Update on the evaluation and treatment of osteogenesis imperfecta

Effects of shear stress on mesenchymal stem cells of patients with osteogenesis imperfecta

INTRODUCTION

Osteogenesis imperfecta (OI) is a rare genetic bone disorder, mainly caused by autosomal dominant mutations of the COL1A1 or COL1A2 genes that encode the alpha chains of type 1 collagen. In severe forms and in nonambulatory patients, for whom physical exercise is difficult, exposing the bone to mechanical stimuli by promoting movement, especially with physiotherapy and mobility aids, is an essential part of clinical practice. However, the effects of mechanical stimulation at the cellular level remain unknown for this disease.

HYPOTHESIS

The study hypothesis was that human mesenchymal stem cells (hMSCs) from patients with OI were as sensitive to mechanical stimulation as those from healthy patients, validating the current clinical practice.

MATERIALS AND METHODS

hMSCs were harvested from 3 healthy control subjects and 3 patients with OI during an elective osteotomy of a long bone of the lower limb. The healthy and OI hMSCs were then exposed to mechanical stimuli, such as intermittent shear stress of 0, 0.7, 1.5, and 3 Pascal (Pa) at a frequency of 2.8 Hertz (Hz) for 30 minutes using a commercial ibidi system. The immediate early gene expression of themechanosensitive prostaglandin-endoperoxide synthase 2 (PTGS2) was examined 1 hour after stimulation to determine the best level of mechanical stimulation. The expression of 7 other mechanosensitive genes was also examined for this level of mechanical stimulation after applying intermittent shear stress at 1.5 Pa.

RESULTS

In all hMSCs, mechanical stimulation induced PTGS2 gene overexpression with a maximum after exposure to intermittent shear stress of 1.5 Pa and without significant differences between OI and healthy donors. Except for fibroblast growth factor 2, gene expression in OI donors was found to be significantly different from that in hMSCs not exposed to shear stress. Moreover, the relative expression associated with mechanical stimulation was not significantly different between healthy and OI donors for most other genes.

DISCUSSION

This is the first study to demonstrate that hMSCs from patients with OI are as sensitive to mechanical shear stress as those from healthy donors. The mechanical stress that resulted in the greatest change in the expression of PTGS2 in patients with OI was similar to that previously reported in the literature for healthy subjects. These findings are an important step toward further fundamental research aimed at confirming the effects of mechanical stress at the cellular level over the long term and, more importantly, toward developing clinical protocols for delivering mechanical stimuli to these patients.

LEVEL OF EVIDENCE

III; comparative case-control study.

Demographics and medical burden of osteogenesis imperfecta: a nationwide database analysis

The epidemiological data on osteogenesis imperfecta (OI) in Asia is limited. This study, representing the first comprehensive epidemiological investigation on OI in Taiwan, reveals high medical resource utilization and underscores the importance of early diagnosis to enhance care quality.

INTRODUCTION

This study examines osteogenesis imperfecta, a hereditary connective tissue disorder causing pediatric fractures and limb deformities, using a nationwide database from Taiwan to analyze clinical features and medical burden.

METHODS

The study identified validated OI patients from the Catastrophic Illness Registry in the National Health Insurance Research Database from 2008 to 2019. Demographic data and medical resource utilization were analyzed. A multivariate Cox model assessed the influence of sex, validation age, and comorbidities.

RESULTS

319 OI patients (M/F = 153/166) were identified, with 58% validated before age 20. Prevalence and incidence were 0.8-1.3/100,000 and 0.02-0.09/100,000, respectively, with higher rates in the pediatric demographic. In the study period, 69.6% of the patients had admission history, primarily to pediatric and orthopedic wards. The median admission number was 3, with a median length of stay of 12 days and a median inpatient cost of approximately 3,163 USD during the period. Lower limb fractures were the main reason for hospitalization. 57% of OI patients received bisphosphonate treatment. The leading causes of mortality were OI-related deaths, neurovascular disease, and cardiovascular disease. The median age of validation in the non-survival group was significantly higher compared to the survival group (33 vs. 14 years), and patients validated during childhood required more inpatient fracture surgeries than those validated during adulthood.

CONCLUSION

This study provides comprehensive real-world evidence on the clinical characteristics and high medical resource utilization of OI patients in a low prevalence region like Taiwan. Early diagnosis is crucial for improving care quality and enhancing health outcomes.

Emerging Landscape of Osteogenesis Imperfecta Pathogenesis and Therapeutic Approaches

Osteogenesis imperfecta (OI) is an uncommon genetic disorder characterized by shortness of stature, hearing loss, poor bone mass, recurrent fractures, and skeletal abnormalities. Pathogenic variations have been found in over 20 distinct genes that are involved in the pathophysiology of OI, contributing to the disorder's clinical and genetic variability. Although medications, surgical procedures, and other interventions can partially alleviate certain symptoms, there is still no known cure for OI. In this Review, we provide a comprehensive overview of genetic pathogenesis, existing treatment modalities, and new developments in biotechnologies such as gene editing, stem cell reprogramming, functional differentiation, and transplantation for potential future OI therapy.

The recombinant BMP-2 loaded silk fibroin microspheres improved the bone phenotype of mild osteogenesis imperfecta mice

Osteogenesis imperfecta (OI) is an inherited congenital disorder, characterized primarily by decreased bone mass and increased bone fragility. Bone morphogenetic protein-2 (BMP-2) is a potent cytokine capable of stimulating bone formation, however, its rapid degradation and unanticipated in vivo effects restrict its application. The sustained release characteristic of silk fibroin (SF) microspheres may potentially address the aforementioned challenges, nevertheless they have not previously been tested in OI treatment. In the current investigation, recombinant BMP-2 (rBMP-2) loaded SF (rBMP-2/SF) microspheres-based release carriers were prepared by physical adsorption. The SF microparticles were characterized by scanning electron microscopy (SEM) and were investigated for their cytotoxicity behavior as well as the release profile of rBMP-2. The rBMP-2/SF microspheres were administered via femoral intramedullary injection to two genotypes of OI-modeled mice daily for two weeks. The femoral microstructure and histological performance of OI mice were evaluated 2 weeks later. The findings suggested that rBMP-2/SF spheres with a rough surface and excellent cytocompatibility demonstrated an initial rapid release within the first three days (22.15 ± 2.88% of the loaded factor), followed by a transition to a slower and more consistent release rate, that persisted until the 15th day in an in vitro setting. The factor released from rBMP-2/SF particles exhibited favorable osteoinductive activity. Infusion of rBMP-2/SF microspheres, as opposed to blank SF spheres or rBMP-2 monotherapy, resulted in a noteworthy enhancement of femoral microstructure and promoted bone formation in OI-modeled mice. This research may offer a new therapeutic approach and insight into the management of OI. However, further investigation is required to determine the systematic safety and efficacy of rBMP-2/SF microspheres therapy for OI.

