Fabric-mechanical property relationships of trabecular bone allografts are altered by supercritical CO2 treatment and gamma sterilization

Tissue grafts are implanted in orthopedic surgery every day. In order to minimize infection risk, bone allografts are often delipidated with supercritical CO2 and sterilized prior to implantation. This treatment may, however, impair the mechanical behavior of the bone graft tissue. The goal of this study was to determine clinically relevant mechanical properties of treated/sterilized human trabecular bone grafts, e.g. the apparent modulus, strength, and the ability to absorb energy during compaction. They were compared with results of identical experiments performed previously on untreated/fresh frozen human trabecular bone from the same anatomical site (Charlebois, 2008). We tested the hypothesis that the morphology–mechanical property relationships of treated cancellous allografts are similar to those of fresh untreated bone. The morphology of the allografts was determined by μCT. Subsequently, cylindrical samples were tested in unconfined and confined compression. To account for various morphologies, the experimental data was fitted to phenomenological mechanical models for elasticity, strength, and dissipated energy density based on bone volume fraction (BV/TV) and the fabric tensor determined by MIL. The treatment/sterilization process does not appear to influence bone graft stiffness. However, strength and energy dissipation of the bone grafts were found to be significantly reduced by 36% to 47% and 66% to 81%, respectively, for a broad range of volume fraction (0.14 < BV/TV < 0.39) and degree of anisotropy (1.24 < DA < 2.18). Since the latter properties are strongly dominated by BV/TV, the clinical consequences of this reduction can be compensated by using grafts with lower porosity. The data of this study suggests that an increase of 5–10% in BV/TV is sufficient to compensate for the reduced post-yield mechanical properties of treated/sterilized bone in monotonic compression. In applications where graft stiffness needs to be matched and strength is not a concern, treated allograft with the same BV/TV as an appropriate fresh bone graft may be used.

Comparative effects of Teriparatide and Risedronate in glucocorticoid‐induced osteoporosis in men: 18‐month results of the EuroGIOPs trial

Data on treatment of glucocorticoid-induced osteoporosis (GIO) in men are scarce. We performed a randomized, open-label trial in men who have taken glucocorticoids (GC) for ≥3 months, and had an areal bone mineral density (aBMD) T-score ≤ –1.5 standard deviations. Subjects received 20 μg/d teriparatide (n = 45) or 35 mg/week risedronate (n = 47) for 18 months. Primary objective was to compare lumbar spine (L1–L3) BMD measured by quantitative computed tomography (QCT). Secondary outcomes included BMD and microstructure measured by high-resolution QCT (HRQCT) at the 12th thoracic vertebra, biomechanical effects for axial compression, anterior bending, and axial torsion evaluated by finite element (FE) analysis from HRQCT data, aBMD by dual X-ray absorptiometry, biochemical markers, and safety. Computed tomography scans were performed at 0, 6, and 18 months. A mixed model repeated measures analysis was performed to compare changes from baseline between groups. Mean age was 56.3 years. Median GC dose and duration were 8.8 mg/d and 6.4 years, respectively; 39.1% of subjects had a prevalent fracture, and 32.6% received prior bisphosphonate treatment. At 18 months, trabecular BMD had significantly increased for both treatments, with significantly greater increases with teriparatide (16.3% versus 3.8%; p = 0.004). HRQCT trabecular and cortical variables significantly increased for both treatments with significantly larger improvements for teriparatide for integral and trabecular BMD and bone surface to volume ratio (BS/BV) as a microstructural measure. Vertebral strength increases at 18 months were significant in both groups (teriparatide: 26.0% to 34.0%; risedronate: 4.2% to 6.7%), with significantly higher increases in the teriparatide group for all loading modes (0.005 < p < 0.015). Adverse events were similar between groups. None of the patients on teriparatide but five (10.6%) on risedronate developed new clinical fractures (p = 0.056). In conclusion, in this 18-month trial in men with GIO, teriparatide showed larger improvements in spinal BMD, microstructure, and FE-derived strength than risedronate.

In situ micropillar compression reveals superior strength and ductility but an absence of damage in lamellar bone

Ageing societies suffer from an increasing incidence of bone fractures. Bone strength depends on the amount of mineral measured by clinical densitometry, but also on the micromechanical properties of the hierarchical organization of bone. Here, we investigate the mechanical response under monotonic and cyclic compression of both single osteonal lamellae and macroscopic samples containing numerous osteons. Micropillar compression tests in a scanning electron microscope, microindentation and macroscopic compression tests were performed on dry ovine bone to identify the elastic modulus, yield stress, plastic deformation, damage accumulation and failure mechanisms. We found that isolated lamellae exhibit a plastic behaviour, with higher yield stress and ductility but no damage. In agreement with a proposed rheological model, these experiments illustrate a transition from a ductile mechanical behaviour of bone at the microscale to a quasi-brittle response driven by the growth of cracks along interfaces or in the vicinity of pores at the macroscale.

