Methods for Assessing Bone Quality: A Review

Background  

Bone mass, geometry, and tissue material properties contribute to bone structural integrity. Thus, bone strength arises from both bone quantity and quality. Bone quality encompasses the geometric and material factors that contribute to fracture resistance.     

Structural Allograft as an Option for Treating Infected Hip Arthroplasty with Massive Bone Loss

Background  

Revision of the infected hip arthroplasty with major bone loss is difficult. Attempts to restore bone stock with structural allograft are controversial.     

Infrared Assessment of Bone Quality: A Review

Background  

Bone strength depends on both bone quantity and quality. The former is routinely estimated in clinical settings through bone mineral density measurements but not the latter. Bone quality encompasses the structural and material properties of bone. Although its importance is appreciated, its contribution in determining bone strength has been difficult to precisely quantify partly because it is multifactorial and requires investigation of all bone hierarchical levels. Fourier transform infrared spectroscopy provides one way to explore these levels.     

The Clinical Significance of Vimentin-Expressing Gastric Cancer Cells in Bone Marrow

Background  

Expression of the mesenchymal marker gene vimentin (VIM) in gastric cancer is associated with a more aggressive form of the disease and poor prognosis. Because epithelial mesenchymal transition (EMT) plays a critical role in the progression of gastric cancer, VIM expression was examined in the bone marrow (BM) of gastric cancer patients.     

Injection of Demineralized Bone Matrix With Bone Marrow Concentrate Improves Healing in Unicameral Bone Cyst

Background  

Unicameral bone cysts are benign lesions that usually spontaneously regress with skeletal maturity; however, the high risk of pathologic fractures often justifies treatment that could reinforce a weakened bone cortex. Various treatments have been proposed but there is no consensus regarding the best procedure.     

Liner Exchange and Bone Grafting: Rare Option to Treat Wear & Lysis of Stable TKAs

Background  

Liner exchange and bone grafting are commonly performed for wear and osteolysis around well-fixed modular acetabular components that otherwise would require structural allografting and revision THA. However, liner exchange in the face of substantial lysis around TKA has been performed rarely with reports of failure rates of up to 25% at 3 year followup.     

Osteogenic Protein-1 Delivered by Hydroxyapatite-coated Implants Improves Bone Ingrowth in Extracortical Bone Bridging

Background  

Extracortical bone bridging for treatment of massive bone loss can improve stability and longevity of massive endoprostheses. Osteogenic protein-1 (OP-1), when used with allograft bone, reportedly improves extracortical bone bridging and bone ingrowth.     

Anabolic Agents and Bone Quality

Background  

The definition of bone quality is evolving particularly from the perspective of anabolic agents that can enhance not only bone mineral density but also bone microarchitecture, composition, morphology, amount of microdamage, and remodeling dynamics.     

Surgical Revascularization in Structural Orthotopic Bone Allograft Increases Bone Remodeling

Background

Osseous defects reconstructed with cryopreserved structural allografts are poorly revascularized and therefore are prone to nonunion, infection, deterioration of mechanical properties, and fracture. Whether this can be mitigated by specific interventions such as intramedullary surgical revascularization has been incompletely evaluated.

Questions/purposes

We aimed to study surgical revascularization as a means to improve bone remodeling in cryopreserved allograft. Second, we questioned whether spatial histomorphometric differences occur in cortical bone areas after intramedullary surgical revascularization. Third, biomechanical properties of the graft-recipient construct in surgically revascularized allograft were compared with those of conventional allografts.

Methods

Allografts were harvested from 10 Brown Norway rats, cryopreserved, and transplanted orthotopically in a 10-mm defect in two groups of 10 Lewis rats each (major histocompatibility mismatch). In the control group, no surgical revascularization was performed, whereas in the experimental group, a saphenous arteriovenous bundle was transposed in the bone marrow cavity. Bone remodeling was measured with histomorphometry, histology, and microcomputed tomography at 16 weeks. Spatial differences were analyzed with histomorphometry. To determine biomechanical properties, load at failure and structural stiffness in bending were evaluated by the three-point bend testing. In both groups, normal values of the contralateral femur also were analyzed.