Acetabular fracture and central hip dislocation in osteogenesis imperfecta child treated surgically with bone grafts augmented by recombinant human bone morphogenetic protein-2: A rare case report

INTRODUCTION AND IMPORTANCE

Rare congenital disorder osteogenesis imperfecta (OI) can make treating complex acetabular fractures-dislocations challenging. Open reduction and internal fixation (ORIF) with locking plates and screws may not produce satisfactory results. We present the outcome of ORIF with reconstruction locking plate and screw augmented by bone grafts with recombinant bone morphogenetic protein-2 (rhBMP-2) for OI type I child with Judet-Letournel both column type acetabular fracture associated with central hip dislocation.

CASE PRESENTATION

We present a case of a 13-year-old female OI type I patient with right hip pain after falling while biking. Both eyes had blue sclera and OI family history. Intraoperatively, the Stoppa approach was used. Proximal femoral skeletal traction was used to reduce the femoral head and aid bone graft reconstruction of the acetabular wall. Intraosseous injection of rhBMP-2 was added. Fractures were fixed with a curved reconstruction locking plate and screws. Bones and soft tissues were gently manipulated to prevent blood loss. Radiographic and functional results were remarkable.

CLINICAL DISCUSSION

Fractures and blood loss are more likely to occur in OI type I patients due to collagen type I deficiency. Proximal femur skeletal traction is crucial for ORIF plating in acetabular fractures with central hip dislocation. This minimizes bone and soft tissue manipulation. RhBMP-2-injected bone grafts have structural support and osteoinductive properties that enhance bone healing. Despite its exceptional results in this case, further research is needed.

CONCLUSION

The combination of our technique and rhBMP-2 effectively accelerates bone healing in OI patient treated with ORIF.

Mesenchymal stem cells in the treatment of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a disease caused by mutations in different genes resulting in mild, severe, or lethal forms. With no cure, researchers have investigated the use of cell therapy to correct the underlying molecular defects of OI. Mesenchymal stem cells (MSCs) are of particular interest because of their differentiation capacity, immunomodulatory effects, and their ability to migrate to sites of damage. MSCs can be isolated from different sources, expanded in culture, and have been shown to be safe in numerous clinical applications. This review summarizes the preclinical and clinical studies of MSCs in the treatment of OI. Altogether, the culmination of these studies show that MSCs from different sources: 1) are safe to use in the clinic, 2) migrate to fracture sites and growth sites in bone, 3) engraft in low levels, 4) improve clinical outcome but have a transient effect, 5) have a therapeutic effect most likely due to paracrine mechanisms, and 6) have a reduced therapeutic potential when isolated from patients with OI.

Does the Skeletal Phenotype of Osteogenesis Imperfecta Differ for Patients With Non-COL1A1/2 Mutations? A Retrospective Study in 113 Patients

BACKGROUND

Osteogenesis imperfecta (OI) is a heritable disease characterized by bone fragility and other extra skeletal manifestations. Most patients with OI have mutations in the COL1A1 or COL1A2 genes. However, a significant minority of patients with clinical OI have non-COL1A1/2 mutations, which have become easier to detect with the use of genetic panels. Traditional understanding of OI pathogenesis was expanded because of these new mutations, and their phenotypic-genotypic relationship is largely unknown. We hypothesized that patients with non-COL1A1/2 mutations have different skeletal clinical presentations from those with OI caused by COL1A1/2 mutations.

METHODS

Patients were categorized into 4 groups according to our modified functional classification, namely, quantitative COL1A1/2 haploinsufficiency (group 1), qualitative COL1A1/2 dominant negative mutations (group 2), mutations indirectly affecting type I collagen synthesis, processing and posttranslational modification (group 3) and mutations altering osteoblast differentiation and function (group 4). Both group 3 and 4 were classified as non-COL1A1/2 mutation group.

RESULTS

Of 113 OI patients included, 51 had COL1A1/2 quantitative haploinsufficiency mutations (group 1), 39 had COL1A1/2 qualitative dominant negative mutations (group 2), and 23 patients had OI caused by mutations in 1 of 9 other noncollagen genes (groups 3/4). Patients with non-COL1A1/2 mutations (groups 3 and 4) have severe skeletal presentations. Specifically, OI patients with non-COL1A1/2 mutations experienced more perinatal fractures, vertebral compression fractures and had more long bone deformities. Although the occurrence of scoliosis was similar, the cobb angle was larger in the non-COL1A1/2 mutation group. Radial head dislocations, ossification of interosseous membrane, extraskeletal ossification, cervical kyphosis, and champagne glass deformity of the pelvis were more frequent in this group.

CONCLUSIONS

The clinical phenotype of OI in patients with non-COL1A1/2 is severe and has unique features. This information is useful for clinical diagnosis and prognosis.

LEVEL OF EVIDENCE

Level III.

Bone Fractures Numerical Analysis in a Femur Affected by Osteogenesis Imperfecta

This work presents a non-invasive methodology to obtain a three-dimensional femur model of three-year-old infants affected with Osteogenesis Imperfecta (OI) type III. DICOM^® Files of a femur were processed to obtain a finite element model to assess the transverse, the oblique, and the comminuted fractures. The model is evaluated under a normal walking cycle. The loads applied were considered the most critical force generated on the normal walking cycle, and the analyses considered anisotropic bone conditions. The outcome shows stress concentration areas in the central zone of the diaphysis of the femur, and the highest levels of stress occur in the case of the comminuted fracture, while the transverse fracture presents the lowest values. Thus, the method can be helpful for determining the bone fracture behavior of certain pathologies, such as osteogenesis imperfecta, osteopenia, and osteoporosis.

Infrequent association of two rare diseases: amniotic band syndrome and osteogenesis imperfecta

Objectives

Amniotic band syndrome and osteogenesis imperfecta are two distinct diseases that develop due to structural defects of the collagen protein. In our paper, we report the concurrence of these two diseases rarely seen in the newborn period.

Case presentation

A female infant born at 33rd gestational week was found to have constrictive bands in her right lower extremity and flexion contractures in distal joints of lower and upper extremities due to amniotic bands in postnatal physical examination. While being treated for respiratory difficulty, she was diagnosed with osteogenesis imperfecta and treated with bisphosphonates upon being found to suffer bilateral humeral fractures on the sixth day of life. She received respiratory support with mechanical ventilation due to respiratory tract complications related to osteogenesis imperfecta and died on the 384th day of life.

