COL11A2 as a candidate gene for vertebral malformations and congenital scoliosis.

Human vertebral malformations (VMs) have an estimated incidence of 1/2000 and are associated with significant health problems including congenital scoliosis (CS) and recurrent organ system malformation syndromes such as VACTERL (vertebral anomalies; anal abnormalities; cardiac abnormalities; tracheo-esophageal fistula; renal anomalies; limb anomalies). The genetic cause for the vast majority of VMs are unknown. In a CS/VM patient cohort, three COL11A2 variants (R130W, R1407L and R1413H) were identified in two patients with cervical VM. A third patient with a T9 hemivertebra and the R130W variant was identified from a separate study. These substitutions are predicted to be damaging to protein function, and R130 and R1407 residues are conserved in zebrafish Col11a2. To determine the role for COL11A2 in vertebral development, CRISPR/Cas9 was used to create a nonsense mutation (col11a2L642*) as well as a full gene locus deletion (col11a2del) in zebrafish. Both col11a2L642*/L642* and col11a2del/del mutant zebrafish exhibit vertebral fusions in the caudal spine, which form due to mineralization across intervertebral segments. To determine the functional consequence of VM-associated variants, we assayed their ability to suppress col11a2del VM phenotypes following transgenic expression within the developing spine. While wildtype col11a2 expression suppresses fusions in col11a2del/+ and col11a2del/del backgrounds, patient missense variant-bearing col11a2 failed to rescue the loss-of-function phenotype in these animals. These results highlight an essential role for COL11A2 in vertebral development and support a pathogenic role for two missense variants in CS.

Osteogenesis Imperfecta: Skeletal and Non-skeletal Challenges in Adulthood.

Osteogenesis imperfecta (OI) is a Mendelian connective tissue disorder associated with increased bone fragility and other clinical manifestations most commonly due to abnormalities in production, structure, or post-translational modification of type I collagen. Until recently, most research in OI has focused on the pediatric population and much less attention has been directed at the effects of OI in the adult population. This is a narrative review of the literature focusing on the skeletal as well as non-skeletal manifestations in adults with OI that may affect the aging individual. We found evidence to suggest that OI is a systemic disease which involves not only the skeleton, but also the cardiopulmonary and gastrointestinal system, soft tissues, tendons, muscle, and joints, hearing, eyesight, dental health, and women's health in OI and potentially adds negative affect to health-related quality of life. We aim to guide clinicians as well as draw attention to obvious knowledge gaps and the need for further research in adult OI.

Clinical utility of comprehensive gene panel testing for common and rare causes of skeletal dysplasia and other skeletal disorders: Results from the largest cohort to date.

Molecular genetics enables more precise diagnoses of skeletal dysplasia and other skeletal disorders (SDs). We investigated the clinical utility of multigene panel testing for 5011 unrelated individuals with SD in the United States (December 2019-April 2022). Median (range) age was 8 (0-90) years, 70.5% had short stature and/or disproportionate growth, 27.4% had a positive molecular diagnosis (MDx), and 30 individuals received two MDx. Genes most commonly contributing to MDx were FGFR3 (16.9%), ALPL (13.0%), and COL1A1 (10.3%). Most of the 112 genes associated with ≥1 MDx were primarily involved in signal transduction (n = 35), metabolism (n = 23), or extracellular matrix organization (n = 17). There were implications associated with specific care/treatment options for 84.4% (1158/1372) of MDx-positive individuals; >50% were linked to conditions with targeted therapy approved or in clinical development, including osteogenesis imperfecta, achondroplasia, hypophosphatasia, and mucopolysaccharidosis. Forty individuals with initially inconclusive results became MDx-positive following family testing. Follow-up mucopolysaccharidosis enzyme activity testing was positive in 14 individuals (10 of these were not MDx-positive). Our findings showed that inclusion of metabolic genes associated with SD increased the clinical utility of a gene panel and confirmed that integrated use of comprehensive gene panel testing with orthogonal testing reduced the burden of inconclusive results.

Patient-reported prevalence of gastrointestinal issues in the adult skeletal dysplasia population with a concentration on osteogenesis imperfecta.

