Intravenous Bisphosphonate Therapy of Young Children With Osteogenesis Imperfecta: Skeletal Findings During Follow Up Throughout the Growing Years

Schnurri-3 inhibition rescues skeletal fragility and vascular skeletal stem cell niche pathology in the OIM model of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a disorder of low bone mass and increased fracture risk due to a range of genetic variants that prominently include mutations in genes encoding type I collagen. While it is well known that OI reflects defects in the activity of bone-forming osteoblasts, it is currently unclear whether OI also reflects defects in the many other cell types comprising bone, including defects in skeletal vascular endothelium or the skeletal stem cell populations that give rise to osteoblasts and whether correcting these broader defects could have therapeutic utility. Here, we find that numbers of skeletal stem cells (SSCs) and skeletal arterial endothelial cells (AECs) are augmented in Col1a2oim/oim mice, a well-studied animal model of moderate to severe OI, suggesting that disruption of a vascular SSC niche is a feature of OI pathogenesis. Moreover, crossing Col1a2oim/oim mice to mice lacking a negative regulator of skeletal angiogenesis and bone formation, Schnurri 3 (SHN3), not only corrected the SSC and AEC phenotypes but moreover robustly corrected the bone mass and spontaneous fracture phenotypes. As this finding suggested a strong therapeutic utility of SHN3 inhibition for the treatment of OI, a bone-targeting AAV was used to mediate Shn3 knockdown, rescuing the Col1a2oim/oim phenotype and providing therapeutic proof-of-concept for targeting SHN3 for the treatment of OI. Overall, this work both provides proof-of-concept for inhibition of the SHN3 pathway and more broadly addressing defects in the stem/osteoprogenitor niche as is a strategy to treat OI.

Clinical spectrum of rare bone fragility disorders and response to bisphosphonate treatment: a retrospective study

Osteogenesis Imperfecta (OI) is a clinically and genetically heterogeneous group of diseases characterized by brittle bones. Though genetic mutations in COL1A1 and COL1A2 account for approximately 85-90% of OI cases, there are now more than twenty genes described, responsible for rare forms of OI. Treatment is based on the use of bisphosphonates and though it is well established that they increase lumbar spine (LS) bone mineral density (BMD), the clinical impact on fracture reduction is still debated.In this study, we investigated the clinical characteristics of 38 patients with a bone fragility disorder that had variants in non-COL1A1/COL1A2 genes in order to study genotype-phenotype correlations, as the natural history of these rare forms is still not well known. We then studied the usefulness of bisphosphonate treatment by evaluating the effects on LS BMD, annual non-vertebral fracture rate, bone turnover markers and height. This study enabled us to better define the natural history of patients with non-COL1 pathogenic variants. Patients with CRTAP and TMEM38B variants consistently had a prenatal presentation with a short (<3rd p) and bowed femur. Importantly, this prenatal involvement does not predict the postnatal severity of the disease. Regarding treatment by bisphosphonates, all patients showed a significant increase in LS BMD while treated and this increase was dependent on the dose received. The increase in LS BMD also translated in a reduction of fracture rate during treatment. Finally, our study showed that the earlier bisphosphonates are initiated, the greater the fracture rate is reduced.

Safety and Efficacy of Denosumab in Children With Osteogenesis Imperfecta-the First Prospective Comparative Study

CONTEXT

Denosumab is a potential therapeutic agent for osteogenesis imperfecta (OI), but its efficacy and safety remain unclear in children with OI.

OBJECTIVE

We aimed to investigate the effects of denosumab on bone mineral density (BMD), spinal morphometry, and safety in children with OI compared with zoledronic acid.

METHODS

In this prospective study, 84 children or adolescents with OI were randomized to receive denosumab subcutaneous injection every 6 months or zoledronic acid intravenous infusion once. Changes of BMD and its Z-score, vertebral shape, serum levels of calcium and bone turnover biomarkers were assessed during the 1-year treatment.

RESULTS

After 12 months of treatment, BMD at the lumbar spine, femoral neck, and total hip significantly increased by 29.3%, 27.8%, and 30.2% in the denosumab group, and by 32.2%, 47.1%, and 41.1% in the zoledronic acid group (all P < .001 vs baseline). Vertebral height and projection area significantly increased after denosumab and zoledronic acid treatment. Rebound hypercalcemia was found to be a common and serious side effect of denosumab, of which 14.3% reached hypercalcemic crisis. Rebound hypercalcemia could be alleviated by switching to zoledronic acid treatment.

CONCLUSION

Treatment with denosumab or zoledronic acid is beneficial in increasing BMD and improving the spinal morphometry of children with OI. However, denosumab should be used with caution in pediatric patients with OI because of its common and dangerous side effect of rebound hypercalcemia. The appropriate dosage and dosing interval of denosumab need to be further explored in children with OI.

Unraveling the Link of Altered TGFβ Signaling with Scoliotic Vertebral Malformations in Osteogenesis Imperfecta: A Comprehensive Review

Osteogenesis Imperfecta (OI) is a genetic disorder caused by mutations in genes responsible for collagen synthesis or polypeptides involved in the formation of collagen fibers. Its predominant skeletal complication is scoliosis, impacting 25 to 80% of OI patients. Vertebral deformities of the scoliotic curves in OI include a variety of malformations such as codfish, wedged-shaped vertebrae or platyspondyly, craniocervical junction abnormalities, and lumbosacral spondylolysis and spondylolisthesis. Although the precise pathophysiology of these spinal deformities remains unclear, anomalies in bone metabolism have been implicated in the progression of scoliotic curves. Bone Mineral Density (BMD) measurements have demonstrated a significant reduction in the Z-score, indicating osteoporosis and a correlation with the advancement of scoliosis. Factors such as increased mechanical strains, joint hypermobility, lower leg length discrepancy, pelvic obliquity, spinal ligament hypermobility, or vertebrae microfractures may also contribute to the severity of scoliosis. Histological vertebral analysis has confirmed that changes in trabecular microarchitecture, associated with inadequate bone turnover, indicate generalized bone metabolic defects in OI. At the molecular level, the upregulation of Transforming Growth factor-β (TGFβ) signaling in OI can lead to disturbed bone turnover and changes in muscle mass and strength. Understanding the relationship between spinal clinical features and molecular pathways could unveil TGFβ -related molecular targets, paving the way for novel therapeutic approaches in OI.

Management of RANKL-mediated Disorders With Denosumab in Children and Adolescents: A Global Expert Guidance Document

CONTEXT

Denosumab is an effective treatment for many receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated disorders but there are potential safety considerations and limited data to guide its use in children and adolescents.

OBJECTIVE

This document seeks to summarize the evidence and provide expert opinion on safe and appropriate use of denosumab in pediatric RANKL-mediated disorders.

PARTICIPANTS

Ten experts in pediatric bone and mineral medicine from 6 countries with experience in the use of denosumab participated in the creation of this document.

EVIDENCE

Data were sourced from the published literature, primarily consisting of case reports/series and review articles because of the lack of higher level evidence. Expert opinion of the authors was used substantially when no published data were available.

CONCLUSION

Denosumab is an effective treatment for RANKL-mediated disorders in children and adolescents but is often not curative and, in some cases, is best used in conjunction with surgical or other medical treatments. Careful multidisciplinary planning is required to define the goals of treatment and expert oversight needed to manage the risk of mineral abnormalities. Substantive, collaborative research efforts are needed to determine optimal treatment regimens and minimize risks.

Vertebral Body Reshaping after Fractures: An Important Index of Recovery in Glucocorticoid-Treated Children

PURPOSE

In this 6-year study we identified factors associated with spontaneous vertebral body reshaping in glucocorticoid (GC)-treated children with leukemia, rheumatic disorders, and nephrotic syndrome.

METHODS

Subjects were 79 children (mean age 7.4 years) who had vertebral fracture (VF) evaluation on lateral spine radiographs at least 1 year after VF detection. VF were graded using the modified Genant semiquantitative method and fracture burden for individuals was quantified using the spinal deformity index (SDI; sum of grades from T4 to L4).

RESULTS

Sixty-five children (82.3%) underwent complete vertebral body reshaping (median time from VF detection to complete reshaping 1.3 years by Cox proportional hazard modeling). Of 237 VF, the majority (83.1%) ultimately reshaped, with 87.2% reshaping in the thoracic region vs 70.7% in the lumbar region (P = .004). Cox models showed that (1) every g/m2 increase in GC exposure in the first year after VF detection was associated with a 19% decline in the probability of reshaping; (2) each unit increase in the SDI at the time of VF detection was associated with a 19% decline in the probability of reshaping [hazard ratio (HR) = 0.81; 95% confidence interval (CI) = 0.71, 0.92; P = .001]; (3) each additional VF present at the time of VF detection reduced reshaping by 25% (HR = 0.75; 95% CI = 0.62, 0.90; P = .002); and (4) each higher grade of VF severity decreased reshaping by 65% (HR = 0.35; 95% CI = 0.21, 0.57; P < .001).

