Retrieved bone-anchored percutaneous amputation prosthesis showing maintained osseointegration after 11 years—a case report

Abstract

The patient is a woman born in 1960. She suffered a high transfemoral amputation due to a tumor in 1976. In 1993, she was enrolled for treatment with a custom-designed bone-anchored implant solution. The surgery was performed in 2 stages, Briefly, at stage 1 of surgery (S1), a titanium fixture was implanted in residual femoral bone after reaming of the intramedullary canal, and using a 3-D centering guide and fluoroscopy to ensure proper positioning. At stage 2 of surgery (S2) 6 months later, a full skin thickness flap was trimmed of subcutaneous fat and sutured to the distal end of the femoral bone, essentially according to the surgical technique developed for percutaneous bone-anchored hearing aids (Tjellstrom 1989). In conjunction with S2, a skin-penetrating abutment was inserted into the fixture and secured via an abutment screw. Following S2, the rehabilitation included a gradual increase of the load on the implant, the fitting of an external prosthesis to the abutment, increased activity, and prosthetic use. In 1998, the titanium fixture fractured at the distal end, and a custom-made abutment was installed to try to avoid fixture removal. This abutment failed in 2000, and was exchanged. In 2004, the fixture fractured again due to fatigue, and it was removed. The distal part was loose and was easily removed, while the proximal part was drilled out with a trephine burr together with a surrounding tissue collar. The fixture with surrounding bone was immersed in 4% formalin. The patient was successfully revised with a new implant and has not suffered from any new fracture. Specimen preparation The specimen was dehydrated and embedded in LR White (London Resin Co. Ltd., UK) and divided into 2 pieces through the long axis by use of a diamond band saw. One part was used for preparation of a toluidine blue stained ground section for histological and histomorphometrical analysis using light microscopy. The counter part of the block was divided further into one smaller part at the apical end, containing 7 threads intended for micro-CT analysis in a Skyscan 1172. The rest was polished with grit paper to create an even surface, and then sputter-coated with gold (approximately 10 nm) and analyzed by scanning electron microscopy (SEM).