New horizons for the in vivo assessment of major aspects of bone quality

The Biomechanically founded individualised osteoporosis Assessment and treatment (BioAsset) consortium pursues experimental and clinical studies in the context of skeletal effects of bisphosphonate treatment. Here, first results using newly developed diagnostic methods in a set of vertebral bone specimen obtained from donors with documented bisphosphonate history ranging from 0 to more than 5 years of treatment are presented. A new thoracolumbar quantitative computed tomography (QCT) protocol covering T6 to L4 plus high-resolution QCT (HRQCT) assessment of T12 were compared with high-resolution peripheral QCT (HRpQCT) and micro-CT scans of excised specimens serving as gold standard techniques. Finite element (FE) modelling was performed. Material, ultrastructural, and micromechanical properties were tested on a set of single trabeculae obtained from the donor specimens. A newly developed quantitative ultrasound (QUS) device for measuring the anisotropy of cortical material properties at the tibia was designed and built. The thoracolumbar QCT protocol permitted in situ imaging with good image quality and automated segmentation of vertebral bodies in the whole range from T6 to L4. The duration of bisphosphonate treatment was significantly associated with increased levels of mineralization and this effect could be measured with HRQCT performed on excised specimens. Microstructural parameters contributed to vertebral bone strength modelled by FE analysis independently of bone mineral density. The new QUS tibia scanner permitted measuring the acoustical anisotropy of reference materials. Taken together, these results document that new methods developed in BioAsset permit a more comprehensive assessment of bone fragility. The set of donor specimens with a documented history of bisphosphonate treatment allows for the assessment of the effects of long-term treatment from the organ down to the tissue and material level. These results will ultimately be linked to the parallel clinical study to provide guidance for determining the optimum duration of bisphosphonate treatment to reduce the incidence of osteoporotic fractures.

Traumatic Rupture of the Distal Triceps Tendon (A Series of 7 Cases)

Even non-traumatic ruptures of the triceps tendon are rare, surgical therapy should be recommended in all cases, because of poor results after non-operative treatment. A golden standard for the surgical procedure is not established. A small series of traumatic distal tendon ruptures was treated surgical in our hospital and was followed up after 12 months concerning their function. Very good and good results could be found with a strong reintegration of the tendon by using transosseus sutures with non resorbable suture material. The refixation with suture anchors showed disappointing results with early pull-outs of the anchor. Revision with screw augmentation with a washer had to be performed. Concerning the biomechanical forces, which show up on the olecranon (up to 40 NM), the refixation of the triceps tendon has proved to be extremely resistant against pull out forces. The good results by using non absorbable transosseus sutures led to a standardized procedure in our trauma center, even the rupture is not traumatic.

Effects of long-term alendronate treatment on bone mineralisation, resorption parameters and biomechanics of single human vertebral trabeculae

Due to their well-established fracture risk reduction, bisphosphonates are the most frequently used therapeutic agent to treat osteoporosis. Bisphosphonates reduce fracture risk by suppressing bone resorption, but the lower bone turnover could have a negative impact on bone quality at the tissue level. Here, we directly assess the structural and mechanical characteristics of cancellous bone from the lumbar vertebrae (L5) in non-treated osteoporotic controls (n=21), mid-term alendronate-treated osteoporotic patients (n=6), and long-term alendronate-treated osteoporotic patients (n=7). The strength and toughness of single trabeculae were evaluated, while the structure was characterised through measurements of microdamage accumulation, mineralisation distribution, and histological indices. The alendronate-treated cases had a reduced eroded surface (ES/BS, p<0.001) and a higher bone mineralisation in comparison to non-treated controls (p=0.037), which is indicative of low turnover associated with treatment. However, the amount of microdamage and the mechanical properties were similar among the control and treatment groups. As the tissue mineral density (TMD) increased significantly with alendronate treatment compared to non-treated osteoporotic controls, the reduction in resorption cavities could counterbalance the higher TMD allowing the alendronate-treated bone to maintain its mechanical properties and resist microdamage accumulation. A multivariate analysis of the possible predictors supports the theory that multiple factors (e.g., body mass index, TMD, and ES/BS) can impact the mechanical properties. Our results suggest that long-term alendronate treatment shows no adverse impact on mechanical cancellous bone characteristics.

Accuracy of trabecular structure by HR-pQCT compared to gold standard μCT in the radius and tibia of patients with osteoporosis and long-term bisphosphonate therapy

Despite an increasing use of high-resolution peripheral quantitative computed tomography (HR-pQCT) to evaluate bone morphology in vivo, there are reservations about its applicability in patients with osteoporosis and antiresorptive therapy. This study shows that HR-pQCT provides acceptable in vivo accuracy for bone volume fraction (BV/TV) in patients with osteoporosis and bisphosphonate (BP) treatment.

