Bone healing in children with osteogenesis imperfecta treated with bisphosphonates

Prevalence, number of fractures, and hospital characteristics among the pediatric population with osteogenesis imperfecta: results from the nationwide registry of Türkiye

OBJECTIVE

Osteogenesis imperfecta is a rare connective tissue disorder with an estimated number of 4-20 cases per 100 000 inhabitants. Although the prevalence differs among regions, there are only a few number of national registry studies published previously. The aim of this study was to determine the prevalence of osteogenesis imperfecta among the pediatric age group in Türkiye, together with the patient and hospital characteristics.

METHODS

Via the e-health database of the Turkish Ministry of Health, we collected and retrospectively evaluated the medical records of the patients who were under 18 years of age with the diagnosis of osteogenesis imperfecta between 2016 and 2022. Total number of fractures, treatment modalities, and the hospital characteristics were also recorded. Two thousand seven hundred forty patients were extracted with a mean age of 9.77 ± 4.81 years.

RESULTS

The prevalence of osteogenesis imperfecta in Türkiye among the pediatric population was calculated as 11.6 per 100 000 individuals. The median annual incidence was 31.5 per 100 000 live births between 2016 and 2022. There were 17.4 hospital admissions per patient per year. The mean age at the time of in-hospital mortality was 4.08 ± 5.03 years. The fracture rate per patient per year was 0.56 and conservative treatment was the most commonly preferred modality for all ages.

CONCLUSION

This is the first registry-based nationwide study of osteogenesis imperfecta patients in Türkiye, providing important characteristics of the disease. Together with the help of the ongoing development of national health database systems, precision in patient identification would yield substantial benefits in terms of management of osteogenesis imperfecta.

Conjugated linoleic acid and glucosamine supplements may prevent bone loss in aging by regulating the RANKL/RANK/OPG pathway

The skeleton is a living organ that undergoes constant changes, including bone formation and resorption. It is affected by various diseases, such as osteoporosis, osteopenia, and osteomalacia. Nowadays, several methods are applied to protect bone health, including the use of hormonal and non-hormonal medications and supplements. However, certain drugs like glucocorticoids, thiazolidinediones, heparin, anticonvulsants, chemotherapy, and proton pump inhibitors can endanger bone health and cause bone loss. New studies are exploring the use of supplements, such as conjugated linoleic acid (CLA) and glucosamine, with fewer side effects during treatment. Various mechanisms have been proposed for the effects of CLA and glucosamine on bone structure, both direct and indirect. One mechanism that deserves special attention is the regulatory effect of RANKL/RANK/OPG on bone turnover. The RANKL/RANK/OPG pathway is considered a motive for osteoclast maturation and bone resorption. The cytokine system, consisting of the receptor activator of the nuclear factor (NF)-kB ligand (RANKL), its receptor RANK, and its decoy receptor, osteoprotegerin (OPG), plays a vital role in bone turnover. Over the past few years, researchers have observed the impact of CLA and glucosamine on the RANKL/RANK/OPG mechanism of bone turnover. However, no comprehensive study has been published on these supplements and their mechanism. To address this gap in knowledge, we have critically reviewed their potential effects. This review aims to assist in developing efficient treatment strategies and focusing future studies on these supplements.

The growth-friendly surgical treatment of scoliosis in children with osteogenesis imperfecta using distraction-based instrumentation

PURPOSE

The study was undertaken to determine the feasibility of growth-friendly distraction-based surgery in children with OI.

METHODS

Two multi-center databases were queried for children with OI who had undergone GR or VEPTR surgery. Inclusion criteria were a minimum 2-year follow-up and three lengthening procedures following the initial implantation. Details of the surgical techniques, surgical complications, and radiographic measurements of deformity correction, T1-T12 and T1-S1 elongation and growth were recorded.

RESULTS

Five patients were identified. There was one patient with type I OI and two patients each with type III and type IV. Four patients had GR constructs and one a VEPTR construct. The initial scoliosis deformity averaged 80° (70°-103°), and the subsequent corrections averaged 32% for initial correction, 48% at last follow-up, and 54% for the two patients that had a final fusion. The T1-T12 and T1-S1 growth averaged 31 mm and 44 mm respectively, and yearly growth averaged 4 mm and 6 mm, respectively. Growth was notably much less in those with more severe disease. There were 13 complications in 4 patients. Nine of the 10 surgical complications were anchor failures which were corrected in 7 planned and 2 un-planned procedures. Significant migration occurred in one patient with severe OI type III.

