Low-intensity pulsed ultrasound enhances bone repair in a rabbit model of steroid-associated osteonecrosis

Osteogenic effect of low-intensity pulsed ultrasound on peri-implant bone: A systematic review and meta-analysis

Purpose This study aimed to evaluate the effect of low-intensity pulsed ultrasound (LIPUS) on promoting osseointegration around dental implants.Study selection A comprehensive search was performed on two databases, including MEDLINE (PubMed) and Web of Science to identify relevant studies published before June 1, 2022. Randomized controlled trials that met the inclusion criteria were selected for the study. The year of publication, study design, animal species, number of animals, number of implants, implant position, implant size, intervention, follow-up time, bone volume ratio (BV/TV), bone-implant contact ratio (BIC), and implant removal torque value (RTV) measurements, including mean and SD, were extracted.Results Ten randomized trials were included in this meta-analysis. The results showed that LIPUS significantly promoted osteogenesis around dental implants. Furthermore, in animal models of pre-existing diseases such as osteoporosis and diabetes, LIPUS had the same effect. The included data were divided into subgroups to explore the effects of different follow-up time, acoustic intensities, and frequencies. Results showed that higher acoustic intensities and frequencies significantly improve the osteogenic effects of LIPUS. There was some degree of heterogeneity owing to bias in the included studies. More high-quality randomized controlled trials are necessary in the future.Conclusions LIPUS can promote bone healing around dental implants and is an attractive option for edentulous patients, especially those with pre-existing diseases. Further clinical trials on the use of LIPUS in implant dentistry are warranted. Furthermore, future studies must pay more attention to acoustic intensity and frequency.

Selenium nanoparticles/carboxymethyl chitosan/alginate antioxidant hydrogel for treating steroid-induced osteonecrosis of the femoral head

Oxidative stress plays a crucial role in steroid-induced osteonecrosis of the femoral head (SONFH). Although several antioxidant strategies have been investigated for treating SONFH, their antioxidant efficiencies and therapeutic effects remain unsatisfactory. Here, we developed a selenium nanoparticles/carboxymethyl chitosan/alginate (SeNPs/CMC/Alg) antioxidant hydrogel and evaluated its ability to treat SONFH. In vitro assays indicated that the SeNPs/CMC/Alg hydrogel exhibited excellent properties, such as low cytotoxicity, sustained SeNPs release, and favorable antioxidant activity. Under oxidative stress, the SeNPs/CMC/Alg hydrogel promoted reactive oxygen species (ROS) elimination and enhanced the osteogenic and proangiogenic abilities of bone marrow mesenchymal stem cells (BMSCs). After establishing a rabbit model of SONFH, the SeNPs/CMC/Alg hydrogel was transplanted into the femoral head after core decompression (CD) surgery. Radiographic and histological analyses revealed that the hydrogel treatment alleviated SONFH by eliminating ROS and promoting osteogenesis and angiogenesis compared to those in the CD and CMC/Alg groups. In vitro and in vivo studies indicated that the Wnt/β-catenin signaling pathway was activated by the SeNPs/CMC/Alg hydrogel in both hydrogen peroxide-conditioned BMSCs and necrotic femoral heads. These findings indicate that local transplantation of the SeNPs/CMC/Alg hydrogel is beneficial for treating SONFH, as it promotes ROS elimination and activation of the Wnt/β-catenin signaling pathway.

Dimethyloxallyl glycine-loaded mesoporous bioactive glass/poly(D,L-lactide) composite scaffolds with ultrasound stimulation for promoting bone repair

Introduction: Bone tissue engineering is considered the ideal approach for bone repair. Mesoporous bioactive glass (MBG) possesses the characteristics of high drug-loading capacity and bioactivity. Low-intensity pulsed ultrasound contributes to promoting fracture healing and bone defect repair, and dimethyloxalyl glycine (DMOG) is a small molecular inhibitor that can suppress prolyl hydroxylase, reducing the degradation of hypoxia-inducible factor. Methods: In this study, we proposed to prepare DMOG-loaded MBG/poly(D,L-lactide) composite scaffolds (DMOG-MBG/PDLLA) for promoting bone repair. The effects of ultrasound stimulation and DMOG release on the cell responses of rat bone marrow mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) and bone repair in vivo were investigated. Results and Discussion: The results showed that both ultrasound stimulation and DMOG release could promote the proliferation, adhesion and differentiation of BMSCs and HUVECs, respectively. After the implantation of scaffolds in rat cranial bone defect model for 8 weeks, the results indicated that the combined ultrasound stimulation and DMOG release contributed to the highest ability for promoting bone repair. Hence, the DMOG-MBG/PDLLA scaffolds with ultrasound stimulation are promising for application in bone repair.

Musculoskeletal Biomaterials: Stimulated and Synergized with Low Intensity Pulsed Ultrasound

Clinical biophysical stimulating strategies, which have significant effects on improving the function of organs or treating diseases by causing the salutary response of body, have shown many advantages, such as non-invasiveness, few side effects, and controllable treatment process. As a critical technique for stimulation, the low intensity pulsed ultrasound (LIPUS) has been explored in regulating osteogenesis, which has presented great promise in bone repair by delivering a combined effect with biomaterials. This review summarizes the musculoskeletal biomaterials that can be synergized with LIPUS for enhanced biomedical application, including bone regeneration, spinal fusion, osteonecrosis/osteolysis, cartilage repair, and nerve regeneration. Different types of biomaterials are categorized for summary and evaluation. In each subtype, the verified biological mechanisms are listed in a table or graphs to prove how LIPUS was effective in improving musculoskeletal tissue regeneration. Meanwhile, the acoustic excitation parameters of LIPUS that were promising to be effective for further musculoskeletal tissue engineering are discussed, as well as their limitations and some perspectives for future research. Overall, coupled with biomimetic scaffolds and platforms, LIPUS may be a powerful therapeutic approach to accelerate musculoskeletal tissue repair and even in other regenerative medicine applications.