Conclusions

One should bear in mind that other collagen tissue diseases may accompany the amniotic band syndrome; this possibility should be definitely pursued if clinical suspicion exists.

Metabolic Bone Diseases in the Pediatric Population

Bone plays an important role in regulating mineral balance in response to physiologic needs. In addition, bone is subject to a continuous remodeling process to maintain healthy bone mass and growth. Metabolic bone diseases are a heterogeneous group of diseases caused by abnormalities of bone mass, mineral structure homeostasis, bone turnover, or bone growth. In pediatrics, several significant advances have been made in recent years in the diagnosis of metabolic bone diseases (e.g., osteogenesis imperfecta, hyperparathyroidism, rickets, renal osteodystrophy, pediatric osteoporosis, and osteopetrosis). Imaging is fundamental in the diagnosis of these pathologies.

Impact of Intrinsic Muscle Weakness on Muscle-Bone Crosstalk in Osteogenesis Imperfecta

Bone and muscle are highly synergistic tissues that communicate extensively via mechanotransduction and biochemical signaling. Osteogenesis imperfecta (OI) is a heritable connective tissue disorder of severe bone fragility and recently recognized skeletal muscle weakness. The presence of impaired bone and muscle in OI leads to a continuous cycle of altered muscle-bone crosstalk with weak muscles further compromising bone and vice versa. Currently, there is no cure for OI and understanding the pathogenesis of the skeletal muscle weakness in relation to the bone pathogenesis of OI in light of the critical role of muscle-bone crosstalk is essential to developing and identifying novel therapeutic targets and strategies for OI. This review will highlight how impaired skeletal muscle function contributes to the pathophysiology of OI and how this phenomenon further perpetuates bone fragility.

'In-Out-In' K-wires sliding in severe tibial deformities of osteogenesis imperfecta: a technical note

Severe infant osteogenesis imperfecta requires osteosynthesis. Intramedullary tibia's osteosynthesis is a technical challenge given the deformity and the medullar canal's narrowness. We describe an extramedullary technique: 'In-Out-In' K-wires sliding. We performed an anteromedial diaphysis approach. The periosteum was released while preserving its posterior vascular attachments. To obtain a straight leg, we did numerous osteotomies as many times as necessary. K-wires ('In') were introduced into the proximal epiphysis, and the medial malleolus ('Out') bordered the cortical and ('In') reach their opposite metaphysis. K-wires were cut, curved and impacted at their respective epiphysis ends to allow a telescopic effect. All tibial fragments are strapped on K-wires, and the periosteum was sutured over it. Our inclusion criteria were children with osteogenesis imperfecta operated before 6 years old whose verticalization was impossible. Seven patients (11 tibias) are included (2006-2016) with a mean surgery's age of 3.3 ± 1.1 years old. All patients received intravenous bisphosphonates preoperatively. The follow-up was 6.1 ± 2.7 years. All patients could stand up with supports, and the flexion deformity correction was 46.7 ± 14.2°. Osteosynthesis was changed in nine tibias for the arrest of telescoping with flexion deformity recurrence and meantime first session-revision was 3.8 ± 1.7 years. At revision, K-wires overlap had decreased by 55 ± 23%. Including all surgeries, three distal K-wires migrations were observed, and the number of surgical procedures was 2.5/tibia. No growth arrest and other complications reported. 'In-Out-In' K-wires sliding can be considered in select cases where the absence of a medullary canal prevents the insertion of intramedullary rod or as a salvage or alternative procedure mode of fixation. It can perform in severe infant osteogenesis imperfecta under 6 years old with few complications and good survival time.

Osteogenesis Imperfecta in neonatal period in Cameroon: A case report

Early forms of Osteogenesis Imperfecta should be considered as main etiology of bone deformities in newborns. Prenatal diagnosis and genetic counseling should be improved in Africa. Management of these children remains difficult in low-income countries.

New 3D Cone Beam CT Imaging Parameters to Assist the Dentist in Treating Patients with Osteogenesis Imperfecta

(1) Background: The aim of the work is to identify some imaging parameters in osteogenesis imperfecta to assist the dentist in the diagnosis, planning, and orthodontic treatment of Osteogenesis Imperfecta (OI) using 3D cone beam Computed Tomography (CBCT) and the Double Energy X-ray Absorptiometry (DEXA) technique. (2) Methods: 14 patients (9 males and 5 females; aged mean ± SD 15 ± 1.5) with a clinical-radiological diagnosis of OI were analyzed and divided into mild and moderate to severe forms. The patients' samples were compared with a control group of 14 patients (8 males and 6 females; aged mean ± SD 15 ± 1.7), free from osteoporotic pathologies. (3) Results: The statistical analysis allowed us to collect four datasets: in the first dataset (C1 sick population vs. C1 healthy population), the t-test showed a p-value < 0.0001; in the second dataset (C2 sick population vs. C2 healthy population), the t-test showed a p-value < 0.0001; in the third dataset (parameter X of the sick population vs. parameter X of the healthy population), the t-test showed a p-value < 0.0001; in the fourth dataset the bone mineralometry (BMD) value detected by the DEXA technique compared to the C2 value of the OI affected population only) the Welch-Satterthwaite test showed a p-value < 0.0001. (4) Conclusions: The research has produced specific imaging parameters that assist the dentist in making diagnostic decisions in OI patients. This study shows that patients with OI have a characteristic chin-bearing symphysis, thinned, and narrowed towards the center, configuring it with a constant "hourglass" appearance, not reported so far in the literature by any author.

Perioperative Considerations in Osteogenesis Imperfecta: A 20-Year Experience with the Use of Blood Pressure Cuffs, Arterial Lines, and Tourniquets

Osteogenesis imperfecta (OI) is a rare genetic connective-tissue disorder with bone fragility. To avoid iatrogenic fractures, healthcare providers have traditionally avoided using non-invasive blood pressure (NIBP) cuffs and extremity tourniquets in the OI population in the perioperative setting. Here, we hypothesize that these procedures do not lead to iatrogenic fractures or other complications in patients with OI. A retrospective study of all children with OI who underwent surgery at a single tertiary care children’s hospital from 1998 to 2018 was performed. Patient positioning and the use of NIBP cuffs, arterial lines, and extremity tourniquets were documented. Fractures and other complications were recorded. Forty-nine patients with a median age of 7.9 years (range: 0.2–17.7) were identified. These patients underwent 273 procedures, of which 229 were orthopaedic operations. A total of 246 (90.1%) procedures included the use of an NIBP cuff, 61 (22.3%) an extremity tourniquet, and 40 (14.7%) an arterial line. Pediatric patients with OI did not experience any iatrogenic fractures related to hemodynamic monitoring or extremity tourniquet use during the 20-year period of this study. Given the benefits of continuous intra-operative hemodynamic monitoring and extremity tourniquets, we recommend that NIBP cuffs, arterial lines, and tourniquets be selectively considered for use in children with OI.

