Decreases in bone mineral density at cortical and trabecular sites in the tibia and femur during the first year of spinal cord injury

Risk of fracture among patients with spinal cord injury: A nationwide cohort study in South Korea

BACKGROUND

Clinical concerns about preventing and managing fractures after spinal cord injury (SCI) have been growing.

OBJECTIVE

This study investigates the risk of fractures among SCI patients according to the presence of disability, disease severity, and level of injury.

METHODS

We performed a retrospective cohort study using the Korean National Health Insurance Service (KNHIS 2010-2018) database. We included 5190 SCI patients and 1:3 age- and sex-matched control participants. The primary outcome was fracture, and the cohort was followed until December 31, 2019.

RESULTS

SCI patients had a higher fracture risk than the matched controls (adjusted hazard ratio [aHR] 1.33, 95 % CI 1.16-1.54). The risk of fracture was higher in the presence of disability (aHR 1.57, 95 % CI 1.19-2.07), especially among patients with severe disability (aHR 1.65, 95 % CI 1.05-2.60). Higher fracture risks were observed among SCI patients regardless of injury level, but statistical significance was found only with cervical-level injury. When we considered site-specific fractures, vertebral (aHR 1.31, 95 % CI 1.04-1.64) and hip fracture risks (aHR 2.04, 95 % CI 1.39-2.98) were both higher among SCI patients than the controls. SCI patients with disability and cervical-level injury showed the highest hip fracture risk (aHR 3.67, 95 % CI 1.90-7.07).

CONCLUSIONS

Compared with the controls, SCI patients were at higher risk of any fracture, particularly hip fracture, especially those with disability and cervical-level injury. Clinicians should be aware of the fracture risk among SCI patients to provide proper management.

Peripheral nerve-derived Sema3A promotes osteogenic differentiation of mesenchymal stem cells through the Wnt/β-catenin/Nrp1 positive feedback loop

Sensory nerves play a crucial role in maintaining bone homeostasis by releasing Semaphorin 3A (Sema3A). However, the specific mechanism of Sema3A in regulation of bone marrow mesenchymal stem cells (BMMSCs) during bone remodelling remains unclear. The tibial denervation model was used and the denervated tibia exhibited significantly lower mass as compared to sham operated bones. In vitro, BMMSCs cocultured with dorsal root ganglion cells (DRGs) or stimulated by Sema3A could promote osteogenic differentiation through the Wnt/β-catenin/Nrp1 positive feedback loop, and the enhancement of osteogenic activity could be inhibited by SM345431 (Sema3A-specific inhibitor). In addition, Sema3A-stimulated BMMSCs or intravenous injection of Sema3A could promote new bone formation in vivo. To sum up, the coregulation of bone remodelling is due to the ageing of BMMSCs and increased osteoclast activity. Furthermore, the sensory neurotransmitter Sema3A promotes osteogenic differentiation of BMMSCs via Wnt/β-catenin/Nrp1 positive feedback loop, thus promoting osteogenesis in vivo and in vitro.

Alteration of Volumetric Bone Mineral Density Parameters in Men with Spinal Cord Injury

Spinal cord injury (SCI) induces severe losses of trabecular and cortical volumetric bone mineral density (vBMD), which cannot be discriminated with conventional dual-energy X-ray absorptiometry (DXA) analysis. The objectives were to: (i) determine the effects of SCI on areal BMD (aBMD) and vBMD determined by advanced 3D-DXA-based methods at various femoral regions and (ii) model the profiles of 3D-DXA-derived parameters with the time since injury. Eighty adult males with SCI and 25 age-matched able-bodied (AB) controls were enrolled in this study. Trabecular and cortical vBMD, cortical thickness and derived strength parameters were assessed by 3D-SHAPER® software at various femoral subregions. Individuals with SCI had significantly lower integral vBMD, trabecular vBMD, cortical vBMD, cortical thickness and derived bone strength parameters (p < 0.001 for all) in total proximal femur compared with AB controls. These alterations were approximately to the same degree for all three femoral subregions, and the difference between the two groups tended to be greater for cortical vBMD than trabecular vBMD. There were minor differences according to the lesion level (paraplegics vs tetraplegics) for all 3D-DXA-derived parameters. For total proximal femur, the decreasing bone parameters tended to reach a new steady state after 5.1 years for integral vBMD, 7.4 years for trabecular vBMD and 9.2 years for cortical vBMD following SCI. At proximal femur, lower vBMD (integral, cortical and trabecular) and cortical thickness resulted in low estimated bone strength in individuals with SCI. It remains to be demonstrated whether these new parameters are more closely associated with fragility fracture than aBMD.

Bone Mineral Loss at the Distal Femur and Proximal Tibia Following Spinal Cord Injury in Men and Women

PURPOSE

Spinal cord injury (SCI) causes rapid bone loss and increases risk of fragility fractures in the lower extremities. The majority of individuals with SCI are men, and few studies have investigated sex as a biological variable in SCI-induced osteoporosis. This cross-sectional study aimed to quantify sex-specific differences in bone mineral following SCI.

METHODS

Quantitative computed tomography (QCT) scans of the distal femur and proximal tibia were obtained at baseline of one of four clinical trials enrolling people who sustained SCI 1 month to 50 years prior to recruitment. Bone volume (BV), bone mineral content (BMC), bone mineral density (BMD), and bending strength index (BSI) were quantified in the integral, trabecular, and cortical bone in the epiphysis, metaphysis and diaphysis. Scans from 106 men and 31 women were analyzed to measure sex-specific effects on bone loss over time post-SCI.

RESULTS

BMC and BSI declined exponentially as a function of time post-SCI and were best described by separate decay curves for men and women. Women had BV, BMC, and BSI at 58-77% that of men in the acute and plateau phases, with both sexes showing similar rates of loss as a function of time post-SCI. Trabecular BMD was best described as an exponential decay versus time post-SCI, with no sex-specific differences.

CONCLUSIONS

Due to consistently lower BV, BMC, and BSI, women may be more susceptible to fractures after SCI than men.