Bone tissue engineering for treating osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a devastating and complicated disease with an unclear etiology. Femoral head-preserving surgeries have been devoted to delaying and hindering the collapse of the femoral head since their introduction in the last century. However, the isolated femoral head-preserving surgeries cannot prevent the natural progression of ONFH, and the combination of autogenous or allogeneic bone grafting often leads to many undesired complications. To tackle this dilemma, bone tissue engineering has been widely developed to compensate for the deficiencies of these surgeries. During the last decades, great progress has been made in ingenious bone tissue engineering for ONFH treatment. Herein, we comprehensively summarize the state-of-the-art progress made in bone tissue engineering for ONFH treatment. The definition, classification, etiology, diagnosis, and current treatments of ONFH are first described. Then, the recent progress in the development of various bone-repairing biomaterials, including bioceramics, natural polymers, synthetic polymers, and metals, for treating ONFH is presented. Thereafter, regenerative therapies for ONFH treatment are also discussed. Finally, we give some personal insights on the current challenges of these therapeutic strategies in the clinic and the future development of bone tissue engineering for ONFH treatment.

Role of low-intensity pulsed ultrasound in regulating macrophage polarization to accelerate tendon-bone interface repair

Low-intensity pulsed ultrasound (LIPUS) has been proven to accelerate the healing of the tendon-bone interface (TBI), and macrophages are considered to play an important regulatory role. This study was designed to explore the polarization of macrophages during treatment of TBI injury with LIPUS. In a rat model of rotator cuff tear, LIPUS or mock sonication (controls) was administered from 1 week postoperatively. The supraspinatus-supraspinatus tendon-humerus complexes were harvested for further evaluation at different time points for measures such as new bone formation, TBI maturity, ultimate failure load and stiffness, and types of macrophages. In vitro, bone marrow-derived macrophages were cultured, and polarization was identified after stimulation with or without LIPUS (the LIPUS or control groups, respectively). Two weeks posttreatment, the LIPUS group showed higher bone volume/total volume ratios and better TBI maturity scores. Six weeks posttreatment, the failure load of the LIPUS group was significantly higher than that of the control group. LIPUS also accelerated initial inflammatory macrophage accumulation and facilitated anti-inflammatory macrophage polarization (M2) in the late period. In the in vitro macrophage polarization model, the LIPUS group showed a higher proportion of M2 macrophages and mRNA expression of anti-inflammatory genes than the control group, while there was no significant difference in the proinflammatory macrophages between the two groups. Our observations revealed that macrophage polarization may be a potential mechanism of LIPUS treatment for TBI repair.

Low-Intensity Pulsed Ultrasound Promotes Osteogenic Potential of iPSC-Derived MSCs but Fails to Simplify the iPSC-EB-MSC Differentiation Process

Induced pluripotent stem cell (iPSC)-derived mesenchymal stem cells (iMSCs) are a promising cell source for bone tissue engineering. However, iMSCs have less osteogenic potential than BMSCs, and the classical iPSC-EB-iMSC process to derive iMSCs from iPSCs is too laborious as it involves multiple in vitro steps. Low-intensity pulsed ultrasound (LIPUS) is a safe therapeutic modality used to promote osteogenic differentiation of stem cells. Whether LIPUS can facilitate osteogenic differentiation of iMSCs and simplify the iPSC-EB-iMSC process is unknown. We stimulated iMSCs with LIPUS at different output intensities (20, 40, and 60 mW/cm²) and duty cycles (20, 50, and 80%). Results of ALP activity assay, osteogenic gene expression, and mineralization quantification demonstrated that LIPUS was able to promote osteogenic differentiation of iMSCs, and it worked best at the intensity of 40 mW/cm² and the duty cycle of 50% (LIPUS40/50). The Wnt/β-catenin signaling pathway was involved in LIPUS40/50-mediated osteogenesis. When cranial bone defects were implanted with iMSCs, LIPUS40/50 stimulation resulted in a significant higher new bone filling rate (72.63 ± 17.04)% than the non-stimulated ones (34.85 ± 4.53)%. Daily exposure to LIPUS40/50 may accelerate embryoid body (EB)-MSC transition, but it failed to drive iPSCs or EB cells to an osteogenic lineage directly. This study is the first to demonstrate the pro-osteogenic effect of LIPUS on iMSCs. Although LIPUS40/50 failed to simplify the classical iPSC-EB-MSC differentiation process, our preliminary results suggest that LIPUS with a more suitable parameter set may achieve the goal. LIPUS is a promising method to establish an efficient model for iPSC application.

Low Intensity Pulsed Ultrasound for Bone Tissue Engineering

As explained by Wolff's law and the mechanostat hypothesis, mechanical stimulation can be used to promote bone formation. Low intensity pulsed ultrasound (LIPUS) is a source of mechanical stimulation that can activate the integrin/phosphatidylinositol 3-OH kinase/Akt pathway and upregulate osteogenic proteins through the production of cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2). This paper analyzes the results of in vitro and in vivo studies that have evaluated the effects of LIPUS on cell behavior within three-dimensional (3D) titanium, ceramic, and hydrogel scaffolds. We focus specifically on cell morphology and attachment, cell proliferation and viability, osteogenic differentiation, mineralization, bone volume, and osseointegration. As shown by upregulated levels of alkaline phosphatase and osteocalcin, increased mineral deposition, improved cell ingrowth, greater scaffold pore occupancy by bone tissue, and superior vascularization, LIPUS generally has a positive effect and promotes bone formation within engineered scaffolds. Additionally, LIPUS can have synergistic effects by producing the piezoelectric effect and enhancing the benefits of 3D hydrogel encapsulation, growth factor delivery, and scaffold modification. Additional research should be conducted to optimize the ultrasound parameters and evaluate the effects of LIPUS with other types of scaffold materials and cell types.

Cotransplantation of mesenchymal stem cells and endothelial progenitor cells for treating steroid-induced osteonecrosis of the femoral head

Steroid-induced osteonecrosis of the femoral head (ONFH) is characterized by decreased osteogenesis, angiogenesis, and increased adipogenesis. While bone tissue engineering has been widely investigated to treat ONFH, its therapeutic effects remain unsatisfactory. Therefore, further studies are required to determine optimal osteogenesis, angiogenesis and adipogenesis in the necrotic area of the femoral head. In our study, we developed a carboxymethyl chitosan/alginate/bone marrow mesenchymal stem cell/endothelial progenitor cell (CMC/ALG/BMSC/EPC) composite implant, and evaluated its ability to repair steroid-induced ONFH. Our in vitro studies showed that BMSC and EPC coculture displayed enhanced osteogenic and angiogenic differentiation. When compared with single BMSC cultures, adipogenic differentiation in coculture systems was reduced. We also fabricated a three-dimensional (3D) CMC/ALG scaffold for loading cells, using a lyophilization approach, and confirmed its good cell compatibility characteristics, that is, high porosity, low cytotoxicity and favorable cell adhesion. 3D coculture of BMSCs and EPCs also promoted secretion of osteogenic and angiogenic factors. Then, we established an rabbit model of steroid-induced ONFH. The CMC/ALG/BMSC/EPC composite implant was transplanted into the bone tunnel of the rabbit femoral head after core decompression (CD) surgery. Twelve weeks later, radiographical and histological analyses revealed CMC/ALG/BMSC/EPC composite implants had facilitated the repair of steroid-induced ONFH, by promoting osteogenesis and angiogenesis, and reducing adipogenesis when compared with CD, CMC/ALG, CMC/ALG/BMSC and CMC/ALG/EPC groups. Thus, our data show that cotransplantation of BMSCs and EPCs in 3D scaffolds is beneficial in treating steroid-induced ONFH.