CONCLUSION

The results varied in this heterogeneous population. In general, satisfactory deformity corrections were obtained and maintained, modest growth was obtained, and complications were similar to those reported in other series of growth-friendly surgery. Limited growth and significant anchor migration are to be anticipated in this population.

LEVEL OF EVIDENCE

IV.

Osteogenesis imperfecta: an update on clinical features and therapies

Osteogenesis imperfecta (OI) is an inherited skeletal dysplasia characterized by bone fragility and skeletal deformities. While the majority of cases are associated with pathogenic variants in COL1A1 and COL1A2, the genes encoding type I collagen, up to 25% of cases are associated with other genes that function within the collagen biosynthesis pathway or are involved in osteoblast differentiation and bone mineralization. Clinically, OI is heterogeneous in features and variable in severity. In addition to the skeletal findings, it can affect multiple systems including dental and craniofacial abnormalities, muscle weakness, hearing loss, respiratory and cardiovascular complications. A multi-disciplinary approach to care is recommended to address not only the fractures, reduced mobility, growth and bone pain but also other extra-skeletal manifestations. While bisphosphonates remain the mainstay of treatment in OI, new strategies are being explored, such as sclerostin inhibitory antibodies and TGF beta inhibition, to address not only the low bone mineral density but also the inherent bone fragility. Studies in animal models have expanded the understanding of pathomechanisms of OI and, along with ongoing clinical trials, will allow to develop better therapeutic approaches for these patients.

The effect of bisphosphonate medication on orthodontics and orthognathic surgery in patients with osteogenesis imperfecta

Introduction: Osteogenesis imperfecta (OI) is a genetic disease that primarily affects bone formation and metabolism. Craniofacial malformations belong to the broad spectrum of the OI phenotype. The introduction of bisphosphonate medications was intended to counteract the significant brittleness of the bones of OI patients. In connection with the application of bisphosphonates, drug-associated osteonecrosis of the jaw has become known as an undesirable effect of the therapeutically intended reduction of osteoclast activity. Originally, the pharmacological inhibition of bone loss was mainly used in oncological therapy. For some time now, osteoporosis has also been treated with substances that inhibit bone resorption.

In OI, malposition of the jaws is relatively common, in particular retrognathia of the maxilla and progeny of the mandible. The literature discloses complications of orthognathic surgery in OI patients. Previous literature reviews suggest that bisphosphonate medication has no significant impact on the performance of and healing after oral surgery in OI patients.

Materialandmethods: An essential prerequisite of a therapy adapted to the patient’s condition is the knowledge of the patient's medical history. This case report describes the orthodontic-surgical treatment of an OI patient and the treatment experience derived in dealing with the condition. The unusual circumstance of this case is that the patient had concealed both his underlying disease and his medication during the current treatment period. In addition, the relevant literature is evaluated for combining the keywords OI, orthodontic therapy, bisphosphonates, and orthognathic surgery.

Results: Based on the literature and our own experience, it is concluded that orthodontic treatment with bisphosphonate medication can also be carried out in OI patients. However, considerably greater forces and longer time intervals should be scheduled for each treatment. Orthognathic surgery with bisphosphonate medication turned out to be uncomplicated in our own case, considering the underlying disease in the planning of surgical procedures. However, there have been very few reports of OI patients in whom orthodontic-surgical treatment of jaw malformation has been performed with bisphosphonate medication.

Conclusion: Taking into account the reported experience of severe complications of orthognathic surgery, the multiple documented adjustments to the treatment strategy of OI patients should be taken seriously. The basic condition of therapy adapted to the disease is that the patient informs the practitioner in an appropriate manner about his or her state of health.

The Effects of Long-term Use of Nitrogen-containing Bisphosphonates on Fracture Healing

Nitrogen-containing bisphosphonates (N-BPs) are pharmaceutical agents that have been used for many years to treat osteoporosis, multiple myeloma, Paget's disease, metastatic bone disease, and a variety of other diseases in which bone mineral density is reduced. Given that N-BPs inhibit bone resorption, an important stage in the fracture healing process, they have been extensively studied in preclinical models for their activity. In animal models, treatment with N-BPs is associated with a larger callus formation in fracture area and delay in remodeling from primary woven bone to lamellar bone, but there is no delay in formation of the fracture callus. In humans, all existing evidence suggest that initiating treatment with N-BPs, after upper and lower limb fractures, does not appear to have a significant effect on fracture healing. Rarely, patients with long-term use of N-BPs may develop "atypical fractures" and delay in their healing. Therefore, this clinical condition is not fully understood and many questions remain unanswered. Similarly, there are few studies about the benefits of stopping a long-term treatment with them, if a fracture occurs. Although most studies support that chronic N-BP therapy may lead to fracture healing delay, this is not fully documented. On the other hand, there are studies that are in complete disagreement with them. All of the above suggest that there is a need for more detailed future research into larger patient populations and different types of fractures, with sufficient data on the type, dosage, route and duration of administration of N-BPs, and the control methods of fracture healing, in order to have a safe final conclusion on the effect of their long-term administration in this highly complex process.