Regional and temporal variation in bone loss during the first year following spinal cord injury

Osteoporosis is a consequence of spinal cord injury (SCI) that leads to fragility fractures. Visual assessment of bone scans suggests regional variation in bone loss, but this has not been objectively characterised. In addition, substantial inter-individual variation in bone loss following SCI has been reported but it is unclear how to identify fast bone losers. Therefore, to examine regional bone loss, tibial bone parameters were assessed in 13 individuals with SCI (aged 16-76 years). Peripheral quantitative computed tomography scans at 4 % and 66 % tibia length were acquired within 5 weeks, 4 months and 12 months postinjury. Changes in total bone mineral content (BMC), and bone mineral density (BMD) were assessed in ten concentric sectors at the 4 % site. Regional changes in BMC and cortical BMD were analysed in thirty-six polar sectors at the 66 % site using linear mixed effects models. Relationships between regional and total loss at 4 months and 12 months timepoints were assessed using Pearson correlation. At the 4 % site, total BMC (P = 0.001) decreased with time. Relative losses were equal across the sectors (all P > 0.1). At the 66 % site, BMC and cortical BMD absolute losses were similar (all P > 0.3 and P > 0.05, respectively) across polar sectors, but relative loss was greatest in the posterior region (all P < 0.01). At both sites, total BMC loss at 4 months was strongly positively associated with the total loss at 12 months (r = 0.84 and r = 0.82 respectively, both P < 0.001). This correlation was stronger than those observed with 4-month BMD loss in several radial and polar sectors (r = 0.56-0.77, P < 0.05). These results confirm that SCI-induced bone loss varies regionally in the tibial diaphysis. Moreover, bone loss at 4 months is a strong predictor of total loss 12 months postinjury. More studies on larger populations are required to confirm these findings.

Bone resorption after maxillary reconstruction with the vascularized free iliac flap

The aim of this study was to evaluate the resorption of the iliac bone after maxillary reconstruction with a vascularized free iliac flap. Twenty-seven patients with maxillary defects who underwent maxillary reconstruction with the vascularized free iliac flap between January 2017 and January 2021 were included. Computed tomography (CT) images taken at 1 week, approximately 6 months, and 1 year after the surgery were used for evaluation. The total iliac bone thickness and height, cortical bone thickness, and cancellous bone density were measured in the CT images. Compared with 1 week after the surgery, the total thickness and height of the iliac bone were reduced significantly 1 year after the surgery, and the cortical bone thickness and cancellous bone density were reduced significantly at 6 months and 1 year after the surgery. Compared with 6 months after the surgery, cancellous bone density was reduced significantly 1 year after the surgery. In conclusion, during the first year after maxillary reconstruction with a vascularized free iliac flap, there was significant resorption of iliac bone, including the total iliac bone thickness and height, the cortical bone thickness, and the cancellous bone density.

Frontiers of Hydroxyapatite Composites in Bionic Bone Tissue Engineering

Bone defects caused by various factors may cause morphological and functional disorders that can seriously affect patient's quality of life. Autologous bone grafting is morbid, involves numerous complications, and provides limited volume at donor site. Hence, tissue-engineered bone is a better alternative for repair of bone defects and for promoting a patient's functional recovery. Besides good biocompatibility, scaffolding materials represented by hydroxyapatite (HA) composites in tissue-engineered bone also have strong ability to guide bone regeneration. The development of manufacturing technology and advances in material science have made HA composite scaffolding more closely related to the composition and mechanical properties of natural bone. The surface morphology and pore diameter of the scaffold material are more important for cell proliferation, differentiation, and nutrient exchange. The degradation rate of the composite scaffold should match the rate of osteogenesis, and the loading of cells/cytokine is beneficial to promote the formation of new bone. In conclusion, there is no doubt that a breakthrough has been made in composition, mechanical properties, and degradation of HA composites. Biomimetic tissue-engineered bone based on vascularization and innervation show a promising future.

Disuse Osteoporosis: Clinical and Mechanistic Insights

Disuse osteoporosis describes a state of bone loss due to local skeletal unloading or systemic immobilization. This review will discuss advances in the field that have shed light on clinical observations, mechanistic insights and options for the treatment of disuse osteoporosis. Clinical settings of disuse osteoporosis include spinal cord injury, other neurological and neuromuscular disorders, immobilization after fractures and bed rest (real or modeled). Furthermore, spaceflight-induced bone loss represents a well-known adaptive process to microgravity. Clinical studies have outlined that immobilization leads to immediate bone loss in both the trabecular and cortical compartments accompanied by relatively increased bone resorption and decreased bone formation. The fact that the low bone formation state has been linked to high levels of the osteocyte-secreted protein sclerostin is one of the many findings that has brought matrix-embedded, mechanosensitive osteocytes into focus in the search for mechanistic principles. Previous basic research has primarily involved rodent models based on tail suspension, spaceflight and other immobilization methods, which have underlined the importance of osteocytes in the pathogenesis of disuse osteoporosis. Furthermore, molecular-based in vitro and in vivo approaches have revealed that osteocytes sense mechanical loading through mechanosensors that translate extracellular mechanical signals to intracellular biochemical signals and regulate gene expression. Osteocytic mechanosensors include the osteocyte cytoskeleton and dendritic processes within the lacuno-canalicular system (LCS), ion channels (e.g., Piezo1), extracellular matrix, primary cilia, focal adhesions (integrin-based) and hemichannels and gap junctions (connexin-based). Overall, disuse represents one of the major factors contributing to immediate bone loss and osteoporosis, and alterations in osteocytic pathways appear crucial to the bone loss associated with unloading.

Spatiotemporal responses of trabecular and cortical bone to complete spinal cord injury in skeletally mature rats

Objective

Methods

Results

Conclusions

•

Skeletally mature spinal cord transected rats display biphasic bone loss

•

The osteoporosis manifests over slower time scales than in skeletally immature rats.

•

Relevancy for testing efficacy of interventions against SCI-induced osteoporosis.

Fibula response to disuse: a longitudinal analysis in people with spinal cord injury

Fibular response to disuse has been described in cross-sectional but not longitudinal studies. This study assessed fibular bone changes in people with spinal cord injury. Fibular bone loss was less than in the tibia and was not correlated together. This might explain low fibular fracture incidents in these patients.

PURPOSE

Cross-sectional studies suggest that the fibula responds differently to loading and disuse compared to the tibia. Whilst tibial bone changes following spinal cord injury (SCI) have been established in longitudinal studies, fibular changes remain unexplored.