CONCLUSION

After experiencing a VF, children with higher GC exposure, higher SDI, more severe fractures, or lumbar VF were at increased risk for persistent vertebral deformity.

A practical guide to the diagnosis and management of osteoporosis in childhood and adolescence

Osteoporosis in childhood distinguishes itself from adulthood in four important ways: 1) challenges in distinguishing otherwise healthy children who have experienced fractures due to non-accidental injury or misfortunate during sports and play from those with an underlying bone fragility condition; 2) a preponderance of monogenic "early onset" osteoporotic conditions that unveil themselves during the pediatric years; 3) the unique potential, in those with residual growth and transient bone health threats, to reclaim bone density, structure, and strength without bone-targeted therapy; and 4) the need to benchmark bone health metrics to constantly evolving "normal targets", given the changes in bone size, shape, and metabolism that take place from birth through late adolescence. On this background, the pediatric osteoporosis field has evolved considerably over the last few decades, giving rise to a deeper understanding of the discrete genes implicated in childhood-onset osteoporosis, the natural history of bone fragility in the chronic illness setting and associated risk factors, effective diagnostic and monitoring pathways in different disease contexts, the importance of timely identification of candidates for osteoporosis treatment, and the benefits of early (during growth) rather than late (post-epiphyseal fusion) treatment. While there has been considerable progress, a number of unmet needs remain, the most urgent of which is to move beyond the monotherapeutic anti-resorptive landscape to the study and application of anabolic agents that are anticipated to not only improve bone mineral density but also increase long bone cross-sectional diameter (periosteal circumference). The purpose of this review is to provide a practical guide to the diagnosis and management of osteoporosis in children presenting to the clinic with fragility fractures, one that serves as a step-by-step "how to" reference for clinicians in their routine clinical journey. The article also provides a sightline to the future, emphasizing the clinical scenarios with the most urgent need for an expanded toolbox of effective osteoporosis agents in childhood.

Combination of osteogenesis imperfecta and hypophosphatasia in three children with multiple fractures, low bone mass and severe osteomalacia, a challenge for therapeutic management

Osteogenesis imperfecta (OI) and hypophosphatasia (HPP) are rare skeletal disorders caused by mutations in the genes encoding collagen type I (COL1A, COL1A2) and tissue-non-specific isoenzyme of alkaline phosphatase (ALPL), respectively. Both conditions result in skeletal deformities and bone fragility although bone tissue abnormalities differ considerably. Children with OI have low bone mass and hypermineralized matrix, whereas HPP children develop rickets and osteomalacia. We report a family, father and three children, affected with growth retardation, low bone mass and recurrent fractures. None of them had rickets, blue sclera or dentinogenesis imperfecta. ALP serum levels were low and genetics revealed in the four probands heterozygous pathogenic mutations in COL1A2 c.838G > A (p.Gly280Ser) and in ALPL c.1333T > C (p.Ser445Pro). After multidisciplinary meeting, a diagnostic transiliac bone biopsy was indicated for each sibling for therapeutic decision. Bone histology and histomorphometry, as compared to reference values of children with OI type I as well as, to a control pediatric patient harboring the same COL1A2 mutation, revealed similarly decreased trabecular bone volume, increased osteocyte lacunae, but additionally severe osteomalacia. Quantitative backscattered electron imaging demonstrated that bone matrix mineralization was not as decreased as expected for osteomalacia. In summary, we observed within each biopsy samples classical features of OI and classical features of HPP. The apparent nearly normal bone mineralization density distribution results presumably from divergent effects of OI and HPP on matrix mineralization. A combination therapy was initiated with ALP enzyme-replacement and one month later with bisphosphonates. The ongoing treatment led to improved skeletal growth, increased BMD and markedly reduced fracture incidence.

Schnurri-3 inhibition rescues skeletal fragility and vascular skeletal stem cell niche pathology in a mouse model of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a disorder of low bone mass and increased fracture risk due to a range of genetic variants that prominently include mutations in genes encoding type collagen. While it is well known that OI reflects defects in the activity of bone-forming osteoblasts, it is currently unclear whether OI also reflects defects in the many other cell types comprising bone, including defects in skeletal vascular endothelium or the skeletal stem cell populations that give rise to osteoblasts and whether correcting these broader defects could have therapeutic utility. Here, we find that numbers of skeletal stem cells (SSCs) and skeletal arterial endothelial cells (AECs) are augmented in Col1a2oim/oim mice, a well-studied animal model of moderate to severe OI, suggesting that disruption of a vascular SSC niche is a feature of OI pathogenesis. Moreover, crossing Col1a2oim/oim mice to mice lacking a negative regulator of skeletal angiogenesis and bone formation, Schnurri 3 (SHN3), not only corrected the SSC and AEC phenotypes but moreover robustly corrected the bone mass and spontaneous fracture phenotypes. As this finding suggested a strong therapeutic utility of SHN3 inhibition for the treatment of OI, a bone-targeting AAV was used to mediate Shn3 knockdown, rescuing the Col1a2oim/oim phenotype and providing therapeutic proof-of-concept for targeting SHN3 for the treatment of OI. Overall, this work both provides proof-of-concept for inhibition of the SHN3 pathway and more broadly addressing defects in the stem/osteoprogentior niche as is a strategy to treat OI.

The patient clinical journey and socioeconomic impact of osteogenesis imperfecta: a systematic scoping review

BACKGROUND

Osteogenesis imperfecta (OI) is a rare heritable connective tissue disorder primarily characterised by skeletal deformity and fragility, and an array of secondary features. The purpose of this review was to capture and quantify the published evidence relating specifically to the clinical, humanistic, and economic impact of OI on individuals, their families, and wider society.

METHODS

A systematic scoping review of 11 databases (MEDLINE, MEDLINE in-progress, EMBASE, CENTRAL, PsycINFO, NHS EED, CEA Registry, PEDE, ScHARRHUd, Orphanet and Google Scholar), supplemented by hand searches of grey literature, was conducted to identify OI literature published 1st January 1995-18th December 2021. Searches were restricted to English language but without geographical limitations. The quality of included records was assessed using the AGREE II checklist and an adapted version of the JBI cross-sectional study checklist.

RESULTS

Of the identified 7,850 records, 271 records of 245 unique studies met the inclusion criteria; overall, 168 included records examined clinical aspects of OI, 67 provided humanistic data, 6 reported on the economic impact of OI, and 30 provided data on mixed outcomes. Bone conditions, anthropometric measurements, oral conditions, diagnostic techniques, use of pharmacotherapy, and physical functioning of adults and children with OI were well described. However, few records included current care practice, diagnosis and monitoring, interactions with the healthcare system, or transition of care across life stages. Limited data on wider health concerns beyond bone health, how these concerns may impact health-related quality of life, in particular that of adult men and other family members, were identified. Few records described fatigue in children or adults. Markedly few records provided data on the socioeconomic impact of OI on patients and their caregivers, and associated costs to healthcare systems, and wider society. Most included records had qualitative limitations.

CONCLUSION

Despite the rarity of OI, the volume of recently published literature highlights the breadth of interest in the OI field from the research community. However, significant data gaps describing the experience of OI for individuals, their families, and wider society warrant further research to capture and quantify the full impact of OI.

Micro Ribonucleic Acid-29a (miR-29a) Antagonist Normalizes Bone Metabolism in Osteogenesis Imperfecta (OI) Mice Model

Osteogenesis imperfecta (OI) is not curative nowadays. This study tried to unriddle the therapeutic potential of micro ribonucleic acid-29a (miR-29a) antagonist in treating OI in a mouse animal model (B6C3Fe a/a-Col1a2oim/J). We showed that the expression levels of miR-29a were higher in bone tissues obtained from the OI mice than from wild-type mice demonstrated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and in situ hybridization assay. We established lentivirus-shuttled vector expressing miR-29a antisense oligonucleotide (miR-29a-AS) and miR-29a precursors (pre-miR-29a), showing that the inferior bony architecture in micro-computed tomography and pertinent morphometric parameters could be rescued by miR-29a-AS and deteriorated by pre-miR-29a. The decreased proliferating cell nuclear antigen (PCNA), increased Dickkopf-1 (DKK1), and decreased β-catenin expression in OI mice could be accentuated by pre-miR-29a and normalized by miR-29a-AS. The decreased osteogenesis and increased osteoclastogenesis in OI mice could also be accentuated by pre-miR-29a and normalized by miR-29a-AS. miR-29a-AS did not seem to possess severe hepatic or renal toxicities.

