Aims. The distal radius is a major site of osteoporotic bone loss resulting in a high risk of fragility fracture. This study evaluated the capability of a cortical index (CI) at the distal radius to predict the local bone mineral density (BMD). Methods. A total of 54 human cadaver forearms (ten singles, 22 pairs) (19 to 90 years) were systematically assessed by clinical radiograph (XR), dual-energy X-ray absorptiometry (DXA), CT, as well as high-resolution peripheral quantitative CT (HR-pQCT). Cortical bone thickness (CBT) of the distal radius was measured on XR and CT scans, and two cortical indices mean average (CBTavg) and gauge (CBTg) were determined. These cortical indices were compared to the BMD of the distal radius determined by DXA (areal BMD (aBMD)) and HR-pQCT (volumetric BMD (vBMD)). Pearson correlation coefficient (r) and intraclass correlation coefficient (ICC) were used to compare the results and degree of reliability. Results. The CBT could accurately be determined on XRs and highly correlated to those determined on CT scans (r = 0.87 to 0.93). The CBTavg index of the XRs significantly correlated with the BMD measured by DXA (r = 0.78) and HR-pQCT (r = 0.63), as did the CBTg index with the DXA (r = 0.55) and HR-pQCT (r = 0.64) (all p < 0.001). A high correlation of the BMD and CBT was observed between paired specimens (r = 0.79 to 0.96). The intra- and inter-rater reliability was excellent (ICC 0.79 to 0.92). Conclusion. The cortical index (CBTavg) at the distal radius shows a close correlation to the local BMD. It thus can serve as an initial screening tool to estimate the local bone quality if quantitative BMD measurements are unavailable, and enhance decision-making in acute settings on fracture management or further osteoporosis screening. Cite this article: Bone Joint Res 2021;10(12):820–829

The increase in revision joint replacement surgery and fractures of bone around orthopaedic implants may be partly addressed by keeping bone healthy around orthopaedic implants by inserting implants with mechanical properties closer to the patient's bone properties. We do not currently have an accurate way of calculating a patient's bone mechanical properties. We are therefore investigating whether microindentation can accurately calculate bone stiffness. We received ethical approval to retrieve femoral heads and necks from patients undergoing hip replacement surgery for research. Cortical bone from the medial calcar region of the femoral neck was cut into 3×3×6mm cuboid specimens. Micro-indentation testing was performed in the direction of loading of the bone using a MicroMaterials indenter. The samples were kept hydrated and were not fixed or polished. From the unloading curve after indentation, the elastic modulus was calculated, using the Oliver- Pharr method. To assess which microindentation machine settings most precisely calculate the elastic modulus we varied the loading and unloading rates, load and indenter tip shape. The most precise results were obtained by using a spherical indenter tip (rather than Berkovich tip), high load (10N), a loading rate of 100 mN/s and unloading rate of 300 mN/s with a pause of 60 seconds at maximum load and multiple load cycles with constant loads. Using these settings the mean elastic modulus over 12 cycles of testing was 13.0 GPa (+/- 2.47). By using a spherical indenter tip and fast unloading it was possible to get precise apparent modulus values. By unloading as fast as possible the effects of bone viscoelastic properties are minimised. By using a spherical indenter tip, plastic deformation at the tip is minimised (compared to the Berkovich tip). We are performing further standard compression tests on the samples to verify the accuracy of the indentation tests

Treatment of tendon and ligament injuries remains challenging; the aim is to find a biocompatible substance with mechanical and structural properties that replicate those of normal tendon and ligament. We examined the mechanical properties of Demineralised Cortical Bone (DCB) after gamma irradiation (GI) and freeze drying (FD). We also used different techniques for repairing bone-tendon-bone with DCB in order to measure the mechanical performance of the construct. DCB specimens were allocated into 4 groups; FD, GI, combination of both or none. The maximum tensile forces and stresses were measured. 4 cadaveric models of repair of 1cm patellar tendon defect using DCB were designed; model-1 using one bone anchor, Model-2 using 2 bone anchors, Model-3 off-loading by continuous thread looped twice through bony tunnels, Model-4 off-loading with 3 hand braided threads. Force to failure and mode were recorded for each sample. FD groups results were statistically higher (p=<0.05) compared to non-FD groups, while there was no statistical difference between GI and non-GI groups. The median failure force for model-1: 250N, model-2: 290N, model-3: 767N and model-4: 934N. There was no statistical significance between model-1 and model-2 (p=0.249), however statistical significance was found between other models (p=<0.006). GI has no significant effect on mechanical strength of the CDB while FD may have positive effect on its mechanical strength. Our study shows that a tendon rupture can be successfully augmented with CDB giving initial appropriate mechanical strength suitable for in vivo use providing the biological reactions to the graft are favourable