METHODS

Fibular and tibial bone parameters were assessed in 13 individuals with SCI (aged 16-76 years). Peripheral quantitative computed tomography scans were acquired at 4%, 38% and 66% distal-proximal tibia length at 5 weeks and 12 months post-injury. Changes in 4% site total bone mineral content (BMC), total cross-sectional area (CSA) and bone mineral density (BMD), and 38% and 66% sites total BMC, total CSA, cortical BMD and cortical CSA were assessed using paired T-tests. Relationships between bone loss in the two bones at equivalent sites were assessed using paired T-tests and correlation.

RESULTS

At the 4% site, fibular total BMC and BMD losses were less than tibial losses (- 6.9 ± 5.1% and - 6.6 ± 6.0% vs - 14.8 ± 12.4% and - 14.4 ± 12.4%, p = 0.02 and p = 0.03, respectively). Similarly, at the 66% site, fibular BMC losses were less than those in the tibia (- 2.0 ± 2.6% vs - 4.3 ± 3.6%, p = 0.03), but there was no difference at 38% (- 1.8 ± 3.5% vs - 3.8 ± 2.1%, p = 0.1). No correlation was observed for BMC changes between the two bones (all p > 0.25).

CONCLUSION

These results support cross-sectional evidence of smaller disuse-related bone loss in the fibula compared to the tibia. These results may in part explain lower incidence of fibula fractures in individuals with chronic SCI. The lack of association between losses in the two bones might point to different underlying mechanisms.

Osteopenia in a Mouse Model of Spinal Cord Injury: Effects of Age, Sex and Motor Function

Simple Summary

In the first two years following spinal cord injury, people lose up to 50% of bone below the injury. This injury-induced bone loss significantly affects rehabilitation and leaves people vulnerable to fractures and post-fracture complications, including lung and urinary tract infections, blood clots in the veins, and depression. Unfortunately, little is known about the factors driving this bone loss. In fact, even though we know that injury, age, and sex independently increase bone loss, there have been no studies looking at the cumulative effects of these variables. People with spinal injury are aging, and the age at which injuries occur is increasing. It is essential to know whether these factors together will further compromise bone. To examine this, we assessed bone loss in young and old, male and female mice after spinal injury. As expected, we found that aging alone decreased motor activity and bone volume. Spinal injury also reduced bone volume, but it did not worsen the effects of age. Instead, injury effects appeared related to reduced rearing activity. The data suggest that although partial weight-bearing does not reduce bone loss after spinal cord injury, therapies that put full weight on the legs may be clinically effective.

Abstract

After spinal cord injury (SCI), 80% of individuals are diagnosed with osteopenia or osteoporosis. The dramatic loss of bone after SCI increases the potential for fractures 100-fold, with post-fracture complications occurring in 54% of cases. With the age of new SCI injuries increasing, we hypothesized that a SCI-induced reduction in weight bearing could further exacerbate age-induced bone loss. To test this, young (2–3 months) and old (20–30 months) male and female mice were given a moderate spinal contusion injury (T9–T10), and recovery was assessed for 28 days (BMS, rearing counts, distance traveled). Tibial trabecular bone volume was measured after 28 days with ex vivo microCT. While BMS scores did not differ across groups, older subjects travelled less in the open field and there was a decrease in rearing with age and SCI. As expected, aging decreased trabecular bone volume and cortical thickness in both old male and female mice. SCI alone also reduced trabecular bone volume in young mice, but did not have an additional effect beyond the age-dependent decrease in trabecular and cortical bone volume seen in both sexes. Interestingly, both rearing and total activity correlated with decreased bone volume. These data underscore the importance of load and use on bone mass. While partial weight-bearing does not stabilize/reverse bone loss in humans, our data suggest that therapies that simulate complete loading may be effective after SCI.

Bone Mineral Density at the Distal Femur and Proximal Tibia and Related Factors During the First Year of Spinal Cord Injury

Background

Spinal cord injury (SCI) can lead to disuse osteoporosis. The most vulnerable sites for fragility-induced fractures are the distal femur (DF) and proximal tibia (PT). The aim of this study was to evaluate changes in bone mineral density (BMD) at the DF and PT, as well as related factors, during the first year of SCI.

Patients and Methods

Thirty-six SCI patients within 12 months of their injury were selected, as were 36 healthy controls. The dual-energy X-ray absorptiometry was used to measure BMDs at the DF, PT, and hip of all subjects. According to the duration of SCI when receiving DXA scan, 36 SCI patients were divided into three subgroups. The BMDs of overall patients and subgroups were compared to those of controls. Biochemical markers of bone metabolism were detected in SCI patients.

Results

The BMDs at the DF, PT, and hips of overall SCI patients were significantly lower than those of controls. The percentage difference of BMD between SCI patients and controls at the DF and PT was higher than at the hip. The BMD at the PT of SCI within 6 weeks post-injury was lower than that of controls. The BMDs at the DF and PT of SCI during 6 weeks-3 months post-injury were lower than those of controls. Whereas there was no difference in the BMD at the hip during the first 3 months of SCI. Age and 25OHD were the influencing factors of DF BMD. Age and gender were found to influence PT BMD.

Conclusion

The rapid loss of BMD at the PT and DF during the first year of SCI occurred significantly earlier than that of the hip. It is recommended to monitor the BMD of DF and PT in early-stage SCI patients, combined with detection of biochemical markers of bone metabolism.

Abaloparatide treatment increases bone formation, bone density and bone strength without increasing bone resorption in a rat model of hindlimb unloading

Disuse osteoporosis can result from prolonged bed rest, paralysis, casts, braces, fractures and other conditions. Abaloparatide (ABL) is a PTHrP analog that increases bone density and strength by stimulating osteogenesis with limited effects on bone resorption. We examined skeletal responses to abaloparatide in young adult male rats with normal weight-bearing and with hindlimb unloading via a pelvic harness. Rats were allocated to four groups (10-12 per group): normal weight-bearing plus vehicle treatment (CON-VEH), normal weight-bearing plus ABL treatment (CON-ABL), hindlimb-unloading plus vehicle (HLU-VEH), or hindlimb-unloading plus ABL (HLU-ABL). Rats received ABL (25 μg/kg/day, s.c.) or vehicle throughout the 28-day unloading period and were then sacrificed, at which time HLU-VEH rats exhibited reduced bone formation and significant deficits in tibial, femoral, and vertebral bone mass compared with CON-VEH. ABL treatment increased serum osteocalcin in CON and HLU animals while having no effect on the osteoclast marker TRACP-5b. Longitudinal peripheral quantitative computed tomography (pQCT) indicated that ABL increased trabecular and cortical bone mass in the tibia. ABL was also associated with improved trabecular and cortical bone mass and architectural parameters at the femur, tibia, and vertebrae by μCT. Tibial histomorphometry indicated increased trabecular and endocortical bone formation with HLU-ABL versus HLU-VEH and with CON-ABL versus CON-VEH, and ABL was also associated with lower trabecular and endocortical osteoclast surfaces. Vertebral finite element analysis indicated higher ultimate load and stiffness for CON-ABL versus CON-VEH and for HLU-ABL versus HLU-VEH. In summary, ABL was associated with improved trabecular and cortical bone density and architecture in normal weight-bearing and hindlimb-unloaded rats, with higher bone formation and no difference in bone resorption. ABL was also associated with improved bone biomechanical parameters. These results provide rationale for investigating the ability of abaloparatide to prevent or treat disuse osteoporosis in humans.

