No effect of hydroxyapatite particles in phagocytosable sizes on implant fixation: An experimental study in dogs

Abstract

The influence of wear debris on bone healing around orthopedic implants is debated. Hydroxyapatite (HA) particles and polyethylene (PE) particles have been shown to have a negative effect on osteoblast cultures in vitro. The present study investigated the in vivo effects of HA and PE particles on the mechanical fixation and gap healing around experimental HA implants. Nonloaded implants (n = 30) were inserted bilaterally into the proximal tibia of 15 dogs with a 2-mm gap to the bone. The peri-implant gap was either (1) empty (n = 6) or filled with (2) hyaluronic acid (n = 8), (3) hyaluronic acid and HA particles (n = 8), or (4) hyaluronic acid and PE particles (n = 8). After 4 weeks, the animals were killed. The implant interface was evaluated by pushout testing until failure and by histomorphometry. Both HA and PE particles were found to be phagocytosed by macrophage-like cells in the interfacial tissue. HA particles were also integrated in newly formed bone. We found no negative effect of the particulate material on mechanical fixation of the implants or on bone formation around the implants.

Allocation of nonbirefringent wear debris: Darkfield illumination associated with PIXE microanalysis reveals cobalt deposition in mineralized bone matrix adjacent to CoCr implants

“…It is still unknown if the deposition of cobalt takes place via linked osteocytes or osteoblasts phagocytize particles, which then infiltrate bone tissue during formation of new bone. [47][48][49] Furthermore, it is still uncertain whether deposition of cobalt in bone tissue is a continuous process, whether it reaches a ''saturation point,'' or whether there is a correlation between the concentration of cobalt and certain lysis zones in the implant bearing. 50 Further investigations will be necessary to determine if a continuous release of alloying components (heavy metals) leads to detrimental alterations and remodeling of mineralized bone tissue.…”

Free or fixed state of nHAP differentially regulates hBMSC morphology and osteogenesis through the valve role of ITGA7

“…Free HAP has been reported to induce proinflammatory and osteoclastogenic effects on human mononuclear cells and negatively regulate the proliferation of osteoblasts in vitro [ 25 ]. Other studies reported that free HAP did not support bone healing and growth in vivo [ 26 ]. In contrast, Yao et al injected a free-flowing calcium phosphate material into the mice osteoporotic tibia in order to remineralize the collagen fibrils, and revealed that the repaired bones exhibit satisfactory mechanical performance comparable with normal bones [ 3 ].…”

Particulate gold as an anti‐inflammatory mediator in bone allograft—An animal study

“…The study was designed to imitate a cementless joint replacement with the implant inserted at the center of an oversized drill hole in cancellous bone and surrounded by morselized allograft. The model is highly standardized and reproducible and allows a well‐controlled amount of added treatment substance to the peri‐implant tissue,21–23 in this case gold particles. The paired study design also permits direct comparison within animals, thereby minimizing the number of animals needed.…”