Patient-reported concerns indicate that gastrointestinal (GI) manifestations affect the skeletal dysplasia population, but quantitative information regarding prevalence and severity of GI issues is limited. We examined the frequency and characteristics of GI symptoms in adults with skeletal dysplasias by reviewing 101 responses to the Gastrointestinal Symptom Rating Scale (GSRS). Participant demographics, medication history, and ambulatory status were collected from medical records. Compared to published GSRS reference data, our cohort scored higher on reflux, diarrhea, and total scores, and lower on abdominal pain and indigestion scores; none of these differences were statistically significant. Although osteogenesis imperfecta respondents had more severe symptoms across all domains, only reflux reached significance (p = 0.009). Scores in patients with achondroplasia were higher for indigestion, constipation, diarrhea, and total scores and lower on abdominal pain and reflux scores than the general population; only the diarrhea score was significant (p = 0.034). There were no statistically significant differences in any of the domain or total GSRS scores across ambulatory status groups. Increased height correlated with worse abdominal pain domain score (p = 0.033). The number of medications positively correlated with total GSRS score (p = 0.013). Future studies should include larger numbers of individuals to allow a more in-depth analysis of patient-reported symptoms and signs within this population.

Orthopedic considerations and surgical outcomes in Ehlers-Danlos syndromes.

The Ehlers-Danlos syndromes (EDS) are a clinically and genetically heterogeneous group of connective tissue disorders with varying physical manifestations. There are no clear guidelines for addressing orthopedic concerns or reporting surgical outcomes in this population. This article reviews the literature, reports on a new study, and offers considerations prior to surgical intervention. The new study seeks to determine the effectiveness of surgical intervention in individuals with EDS. It is a retrospective chart review of 154 individuals clinically diagnosed with EDS who had orthopedic surgery >2 years ago at Hospital for Special Surgery. A total of 120 individuals were included in the study. One hundred eleven females and 9 males underwent a total of 320 orthopedic surgeries, of which 204 surgeries had available post-operative follow-up. The average age at surgery was 38.2 years (range: 7.6-83.3). Multiple post-operative complications (290) were reported in 91% of cases. Common complications were persistent pain/discomfort (45), continued subluxation/dislocation (20), instability (19), pain/discomfort from hardware (17), and infection (16). Our results suggest that surgical outcomes are worse for individuals with EDS compared to the general population, a finding which is similar to other studies. Complications occurred more frequently in the EDS population than the average population, suggesting that surgery should be undertaken by a multidisciplinary team of clinicians with careful pre-operative planning and full knowledge of the risks and benefits. Guidelines for the care of this unique population must be established.

Quality of life in adults with achondroplasia in the United States.

Studies examining quality of life (QoL) in adults with achondroplasia are limited. We report on QoL and psychiatric illness diagnoses in a modern cohort of adults with achondroplasia. SF-36 Health Survey scores from adults with achondroplasia were compared to general population scores. Demographics, physical measurements, and psychiatric illness diagnoses were recorded from medical records. The achondroplasia population had lower scores than the general population in all categories. Most people with achondroplasia (56%) had a diagnosed psychiatric illness. Those with a diagnosed psychiatric illness had lower scores in physical functioning, role limitations due to physical and emotional health, and mental health. Pain, energy/fatigue, and general health scale scores were roughly equivalent (<2 points difference). Social functioning was >15 points higher in individuals with psychiatric illness diagnoses. Adults with achondroplasia report significantly lower physical and mental well-being and had nearly 3× the rate of psychiatric illness diagnosis than the general population, highlighting the importance of total care for this population. Healthcare providers must understand the physical and mental comorbidities of achondroplasia, beyond short stature and orthopedic issues, so they can proactively improve QoL across the lifespan for patients and families.

Blood pressure in adults with short stature skeletal dysplasias.

Hypertension, compounded by obesity, contributes to cardiovascular disease and mortality. Data describing hypertension prevalence in adults with short stature skeletal dysplasias are lacking, perhaps due to poor fit of typical adult blood pressure cuffs on rhizomelic or contracted upper extremities. Through health screening research, blood pressure was measured in short stature adults attending support group meetings and skeletal dysplasia clinics. Blood pressure was measured with a commercially available, narrower adult cuff on the upper and/or lower segment of the arm. Height, weight, age, gender, diagnosis, exercise, and medications were collected. Subjects were classified as normotensive, prehypertensive, or hypertensive for group analysis; no individual clinical diagnoses were made. In 403 short stature adults, 42% were hypertensive (systolic >140, diastolic >90 OR taking antihypertensive medications). For every BMI unit and 1 kg weight increase in males, there was a 9% and an 8% increase, respectively, in the odds of hypertension versus normotension. In females, the increase was 10% and 6%, respectively. In those with achondroplasia, the most common short stature dysplasia, males (n = 106) had 10% greater odds of hypertension versus normotension for every BMI unit and kilogram increase. In females with achondroplasia (n = 128), the odds of hypertension versus normotension was 8% greater for each BMI unit and 7% for each additional kilogram. These data suggest a high population prevalence of hypertension among short stature adults. Blood pressure must be monitored as part of routine medical care, and measuring at the forearm may be the only viable clinical option in rhizomelic short stature adults with elbow contractures.