Administration of Denosumab Preserves Bone Mineral Density at the Knee in Persons With Subacute Spinal Cord Injury: Findings From a Randomized Clinical Trial

Persons with neurologically motor-complete spinal cord injury (SCI) have a marked loss of bone mineral density (BMD) of the long bones of the lower extremities, predisposing them to fragility fractures, especially at the knee. Denosumab, a commercially available human monoclonal IgG antibody to receptor activator of nuclear factor-κB ligand (RANKL), may provide an immunopharmacological solution to the rapid progressive deterioration of sublesional bone after SCI. Twenty-six SCI participants with subacute motor-complete SCI were randomized to receive either denosumab (60 mg) or placebo at baseline (BL), 6, and 12 months. Areal bone mineral density (aBMD) by dual energy x-ray absorptiometry (DXA) at 18 months at the distal femur was the primary outcome and aBMD of the proximal tibia and hip were the secondary outcomes analyzed in 18 of the 26 participants (denosumab, n = 10 and placebo, n = 8). The metrics of peripheral QCT (pQCT) were the exploratory outcomes analyzed in a subsample of the cohort (denosumab, n = 7 and placebo n = 7). The mean aBMD (±95% CI) for the denosumab versus the placebo groups demonstrated a significant group × time interactions for the following regions of interest at BL and 18 months: distal femoral metaphysis = mean aBMD 1.187; 95% CI, 1.074 to 1.300 and mean aBMD 1.202; 95% CI, 1.074 to 1.329 versus mean aBMD 1.162; 95% CI, 0.962 to 1.362 and mean aBMD 0.961; 95% CI, 0.763 to 1.159, respectively (p < 0.001); distal femoral epiphysis = mean aBMD 1.557; 95% CI, 1.437 to 1.675 and mean aBMD 1.570; 95% CI, 1.440 to 1.700 versus mean aBMD 1.565; 95% CI, 1.434 to 1.696 and mean aBMD 1.103; 95% CI, 0.898 to 1.309, respectively (p = 0.002); and proximal tibial epiphysis = mean aBMD 1.071; 95% CI, 0.957 to 1.186 and mean aBMD 1.050; 95% CI, 0.932 to 1.168 versus mean aBMD 0.994; 95% CI, 0.879 to 1.109 and mean aBMD 0.760; 95% CI, 0.601 to 0.919, respectively (p < 0.001). Analysis of pQCT imaging revealed a continued trend toward significantly greater loss in total volumetric BMD (vBMD) and trabecular vBMD at the 4% distal tibia region, with a significant percent loss for total bone mineral content. Thus, at 18 months after acute SCI, our findings show that denosumab maintained aBMD at the knee region, the site of greatest clinical relevance in the SCI population. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

The neural system regulates bone homeostasis via mesenchymal stem cells: a translational approach

Large bone reconstruction is a major clinical issue associated with several challenges, and autograft is the main method for reconstructing large defects of maxillofacial bone. However, postoperative osteoporosis of the bone graft, even with sufficient vascularization, remains a primary problem. Therefore, better understanding of the mechanisms and clinical translation of bone homeostasis is required. Neuronal innervation of the bone is an emerging research topic, especially with regards to the role of peripheral nerves in regulating bone homeostasis. Moreover, sensory and autonomic nerves regulate this process via different types of neurotransmitters, but the specific mechanism is still elusive. In this review article, the current understanding of the interaction between the peripheral nerve and the skeleton system is summarized, with a particular focus on bone marrow mesenchymal stem cells (BMMSCs), except for osteoblasts and osteoclasts. The novel application of nerve-based bone regeneration via BMMSCs may provide a new strategy in tissue engineering and clinical treatment of osteoporosis and bone disorders.

Evaluating Bone Loss with Bone Turnover Markers Following Acute Spinal Cord Injury

STUDY DESIGN

Prospective observational study.

PURPOSE

To evaluate bone turnover markers (BTMs) in individuals with acute spinal cord injury (SCI) and to compare the results with those of healthy controls and postmenopausal females.

OVERVIEW OF LITERATURE

SCI significantly impacts bone health. Change in bone mineral density appears 6 months after SCI and rapid bone loss during the acute phase is often underestimated, resulting in osteoporosis and a high risk of sublesional fractures. However, few studies have evaluated BTMs in the Indian SCI population. Despite a high risk of fracture, there are no guidelines for the diagnosis, monitoring, and management of SCI-induced osteoporosis.

METHODS

Twenty patients within 1 month of traumatic SCI who had been admitted to a tertiary care rehabilitation center were included in this study. Serum BTMs, C telopeptide (CTX) as a bone resorption marker, and osteocalcin as a bone formation marker, were serially measured at baseline, and 3 and 6 months after SCI. BTMs of SCI patients were compared with those of a control group of age-matched healthy males, premenopausal females, and a vulnerable group of postmenopausal females.

RESULTS

BTMs were significantly elevated in patients with SCI, with maximum levels observed at the 3rd month of injury. At baseline, the bone resorption marker CTX was approximately 3 times higher in SCI patients than in the control male population and premenopausal females, and about double that of postmenopausal females. The rise in the bone formation marker was marginal in comparison to that of the bone resorption marker. BTMs were persistently elevated and did not reach the normative range until the 6th month of SCI.

CONCLUSIONS

Raised bone resorption markers in comparison to bone formation markers indicate hyper-resorption-related bone loss following acute SCI. Markedly elevated bone resorption markers in the SCI population, compared with those in control and vulnerable groups, emphasize the need for early bone health monitoring and management.