Therapeutic Dimensions of Bisphosphonates: A Clinical Update

Bisphosphonates (BPs) are a commonly used class of drugs for the treatment of bone disorders. An extensive review of BPs with their clinical efficacy and safety profile is unavailable. This study aimed to review the available literature on BPs, summarize their role in clinical therapy, and emphasize their safety profile. Authors reviewed the existing literature using the Google Scholar, PubMed, and Micromedex databases and analyzed the collected articles. BPs are the preferred medication for osteoporosis and other similar conditions owing to their efficient antiosteoclastic activity. Few of them are available in oral dosage forms; hence, they are patient-friendly. The mechanism of action, common adverse effects and their clinical applications, precautions and warnings pertaining to the route of administration, and safety profiles have been discussed in this manuscript. The common adverse effects are majorly related to the gastrointestinal, cardiovascular, and endocrine system. Upon chronic usage, patients may experience serious problems like osteonecrosis of the jaw and atypical bone fractures. Although BPs are effective and safe, they may cause GI adverse effects and rare cases of osteonecrosis. Patient counseling could prove beneficial in early identification and prevention of the adverse effects associated with BPs.

Craniofacial allometry in the OIM-/- mouse model of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a skeletal disorder characterized by the impaired synthesis of type I collagen (Col1). This study tests the hypothesis that the craniofacial phenotype of severe OI is linked to an overall reduction in body size. 3D landmark data were collected from µCT scans of adult OIM^-/- and wild-type (WT) mice and used to calculate centroid sizes (CS) and interlandmark distances (ILDs). To remove the effect of body size, ILDs were scaled against craniomandibular lengths and CS. Mann-Whitney U tests were used to compare CS and absolute/scaled ILDs between genotypes. OIM^-/- mice are smaller than their WT littermates in body mass, craniomandibular CS, and absolute ILDs including skull, basicranial, palatal, mandibular, and toothrow lengths. When linear distances are scaled to CS, OIM^-/- mice have a relatively short midface, short nasal bones, tall mandibular corpora, and long mandibular toothrows. Results underscore the importance of size and scaling in morphometric analyses. The deleterious effect of Col1 mutations on global skeletal dimensions combined with localized morphometric changes may underlie the facial phenotype seen in human patients with severe OI. Attempts to identify these localized changes should first account for the restricted growth and small body sizes present in individuals with OI.

Hybrid minigene splicing assay verifies the pathogenicity of a novel splice site variant in the COL1A1 gene of a chinese patient with osteogenesis imperfecta type I

BACKGROUND

Osteogenesis imperfecta (OI) is a rare genetic bone disease associated with brittle bones and fractures. Among all known types, OI type I is the most common type and characterized by increased bone fragility, low bone mass, distinctly blue-gray sclera, and susceptibility to conductive hearing loss beginning in adolescence. Mutations in genes encoding type I collagen (COL1A1 and COL1A2) contribute to the main pathogenic mechanism of OI.

METHODS

Subtle mutation of the COL1A1 gene in the proband was detected by targeted next-generation sequencing (NGS) and confirmed by Sanger sequencing. We then assessed the effect of the mutation on the splicing of the COL1A1 gene by bioinformatics prediction and hybrid minigene splicing assay (HMSA).

RESULTS

A novel splice site mutation c.1821+1 G>C was discovered in the proband by NGS and further confirmed by Sanger sequencing, which was also simultaneously identified from the proband's mother and elder sister. Bioinformatics predicted that this mutation would result in a disappearance of the 5' donor splice site in intron 26, thereby leading to abnormal splicing and generation of premature stop codon. The follow-up experimental data generated by HMSA was consistent with this prediction.

CONCLUSION

Our study identified a novel splice site mutation that caused OI type I in the proband by abnormal splicing and demonstrated that combined applications of NGS, bioinformatics and HMSA are comprehensive and effective methods for diagnosis and aberrant splicing study of OI.

Surgical Treatment of Bilateral Tibia Deformity in a 9-Year-Old Child Suffering from Osteogenesis Imperfecta Type III: A Case Report

Patient: Male, 9

Final Diagnosis: Osteogenesis imperfecta type III

Symptoms: Walking difficulties

Medication: —

Clinical Procedure: Osteotomies and realignment of bone deformity

Specialty: Orthopedics and Traumatology

Management of Catastrophic Proximal Junctional Failure Following Spinal Deformity Correction in an Adult with Osteogenesis Imperfecta: Case Report and Technical Note

BACKGROUND

Proximal junctional failure (PJF) is a major and sometimes devastating problem following adult spinal deformity (ASD) correction surgery. Common consensus still lags on guidelines for preventing and managing these complications. Surgical treatment of scoliosis in the presence of osteogenesis imperfecta (OI) in the pediatric population is well described. The complication rates are unusually higher in this special subset of patients owing to poor quality of bone. There is a paucity of literature focusing on surgical techniques, strategies, and problems involved in the management of ASD associated with OI.

CASE DESCRIPTION

We report a 59-year-old female with type 1 OI and adult scoliosis who underwent T10-to-pelvis fusion for ASD according to the principles of adult deformity correction. At a 1-year follow-up, she presented with asymptomatic proximal junctional kyphosis of 45° and 2 weeks later had PJF along with spinal cord injury after a fall. On computed tomography scan, kyphosis was increased to 60° at T9-T10. She underwent decompression and revision deformity correction using quadruple rods, with extension of instrumentation to T2 with soft landing using rib bands. At a 4-year follow-up, she had a good functional outcome after revision surgery.

CONCLUSIONS

This is the first report of successful management of PJF following ASD correction in the presence of OI using this technique. Suboptimal hold of implants due to poor bone quality must be at the focus of any surgical planning for these patients. All possible strategies to prevent PJF must be considered when planning the deformity correction in adults with OI.

Results of stapedotomy in otosurgical treatment of adult patients with osteogenesis imperfecta

OBJECTIVE

This is a retrospective study of hearing results and characteristics of osteogenesis imperfecta (OI) patients treated for hearing loss by stapedotomy at tertiary reference center.

METHODS

This study enrolled 20 patients with a clinical diagnosis of OI- (11M:9F). 18 patients (90%) underwent surgery due to hearing loss in the period 2003-16. The audiometric analysis provides the pure tone audiometry results of stapedotomy in adult patients in 2 periods (≤12 months and >12 months). Air-bone gap (ABG), hearing gain (HG), and changes in air and bone conduction thresholds after surgical treatment were analyzed.