Percutaneous screw fixation of fractured neck of femur in a teenage girl with osteogenesis imperfecta. A case report

INTRODUCTION

Neck of femur fracture in osteogenesis imperfecta is rarely reported. The management is uncertain and always reported as difficult. Clinical outcomes are not well described.

CASE PRESENTATION

A teenage girl, who is known to have osteogenesis imperfecta, sustained neck of femur fracture in the presence of a previously inserted implant. She was treated by percutaneous screw fixation. In both immediate and long term follow up, our patient had satisfactory outcome and return to pre-fracture functional status.

DISCUSSION

Dealing with fragility fracture in small abnormal hips is challenging especially, in the presence of a retained implant in- situ. Intra-operative difficulty were encountered during positioning, reduction, and screw insertion attempt.

CONCLUSION

This rare case illustrates the anticipated difficulties in managing neck of femur fracture in osteogenesis imperfect patients. It also emphasize on the importance of surgical fixation to control pain and allow for healing in anatomically functional position.

Mid-term Results of Femoral and Tibial Osteotomies and Fassier-Duval Nailing in Children With Osteogenesis Imperfecta

BACKGROUND

Patients with osteogenesis imperfecta (OI) have significant burden of both fractures and bony deformities. The present approach to care in this disorder is a combination of surgical care with intramedullary rod fixation, cyclic bisphosphonate therapy, and rehabilitation with goal of maximizing patient function and quality of life.

METHODS

Retrospective chart review identified 58 children with OI who had realignment osteotomies with Fassier-Duval (FD) intramedullary nailing of the lower extremity by a single surgeon. This is a consecutive series treated between 2003 and 2010. Postoperatively, patients were followed up clinically and radiologically. Motor function was assessed using the Brief Assessment of Motor Function score and the walking scale subset of the Gillette Functional Assessment Questionnaire.

RESULTS

Fifty-eight patients had 179 lower extremity FD intramedullary rods placed. This technique allowed for intervention on multiple long bones, with 29% having bilateral femur and tibial rodding in the same procedure. Revisions were required in 53% of patients, which occurred at a mean time of 52 months after initial rodding surgery. In most cases, revision surgery was related to patient growth and subsequent fracture, although rod migration did occur in a minority of patients. Nonunion or incomplete union was 14.5% in this series. Bisphosphonate infusion was not postponed after surgical procedures. Patients had improvement in mobility status at the latest follow-up.

CONCLUSIONS

This series lends evidence to the medium-term utility of FD intramedullary rods as an effective and less invasive platform for stabilization and correction of deformity in long bones of patients with OI. Relatively low blood loss and relatively short hospitalizations were noted. Nonunion rate was comparable with existing literature noting that our patients did not have postsurgical postponement of bisphosphonate therapy.

LEVEL OF EVIDENCE

Therapeutic study to investigate the results of treatment with FD rods. Retrospective case series model of Level IV evidence quality.

EFFECTS OF LONG-TERM ALENDRONATE TREATMENT ON A LARGE SAMPLE OF PEDIATRIC PATIENTS WITH OSTEOGENESIS IMPERFECTA

OBJECTIVE

Osteogenesis imperfecta (OI) is a group of inherited diseases characterized by reduced bone mass, recurrent bone fractures, and progressive bone deformities. Here, we evaluate the efficacy and safety of long-term treatment with alendronate in a large sample of Chinese children and adolescents with OI.

METHODS

In this prospective study, a total of 91 children and adolescents with OI were included. The patients received 3 years' treatment with 70 mg alendronate weekly and 500 mg calcium daily. During the treatment, fracture incidence, bone mineral density (BMD), and serum levels of the bone turnover biomarkers (alkaline phosphatase [ALP] and cross-linked C-telopeptide of type I collagen [β-CTX]) were evaluated. Linear growth speed and parameters of safety were also measured.

