Bisphosphonates can block the deterioration in implant fixation after withdrawal of intermittent doses of parathyroid hormone

Osseointegration Pharmacology: A Systematic Mapping Using Artificial Intelligence

Clinical performance of osseointegrated implants could be compromised by the medications taken by patients. The effect of a specific medication on osseointegration can be easily investigated using traditional systematic reviews. However, assessment of all known medications requires the use of evidence mapping methods. These methods allow assessment of complex questions, but they are very resource intensive when done manually. The objective of this study was to develop a machine learning algorithm to automatically map the literature assessing the effect of medications on osseointegration. Datasets of articles classified manually were used to train a machine-learning algorithm based on Support Vector Machines. The algorithm was then validated and used to screen 599,604 articles identified with an extremely sensitive search strategy. The algorithm included 281 relevant articles that described the effect of 31 different drugs on osseointegration. This approach achieved an accuracy of 95%, and compared to manual screening, it reduced the workload by 93%. The systematic mapping revealed that the treatment outcomes of osseointegrated medical devices could be influenced by drugs affecting homeostasis, inflammation, cell proliferation and bone remodeling. The effect of all known medications on the performance of osseointegrated medical devices can be assessed using evidence mappings executed with highly accurate machine learning algorithms.

Effects of sequential treatment with intermittent parathyroid hormone and zoledronic acid on particle-induced implant loosening: Evidence from a rat model

Particle-induced implant loosening is a major challenge to long-term survival of joint prostheses. Administration of intermittent parathyroid hormone (PTH) has shown potential in the treatment of cases of early-stage periprosthetic osteolysis, while sequential administration of intermittent PTH (iPTH) and bisphosphonates (Bps) has achieved significant effects on treatment of postmenopausal osteoporosis. The objective of this study was to determine whether sequential treatment could preserve bone mass and implant fixation during a pathological course of peri-implant osteolysis in a rat model. Ninety male Sprague Dawley rats were randomly divided into nine groups, four of which were used for confirmation of establishment of the peri-implant osteolysis model at two time points, while the other five were used to determine the efficiency of the sequential treatment on peri-implant osteolysis. Implant fixation and peri-implant bone mass were evaluated using biomechanical testing, micro-CT analysis, and histology at 6 and 12 weeks postoperative. The biomechanical test demonstrated that the maximum loading force during a push-out test was significantly elevated in the sequential treatment group compared to the osteolysis group and iPTH withdrawal group at 12 weeks. Peri-implant bone morphology also indicated a robust increase in bone volume in the sequential treatment group. Sequential administration of iPTH and Bps was effective in preventing experimental peri-implant osteolysis, resulting in improved implant fixation and increased peri-implant bone volume. Clinical significance: The innovative application of sequential treatment in peri-implant osteolysis could be used clinically to improve the prognosis of patients with early-stage periprosthetic osteolysis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1489-1497, 2019.

The effect of osteoprotegerin on implant osseointegration in ovariectomized rats

INTRODUCTION

Osteoprotegerin (OPG), the endogenous inhibitor of RANKL, prevents or reverses bone loss in a variety of preclinical models of bone disease. Preclinical studies indicate that osteoporosis significantly impairs implant fixation. This study aims to investigate the role of OPG in implant osseointegration in ovariectomized rats.

MATERIAL AND METHODS

Twelve weeks after bilateral ovariectomy, each rat accepted two titanium screws in the proximal tibiae. All animals were then randomly divided into two groups: the control (10 rats) and OPG group (10 rats). Subcutaneous injection of OPG (10 mg/kg) or vehicle was performed three times a week. Eight weeks later, tibiae with screws were harvested for micro-computed tomography (μCT), histological and biomechanical analysis.

RESULTS

Compared to control, OPG increased the percent bone volume by 124%, the percent osseointegration by 167%, the mean trabecular number by 111%, the mean trabecular thickness by 92% (p < 0.01), the mean connective density by 95% (p < 0.05); and decreased the mean trabecular separation by 64% in μCT analysis (p < 0.05). Osteoprotegerin also increased bone area density by 160% and bone-to-implant contact by 234% in histomorphometric evaluation (p < 0.01), and increased the maximal push-out force by 228% in biomechanical test (p < 0.01).