Summary. Our study shows that a tendon rupture can be successfully augmented with Demineralised Cortical Bone (DCB) giving initial appropriate mechanical strength suitable for in vivo use providing the biological reactions to the graft are favourable. Introduction. Treatment of tendon and ligament injuries remains challenging; the aim is to find a biocompatible substance with mechanical and structural properties that replicate those of normal tendon and ligament. Because of its structural and mechanical properties, we proposed that DCB can be used in repair of tendon and ligament as well as regeneration of the enthesis. DCB is porous, biocompatible and has the potential to be remodelled by the host tissues. 2 studies were designed; in the first we examined the mechanical properties of DCB after gamma irradiation (GI) and freeze drying (FD). In the second we used different techniques for repairing bone-tendon-bone with DCB in order to measure the mechanical performance of the construct. Methods. In the first study we allocated the DCB specimens into 4 groups; group-A non-freeze dried non-gamma irradiated, group-B freeze dried non-gamma irradiated, group-C non-freeze dried gamma irradiated and group-D freeze dried and gamma irradiated. The 4 groups were tested for maximum tensile strength. In the 2nd study, patella - patellar tendon - tibia construct of mature ewes were harvested and the distal 1cm of the patellar tendon was excised, 4 models of repair were tested;. • Model-1, DCB was used to bridge the gap between the tendon and the tibial tuberosity. The DCB strip was stitched to the tendon using one bone anchor. • Model-2, similar to model-1 with the use of 2 bone anchors. • Model-3, similar to model-2, construct was offloaded by Fiberwire continuous thread looped twice through bony tunnels sited in the patella and in the tibial tuberosity. • Model-4, similar to model-3 with 3 hand braided fiberwire threads as offloading loop. All 4 models were tested until failure and force displacement curves used to investigate the structural properties of the reconstruction. Results. The Median of maximum tensile force for group-A was 218N [95%C.I.=147.9–284.7N], group-B was 306N [95%C.I.=154.1–488.6N], group-C was 263N [95%C.I.=227.8–315.6N], group-D was 676N [95%C.I.=127-1094.9N]. Group-D results were statistically higher (p=<0.05) compared to group-A and group-C, while there was no statistical significance compared to group-B. The median failure force for model-1 was 250N, (95%C.I.=235-287), model-2 was 290N (95%C.I.=197-396), model-3 was 767N (95%C.I.=730-812) and for model-4 was 934N (95%C.I.=867-975). There was no statistical significance between model-1 and model-2 (p=0.249), however statistical significance was found between other models (p=<0.006). Discussion. Demineralised Bone is widely used as a bone graft substitute and may be used to augment bone formation in load bearing applications. In this study we focus on the potential use of demineralised bone in ligament and tendon repair. A previous animal study by our group found that the use of demineralised bone can enhance healing of the enthesis. Other published studies suggested the possibility of using DCB as ligament substitute. We examined the effect of gamma radiation as the most common sterilisation technique in medical field and the freeze drying as a possible technique for long term storage on the tensile strength of the DCB