RESULTS

After 3 years of treatment, the mean annual fracture incidence decreased from 1.2 ± 0.8 to 0.2 ± 0.3 (P<.01). BMD at the lumbar spine and femoral neck significantly increased by 74.6% and 39.5%, with their BMD Z-score increasing from -3.0 to 0.1 and from -4.2 to -1.3, respectively (both P<.01 vs. baseline). In addition, serum ALP and β-CTX levels decreased by 35.6% and 44.3%, respectively (both P<.05 vs. baseline). Height significantly increased, but without an obvious increase in its Z-score. Patient tolerance of alendronate was good.

CONCLUSION

Three years' treatment with alendronate was demonstrated for the first time to significantly reduce fracture incidence, increase lumbar spine and femoral neck BMD, and decrease bone turnover biomarkers in Chinese children and adolescents with OI.

ABBREVIATIONS

ALP = alkaline phosphatase β-CTX = cross-linked C-telopeptide of type I collagen BMD = bone mineral density BP = bisphosphonate DXA = dual-energy X-ray absorptiometry 25OHD = 25-hydroxyvitamin D OI = osteogenesis imperfecta PTH = parathyroid hormone.

Fracture healing: a consensus report from the International Osteoporosis Foundation Fracture Working Group

We used the RAND UCLA appropriateness method to decide appropriateness of use of osteoporosis medication after incident fracture and potential for fracture healing and make suggestions for trial design for clinical and preclinical research.

PURPOSE

To develop appropriateness criteria to assist in the use and study of osteoporosis medications in patients with recent fracture and in the potential use of osteoporosis medications to enhance delayed fracture healing. To promote further research by suggesting preclinical and clinical trial design for studies where fracture healing is the endpoint.

DESIGN

RAND/UCLA appropriateness method (RUAM).

PARTICIPANTS

A panel of experts, both members and non-members of the International Osteoporosis Foundation Fracture Working Group, were identified consisting of geriatricians, rheumatologists, orthopedists, endocrinologists, and internists. This resulted in a round 1 panel of 15 panelists, round 2 panel of 15 members, and a round 3 panel of 14 members.

MAIN OUTCOME MEASURE

Agreement on statements and scenarios using RUAM. Three rounds of voting by panelists took place. Agreement in a third round was reached for 111 statements and scenarios, measured by median panel ratings and the amount of dispersion of panel ratings, based on the interpercentile range.

RESULTS

An expert panel validated a set of statements and scenarios about the use of osteoporosis medications after incident fracture and use of these medications to enhance delayed fracture healing and made recommendations for study designs to investigate the effect of osteoporosis medications on fracture healing.

CONCLUSIONS

The result of this exercise is intended to assist in improving patient care by identifying the appropriateness of use of osteoporosis medications after fracture and in fracture healing and to make suggestions for further preclinical and clinical research.

Autologous implantation of BMP2-expressing dermal fibroblasts to improve bone mineral density and architecture in rabbit long bones

Cell-mediated gene therapy may treat bone fragility disorders. Dermal fibroblasts (DFb) may be an alternative cell source to stem cells for orthopedic gene therapy because of their rapid cell yield and excellent plasticity with bone morphogenetic protein-2 (BMP2) gene transduction. Autologous DFb or BMP2-expressing autologous DFb were administered in twelve rabbits by two delivery routes; a transcortical intra-medullar infusion into tibiae and delayed intra-osseous injection into femoral drill defects. Both delivery methods of DFb-BMP2 resulted in a successful cell engraftment, increased bone volume, bone mineral density, improved trabecular bone microarchitecture, greater bone defect filling, external callus formation, and trabecular surface area, compared to non-transduced DFb or no cells. Cell engraftment within trabecular bone and bone marrow tissue was most efficiently achieved by intra-osseous injection of DFb-BMP2. Our results suggested that BMP2-expressing autologous DFb have enhanced efficiency of engraftment in target bones resulting in a measurable biologic response by the bone of improved bone mineral density and bone microarchitecture. These results support that autologous implantation of DFb-BMP2 warrants further study on animal models of bone fragility disorders, such as osteogenesis imperfecta and osteoporosis to potentially enhance bone quality, particularly along with other gene modification of these diseases.

Update on the evaluation and treatment of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a heritable bone fragility disorder that presents with a wide clinical phenotype spectrum: from perinatal lethality and severe deformities to very mild forms without fractures. Most cases of OI are due to autosomal dominant mutations of the type I collagen genes. A multidisciplinary approach with rehabilitation, orthopedic surgery, and consideration of medical therapy with bisphosphonates underpins current management. Greater understanding of the pathogenesis of OI may lead to novel, therapeutic approaches to help improve clinical symptoms of children with OI in the future.