Effect of porosity of a functionally-graded scaffold for the treatment of corticosteroid-associated osteonecrosis of the femoral head in rabbits

Background/Objective: Core decompression (CD) with scaffold and cell-based therapies is a promising strategy for providing both mechanical support and regeneration of the osteonecrotic area for early stage osteonecrosis of the femoral head (ONFH). We designed a new 3D printed porous functionally-graded scaffold (FGS) with a central channel to facilitate delivery of transplanted cells in a hydrogel to the osteonecrotic area. However, the optimal porous structural design for the FGS for the engineering of bone in ONFH has not been elucidated. The aim of this study was to fabricate and evaluate two different porous structures (30% or 60% porosity) of the FGSs in corticosteroid-associated ONFH in rabbits.

Methods

Two different FGSs with 30% or 60% porosity containing a 1-mm central channel were 3D printed using polycaprolactone and β-tricalcium phosphate. The FGS was 3-mm diameter and 32-mm length and was composed of three segments: 1-mm in length for the non-porous proximal segment, 22-mm in length for the porous (30% versus 60%) middle segment, and 9-mm in length for the 15% porous distal segment. Eighteen male New Zealand White rabbits were given a single dose of 20 ​mg/kg methylprednisolone acetate intramuscularly. Four weeks later, rabbits were divided into three groups: the CD group, the 30% porosity FGS group, and the 60% porosity FGS group. In the CD group, a 3-mm diameter drill hole was created into the left femoral head. In the FGS groups, a 30% or 60% porosity implant was inserted into the bone tunnel. Eight weeks postoperatively, femurs were harvested and microCT, mechanical, and histological analyses were performed.

Results

The actual porosity and pore size of the middle segments were 26.4% ​± ​2.3% and 699 ​± ​56 ​μm in the 30% porosity FGS, and 56.0% ​± ​4.5% and 999 ​± ​71 ​μm in the 60% porosity FGS, respectively using microCT analysis. Bone ingrowth ratio in the 30% porosity FGS group was 73.9% ​± ​15.8%, which was significantly higher than 39.5% ​± ​13.0% in the CD group on microCT (p ​< ​0.05). Bone ingrowth ratio in the 60% porosity FGS group (61.3% ​± ​30.1%) showed no significant differences compared to the other two groups. The stiffness at the bone tunnel site in the 30% porosity FGS group was 582.4 ​± ​192.3 ​N/mm³, which was significantly higher than 338.7 ​± ​164.6 ​N/mm³ in the 60% porosity FGS group during push-out testing (p ​< ​0.05). Hematoxylin and eosin staining exhibited thick and mature trabecular bone around the porous FGS in the 30% porosity FGS group, whereas thinner, more immature trabecular bone was seen around the porous FGS in the 60% porosity FGS group.

Conclusion

These findings indicate that the 30% porosity FGS may enhance bone regeneration and have superior biomechanical properties in the bone tunnel after CD in ONFH, compared to the 60% porosity FGS.

Translation potential statement

The translational potential of this article: This FGS implant holds promise for improving outcomes of CD for early stage ONFH.

CaO2/gelatin oxygen slow-releasing microspheres facilitate tissue engineering efficiency for the osteonecrosis of femoral head by enhancing the angiogenesis and survival of grafted bone marrow mesenchymal stem cells

The osteonecrosis of femoral head (ONFH), a common refractory disease, is still not fully understood today. Hypoxia caused by ischemia is not only an important pathogenic factor but also a critical challenge for the survival of seed cells in the tissue engineering therapy of ONFH. To explore an efficient strategy to treat ONFH by targeting hypoxia, newly designed CaO₂/gelatin microspheres were composited with 3D printed polycaprolactone/nano-hydroxyapatite (PCL/nHA) porous scaffold, sodium alginate/gelatin hydrogel, and bone marrow mesenchymal stem cells (BMSCs) to develop a novel tissue engineering scaffold and then transplanted into the core depression area of the ONFH rabbit model. The current data demonstrated that CaO₂/gelatin microspheres can constantly release oxygen for 19 days. In vitro assays with BMSCs illustrated that scaffolds have high biocompatibility and are favorable for cell proliferation in extreme hypoxia (1% O₂). The in vivo study demonstrated that the transplanted scaffold with oxygen-generating microspheres significantly enhanced the osteogenic and angiogenic effects compared to the scaffold without microspheres. Further assessments revealed that microspheres in the scaffold can reduce the local cell apoptosis and enhance the survival of grafted cells in the host. Collectively, the present study developed a novel oxygen slow-releasing composite scaffold, which can facilitate tissue engineering efficiency for treating the osteonecrosis of the femoral head by enhancing the angiogenesis and survival of grafted stem cells.