Hearing loss in individuals with osteogenesis imperfecta in North America: Results from a multicenter study.

Hearing loss (HL) is an extra-skeletal manifestation of the connective tissue disorder osteogenesis imperfecta (OI). Systematic evaluation of the prevalence and characteristics of HL in COL1A1/COL1A2-related OI will contribute to a better clinical management of individuals with OI. We collected and analyzed pure-tone audiometry data from 312 individuals with OI who were enrolled in the Linked Clinical Research Centers and the Brittle Bone Disorders Consortium. The prevalence, type, and severity of HL in COL1A1/COL1A2-related OI are reported. We show that the prevalence of HL in OI is 28% and increased with age in Type I OI but not in Types III and IV. Individuals with OI Types III and IV are at a higher risk to develop HL in the first decade of life when compared to OI Type I. We also show that the prevalence of SNHL is higher in females with OI compared to males. This study reveals new insights regarding prevalence of HL in OI including a lower general prevalence of HL in COL1A1/COL1A2-related OI than previously reported (28.3 vs. 65%) and high prevalence of SNHL in females. Our data support the need in early routine hearing evaluation in all types of OI that can be adjusted to the severity of the skeletal disease.

Distal chromosome 16p11.2 duplications containing SH2B1 in patients with scoliosis.

INTRODUCTION: Adolescent idiopathic scoliosis (AIS) is a common musculoskeletal disorder with strong evidence for a genetic contribution. CNVs play an important role in congenital scoliosis, but their role in idiopathic scoliosis has been largely unexplored. METHODS: Exome sequence data from 1197 AIS cases and 1664 in-house controls was analysed using coverage data to identify rare CNVs. CNV calls were filtered to include only highly confident CNVs with >10 average reads per region and mean log-ratio of coverage consistent with single-copy duplication or deletion. The frequency of 55 common recurrent CNVs was determined and correlated with clinical characteristics. RESULTS: Distal chromosome 16p11.2 microduplications containing the gene SH2B1 were found in 0.7% of AIS cases (8/1197). We replicated this finding in two additional AIS cohorts (8/1097 and 2/433), resulting in 0.7% (18/2727) of all AIS cases harbouring a chromosome 16p11.2 microduplication, compared with 0.06% of local controls (1/1664) and 0.04% of published controls (8/19584) (p=2.28×10-11, OR=16.15). Furthermore, examination of electronic health records of 92 455 patients from the Geisinger health system showed scoliosis in 30% (20/66) patients with chromosome 16p11.2 microduplications containing SH2B1 compared with 7.6% (10/132) of controls (p=5.6×10-4, OR=3.9). CONCLUSIONS: Recurrent distal chromosome 16p11.2 duplications explain nearly 1% of AIS. Distal chromosome 16p11.2 duplications may contribute to scoliosis pathogenesis by directly impairing growth or by altering expression of nearby genes, such as TBX6. Individuals with distal chromosome 16p11.2 microduplications should be screened for scoliosis to facilitate early treatment.

Cardiopulmonary Status in Adults with Osteogenesis Imperfecta: Intrinsic Lung Disease May Contribute More Than Scoliosis.