Multimodal Pain Management of Children Diagnosed with Osteogenesis Imperfecta: An Integrative Literature Review

OBJECTIVES

The objective of this literature review was to evaluate multimodal therapies and interventions that help prevent progression and manage pain in children with OI.

DESIGN

A systematic review of literature utilizing PRISMA guidelines.

DATA SOURCES

The Cumulative Index to Nursing and Allied Health Literature (CINAHL) Complete, PubMed, PsycINFO, UpToDate, and ProQuest Nursing & Allied Health Source.

REVIEW/ANALYSIS METHODS

Existing literature on pain management in pediatric patients diagnosed with OI was reviewed and appraised. Fifteen studies met the criteria for review.

RESULTS

Results indicated that therapies addressing pain management are most effective when they use a multimodal approach that promotes bone strength, psychological support, reduces the risk of fractures, increases bone stability, and maintains physiological function. Four multimodal treatments for pain management in children with OI were identified including bisphosphonate therapy, surgical intervention, physical therapy, and psychosocial support.

CONCLUSIONS

Developing a finite understanding of the utilization of multimodal therapies to manage and treat pain can assist in engineering treatments that improve the quality of life for children diagnosed with OI.

Bone Turnover Markers in Children: From Laboratory Challenges to Clinical Interpretation

Bone turnover markers (BTMs) have been developed many years ago to study, in combination with imaging techniques, bone remodeling in adults. In children and adolescents, bone metabolism differs from adults since it implies both growth and bone remodeling, suggesting an age- and gender-dependent BTM concentration. Therefore, specific studies have evaluated BTMs in not only physiological but also pathological conditions. However, in pediatrics, the use of BTMs in clinical practice is still limited due to these many children-related specificities. This review will discuss about physiological levels of BTMs as well as their modifications under pathological conditions in children and adolescents. A focus is also given on analytical and clinical challenges that restrain BTM usefulness in pediatrics.

Sickle cell bone disease and response to intravenous bisphosphonates in children

Children with sickle cell disease (SCD) have the potential for extensive and early-onset bone morbidity. This study reports on the diversity of bone morbidity seen in children with SCD followed at three tertiary centers. IV bisphosphonates were effective for bone pain analgesia and did not trigger sickle cell complications.

INTRODUCTION

To evaluate bone morbidity and the response to intravenous (IV) bisphosphonate therapy in children with SCD.

METHODS

We conducted a retrospective review of patient records from 2003 to 2019 at three Canadian pediatric tertiary care centers. Radiographs, magnetic resonance images, and computed tomography scans were reviewed for the presence of avascular necrosis (AVN), bone infarcts, and myositis. IV bisphosphonates were offered for bone pain management. Bone mineral density was assessed by dual-energy X-ray absorptiometry (DXA).

RESULTS

Forty-six children (20 girls, 43%) had bone morbidity at a mean age of 11.8 years (SD 3.9) including AVN of the femoral (17/46, 37%) and humeral (8/46, 17%) heads, H-shaped vertebral body deformities due to endplate infarcts (35/46, 76%), and non-vertebral body skeletal infarcts (15/46, 32%). Five children (5/26, 19%) had myositis overlying areas of AVN or bone infarcts visualized on magnetic resonance imaging. Twenty-three children (8/23 girls) received IV bisphosphonate therapy. They all reported significant or complete resolution of bone pain. There were no reports of sickle cell hemolytic crises, pain crises, or stroke attributed to IV bisphosphonate therapy.

CONCLUSION

Children with SCD have the potential for extensive and early-onset bone morbidity. In this series, IV bisphosphonates were effective for bone pain analgesia and did not trigger sickle cell complications.

Hereditary Metabolic Bone Diseases: A Review of Pathogenesis, Diagnosis and Management

Hereditary metabolic bone diseases are characterized by genetic abnormalities in skeletal homeostasis and encompass one of the most diverse groups among rare diseases. In this review, we examine 25 selected hereditary metabolic bone diseases and recognized genetic variations of 78 genes that represent each of the three groups, including sclerosing bone disorders, disorders of defective bone mineralization and disorder of bone matrix and cartilage formation. We also review pathophysiology, manifestation and treatment for each disease. Advances in molecular genetics and basic sciences has led to accurate genetic diagnosis and novel effective therapeutic strategies for some diseases. For other diseases, the genetic basis and pathophysiology remain unclear. Further researches are therefore crucial to innovate ways to overcome diagnostic challenges and develop effective treatment options for these orphan diseases.

Relationship of Pathogenic Mutations and Responses to Zoledronic Acid in a Cohort of Osteogenesis Imperfecta Children

CONTEXT

Osteogenesis imperfecta (OI) is a rare, heterogeneous, genetic disorder characterized by bone fragility and recurrent fractures. Bisphosphonates (BPs) are the most commonly used medications for OI, but their efficacy has great variability.

OBJECTIVE

We investigated the relationship of pathogenic gene mutations and responses to zoledronic acid (ZOL) in a large cohort of children with OI.

METHODS

Children with OI who received ZOL treatment were included and were followed up for at least 1 year. Bone mineral density (BMD) and serum levels of β-isomerized carboxy-telopeptide of type I collagen (β-CTX, bone resorption marker) were measured at baseline and during follow-up. Causative mutations of OI were identified using next-generation sequencing and Sanger sequencing.

RESULTS

201 children with OI were included. They had initiated ZOL treatment at a median age of 5 years, with mutations identified in 11 genes. After 3 years of treatment, the increase in femoral neck BMD Z-score in patients with OI with autosomal dominant (AD) inheritance was greater than that in patients with autosomal recessive or X-linked inheritance (non-AD) (4.5 ± 2.9 vs 2.0 ± 1.0, P < .001). Collagen structural defects were negatively correlated with the increase in femoral neck BMD Z-score. Patients with collagen structural defects had higher incidence of new fractures (35.1% vs 18.4%, relative risk 0.52, P = .044) and less decline in β-CTX level than those with collagen quantitative reduction. Increase in lumbar spine BMD and change in height Z-score was not associated with the genotype of children with OI.

CONCLUSION

Patients with OI with non-AD inheritance or with pathogenic mutations leading to collagen structural defects may have relatively poor responses to ZOL treatment, which is possibly associated with their more severe phenotypes. New therapeutic agents are worth developing in these patients.

An Unusual Diagnosis of Sporadic Type III Osteogenesis Imperfecta in the First Day of Life

Osteogenesis imperfecta (OI) is a group of rare, permanent genetic bone disorders resulting from the mutations in genes encoding type 1 collagen. It usually is inherited by an autosomal dominant pattern, but it can sometimes occur sporadically. Among the four main types, type III is the most severe type which presents with multiple bone fractures, skeletal deformities, blue sclera, hearing, and dental abnormalities. It is estimated that only 1 in 20,000 cases of OI are detected during infancy, and the diagnosis carries a poor prognosis. This case is reported for the rarity of sporadic OI diagnosis in neonates. We present a case of a 1-day-old neonate following a normal vaginal delivery referred to our center in the view of low birth weight and multiple bony deformities. Physical examination revealed an ill-looking child with poor suckling, gross bony deformities in upper and lower limbs, and blue sclera. X-ray showed thin gracile bones with multiple bone fractures. Echocardiography revealed a 4 mm patent ductus arteriosus. The patient was diagnosed with type III OI with patent ductus arteriosus. Though OI is rare in neonates and infants, it should be considered in the differentials in a newborn presenting with multiple bony deformities regardless of family history, history of trauma, or physical abuse. OI is also associated with cardiac anomalies such as the atrial septal defect and patent ductus arteriosus for which echocardiography is recommended routinely.

Pamidronate Therapy Increases Trabecular Bone Complexity of Mandibular Condyles in Individuals with Osteogenesis Imperfecta

Patients with Osteogenesis Imperfecta (OI) present extra-skeletal manifestations, including important orodental and craniofacial features as dentinogenesis imperfecta, dental agenesis, failure of maxilla growth and hypotonia of masticatory muscles. These features may compromise vital functions speech and mastication. Studies have demonstrated that cyclic pamidronate infusion, the standard therapy for patients with moderate to severe OI, influences the histomorphometric pattern of different body bones. The present study aimed to investigate the condyle trabecular bone pattern in OI patients. We used fractal dimension (FD) analysis on dental panoramic radiographic images to characterize the mandibular condyle trabecular bone in adolescents diagnosed with OI and treated with pamidronate. Imaging exam of 33 adolescents of both sexes, aged between 12 and 17 years, were analyzed and compared with 99 age- and sex-matched healthy adolescents. FD in patients was significantly lower (1.23 ± 0.15) than in healthy controls (1.29 ± 0.11; p < 0.01). Type of OI, age at treatment onset, and the duration of therapy were variables that showed a statistically significant effect on the FD results. This study demonstrated that the bone architecture of mandibular condyles may be altered in pediatric patients with moderate and severe forms of OI. Also, pamidronate treatment seems to have a positive effect on condyle trabecular bone in these patients. This is supported by our finding that FD values were positively influenced by the length of cyclic pamidronate treatment at the time of imaging, as well as by the age of the individual at treatment onset.