Results

Surgically revascularized allografts had increased bone remodeling (bone formation rate to bone surface ratio: 130 ± 47 µm³/µm²/year versus 44 ± 43 µm³/µm²/year, p = 0.006) and higher cortical osteocyte counts (18.6% ± 12.7% versus 3.1% ± 2.8%, p = 0.002) than nonrevascularized grafts. In nonrevascularized grafts, the bone formation rate to bone surface ratio was 35% of the contralateral normal values, whereas in surgically revascularized grafts, the bone formation rate to bone surface ratio in the grafts exceeded the contralateral values (110%). Microcomputed tomography did not show differences in bone volume between groups, however in both groups, bone volume was less in grafts compared with the contralateral femurs. Inner cortical bone formation rate to bone surface ratio was greater in surgically revascularized grafts (65 ± 30 µm³/µm²/year versus 13 ± 16 µm³/µm²/year in the control group, p = 0.012). Outer cortical bone formation rate to bone surface ratio also increased in surgically revascularized grafts (49 ± 31 µm³/µm²/year versus 19 ± 21 µm³/µm²/year, p = 0.032). No differences were found in load at failure and structural stiffness between both groups. In the control group, load at failure and structural stiffness were lower in grafts than in the contralateral femurs (p = 0.004 and p = 0.02, respectively). In the experimental group, surgically revascularized grafts also had lower load at failure and structural stiffness than the contralateral femurs (p = 0.008 and p = 0.02, respectively).

Conclusions

Surgical revascularization of large segmental allografts improved bone remodeling and viability without an adverse effect on total bone volume or bending strength and stiffness in this short-term analysis.

Clinical Relevance

Cryopreserved allografts remain largely necrotic and are associated with a high rate of complications. Surgical revascularization increases graft healing which could contribute to graft survival with time.     

Raman Assessment of Bone Quality

Background  

Progress in the diagnosis and prediction of fragility fractures depends on improvements to the understating of the compositional contributors of bone quality to mechanical competence. Raman spectroscopy has been used to evaluate alterations to bone composition associated with aging, disease, or injury.     

Diseases Affecting Bone Quality: Beyond Osteoporosis

Background  

Bone quantity, quality, and turnover contribute to whole bone strength. Although bone mineral density, or bone quantity, is associated with increased fracture risk, less is known about bone quality. Various conditions, including disorders of mineral homeostasis, disorders in bone remodeling, collagen disorders, and drugs, affect bone quality.     

A Correlation Exists Between Subchondral Bone Mineral Density of the Distal Radius and Systemic Bone Mineral Density

Background  

Intraarticular distal radius fractures are common and risk articular congruity owing to disruption of the subchondral bone. Studies regarding microstructure and mechanical properties of the distal radius, however, focus only on the cortical and trabecular bones in the metaphysis and not on the subchondral bone.     

The Otto Aufranc Award: Demineralized Bone Matrix Around Porous Implants Promotes Rapid Gap Healing and Bone Ingrowth

Background  

Noncemented revision arthroplasty is often complicated by the presence of bone implant gaps that reduce initial stability and biologic fixation. Demineralized bone matrix has osteoinductive properties and therefore the potential to enhance gap healing and porous implant fixation.     

The Influence of Cortical Porosity on the Strength of Bone During Growth and Advancing Age

Purpose of Review

Bone densitometry provides a two-dimensional projected areal apparent bone mineral density that fails to capture the heterogeneity of bone’s material composition and macro-, micro-, and nano-structures critical to its material and structural strength. Assessment of the structural basis of bone fragility has focused largely on trabecular bone based on the common occurrence of fragility fractures at sites with substantial amounts of trabecular bone. This review focuses on the contribution of cortical bone to bone fragility throughout life.