Low Energy Availability, Menstrual Dysfunction, and Low Bone Mineral Density in Individuals with a Disability: Implications for the Para Athlete Population

Low energy availability, functional hypothalamic amenorrhea, and low bone mineral density are three interrelated conditions described in athletic women. Although described as the female athlete triad (Triad), males experience similar health concerns. The literature suggests that individuals with a disability may experience altered physiology related to these three conditions when compared with the able-bodied population. The goal of this review is to describe the unique implications of low energy availability, low bone mineral density, and, in females, menstrual dysfunction in individuals with a disability and their potential impact on the para athlete population. A literature review was performed linking search terms related to the three conditions with six disability categories that are most represented in para sport. Few articles were found that directly pertained to athletes, therefore, the review additionally characterizes literature found in a non-athlete population. Review of the available literature in athletes suggests that both male and female athletes with spinal cord injury demonstrate risk factors for low energy availability. Bone mineral density may also show improvements for wheelchair athletes or athletes with hemiplegic cerebral palsy when compared with a disabled non-athlete population. However, the prevalence of the three conditions and implications on the health of para athletes is largely unknown and represents a key gap in the sports medicine literature. As participation in para sport continues to increase, further research is needed to understand the impact of these three interrelated health concerns for athletes with a disability, accompanied by educational initiatives targeting athletes, coaches, and health professionals.

Peripheral Quantitative Computed Tomography: Review of Evidence and Recommendations for Image Acquisition, Analysis, and Reporting, Among Individuals With Neurological Impairment

In 2015, the International Society for Clinical Densitometry (ISCD) position statement regarding peripheral quantitative computed tomography (pQCT) did not recommend routine use of pQCT, in clinical settings until consistency in image acquisition and analysis protocols are reached, normative studies conducted, and treatment thresholds identified. To date, the lack of consensus-derived recommendations regarding pQCT implementation remains a barrier to implementation of pQCT technology. Thus, based on description of available evidence and literature synthesis, this review recommends the most appropriate pQCT acquisition and analysis protocols for clinical care and research purposes, and recommends specific measures for diagnosis of osteoporosis, assigning fracture risk, and monitoring osteoporosis treatment effectiveness, among patients with neurological impairment. A systematic literature search of MEDLINE, EMBASE^©, CINAHL, and PubMed for available pQCT studies assessing bone health was carried out from inception to August 8th, 2017. The search was limited to individuals with neurological impairment (spinal cord injury, stroke, and multiple sclerosis) as these groups have rapid and severe regional declines in bone mass. Of 923 references, we identified 69 that met review inclusion criteria. The majority of studies (n = 60) used the Stratec XCT 2000/3000 pQCT scanners as reflected in our evaluation of acquisition and analysis protocols. Overall congruence with the ISCD Official Positions was poor. Only 11% (n = 6) studies met quality reporting criteria for image acquisition and 32% (n = 19) reported their data analysis in a format suitable for reproduction. Therefore, based on current literature synthesis, ISCD position statement standards and the authors' expertise, we propose acquisition and analysis protocols at the radius, tibia, and femur sites using Stratec XCT 2000/3000 pQCT scanners among patients with neurological impairment for clinical and research purposes in order to drive practice change, develop normative datasets and complete future meta-analysis to inform fracture risk and treatment efficacy evaluation.

Analysis of the evolution of cortical and trabecular bone compartments in the proximal femur after spinal cord injury by 3D-DXA

Marked trabecular and cortical bone loss was observed at the proximal femur short-term after spinal cord injury (SCI). 3D-DXA provided measurement of vBMD evolution at both femoral compartments and cortical thinning, thereby suggesting that this technique could be useful for bone analysis in these patients.

INTRODUCTION

SCI is associated with a marked increase in bone loss and risk of osteoporosis development short-term after injury. 3D-DXA is a new imaging analysis technique providing 3D analysis of the cortical and trabecular bone from DXA scans. The aim of this study was to assess the evolution of trabecular macrostructure and cortical bone using 3D-DXA in patients with recent SCI followed over 12 months.

METHODS

Sixteen males with recent SCI (< 3 months since injury) and without antiosteoporotic treatment were included. Clinical assessment, bone mineral density (BMD) measurements by DXA, and 3D-DXA evaluation at proximal femur (analyzing the integral, trabecular and cortical volumetric BMD [vBMD] and cortical thickness) were performed at baseline and at 6 and 12 months of follow-up.

RESULTS

vBMD significantly decreased at integral, trabecular, and cortical compartments at 6 months (- 8.8, - 11.6, and - 2.4%), with a further decrease at 12 months, resulting in an overall decrease of - 16.6, - 21.9, and - 5.0%, respectively. Cortical thickness also decreased at 6 and 12 months (- 8.0 and - 11.4%), with the maximal decrease being observed during the first 6 months. The mean BMD losses by DXA at femoral neck and total femur were - 17.7 and - 21.1%, at 12 months, respectively.

CONCLUSIONS

Marked trabecular and cortical bone loss was observed at the proximal femur short-term after SCI. 3D-DXA measured vBMD evolution at both femoral compartments and cortical thinning, providing better knowledge of their differential contributory role to bone strength and probably of the effect of therapy in these patients.

FES Bike Race preparation to Cybathlon 2016 by EMA team: a short case report

FES-assisted cycling has been recommended to people struggling to emerge from a disability to more functioning life after spinal cord injury. Recommendations issued by a gowing number of scientific papershas promised toimprove body composition and physical activity levels, as well as to controlinvoluntary muscle response; favoring activity and participation which break new grounds in expanding locomotion, leisure and occupational options for people with paraplegia and tetraplegia. In this report we described our experience to select and prepare a pilot to compete in the FES Bike Race modality at Cybathlon 2016 in Kloten (Zurick). He was a man, 38 years old, with a complete spinal cord injury, level T9, three years of injury. He took part in a two preparation phases lasting respectively 18 and 12 weeks each: (1st) pre-FES-cycling and a (2nd) FES-cycling. The 1st phase aimed to explore electrical stimulation response in the quadricps, hamstrings and gluteus muscles; searching for a standard muscular recruitment enable to propel the pedals of a trike. Following, in the 2nd phase, stationary to mobile FES-cycling was performed at the same time the development of the automation and control systems were being incorporated in the trike. We adapted a commercial tadpole trycicle anda pilot controlled system. Although we had planned a three session by week protocol, for reasons of term and time to finish the trike development and be prepared to compete, in the last two weeks before the Cybatlhon an intense level of exercise was maintained. After the race, we noticedinflammatory signs on the left knee which later revealed a patella fracture. The video footage analysis confirmed ithappened during the race's first lap.