CONCLUSIONS

Systemic administration of OPG improved implant osseointegration and fixation in ovariectomized rats, resulting from the increased peri-implant bone mass and improved trabecular microarchitecture.

Promotion of peri-implant bone healing by systemically administered parathyroid hormone (1-34) and zoledronic acid adsorbed onto the implant surface

The effect of human parathyroid hormone 1-34 (PTH) and zoledronic acid (ZA) alone or in combination on bone healing in osteoporotic settings was tested using implants inserted in tibiae of ovariectomized (OVX) rats. Combination therapy promoted bone healing more than each treatment alone 12 weeks after implant insertion.

INTRODUCTION

PTH and ZA have been demonstrated to be effective on implant fixation. However, reports about the combined use of PTH and ZA for promotion of bone healing around implant in osteoporotic settings are still limited. This study aims to investigate effects of PTH+ZA on implant stabilization in OVX rats.

METHODS

Twelve weeks after bilateral ovariectomy, OVX rats randomly received implants without or with ZA (by immersion in 1 mg/ml ZA solution for 24 h). Subsequently, half of the animals from each group also received subcutaneous injections of PTH (60 μg/kg, three times a week) for 12 weeks. Thus, there were four groups: control, PTH, ZA, and PTH+ZA.

RESULTS

All treatments promoted bone healing around implant compared to control, but PTH+ZA treatment showed significantly stronger effects than PTH or ZA alone in histological, micro-CT, and biomechanical tests.

CONCLUSION

The results indicated the additive effects of PTH and ZA on implant fixation in OVX rats; it was suggested that the anabolic effect of PTH was potent and not blunted by ZA during bone healing around implant when used concurrently.

The effects of combined human parathyroid hormone (1-34) and zoledronic acid treatment on fracture healing in osteoporotic rats

Ovariectomized (OVX) rats with tibial fracture received vehicle, ZA, PTH, or ZA plus PTH treatment for 4 and 8 weeks. Bone metabolism, callus formation, and the mass of undisturbed bone tissue were evaluated by serum analysis, histology, immunohistochemistry, radiography, micro-computerized tomography, and biomechanical test.

INTRODUCTION

Previous studies have demonstrated the effect of ZA or PTH on osteoporotic fracture healing. However, reports about effects of ZA plus PTH on callus formation of osteoporotic fracture were limited. This study was designed to investigate the impact of combined treatment with ZA and PTH on fracture healing in OVX rats.

METHODS

Twelve weeks after bilateral ovariectomy, all rats underwent unilateral transverse osteotomy on tibiae. Animals then randomly received vehicle, ZA (1.5 μg/kg weekly), PTH (60 μg/kg, three times a week), or ZA plus PTH until death at 4 and 8 weeks. The blood and bilateral tibiae of rats were harvested for evaluation.

RESULTS

All treatments increased callus formation and strength other than the control; ZA + PTH showed the strongest effects on percent bone volume (BV/TV), trabecular thickness, total fluorescence-marked callus area, and biomechanical strength. Additionally, inhibited RANKL and enhanced osteoprotegerin expression were observed in the ZA + PTH group. But no difference in bone mineral density and BV/TV of the contralateral tibiae was observed between treated groups.

CONCLUSION

Findings in this study suggested an additive effect of ZA and PTH on fracture healing in OVX rats, and this additive effect was specific to callus formation, not to undisturbed bone tissue.