RESULTS

In short-time follow-up we noted statistically significant improvement in mean AC thresholds and ABG (p < 0.001 for both), change in mean BC thresholds was statistically negligible. Comparing the observation periods short-term and long-term, it was found that AC thresholds, ABG, HG, ABG closure did not significantly change, although BC thresholds and BC closure deteriorated significantly (p < 0.05).

CONCLUSION

Stapes surgery for OI can be considered as a method of treating the conductive and/or mixed hearing loss suffered by these patients; however, the surgery is more difficult than that for otosclerosis because OI cases often have extremely difficult anatomical conditions. The hearing results of OI stapes surgery differ from typical otosclerosis cases, with the ABG closure not being as good. In addition, sensorineural hearing loss inevitably progresses.

Treatment of tibial deformities with the Fassier-Duval telescopic nail and minimally invasive percutaneous osteotomies in patients with osteogenesis imperfecta type III

Osteogenesis imperfecta (OI) is a rare congenital osteodystrophy. Patients with OI present with osteoporosis, extreme bone fragility and severe deformities of the lower limbs, which predispose them to frequent fractures. The aim of our study is to describe the minimally invasive osteotomy technique to correct the tibial deformities in patients with OI type III, using the Fassier-Duval (FD) intramedullary nailing, which is considered the gold standard in this kind of surgery. We analyzed the results obtained from 14 patients with OI type III, treated for tibial deformities with the minimally invasive percutaneous osteotomy technique and osteosynthesis with the FD telescopic nail. The results were compared with that of a control group composed of 18 patients with OI type III, treated for tibial deformities with open technique osteotomies and osteosynthesis with FD telescopic nail. The follow-up was set at 18 months postoperatively. The data concerning the following were collected from the two groups: duration of surgery, number of osteotomies performed, postoperative pain, time required for functional recovery, and for the formation of bone callus. To analyze the variations in the quality of life, all the patients were given the Pediatric Outcomes Data Collection Instrument questionnaire, before surgery and at the end of the follow-up. In patients who underwent corrective surgery with the percutaneous technique, the average duration of surgery was inferior, the postoperative pain was significantly lower, the recovery of 90° range of motion of knee flexion was reached at an average of 37.8 days, and they ambulated bearing full weight on the leg without auxiliary aids on average 45 days after surgery. The Pediatric Outcomes Data Collection Instrument questionnaire values were satisfactory in both groups. The osteosynthesis with the FD telescopic nail, performed with the minimally invasive surgical technique, has improved the management of deformities in OI. The minimally invasive technique, however, requires the maturation of three distinct learning curves: surgery on patients with OI, open technique with the FD nail, and percutaneous technique with the FD nail.

Pharmacological resources, diagnostic approach and coordination of care in joint hypermobility-related disorders

INTRODUCTION

Joint hypermobility (JH) is the hallmark of many hereditary soft connective tissue disorders, including Ehlers-Danlos syndromes and related disorders, disorders of the TGFβ-pathway, lateral meningocele syndrome, arterial tortuosity syndrome, and cutis laxa syndromes. Contemporary practice separates individuals with isolated, non-syndromic JH from patients with Mendelian syndromes and those with hypermobility spectrum disorders. The latter is a new nosologic entity grouping together individuals with JH and related musculoskeletal manifestations, but lacking inclusion criteria for well-defined and/or single-gene disorders. Area covered: Nomenclature of JH and JH-related disorders are summarized on a practically oriented perspective. Critical areas of clinical management comprise pain; cardiovascular and respiratory issues; fatigue and dysautonomia; bone fragility; and capillary, skin and soft tissue fragility. Medical management stands on low-evidence data. Ongoing preclinical and clinical studies are aimed to reach a more personalized pharmacological approach to the management of the cardiovascular risk, musculoskeletal pain, and reduced bone mass. Expert commentary: Correct classification of patients with JH-related disorders needs a systematic approach, in which a wide array of molecular tests should be intermingled with strong clinical competences in highly specialized settings. A multispecialty, hierarchical approach should be encouraged for optimal coordination of care in systemic phenotypes.

Pain and quality of life of children and adolescents with osteogenesis imperfecta over a bisphosphonate treatment cycle

The objective was to describe the pain and quality of life among children and adolescents with any osteogenesis imperfecta (OI) type over one intravenous bisphosphonate treatment cycle from a child and parental perspective. A prospective, observational study was conducted, where children and adolescents evaluated their pain intensity, location, and quality, as well as quality of life before, 1 week after treatment, and 6 months later. Quality of life was also evaluated from the parental perspective at the same three time points. Thirty-three child/parent dyads participated. The results showed that pain intensity on the 0-10 self-report scale after the Zoledronate infusion (median = 0, range = 0-6) was not different from pre (median = 2, range = 0-10) and 6-months post-scores (median = 2, range = 0-8) (p = 0.170). Children and adolescents with OI reported experiencing pain mainly in the ankles and the anterior and posterior shoulders. They selected evaluative pain descriptors such as uncomfortable (n = 16, 48%) and annoying (n = 13, 39%). Children and adolescents' functioning and quality of life did not change significantly across the bisphosphonate treatment cycle (p = 0.326), parents perceived an improvement immediately after the treatment compared to before (p = 0.016).

CONCLUSION

Children and adolescents with OI experience mild, yet complex pain localized across several body areas. There is little fluctuation in the pain intensity and functioning of children with OI undergoing bisphosphonate treatment. What is Known: • Acute and chronic musculoskeletal pain remains a major issue in OI. • Pain has a negative impact on quality of life. What is New: • New and unpublished methods and findings describing the pain and quality of life of children and adolescents with OI over one intravenous bisphosphonate treatment cycle from a child- and parental-proxy perspective. • Children and adolescents with OI experience pain intensity that is mild, yet complex in quality and localized across several body areas.

Multiscale modeling of keratin, collagen, elastin and related human diseases: Perspectives from atomistic to coarse-grained molecular dynamics simulations

Scleroproteins are an important category of proteins within the human body that adopt filamentous, elongated conformations in contrast with typical globular proteins. These include keratin, collagen, and elastin, which often serve a common mechanical function in structural support of cells and tissues. Genetic mutations alter these proteins, disrupting their functions and causing diseases. Computational characterization of these mutations has proven to be extremely valuable in identifying the intricate structure-function relationships of scleroproteins from the molecular scale up, especially if combined with multiscale experimental analysis and the synthesis of model proteins to test specific structure-function relationships. In this work, we review numerous critical diseases that are related to keratin, collagen, and elastin, and through several case studies, we propose ways of extensively utilizing multiscale modeling, from atomistic to coarse-grained molecular dynamics simulations, to uncover the molecular origins for some of these diseases and to aid in the development of novel cures and therapies. As case studies, we examine the effects of the genetic disease Epidermolytic Hyperkeratosis (EHK) on the structure and aggregation of keratins 1 and 10; we propose models to understand the diseases of Osteogenesis Imperfecta (OI) and Alport syndrome (AS) that affect the mechanical and aggregation properties of collagen; and we develop atomistic molecular dynamics and elastic network models of elastin to determine the role of mutations in diseases such as Cutis Laxa and Supravalvular Aortic Stenosis on elastin's structure and molecular conformational motions and implications for assembly.