Cortical bone is a complex composite material composed of an inorganic mineral phase and organic matrix of type I collagen and various non-collagenous proteins. The hierarchical organisation of bone results in a transversely isotropic material with the mechanical properties in the long-axis (z) being superior to the radial and circumferential axes which are equivalent. This directional dependence of bone has been well reported, whilst the mechanisms/anisotropy are more difficult to study. This study examined the anistropic nature of cortical bone and the influence of different sterilisation procedures. Ninety cortical bone cubes were prepared using established techniques (Walsh and Guzelsu) and randomly allocated to three treatments; control, 15 KGy, Super Critical Fluid (SCF) (n=30 per group). The ultrasonic moduli was examined using longitudinal sound waves at 5 MHz using a pulse receive technique. Unconfined compression was performed non-destructively in longitudinal (z), circumferential (ï±) and radial orientations (r). Samples were tested to failure in the z axis. A two-way analysis of variance (treatment and time) followed by a Games Howell post hoc test and covariate analysis was performed using SPSS for Windows. Data from this study revealed some interesting and intriguing results with respect to the effects of gamma irradiation and dense gas technology on the properties of cortical bone and load transmission. A statistical decrease in the compressive stiffness and strength was noted with 15 KGy of whilst SCF treatment did not alter the properties in the r or ï orientations. Similar results were found with respect to the ultrasonic moduli (data not shown). The pilot data confirmed the adverse effects of bone in compression following gamma irradiation as we found in our recently presented ORS work. However, the study in compression demonstrated that the directional dependence that makes cortical bone a transversely isotropic material is removed following gamma irradiation with SCF did not appear to have this effect. The effects of gamma irradiation on the mechanical performance of allografts in the long bone axis may play a role in their in vivo performance. The removal of the anisotropy following gamma irradiation provides insight into the relationship(s) between the mineral and organic constituents, which requires further study

Introduction: Open lower leg fractures are frequently associated with severe soft tissue damage. Cortical bone tissue is thus denudated. Osteomyelitis and impaired circulation with loss of bone tissue and subsequent defects are among the main complications. Necrosis vs. revascularisation are supposed to be reflected by local tissue contents of high energy phosphates. Methods: 80 inbred white New Zealand rabbits with two groups of 40 animals each were employed. Each animal had a tibial fracture induced in a standardized fashion, stabilized by screw osteosynthesis. The fracture area was freed from soft tissue and periost and the medullary space reamed. After 3 or 7 days (group one or two, respectively), the tissue defect was covered by a local fascia-free gastrocnemius muscle flap. In increasing intervalls from one to 16 weeks, the implants were removed and the animals euthanized. Cortical bone of the fragment created and of the adjacent cortical bone with and without periostal linig was analysed. The bone was removed after euthanisation and analysed histomorphologically. Simultaneously, fragments were deep frozen in liquid nitrogen at −190°C, a two by one centimeter fragment from the unaffected contralateral tibia harvested as control. Analysis of high energy phosphates (ATP) was performed by high pressure liquid chromatography as described by NEES (HPLC). All animals were kept i. Results: The average ATP contents in healthy cortical bone was 0,092 +/− 0,009 nmol/mg dry weight. A muscle flap after three days led to significantly higher concentrations as compared to 7 days with 0,081 +/− 0,011 vs 0,03 +/− 0,008 nml/mg dry weight (mean +/− SEM; p < 0,05, paired t-test), the latter resembling sequestration. Simultaneously, flap covering after three days displayed a lower rate of necroses with 23 vs. 40 % (p < 0,05, paired t-test). Incidence of osteomyelitis was as well higher in the 7-days-group (24%). Discussion: Delayed plastic covering of open lower leg fractures led to decreased ATP levels, delayed healing and infection in our experimental setting. For the first time, we could determine the contents of ATP by HPLC in cortical bone. Increase in ATP contents reflected the biological quality of the bone investigated, ranging from reconstituted healthy bone to sequesters

Introduction and Objective

Bone remodelling is a continuous process whereby osteocytes regulate the activity of osteoblasts and osteoclasts to repair loading-induced microdamage. While many in vitro studies have established the role of paracrine factors (e.g., RANKL/OPG) and cellular pathways involved in bone homeostasis, these techniques are generally limited to two-dimensional cell culture, which neglects the role of the native extracellular matrix in maintaining the phenotype of osteocyte. Recently, ex vivo models have been used to understand cell physiology and mechanobiology in the presence of the native matrix. Such approaches could be applicable to study the mechanisms of bone repair, whilst also enabling exploration of biomechanical cues. However, to date an ex vivo model of bone remodelling in cortical bone has not been developed. In this study, the objective was to develop an ex vivo model where cortical bone was subjected to cyclic strains to study the remodelling of bone.