Bisphosphonates in orthopedic applications

Bisphosphonates (BPs) exert potent effects on the skeleton. As such, there are important questions relating to how treatment with BPs for metabolic disorders might affect outcomes of orthopedic problems. A further question is what role, if any, might BPs play as adjunctive therapeutics for orthopedic problems. This article outlines the research thus far in the application of BPs to the management of osteonecrosis, bone repair, and joint arthroplasty. Many animal studies show a benefit to decreasing bone resorption in models of osteonecrosis. These include studies in both small and large animals, backed up by limited human data. Further clinical trials are underway for this indication. In bone repair, again, multiple studies exist. There are concerns that BPs could interfere with the normal processes of healing. Some of the controversy about benefits or adverse effects of BPs in this context can be distilled down to effects of dosing and administration. With some exceptions, longer intervals between dosing seem to be more beneficial while not producing adverse healing effects in animal studies. In joint arthroplasty, animal studies suggest a role for topical or systemic BPs for enhancing bone on-growth to implant surfaces and strength of mechanical fixation, although these are yet to be confirmed in clinical studies. Clinical studies show that BPs inhibit periprosthetic bone loss due to strain-adaptive remodeling and after impaction bone grafting, although an efficacy in inhibiting inflammatory bone loss due to wear particle-induced osteolysis has not been confirmed. Lastly, as anabolic drugs have become available, there is increasing interest in their combined use with BPs. From experimental data, manipulation of both the anabolic and catabolic responses is a powerful approach in models of bone repair.

Parathyroid hormone treatment increases fixation of orthopedic implants with gap healing: a biomechanical and histomorphometric canine study of porous coated titanium alloy implants in cancellous bone

Parathyroid hormone (PTH) administered intermittently is a bone-building peptide. In joint replacements, implants are unavoidably surrounded by gaps despite meticulous surgical technique and osseointegration is challenging. We examined the effect of human PTH(1-34) on implant fixation in an experimental gap model. We inserted cylindrical (10 × 6 mm) porous coated titanium alloy implants in a concentric 1-mm gap in normal cancellous bone of proximal tibia in 20 canines. Animals were randomized to treatment with PTH(1-34) 5 μg/kg daily. After 4 weeks, fixation was evaluated by histomorphometry and push-out test. Bone volume was increased significantly in the gap. In the outer gap (500 μm), the bone volume fraction median (interquartile range) was 27% (20-37%) for PTH and 10% (6-14%) for control. In the inner gap, the bone volume fraction was 33% (26-36%) for PTH and 13% (11-18%) for control. At the implant interface, the bone fraction improved with 16% (11-20%) for PTH and 10% (7-12%) (P = 0.07) for control. Mechanical implant fixation was improved for implants exposed to PTH. For PTH, median (interquartile range) shear stiffness was significantly higher (PTH 17.4 [12.7-39.7] MPa/mm and control 8.8 [3.3-12.4] MPa/mm) (P < 0.05). Energy absorption was significantly enhanced for PTH (PTH 781 [595-1,198.5] J/m(2) and control 470 [189-596] J/m(2)). Increased shear strength was observed but was not significant (PTH 3.0 [2.6-4.9] and control 2.0 [0.9-3.0] MPa) (P = 0.08). Results show that PTH has a positive effect on implant fixation in regions where gaps exist in the surrounding bone. With further studies, PTH may potentially be used clinically to enhance tissue integration in these challenging environments.

Effect of alendronate and intermittent parathyroid hormone on implant fixation in ovariectomized rats

BACKGROUND

Intermittent administration of parathyroid hormone (PTH) leads to bone formation by increasing osteoblast numbers and activity levels. Animal studies have shown that intermittent PTH administration increases implant fixation in normal rats. The purpose of this study was to analyze the osseous incorporation of an implant in osteoporotic rats while treating them with intermittent PTH (1-34) or alendronate.

METHODS

A total of 36 ovariectomized (OVX) Wistar rats were randomized into three groups. Polymethylmethacrylate cement rods were implanted in one tibia in each rat. The three groups received daily PTH (60 mug/kg body weight [BW]), alendronate (200 mug/kg BW), or saline (0.5 ml/kg BW). A sham-ovariectomized group (n = 12) was treated with saline. After 2 weeks, the area around the implants was analyzed by histomorphometry for bone volume density (BVD) and implant bone contact. Bone mineral density (BMD) was evaluated by dual-energy X-ray absorptiometry.

RESULTS

The BVD was higher in the specimens treated with PTH than in the other groups. PTH improved the BVD, BMD, and implant bone contact. Alendronate doubled the implant bone contact compared to the OVX and sham groups but did not improve BVD or BMD.

CONCLUSIONS

These findings confirm that intermittent PTH enhances implant fixation in osteoporotic bone. The clinical significance of these findings is that application of intermittent PTH may be beneficial for early implant fixation in fractures, nonunions, and prosthetic replacements when bone density is decreased.