The combination of PLLA/PLGA/PCL composite scaffolds integrated with BMP-2-loaded microspheres and low-intensity pulsed ultrasound alleviates steroid-induced osteonecrosis of the femoral head

Low-intensity pulsed ultrasound (LIPUS), which has been previously reported to promote bone repair, is proposed to be a noninvasive form of therapy for the treatment of osteonecrosis. Bone fillers made from composite scaffolds have been demonstrated to be effective for preventing bone defects such as osteonecrosis. The present study aimed to investigate whether the application of LIPUS combined with bone morphogenetic protein-2 (BMP-2)-loaded poly-L-lactic acid/polylactic-co-glycolic acid/poly-ε-caprolactone (PLLA/PLGA/PCL) composite scaffolds can improve recovery in a rat model of steroid-induced osteonecrosis of the femoral head (ONFH). BMP-2-loaded PLGA microspheres incorporated into PLLA/PLGA/PCL composite scaffolds were constructed. Bilateral femoral head LIPUS intervention was conducted in rats with steroid-induced ONFH. LIPUS intervention alone contributed to the alleviation of osteonecrosis, in addition to improving load-carrying capacity and accelerated bone formation, angiogenesis and differentiation. Subsequently, femoral head parameters and assessment of load-carrying capacity, bone formation-related factors, and angiogenesis- and differentiation-related factors were measured in rats with or without implanted BMP-2-loaded PLLA/PLGA/PCL composite scaffolds. LIPUS combined with the implantation of PLLA/PLGA/PCL composite scaffolds loaded with BMP-2 microspheres protected rats against steroid-induced ONFH and improved load-carrying capacity, bone formation, angiogenesis and differentiation. Together, these data support the use of BMP-2-loaded PLLA/PLGA/PCL composite scaffolds combined with LIPUS for ONFH as a potential alternative curative solution for treating bone diseases.

[A review of mechanisms by which low-intensity pulsed ultrasound affects bone regeneration]

Low-intensity pulsed ultrasound (LIPUS) is a common physical therapy to accelerate the healing of bone fracture and treat delayed union of bone fracture. Vessels, nerves, and bone tissue are essential constituents of bone system. Recently, increasing evidence has been revealed that LIPUS can not only promote bone regeneration by directly regulating osteoblasts, osteoblasts, mesenchymal stem cells, but also have a positive impact on the repair of bone healing through vessels and nerves. Thus, we reviewed and summarized the latest published literature about the molecular mechanism for the effects of LIPUS on bone regeneration, which might offer a promising therapy for bone-related diseases.

Curcumin prevents osteocyte apoptosis by inhibiting M1-type macrophage polarization in mice model of glucocorticoid-associated osteonecrosis of the femoral head

Inflammation is a contributing factor in osteocyte apoptosis, which is strongly associated with the development of glucocorticoid-associated osteonecrosis of the femoral head (GA-ONFH). Curcumin is a naturally derived drug that regulates immunity and inhibits inflammation. This study aimed to examine the capacity of curcumin to prevent osteocyte apoptosis and GA-ONFH, while elucidating possible mechanisms of action. C57/BL6 female mice were divided into control, GA-ONFH, and curcumin-treated GA-ONFH groups. We determined the effect of curcumin on the polarization of RAW264.7 and the apoptosis of MLO-Y4 cells. We found that curcumin reduced the infiltration of M1-type macrophages in the femoral heads and alleviated systemic inflammation in GA-ONFH models. Additionally, curcumin decreased the apoptosis of osteocytes in the femoral heads and the ratio of GA-ONFH in mice. Further, in vitro curcumin intervention inhibited M1-type polarization via the Janus kinase1/2-signal transducer and activator of transcription protein1 (JAK1/2-STAT1) pathway. Taken together, this study demonstrates that curcumin is effective in preventing osteocyte apoptosis and the development of GA-ONFH in a mouse model. Curcumin prevents inflammatory-mediated apoptosis of osteocytes in part through inhibition of M1 polarization through the JAK1/2-STAT1 pathway. These findings provide novel insights as well as a potential preventive agent for GA-ONFH. This article is protected by copyright. All rights reserved.

High Pelvic Incidence Is Associated with Disease Progression in Nontraumatic Osteonecrosis of the Femoral Head

BACKGROUND

Although several factors exacerbate osteonecrosis of the femoral head (ONFH), little is known about whether pelvic sagittal parameters are associated with a greater risk of ONFH progression.

QUESTIONS/PURPOSES

The purpose of this study was to investigate the association between pelvic sagittal parameters and disease progression (collapse of the femoral head) in patients with nontraumatic ONFH.

METHODS

From March 2010 through December 2016, we saw 401 patients with unilateral ONFH diagnosed at an outpatient clinic using plain radiography and MRI that were retrospectively reviewed. Of those, 276 patients met our inclusion criteria: Association Research Circulation Osseous (ARCO) Stage I or II nontraumatic unilateral ONFH without femoral head collapse, older than 18 years, and no prior surgical treatment. In all, 74% (203 of 276) of hips had complete follow-up (clinical and radiographic) at a minimum of 2 years. The pelvic sagittal parameters (pelvic incidence, pelvic tilt, and sacral slope) of all patients were measured with standing radiographs by two observers. Progression of disease and potential collapse of the femoral head of all patients (ARCO Stage ≥ III) was examined using radiography every 2 to 3 months after the first outpatient clinic visit. If patients with intractable pain associated with collapse of the femoral head did not respond to nonoperative treatment, THA was performed during the follow-up period. The patients were divided into two groups for comparison: those whose femoral head collapsed within 12 months (rapid progression group) and those whose femoral head did not collapse (nonrapid progression group). The rapid progression group consisted of 49 men and 55 women with a mean age of 55 years; the nonrapid progression group consisted of 60 men and 39 women with a mean age of 56 years. Factors such as age, sex, BMI, size of necrotic lesions, location of necrosis, necrosis risk factor associated with the rapid progression of disease were analyzed using an exploratory univariate analysis followed by a multivariate analysis.

RESULTS

Pelvic incidence (53° ± 9° versus 49° ± 7°; p < 0.01) and sacral slope (38° ± 9° versus 33° ± 7°; p < 0.01) were greater in the rapid progression group than in the non-rapid progression group. After accounting for potentially confounding variables like age, sex, BMI, size of necrotic lesions, location of necrosis, and necrosis risk factors, the only variable we found that was independently associated with more rapid disease progression was high (> 55°) pelvic incidence (odds ratio, 0.95 [95% CI 0.91 to 0.99]; p = 0.03).

