Using three-zone flexible cones at the metaphyseal-diaphyseal junction may avoid the need for distal femoral replacement: The floating cone technique.
Case Report
Distal femoral replacement (DFR) with megaprostheses is a salvage revision total knee arthroplasty (rTKA) procedure indicated in cases with massive bone defects in the distal femur. As long as these implants achieve fixation only in the diaphysis, the high aseptic loosening rate reported in some series is probably related to a lack of rotational stability. Two patients with extensive distal femoral bone defects with preservation of the metaphyseal-diaphyseal junction underwent rTKA. Instead of performing a DFR with megaprostheses, partially impacted three-zone cones and standard cemented hinged implants were used with the aim of achieving better rotational stability. Both patients showed good evolution after a 12-month follow up. Clinical findings included a normal range of motion (0-100°) without any instability and preserved ability for full weight-bearing ambulation. No signs of prosthetic loosening appeared in the X-rays during follow up. To our knowledge, this was the first time a single partially anchored three-zone cone was used in massive metaphyseal femoral defects. It is an implant-dependent technique that additionally requires the preservation of the metaphyseal-diaphyseal junction, but may avoid the use of megaprostheses in some cases.
