Safety of OPRA procedure for individuals with upper limb amputation

Surgical implantations of osseointegrated fixations for bone-anchored prosthesis are developing at an unprecedented pace worldwide while initial skepticism in the orthopedic community is slowly fading away. Clearly, this option is becoming accessible to a wide range of individuals with limb loss. [1-18] The team led by Dr Rickard Branemark has previously published a number of landmark articles focusing on the benefits and safety of the OPRA fixation mainly for individual with lower limb loss, particularly those with transfemoral amputation. [1-3, 19-32] However, similar information is lacking for those with upper limb amputation. This team is once again taking a leading role by sharing a retrospective study focusing on the implant survival, adverse events, implant stability, and bone remodelling for 18 individuals with transhumeral amputation over a 5-year post-operative period. Therefore, a comprehensive analysis of the safety of the procedure is accessible for the first time. In essence, the results showed an implant survival rate of 83% and 80% at 2 and 5 year follow ups, respectively. The most frequent adverse events were superficial skin infections that occurred for 28% (5) participants while the least frequent was deep bone infection that happened only once. More importantly, 38% of complications due to infections were effectively managed with nonoperative treatments (e.g., revision of skin penetration site, local cleaning, antibiotics, restriction of soft tissue mobility). Implant stability and bone remodelling were satisfactory. Clearly, this study provided better understanding of the safety of the OPRA surgical and rehabilitation procedure for individuals with upper limb amputation while establishing standards and benchmark data for future studies. However, strong evidences of the benefits are yet to be demonstrated. However, increase in health related quality of life and functional outcomes (e.g., range of movement) are likely. Altogether, the team of authors are providing further evidence that bone-anchored attachment is definitely a promising alternative to socket prostheses.

Prospective ten-month exercise intervention in premenarcheal girls: Positive effects on bone and lean mass

Enhancement of bone mineral acquisition during growth may be a useful preventive strategy against osteoporosis. The aim of this study was to explore the lean mass, strength, and bone mineral response to a 10-month, high-impact, strength-building exercise program in 71 premenarcheal girls, aged 9–10 years. Lean body mass, total body (TB), lumbar spine (LS), proximal femur (PF), and femoral neck (FN) bone mineral were measured using the Hologic QDR 2000+ bone densitometer. Strength was assessed using a grip dynamometer and the Cybex isokinetic dynamometer (Cybex II). At baseline, no significant difference in body composition, pubertal development, calcium intake, physical activity, strength, or bone mineral existed between groups. At completion, there were again no differences in height, total body mass, pubertal development, calcium intake, or external physical activity. In contrast, the exercise group gained significantly more lean mass, less body fat content, greater shoulder, knee and grip strength, and greater TB, LS, PF, and FN BMD (exercise: TB 3.5%, LS 4.8%, PF 4.5%, and FN 12.0%) compared with the controls (controls: TB 1.2%, LS 1.2%, PF 1.3%, and FN 1.7%). TB bone mineral content (BMC), LS BMC, PF BMC, FN BMC, LS bone mineral apparent density (BMAD), and FN bone area also increased at a significantly greater rate in the exercise group compared with the controls. In multiple regression analysis, change in lean mass was the primary determinant of TB, FN, PF, and LS BMD accrual. Although a large proportion of bone mineral accrual in the premenarcheal skeleton was related to growth, an osteogenic effect was associated with exercise. These results suggest that high-impact, strength building exercise is beneficial for premenarcheal strength, lean mass gains, and bone mineral acquisition.

The impact of intense training on endogenous estrogen and progesterone concentrations and bone mineral acquisition in adolescent rowers