CONCLUSIONS

After controlling for potential confounders such as age, sex, BMI, size of necrotic lesions, location of necrosis, and necrosis risk factors, we found that a high pelvic incidence was associated with a greater likelihood of femoral head collapse in patients with nontraumatic ONFH. Assessing pelvic sagittal parameters in patients with early nontraumatic ONFH may help anticipate which patients are at risk for femoral head collapse, but future prospective studies are needed to confirm these findings.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Motivating role of type H vessels in bone regeneration

Coupling between angiogenesis and osteogenesis has an important role in both normal bone injury repair and successful application of tissue‐engineered bone for bone defect repair. Type H blood vessels are specialized microvascular components that are closely related to the speed of bone healing. Interactions between type H endothelial cells and osteoblasts, and high expression of CD31 and EMCN render the environment surrounding these blood vessels rich in factors conducive to osteogenesis and promote the coupling of angiogenesis and osteogenesis. Type H vessels are mainly distributed in the metaphysis of bone and densely surrounded by Runx2⁺ and Osterix⁺ osteoprogenitors. Several other factors, including hypoxia‐inducible factor‐1α, Notch, platelet‐derived growth factor type BB, and slit guidance ligand 3 are involved in the coupling of type H vessel formation and osteogenesis. In this review, we summarize the identification and distribution of type H vessels and describe the mechanism for type H vessel‐mediated modulation of osteogenesis. Type H vessels provide new insights for detection of the molecular and cellular mechanisms that underlie the crosstalk between angiogenesis and osteogenesis. As a result, more feasible therapeutic approaches for treatment of bone defects by targeting type H vessels may be applied in the future.

Comparative Analysis of the Effect of Two Therapeutic Ultrasound Protocols for Regeneration of a Critical Bone Defect

Objective  To compare the effect of two therapeutic ultrasound protocols, with different times of exposure in the regeneration of critical bone defect. Methods  Forty-five male rats were distributed among three experimental groups: therapeutic ultrasound group 5 minutes (TUG 5); therapeutic ultrasound group 10 minutes (TUG 10); and control group (CG). In all groups, a critical bone defect of 8.5 mm diameter was made in the calvaria region. The protocol was initiated on the 1 ^st postoperative day in TUGs 5 and 10, with therapeutic ultrasound at the frequency of 1.0 MHz, pulsed mode, five times a week, at periods of 15, 30, and 60 days. Results  Among the experimental groups, the highest volume of neoformation of osteoid matrix took place in the TUG 10 group followed by TUG 5, when compared with the CG group, in which the neoformation was restricted to the border region. The use of ultrasound promoted an increase in the thickness of the conjunctive matrix, proliferation of capillaries, alignment of the collagen fibers, reduction of edema and inflammatory process, being more significant in the 10-minutes time period. Conclusion  Therapeutic ultrasound stimulated the repair of a critical bone defect, and the longer exposure time promoted greater osteogenic stimulation.

Low-intensity pulsed ultrasound improves osseointegration of dental implant in mice by inducing local neuronal production of αCGRP

OBJECTIVE

This study aimed to explore the effect of Low-intensity pulsed ultrasound (LIPUS) on implant osseointegration and elucidate the role of α-calcitonin gene-related peptide (αCGRP) in this process.

DESIGN

In vivo, αCGRP^+/+ (Wild-type model) mice and αCGRP^-/- (Knock-out model) mice with implants immediately placed in the maxillary first molars extraction sockets were treated with LIPUS. We detected details of peri-implant bone tissues by micro-CT, real-time PCR and histological analysis. In vitro, αCGRP^+/+ and αCGRP^-/- dorsal root ganglia (DRG) neurons were cultured and exposed to LIPUS. Then conditioned media from these neurons were collected and added to osteoblasts to analyze cell differentiation, mineralization and proliferation by real-time PCR, alkaline phosphatase (ALP) and cell counting kit-8 (CCK-8) assay. Besides, ELISA was performed to determine the effect of LIPUS on the αCGRP secretion in neurons.

RESULTS

In vivo tests revealed that αCGRP^-/- mice displayed worse osseointegration when compared to αCGRP^+/+ mice. LIPUS could enhance implant osseointegration in αCGRP+/+ mice but had little effect on αCGRP^-/- mice. Meanwhile, αCGRP was elevated during the osseointegration with LIPUS treatment. In vitro, LIPUS promoted αCGRP secretion in DRG neurons, thereby enhanced osteogenic differentiation and mineralization of osteoblasts. Also we proved that the effects of LIPUS was duty cycle-related and LIPUS of 80% duty cycle had the strongest impacts.

CONCLUSIONS

Our findings demonstrated that LIPUS could enhance osseointegration of dental implant by inducing local neuronal production of αCGRP, providing a new idea to promote peri-implant osseointegration and bone regeneration.

Low-intensity pulsed ultrasound inhibits VEGFA expression in chondrocytes and protects against cartilage degeneration in experimental osteoarthritis

Low-intensity pulsed ultrasound (LIPUS), a noninvasive physical therapy, was recently demonstrated to be an effective treatment for osteoarthritis (OA). Vascular endothelium growth factor A (VEGFA) has been found to be upregulated in the articular cartilage, synovium and subchondral bone of OA patients, leading to cartilage degeneration, synovitis and osteophyte formation. However, the functions and mechanisms of LIPUS in regulating chondrocyte-derived VEGFA expression are still unclear. In this study, we investigated whether LIPUS attenuated OA progression by (a) decreasing the percentage of VEGFA-positive cells in mouse articular cartilage destabilised through medial meniscus surgery and (b) relieving interleukin-1β-induced VEGFA expression in mouse primary chondrocytes. However, this function was negated by a p38 mitogen-activated protein kinase (p38 MAPK) inhibitor. In addition, we found that LIPUS ameliorated VEGFA-mediated disorders in cartilage extracellular matrix metabolism and chondrocyte hypertrophy during OA development. In conclusion, our data indicate a novel effect of LIPUS in regulating the expression of osteoarthritic chondrocyte-derived VEGFA through the suppression of p38 MAPK activity.

Advances in the understanding of the role of type-H vessels in the pathogenesis of osteoporosis

BACKGROUND

Angiogenesis in the bone and its role in bone metabolic plays a fundamental role in the pathology of osteoporosis. Type-H vessels have been reported to exhibit distinct morphological, molecular, and functional properties. This review is aimed to illustrate the relationship between type-H vessels in the bone and bone metabolism.

METHODS

This manuscript reviews the articles on in vitro and in vivo experiments concerning the topic of type-H vessels and osteoporosis, and other researches in the area published by the author within the time frame from 2014 to 2019.

RESULTS

Current literatures have demonstrated that age-related loss of type-H vessels plays a critical role in the pathogenesis of osteoporosis. Impaired bone mass can be reserved by enhancing the formation of type-H vessels. Activation of the Notch and Hif-1α signaling pathway in bone tissue and exogenous PDGF-BB treatment increase the number of type-H vessels, along with the restoration of bone mass. The effects of osteoblasts and low-intensity pulsed ultrasound (LIPUS) on type-H vessels remain to be further studied.