Background: Conventional magnetic resonance pulse sequence echo times (TEs) produces no signal of cortical bone. In this pilot study we wished to explore the value of a novel pulse sequence with an ultrashort echo time (UTE), which is able to detect signal from cortical bone and periosteum (Ref.). The signal obtained using an UTE sequence from cortical bone reflects the soft tissue component of cortical bone including its vasculature. We hypothesized that conditions, which alter the soft tissue component and vascularity of bone, show a change in signal. We have examined the lower limb in patients and volunteers of different age and at different time points following fracture of the tibia. Subjects and Methods: Seven volunteers (aged 29 – 85 years) and eight patients with acute fractures of the tibia (aged 18 – 56 years) were examined at different time points (2 days – 16 weeks) following fracture, in three of the patients serial scans were obtained. Three patients were examined years following bone injury: one patient with a hypertrophic mal-union at 5 years, one patient with polio 14 years following a tibial osteotomy and one patient 28 years following a tibial fracture. Ultra-short echo time pulse sequences (TE = 0.07 or 0.08 ms) were used with and without preceding fat suppression and / or long T2 component suppression pulses. Intravenous gadolinium (0.3 mmol/kg) was administered to one volunteer and three of the patients. Mean signal intensity (AU) was plotted against time following contrast enhancement. T1 and T2* values for cortical bone were determined and T1 was plotted against age. Results A signal was obtained of cortical bone, periosteum and callus in all subjects. The injection of contrast enhanced the signal in all of these tissues. Distribution curves of gadolinium in cortical bone showed enhanced signal intensity following fracture. The signal was dependent on the type and severity of fracture and the time following fracture. There was a marked increase in signal in a hypertrophic mal-union 5 years following fracture and a moderate increase in signal was still detectable 28 years following fracture. Osteoporosis associated with polio reduced volume and signal of bone. T1 echo times ranged from 140 – 260 ms and increased significantly with age (P < 0.01). T2* ranged from 0.42 – 0.50 ms. Fat suppression and long T2 suppression increased the conspicuity of the periosteum. Conclusion: Magnetic resonance imaging using UTE sequences is able to detect a signal from cortical bone for the first time. Cortical bone, callus and adult periosteum show a distinct signal following fracture with a characteristic time course. Measurements reflect the organic matrix rather than the inorganic crystals of bone. The T1 of cortical bone is very short and changes with age. The distribution curve of gadolinium can be established in cortical bone and is understood to reflect changes in blood flow. We present a pilot study to introduce a new MRI sequence, which at present a research tool, has potential for selected clinical application

Introduction

Bone fracture toughness is an important parameter in resistance of bone to monotonic and fatigue failure. Earlier studies on bone fracture toughness were focused on either cortical or cancellous bone, separately [1, 2]. Reported fracture toughness values indicated that cortical bone is tougher to break as compared to cancellous bone. In order to understand complete fracture of a whole bone, the interface between cortical and cancellous bone (named as corticellous bone) might play a crucial role and is interesting topic of research. The goal of this study was to identify fracture toughness in terms of J integral and fracture mechanism of the corticellous bone.

Formation of micro-cracks occurs in bone due to daily activities. Through a mechanism of self-repair, these micro-cracks are detected, and the damaged areas are restored, avoiding further propagation. The Scissors Model suggests that the osteocyte processes that cross the micro-cracks break as consequence of the cyclic displacements of the micro-crack faces, due to fatigue, and this triggers the remodelling processes. A fresh bovine tibia bone was cut in sections oriented 20° from the transversal direction. The cortical bone was sliced using a circular saw and shaped to the dimensions: 20 × 10 × 1 (mm) and the surfaces were polished. µCT images were obtained from all the samples (μCT 40, Scanco Medical, Brüttisellen, Switzerland). From the DICOM files, the geometries were reconstructed and meshed using tetrahedrons, in ICEM CFD. The Elasticity Modulus (E) was determined in Bonemat, by applying an empirical relationship Elasticity-Density from the literature. The parts were then imported into ANSYS APDL to simulate micro-crack propagation in bone. This model will be validated with further experimental work where the micro-crack will be initiated in the prepared samples and propagated due to fatigue loading, and the osteocyte processes will be visualized in the Scanning Electron Microscope (SEM). This investigation aims to study how cyclic loading in bones and failure of osteocyte processes can trigger target the mechanism of bone remodelling. The resulting model can later contribute for the investigation of treatments for bone diseases such as osteoporosis and the response of bone to the presence of orthopaedic implants.

