Uncemented short‐length diaphyseal segmental replacement prosthesis fixation—Finite element analysis and long‐term results

Abstract

Introduction: Extensively porous coated segmental replacement prostheses with intramedullary cementless fixation to bone over the whole length of stem often exhibit resorption of the surrounding bone due to stress-shielding. This makes them particularly susceptible to aseptic loosening.Study: A finite element analysis of the state of loading of a short-length fixation in a new prosthetic stem design has shown a definite advantage over long-length fixation. The stress pattern within the bone surrounding the prosthesis confirmed that shortening of the-ongrowth area in length increases the stress values at the resection level significantly. This stem (Endlock) has been used for diaphyseal anchorage in the treatment of tumors in combination with an artificial joint of proven design in order to reduce stress shielding.Results: No Endlock stem fractures or aseptic loosenings were observed at recent follow-up. The early clinical results comply with the theoretical assumptions.Conclusions: A short-length fixation system based on intramedullary anchorage of segmental replacement endoprostheses would possibly support physiologic adaptive processes more than fixation over the full length of the stem.

Variation in bone response to the placement of percutaneous osseointegrated endoprostheses: A 24-month follow-up in sheep

“…As seen in sheep radiographs (Fig 4, Animal A), distal loading and distal fit that avoids complete proximal fill of the medullary canal should be considered an essential element of design and is necessary for conservation and preservation of host bone. This observation is also supported by the previous reports of various clinically implemented endoprosthesis designs [37–39]. In one study, Werner and his co-authors concluded that a partially coated prosthesis with short segmental distal intramedullary fixation ensured more physiologically adaptive remodeling compared to the fully coated endoprosthesis systems.…”

Bone growth in rapid prototyped porous titanium implants

“…This stress shielding effect results in bone resorption significantly affecting the long‐term performance of the implants 3. Finite element modeling (FEM) has shown that both the strength and Young's modulus of a metal may be controlled by its porosity 6–8. It ought, therefore, to be possible to match the strength and elastic modulus of bone by using porous titanium implants.…”

Periprosthetic fracture caused by stress shielding after implantation of a femoral condyle endoprosthesis in a transfemoral amputee—a case report

“…Extensively coated femoral stems, such as the FCE, will have a more pronounced bone loss than proximally or partially coated stems (Bobyn et al 1992, Blunn et al 2000, Yamaguchi et al 2000, Werner et al 2005). …”