Acute bone changes after lower limb amputation resulting from traumatic injury

Bone health is critical for lower limb amputees, affecting their ability to use a prosthesis and their risk of osteoporosis. We found large losses in hip bone mineral density (BMD) and in amputated bone strength in the first year of prosthesis use, suggesting a need for load bearing interventions early post-amputation.

INTRODUCTION

Large deficits in hip areal BMD (aBMD) and residual limb volumetric BMD (vBMD) occur after lower limb amputation; however, the time course of these bone quality changes is unknown. The purpose of this study was to quantify changes in the amputated bone that occur during the early stages post-amputation.

METHODS

Eight traumatic unilateral amputees (23-53 years) were enrolled prior to surgery. Changes in total body, hip, and spine aBMD (dual-energy X-ray absorptiometry); in vBMD, stress-strain index (SSI), and muscle cross-sectional area (MCSA) (peripheral QCT); and in bone turnover markers were assessed after amputation prior to prosthesis fitting (pre-ambulatory) and at 6 and 12 months walking with prosthesis.

RESULTS

Hip aBMD of the amputated limb decreased 11-15%, which persisted through 12 months. The amputated bone had decreases (p < 0.01) in BMC (-26%), vBMD (-21%), and SSI (-25%) from pre-ambulatory to 6 months on a prosthesis, which was maintained between 6 and 12 months. There was a decrease (p < 0.05) in the proportion of bone >650 mg/cm³ (58 to 43% of total area) or >480 mg/cm³ (65% to 53%), suggesting an increase in cortical porosity after amputation. Bone alkaline phosphatase and sclerostin were elevated (p < 0.05) at pre-ambulatory and then decreased towards baseline. Bone resorption markers were highest at surgery and pre-ambulatory and then progressively decreased (p < 0.05).

CONCLUSIONS

Rapid and substantial losses in bone content and strength occur early after amputation and are not regained by 12 months of becoming ambulatory. Early post-amputation may be the most critical window for preventing bone loss.

Patient-specific bone mineral density distribution in the tibia of individuals with chronic spinal cord injury, derived from multi-slice peripheral Quantitative Computed Tomography (pQCT) - A cross-sectional study

BACKGROUND

The high risk of fracture associated with chronic spinal cord injury (SCI) is attributed to extensive disuse-related bone loss in previously weight-bearing long bones. Changes in bone mineral density (BMD) after SCI have been documented extensively for the epiphyses of the tibia and femur, fracture-prone sites in this patient group. Less attention has been given to patterns of cortical bone loss in the diaphyses, but variability in BMD distributions throughout the long bones may contribute to some patients' increased susceptibility to shaft fractures in chronic SCI.

AIM

A cross-sectional study was carried out to determine whether BMD distributions along the tibia differ between individuals with chronic SCI and healthy able-bodied (AB) controls, in both the trabecular and cortical bone compartments. The effects of time post-injury and gender on BMD distribution were also explored.

METHODS

Individuals with chronic (≥6months post-injury) motor-complete SCI were recruited from the Queen Elizabeth National Spinal Injuries Unit (Glasgow, UK). AB control subjects were recruited to achieve similar age and gender profiles for the SCI and control groups. Multi-slice pQCT (XCT3000, Stratec) was performed along the length of the tibia (2mm thickness, 0.5mm voxel size), at 1% intervals in the epiphyses and 5% intervals in the diaphysis (34 slices in total). These were used to reconstruct full 3-D subject-specific models (Mimics, Materialise) of BMD distribution, by interpolating between slices. Subjects with chronic SCI were subdivided into 'early' (<4years post-injury) and 'established' SCI (≥4years post-injury). Subject-specific BMD distribution was described according to new parameters determined from the 3-D patient-specific models, quantifying descriptors of the trabecular and cortical BMD regions separately (volume, peak BMD, half-peak width, area under the curve). These were compared between sub-groups (using independent-samples t-tests or Mann-Whitney tests, significance level of 5%).

RESULTS

11 men (age range 17-59years old; mean 35.7±10.6) and 3 post-menopausal women (age range 56-58years old; mean 56.7±1.2years) with motor-complete SCI (ranging from 6months to 27years post-injury) were recruited; 6 men (age range 20-56years old; 33.0±12.7years) and 1 post-menopausal woman (56years) formed the AB control group. Overall, SCI resulted in lower BMD at both trabecular and cortical regions of the tibia. In men, longer time since injury resulted in greater BMD differences when compared to AB, throughout the tibia. For the post-menopausal women, differences in BMD between SCI and AB were greater in cortical bone than in trabecular bone. From the models, individual BMD distribution curves showed healthy double-peaks in AB subjects: one trabecular peak (around 200-300mg/cm³) and the other cortical (around 1000-1100mg/cm³). In most subjects with established SCI, trabecular peaks were exaggerated whilst the cortical peaks were barely discernible, with crucially some individuals already exhibiting a diminishing cortical BMD peak even <4years post-injury.

CONCLUSIONS

These findings may have implications for determining the fracture susceptibility of the long bones in individual patients with SCI. Epiphyseal fractures associated with low trabecular BMD are well characterised, but our data show that some individuals with SCI may also be at higher risk of shaft fractures. The proposed BMD distribution description parameters, determined from patient-specific models, could be used to identify patients with a weakened diaphysis who may be susceptible to fractures of the tibial shaft, but this requires validation.