BACKGROUND: Osteogenesis imperfecta (OI) is a heterogeneous group of collagen-related disorders characterized by osteopenia, bone fractures, spine deformities, and nonskeletal complications. Cardiopulmonary complications are the major cause of morbidity and mortality in adults with OI. The cause of such problems was often attributed solely to the presence of large scoliosis curves affecting pulmonary function and, indirectly, cardiovascular health. However, recent studies suggest this may not be the case. Therefore, determining the relationships and causative agents of cardiopulmonary problems in patients with OI, specifically pulmonary impairment, is important to improving the overall wellbeing, quality of life, and survival of these patients. QUESTIONS/PURPOSES: (1) Is cardiopulmonary fitness in OI solely related to the presence of scoliosis? (2) What is the prevalence of heart and lung complications in this adult population? (3) Does the presence of pulmonary impairment impact quality of life in adults with OI? METHODS: This is a prospective observational cross-sectional study. Within 1 year, each participant (n = 30) completed pulmonary function testing, echocardiogram, ECG, chest CT, AP spine radiography, and quality-of-life assessments (SF-36, St. George's Respiratory Questionnaire, Functional Outcomes of Sleep Questionnaire, and Pittsburgh Sleep Quality Index). In terms of pulmonary function, we differentiated restrictive and obstructive physiology using the ratio of forced expiratory volume over one second to forced vital capacity (FEV1/FVC), with restrictive lung physiology defined as FEV1/FVC > 0.8 and obstructive lung physiology as FEV1/FVC < 0.7. Spine radiographs were evaluated for scoliosis. Chest CT images were reviewed to qualitatively assess the lungs. The statistical analysis involved a Kruskall-Wallis test with Bonferroni's correction and a bivariate correlation analysis using Spearman's rho correlation coefficient (p < 0.05). RESULTS: Sixteen of 23 participants with restrictive lung physiology had scoliosis; their ages ranged from 19 years to 67 years. There was no correlation between the magnitude of the scoliosis curve and deficient pulmonary function (R = 0.08; p = 0.68). Seven participants had normal pulmonary function. The average scoliosis curve was 44 ± 29°. Thirteen participants had abnormal ECG findings while 10 had abnormal echocardiogram results. All but two individuals with abnormal chest CT results were found to have bronchial wall thickening. There were no differences in pulmonary or cardiac findings between OI types, except for FVC and total lung capacity, which were lower in individuals with Type III OI than in those with other types of OI. FEV1/FVC correlated with St. George's Respiratory Questionnaire (R = 0.429; p = 0.02) but not with Functional Outcomes of Sleep Questionnaire (R = -0.26; p = 0.19) or SF-36 scores (physical component summary: R = -0.037, p = 0.85; mental component summary: R = -0.204, p = 0.29). CONCLUSIONS: The lack of a relationship between decreased pulmonary function and the severity of scoliosis suggests that restrictive lung physiology in this population is likely because of factors intrinsic to OI and not entirely because of thoracic cage deformities. The fact that pulmonary impairment influences self-perceived quality of life exemplifies how detrimental such complications may be to everyday functioning. This also reinforces the importance of determining the underlying cause of cardiopulmonary impairment in this population to set clear clinical guidelines of care. LEVEL OF EVIDENCE: Level II, prognostic study.

Joint Replacements in Individuals With Skeletal Dysplasias: One Institution's Experience and Response to Operative Complications.

BACKGROUND: Skeletal dysplasias are a heterogeneous group of >400 genetic disorders characterized by abnormal bone growth. Many individuals experience joint pain and limitation, coming to require joint replacement much earlier than the average-statured population. In addition, prosthesis survival rate is less in the dysplastic population. The purpose of this study is to identify risk factors for surgery and provide recommendations to improve surgical outcomes. METHODS: This a retrospective review of 29 individuals with a skeletal dysplasia who had 64 joint replacements between April 1985 and January 2019 at a single institution. We collected demographics, physical examination, medical history, imaging studies, surgical indication, and complications. RESULTS: Spondyloepiphyseal dysplasia was the most common skeletal dysplasia (7), followed by pseudoachondroplasia (4) and multiple epiphyseal dysplasia (4). Average age of the cohort was 40.6 years (range 14-64). Hip arthroplasty (34) was the most commonly performed surgery. The majority of arthroplasties (75%) required custom components. Complication rate was 37.3%, most commonly pulmonary embolism (3) and pneumonia (3). Most complications (81.8%) occurred in individuals with either a pre-existing cardiopulmonary comorbidity or lumbar/sacral deformity. Body mass index did not correlate with complication severity (R = -0.042, P = .752) or rate (R = 0.006, P = .963). CONCLUSION: Surgical complications are highest in patients with pre-existing cardiopulmonary conditions. Body mass index does not predict complications in this cohort. Preoperative evaluations for individuals with skeletal dysplasias should include comprehensive work-up of spine issues and extraskeletal systems that present an operative risk. Intraoperative protocol should include special consideration for placement on the table, airway maintenance, and spinal cord monitoring in select cases.