The effect of 18 months of training on the ovarian hormone concentrations and bone mineral density (BMD) accrual was assessed longitudinally in 14 adolescent rowers and 10 matched controls, aged 14–15 years. Ovarian hormone levels were assessed by urinary estrone glucuronide (E1G) and pregnanediol glucuronide (PdG) excretion rates, classifying the menstrual cycles as ovulatory or anovulatory. Total body (TB), total proximal femur (PF), femoral neck (FN) and lumbar spine (LS) (L2–4) bone mass were measured at baseline and 18 months using dual-energy X-ray densitometry. Results were expressed as bone mineral content (BMC), BMD and bone mineral apparent density (BMAD). Five rowers had anovulatory menstrual cycles compared with zero prevalence for the control subjects. Baseline TB BMD was significantly higher in the ovulatory rowers, with PF BMD, FN BMD and LS BMD similar for all groups. At completion, the LS bone accrual of the ovulatory rowers was significantly greater (BMC 8.1%, BMD 6.2%, BMAD 6.2%) than that of the anovulatory rowers (BMC 1.1%, BMD 3.9%, BMAD 1.6%) and ovulatory controls (BMC 0.5%, BMD 1.1%, BMAD 1.1%). No difference in TB, PF or FN bone accrual was observed among groups. This study demonstrated an osteogenic response to mechanical loading, with the rowers accruing greater bone mass than the controls at the lumbar spine. However, the exercise-induced osteogenic benefits were less when rowing training was associated with low estrogen and progesterone metabolite excretion.

Changes in cervical spine bone mineral density in response to flight training

BACKGROUND High magnitude loads and unusual loading regimes are two important determinants for increasing bone mass. Past research demonstrated that positive Gz-induced loading, providing high loads in an unaccustomed manner, had an osteogenic effect on bone. Another determinant of bone mass is that the bone response to loading is site specific. This study sought to further investigate the site specific bone response to loading, examining the cervical spine response, the site suspected of experiencing the greatest loading, to high performance flight. METHODS Bone mineral density (BMD) and bone mineral content (BMC) was monitored in 9 RAAF trainee fighter pilots completing an 8-mo flight training course on a PC-9 and 10 age-height-weight-matched controls. RESULTS At completion of the course, the pilots had a significant increase in cervical spine BMD and total body BMC. No significant changes were found for the control group. CONCLUSIONS This study demonstrated that the physical environment associated with flight training may have contributed to a significant increase in cervical spine bone mass in the trainee PC-9 pilots. The increase in bone mass was possibly a response to the strain generated by the daily wearing of helmet and mask assembly under the influence of positive sustained accelerative forces.

Exercise, Nutrition, and Bone Health

Optimal bone metabolism is the result of hormonal, nutritional, and mechanical harmony, and a deficit in one area is usually impossible to overcome by improvements in others. Exercise during growth influences bone modeling locally at the regions being loaded, whereas calcium is thought to act systemically to influence bone remodeling. Despite acting through different mechanisms, a growing body of research suggests that exercise and calcium may not operate independently. Low dietary calcium intake or reduced bioavailability may minimize the adaptive response to exercise-induced bone loading. Conversely, adequate levels of calcium intake can maximize the positive effect of physical activity on bone health during the growth period of children and adolescents. Research also suggests that adequate levels of calcium intake can maximize bone density at the regions being loaded during exercise. Achieving optimal bone health and minimizing one’s risk of osteoporotic fracture later in life depend on a lifelong approach. This approach relies on the establishment of an optimum level of bone during the growth years, with a subsequent goal to maintain and slow the rate of age-related bone loss thereafter. Exercise, adequate nutrition, and optimal hormone levels are the components that influence the bone outcome. Making healthy nutritional choices, engaging in weight-bearing physical activity, and ensuring optimal hormone levels during growth provides a window of opportunity to build optimal bone mass, to reduce the risk of fracture later in life. Concurrent management of fracture risk with a physical activity prescription, adequate nutrition, and pharmacotherapy for osteoporosis when required offers the best approach to optimal bone health throughout adulthood.

A humanized tissue-engineered in vivo model to dissect interactions between human prostate cancer cells and human bone