Phenotypic Spectrum and Molecular Basis in a Chinese Cohort of Osteogenesis Imperfecta With Mutations in Type I Collagen

Osteogenesis imperfecta (OI) is a rare inherited connective tissue dysplasia characterized with skeletal fragility, recurrent fractures and bone deformity, predominantly caused by mutations in the genes COL1A1 or COL1A2 that encode the chains of type I collagen. In the present study, clinical manifestations and genetic variants were analysed from 187 Chinese OI patients, majority of whom are of southern Chinese origin. By targeted sequencing, 63 and 58 OI patients were found carrying mutations in COL1A1 and COL1A2 respectively, including 8 novel COL1A1 and 7 novel COL1A2 variants. We validated a novel splicing mutation in COL1A1. A diverse mutational and phenotypic spectrum was observed, coupling with the heterogeneity observed in the transcriptomic data derived from osteoblasts of six patients from our cohort. Missense mutations were significantly associated (χ²p = 0.0096) with a cluster of patients with more severe clinical phenotypes. Additionally, the severity of OI was more correlated with the quality of bones, rather than the bone mineral density. Bone density is most responsive to bisphosphonate treatment during the juvenile stage (10–15 years old). In contrast, height is not responsive to bisphosphonate treatment. Our findings expand the mutational spectrum of type I collagen genes and the genotype-phenotype correlation in Chinese OI patients. The observation of effective bisphosphonate treatment in an age-specific manner may help to improve OI patient management.

4PBA reduces growth deficiency in osteogenesis imperfecta by enhancing transition of hypertrophic chondrocytes to osteoblasts

Short stature is a major skeletal phenotype in osteogenesis imperfecta (OI), a genetic disorder mainly caused by mutations in genes encoding type I collagen. However, the underlying mechanism is poorly understood, and no effective treatment is available. In OI mice that carry a G610C mutation in COL1A2, we previously found that mature hypertrophic chondrocytes (HCs) are exposed to cell stress due to accumulation of misfolded mutant type I procollagen in the endoplasmic reticulum (ER). By fate mapping analysis of HCs in G610C OI mice, we found that HCs stagnate in the growth plate, inhibiting translocation of HC descendants to the trabecular area and their differentiation to osteoblasts. Treatment with 4-phenylbutyric acid (4PBA), a chemical chaperone, restored HC ER structure and rescued this inhibition, resulting in enhanced longitudinal bone growth in G610C OI mice. Interestingly, the effects of 4PBA on ER dilation were limited in osteoblasts, and the bone fragility was not ameliorated. These results highlight the importance of targeting HCs to treat growth deficiency in OI. Our findings demonstrate that HC dysfunction induced by ER disruption plays a critical role in the pathogenesis of OI growth deficiency, which lays the foundation for developing new therapies for OI.

Skeletal outcomes of patients with osteogenesis imperfecta during drug holiday of bisphosphonates: a real-world study

PURPOSE

This study aimed to investigate the skeletal outcomes of patients with osteogenesis imperfecta (OI) who received bisphosphonate (BP) treatment and entered drug holiday after achieving an age- and sex-specific bone mineral density (BMD) reference.

METHODS

Patients with OI receiving BP treatment were enrolled when they entered drug holidays of BPs. The skeletal outcomes were evaluated in detail during the drug holiday, including BMD, X-ray of the bone, bone fracture incidence, and bone turnover biomarkers. The pathogenic mutations of OI were identified by next-generation sequencing and confirmed by Sanger sequencing.

RESULTS

A total of 149 OI patients (127 juveniles and 22 adults) who entered drug holidays after nearly 4 years of BP treatment were included. Areal BMD at the lumbar spine increased from 0.934 ± 0.151 to 0.990 ± 0.142 g/cm² and was stable in the second (1.029 ± 0.176 g/cm²) and third years (1.023 ± 0.174 g/cm²) of BP drug holidays, and BMD at the femoral neck, trochanter, and total hip had no significant change, but it was gradually inferior to that of the same-gender juveniles in the second and third years of the drug holiday. BMD at the lumbar spine and proximal hip did not change and was inferior to that of the same-gender adults. The average time of fractures fluctuated from 0.18 to 0.08 per year in juveniles, while only one adult suffered from a fracture during BP drug holidays. Bone turnover markers were in the normal range, except for a mildly high level of β-carboxy-terminal cross-linked telopeptide of type 1 collagen in the juvenile group. A total of 17 (11.4%) patients received BP retreatment because of bone loss during the drug holiday. OI type III and type IV and COL1A2 mutation were correlated to a longer duration of BP treatment to enter drug holidays (all p < 0.05). Old age at initial treatment (OR, 1.056) and OI type III (OR, 10.880) were correlated to a higher risk of BP retreatment.

CONCLUSIONS

OI patients will undergo nearly 4 years of BP treatment to achieve drug holidays. During the 3 years of the drug holiday, the patients' BMD is stable, and fracture incidence does not increase significantly. Patients are more inclined to need retreatment during drug holidays owing to the late start of BP treatment and more severe OI phenotypes.

Osteoporotic Fractures and Vertebral Body Reshaping in Children With Glucocorticoid-treated Rheumatic Disorders

CONTEXT

Osteoporotic fractures are an important cause of morbidity in children with glucocorticoid-treated rheumatic disorders.

OBJECTIVE

This work aims to evaluate the incidence and predictors of osteoporotic fractures and potential for recovery over six years following glucocorticoid (GC) initiation in children with rheumatic disorders.

METHODS

Children with GC-treated rheumatic disorders were evaluated through a prospective inception cohort study led by the Canadian STeroid-induced Osteoporosis in the Pediatric Population (STOPP) Consortium. Clinical outcomes included lumbar spine bone mineral density (LS BMD), vertebral fractures (VF), non-VF, and vertebral body reshaping.

RESULTS

A total of 136 children with GC-treated rheumatic disorders were enrolled (mean age 9.9 years, SD 4.4). The 6-year cumulative fracture incidence was 16.3% for VF, and 10.1% for non-VF. GC exposure was highest in the first 6 months, and 24 of 38 VF (63%) occurred in the first 2 years. Following VF, 16 of 19 children (84%) had complete vertebral body reshaping. Increases in disease activity and body mass index z scores in the first year and declines in LS BMD z scores in the first 6 months predicted incident VF over the 6 years, while higher average daily GC doses predicted both incident VF and non-VF. LS BMD z scores were lowest at 6 months (mean -0.9, SD 1.2) and remained low by 6 years even when adjusted for height z scores (-0.6, SD 0.9).

CONCLUSION

VF occurred early and were more common than non-VF in children with GC-treated rheumatic disorders. Eighty-four percent of children with VF underwent complete vertebral body reshaping, whereas vertebral deformity persisted in the remainder of children. On average, LS BMD z scores remained low at 6 years, consistent with incomplete recovery.

Hematopoietic stem cell-derived functional osteoblasts exhibit therapeutic efficacy in a murine model of osteogenesis imperfecta

Currently, there is no cure for osteogenesis imperfecta (OI)-a debilitating pediatric skeletal dysplasia. Herein we show that hematopoietic stem cell (HSC) therapy holds promise in treating OI. Using single-cell HSC transplantation in lethally irradiated oim/oim mice, we demonstrate significant improvements in bone morphometric, mechanics, and turnover parameters. Importantly, we highlight that HSCs cause these improvements due to their unique property of differentiating into osteoblasts/osteocytes, depositing normal collagen-an attribute thus far assigned only to mesenchymal stem/stromal cells. To confirm HSC plasticity, lineage tracing was done by transplanting oim/oim with HSCs from two specific transgenic mice-VavR, in which all hematopoietic cells are GFP+ and pOBCol2.3GFP, where GFP is expressed only in osteoblasts/osteocytes. In both models, transplanted oim/oim mice demonstrated GFP+ HSC-derived osteoblasts/osteocytes in bones. These studies unequivocally establish that HSCs differentiate into osteoblasts/osteocytes, and HSC transplantation can provide a new translational approach for OI.