Effects of a telescopic intramedullary rod for treating patients with osteogenesis imperfecta of the femur

PURPOSE

To introduce a new model of telescopic intramedullary rod (TIR), evaluate its effects on treating patients presenting with moderate and severe osteogenesis imperfecta (OI) and to compare the findings with those of other telescopic rods.

METHODS

A total of 21 patients (nine girls and 12 boys; mean age at first operation, 6.6 years, 1.52 to 13.18) who underwent 52 femoral operations were monitored during a mean of 9.96 years (3.39 to 14.54). Patient characteristics, telescoping rod capability and its complications were examined.

RESULTS

According to the Sillence classification, we investigated one patient with type I, nine with type III and 11 with type IV OI. Revision rates at up to five years (36%) were inferior to those found for the Fassier-Duval rod (46%). The main cause of revision was fracture (15 patients), followed by rod migration (nine), and infection (two). The rod exhibited higher telescopic capacity in boys than girls. Type III most commonly required an operation; the age group with the highest number of procedures was five to ten years. Male migration was the main cause of rod migration.

CONCLUSION

The TIR has a satisfactory cost-benefit ratio with less complication rates and low production costs. The TIR is a feasible alternative to the commonly used Fassier-Duval rod.

LEVEL OF EVIDENCE

IV.

Osteogenesis Imperfecta

Osteogenesis imperfecta is a common heritable connective tissue disorder. Nearly ninety percent are due to Type I collagen mutations. Type I-IV are autosomal dominant, and Type VI-XIII are autosomal recessive. They are Graded 1-5 based on severity. Genomic testing is done by collagen analysis from fibroblasts. The mainstay of treatment is bisphosphonate therapy. The prognosis is variable.

Confirmation of the pathogenicity of a mutation p.G337C in the COL1A2 gene associated with osteogenesis imperfecta

Mutation analysis as the gold standard is particularly important in diagnosis of osteogenesis imperfecta (OI) and it may be preventable upon early diagnosis. In this study, we aimed to analyze the clinical and genetic materials of an OI pedigree as well as to confirm the deleterious property of the mutation.A pedigree with OI was identified. All family members received careful clinical examinations and blood was drawn for genetic analyses. Genes implicated in OI were screened for mutation. The function and structure of the mutant protein were predicted using bioinformatics analysis.The proband, a 9-month fetus, showed abnormal sonographic images. Disproportionately short and triangular face with blue sclera was noticed at birth. She can barely walk and suffered multiple fractures till 2-year old. Her mother appeared small stature, frequent fractures, blue sclera, and deformity of extremities. A heterozygous missense mutation c.1009G>T (p.G337C) in the COL1A2 gene was identified in her mother and her. Bioinformatics analysis showed p.G337 was well-conserved among multiple species and the mutation probably changed the structure and damaged the function of collagen.We suggest that the mutation p.G337C in the COL1A2 gene is pathogenic for OI by affecting the protein structure and the function of collagen.

Osteogenesis imperfecta

Skeletal deformity and bone fragility are the hallmarks of the brittle bone dysplasia osteogenesis imperfecta. The diagnosis of osteogenesis imperfecta usually depends on family history and clinical presentation characterized by a fracture (or fractures) during the prenatal period, at birth or in early childhood; genetic tests can confirm diagnosis. Osteogenesis imperfecta is caused by dominant autosomal mutations in the type I collagen coding genes (COL1A1 and COL1A2) in about 85% of individuals, affecting collagen quantity or structure. In the past decade, (mostly) recessive, dominant and X-linked defects in a wide variety of genes encoding proteins involved in type I collagen synthesis, processing, secretion and post-translational modification, as well as in proteins that regulate the differentiation and activity of bone-forming cells have been shown to cause osteogenesis imperfecta. The large number of causative genes has complicated the classic classification of the disease, and although a new genetic classification system is widely used, it is still debated. Phenotypic manifestations in many organs, in addition to bone, are reported, such as abnormalities in the cardiovascular and pulmonary systems, skin fragility, muscle weakness, hearing loss and dentinogenesis imperfecta. Management involves surgical and medical treatment of skeletal abnormalities, and treatment of other complications. More innovative approaches based on gene and cell therapy, and signalling pathway alterations, are under investigation.

Monoallelic and biallelic CREB3L1 variant causes mild and severe osteogenesis imperfecta, respectively

Purpose

Osteogenesis imperfecta (OI) is a heritable skeletal dysplasia. Dominant pathogenic variants in COL1A1 and COL1A2 explain the majority of OI cases. At least fifteen additional genes have been identified, but still do not account for all OI phenotypes that present. We sought the genetic cause of mild and lethal OI phenotypes in an unsolved family.

Methods

We performed exome sequencing on seven members of the family, both affected and unaffected.

Results

We identified a variant in Cyclic AMP Responsive Element Binding Protein 3-Like 1 (CREB3L1) in a consanguineous family. The variant caused a prenatal/perinatal lethal OI in homozygotes, similar to that seen in OI type II as a result of mutations in type I collagen genes, and a mild phenotype (fractures, blue sclerae) in multiple heterozygous family members. CREB3L1 encodes Old Astrocyte Specifically-Induced Substance (OASIS), an ER stress transducer. The variant disrupts a DNA-binding site and prevents OASIS from acting on its transcriptional targets including SEC24D, which encodes a component of the coat protein II (COPII) complex.

Conclusion

This report confirms that CREB3L1 is an OI-related gene and suggests the pathogenic mechanism of CREB3L1-associated OI involves the altered regulation of proteins involved in cellular secretion.