Currently used xenograft models for prostate cancer bone metastasis lack the adequate tissue composition necessary to study the interactions between human prostate cancer cells and the human bone microenvironment. We introduce a tissue engineering approach to explore the interactions between human tumor cells and a humanized bone microenvironment. Scaffolds, seeded with human primary osteoblasts in conjunction with BMP7, were implanted into immunodeficient mice to form humanized tissue engineered bone constructs (hTEBCs) which consequently resulted in the generation of highly vascularized and viable humanized bone. At 12 weeks, PC3 and LNCaP cells were injected into the hTEBCs. Seven weeks later the mice were euthanized. Micro-CT, histology, TRAP, PTHrP and osteocalcin staining results reflected the different characteristics of the two cell lines regarding their phenotypic growth pattern within bone. Microvessel density, as assessed by vWF staining, showed that tumor vessel density was significantly higher in LNCaP injected hTEBC implants than in those injected with PC3 cells (p\0.001). Interestingly, PC3 cells showed morphological features of epithelial and mesenchymal phenotypes suggesting a cellular plasticity within this microenvironment. Taken together, a highly reproducible humanized model was established which is successful in generating LNCaP and PC3 tumors within a complex humanized bone microenvironment. This model simulates the conditions seen clinically more closely than any other model described in the literature to date and hence represents a powerful experimental platform that can be used in future work to investigate specific biological questions relevant to bone metastasis.

The cost and time effectiveness of osseointegration compared to the traditional socket prosthesis

Individuals with limb amputation fitted with conventional socket-suspended prostheses often experience socket related discomfort leading to a significant decrease in quality of life.[1-14] Most of these concerns can be overcome with osseointegration, a direct skeletal fixation method where the prosthetic componentry are directly attached to the fixation, resulting in the redundancy of the traditional socket system. There are two stages of osseointegration; Stage one, a titanium implant is inserted into the marrow space of residual limb bone and Stage two, a titanium extension is attached to the fixture. This surgical procedure is currently blooming worldwide, particularly within Queensland. Whilst providing improvements in quality of life, this new method also has potential to minimise the cost required for an amputee to ambulate during daily living. Thus, the aim of this project was to compare the differences in mean cost of services, cost of componentry and labour hours when using osseointegration compared to traditional socket-based prostheses. Data were extracted from Queensland Artificial Limb Services (QALS) database to determine cost of services, type of services and labour hours required to maintain a prosthetic limb. Five trans-femoral amputee male participants (age 46.4±10.1 yrs; height 175.4±16.3 cm; mass 83.8±14.0 kg; time since second stage 22.0± 8.1 mths) met inclusion criteria which was patient had to be more than 12 months post stage two osseointegration procedure. The socket and osseointegration prosthesis variables examined were the mean hours of labour, mean cost of services and mean cost of prosthetic componentry. Statistical analyses were conducted using an ANOVA. The results identified that there were only significant differences in the number of labour hours (p = 0.005) and cost of services (p = 0.021) when comparing the socket and osseointegration prosthetic type. These results identified that the cost of componentry were comparable between the two methods.

Tissue engineering of a morphologically and functionally intact humanized bone organ for bone metastasis research

The aim of this thesis was to establish an individualized, patient-specific diagnostic and therapeutic preclinical disease model for bone metastasis research. Tissue engineering of humanized bone within mice allowed the development of a humanized immune system in the host animal. This novel platform makes it possible to analyze the growth of human cancer cells in human bone in the presence of human immune cells.

High-throughput bone and cartilage micropellet manufacture, followed by assembly of micropellets into biphasic osteochondral tissue

Engineered biphasic osteochondral tissues may have utility in cartilage defect repair. As bone-marrow-derived mesenchymal stem/stromal cells (MSC) have the capacity to make both bone-like and cartilage-like tissues, they are an ideal cell population for use in the manufacture of osteochondral tissues. Effective differentiation of MSC to bone-like and cartilage-like tissues requires two unique medium formulations and this presents a challenge both in achieving initial MSC differentiation and in maintaining tissue stability when the unified osteochondral tissue is subsequently cultured in a single medium formulation. In this proof-of-principle study, we used an in-house fabricated microwell platform to manufacture thousands of micropellets formed from 166 MSC each. We then characterized the development of bone-like and cartilage-like tissue formation in the micropellets maintained for 8–14 days in sequential combinations of osteogenic or chondrogenic induction medium. When bone-like or cartilage-like micropellets were induced for only 8 days, they displayed significant phenotypic changes when the osteogenic or chondrogenic induction medium, respectively, was swapped. Based on these data, we developed an extended 14-day protocol for the pre-culture of bone-like and cartilage-like micropellets in their respective induction medium. Unified osteochondral tissues were formed by layering 12,000 osteogenic micropellets and 12,000 chondrogenic micropellets into a biphasic structure and then further culture in chondrogenic induction medium. The assembled tissue was cultured for a further 8 days and characterized via histology. The micropellets had amalgamated into a continuous structure with distinctive bone-like and cartilage-like regions. This proof-of-concept study demonstrates the feasibility of micropellet assembly for the formation of osteochondral-like tissues for possible use in osteochondral defect repair.