Advances in the orthopedic management of osteogenesis imperfecta

The long-established study of osteogenesis imperfecta (OI) has opened a realm of scientific research surrounding connective tissue disorders. Over the past decade alone there have been vast advancements in the understanding of the underlying genetic variations of this disease, pharmacologic treatments, and the technological and surgical options for fracture deformity. It is important to appreciate the progressive nature of the advances concerning OI. This article aims to synthesize the expanding evolution of the field surrounding OI over the past decade.

Fracture healing with alendronate treatment in the Brtl/+ mouse model of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a heritable bone dysplasia characterized by increased skeletal fragility. Patients are often treated with bisphosphonates to attempt to reduce fracture risk. However, bisphosphonates reside in the skeleton for many years and long-term administration may impact bone material quality. Acutely, there is concern about risk of non-union of fractures that occur near the time of bisphosphonate administration. This study investigated the effect of alendronate, a potent aminobisphosphonate, on fracture healing. Using the Brtl/+ murine model of type IV OI, tibial fractures were generated in 8-week-old mice that were untreated, treated with alendronate before fracture, or treated before and after fracture. After 2, 3, or 5 weeks of healing, tibiae were assessed using microcomputed tomography (μCT), torsion testing, quantitative histomorphometry, and Raman microspectroscopy. There were no morphologic, biomechanical or histomorphometric differences in callus between untreated mice and mice that received alendronate before fracture. Alendronate treatment before fracture did not cause a significant increase in cartilage retention in fracture callus. Both Brtl/+ and WT mice that received alendronate before and after fracture had increases in the callus volume, bone volume fraction and torque at failure after 5 weeks of healing. Raman microspectroscopy results did not show any effects of alendronate in wild-type mice, but calluses from Brtl/+ mice treated with alendronate during healing had a decreased mineral-to-matrix ratio, decreased crystallinity and an increased carbonate-to-phosphate ratio. Treatment with alendronate altered the dynamics of healing by preventing callus volume decreases later in the healing process. Fracture healing in Brtl/+ untreated animals was not significantly different from animals in which alendronate was halted at the time of fracture.

Comparable outcomes in fracture reduction and bone properties with RANKL inhibition and alendronate treatment in a mouse model of osteogenesis imperfecta

We report a direct comparison of receptor activator of nuclear factor kappa B ligand (RANKL) inhibition (RANK-Fc) with bisphosphonate treatment (alendronate, ALN) from infancy through early adulthood in a mouse model of osteogenesis imperfecta. Both ALN and RANK-Fc decreased fracture incidence to the same degree with increases in metaphyseal bone volume via increased number of thinner trabeculae.

INTRODUCTION

The potential therapeutic benefit of RANKL inhibitors in osteogenesis imperfecta (OI) is under investigation. We report a direct comparison of RANKL inhibition (RANK-Fc) with bisphosphonate treatment (ALN) from infancy through early adulthood in a model of OI, the oim/oim mouse.

METHODS

Two-week-old oim/oim, oim/+, and wildtype (+/+) mice were treated with RANK-Fc 1.5 mg/kg twice per week, ALN 0.21 mg/kg/week or saline (n = 12-20 per group) for 12 weeks.

RESULTS

ALN and RANK-Fc both decreased fracture incidence (9.0 ± 3.0 saline 4.4 ± 2.7 ALN, 4.3 ± 3.0 RANK-Fc fractures per mouse). Serum TRACP-5b activity decreased to 65% after 1 month in all treated mice, but increased sacrifice with RANK-Fc to 130-200% at sacrifice. Metaphyseal density was significantly increased with ALN in +/+ and oim/oim mice (p < 0.05) and tended to increase with RANK-Fc in +/+ mice. No changes in oim/oim femur biomechanical parameters occurred with treatment. Both ALN and RANK-Fc significantly increased trabecular number (3.73 ± 0.77 1/mm for oim/oim saline vs 7.93 ± 0.67 ALN and 7.34 ± 1.38 RANK-Fc) and decreased trabecular thickness (0.045 mm ± 0.003 for oim/oim saline vs 0.034 ± 0.003 ALN and 0.032 ± 0.002 RANK-Fc) and separation in all genotypes (0.28 ± 0.08 mm for oim/oim saline vs 0.12 ± 0.010 ALN and 13 ± 0.03 RANK-Fc)., with significant increase in bone volume fraction (BVF) with ALN, and a trend towards increased BVF in RANK-Fc.