Calvarial doughnut lesions with bone fragility in a French-Canadian family; case report and review of the literature

Calvarial Doughnut Lesions with Bone Fragility (CDL) is an autosomal dominant genetic disease, characterized by low bone mineral density, multiple fractures starting in childhood, and sclerotic doughnut-shaped lesions in the cranial bones. Aubé and colleagues described in 1988 a French-Canadian family of 12 affected members who had a clinical diagnosis of doughnut lesions of the skull, with pathological fractures, osteopenia, "bone in bone" in the vertebral bodies and squaring of metatarsal and metacarpal bones. Herein we study new members of this family. Sequential genetic testing identified a nonsense variant c.148C>T, p. Arg50^⁎ in SGMS2 previously reported in other families. SGMS2 encodes Sphingomyelin Synthase 2, which produces Sphingomyelin (SM), a major lipid component of the plasma membrane that plays a role in bone mineralization. The nonsense variant is associated with milder phenotype. The proband presents with bone in bone vertebral appearance that had been defined uniquely in the first cases described in the same family. The proband's son was identified to carry the same variant, which makes him the sixth generation with the diagnosis of CDL. We also report that the same pathogenic variant was identified in another previously described family, from France. These reports further confirm the genetic basis of CDL, the recurrence of the same variant (p.Arg50*) in individuals of the same ancestry, and the variable penetrance of some of the clinical findings.

High Bone Mineral Density Osteogenesis Imperfecta in a Family with a Novel Pathogenic Variant in COL1A2

Osteogenesis imperfecta (OI) is a heterogenous group of heritable bone dysplasias characterized by bone fragility, typically low bone mass, joint laxity, easy bruising, and variable short stature. Classical OI is caused by autosomal dominant pathogenic variants in COL1A1 or COL1A2 that result in either reduced production of normal type 1 collagen or structurally abnormal collagen molecules. Pathogenic variants in these genes generally result in low bone mass. Here, we report a family that had 2 affected individuals who presented with minimal trauma fractures and were found to have elevated bone mineral density (BMD) and a previously unreported variant in COL1A2 c.3356C>T p.(Ala1119Val). We report the change in BMD using dual-energy X-ray and peripheral quantitative computed tomography over a 2.3-year period in the proband. This case report highlights the importance of BMD studies and genetic testing in the diagnostic process for brittle bone disorders.

A quality improvement project to address the challenges surrounding zoledronic acid use in children

INTRODUCTION

Zoledronic acid (ZA) is an intravenous bisphosphonate used to treat pediatric osteoporosis. Adverse events including hypocalcemia and acute phase reaction (APR) are common following first-infusion. The purpose of this report is to describe implementation of a ZA clinical practice guideline and the subsequent process changes to improve adherence to aspects of the protocol related to safety and efficacy.

METHODS

Quality assurance was evaluated by chart review over a 5-year period to compare the prevalence of hypocalcemia and APR to published data. A quality improvement (QI) initiative consisting of process changes including the addition of an endocrine RN to coordinate infusions and a shift to patient/family self-scheduling of infusions was conducted. The effect of the interventions on safety (completion of pre- and post-infusion bloodwork) and efficacy (receipt of all prescribed infusions) outcomes was evaluated.

RESULTS

Seventy-two patients received 244 infusions over the period. The frequency of hypocalcemia (22%) and APR (31%) was consistent with prior reports. 99% of patients received pre-infusion bloodwork, 78% received post-first-infusion bloodwork, and 47% received all prescribed infusions. QI initiatives increased the percentage of patients receiving post-first-infusion bloodwork from 67 to 79% and those receiving all infusions from 62 to 74%, but fell short of the goal of 90%.

CONCLUSIONS

The implementation of a standardized protocol for ZA use in children was successful in confirming patient eligibility with pre-infusion bloodwork but failed to ensure that patients obtained post-first-infusion bloodwork and received all prescribed infusions. Further efforts to systematize the management of children on ZA are needed.

Surgical Outcome of Spinal Fusion for Osteogenesis Imperfecta With Scoliosis: Is the Hybrid System With Pedicle Screws Applicable to Weak, Tiny, and Fragile Vertebrae?

INTRODUCTION

Corrective surgery for spinal deformity associated with osteogenesis imperfecta (OI) is challenging due to the severe and rigid deformity combined with extreme bone fragility. However, surgical outcomes still remain unclear. In addition, the applicability of pedicle screws (PSs) to the tiny and fragile vertebrae in patients with OI is poorly understood. This study evaluated the surgical outcome, and the accuracy and safety of PS placement in patients with OI.

METHODS

Twenty-five patients with OI were included in this study. Mean age was 21.0±9.3 (10 to 49) years. Mean follow-up was 5.8±2.0 years. The Sillence classification showed 16 patients had the mildest type I, 1 patient had moderate type IV, and 8 patients had the most severe type III. Fifteen patients underwent anterior release followed by posterior fusion, and 10 patients underwent only posterior fusion. The accuracy of PS placement was evaluated with postoperative computed tomography.

RESULTS

Scoliosis was corrected from 95.6 to 65.8 degrees after surgery (correction rate 32.5%) and 68.1 degrees at final follow-up (both, P<0.01). Space available for the lung was improved from 76.3% to 84.9% (P<0.05). No implant dislodgement occurred after surgery. A total of 290 screws were placed, of which 213 screws (73.4%) were placed completely. However, 30 screws (10.3%) penetrated >2 mm. In particular, rates of >2 mm penetration was much higher in type III than type I and IV (27.8% vs. 3.0%; P<0.01). Complications related to spinal surgery included 2 transient neurological disturbances.

CONCLUSIONS

PSs were applicable to spinal fusion surgery in patients with OI. However special care should be taken in placing PSs because of the weakness of the pedicle cortex, which was easily penetrated especially in Sillence type III.

LEVEL OF EVIDENCE

Level IV.

Compressive Strength of Iliac Bone ECM Is Not Reduced in Osteogenesis Imperfecta and Increases With Mineralization

Osteogenesis imperfecta (OI) is an inheritable, genetic, and collagen-related disorder leading to an increase in bone fragility, but the origin of its "brittle behavior" is unclear. Because of its complex hierarchical structure, bone behaves differently at various length scales. This study aims to compare mechanical properties of human OI bone with healthy control bone at the extracellular matrix (ECM) level and to quantify the influence of the degree of mineralization. Degree of mineralization and mechanical properties were analyzed under dry conditions in 12 fixed and embedded transiliac crest biopsies (control n = 6, OI type I n = 3, OI type IV n = 2, and OI type III n = 1). Mean degree of mineralization was measured by microcomputed tomography at the biopsy level and the mineral-to-matrix ratio was assessed by Raman spectroscopy at the ECM level. Both methods revealed that the degree of mineralization is higher for OI bone compared with healthy control. Micropillar compression is a novel technique for quantifying post-yield properties of bone at the ECM level. Micropillars (d = 5 μm, h = 10 μm) were fabricated using focused ion beam milling and quasi-statically compressed to capture key post-yield properties such as ultimate strength. The qualitative inspection of the stress-strain curves showed that both OI and healthy control bone have a ductile response at the ECM level. The quantitative results showed that compressive strength is not reduced in OI bone and is increasing with OI severity. Nanoindentation measurements revealed that OI bone tends to have a higher Young's modulus, hardness, and dissipated energy compared with healthy bone. Micropillar strength and indentation modulus increased linearly and significantly (p < .0001) with mineral-to-matrix ratio. In conclusion, this study indicates that compressive mechanical properties of dry OI bone at the iliac crest are not inferior to healthy control at the ECM level and increase with mineralization. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Effects of treatment with a bone-targeted prostaglandin E2 receptor 4 agonist C3 (Mes-1007) in a mouse model of severe osteogenesis imperfecta

OBJECTIVE

Osteogenesis imperfecta (OI) is a heritable bone fragility disorder that is usually caused by mutations affecting collagen type I synthesis in osteoblasts. Bisphosphonates are widely used to decrease fracture rate but are only partially effective. Bone anabolic compounds, such as prostaglandin E2 receptor 4 (EP4) agonists may be an alternative treatment approach. Here we assessed the effect of Mes-1007, a novel bone-targeted EP4 agonist in Jrt mice, a model of severe OI.

STUDY DESIGN

Experimental study.

RESULTS

Male 8-week old wild type (WT) and OI mice were randomly assigned to 4 weeks of three intraperitoneal injections per week with Mes-1007 (25 mg per kg body mass), phosphate-buffered saline, zoledronate (5 μg per kg), or a combination treatment of zoledronate and Mes-1007. Treatment with Mes-1007 alone did not lead to higher trabecular bone volume per tissue volume (BV/TV) in the distal femur or lumbar vertebra 4 in either WT or OI mice. Treatment with zoledronate alone was associated with a significant increase in distal femur and vertebra BV/TV in both genotypes. In zoledronate-treated WT and OI mice, Mes-1007 increased bone formation rate in vertebral trabecular bone and had an additive effect on BV/TV. Vertebral BV/TV in OI mice that received zoledronate or Mes-1007/zoledronate combination treatment was similar to untreated WT mice (p = 0.25). At the femoral midshaft, Mes-1007/zoledronate combination treatment increased cortical thickness in both genotypes and led to higher periosteal diameter in OI mice. Three-point bending tests of femurs showed that Mes-1007/zoledronate combination treatment increased the stiffness, load at yield and maximal load in WT but not in OI mice.

