Synergistic Effects of Hydroxyapatite Nanoparticles and Platelet Rich Fibrin on Femoral Head Avascular Necrosis Repair in a Rat Model.

Abstract

Nanomaterials and platelets derivatives provide promising substitutes in regenerative medicine for the management of avascular necrosis of the femoral head (AVN). Thus, this study was accomplished to evaluate the effectiveness of Platelets rich fibrin (PRF) and Hydroxyapatite nanoparticles (HANPs) as innovative strategies for providing immediate mechanical support and protecting the femoral head from collapse in a surgical model of AVN and their influence on optimizing core decompression (CD) via clinical, radiographic, histopathological, and immuno-histochemical analyses. Fifty-six Sprague Dawley rats were divided into four groups. Bipolar electrocoagulation was used to surgically induce AVN by depriving blood flow. HANPs were administered to the ischemic femoral head via CD hole and sealed with PRF gel in the CD-PRF-HANPs treated group, while a CD hole was made and sealed with PRF gel in the CD-PRF treated group. The healing was evaluated at 2- and 8-weeks following surgery clinically, radiographically using Cone beam computed tomography (CBCT), and histopathologically using HE, Masson Trichrome, and Alizarin red S staining's and immunohistochemistry where Osteopontin (OPN) and cluster of differentiation 34 (CD34) were detected. The CD-PRF-HANPs group revealed a significant enhancement in mechanical hyperalgesia compared to the AVN group (p < 0.01) at 2 weeks, with the greatest improvement observed at 8 weeks compared to both AVN (p < 0.0001) and the CD-PRF group (p = 0.0001). It also showed enhanced efficacy in regenerating the ischemic femoral head and maintaining head sphericity, as evidenced by macroscopical images and CBCT measurements. It recorded higher BMD relative to CD-PRF (p = 0.003) at 8 weeks, with complete obliteration of the CD tunnel. In contrast, the AVN group displayed subchondral collapse (crescent sign) at 2 weeks and complete noticeable femoral head deformity, with the lowest CBCT values at 8 weeks (p < 0.0001). Histopathological analysis of the CD-PRF-HANPs group confirmed a significant restoration of normal cortical bone, organized bone lacunae, osteoid matrix, and enhanced mineralization. The AVN group displayed a significant (p < 0.0001) increase in the number of empty lacunae over time, compared to the other groups; in contrast, the CD-PRF-HANPs group demonstrated a significant (p = 0.0005) decrease in the number of empty lacunae compared to the CD-PRF group. Additionally, it exhibited the highest levels of OPN and CD34 (p < 0.0001), indicating a beneficial role in promoting bone matrix deposition, osteogenesis, and angiogenesis, thereby offering enhanced protection and regeneration of the femoral head. In a rat model of AVN, intraosseous administration of HANPs and PRF gel positively influenced the repair of the ischemic femoral head architecture, protected it from accelerated bone turnover, restored joint integrity, and presented a viable therapeutic approach in the early stages of AVN.