Purpose: To assess the use of cortical allografts (bone plates?) in hip replacement surgery.

Materials and methods: This is a retrospective study of 43 bone plates in 36 hip prostheses. In 18 cases they were implanted to treat a periprosthetic fracture (an associated replacement of the femoral component was performed in 5 cases) and in 18 they were implanted to replace a loosened stem in a hip with large bone defects. Standard long uncemented stems were implanted in 7 cases and standard cemented stems associated with morselized compacted allografts were implanted in 16 cases. 14 patients were only given bone plates and in 22 these bone plates were associated to a metal plate. The mean age was 69.1 years (range: 38–82). 61.1% were female, 18% were implanted in the right side and the mean follow-up was 45.4 months.

Results: At the time of the last review, three patients had died but for reasons not related to their hip surgery. Transient sciatic nerve palsy was observed in one patient, prosthetic dislocation in three cases (two of them were successfully treated with bracing and the other had to be given a constrained cup), there was an infection (treated with a two-stage replacement) and two re-fractures (after 3 and 13 months) treated with a new osteosynthesis with a bone plate associated to a metal plate. All the fractures healed and the imaging tests showed an integration of the bone plate with the host bone with no signs of prosthetic loosening.

Conclusions: Cortical allografts can fulfill two functions: a mechanical one (they behave as if they were a plate) and a biological one (they increase bone stock on integration).

Background

Structural bone allografts are an established treatment method for long-bone structural defects arising from such conditions as trauma, sarcoma, and osteolysis following total joint replacement. However, the quality of structural bone allografts is difficult to non-destructively assess prior to use. The functional lifetime of structural allografts depend on their ability to resist cyclic loading, which can lead to fracture even at stress levels well below the yield strength. Because allograft bone has limited capacity for remodeling, optimizing allograft selection for bone quality could decrease long-term fracture risk. Raman spectroscopy biomarkers can non-destructively assess the three primary components of bone (collagen, mineral, and water), and may predict the resistance of donor bone allografts to fracture from cyclic loads.

The purpose of this study was to prospectively assess the ability of Raman biomarkers to predict number of cycles to fracture (“cyclic fatigue life”) of human allograft cortical bone.

Introduction: With aging and in disease, the changes in bone microstructure and geometry influence the mechanical properties of cortical bone. We examine the cross-section geometrical properties of cortical bone, area and second moment of inertia, and microstructural parameters in an ovine model of osteoporosis.

Methods: Twenty seven skeletally mature sheep were randomly divided into two groups: ovariectomy (OVX; n=11) and control (CON; n=16). Animals were sacrificed at 31 months following surgery. Compact bone samples were harvested from mid-diaphysis of the left and right metatarsal,4cm proximal to the metatarsal-phalangeal joint using a low speed diamond saw (Accutom 50, Struers, Ballerup, Denmark). For histological analysis, thin sections (150–200μm) were prepared. Each section was initially examined using brightfield microscopy (Olympus 1X51, Hamburg, Germany). Cortical area was measured using an image analysis system by measuring area enclosed by the perisoteal surface and subtracting the area of the medullary canal (analySIS, Soft Imaging systems, Munster, Germany). Sections were then examined using polarised light microscopy, cortical thickness was measured in four regions: anterior, posterior, medial and lateral. These regions were defined by finding the widest diameter of the medullary cavity of the section and drawing a line perpendicular through the midpoint. At each point total cortical thickness, periosteal thickness and endosteal thickness was measured. All measurements were scaled according to animal weight.

Results: The outer cortical area was significantly greater in the OVX group compared to CON (p=0.006), the inner medullary area was also greater in the OVX group, but not significant. The actual cortical area (outer cortical area – medullary area) was significantly greater in OVX (129.27mm2 vs 119.24 mm2, p=0.005). Second moment of inertia (I), was significantly greater in OVX (2.53 m4 v 2.21m4, p=0.002).