CONCLUSION

Treatment of oim/oim mice with either a bisphosphonate or a RANK-Fc causes similar decreases in fracture incidence with increases in metaphyseal bone volume via increased number of thinner trabeculae.

Bioavailability and short-term tolerability of alendronate in glucocorticoid-treated children

BACKGROUND

Children receiving glucocorticoids (GCs) are at an increased risk of fragility fractures. Conservative measures may be inadequate in treating low bone mass, giving rise to fractures in this population; as such, attention has turned to the use of bisphosphonates.

OBJECTIVE

The goal of this study was to evaluate the bioavailability and single-dose tolerability of alendronate (ALN) in children receiving a stable dose of GCs.

METHODS

Children (ages 4-17 years) receiving GC treatment for their chronic illnesses received intravenous (125 μg) and oral (35 mg) ALN in a 2-period, randomized crossover study, with doses separated by at least a 7-day washout period. Urine was collected for either 8 or 24 hours after drug administration to determine urinary excretion of ALN and bioavailability. Tolerability was assessed by continuous collection of adverse events reported during the study. The main outcome measures were total urinary excretion rates, oral bioavailability of ALN, and adverse events.

RESULTS

There were 12 patients in the 4- to 11-year-old group (mean age, 8.1 years; 5 girls) and 12 patients in the 12- to 17-year-old group (mean age, 14.3 years; 5 girls). The least-squares mean bioavailability (90% CI) for children aged 4 to 11 years (n = 12) was 0.43% (0.27-0.67) and for children aged 12 to 17 years (n = 12) it was 0.39% (0.26-0.60). The least-squares mean bioavailability for all ages combined was 0.41% (0.30-0.56), with no statistical difference between the 2 age groups. The total urinary excretion of ALN after the intravenous dose was similar between groups. Fifteen patients reported a total of 36 transient clinical nonserious adverse events, all of which were mild or moderate in intensity; the most common were headache (n = 13), abdominal pain (n = 3), limb, neck, or facial pain (n = 6), and ankle or knee swelling (n = 3).

CONCLUSIONS

The mean oral bioavailability of ALN was similar to previous pharmacokinetic studies in children with osteogenesis imperfecta and slightly lower than that observed in historical adult controls. Alendronate was generally well tolerated, with minor adverse events that resolved uneventfully. Elucidation of the full adverse-effect profile of this agent was limited by the single-dose nature of this study, and robust comparisons of the pharmacokinetics of ALN in different age groups may need a larger number of patients.

Orthognathic bimaxillary surgery in two patients with osteogenesis imperfecta and a review of the literature

Orthognathic surgery in patients with osteogenesis imperfecta is rare. Most cases result in a successful outcome with stable and good occlusion. Two patients with, probably severe types III and IV, and malocclusion class III with retrognathic maxilla and prognathic mandible, were treated with orthodontic treatment and bimaxillary surgical correction. The surgical outcome and follow up are presented together with a review of published cases of orthognathic surgery in patients with different types of osteogenesis imperfecta. The authors conclude that it is possible to perform combined orthodontic and orthognathic surgery in patients with osteogenesis imperfecta despite the greater risk of complications. The treatments were successful with follow up times of 5-6 years.

RANKL inhibition improves bone properties in a mouse model of osteogenesis imperfecta

Recently, a new class of agents targeting the receptor activator of nuclear factor-kappaB ligand (RANKL) pathway has been developed for the treatment of osteoporosis and other bone diseases. In the current study, inhibition of the RANKL pathway was evaluated to assess effects on "bone quality" and fracture incidence in an animal model of osteogenesis imperfect (OI), the oim/oim mouse. Juvenile oim/oim ( approximately 6 weeks old) and wildtype (+/+) mice were treated with either a RANKL inhibitor (RANK-Fc) or saline. After treatment, bone density increased significantly in the femurs of both genotypes. Femoral length decreased with RANK-Fc in +/+ mice. Geometric measurements at mid-diaphysis in the oim/oim groups showed increases in the ML periosteal and endosteal diameters and AP cortical thickness in the treated groups. Within +/+ groups, ML cortical thickness and ML femoral periosteal diameter were significantly increased with RANK-Fc. Biomechanical testing revealed increased stiffness in oim/oim and +/+ mice. Total strain was increased with treatment in the +/+ mice. Histologically, RANKL inhibition resulted in retained growth plate cartilage in both genotypes. The average number of fractures sustained by RANK-Fc-treated oim/oim mice was not significantly decreased compared to saline treated oim/oim mice. This preclinical study demonstrated that RANKL inhibition at the current dose improved density and some geometric and biomechanical properties of oim/oim bone, but it did not decrease fracture incidence. Further studies that address commencement of therapy at earlier time points are needed to determine whether this mode of therapy will be clinically useful in OI.