CONCLUSIONS

These studies support unique functions for type-H vessels in the bone that may enable new therapeutic approaches to osteoporosis.

Effect of leg-length discrepancy following total hip arthroplasty on collapse of the contralateral hip in bilateral non-traumatic osteonecrosis of the femoral head

AIMS

The purpose of this study was to examine whether leg-length discrepancy (LLD) following unilateral total hip arthroplasty (THA) affects the incidence of contralateral head collapse and subsequent THA in patients with bilateral osteonecrosis, and to determine factors associated with subsequent collapse.

PATIENTS AND METHODS

We identified 121 patients with bilateral non-traumatic osteonecrosis who underwent THA between 2003 and 2011 to treat a symptomatic hip, and who also exhibited medium-to-large lesions (necrotic area ≥ 30%) in an otherwise asymptomatic non-operated hip. Of the 121 patients, 71 were male (59%) and 50 were female (41%), with a mean age of 51 years (19 to 71) at the time of initial THA. All patients were followed for at least five years and were assessed according to the presence of a LLD (non-LLD vs LLD group), as well as the LLD type (longer non-operated side vs shorter non-operated side group).

RESULTS

Overall, 68 hips (56%) became painful and progressed to collapse at a mean of 2.6 years (0.2 to 13.8), resulting in 59 THAs (49%). The five-year collapse-free survival rate for the non-LLD group was 59% (95% confidence interval (CI) 46.8 to 71.8) compared with 45% (95% CI 32.9 to 57.5) for the LLD group (p = 0.036), and 66% (95% CI 55.2 to 77.2) for the longer non-operated side group compared with 32% (95% CI 19.1 to 44.9) for the shorter non-operated side group (p < 0.001). Multivariate regression analyses found that large lesions had a higher risk of collapse than medium-size lesions (odds ratio (OR) 4.19, 95% confidence interval (CI) 1.69 to 10.38; p = 0.002). Meanwhile, patients with a LLD < 3 mm (OR 0.20, 95% CI 0.08 to 0.52; p = 0.001) or a longer non-operated leg (OR 0.11, 95% CI 0.04 to 0.28; p < 0.001) after THA were less likely to experience a subsequent collapse.

CONCLUSION

We found that LLD may be a modifiable risk factor for femoral head collapse. Minimizing LLD and particularly avoiding a shorter non-operated limb after THA may lead to a lower risk of collapse of the asymptomatic hip in patients with bilateral non-traumatic osteonecrosis. Cite this article: Bone Joint J 2019;101-B:303-310.

Low-Intensity Pulsed Ultrasound Treatment Accelerates Angiogenesis by Activating YAP/TAZ in Human Umbilical Vein Endothelial Cells

As a non-invasive method, low-intensity pulsed ultrasound (LIPUS) can accelerate fracture healing. The mechanisms responsible for the enhanced fracture healing need to be studied further. Activation of YAP/TAZ, key mediators of the Hippo signaling pathway, could promote angiogenesis and vascular remodeling. The purpose of this study was to determine whether LIPUS treatment can activate YAP/TAZ. Human umbilical vein endothelial cells (HUVEC) were used. After LIPUS treatment, Western blot and immunofluorescence staining were used for YAP/TAZ activation. Small interfering RNA (siRNA) of YAP and short hairpin LATS1/2 (shLATS1/2) were used to check whether there is cross-talk with the Hippo pathway. The phosphorylated YAP (p-127 and p-397) protein increased more than 3-fold 0.5 h after LIPUS treatment (p < 0.05). TAZ protein increased 3.0-, 2.0- and 1.5-fold 0.5, 6 and 12 h after LIPUS treatment. We found that LIPUS treatment activates YAP/TAZ, which is translocated into the cell nucleus to activate target genes. This process can be inactivated by siYAP and activated by shLATS1/2. The cross-talk with the Hippo pathway can initiate angiogenesis so as to accelerate fracture healing by LIPUS.

Low-intensity pulsed ultrasound inhibits RANKL-induced osteoclast formation via modulating ERK-c-Fos-NFATc1 signaling cascades

Low-intensity pulsed ultrasound (LIPUS), which is a noninvasive form of mechanical energy, has been utilized as a clinical therapy for bone fracture healing. However, the mechanism how LIPUS affects osteoclast formation and osteoclast activity, has not been fully detailed. Here we found that LIPUS inhibited RANKL-induced osteoclast differentiation in vitro, characterized by decreased number and area of tartrate-resistant acid phosphatase (TRAP) positive cells. Moreover, the expression levels of osteoclast-specific gene were also suppressed by LIPUS treatment. Interestingly, F-actin staining and resorption pit assay showed that LIPUS did not affect the bone resorptive activity of mature osteoclasts. Mechanistically, LIPUS achieved these inhibitory effects by disrupting the phosphorylation of ERK and subsequent activation of the osteoclastic transcription factors, c-Fos and NFATc1. Collectively, our results demonstrated that LIPUS effectively suppresses osteoclast differentiation and osteoclast-specific gene expression through the inhibition of ERK-c-Fos-NFATC1 cascades.

Microbubble-Mediated Ultrasound Outweighs Low-Intensity Pulsed Ultrasound on Osteogenesis and Neovascularization in a Rabbit Model of Steroid-Associated Osteonecrosis

Microbubbles magnify the acoustic pressure of low-intensity pulsed ultrasound (LIPUS) and may enhance its bioeffect for diagnostic and therapeutic purposes. This study compared the effect of this novel microbubble-mediated ultrasound (MUS) with that of the traditional LIPUS on osteogenesis and neovascularization in a rabbit model of steroid-associated osteonecrosis. We hypothesized that MUS might outweigh LIPUS on promoting osteogenesis and neovascularization in steroid-associated osteonecrosis. The bilateral femoral head necrosis was induced by lipopolysaccharide and methylprednisolone in the rabbits. The indices of bone mineral density (BMD), trabecular number, maximal loading strength, and mineral apposition rate were analyzed, demonstrating that the animal model of steroid-associated osteonecrosis was successfully established. Both the MUS group (G_M) and the LIPUS group (G_L) were insonated 20 min daily for six weeks. G_M received an extra intracapsular injection of microbubbles before insonation every other day. Fluorescence bone labeling, Micro-CT Analysis, biomechanical test, quantitative real-time PCR, Western blot analysis, and histological evaluation were performed for comparing G_M with G_L. The results demonstrated a 39% higher mineral apposition rate in G_M compared with G_L. The BMD and the maximal loading strength of femoral head of G_M increased by 4.3% and 27.8% compared to those of G_L, respectively. The mRNA and protein expression of BMP-2 and VEGF were also significantly higher in G_M. The number of blood vessels of G_M was 65% greater than that of G_L. MUS is more potent than LIPUS in enhancing osteogenesis, neovascularization, and biomechanical strength of femoral head in the animal model of steroid-associated osteonecrosis. Without increasing the intensity of insonation or the risk of tissue damage, MUS is better for inhibiting the process of steroid-associated osteonecrosis.