CONCLUSION

Dosing Mes-1007 in combination with zoledronate improved the bone properties in a manner that is consistent with a mechanism of action of EP4 agonists on bone and additive to effects of anti-resorptives typified by zoledronate.

Vertebral fracture assessment (VFA) for monitoring vertebral reshaping in children and adolescents with osteogenesis imperfecta treated with intravenous neridronate

PURPOSE

The study was aimed at monitoring vertebral bodies changes with the use of Vertebral Fracture Assessment (VFA) in children and adolescents affected by osteogenesis imperfecta (OI) during treatment with intravenous neridronate.

METHODS

60 children and adolescents (35 males and 25 females; age 1-16 years) with OI type I, III and IV were included in the study. Intravenous neridronate was administered at the dose of 2 mg/kg every 3 months in all patients. Lumbar spine (LS) bone mineral density (BMD) and VFA by dual X-ray absorptiometry (DXA) were assessed every 6 months up to 24 months during treatment. VFA with vertebral morphometry (MXA) was used to calculate the three indices of vertebral deformity: wedging, concavity and crushing. Serum calcium, phosphate, parathyroid hormone (PTH), 25-hydroxy-vitamin D [25(OH)D], total alkaline phosphatase (ALP), bone alkaline phosphatase (BALP) and urinary C-terminal telopeptide of type 1 collagen (CTx) were measured at any time point.

RESULTS

Mean LS BMD values significantly increased at 24 months compared to baseline (p < 0.0001); the corresponding Z-score values were -1.28 ± 1.23 at 24 months vs -2.46 ± 1.25 at baseline; corresponding mean Bone Mineral Apparent Density (BMAD) values were 0.335 ± 0.206 vs 0.464 ± 0.216. Mean serum levels of ALP, BALP and CTx significantly decreased from baseline to 24 months. By MXA, we observed a significant 19.1% reduction of the mean wedging index of vertebral reshaping at 12 months, and 38.4% at 24 months (p < 0.0001) and of the mean concavity index (16.3% at 12 months and 35.9% at 24 months; p < 0.0001). Vertebral reshaping was achieved for 66/88 (75%) wedge fractures and 59/70 (84%) concave fractures, but there were 4 incident mild fractures. Finally, VF rate was reduced at 24 months compared to baseline: 37/710 (5.2%) vs 158/710 (22.2%).

CONCLUSION

Our study demonstrates the utility of VFA as a safe and alternative methodology in the follow-up of children and adolescents with OI.

Intravenous pamidronate for treatment of osteogenesis imperfecta in Indian children

Osteogenesis imperfecta is characterised by low bone mineral density, bone fragility, fractures and deformity. We present five such children treated with intravenous pamidronate, which resulted in a decrease of fracture rate and increase in spinal bone mineral density.

Predicting ambulatory function at skeletal maturity in children with moderate to severe osteogenesis imperfecta

Maximizing ambulation is a key treatment aim in moderate to severe osteogenesis imperfecta (OI). Here we investigated which early clinical characteristics predicted ambulation function at skeletal maturity. We assessed Bleck ambulation scores in 88 individuals with OI at 5 to 6 years of age and again at final height (at 15 to 24 years of age). At 5 to 6 years of age, 33 (38%) children were non-ambulators, 32 (36%) were fully independent ambulators, and 23 (26%) had intermediate ambulation skills. At skeletal maturity, 58% of the study participants had the same mobility level as at first assessment. The ability to ambulate independently at skeletal maturity was predicted by independent ambulation at 5 to 6 years (odds ratio [OR] 22.6, 95% confidence interval [CI] 4.9-105; P < 0.001), height z score at 5 to 6 years (OR 3.1, CI 1.6-6.3; P = 0.001) and weight z score at 5 to 6 years (OR 0.44, CI 0.19-0.99; P = 0.04).Conclusion: Independent ambulation at 5 to 6 years was the main determinant of independent ambulation at skeletal maturity. This highlights the importance of maximizing ambulation in children below 5 years of age. What is Known: •walking ability varies markedly between OI types. The highest level of mobility was found in OI type I, the lowest in OI type III who require mobility aids; intermediate levels were reported for OI type IV. • OI type is a key predictor of ultimate ability to ambulate, whereas the timing of developmental milestones was not associated with walking ability What is New: • overall key predictors of mobility function at skeletal maturity were mobility status and height z-score at 5-6 years of age • Childrenwho were non-ambulators at 5 to 6 years of age had a higher chance of having better mobility at skeletal maturity if they had good upper extremity function, as expressed in the PEDI Self Care Score.

Glucocorticoid-Induced Osteoporosis: Why Kids Are Different

Glucocorticoids (GC) are an important risk factor for bone fragility in children with serious illnesses, largely due to their direct adverse effects on skeletal metabolism. To better appreciate the natural history of fractures in this setting, over a decade ago the Canadian STeroid-associated Osteoporosis in the Pediatric Population ("STOPP") Consortium launched a 6 year, multi-center observational cohort study in GC-treated children. This study unveiled numerous key clinical-biological principles about GC-induced osteoporosis (GIO), many of which are unique to the growing skeleton. This was important, because most GIO recommendations to date have been guided by adult studies, and therefore do not acknowledge the pediatric-specific principles that inform monitoring, diagnosis and treatment strategies in the young. Some of the most informative observations from the STOPP study were that vertebral fractures are the hallmark of pediatric GIO, they occur early in the GC treatment course, and they are frequently asymptomatic (thereby undetected in the absence of routine monitoring). At the same time, some children have the unique, growth-mediated ability to restore normal vertebral body dimensions following vertebral fractures. This is an important index of recovery, since spontaneous vertebral body reshaping may preclude the need for osteoporosis therapy. Furthermore, we now better understand that children with poor growth, older children with less residual growth potential, and children with ongoing bone health threats have less potential for vertebral body reshaping following spine fractures, which can result in permanent vertebral deformity if treatment is not initiated in a timely fashion. Therefore, pediatric GIO management is now predicated upon early identification of vertebral fractures in those at risk, and timely intervention when there is limited potential for spontaneous recovery. A single, low-trauma long bone fracture can also signal an osteoporotic event, and a need for treatment. Intravenous bisphosphonates are currently the recommended therapy for pediatric GC-induced bone fragility, typically prescribed to children with limited potential for medication-unassisted recovery. It is recognized, however, that even early identification of bone fragility, combined with timely introduction of intravenous bisphosphonate therapy, may not completely rescue the osteoporosis in those with the most aggressive forms, opening the door to novel strategies.

Management of primary and secondary osteoporosis in children

Osteoporosis in children differs from adults in terms of definition, diagnosis, monitoring and treatment options. Primary osteoporosis comprises primarily of osteogenesis imperfecta (OI), but there are significant other causes of bone fragility in children that require treatment. Secondary osteoporosis can be a result of muscle disuse, iatrogenic causes, such as steroids, chronic inflammation, delayed or arrested puberty and thalassaemia major. Investigations involve bone biochemistry, dual-energy X-ray absorptiometry scan for bone densitometry and vertebral fracture assessment, radiographic assessment of the spine and, in some cases, quantitative computed tomography (QCT) or peripheral QCT. It is important that bone mineral density (BMD) results are adjusted based on age, gender and height, in order to reflect size corrections in children. Genetics are being used increasingly for the diagnosis and classification of various cases of primary osteoporosis. Bone turnover markers are used less frequently in children, but can be helpful in monitoring treatment and transiliac bone biopsy can assist in the diagnosis of atypical cases of osteoporosis. The management of children with osteoporosis requires a multidisciplinary team of health professionals with expertise in paediatric bone disease. The prevention and treatment of fragility fractures and improvement of the quality of life of patients are important aims of a specialised service. The drugs used most commonly in children are bisphosphonates, that, with timely treatment, can give good results in improving BMD and reshaping vertebral fractures. The data regarding their effect on reducing long bone fractures are equivocal. Denosumab is being used increasingly for various conditions with mixed results. There are more drugs trialled in adults, but these are not yet licenced for children. Increasing awareness of risk factors for paediatric osteoporosis, screening and referral to a specialist team for appropriate management can lead to early detection and treatment of asymptomatic fractures and prevention of further bone damage.

Parents' Perceptions of Health-Related Quality of Life of Children Diagnosed with Osteogenesis Imperfecta

PURPOSE

The purpose of this research was to describe the health-related quality of life (HRQoL) perceptions of parents of children diagnosed with osteogenesis imperfecta (OI).