Bone loss at the distal femur and proximal tibia in persons with spinal cord injury: imaging approaches, risk of fracture, and potential treatment options

Persons with spinal cord injury (SCI) undergo immediate unloading of the skeleton and, as a result, have severe bone loss below the level of lesion associated with increased risk of long-bone fractures. The pattern of bone loss in individuals with SCI differs from other forms of secondary osteoporosis because the skeleton above the level of lesion remains unaffected, while marked bone loss occurs in the regions of neurological impairment. Striking demineralization of the trabecular epiphyses of the distal femur (supracondylar) and proximal tibia occurs, with the knee region being highly vulnerable to fracture because many accidents occur while sitting in a wheelchair, making the knee region the first point of contact to any applied force. To quantify bone mineral density (BMD) at the knee, dual energy x-ray absorptiometry (DXA) and/or computed tomography (CT) bone densitometry are routinely employed in the clinical and research settings. A detailed review of imaging methods to acquire and quantify BMD at the distal femur and proximal tibia has not been performed to date but, if available, would serve as a reference for clinicians and researchers. This article will discuss the risk of fracture at the knee in persons with SCI, imaging methods to acquire and quantify BMD at the distal femur and proximal tibia, and treatment options available for prophylaxis against or reversal of osteoporosis in individuals with SCI.

Meagre effects of disuse on the human fibula are not explained by bone size or geometry

Fibula response to disuse is unknown; we assessed fibula bone in spinal cord injury (SCI) patients and able-bodied counterparts. Group differences were smaller than in the neighbouring tibia which could not be explained by bone geometry. Differential adaptation of the shank bones may indicate previously unknown mechanoadaptive behaviours of bone.

INTRODUCTION

The fibula supports only a small and highly variable proportion of shank compressive load (-8 to +19 %), and little is known about other kinds of stresses. Hence, whilst effects of habitual loading on tibia are well-known, fibula response to disuse is difficult to predict.

METHODS

Therefore, we assessed fibular bone strength using peripheral quantitative computed tomography (pQCT) at 5 % increments from 5 to 90 % distal-proximal tibia length in nine participants with long-term spinal cord injury (SCI; age 39.2 ± 6.2 years, time since injury 17.8 ± 7.4 years), representing a cross-sectional model of long-term disuse and in nine able-bodied counterparts of similar age (39.6 ± 7.8 years), height and mass.

RESULTS

There was no group difference in diaphyseal fibula total bone mineral content (BMC) (P = 0.22, 95 % CIs -7.4 % to -13.4 % and +10.9 % to +19.2 %). Site by group interactions (P < 0.001) revealed 27 and 22 % lower BMC in SCI at 5 and 90 % (epiphyseal) sites only. Cortical bone geometry differed at mid and distal diaphysis, with lower endocortical circumference and greater cortical thickness in SCI than able-bodied participants in this region only (interactions both P < 0.01). Tibia bone strength was also assessed; bone by group interactions showed smaller group differences in fibula than tibia for all bone parameters, with opposing effects on distal diaphysis geometry in the two bones (all Ps < 0.001).

CONCLUSIONS

These results suggest that the structure of the fibula diaphysis is not heavily influenced by compressive loading, and only mid and distal diaphysis are influenced by bending and/or torsional loads. The fibula is less influenced by disuse than the tibia, which cannot satisfactorily be explained by differences in bone geometry or relative changes in habitual loading in disuse. Biomechanical study of the shank loading environment may give new information pertaining to factors influencing bone mechanoadaptation.

Bone mineral decreases in the calcanei in men after arthroscopic shoulder surgery: a prospective study over 5 years

PURPOSE

It is well known that injuries and surgical procedures in the lower extremities affect bone mineral both in the injured limb and in the contralateral limb. The possible effect on bone mineral after upper extremity surgery is not well studied, and the aim of this study was to study the effect on bone mineral in the calcanei after arthroscopic shoulder surgery.

METHODS

Twenty-two men scheduled for arthroscopic shoulder surgery underwent bone mineral area (BMA) mass measurements in both calcanei using the Calscan DXL device prior to surgery and after 6, 18, 36 and 60 months. On every occasion, the Tegner activity score and EuroQoL 5-dimensions (EQ-5D) were assessed.

RESULTS

During 5 years, there was a significant decrease in the BMA in both calcanei (p = 0.003). The Tegner activity score decreased from preinjury to the operation and did not increase significantly after the operation. The EQ-5D increased significantly after the operation.

CONCLUSION

The bone mineral in the calcanei in men during the 5-year study period decreased more than the expected age-dependent decline after arthroscopic shoulder surgery. There was an increase in health-related quality of life as measured with the EQ-5D after arthroscopic Bankart reconstruction.

LEVEL OF EVIDENCE

Case-control study, Level III.

Multiple organ dysfunction and systemic inflammation after spinal cord injury: a complex relationship

Spinal cord injury (SCI) is a devastating event that results in significant physical disabilities for affected individuals. Apart from local injury within the spinal cord, SCI patients develop a variety of complications characterized by multiple organ dysfunction or failure. These disorders, such as neurogenic pain, depression, lung injury, cardiovascular disease, liver damage, kidney dysfunction, urinary tract infection, and increased susceptibility to pathogen infection, are common in injured patients, hinder functional recovery, and can even be life threatening. Multiple lines of evidence point to pathological connections emanating from the injured spinal cord, post-injury systemic inflammation, and immune suppression as important multifactorial mechanisms underlying post-SCI complications. SCI triggers systemic inflammatory responses marked by increased circulation of immune cells and pro-inflammatory mediators, which result in the infiltration of inflammatory cells into secondary organs and persistence of an inflammatory microenvironment that contributes to organ dysfunction. SCI also induces immune deficiency through immune organ dysfunction, resulting in impaired responsiveness to pathogen infection. In this review, we summarize current evidence demonstrating the relevance of inflammatory conditions and immune suppression in several complications frequently seen following SCI. In addition, we highlight the potential pathways by which inflammatory and immune cues contribute to multiple organ failure and dysfunction and discuss current anti-inflammatory approaches used to alleviate post-SCI complications. A comprehensive review of this literature may provide new insights into therapeutic strategies against complications after SCI by targeting systemic inflammation.

Measuring muscle and bone in individuals with neurologic impairment; lessons learned about participant selection and pQCT scan acquisition and analysis

Peripheral quantitative computed tomography (pQCT) can be used to examine bone strength outcomes and muscle size and fatty infiltration. Our research team and others have used it to examine bone loss after spinal cord injury (SCI). However, the high prevalence of restricted lower extremity range of motion, spasticity, edema, excessive muscle atrophy, or severe osteoporosis necessitates changes to standard protocols for screening, positioning during scan acquisition, and analysis methods. This manuscript outlines the challenges that we experienced using pQCT in individuals with SCI, and provides solutions, ones that may also be applicable when using pQCT in individuals with other chronic conditions or in older adults. Suggestions for participant screening, positioning individuals for scanning while in a wheelchair, scan site selection, need for attendant assistance, and considerations in the presence of secondary complications, such as contracture, spasticity, and paralysis, are presented. In the presence of very low bone mineral density or severe muscle atrophy, the default analysis modes provided by the manufacturer may not provide valid estimates of bone or muscle indices; we propose alternates. We have used watershed segmentation methods to determine muscle size and density based on lower precision error compared to threshold-based edge-detection segmentation, particularly for adults with SCI, where more fatty infiltration was present. By presenting our "lessons learned," we hope to reduce the learning curve for researchers using pQCT in the future.

