor Society (MSTS) system developed by Enneking et al.6, in the distal end of the left femur. A wide local resection was done at another institution with limb reconstruction with use of a Lewis Expandable Adjustable Prosthesis (LEAP, Wright Medical Technology) with an expansion capacity of 2.5 cm. Two years later, she presented to us with a fixed knee flexion deformity of 80° and an inability to bear weight on that leg because of the deformity and limb-length discrepancy. Following serial casting to …