Low-Intensity Pulsed Ultrasound Accelerates Traumatic Vertebral Fracture Healing by Coupling Proliferation of Type H Microvessels

OBJECTIVES

Patients with traumatic vertebral fractures often have major associated postoperative morbidities such as healing failure and kyphosis. Low-intensity pulsed ultrasound (US) has been found to promote bone fracture healing. The objectives of our study were to determine whether low-intensity pulsed US could promote traumatic vertebral fracture healing and to explore its inner mechanisms.

METHODS

A rat model of traumatic vertebral fracture was created and treated with low-intensity pulsed US after surgery. At 4 weeks after surgery, radiographic, micro-computed tomography, and 3-dimensional reconstruction were used to assess the radiologic healing status; a histologic analysis was performed to evaluate the pathologic process and relationship between osteogenesis and type H microvessels.

RESULTS

Well-remodeled trabecular meshworks were found in the low-intensity pulsed US treatment group compared to the control group. Micro-computed tomography and 3-dimensional reconstruction revealed more and thicker trabeculae after low-intensity pulsed US treatment. Abundant chondrocytes, a newly formed bone marrow cavity, trabeculae, and microvessels were formed at the fracture sites. More osterix-positive osteoblasts were circling the newly formed bone meshwork and were situated at the interface of chondrocytes in the low-intensity pulsed US treatment group. Type H microvessels were spreading around the newly formed trabecula, bone marrow cavity, osteoblasts, and interface of chondrocytes, with a larger mean vascular density in the low-intensity pulsed US group.

CONCLUSIONS

Low-intensity pulsed US could accelerate traumatic vertebral fracture healing by temporally and spatially increasing chondrogenesis and osteoblast-induced osteogenesis coupled with angiogenesis of type H microvessels in a rat model of traumatic vertebral fracture.

Inhibitory Effect of Low-Intensity Pulsed Ultrasound on the Expression of Lipopolysaccharide-Induced Inflammatory Factors in U937 Cells

OBJECTIVES

Low-intensity pulsed ultrasound (US) has been reported to promote periodontal tissue regeneration and reduce inflammation in soft tissues and in bone infectious diseases. Here we investigated the effect of low-intensity pulsed US on the expression of lipopolysaccharide (LPS)-induced inflammatory factors in U937 macrophage cells.

METHODS

U937 cells were stimulated with different concentrations of LPS and exposed to different intensities of low-intensity pulsed US. Cell viability and apoptosis of U937 cells were determined by cell-counting kit assays and flow cytometry. A real-time polymerase chain reaction and an enzyme-linked immunosorbent assay were used to test the expression of inflammatory factors. The expression levels of toll-like receptor 4, p65, p-IκBα, and IκBα were assessed by western blots.

RESULTS

Tumor necrosis factor α began to increase in U937 cells on induction with 1-μg/mL LPS. Low-intensity pulsed US at the intensity of 60 mW/cm² was more effective in reducing interleukin 8 (IL-8) expression. Furthermore, LPS inhibited the viability and increased apoptosis of U937 cells, whereas low-intensity pulsed US significantly reversed these effects (P < .05). Low-intensity pulsed US reduced the protein expression of IL-6 and IL-8 at both gene and protein levels in U937 cells. The western blot and immunofluorescence showed that low-intensity pulsed US primarily suppressed the degradation and phosphorylation of IκBα and the translocation of p65 into the nuclei.

CONCLUSIONS

Low-intensity pulsed US alleviated the expression of inflammatory factors induced by LPS in U937 cells. This process was modulated by suppressing the toll-like receptor 4-nuclear factor κB signaling pathway. Therefore, low-intensity pulsed US might be a potential immunomodulatory therapy for the treatment of periodontitis.

Combined Treatment with an Anticoagulant and a Vasodilator Prevents Steroid-Associated Osteonecrosis of Rabbit Femoral Heads by Improving Hypercoagulability

Steroid-associated osteonecrosis of the femoral head remains a challenging problem in orthopedics worldwide. One pathomechanism is ischemia of the femoral head, as a result of thrombus formation and vasoconstriction. The present study investigates the effects of combination prevention with enoxaparin and EGb 761 on steroid-associated ONFH in rabbits. Rabbits were randomly divided into 5 groups (control group, model group, enoxaparin group, ginkgo group, and combination group). With the exception of the control group, the groups of rabbits were modeled with lipopolysaccharide and methylprednisolone acetate. Starting with modeling, the enoxaparin group and ginkgo group were injected with 1 μg/kg/day enoxaparin subcutaneously and orally given 40 mg/kg/day EGb 761 for 4 weeks, respectively; the combination group received both treatments. After modeling for 6 weeks, the hematology data indicated prolonged PT and APTT in the three prevention groups. The micro-CT examination revealed higher bone density and better structure; histomorphometry revealed significant pathological changes. Immunohistochemistry revealed higher expression of BMP-2 and VEGF, thus revealing better osteogenesis and angiogenesis activities. Among the three prevention groups, the combination group had the most efficient results. In conclusion, the combined prevention with an anticoagulant and a vasodilator has the potential to decrease the incidence of steroid-associated ONFH in rabbits.

Surgical accuracy, function, and quality of life of simultaneous versus staged bilateral Total hip Arthroplasty in patients with Osteonecrosis of the femoral head

BACKGROUND

The optimal surgical option for patients requiring bilateral hip replacement remains controversial. The purpose of this study was to compare surgical accuracy; functional outcome and health-related quality of life; and prosthetic-related complications and revision surgery of a simultaneous bilateral total hip arthroplasty (THA) with those of a staged bilateral THA with an interval between procedures <12 months.

