Potential for supraphysiologic fluid shear stresses in a rat cemented knee replacement model

Abstract

The mechano-biologic environment associated with aseptic loosening of cemented joint replacements is not fully understood. The goal of this study was to use a preclinical rat knee arthroplasty model to explore the changes in cement−bone morphology and micromotion that occur with in vivo service. Narrow gaps between cement and bone under the tibial tray were present at early time points, and with even small magnitude micromotion, resulted in large micromotion-to-gap width ratios. These data were then used to develop models of fluid flow in the cement−bone gaps to estimate potential for high fluid shear stress (FSS). Modeling results revealed supraphysiologic (>4 Pa) FSS were possible, particularly for cases in which eccentric loading applied to the implant and if the fluid in the gap consisted of marrow or synovial fluid. The early, high FSS environment, could cause fluid-induced periprosthetic osteolysis locally, resulting in progressive loss of cement−bone fixation.

Friend or foe? Inflammation and the foreign body response to orthopedic biomaterials

“…Interestingly, a joint fluid is the product of SLIM. 70,78 Current evidence suggest that activated fibroblasts trigger and perpetuate the inflammatory state upon the detection of pathological stimuli. 79 These cells are master immune regulators affecting the final F I G U R E 3 Initiation and perpetuation of chronic inflammation begins years before apparent aseptic loosening (AL) occurs.…”

“…In this line, the processes leading to development of PPOL and AL show a very complex interaction between chronic inflammation driven mainly by the foreign body response and mechanical forces either associated with repetitive joint fluid pumping or development of harmful stress–strain patterns at the bone‐implant‐soft tissue interfaces (Figure 3). Interestingly, a joint fluid is the product of SLIM 70,78 …”

Effect of cortical bone thickness on shear stress and force in orthodontic miniscrew-bone interface – A finite element analysis

“…Most of the studies focused on equivalent stress in orthodontic miniscrewbone assembly [13-15, 17, 23, 24]. Few studies addressed the shear stress in orthopaedic implants [25,26]. To the best of our knowledge, no studies are available on the shear stress in orthodontic miniscrewbone assembly.…”

Mechanical loading intensities affect the release of extracellular vesicles from mouse bone marrow‐derived hematopoietic progenitor cells and change their osteoclast‐modulating effect

“…However, how changes in loading intensity changes the EV release with an osteoclast‐modulating effect has not been investigated. Nevertheless, it is well established that different loading intensities affect bone remodeling differently, for example, unloading, physiological loading, and supraphysiological loading 23,27–30 . Unloading (Stress shielding, SS) results from either physical inactivity such as extended bed rest 31 or stress shielding caused by orthopedic or dental implant designs that shield bone from mechanical loading 32 .…”

“…Nevertheless, it is well established that different loading intensities affect bone remodeling differently, for example, unloading, physiological loading, and supraphysiological loading. 23,[27][28][29][30] Unloading (Stress shielding, SS) results from either physical inactivity such as extended bed rest 31 or stress shielding caused by orthopedic or dental implant designs that shield bone from mechanical loading. 32 We simulated this loading through a static culture that lacked any active mechanical loading (0.0 ± 0.0 Pa, 0 Hz).…”