In all four cortical regions OVX was thicker than CON, however this never achieved significance. Similarly, in all four regions endosteal bone was thicker in OVX, but this was not significant. Periosteal bone was thicker in CON in the medial and lateral regions, whereas OVX periosteal bone was thicker in anterior and posterior regions (NS).

Conclusion: Our results demonstrate structural adaptation of cortical bone in a model of ovine osteoporosis. In theory these changes result in improved biomechanical properties of that bone; resistance to bending (second moment of inertia) and compressive strength (cross-sectional area). However in osteoporosis this biomechanical advantage is offset by diminution of bone quality.

Most of researches related to osteoporosis emphasized on trabecular bone loss. However, cortical bone has a prominent role on bone strength determined by bone quality, such as 2D or 3D geometry and microstructure of bone, not only density.[1] The focal thinning of cortical bone associated with aging in post-menopausal osteoporotic bone in the proximal femur may predispose a hip to fracture.[2, 3] As the trabecular bone is lost with progression of osteoporosis, the remaining cortical bone take more predominant role on bone strength.[4] To date, no effective osteoporotic agent was demonstrated to enhance both cortical geometric change and bone strength. Herein, we investigate the effect of Teriparatide (rhPTH(1–34)) on cortical bone at femoral diaphysis in OVX rat model.

Twenty 12-week-old, female Sprague Dawley rats were used in this study. Bilateral ovariectomies were performed in 16 animals and randomly divided to three groups as control (N=6), OVX (N=6) and treatment group after OVX (OVX+F) by teriparatide (N=8). After twelve weeks of intervention, all rats were euthanized and right femurs and L5 vertebrae were extracted for further tests. All bone specimens were subjected to dual-energy X-ray absorptiometer (DXA) to evaluate areal bone mineral density (aBMD) of L5 vertebrae and femurs, micro-computed tomography (micro-CT) to analyze cortical bone parameters of femoral diaphysis, including cortical cross section area (CSA), cortical thickness and cross-sectional moment of inertia (CSMI). A three-point bending test was applied to determine fracture load of each femurs.

Compare to OVX group, increase of aBMD by 14.6 % at L5 vertebrae and 13.3% at femoral diahpysis in treatment group. The cortical parameters of femoral diaphysis, CSA and cortical thickness, analyzed by micro-CT were significantly increased but the increasing tendency of CSMI did not have significant changes statistically after teriparatide intervention for 3 months duration. The increase of cortical bone strength (OVX vs OVX+F group, 120.72±2.72 vs 137.93±5.02, p < 0.05) at femoral diaphysis after treatment were also noticed.

This study has point out a deeper look at geometric change of cortical bone after teriparatide treatment. This finding imply teirparatide has the ability to change the geometry of cortical bone and increase bone strength at femoral diaphysis.

With information about a patient's bone mechanical properties orthopaedic operations could be optimised to reduce intra- and post-operative complications. However, there is currently no reliable method of measuring a patient's bone mechanical properties in vivo. We have previously investigated microindentation, using a 1.5mm diameter spherical indenter tip, and found no correlation between these measurements and compression testing measurements. We hypothesised that by using a larger diameter indenter tip we would closer match bone millimetre-scale mechanical properties.

20 bone samples were taken from 20 patients undergoing hip replacement surgery. The samples were machined from the femoral neck calcar cortical bone into 6×3×3mm parallelepiped specimens, aligned with the osteons along the long axis. The samples were micro-computed tomography (CT) scanned to calculate porosity. Microindentation was performed using a 6mm diameter, sapphire, spherical indenter tip. 12 indentations were performed in a grid and the reduced moduli were calculated using the Oliver-Pharr method. Compression testing was then performed to failure and the apparent elastic modulus was calculated for each sample.

A moderate correlation was found between the indentation reduced moduli and compression testing elastic moduli (r=0.52, r2=0.275, p=0.018). In addition, a moderate correlation was found between the indentation reduced moduli and CT-measured porosity (r=0.5, r2=0.251, p=0.025) and a strong correlation was found between compression testing moduli and porosity (r=0.75, r2=0.568, p<0.001).