Best practice guidelines regarding diagnosis and management of patients with type II collagen disorders.

PURPOSE: Skeletal dysplasias comprise a heterogeneous group of inherited disorders of development, growth, and maintenance of the human skeleton. Because of their relative rarity and wide phenotypic variability, patients should be accurately identified, uniformly assessed, and managed by clinicians who are aware of their potential complications and possess the knowledge and resources to treat them effectively. This study presents expert guidelines developed to improve the diagnosis and management of patients with type II collagen skeletal disorders to optimize clinical outcomes. METHODS: A panel of 11 multidisciplinary international experts in the field of skeletal dysplasia participated in a Delphi process, which comprised analysis of a thorough literature review with subsequent generation of 26 diagnosis and care recommendations, followed by two rounds of anonymous voting with an intervening face-to-face meeting. Those recommendations with more than 80% agreement were considered as consensual. RESULTS: After the first voting round, consensus was reached to support 12 of 26 (46%) statements. After the panel discussion, the group reached consensus on 22 of 24 revised statements (92%). CONCLUSIONS: Consensus-based, expert best practice guidelines developed as a standard of care to assist accurate diagnosis, minimize associated health risks, and improve clinical outcomes for patients with type II collagen skeletal dysplasias.

TBX6-associated congenital scoliosis (TACS) as a clinically distinguishable subtype of congenital scoliosis: further evidence supporting the compound inheritance and TBX6 gene dosage model.

PURPOSE: To characterize clinically measurable endophenotypes, implicating the TBX6 compound inheritance model. METHODS: Patients with congenital scoliosis (CS) from China(N = 345, cohort 1), Japan (N = 142, cohort 2), and the United States (N = 10, cohort 3) were studied. Clinically measurable endophenotypes were compared according to the TBX6 genotypes. A mouse model for Tbx6 compound inheritance (N = 52) was investigated by micro computed tomography (micro-CT). A clinical diagnostic algorithm (TACScore) was developed to assist in clinical recognition of TBX6-associated CS (TACS). RESULTS: In cohort 1, TACS patients (N = 33) were significantly younger at onset than the remaining CS patients (P = 0.02), presented with one or more hemivertebrae/butterfly vertebrae (P = 4.9 × 10‒8), and exhibited vertebral malformations involving the lower part of the spine (T8-S5, P = 4.4 × 10‒3); observations were confirmed in two replication cohorts. Simple rib anomalies were prevalent in TACS patients (P = 3.1 × 10‒7), while intraspinal anomalies were uncommon (P = 7.0 × 10‒7). A clinically usable TACScore was developed with an area under the curve (AUC) of 0.9 (P = 1.6 × 10‒15). A Tbx6-/mh (mild-hypomorphic) mouse model supported that a gene dosage effect underlies the TACS phenotype. CONCLUSION: TACS is a clinically distinguishable entity with consistent clinically measurable endophenotypes. The type and distribution of vertebral column abnormalities in TBX6/Tbx6 compound inheritance implicate subtle perturbations in gene dosage as a cause of spine developmental birth defects responsible for about 10% of CS.

Acetabular Protrusio in Patients With Osteogenesis Imperfecta: Risk Factors and Progression.