The ultrastructural relationship between osteocytes and dental implants following osseointegration

Background Osteocytes, the most abundant cells in bone, havemultiple functions, including acting as mechanosensors and regulating mineralization. It is clear that osteocytes influence bone remodeling by controlling the differentiation and activity of osteoblasts and osteoclasts. Determining the relationship between titanium implants and osteocytes may therefore benefit our understanding of the process of osseointegration. Purpose The aim of this study was to visualize the ultrastructural relationship between osteocytes and the titanium implant surface following osseointegration in vivo. Materials and Methods Titanium implants were placed in the maxillary molar regions of eight female Sprague Dawley rats, 3 months old. The animals were sacrificed 8 weeks after implantation, and undecalcified tissue sections were prepared. Resin-cast samples were subsequently acid-etched with 37% phosphoric acid prior to examination using scanning electron microscopy. Results Compared with mature bone, where the osteocytes were arranged in an ordered fashion, the osteocytes appeared less organized in the newly formed bone around the titanium implant. Further, a layer of mineralization with few organic components was observed on the implant surface. This study shows for the first time that osteocytes and their dendrites are directly connected with the implant surface. Conclusions: This study shows the direct anchorage of osteocytes via dendritic processes to a titanium implant surface in vivo. This suggests an important regulatory role for osteocytes and their lacunar-canalicular network in maintaining long-term osseointegration.

Increased intra-cortical porosity reduces bone stiffness and strength in pediatric patients with osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a heritable disease occurring in one out of every 20,000 births. Although it is known that Type I collagen mutation in OI leads to increased bone fragility, the mechanism of this increased susceptibility to fracture is not clear. The aim of this study was to assess the microstructure of cortical bone fragments from patients with osteogenesis imperfecta (OI) using polarized light microscopy, and to correlate microstructural observations with the results of previously performed mechanical compression tests on bone from the same source. Specimens of cortical bone were harvested from the lower limbs of three (3) OI patients at the time of surgery, and were divided into two groups. Group 1 had been subjected to previous micro-mechanical compression testing, while Group 2 had not been subjected to any prior testing. Polarized light microscopy revealed disorganized bone collagen architecture as has been previously observed, as well as a large increase in the areal porosity of the bone compared to typical values for healthy cortical bone, with large (several hundred micron sized), asymmetrical pores. Importantly, the areal porosity of the OI bone samples in Group 1 appears to correlate strongly with their previously measured apparent Young's modulus and compressive strength. Taken together with prior nanoindentation studies on OI bone tissue, the results of this study suggest that increased intra-cortical porosity is responsible for the reduction in macroscopic mechanical properties of OI cortical bone, and therefore that in vivo imaging modalities with resolutions of ~ 100 μm or less could potentially be used to non-invasively assess bone strength in OI patients. Although the number of subjects in this study is small, these results highlight the importance of further studies in OI bone by groups with access to human OI tissue in order to clarify the relationship between increased porosity and reduced macroscopic mechanical integrity.

Oldest pathology in a tetrapod bone illuminates the origin of terrestrial vertebrates

The origin of terrestrial tetrapods was a key event in vertebrate evolution, yet how and when it occurred remains obscure, due to scarce fossil evidence. Here, we show that the study of palaeopathologies, such as broken and healed bones, can help elucidate poorly understood behavioural transitions such as this. Using high-resolution finite element analysis, we demonstrate that the oldest known broken tetrapod bone, a radius of the primitive stem tetrapod Ossinodus pueri from the mid-Viséan (333 million years ago) of Australia, fractured under a high-force, impact-type loading scenario. The nature of the fracture suggests that it most plausibly occurred during a fall on land. Augmenting this are new osteological observations, including a preferred directionality to the trabecular architecture of cancellous bone. Together, these results suggest that Ossinodus, one of the first large (>2m length) tetrapods, spent a significant proportion of its life on land. Our findings have important implications for understanding the temporal, biogeographical and physiological contexts under which terrestriality in vertebrates evolved. They push the date for the origin of terrestrial tetrapods further back into the Carboniferous by at least two million years. Moreover, they raise the possibility that terrestriality in vertebrates first evolved in large tetrapods in Gondwana rather than in small European forms, warranting a re-evaluation of this important evolutionary event.