DESIGN AND METHODS

This research used a descriptive design with a comparative sample. The Child Health Questionnaire (CHQ-PF 28) parent form was used to assess HRQoL in a sample of 37 parents from a mid-western tertiary pediatric hospital OI specialty clinic. Comparisons were made with a sample of parents of well children.

RESULTS

Parent HRQoL perception scores were described in both the physical and psycho-social-emotional domains. The domains of physical function (PF), bodily pain (BP), general health (GH), parent impact-emotional (PE), and child self-esteem (SE) were the lowest HRQoL mean domain scores for the parents of the children diagnosed with OI. Ceiling and floor scores were calculated to describe the magnitude of the differences between the mean HRQoL perception domain scores of the two parent groups.

CONCLUSIONS

Low HRQoL physical and psycho-social-emotional mean domain scores in conjunction with small percentage scores in the ceiling (and greater percentage scores in the floor) for parents of children diagnosed with OI were described. Findings suggest the on-going need for research to identify interventions to promote physical functioning for the child diagnosed with OI. Outcome based programs for parent and family-centered psycho-social self-care should be developed. PracticeImplications: ip Comprehensive and longitudinal assessment of HRQoL for both parents and their children diagnosed with OI will assist in documenting the outcomes of interventions for the management of chronic care.

Growing Rod Surgery for Early-Onset Scoliosis in an Osteogenesis Imperfecta Patient

BACKGROUND

Osteogenesis imperfecta (OI) is characterized by bone fragility and is often accompanied by spinal deformity. Surgical treatment for early-onset scoliosis in patients with OI is hazardous and difficult due to the bone fragility and rigidity of the deformity. A case of early-onset scoliosis with OI that was treated using growing-rod surgery is presented.

CASE DESCRIPTION

The patient was an 11-year-old girl with type 4 OI. At the age of 4 years, she was noted to have scoliosis. Preoperative radiographs showed that the Cobb angle, thoracic kyphosis angle, and T1-S1 height were 94°, 77°, and 258 mm, respectively. One year before the operation, she underwent cyclic intravenous pamidronate disodium treatment. Three months after the pedicle screws were inserted, the growing rods were placed with pedicle screws and sublaminar polyethylene tape. The patient had intraoperative traction for correction. At 13 years and 11 months, the patients underwent posterior instrumentation and spinal fusion. Postoperative radiographs showed that the Cobb angle, thoracic kyphosis angle, and T1-S1 height were 29°, 29°, and 405 mm, respectively. Three months after the operation, she was well, and there have been no spine-related problems.

CONCLUSIONS

This case demonstrates the successful use of the growing rod for early-onset scoliosis in patients with OI. The treatment strategy, which included pedicle screw insertion as anchors to create the foundations in advance, sublaminar tape, intraoperative traction, and preoperative bisphosphonate administration, might have led to the good outcome.

Diagnosis and management of pediatric metabolic bone diseases associated with skeletal fragility

PURPOSE OF REVIEW

The goal of this review is to give an overview of diagnosis and up-to-date management of major pediatric metabolic bone diseases that are associated with bone fragility, including nutritional rickets, hypophosphatemic rickets, osteogenesis imperfecta, Ehlers--Danlos syndrome, Marfan's syndrome, hypophosphatasia, osteopetrosis and skeletal fluorosis.

RECENT FINDINGS

During the past decade, a number of advanced treatment options have been introduced and shown to be an effective treatment in many metabolic bone disorders, such as burosumab for hypophosphatemic rickets and asfotase alfa for hypophosphatasia. On the other hand, other disorders, such as nutritional rickets and skeletal fluorosis continue to be underrecognized in many regions of the world. Genetic disorders of collagen-elastin, such as osteogenesis imperfecta, Ehlers--Danlos syndrome and Marfan's syndrome are also associated with skeletal fragility, which can be misdiagnosed as caused by non-accidental trauma/child abuse.

SUMMARY

It is essential to provide early and accurate diagnosis and treatment for pediatric patients with metabolic bone disorders in order to maintain growth and development as well as prevent fractures and metabolic complications.

A Multicenter Study of Intramedullary Rodding in Osteogenesis Imperfecta

BACKGROUND

Osteogenesis imperfecta (OI), a heritable connective tissue disorder with wide clinical variability, predisposes to recurrent fractures and bone deformity. Management requires a multidisciplinary approach in which intramedullary rodding plays an important role, especially for moderate and severe forms. We investigated the patterns of surgical procedures in OI in order to establish the benefits of rodding. The main hypothesis that guided this study was that rodded participants with moderate and severe OI would have lower fracture rates and better mobility.

METHODS

With data from the Linked Clinical Research Centers, we analyzed rodding status in 558 individuals. Mobility and fracture data in OI Types III and IV were compared between rodded and non-rodded groups. Univariate regression analyses were used to test the association of mobility outcomes with various covariates pertinent to rodding.

RESULTS

Of the individuals with OI, 42.1% had undergone rodding (10.7% of those with Type I, 66.4% with Type III, and 67.3% with Type IV). Rodding was performed more frequently and at a younger age in femora compared with tibiae. Expanding intramedullary rods were used more frequently in femora. In Type III, the rate of fractures per year was significantly lower (p ≤ 0.05) for rodded bones. In Type III, the mean scores on the Gillette Functional Assessment Questionnaire (GFAQ) and Brief Assessment of Motor Function (BAMF) were higher in the rodded group. However, Type-IV non-rodded subjects had higher mean scores in nearly all mobility outcomes. OI type, the use of expanding rods in tibiae, and anthropometric measurements were associated with mobility outcomes scores.

CONCLUSIONS

Current practice in 5 orthopaedic centers with extensive experience treating OI demonstrates that most individuals with moderate and severe types of OI undergo rodding procedures. Individuals with severe OI have improved mobility outcomes and lower fracture rates compared with their non-rodded peers, which suggests that early bilateral rodding benefits OI Type III. Our analysis showed a change in practice patterns in the final years of the study in the severe forms, with earlier and more simultaneous rodding procedures performed.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Musculoskeletal phenotype in two unrelated individuals with a recurrent nonsense variant in SGMS2

Heterozygous mutations in the gene encoding the sphingomyelin synthase 2, SGMS2, have recently been linked to childhood-onset osteoporosis and skeletal dysplasia. One nonsense variant at position c.148C>T (p.Arg50*) has been associated with mild bone fragility with or without cranial sclerosis. Here we assessed the effect of the SGMS2 p.Arg50* variant in two unrelated probands with childhood-onset osteoporosis and their unaffected family members. We found that the p.Arg50* variant was associated with phenotypic variability, ranging from absence of a bone phenotype to severe vertebral compression fractures and low lumbar spine areal bone mineral density (BMD) as measured by dual energy x-ray absorptiometry. Peripheral quantitative computed tomography of the radius and tibia in the two probands revealed low cortical volumetric BMD and reduced cortical thickness. In addition, both probands were obese and suffered from muscle function deficits compared to sex- and age-matched controls. Long-term bisphosphonate treatment was associated with reshaping of previously compressed vertebral bodies.

Finite element analysis of bone strength in osteogenesis imperfecta

As a dedicated experimentalist, John Currey praised the high potential of finite element (FE) analysis but also recognized its critical limitations. The application of the FE methodology to bone tissue is reviewed in the light of his enthusiastic and colorful statements. In the past decades, FE analysis contributed substantially to the understanding of structure-function properties in the hierarchical organization of bone and to the simulation of bone adaptation. The systematic experimental validation of FE analysis of bone strength in anatomical locations at risk of fracture led to its application in clinical studies to evaluate efficacy of antiresorptive or anabolic treatment of bone fragility. Beyond the successful analyses of healthy or osteoporotic bone, FE analysis becomes increasingly involved in the investigation of other fragility-related bone diseases. The case of osteogenesis imperfecta (OI) is exposed, the multiscale alterations of the bone tissue and the effect of treatment summarized. A few FE analyses attempting to answer open questions in OI are then reported. An original study is finally presented that explored the structural properties of the Brtl/+ murine model of OI type IV subjected to sclerostin neutralizing antibody treatment using microFE analysis. The use of identical material properties in the four-point bending FE simulations of the femora reproduced not only the experimental values but also the statistical comparisons examining the effect of disease and treatment. Further efforts are needed to build upon the extraordinary legacy of John Currey and clarify the impact of different bone diseases on the hierarchical mechanical properties of bone.

Abundant osteoclasts in the subchondral bone of the juvenile Thoroughbred metacarpus suggest an important role in joint maturation

BACKGROUND

The administration of bisphosphonate medications, which target osteoclastic-bone remodelling, to juvenile and adult racehorses is a matter of debate owing to concerns that these molecules remain bound to the bone-mineralised matrix and may interfere with subsequent bone growth, adaptation to exercise and healing of bone microdamage in equine athletes. Osteoclasts participate in endochondral ossification, subchondral bone remodelling and bone repair. There is a knowledge gap on the role of equine osteoclast biology in the growth and maturation of joint surfaces and this information is important to inform judicious bisphosphonate use.