BACKGROUND: Osteogenesis imperfecta (OI) is a genetic disorder commonly associated with osteopenia, osteoporosis, bone fractures, bone deformities, and other clinical features. A frequent radiologic finding with OI is acetabular protrusio (AP). We hypothesized that AP develops in patients with OI over time. In addition, we hypothesized that AP also develops in patients with OI without radiographic evidence of AP on initial examination. METHODS: Medical records and radiographs of 55 patients (109 hips) diagnosed with OI evaluated at our institution were retrospectively reviewed. Previously established radiographic criteria using the center-edge (CE) angle of Wiberg, position of the acetabulum relative to the iliopectineal line, crossing of the acetabulum across the ilioischial (Kohler) line, and position of the teardrop figure relative to the ilioischial (Kohler) line were utilized to assess AP severity. In addition, pharmacological treatments and patient factors including body mass index (BMI) were recorded. Radiographs of patients with OI that were taken ≥2 years apart were analyzed utilizing AP radiographic criteria to assess for changes. The changes in AP-related measurements were standardized by distance or degree per year. In addition, patient factors were evaluated for associations with AP development. RESULTS: In this series of 109 hips (55 patients), incidence of AP in earliest radiographs was 45% (49/109). Patients with OI type I and III demonstrated the highest incidence of AP (65%). Among the hips that did not meet the criteria for AP in their early radiographs, 24 (40%) were positive for AP by their latest radiograph. In the hips that initially presented with AP, 42% showed increased CE angles on later radiographs. Twenty-six hips (24%) showed either no observable changes or reduced CE angles. Risk factors that were significantly associated with greater odds of developing AP included (1) an age under 12; (2) a BMI>25; (3) presence of AP of the contralateral hip; and (4) female sex. Bisphosphonates, vitamin D, physical therapy, and other drugs related to treatment of OI reduced the risk of developing AP but did not achieve statistical significance. CONCLUSIONS: AP is a common finding in OI patients (54%). Among hips of OI patients that met criteria for AP in early radiographs, 42% (20/48) demonstrated greater CE angles in their latest radiographs. Similar changes were observed in OI patients who did not initially meet criteria for diagnosis for AP. However, CE angle measurements between the 2 groups did not significantly differ (P=0.71). In terms of Kohler line crossing, patients that met criteria for AP in early radiographs had significantly greater change per year than those that did not have AP criteria (P<0.05). The findings suggest AP may develop over time in patients with OI and may be influenced by patient factors such as age, sex, and BMI. In addition, unilateral AP may have a significant impact on the development of AP of the contralateral hip. LEVEL OF EVIDENCE: Level IV-retrospective case series.

Best practice guidelines regarding prenatal evaluation and delivery of patients with skeletal dysplasia.

BACKGROUND: Skeletal dysplasia comprises a heterogeneous and collectively common group of inherited disorders of development, growth, and maintenance of the human skeleton. There is potential for increased perinatal morbidity and mortality in pregnant women who themselves have skeletal dysplasia, and for affected fetuses where skeletal dysplasia is suspected in utero. OBJECTIVE: We sought to establish guidelines for perinatal health care professionals who should be aware of these risks, to optimize maternal and child health pregnancy outcomes through best prenatal and delivery management practices. STUDY DESIGN: A panel of 13 multidisciplinary international experts participated in a Delphi process, which comprised consideration of thorough literature review and a list of 54 possible care recommendations subject to 2 rounds of anonymous voting and a face-to-face meeting. Those recommendations with >80% agreement were considered as consensual. RESULTS: During the first round, consensus was reached to support 30 out of the 54 statements. After the panel discussion, the group reached consensus on 40 statements. These statements include guidelines for the evaluation and treatment of pregnant women with skeletal dysplasia and for the unborn child with or suspected to have skeletal dysplasia. CONCLUSION: Consensus-based best practice guidelines are provided as a minimum of standard care to minimize associated health risks, and improve clinical outcomes for patients with skeletal dysplasia.

Best practices in peri-operative management of patients with skeletal dysplasias.

Patients with skeletal dysplasia frequently require surgery. This patient population has an increased risk for peri-operative complications related to the anatomy of their upper airway, abnormalities of tracheal-bronchial morphology and function; deformity of their chest wall; abnormal mobility of their upper cervical spine; and associated issues with general health and body habitus. Utilizing evidence analysis and expert opinion, this study aims to describe best practices regarding the peri-operative management of patients with skeletal dysplasia. A panel of 13 multidisciplinary international experts participated in a Delphi process that included a thorough literature review; a list of 22 possible care recommendations; two rounds of anonymous voting; and a face to face meeting. Those recommendations with more than 80% agreement were considered as consensual. Consensus was reached to support 19 recommendations for best pre-operative management of patients with skeletal dysplasia. These recommendations include pre-operative pulmonary, polysomnography; cardiac, and neurological evaluations; imaging of the cervical spine; and anesthetic management of patients with a difficult airway for intubation and extubation. The goals of this consensus based best practice guideline are to provide a minimum of standardized care, reduce perioperative complications, and improve clinical outcomes for patients with skeletal dysplasia.

Best practices in the evaluation and treatment of foramen magnum stenosis in achondroplasia during infancy.