Using large-tip spherical microindentation, indentation reduced moduli correlated significantly with compression testing apparent elastic moduli in these 20 cortical bone specimens. Microindentation using a large, spherical indenter tip may predict the mechanical properties of bone at the millimetre length scale and shows promise as a potential future clinical decision aid in surgery.

Objectives

Despite promising results have shown by osteogenic cell-based demineralized bone matrix composites, they need to be optimized for grafts that act as structural frameworks in load-bearing defects. The aims of this study is attempt to assess the effects of laser perforations on osteoinduction in cortical bone allografts.

Screw stripping in osteoporotic bone and bone of otherwise poor quality represents a common problem. Treatment alternatives, such as using a larger diameter screw or a longer plate, may add time, increase morbidity, be impractical, or simply be ineffective. Alternatively, the stripped screw can be augmented with a bone cement. A new injectable synthetic cortical bone void filler (Cor-toSSTM) is based on a resin system, resulting in a very strong, radiopaque, extensively crosslinked, biocompatible composite that does not resorb. We tested the safety and efficacy of the new bone cement in augmenting stripped screws until bone healing.

Of a total of 143 screws implanted in 24 patients with ankle fractures (average age 66. 8 years), 61 became stripped and were augmented. The primary efficacy endpoint was successful intraoperative screw augmentation. The secondary endpoint was whether screw fixation, determined radiologically, remained effective during the 3-month follow-up required for the fracture to heal.

All the stripped screws were successfully augmented. During follow-up at 24 hours, 7 days, and 1 month, none showed any movement relative to either the plate or the bone. At 3 months, one augmented screw in a patient with severe osteoporosis showed gross movement above the plate, which did not affect healing. Serial radiographic analysis did not show the development of any lucencies or cracks in the cement. All fractures healed within 3 months following surgery.

Screw augmentation allowed successful reduction and fixation of the fractures. No adverse events directly attributable to the device were observed. The new bone void filler represents a safe, simple, and reliable method by which to achieve stable internal fixation constructs in patients in whom bone screws fail to gain purchase due to poor bone quality or overtightening.

Aims: The shape and the structure of cortical bone of the diaphysis is the result of the continual resorption/ replacement process where the two phases have well regulated temporal sequence and spatial localization. Different methods can be employed to measure the appositional growth but their possible application to structural studies has not been so far considered.

The broad interest of this study was addressed to the mechanisms which control the structural modelling of cortical bone in the course of the long growth and development, therefore a morphometric evaluation appeared the more suitable method for the possibility to examine large segments of the bone.

Methods: The study was carried out on the femurs of four male New Zealand white rabbits. The left femurs were prepared with the techniques for undecalcified bone and studied in incedent fluorescent light. The right femurs were decalcified, prepared in sections and studied in bright field, in polarized light and in phase contrast.

Ditigital microscope images were analyzed utilizing the software Cell D: the cortical area was measured and the number of vascular canals was counted and expressed as a function of the cortical area (n/mm²). The total cortical area, the density of vascular canals and the frequency distribution for area classes in the cortex of mid-shaft and distal-shaft was compared with paired student t test and Pearson chi-square test respectively.

Results and Conclusions: The canals distribution for area classes showed a significant prevalence for actually structuring osteons in the distal shaft: these data demonstrate the higher rate of bone remodelling of the most recent apposed bone at the extremities of the shaft. On the contrary there were not significant differences among sectors at levels of the mid-shaft and distal-shaft.

Title

3D distribution of cortical bone thickness in the proximal humerus, implications for fracture management.

Introduction

The interstitial fluid of bone fluid flow is supplied by flowing blood. Blood flow is determined by three kinds of muscles: cardiac, smooth, and skeletal. Cardiac muscle establishes baseline blood pressure. Smooth muscle controls vessel diameter and skeletal muscle creates intermittent intravascular pressure pulses. For the tibia the relevant skeletal muscle is the gastrocnemius which functions as a muscle pump. This study tested the hypotheses: 1) skeletal muscle-caused pressure pulses increase cortical blood flow, 2) extravasation of vascular fluid and, consequently, interstitial bone fluid flow are enhanced by resultant increased microvascular pressure and 3) bone healing is enhanced by increased bone fluid flow.