Bone Mineral Density and Cognitive Decline in Elderly Women: Results from the InCHIANTI Study

Osteoporosis and cognitive impairment, which are highly prevalent conditions in elderly populations, share several risk factors. This study aims at evaluating the association of bone mineral density (BMD) with prevalent and incident cognitive impairment after a 3-year follow-up. We studied 655 community-dwelling women aged 65+ participating in the InCHIANTI study, who had been followed for 3 years. Total, trabecular, and cortical BMD were estimated by peripheral quantitative computed tomography using standard transverse scans at 4 and 38 % of the tibial length. Cognitive performance was evaluated using the Mini-Mental State Examination and the Trail Making Tests (TMT) A and B; a MMSE score <24 was adopted to define cognitive impairment. The TMT A-B score was calculated as the difference between TMT-A and TMT-B times (ΔTMT). The association of cognitive performance after 3 years with baseline indices of BMD was assessed by logistic and linear regression analyses. Cortical, but not trabecular, BMD was independently associated with incident cognitive impairment (OR 0.93, 95 % CI 0.88-0.98; P = 0.012), worsening cognitive performance (OR 0.96, 95 % CI 0.92-0.98; P = 0.039), and worsening performance in ΔTMT (OR 0.96, 95 % CI 0.92-0.99; P = 0.047). Increasing cortical BMD tertiles was associated with decreasing probability of incident cognitive impairment (P for linear trend =0.001), worsening cognitive performance (P = 0.013), and a worsening performance below the median value (P for linear trend <0.0001). In older women, low BMD might represent an independent and early marker of subsequent cognitive impairment. Physicians should assess and monitor cognitive performance in the routine management of elderly women with osteoporosis.

Bone morphology of the femur and tibia captured by statistical shape modelling predicts rapid bone loss in acute spinal cord injury patients

After spinal cord injury (SCI), bone loss in the paralysed limbs progresses at variable rates. Decreases in bone mineral density (BMD) in the first year range from 1% (slow) to 40% (rapid). In chronic SCI, fragility fractures commonly occur around the knee, with significant associated morbidity. Osteoporosis treatments await full evaluation in SCI, but should be initiated early and targeted towards patients exhibiting rapid bone loss. The potential to predict rapid bone loss from a single bone scan within weeks of a SCI was investigated using statistical shape modelling (SSM) of bone morphology, hypothesis: baseline bone shape predicts bone loss at 12-months post-injury at fracture-prone sites. In this retrospective cohort study 25 SCI patients (median age, 33 years) were scanned at the distal femur and proximal tibia using peripheral Quantitative Computed Tomography at <5 weeks (baseline), 4, 8 and 12 months post-injury. An SSM was made for each bone. Links between the baseline shape-modes and 12-month total and trabecular BMD loss were analysed using multiple linear regression. One mode from each SSM significantly predicted bone loss (age-adjusted P<0.05 R(2)=0.37-0.61) at baseline. An elongated intercondylar femoral notch (femur mode 4, +1 SD from the mean) was associated with 8.2% additional loss of femoral trabecular BMD at 12-months. A more concave posterior tibial fossa (tibia mode 3, +1 SD) was associated with 9.4% additional 12-month tibial trabecular BMD loss. Baseline bone shape determined from a single bone scan is a valid imaging biomarker for the prediction of 12-month bone loss in SCI patients.

Serum leptin, bone mineral density and the healing of long bone fractures in men with spinal cord injury

Previously reported fracture rates in patients with spinal cord injury range from 1% to 20%. However, the exact role of spinal cord injury in bone metabolism has not yet been clarified. In order to investigate the effects of serum leptin and bone mineral density on the healing of long bone fractures in men with spinal cord injury, 15 male SCI patients and 15 matched controls were involved in our study. The outcome indicated that at 4 and 8 weeks after bone fracture, callus production in patients with spinal cord injury was lower than that in controls. Besides, bone mineral density was significantly reduced at 2, 4 and 8 weeks. In addition, it was found that at each time point, patients with spinal cord injury had significantly higher serum leptin levels than controls and no association was found between serum leptin level and bone mineral density of lumbar vertebrae. Moreover, bone mineral density was positively correlated with bone formation in both of the groups. These findings suggest that in early phases i.e. week 4 and 8, fracture healing was impaired in patients with spinal cord injury and that various factors participated in the complicated healing process, such as hormonal and mechanical factors.

A Biomechanical Comparison of Locking Versus Conventional Plate Fixation for Distal Fibula Fractures in Trimalleolar Ankle Injuries

Previous biomechanical studies have advocated the use of locking plates for isolated distal fibula fractures in osteoporotic bone. Complex rotational ankle injuries involve an increased number of fractures, which can result in instability, potentially requiring the same fixed angle properties afforded by locking plates. However, the mechanical indication for locking plate technology has not been tested in this fracture model. The purpose of the present study was to compare the biomechanical properties of locking and conventional plate fixation for distal fibula fractures in trimalleolar ankle injuries. Fourteen (7 matched pairs) fresh-frozen cadaver leg specimens were used. The bone mineral density of each was obtained using dual x-ray absorptiometry scans. The fracture model simulated an OTA 44-B3.3 fracture. The syndesmosis was not disrupted. Each fracture was fixated in the same fashion, except for the distal fibula plate construct: locking (n = 7) and one-third tubular (n = 7). The specimens underwent axial and torsional cyclic loading, followed by torsional loading to failure. No statistically significant differences were found between the locking and conventional plate constructs during both fatigue and torque to failure testing (p > .05). Our specimen bone mineral density averages did not represent poor bone quality. The clinical implication of the present study is that distal fibular locking plates do not provide a mechanical advantage for trimalleolar ankle injuries in individuals with normal bone density and in the absence of fracture comminution.