Achondroplasia is the most common inherited disorder of bone growth (skeletal dysplasia). Despite this fact, consistent and evidence-based management approaches to recognized, life-threatening complications, such as foramen magnum stenosis, are lacking. This study aims to outline best practice, based on evidence and expert consensus, regarding the diagnosis, assessment, and management of foramen magnum stenosis in achondroplasia during infancy. A panel of 11 multidisciplinary international experts on skeletal dysplasia was invited to participate in a Delphi process. They were: 1) presented with a list of 26 indications and a thorough literature review, 2) given the opportunity to anonymously rate the indications and discuss in face to face discussion; 3) edit the list and rate it in a second round. Those indications with more than 80% agreement were considered as consensual. After two rounds of rating and a face-to-face meeting, consensus was reached to support 22 recommendations for the evaluation and treatment of foramen magnum stenosis in infants with achondroplasia. These recommendations include indications for surgical decompression, ventriculomegaly, and hydrocephalus, sleep-disordered breathing, physical exams and the use of polysomnography and imaging in this condition. We present a consensus-based best practice guidelines consisting of 22 recommendations. It is hoped that these guidelines will lead to more uniform and structured evaluation, standardizing care pathways, and improving mortality and morbidity outcomes for this cohort.

Are Changes in Composition in Response to Treatment of a Mouse Model of Osteogenesis Imperfecta Sex-dependent?

BACKGROUND: Osteogenesis imperfecta (OI) is a genetic disease characterized by skeletal fragility and deformity. There is extensive debate regarding treatment options in adults with OI. Antiresorptive treatment reduces the number of fractures in growing oim/oim mice, an animal model that reproducibly mimics the moderate-to-severe form of OI in humans. Effects of long-term treatments with antiresorptive agents, considered for treatment of older patients with OI with similar presentation (moderate-to-severe OI) are, to date, unknown. QUESTIONS/PURPOSES: Fourier transform infrared (FTIR) imaging, which produces a map of the spatial variation in chemical composition in thin sections of bone, was used to address the following questions: (1) do oim/oim mice show a sex dependence in compositional properties at 6.5 months of age; (2) is there a sex-dependent response to treatment with antiresorptive agents used in the treatment of OI in humans; and (3) are any compositional parameters in oim/oim mice corrected to wild-type (WT) values after treatment? METHODS: FTIR imaging data were collected from femurs from four to five mice per sex per genotype per treatment. Treatments were 24 weeks of saline, alendronate, or RANK-Fc; and 12 weeks of saline+12 weeks RANK-Fc and 12 weeks of alendronate+RANK-Fc. FTIR imaging compositional parameters measured in cortical and cancellous bones were mineral-to-matrix ratio, carbonate-to-mineral ratio, crystal size/perfection, acid phosphate substitution, collagen maturity, and their respective distributions (heterogeneities). Because of the small sample size, nonparametric statistics (Mann-Whitney U- and Kruskal-Wallis tests with Bonferroni correction) were used to compare saline-treated male and female mice of different genotypes and treatment effects by sex and genotype, respectively. Statistical significance was defined as p<0.05. RESULTS: At 6.5 months, saline-treated male cortical oim/oim bone had increased mineral-to-matrix ratio (p=0.016), increased acid phosphate substitution (p=0.032), and decreased carbonate-to-mineral ratio (p=0.016) relative to WT. Cancellous bone in male oim/oim also had increased mineral-to-matrix ratio (p=0.016) relative to male WT. Female oim/oim mouse bone composition for all cortical and cancellous bone parameters was comparable to WT (p>0.05). Only the female WT mice showed a response of mean compositional properties to treatment, increasing mineral-to-matrix after RANK-Fc treatment in cancellous bone (p=0.036) compared with saline-treated mice. Male oim/oim increased mineral-to-matrix cortical and cancellous bone heterogeneity in response to all long-term treatments except for saline+RANK-Fc (p<0.04); female oim/oim cortical mineral-to-matrix bone heterogeneity increased with ALN+RANK-Fc and all treatments increased cancellous female oim/oim bone acid phosphate substitution heterogeneity (p<0.04). CONCLUSIONS: Both oim/oim and WT mice, which demonstrate sex-dependent differences in composition with saline treatment, showed few responses to long-term treatment with antiresorptive agents. Female WT mice appeared to be more responsive; male oim/oim mice showed more changes in compositional heterogeneity. Changes in bone composition caused by these agents may contribute to improved bone quality in oim/oim mice, because the treatments are known to reduce fracture incidence. CLINICAL RELEVANCE: The optimal drug therapy for long-term treatment of patients with moderate-to-severe OI is unknown. Based on bone compositional changes in mice, antiresorptive treatments are useful for continued treatment in OI. There is a reported sexual dimorphism in fracture incidence in adults with OI, but to date, no one has reported differences in response to pharmaceutical intervention. This study suggests that such an investigation is warranted.