METHODS

A total of 123 unselected consecutive patients (mean age, 43.3 years) who underwent bilateral THAs for osteonecrosis of the femoral head (ONFH) with a minimum follow-up of two years (mean, 60.2 months) were studied retrospectively; 63 simultaneous procedures served as a test group and 60 staged procedures served as a control group.

RESULTS

The mean postoperative leg-length discrepancy (LLD) and the percentage of patients who had an LLD >3 mm were significantly lower in the simultaneous group (P < 0.001 and P = 0.001, respectively). A higher number of cups within the safe zones, a higher correction rate, and a lower failure rate for the cup placement in the second-operated hip were also identified in the simultaneous group. The mean Harris hip score, EuroQol-5D index, and EuroQol-visual analogue scale score were all better in the simultaneous group at the latest follow-up (P < 0.001, in all comparisons). We found that the simultaneous procedure was associated with a lower incidence of postoperative prosthetic-related complications and revision surgery.

CONCLUSIONS

We suggest that bilateral ONFH could be treated with a simultaneous THA rather than a staged THA to achieve a better surgical outcome.

PTH[1-34] improves the effects of core decompression in early-stage steroid-associated osteonecrosis model by enhancing bone repair and revascularization

Steroid-associated osteonecrosis (SAON) might induce bone collapse and subsequently lead to joint arthroplasty. Core decompression (CD) is regarded as an effective therapy for early-stage SAON, but the prognosis is unsatisfactory due to incomplete bone repair. Parathyroid hormone[1–34] (PTH[1–34]) has demonstrated positive efficacy in promoting bone formation. We therefore evaluated the effects of PTH on improving the effects of CD in Early-Stage SAON. Distal femoral CD was performed two weeks after osteonecrosis induction or vehicle injection, with ten of the ON-induced rabbits being subjected to six-week PTH[1–34] treatment and the others, including ON-induced and non-induced rabbits, being treated with vehicle. MRI confirmed that intermittent PTH administration improved SAON after CD therapy. Micro-CT showed increased bone formation within the tunnel. Bone repair was enhanced with decreased empty osteocyte lacunae and necrosis foci area, resulting in enhanced peak load and stiffness of the tunnel. Additionally, PTH enlarged the mean diameter of vessels in the marrow and increased the number of vessels within the tunnels, as well as elevated the expression of BMP-2, RUNX2, IGF-1, bFGF and VEGF, together with serum OCN and VEGF levels. Therefore, PTH[1–34] enhances the efficacy of CD on osteogenesis and neovascularization, thus promoting bone and blood vessels repair in the SAON model.

LIPUS promotes spinal fusion coupling proliferation of type H microvessels in bone

Low-intensity pulsed ultrasound (LIPUS) has been found to accelerate spinal fusion. Type H microvessels are found in close relation with bone development. We analyzed the role of type H vessels in rat spinal fusion model intervened by LIPUS. It was found LIPUS could significantly accelerate bone fusion rate and enlarge bone callus. Osteoblasts were specifically located on the bone meshwork of the allograft, and were surrounded by type H microvessels. LIPUS could significantly increase the quantity of osteoblasts during spine fusion, which process was coupled with elevated angiogenesis of type H microvessels. Our results suggest that LIPUS may be a noninvasive adjuvant treatment modality in spinal fusion for clinical use. The treatment is recommended for usage for at least one month.

Hydrogen-rich saline attenuates steroid-associated femoral head necrosis through inhibition of oxidative stress in a rabbit model

A growing body of evidence suggests that hydrogen is a novel, selective antioxidant that exerts a protective effect against organ damage. The present study investigated the effect of hydrogen-rich saline on corticosteroid-induced necrosis of the femoral head in an animal model established using prednisolone. A total of 30 healthy, male, adult New Zealand white rabbits were randomly divided into two groups: Hydrogen-rich saline (treated with hydrogen-rich saline via intraperitoneal injection) and placebo (treated with normal saline). At the set time-points, the structure of the femoral head was examined using a microscope; the concentrations of glutathione (GSH), lipid peroxide (LPO), vascular endothelial growth factor (VEGF) and thrombomodulin (TM) in the plasma were measured and the microvessel density was quantified. The results showed that hydrogen-rich saline significantly decreased the levels of VEGF, TM and LPO and increased the GSH level in steroid-associated necrosis of the femoral head in the rabbit model. A significant increase in the microvessel density was observed in the hydrogen-rich saline group. Histopathological staining confirmed the results of the biochemical analysis. The present study demonstrates that hydrogen treatment may alleviate steroid-associated osteonecrosis by inhibiting oxidative stress. Hydrogen-rich saline may provide an alternative treatment for steroid-associated necrosis of the femoral head.

Intermittent Administration of Parathyroid Hormone [1-34] Prevents Particle-Induced Periprosthetic Osteolysis in a Rat Model

We examined whether intermittent administration of parathyroid hormone [1-34] (PTH[1-34]; 60 μg/kg/day) can prevent the negative effects of titanium (Ti) particles on implant fixation and periprosthetic osteolysis in a rat model. Eighteen adult male rats (12 weeks old, bones still growing) received intramedullary Ti implants in their bilateral femurs; 6 rats from the blank group received vehicle injections, and 12 rats from the control group and PTH treatment group received Ti particle injections at the time of operation and intra-articular injections 2 and 4 weeks postoperatively. Six of the rats that received Ti particles from the PTH group also received PTH[1-34] treatment. Six weeks postoperatively, all specimens were collected for assessment by X-ray, micro-CT, biomechanical, scanning electron microscopy (SEM), and dynamic histomorphometry. A lower BMD, BV/TV, Tb.N, maximal fixation strength, and mineral apposition rate were observed in the control group compared to the blank group, demonstrating that a periprosthetic osteolysis model had been successfully established. Administration of PTH[1-34] significantly increased the bone mineral density of the distal femur, BV/TV, Tb.N, Tb.Th, Tb.Sp, Con.D, SMI, and maximal fixation strength in the PTH group compared to that in the control group. SEM revealed higher bone-implant contact, thicker lamellar bone, and larger trabecular bone area in the PTH group than in the control group. A higher mineral apposition rate was observed in the PTH group compared to both the blank and control groups. These findings imply that intermittent administration of PTH[1-34] prevents periprosthetic osteolysis by promoting bone formation. The effects of PTH[1-34] were evaluated at a suprapharmacological dosage to the human equivalent in rats; therefore, additional studies are required to demonstrate its therapeutic potential in periprosthetic osteolysis.