CARACTERÍSTICAS CLÍNICAS E PADRÃO DE FRATURAS NO MOMENTO DO DIAGNÓSTICO DE OSTEOGÊNESE IMPERFEITA EM CRIANÇAS

RESUMO Objetivo: Caracterizar o padrão de fraturas e a história clínica no momento do diagnóstico de osteogênese imperfeita. Métodos: Neste estudo retrospectivo, foram incluídos todos os pacientes com osteogênese imperfeita de ambos os sexos, com idades entre 0 e 18 anos, que realizaram tratamento entre 2002 e 2014. Os prontuários médicos foram revisados para coleta de dados clínicos, incluindo presença de escleras azuladas, dentinogênese imperfeita, história familiar positiva para a doença e locais das fraturas, além de achados radiográficos no momento do diagnóstico. Resultados: Foram incluídos no estudo 76 pacientes (42 do sexo feminino), com idade, no momento do diagnóstico, entre 0 e 114 meses [mediana (p25-p75) de idade de 38 (6-96) meses]. Escleras azuladas estavam presentes em 93,4% dos pacientes, dentinogênese imperfeita foi observada em 27,6% e ossos wormianos em 29,4%. O número de fraturas ao diagnóstico variou entre 0 e 17, com uma mediana de 3 (2-8) fraturas. Em 40 (57%) pacientes, as fraturas eram de membros superiores e inferiores no momento do diagnóstico e, em 9 pacientes também havia fratura vertebral. O diagnóstico foi realizado ao nascimento em 85,7% dos pacientes com o tipo 3 e em 39,3% daqueles com tipo 4/5 da doença. Conclusões: Osteogênese imperfeita é uma doença genética com características clínicas distintas, tais como fragilidade óssea, fraturas recorrentes, escleras azuladas e dentinogênese imperfeita. É importante saber identificar essas características, facilitando o diagnóstico, otimizando o tratamento e diferenciando de outras doenças que também podem causar fraturas.

Skeletal Dysplasias: Growing Therapy for Growing Bones

Skeletal dysplasias represent a large and diverse group of rare conditions affecting collagen and bone. They can be clinically classified based on radiographic and physical features, and many can be further defined at a molecular level (Bonafe et al., 2015). Early diagnosis is critical to proper medical management including pharmacologic treatment when available. Patients with severe skeletal dysplasias often have small chests with respiratory insufficiency or airway obstruction and require immediate intubation after birth. Thereafter a variety of orthopedic, neurosurgical, pulmonary, otolaryngology interventions may be needed. In terms of definitive treatment for skeletal dysplasias, there are few pharmacotherapeutic options available for the majority of these conditions. We sought to describe therapies that are currently available or under investigation for skeletal dysplasias.

Osteogenesis imperfecta in children and adolescents-new developments in diagnosis and treatment

Osteogenesis imperfecta (OI) is the most prevalent heritable bone fragility disorder in children. It has been known for three decades that the majority of individuals with OI have mutations in COL1A1 or COL1A2, the two genes coding for collagen type I alpha chains, but in the past 10 years defects in at least 17 other genes have been linked to OI. Almost all individuals with a typical OI phenotype have a mutation in one of the currently known genes. Regarding medical treatment, intravenous bisphosphonate therapy is the most widely used medical approach. This has a marked effect on vertebra in growing children and can lead to vertebral reshaping after compression fractures, but there is little effect of bisphosphonate therapy on the development of scoliosis. Bisphosphonate treatment decreases long-bone fracture rates, but such fractures are still frequent. Newer medications with anti-resorptive and bone anabolic action are being investigated in an attempt to improve on the efficacy of bisphosphonates but the safety and efficacy of these new approaches in children with OI is not yet established.

Pharmacological and biological therapeutic strategies for osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a connective tissue disorder characterized by bone fragility, low bone mass, and bone deformities. The majority of cases are caused by autosomal dominant pathogenic variants in the COL1A1 and COL1A2 genes that encode type I collagen, the major component of the bone matrix. The remaining cases are caused by autosomal recessively or dominantly inherited mutations in genes that are involved in the post-translational modification of type I collagen, act as type I collagen chaperones, or are members of the signaling pathways that regulate bone homeostasis. The main goals of treatment in OI are to decrease fracture incidence, relieve bone pain, and promote mobility and growth. This requires a multi-disciplinary approach, utilizing pharmacological interventions, physical therapy, orthopedic surgery, and monitoring nutrition with appropriate calcium and vitamin D supplementation. Bisphosphonate therapy, which has become the mainstay of treatment in OI, has proven beneficial in increasing bone mass, and to some extent reducing fracture risk. However, the response to treatment is not as robust as is seen in osteoporosis, and it seems less effective in certain types of OI, and in adult OI patients as compared to most pediatric cases. New pharmacological treatments are currently being developed, including anti-resorptive agents, anabolic treatment, and gene- and cell-therapy approaches. These therapies are under different stages of investigation from the bench-side, to pre-clinical and clinical trials. In this review, we will summarize the recent findings regarding the pharmacological and biological strategies for the treatment of patients with OI. © 2016 Wiley Periodicals, Inc.

Emerging targeted drug therapies in skeletal dysplasias

Quantum advances have occurred in the field of human genetics in the six decades since Watson and Crick expressed their "wish to suggest a structure for the salt of deoxyribose nucleic acid." These culminated with the human genome project, which has opened up myriad possibilities, including that of individualized genetic medicine, the ability to deliver medical advice, management, and therapy tailored to an individual's genetic blueprint. Advances in genetic diagnostic capabilities have been rapid, to the point where the genome can be sequenced for several thousand dollars. Crucially, it has facilitated the identification of targets for "precision" treatments to combat genetic diseases at their source. This manuscript will review the innovative, pathogenesis-based therapies that are revolutionizing management of skeletal dysplasias, giving patients and families new options and outcomes. © 2016 Wiley Periodicals, Inc.

Phase angle and World Health Organization criteria for the assessment of nutritional status in children with osteogenesis imperfecta

OBJECTIVE

To compare the phase angle of patients with osteogenesis imperfecta treated at a tertiary university hospital with patients in a control group of healthy children, and to assess the nutritional status of these patients through the body mass index proposed by the World Health Organization.

METHODS

Cross-sectional study carried out in a university hospital that included seven patients with osteogenesis imperfecta and a control group of 17 healthy children of the same gender and age. Weight and height were measured and bioelectrical impedance was performed. Subsequently, the phase angle was calculated based on resistance and reactance values.

RESULTS

The phase angle of the group of children with osteogenesis imperfecta was significantly lower than that of the control group (p<0.05). The body mass index criterion for age of the World Health Organization showed no difference between groups.

CONCLUSIONS

Children with osteogenesis imperfecta have a nutritional risk detected by the phase angle, which is a useful tool for nutritional screening. The calculation result could help in the diet therapy of patients with osteogenesis imperfecta.

Dental panoramic indices and fractal dimension measurements in osteogenesis imperfecta children under pamidronate treatment

OBJECTIVES

To verify radiomorphometric indices and fractal dimension (FD) in dental panoramic radiographs (DPRs) of children with different types of osteogenesis imperfecta (OI) and also to verify the effect of pamidronate (PAM) treatment in such panoramic analyses.