INTRODUCTION

The primary aim was to analyze agreement of trabecular structure between HR-pQCT and gold standard microtomography (μCT) in patients with osteoporosis and long-term BP therapy.

METHODS

In the BioAsset study, we analyzed cadaver radii and tibiae of 34 postmenopausal females (81.1 ± 7.1 years) with osteoporosis (no BP n = 22, 1-5 years BP n = 5, >5 years BP n = 7). Two HR-pQCT protocols (patient-mode and μCT-mode) were compared with gold standard μCT after image registration. Undecalcified histological sections were obtained to quantify nonmineralized bone matrix. Bland-Altman plots illustrated methodological agreement. Multiple regression analysis was used to test for variables associated with method agreement.

RESULTS

In the radius and tibia, patient-mode HR-pQCT derived indices including bone volume fraction, trabecular number, and trabecular separation correlated well with gold standard μCT (R(2) = 0.78 - 0.88) except for trabecular thickness (R(2) = 0.11). Bland-Altman plots illustrated adequate agreement for bone volume fraction. Lower agreement of trabecular number and trabecular separation improved with decreasing structural impairment at the tibia only. Trabecular thickness was not appropriately assessed with HR-pQCT at both skeletal sites. Higher agreement for bone volume fraction was associated with increasing tissue mineral density in the tibia.

CONCLUSIONS

HR-pQCT provides acceptable in vivo accuracy for BV/TV in patients with osteoporosis and BP treatment. Higher TMD was associated with higher BV/TV accuracy in vivo. Overall, methodological agreement got less accurate with increasing structural impairment in the tibia.

Micro-morphological properties of osteons reveal changes in cortical bone stability during aging, osteoporosis, and bisphosphonate treatment in women

SUMMARY

We analyzed morphological characteristics of osteons along with the geometrical indices of individual osteonal mechanical stability in young, healthy aged, untreated osteoporotic, and bisphosphonate-treated osteoporotic women. Our study revealed significant intergroup differences in osteonal morphology and osteocyte lacunae indicating different remodeling patterns with implications for fracture susceptibility.

INTRODUCTION

Bone remodeling is the key process in bone structural reorganization, and its alterations lead to changes in bone mechanical strength. Since osteons reflect different bone remodeling patterns, we hypothesize that the femoral cortices of females under miscellaneous age, disease and treatment conditions will display distinct osteonal morphology and osteocyte lacunar numbers along with different mechanical properties.

METHODS

The specimens used in this study were collected at autopsy from 35 female donors (young group, n = 6, age 32 ± 8 years; aged group, n = 10, age 79 ± 9 years; osteoporosis group, n = 10, age 81 ± 9 years; and bisphosphonate group, n = 9, age 81 ± 7 years). Von Kossa-modified stained femoral proximal diaphyseal sections were evaluated for osteonal morphometric parameters and osteocyte lacunar data. Geometrical indices of osteonal cross-sections were calculated to assess the mechanical stability of individual osteons, in terms of their resistance to compression, bending, and buckling.

RESULTS

The morphological assessment of osteons and quantification of their osteocyte lacunae revealed significant differences between the young, aged, osteoporosis and bisphosphonate-treated groups. Calculated osteonal geometric indices provided estimates of the individual osteons' resistance to compression, bending and buckling based on their size. In particular, the osteons in the bisphosphonate-treated group presented improved osteonal geometry along with increased numbers of osteocyte lacunae that had been formerly impaired due to aging and osteoporosis.

CONCLUSIONS

The data derived from osteons (as the basic structural units of the cortical bone) in different skeletal conditions can be employed to highlight structural factors contributing to the fracture susceptibility of various groups of individuals.

Influence of non-traumatic thoracic and lumbar vertebral fractures on sagittal spine alignment assessed by radiation-free spinometry

Due to missing indications for specific diagnostics, the majority of non-symptomatic vertebral fractures are not diagnosed. This study shows the ability of radiation-free spinometry to assess sagittal spine parameters to raise suspicion for new non-traumatic thoracic and lumbar vertebral fractures and indicate specific diagnostics.

INTRODUCTION

The primary aim of this study was to investigate the accuracy of radiation-free spinometry to predict new non-traumatic vertebral fractures (VF) by the assessment of thoracic kyphosis (TK), lumbar lordosis (LL), and trunk inclination.

METHODS

Three hundred sixty-one patients (278 females and 83 males; age, 67.0 ± 8.6 years) were enrolled. In 86 women and 24 men, at least one non-traumatic VF was confirmed by radiography, MRI, and/or CT. Spinometry (video rasterstereography) was used to assess TK, LL, and trunk inclination. Receiver operating characteristic (ROC) and multivariate logistic regression analyses were performed to test the influence of age, sex, number, location, and grade of fractures on sagittal spine alignment.