Recent Findings

Accurately differentiating cortical and trabecular bone loss has important implications in quantifying bone fragility as these compartments have differing effects on bone strength. Recent advances in imaging methodology have improved distinction of these two compartments by (i) recognition of a cortico-trabecular transitional zone and (ii) quantifying bone microstructure in a region of interest that is a percentage of bone length rather than a fixed point. Additionally, non-invasive three-dimensional imaging methods allow more accurate quantification of changes in the cortical, trabecular, and cortico-trabecular compartments during growth, aging, disease, and treatment.

Summary

Over 75% of the skeleton is assembled as cortical bone. Of all fragility fractures, ~?80% are appendicular and involve regions rich in cortical bone and ~?70% of all age-related appendicular bone loss is cortical and is mainly due to unbalanced intracortical remodeling which increases cortical porosity. The failure to achieve the optimal peak bone microstructure during growth due to disease and the deterioration in cortical and trabecular bone produced by bone loss compromise bone strength. The loss of strength produced by microstructural deterioration is disproportionate to the bone loss producing this deterioration. The reason for this is that the loss of strength increases as a 7th power function of the rise in cortical porosity and a 3rd power function of the fall in trabecular density (Schaffler and Burr in J Biomech. 21(1):13–6, 1988), hence the need to quantify bone microstructure.

     

Bone mass assessment in naval crew members by quantitative ultrasound technique

Objective  

Of necessity, naval crews live in confined spaces when on board warships, which may lead to decreased bone mass and to subsequent bone fractures. Therefore, we investigated the bone mass of crew members and the relationship between bone mass and lifestyle factors.     

High-resolution Computed Tomography for Clinical Imaging of Bone Microarchitecture

Background  

The role of bone structure, one component of bone quality, has emerged as a contributor to bone strength. The application of high-resolution imaging in evaluating bone structure has evolved from an in vitro technology for small specimens to an emerging clinical research tool for in vivo studies in humans. However, many technical and practical challenges remain to translate these techniques into established clinical outcomes.     

Bone status in a mouse model of genetic hemochromatosis

Summary  

Genetic hemochromatosis is a cause of osteoporosis; mechanisms leading to iron-related bone loss are not fully characterized. We assessed the bone phenotype of HFE ^−/− male mice, a mouse model of hemochromatosis. They had a phenotype of osteoporosis with low bone mass and alteration of the bone microarchitecture.     

The Effect of Antiresorptives on Bone Quality

Background  

Currently, antiresorptive therapy in the treatment and prevention of osteoporosis includes bisphosphonates, estrogen replacement, selective estrogen receptor modulators (raloxifene), and denosumab (a human antibody that inactivates RANKL). The original paradigm driving the development of antiresorptive therapy was that inhibition of bone resorption would allow bone formation to continue and correct the defect. However, it is now clear increases in bone density account for little of the antifracture effect of these treatments.     

Do Porous Tantalum Implants Help Preserve Bone?: Evaluation of Tibial Bone Density Surrounding Tantalum Tibial Implants in TKA

Background  

TKA with conventional metal-backed tibial implants subjects the tibial metaphysis to stress shielding, with resultant loss of bone density.     

Bone Substitution and Augmentation in Trauma Surgery with a Resorbable Calcium Phosphate Bone Cement

Background and Purpose:  

Synthetically manufactured bone substitute materials are widely used to fill cancellous bone defects in fracture treatment. By using these materials, complications occurring with the harvesting of autologous bone such as inflammation, hemorrhage and pain are prevented. Ideally, after osteointegration, the bone substitute resorbs, and complete restoration of bone architecture is achieved. Until now, clinical experience is limited to non-fully resorbable calcium phosphates, e. g., hydroxyapatite. Previous studies have revealed a fully resorbable pure calcium phosphate, which is applied in a paste form as a bone implant and results in complete resorption and biocompatibility. The purpose of this prospective, uncontrolled clinical study was to investigate the safety and performance of this new resorbable bone substitute material.