Risk of late effects of treatment in children newly diagnosed with standard-risk acute lymphoblastic leukaemia: a report from the Childhood Cancer Survivor Study cohort

BACKGROUND Treatment of patients with paediatric acute lymphoblastic leukaemia has evolved such that the risk of late effects in survivors treated in accordance with contemporary protocols could be different from that noted in those treated decades ago. We aimed to estimate the risk of late effects in children with standard-risk acute lymphoblastic leukaemia treated with contemporary protocols. METHODS We used data from similarly treated members of the Childhood Cancer Survivor Study cohort. The Childhood Cancer Survivor Study is a multicentre, North American study of 5-year survivors of childhood cancer diagnosed between 1970 and 1986. We included cohort members if they were aged 1·0-9·9 years at the time of diagnosis of acute lymphoblastic leukaemia and had received treatment consistent with contemporary standard-risk protocols for acute lymphoblastic leukaemia. We calculated mortality rates and standardised mortality ratios, stratified by sex and survival time, after diagnosis of acute lymphoblastic leukaemia. We calculated standardised incidence ratios and absolute excess risk for subsequent neoplasms with age-specific, sex-specific, and calendar-year-specific rates from the Surveillance, Epidemiology and End Results Program. Outcomes were compared with a sibling cohort and the general US population. FINDINGS We included 556 (13%) of 4329 cohort members treated for acute lymphoblastic leukaemia. Median follow-up of the survivors from 5 years after diagnosis was 18·4 years (range 0·0-33·0). 28 (5%) of 556 participants had died (standardised mortality ratio 3·5, 95% CI 2·3-5·0). 16 (57%) deaths were due to causes other than recurrence of acute lymphoblastic leukaemia. Six (1%) survivors developed a subsequent malignant neoplasm (standardised incidence ratio 2·6, 95% CI 1·0-5·7). 107 participants (95% CI 81-193) in each group would need to be followed-up for 1 year to observe one extra chronic health disorder in the survivor group compared with the sibling group. 415 participants (376-939) in each group would need to be followed-up for 1 year to observe one extra severe, life-threatening, or fatal disorder in the group of survivors. Survivors did not differ from siblings in their educational attainment, rate of marriage, or independent living. INTERPRETATION The prevalence of adverse long-term outcomes in children treated for standard risk acute lymphoblastic leukaemia according to contemporary protocols is low, but regular care from a knowledgeable primary-care practitioner is warranted. FUNDING National Cancer Institute, American Lebanese-Syrian Associated Charities, Swiss Cancer Research.

Influence of intervertebral disc fenestration at the herniation site in association with hemilaminectomy on recurrence in chondrodystrophic dogs with thoracolumbar disc disease: a prospective MRI study

OBJECTIVE To describe the influence of fenestration at the disc herniation site on recurrence in thoracolumbar disc disease of chondrodystrophoid dogs. STUDY DESIGN Prospective clinical study. ANIMALS Chondrodystrophic dogs (n=19). METHODS Dogs were divided into 2 groups: group 1 (9 dogs) had thoracolumbar disc extrusion (Hansen type I) treated by hemilaminectomy and concomitant fenestration of the affected intervertebral disc and group 2 (10 dogs) had hemilaminectomy without fenestration. All dogs had 3 magnetic resonance imaging (MRI) examinations: preoperatively, immediately postoperatively to assess removal of herniated disc material, and again 6 weeks after surgery. RESULTS There were 13 male and 6 female dogs; mean age, 7.1 years. Thoracolumbar disc herniation was confirmed with MRI. Immediate post surgical MRI revealed that the herniated disc removal was complete in all but 1 dog and that fenestration did not lead to complete removal of nucleus pulposus within the intervertebral disc space. On the 3rd MRI examination, none of the group 1 dogs had further disc material herniation at the fenestrated site. Six of the 10 group 2 dogs had a recurrence of herniation leading to clinical signs in 3 dogs (pain in 2 dogs, paresis in 1 dog). CONCLUSION In thoracolumbar disc herniation, fenestration of the affected intervertebral disc space prevents further extrusion of disc material. CLINICAL RELEVANCE Fenestration reduces the risk of early recurrence of disc herniation and associated postoperative complications.

Use of contrast-enhanced fluid-attenuated inversion recovery sequence to detect brain lesions in dogs and cats.

BACKGROUND The diagnostic value of a contrast-enhanced T2-weighted FLAIR sequence (ceFLAIR) in brain imaging is unclear. HYPOTHESIS/OBJECTIVES That the number of brain lesions detected with ceFLAIR would be no greater than the sum of lesions detected with nFLAIR and ceT1W sequence. ANIMALS One hundred and twenty-nine animals (108 dogs and 21 cats) undergoing magnetic resonance imaging (MRI) of the head between July 2010 and October 2011 were included in the study. METHODS A transverse ceFLAIR was added to a standard brain MRI protocol. Presence and number of lesions were determined based on all available MRI sequences by 3 examiners in consensus and lesion visibility was evaluated for nFLAIR, ceFLAIR, and ceT1W sequences. RESULTS Eighty-three lesions (58 intra-axial and 25 extra-axial) were identified in 51 patients. Five lesions were detected with nFLAIR alone, 2 with ceT1W alone, and 1 with ceFLAIR alone. Significantly higher numbers of lesions were detected using ceFLAIR than nFLAIR (76 versus 67 lesions; P = 0.04), in particular for lesions also detected with ceT1W images (53 versus 40; P =.01). There was no significant difference between the number of lesions detected with combined nFLAIR and ceT1W sequences compared to those detected with ceFLAIR (82 versus 76; P =.25). CONCLUSION AND CLINICAL IMPORTANCE Use of ceFLAIR as a complementary sequence to nFLAIR and ceT1W sequences did not improve the detection of brain lesions and cannot be recommended as part of a routine brain MRI protocol in dogs and cats with suspected brain lesions.

Combining Enzalutamide with Abiraterone, Prednisone, and Androgen Deprivation Therapy in the STAMPEDE Trial.

There are compelling reasons to study the addition of both enzalutamide and abiraterone, in combination, to standard-of-care for hormone-naïve prostate cancer. Through a protocol amendment, this will be assessed in the STAMPEDE trial, with overall survival as primary outcome measure.