Acetabular Protrusio and Proximal Femur Fractures in Patients With Osteogenesis Imperfecta.

BACKGROUND: Osteogenesis imperfect (OI) is a genetic disorder characterized by increased bone fragility, frequent fractures, and extremity deformities among other clinical findings. A frequent radiographic finding in OI patients is acetabular protrusio (AP). We hypothesized that AP incidence would be significant in OI patients and highest among type III OI patients, who have a more severe disease phenotype. In addition, we hypothesized that there would be a correlation between AP and proximal femur fracture incidence. METHODS: We retrospectively reviewed radiographs and medical records of 49 patients with OI evaluated at our institution. Demographic information and modified Sillence classification were recorded. AP was diagnosed using previously published radiographic criteria using the center-edge angle of Wiberg, acetabulum relative to the iliopectineal line, teardrop figure relative to the ilioischial (Kohler) line, and acetabulum relative to the ilioischial (Kohler) line. Medical record and radiographs were reviewed for evidence of proximal femur or acetabulum fracture. Associations between OI type, AP, and fracture incidence were examined with χ or Fisher exact tests. RESULTS: In this series of 49 OI patients, the overall incidence of AP was 55.1% (27/49) with the highest incidence among patients with type III OI (70.6%). There was an increased incidence of proximal femur, and particularly femoral neck, fractures among patients with AP compared with patients with normal hip anatomy. Overall, patients with AP had a 30% increased risk for proximal femur and acetabulum fractures (P=0.03). CONCLUSIONS: AP is a common deformity in OI patients (55.1%) and particularly type III OI (70.6%). Patients with AP have an increased risk for proximal femur fractures and particularly femoral neck fractures. This novel finding adds to the growing body of literature on clinical implications of AP in OI patients. LEVEL OF EVIDENCE: Level IV-Retrospective case series.

Risedronate in children with osteogenesis imperfecta: a randomised, double-blind, placebo-controlled trial.

BACKGROUND: Children with osteogenesis imperfecta are often treated with intravenous bisphosphonates. We aimed to assess the safety and efficacy of risedronate, an orally administered third-generation bisphosphonate, in children with the disease. METHODS: In this multicentre, randomised, parallel, double-blind, placebo-controlled trial, children aged 4-15 years with osteogenesis imperfecta and increased fracture risk were randomly assigned by telephone randomisation system in a 2:1 ratio to receive either daily risedronate (2·5 or 5 mg) or placebo for 1 year. Study treatment was masked from patients, investigators, and study centre personnel. Thereafter, all children received risedronate for 2 additional years in an open-label extension. The primary efficacy endpoint was percentage change in lumbar spine areal bone mineral density (BMD) at 1 year. The primary efficacy analysis was done by ANCOVA, with treatment, age group, and pooled centre as fixed effects, and baseline as covariate. Analyses were based on the intention-to-treat population, which included all patients who were randomly assigned and took at least one dose of assigned study treatment. The trial is registered with ClinicalTrials.gov, number NCT00106028. FINDINGS: Of 147 patients, 97 were randomly assigned to the risedronate group and 50 to the placebo group. Three patients from the risedronate group and one from the placebo group did not receive study treatment, leaving 94 and 49 in the intention-to-treat population, respectively. The mean increase in lumbar spine areal BMD after 1 year was 16·3% in the risedronate group and 7·6% in the placebo group (difference 8·7%, 95% CI 5·7-11·7; p<0·0001). After 1 year, clinical fractures had occurred in 29 (31%) of 94 patients in the risedronate group and 24 (49%) of 49 patients in the placebo group (p=0·0446). During years 2 and 3 (open-label phase), clinical fractures were reported in 46 (53%) of 87 patients in the group that had received risedronate since the start of the study, and 32 (65%) of 49 patients in the group that had been given placebo during the first year. Adverse event profiles were otherwise similar between the two groups, including frequencies of reported upper-gastrointestinal and selected musculoskeletal adverse events. INTERPRETATION: Oral risedronate increased areal BMD and reduced the risk of first and recurrent clinical fractures in children with osteogenesis imperfecta, and the drug was generally well tolerated. Risedronate should be regarded as a treatment option for children with osteogenesis imperfecta. FUNDING: Alliance for Better Bone Health (Warner Chilcott and Sanofi).