RESULTS

TK, LL, and trunk inclination were associated with advancing age (p < 0.05). Patients with prevalent thoracic and lumbar VFs showed increased TK (p < 0.001), decreased LL (p < 0.001), and increased trunk inclination (p < 0.001) in comparison to patients without VFs. ROC analysis revealed that the combination of TK and LL presented with the best predictive accuracy to raise suspicion for new grade 2 or grade 3 VFs in the thoracic and the lumbar spine (AUC, 0.752-0.771). Odds ratio (OR) showed an increased risk for VFs with increased TK (OR, 1.05-1.11; p < 0.001) and LL (1.05-1.07; p < 0.001) in specified regions of interest. A TK <50° (sensitivity, 88-100 %; specificity, 23-25 %) and LL (78-92 %; 24-27 %) were considered as appropriate cutoffs for future screening.

CONCLUSION

Spinometry showed better predictive accuracy than historical height loss. Severe changes of TK and LL may help to raise suspicion of new VFs radiation-free and indicate proper diagnostics, such as radiographs, MRI, or CT.

Spontaneous osteonecrosis of the knee (SONK)

PURPOSE

Spontaneous osteonecrosis of the knee (SONK/Morbus Ahlback) mainly affects the medial condyle of elderly women. It is assumed that localized vascular insufficiency leads to necrosis of the subchondral bone with subsequent disruption of the nutrition supply to the cartilage above. The aetiology remains unclear in detail. Operative treatment procedures compete against non-operative strategies, whereas the outcome is unpredictable in many cases.

METHOD

A consecutive case series of five patients suffering from SONK was analysed. All patients underwent a clinical examination, magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry scan, as well as laboratory analyses and visual analogue scale (VAS) evaluation. Our treatment regime is based on high-dose vitamin D administered orally and intravenous application of 3 mg ibandronate two times within 8 weeks. Another 8 weeks later, all patients were followed up including a follow-up MRI.

RESULTS

Within 4 weeks, all patients were free of symptoms. The MRI follow-up showed remission of the bone marrow oedema in every case studied. VAS decreased significantly from 7.4 ± 1.0 pre-interventional to 0.8 ± 1.0 post-interventional. No allergic reactions or other side effects were documented.

CONCLUSION

We showed that our treatment regime not only eliminated the pathological findings in the MRI of all cases studied, but also decreased the pain level and functional limitations within a short-time period.

LEVEL OF EVIDENCE

IV.

Osteocalcin is associated with testosterone in the general population and selected patients with bone disorders

Research in the last decade has revealed that bone is not only a target tissue for numerous circulating hormones but functions as an endocrine organ itself. As a recent study demonstrated a stimulatory effect of the osteoblast-derived hormone osteocalcin (OCN) on testosterone production in mice, we investigated whether such an association can be replicated in humans. We used data from 1338 men (25-86 years) in the population-based epidemiological Study of Health in Pomerania and from 110 male outpatients with bone disorders (18-85 years) for the study. We analysed cross-sectional associations between OCN and total testosterone serum concentrations (TT), as well as associations between further markers of bone turnover [bone-specific alkaline phosphatase (BAP), serum C-terminal telopeptides of Type I collagen (CTX), urinary deoxypyridinoline] and TT using ordinary least square (OLS) regression models. Multivariable OLS models revealed a positive association between OCN and TT in the population-based (β coefficients for a one standard deviation increase, 0.590; standard error (SE), 0.175; p-value, <0.01) and patient-based (β coefficient, 0.575; SE, 0.132; p-value, <0.01) samples even after adjustment for age and body mass index (both samples), and time of blood sampling (population-based sample only). Furthermore, we observed positive associations between BAP and TT (β coefficient, 0.403; SE, 0.170; p-value, 0.02) as well as between CTX and TT (β coefficient, 0.733; SE, 0.172; p-value, <0.01) in men from the general population. The present investigation shows that OCN is associated with TT in the general population and in patients with bone disorders, and may thus indicate general male health status. Additional longitudinal observational studies are warranted to confirm our findings and future experimental research is necessary to elucidate potential mechanisms underlying the observed associations.

Improved development of thermally fixed holograms in photorefractive LiNbO(3) crystals with high-intensity laser pulses

Holographic gratings were thermally fixed in iron-doped photorefractive LiNbO(3) crystals and developed with frequency-doubled Q -switched pulses of a Nd:YAG laser (light wavelength, 532 nm; pulse duration, 3 ns). The saturation values of the diffraction efficiency increased with increasing pulse light intensity. Compared with development with cw light, high-intensity laser pulse development resulted in an enlargement of the diffraction efficiency of a factor of ~2 . A contribution of the intrinsic defect Nb on Li site to the charge transport is most probably the origin of this effect. The results are useful, e.g., for improvements of volume holographic memories and wavelength filters.