METHODS

In this retrospective study, 197 DPRs of 62 children with OI Types I, III and IV who were in treatment with a comparable dosage of intravenous PAM were selected. The mandibular cortical width (MCW), mandibular cortical index, visual estimation of the cortical width and FD of three standardized trabecular and cortical mandibular regions of interest were obtained from the radiographs. Factorial analysis of variance and Fisher test were used to compare FD and MCW measurements in children with different types of OI for different PAM cycles.

RESULTS

Children with all types of OI have thinner and more porous mandibular cortices at the beginning of treatment. There were significant differences between MCW and FD of the cortical bone, regarding different types of OI and number of PAM cycles (p = 0.037 and p = 0.044, respectively). FD measurements of the trabecular bone were not statistically different among OI types nor were PAM cycles (p > 0.05).

CONCLUSIONS

Children with OI presented cortical bone alterations after PAM treatment. Both MCW and the FD of the cortical bone were higher in children with OI after PAM treatment. It is argued that cortical bone should be considered for analyzing patients with OI, as well as to monitor the progress of PAM treatment.

Advances in the Classification and Treatment of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a rare disorder of type 1 collagen with 13 currently identified types attributable to inherited abnormalities in type 1 collagen amount, structure, or processing. The disease is characterized by an increased susceptibility to bony fracture. In addition to the skeletal phenotype, common additional extraskeletal manifestations include blue sclerae, dentinogenesis imperfecta, vascular fragility, and hearing loss. Medical management is focused on minimizing the morbidity of fractures, pain, and bone deformities by maximizing bone health. Along with optimizing Vitamin D status and calcium intake and physical/occupational therapy, individualized surgical treatment may be indicated. Pharmacological therapy with bisphosphonate medications is now routinely utilized for moderate to severe forms and appears to have a good safety profile and bone health benefits. New therapies with other anti-resorptives as well as anabolic agents and transforming growth factor (TGF)β antibodies are in development. Other potential treatment modalities could include gene therapy or mesenchymal cell transplant. In the future, treatment choices will be further individualized in order to reduce disease morbidity and mortality.

Value of rare low bone mass diseases for osteoporosis genetics

Osteoporosis presents as increased susceptibility to fractures due to bone loss and compromised bone microstructure. Osteoporosis mainly affects the elderly population, but it is increasingly recognized that compromised bone health with low bone mass and increased fractures may have its onset already in childhood. In such cases, genetic component is likely to contribute more than lifestyle factors to disease onset. During the last decade, our understanding of the genetic determinants of osteoporosis has significantly increased through family studies, candidate gene studies and genome-wide association studies (GWASs). GWASs have led to identification of several genetic loci associated with osteoporosis. A valuable contribution to the research field has been made through studies involving families with childhood-onset rare bone diseases such as osteogenesis imperfecta, osteoporosis-pseudoglioma syndrome and various other skeletal dysplasias with reduced bone mass. Some genes involved in rare low bone mass diseases, such as LRP5 and WNT1, participate in the Wnt/β-catenin pathway, and their discovery has underscored the importance of this pathway for normal skeletal health. The still continuing discovery of gene defects underlying various low bone mass phenotypes contributes to our understanding of normal bone metabolism and enables development of new therapies for osteoporosis.

A rare combination of amniotic constriction band with osteogenesis imperfecta

Amniotic constriction bands and osteogenesis imperfecta are disorders arising from a collagen defect. We report a rare association of amniotic bands with osteogenesis imperfecta in a child. The child was born with multiple amniotic bands involving the right leg, both hands and both feet. Multiple fractures of long bones of lower limbs occurred in childhood due to trivial trauma. Deformities of the femur and tibia due to malunion with osteopenia and blue sclerae were present. The patient was treated with z plasty of constriction band of the right tibia and bisphosphonate for osteogenesis imperfecta. This rare association of both collagen diseases may provide further insight for the pathogenesis of these diseases.

Multiple Low Energy Long Bone Fractures in the Setting of Rothmund-Thomson Syndrome

Rothmund-Thomson syndrome is a rare autosomal recessive genodermatosis characterized by a poikilodermatous rash starting in infancy as well as various skeletal anomalies, juvenile cataracts, and predisposition to certain cancers. Although Rothmund-Thomson syndrome is associated with diminished bone mineral density in addition to multiple skeletal abnormalities, there are few reports of the association with stress fractures or pathologic fractures in low energy trauma or delayed healing of fractures. Presented is a case of a young adult male with Rothmund-Thomson syndrome presenting with multiple episodes of long bone fractures caused by low energy trauma with one of the fractures exhibiting significantly delayed healing. The patient was also found to have an asymptomatic stress fracture of the lower extremity, another finding of Rothmund-Thomson syndrome rarely reported in the literature. A thorough review of the literature and comprehensive presentation of Rothmund-Thomson syndrome is provided in conjunction with our case.

Hindlimb Skeletal Muscle Function and Skeletal Quality and Strength in +/G610C Mice With and Without Weight-Bearing Exercise

Osteogenesis imperfecta (OI) is a heterogeneous heritable connective tissue disorder associated with reduced bone mineral density and skeletal fragility. Bone is inherently mechanosensitive, with bone strength being proportional to muscle mass and strength. Physically active healthy children accrue more bone than inactive children. Children with type I OI exhibit decreased exercise capacity and muscle strength compared with healthy peers. It is unknown whether this muscle weakness reflects decreased physical activity or a muscle pathology. In this study, we used heterozygous G610C OI model mice (+/G610C), which model both the genotype and phenotype of a large Amish OI kindred, to evaluate hindlimb muscle function and physical activity levels before evaluating the ability of +/G610C mice to undergo a treadmill exercise regimen. We found +/G610C mice hindlimb muscles do not exhibit compromised muscle function, and their activity levels were not reduced relative to wild-type mice. The +/G610C mice were also able to complete an 8-week treadmill regimen. Biomechanical integrity of control and exercised wild-type and +/G610C femora were analyzed by torsional loading to failure. The greatest skeletal gains in response to exercise were observed in stiffness and the shear modulus of elasticity with alterations in collagen content. Analysis of tibial cortical bone by Raman spectroscopy demonstrated similar crystallinity and mineral/matrix ratios regardless of sex, exercise, and genotype. Together, these findings demonstrate +/G610C OI mice have equivalent muscle function, activity levels, and ability to complete a weight-bearing exercise regimen as wild-type mice. The +/G610C mice exhibited increased femoral stiffness and decreased hydroxyproline with exercise, whereas other biomechanical parameters remain unaffected, suggesting a more rigorous exercise regimen or another exercise modality may be required to improve bone quality of OI mice.