Fracture at the stem–condylar junction of a modular femoral prosthesis in a varus–valgus constrained total knee arthroplasty

Abstract

Case report, Level IV.

The role of complex clinical scenarios in the failure of modular components following revision total knee arthroplasty: A finite element study

“…Based on the evidence in both cases, failure at the modular junction was attributed to aseptic loosening of the femoral component distally in combination with a weakening of osseous support, as suggested by the apparent bone loss under the implants visible from patient radiographs. Similarly, Nikolopoulos et al reported a single case of modular junction failure in a cemented stemmed revision prosthesis attributed to loss of fixation through poor cementing of the prosthesis and a lack of cancellous bone support at the time of revision implantation. This numerical study strongly supports the assertion that lack of osseous support leads to high junction stresses, a loss of metaphyseal fix was also found to increase stresses at the modular junctions, though not to the same extent as a lack of osseous support.…”

“…Previous clinical case studies have indicated that a lack of osseous support, in combination with loss of metaphyseal fixation, might be a key factor in the failure of modular components . In a recent retrieval study, Issack et al reported two cases of failure at the modular taper lock of constrained condylar prostheses with large diameter stems and distal femoral augments.…”

“…In all cases, a Poisson's ratio of 0.3 was assumed for all materials. Many clinical studies have hypothesized that weak osseous support, which can occur as a result of disease or through implant induced stress shielding, may lead to failure of the stem‐junction . To test this hypothesis, a variation of the distal femur model was constructed which incorporated extremely reduced bone quality for both cancellous and cortical regions (“compromised metaphysis”) as shown in Figure .…”

“…The increase in number of junctions and joints per complex implant assembly for example create more potential sites for loosening or failure. A number of recent studies have documented such failures . In these studies, failures ranged from complications due to loosening of locking screws and femoral stem disengagement to full catastrophic failure of the prosthesis at the stem–implant interface .…”

“…A number of recent studies have documented such failures . In these studies, failures ranged from complications due to loosening of locking screws and femoral stem disengagement to full catastrophic failure of the prosthesis at the stem–implant interface . Failure or fracture of the stem–implant junction is thought to be the result of weak osseous support or loosening of the prosthesis distally.…”