Clinical review 1: Bisphosphonate use in childhood osteoporosis

CONTEXT

As awareness of osteoporosis in childhood has increased, so have pressures to consider use of the pharmacological agents used to treat osteoporosis in adults. This review examines available research on the efficacy and safety of bisphosphonate therapy for pediatric osteoporosis.

EVIDENCE ACQUISITION

We reviewed the medical literature for key articles and consensus statements on the use of bisphosphonates in children through June 2008.

EVIDENCE SYNTHESIS

We compared reports using varying bisphosphonate agents, doses, and duration of therapy to treat osteogenesis imperfecta and a variety of secondary causes of osteoporosis in children. Conclusions drawn from a recently published Cochrane analysis and the consensus statements from experts in the field were considered as well.

CONCLUSIONS

Use of bisphosphonate therapy in pediatric patients remains controversial because of inadequate long-term efficacy and safety data. For this reason, many experts recommend limiting use of these agents to those children with recurrent extremity fractures, symptomatic vertebral collapse, and reduced bone mass. Current data are inadequate to support the use of bisphosphonates in children to treat reductions in bone mass/density alone. More research is needed to define appropriate indications for bisphosphonate therapy and the optimal agent, dose, and duration of use in pediatric patients.

Effects of bisphosphonates in children with osteogenesis imperfecta: an AACPDM systematic review

This systematic review of the effects of bisphosphonate treatment in children with osteogenesis imperfecta was conducted using the American Academy for Cerebral Palsy and Developmental Medicine methodology for developing systematic reviews of treatment interventions (Revision 1.1) 2004. Despite a large body of published literature, there have been only eight studies with a sufficiently high level of internal validity to be truly informative. These studies confirm improvement in bone density. Many, but not all studies, demonstrate reduction in fracture rate and enhanced growth. There has been extremely limited evaluation of broader treatment impacts such as deformity, need for orthopedic surgery, pain, functioning, or quality of life. Short-term side effects were minimal. Which medication and dosing regimen is optimal and how long patients should be treated are unclear. This body of evidence would be strengthened by a larger controlled trial, because many studies lacked adequate power to evaluate stated outcomes. These studies do not address the impacts of bisphosphonates in children with milder forms of osteogenesis imperfecta and severe forms that are not due to mutations in the type I pro-collagen gene (e.g. types VII and VIII). Additional research is needed into treatment of infants. More studies evaluating medication choices, optimal dosing, duration of treatment, post-treatment impacts, and long-term side effects are necessary.

Osteogenesis imperfecta: diagnosis and treatment

Osteogenesis imperfecta is a heritable disorder characterized by extremely fragile bones, blue sclerae, dentinogenesis imperfecta, hearing loss, and scoliosis. In 1979, Sillence classified the condition into four types based on genetic and clinical criteria. Three more classifications have subsequently been added. Diagnosis of osteogenesis imperfecta may be done prenatally (in severe cases), clinically, radiographically, or via biochemical or genetic examination. Medical treatment consists of bisphosphonate use, even in patients younger than age 2 years. Surgical treatment consists of internal splinting of long bones. Research is currently being done on the use of smart intramedullary rods (ie, composed of nitinol shape-memory alloy) for correction of bone deformity and on the use of bone marrow transplantation to increase osteoblast density, thereby reducing fracture frequency.

Surgical treatment of osteogenesis imperfecta: current concepts

PURPOSE OF REVIEW

The treatment of osteogenesis imperfecta requires a multidisciplinary team to maximize function and comfort, and decrease fracture incidence. Medical treatment with bisphosphonates has allowed for safer, more effective surgical management of children with osteogenesis imperfecta. The purpose of this review is to outline treatment indications and choices of surgical techniques based on recent clinical studies, and in addition to identify persistent clinical problems addressed in recent literature.

RECENT FINDINGS

Several new intramedullary rodding surgical techniques and modifications of older techniques have been developed to correct deformities of the long bones. These techniques decrease the trauma associated with surgical treatment. The newer techniques limit postoperative immobilization, enabling earlier rehabilitation, and allowing for treatment of multiple bones simultaneously.