Development of a method to assess the quality of ankle joint reduction in 3D

This project developed a quantitative method for determining the quality of the surgical alignment of the bone fragments after an ankle fracture. The research examined the feasibility of utilising MRI-based bone models versus the gold standard CT-based bone models in order to reduce the amount of ionising radiation the patient is exposed to. In doing so, the thesis reports that there is potential for MRI to be used instead of CT depending on the scanning parameters used to obtain the medical images, the distance of the implant relative to the joint surface, and the implant material.

Genome-wide association study using extreme truncate selection identifies novel genes affecting bone mineral density and fracture risk

Osteoporotic fracture is a major cause of morbidity and mortality worldwide. Low bone mineral density (BMD) is a major predisposing factor to fracture and is known to be highly heritable. Site-, gender-, and age-specific genetic effects on BMD are thought to be significant, but have largely not been considered in the design of genome-wide association studies (GWAS) of BMD to date. We report here a GWAS using a novel study design focusing on women of a specific age (postmenopausal women, age 55-85 years), with either extreme high or low hip BMD (age- and gender-adjusted BMD z-scores of +1.5 to +4.0, n = 1055, or -4.0 to -1.5, n = 900), with replication in cohorts of women drawn from the general population (n = 20,898). The study replicates 21 of 26 known BMD-associated genes. Additionally, we report suggestive association of a further six new genetic associations in or around the genes CLCN7, GALNT3, IBSP, LTBP3, RSPO3, and SOX4, with replication in two independent datasets. A novel mouse model with a loss-of-function mutation in GALNT3 is also reported, which has high bone mass, supporting the involvement of this gene in BMD determination. In addition to identifying further genes associated with BMD, this study confirms the efficiency of extreme-truncate selection designs for quantitative trait association studies. © 2011 Duncan et al.

WNT16 influences bone mineral density, cortical bone thickness, bone strength, and osteoporotic fracture risk

We aimed to identify genetic variants associated with cortical bone thickness (CBT) and bone mineral density (BMD) by performing two separate genome-wide association study (GWAS) meta-analyses for CBT in 3 cohorts comprising 5,878 European subjects and for BMD in 5 cohorts comprising 5,672 individuals. We then assessed selected single-nucleotide polymorphisms (SNPs) for osteoporotic fracture in 2,023 cases and 3,740 controls. Association with CBT and forearm BMD was tested for ~2.5 million SNPs in each cohort separately, and results were meta-analyzed using fixed effect meta-analysis. We identified a missense SNP (Thr>Ile; rs2707466) located in the WNT16 gene (7q31), associated with CBT (effect size of -0.11 standard deviations [SD] per C allele, P = 6.2×10-9). This SNP, as well as another nonsynonymous SNP rs2908004 (Gly>Arg), also had genome-wide significant association with forearm BMD (-0.14 SD per C allele, P = 2.3×10-12, and -0.16 SD per G allele, P = 1.2×10-15, respectively). Four genome-wide significant SNPs arising from BMD meta-analysis were tested for association with forearm fracture. SNP rs7776725 in FAM3C, a gene adjacent to WNT16, was associated with a genome-wide significant increased risk of forearm fracture (OR = 1.33, P = 7.3×10-9), with genome-wide suggestive signals from the two missense variants in WNT16 (rs2908004: OR = 1.22, P = 4.9×10-6 and rs2707466: OR = 1.22, P = 7.2×10-6). We next generated a homozygous mouse with targeted disruption of Wnt16. Female Wnt16-/- mice had 27% (P<0.001) thinner cortical bones at the femur midshaft, and bone strength measures were reduced between 43%-61% (6.5×10-13<P<5.9×10-4) at both femur and tibia, compared with their wild-type littermates. Natural variation in humans and targeted disruption in mice demonstrate that WNT16 is an important determinant of CBT, BMD, bone strength, and risk of fracture. © 2012 Zheng et al.