OBJECTIVES

Measure and compare the osteoclast density in the subchondral bone of Thoroughbred (TB) distal third metacarpi (McIII) at different sites, varying depths from the articular surface and with age (0-84 months).

STUDY DESIGN

Ex vivo cadaveric study.

METHODS

McIIIs from foals, yearlings and adults were collected, fixed in formaldehyde and stored at 4°C. Sections were cut from the lateral hemi-metacarpus, stained and scored for cartilage degeneration. Osteoclasts were counted on immunohistochemically (Cathepsin K) stained sections. Osteoclast density was compared in regions of interest (ROIs-the sagittal ridge, axial and abaxial condyle) and also at two depths (0-3 mm and 3-6 mm) into the subchondral bone below the osteochondral junction.

RESULTS

The osteoclast density was consistently highest in the subchondral cortical bone plate (0-3 mm) when compared with the deeper trabecular bone in all age groups. Furthermore, the osteoclast density was significantly higher in juvenile Thoroughbreds (foals and yearlings) within both sites in the subchondral bone when compared with adults.

MAIN LIMITATIONS

The number of specimens available for study was restricted.

CONCLUSIONS

Osteoclasts are important in normal McIII epiphyseal and articular surface maturation and have a propensity to localise at the osteochondral junction and subchondral cortical bone plate zone in juvenile Thoroughbreds.

Impact of fracture characteristics and disease-specific complications on health-related quality of life in osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a connective tissue disease with bone fragility. Several studies have indicated that physical function in adult OI was correlated to the disease severity, but there have been no reports delineating the impact of the fracture characteristics and disease-specific complications on health-related quality of life (HRQoL). The purpose of this study is to clarify the factors impacted on HRQoL in adult OI patients. We conducted a cross-sectional study between July 2016 and March 2018 and sent a questionnaire regarding HRQoL using Short Form-36 (SF-36) to the OI patients at the age of 20 years or older who had a medical history of the investigators' institutions. The 40 patients completely answered the SF-36. Mental component summary and role/social component summary were unremarkable. Physical component summary (PCS) was significantly associated with z-score for height, teeth abnormality, and cardiopulmonary insufficiency (partial regression coefficient, 3.04, - 9.70, and - 11.35; p, < 0.001, 0.047, and 0.025, respectively). PCS was also significantly lower in the patients who had an initial fracture before the age of 2 years than those without occurrence of fractures until 2 years old (25.80 ± 17.15 versus 44.20 ± 16.54; p = 0.002), or those who had lower extremity fractures more than five times as compared with normal populations. Physical function was decreased in OI patients who had fractures before 2 years old, especially in lower extremity. Appropriate medical managements for cardiopulmonary insufficiency are required not only to maintain physical function but also to decrease mortality.

Osteogenesis Imperfecta: Skeletal Outcomes After Bisphosphonate Discontinuation at Final Height

Intravenous cyclical bisphosphonates are widely used to treat children with moderate to severe osteogenesis imperfecta (OI). Bisphosphonates are often discontinued when growth is completed, but subsequent skeletal changes have not been studied in detail. We assessed 31 patients (22 females) with OI who had started intravenous bisphosphonates (either pamidronate or zoledronic acid) before 13 years of age, were treated for at least 2 years (range 4.7-15.7 years), and discontinued treatment after completion of growth, when their age ranged from 13.4 to 20.0 years (mean 16.4 years). At 4 years after treatment discontinuation, lumbar spine areal bone mineral density (BMD) had increased by 4% (p < 0.05). Peripheral quantitative computed tomography of the radius showed a decrease in trabecular volumetric BMD at the distal metaphysis of 19% but an increase in cortical volumetric BMD of 4% (p < 0.05 for both). None of the patients sustained a new vertebral compression fracture during follow-up. The proportion of patients with new long-bone fractures was higher in the 2 years before treatment discontinuation than in the last 2 years of follow-up (42% and 16%, respectively; p < 0.05). © 2019 American Society for Bone and Mineral Research.

Association between ribs shape and pulmonary function in patients with Osteogenesis Imperfecta

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Chest deformities in Osteogenesis Imperfecta patients affect pulmonary function.

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We present the rib cage deformities related to pulmonary function.

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There are significant relations between ribs shape and spirometric parameters.

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There is no relationship between thoracic spine shape and spirometric parameters.

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Correction of rib cage deformities will serve for better patients’ management.

The aim of the present study was to test the hypothesis that ribs shape changes in patients with OI are more relevant for respiratory function than thoracic spine shape. We used 3D geometric morphometrics to quantify rib cage morphology in OI patients and controls, and to investigate its relationship with forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1), expressed as absolute value and as percentage of predicted value (% pred). Regression analyses on the full sample showed a significant relation between rib shape and FEV1, FVC and FVC % pred whereas thoracic spine shape was not related to any parameter. Subsequent regression analyses on OI patients confirmed significant relations between dynamic lung volumes and rib shape changes. Lower FVC and FEV1 values are identified in OI patients that present more horizontally aligned ribs, a greater antero-posterior depth due to extreme transverse curve at rib angles and a strong spine invagination, greater asymmetry, and a vertically short, thoraco-lumbar spine, which is relatively straight in at levels 1–8 and shows a marked kyphosis in the thoraco-lumbar transition. Our research seems to support that ribs shape is more relevant for ventilator mechanics in OI patients than the spine shape.

Effects of zoledronic acid on vertebral shape of children and adolescents with osteogenesis imperfecta

Vertebral compression fracture (VCF) is a common and severe complication of osteogenesis imperfecta (OI). We prospectively observe the changes of vertebral shape during zoledronic acid (ZOL) treatment and assess influence factors of VCF in OI children. 32 children with VCF and 10 children without VCF (NVCF) were included and given ZOL treatment for 2 years, who were matched in age and gender. Control group included 17 treatment naïve OI patients with VCF who were matched in age, gender and clinical severity to 17 patients in VCF group received ZOL treatment for 1 year (as ZOL treated group). We performed quantitative vertebral morphometry and calculated concavity index (mh/ph), height-length ratio (ah/LL, mh/LL, ph/LL) and projection area (PA) of vertebrae from T4 to L4 before and after treatment. At baseline, patients in VCF group had significantly lower PA, mh/ph, ah/LL, mh/LL and ph/LL than patients in NVCF group (P < 0.01). PA, mh/ph, ah/LL, mh/ LL and ph/LL of patients with VCF were raised by (35.2 ± 19.5)%, (22.9 ± 15.1)%, (19.6 ± 13.9)%, (33.6 ± 25.5)%, and (8.1 ± 8.8)% (P < 0.01) after 1-year treatment of ZOL, and were increased by (71.8 ± 28.2)%, (42.8 ± 21.8)%, (35.1 ± 20.6)%, (65.4 ± 43.2)%, and (12.5 ± 11.4)% after 2-year treatment of ZOL (P < 0.01). Compared to control group, mh/ph, ah/LL and mh/LL were significantly higher (P < 0.01) in ZOL treated group. LS-BMD and its increase were positively correlated to vertebral height and PA at baseline and the improvement of vertebral height and PA after ZOL treatment, respectively. In conclusion, the compressive vertebrae of OI children could be effectively reshaped during ZOL treatment. Low LS-BMD was an independent risk factor for VCF and its increase was positively correlated to the improvement in vertebral shape after ZOL treatment.

Cyclic pamidronate treatment for osteogenesis imperfecta: Report from a Brazilian reference center

Treatment of moderate and severe forms of osteogenesis imperfecta (OI) with cyclic pamidronate at the Reference Center for OI Treatment in Southern Brazil was studied. A retrospective cohort study was conducted from 2002 to 2012. Data were obtained during inpatient (drug infusion) and outpatient care. Clinical data, including the presence of blue sclerae, dentinogenesis imperfecta, history and site of the fractures, biochemical data, including calcium, phosphorus, and alkaline phosphatase levels, were systematically collected. Bone mineral density (BMD) was measured using dual energy X-ray absorptiometry (DXA). Forty-five patients (26 females) were included in the study, and the age of the patients at the time of diagnosis ranged from 1 to 144 months, with a median age (p25-p75) of 38 (5-96) months. Most cases presented OI-4 (51.1%), and the median age of the patients at the start of treatment was 3.3 years (25-75 percentiles: 0.5 - 8.7 years). Twenty-four patients (54.5%) had some adverse events or intercurrences during treatment, and the treatment compliance mean was 92.3% (± 10.7). The treatment with intravenous pamidronate has shown to be safe, well-tolerated, and effective in regard to the improvement of BMD and the reduction of the number of fractures in children and adolescents with OI.