SUMMARY

Recent medical and surgical advances have allowed improved safety, function and comfort in treating children with osteogenesis imperfecta. The selection of surgical techniques is dependent on surgeon experience, severity of disease and patient function, and availability of specific instrumentation. Intramedullary fixation rather than plating is preferred, and allowing early protected weight bearing and rehabilitation of children with ambulatory potential is the ideal goal.

Osteogenesis imperfecta

Osteogenesis imperfecta is a relatively common hereditary connective tissue disorder characterized by bone fragility and fractures. Other frequently affected tissues include tendons, ligaments, skin, sclera, teeth, and middle and inner ear. Molecular studies have demonstrated that most cases result from mutations affecting the genes responsible for the formation of type 1 collagen. The phenotypic presentation varies from mild to lethal. Commonly observed dental abnormalities include dentinogenesis imperfecta and malocclusion. Medical therapies using bisphosphonates have resulted in reduced fracture risk and decreased bone pain. To date, no cases of bisphosphonate-associated osteonecrosis have been reported. With appropriate precautions, the patient with osteogenesis imperfecta can tolerate and benefit from the delivery of necessary dental care to control oral disease, improve function, and improve esthetics.

Intravenous pamidronate therapy in osteogenesis imperfecta: response to treatment and factors influencing outcome

Pamidronate treatment has been shown to improve outcome in osteogenesis imperfecta (OI); however, factors influencing outcome are unclear. The present study was conducted to evaluate the response to pamidronate therapy with special emphasis on factors influencing outcome. Twenty children with OI treated with pamidronate were evaluated in a prospective, open clinical trial. Pamidronate (9 mg x kg(-1) x yr) was administered intravenously at the age of 4.5 +/- 4.2 years for 2.9 +/- 0.7 years (range, 2-3.8 years). Treatment led to increase in bone mineral density (BMD) Z score by 0.7 +/- 0.3 every year resulting in significant improvement in BMD Z score (from -4.6 +/- 1.1 to -2.5 +/- 1.1, P<0.001). BMD Z score was within the reference range (>-2) in 9 subjects (45%) at the last follow-up as against none at initiation of treatment (P<0.001). Fracture rate decreased significantly during treatment (3.3 +/- 1.4 to 0.8 +/- 0.9, P<0.001) with 8 subjects (40%) having no fracture during the treatment period. Significantly greater proportion (88.2%) of children were able to walk at last follow-up compared with those at initiation of treatment (45.4%). Increase in BMD Z score and final BMD Z score was not influenced by age at initiation of treatment, duration of treatment, or initial BMD Z score. Treatment before infancy (n=7) was associated with higher final subjective score (6.3 +/- 0.5 vs 4.9 +/- 1.5, P=0.03). Our study reiterates the efficacy of pamidronate in OI. The poorer response of our subjects may be related to compromised calcium and vitamin D status.

Alendronate treatment in osteogenesis imperfecta

AIMS

Osteogenesis imperfecta (OI) is a chronic, disabling condition characterized by bone fragility resulting from defective production of type I collagen. Pamidronate therapy is the most extensively studied treatment and has proved beneficial. Our objective was to evaluate the effect of alendronate, a more potent bisphosphonate than pamidronate, in OI.

MATERIALS AND METHODS

Three patients (age, 3-7 years; mean, 5 years) (one case, type III; 2 cases, type IV) have been given alendronate (0.3-0.56 mg/kg per day orally) for 2 years. Number of fractures, ambulation, height growth, and bone mineral density by dual-energy x-ray absorptiometry (DXA) were followed up.

RESULTS

Bone mineral density improved significantly after the 2-year alendronate treatment, which increased by 47.8% to 106.6% in the lumbar spine and by 24% to 51.4% in forearm bones. The z-score of lumbar spine DXA values increased from -5.26 +/- 0.84 to -3.1 +/- 0.59. The mean of fracture rates did not change significantly. Only one of the patients was highly limited in ambulation. She had curved legs and could not sit without support before the treatment. She improved to walk with help by the treatment. Serum parathormone and alkaline phosphatase concentrations did not change significantly. No side effect was detected in clinical and laboratory evaluations.

CONCLUSION

The study suggests that alendronate is a safe and well-tolerated drug and that it could increase bone density in children with OI, all of which encourage further studies with the bisphosphonates that are more potent than pamidronate and can be used orally. In addition, this study is the first report using the forearm bone mineral density measurement in OI.