Mild to moderate cystic fibrosis is not associated with increased fracture risk in children and adolescents

The use of DXA for early detection of pediatric cystic fibrosis-related bone disease

BACKGROUND

Cystic fibrosis (CF)-related bone disease (CFBD) is seen in adults and can be associated with respiratory illness and malnutrition. There is limited and conflicting data regarding CFBD in pediatric CF. With longer life expectancy and promotion of disease prevention, pediatric CFBD demands further investigation.

METHODS

Our center initiated a quality improvement (QI) project from April 2016 to December 2018 to improve CFBD screening in patients 8 years or older, per current CF Foundation (CFF) guidelines. Our team formulated a dual-energy X-ray absorptiometry (DXA) scan algorithm based upon degree of bone mineral density (BMD); shared CFBD guideline recommendations in our quarterly newsletter; and ordered scans for eligible patients at weekly review meetings. We reviewed DXA results from 141 patients after institutional review board approval and gathered data including comorbidities, genetics, anthropometric measures, medication exposure, and relevant serum studies.

RESULTS

Fifty-three percent of our patients had normal BMD (n = 75). Seventeen patients (12%) had a Z score ≤ -2. Patients with lower BMD also had lower mean forced expiratory volume (FEV₁ ) percent predicted (FEV₁ %) (p < 0.001) as well as lower body mass index % (p = 0.001). Patients with lower BMD were overall older at time of DXA (p = 0.016). During study duration, 13 patients who had abnormal DXA results underwent repeat DXAs after physical therapy; 11 of the 13 showed improvement in DXA results.

CONCLUSIONS

A DXA scan is a useful screening tool and can be used to identify pediatric patients who could benefit from further therapy and interventions to preserve adequate bone health and avoid further loss. QI initiatives can lead to improved screening and diagnosis and earlier intervention such as physical therapy. Further studies are needed to better understand the utility of physical therapy in children with CF.

Endocrine Complications of Cystic Fibrosis

Endocrine comorbidities have become increasingly important medical considerations as improving cystic fibrosis (CF) care increases life expectancy. Although the underlying pathophysiology of CF-related diabetes remains elusive, the use of novel technologies and therapeutics seeks to improve both CF-related outcomes and quality of life. Improvements in the overall health of those with CF have tempered concerns about pubertal delay and short stature; however, other comorbidities such as hypogonadism and bone disease are increasingly recognized. Following the introduction of highly effective modulator therapies there are many lessons to be learned about their long-term impact on endocrine comorbidities.

Orthopedic Manifestations of Cystic Fibrosis

Cystic fibrosis (CF) is a relatively common disease seen in Whites of northern European descent. Classically, it was a lethal disease and uncommon for the orthopedic practitioner to interact with CF patients. Recent pharmaceutical breakthroughs targeting the CF transmembrane conductance regulator (CFTR) gene have significantly prolonged patient life expectancy. This makes it increasingly likely that orthopedic surgeons will encounter CF patients in their clinic. In this article, the authors discuss pertinent musculoskeletal manifestations of the CF population, including the increased risk of decreased bone mineral density and bone mineral content, muscle deconditioning, spinal kyphosis, fractures, and elevated systemic inflammation predisposing these individuals to CF-related arthralgia. The diagnoses are grouped into subspecialties (arthroplasty, pediatrics, spine, sports, and trauma) most likely to evaluate the patient. Additionally, the authors review treatment options for these conditions and discuss the need for these patients to be seen in the perioperative period by their CF care team for patient optimization due to their diminished pulmonary function. Interspersed with this literature review, the authors present 2 unique cases. The first case details a patient with pain over her spine due to multilevel spinous process bursitis caused by a high-frequency chest wall oscillation system, which masquerades as an infection. The second case is a non-contact midsubstance rectus femoris tear in an athlete. These cases highlight the need for increased vigilance for uncommon diagnoses in the CF patient population. [Orthopedics. 2021;44(3):e440-e445.].

The clinical features that contribute to poor bone health in young Australians living with cystic fibrosis: A recommendation for BMD screening

BACKGROUND

For Australians living with cystic fibrosis (CF), increased longevity means greater consideration needs to be given to long-term endocrine sequelae such as CF-related bone disease. Deficits in bone mass accrual are most likely to occur during childhood and adolescence. Current guidelines in Australia suggest repeat dual-energy X-ray absorptiometry (DXA) scans every 2 years. This study aims to stratify clinical factors that determine future bone health in the Australian CF population and use this to guide a more streamlined approach to bone health screening.

METHODS

This study was a retrospective audit of all patients diagnosed with CF who were treated at the Royal Children's Hospital Melbourne, Australia from 2000 to 2016 (n = 453). Two hundred and two patients had a DXA scan in the study period (191 with height-adjusted data) and 111 patients had more than one scan (108 with height-adjusted data). An investigation into the associations between bone mineral density (BMD) Z score and potential risk factors was conducted using DXA and historical data.

RESULTS

The main predictor of future BMD was the previous BMD Z score (p < .001). Other factors found to be determinants of BMD included nutritional status, lung function (FEV₁ ), age, history of previous fracture, oral corticosteroid use, and the number of hospital admissions. However, after adjusting for previous BMD, evidence of an association remained only with nutritional status, FEV₁ , and number of hospital admissions.

CONCLUSION

Second yearly scans may be unnecessary in children with an adequate DXA score on the initial scan who remain clinically stable. However, clinical deterioration in those whose BMD was previously normal, may require closer monitoring of bone health. We propose a guideline for the frequency of DXA monitoring in relation to clinical risk factors.

A retrospective analysis of longitudinal changes in bone mineral content in cystic fibrosis

BACKGROUND

We aimed to describe the longitudinal changes in bone mineral content and influencing factors, in children with cystic fibrosis (CF).

METHODS

One hundred children (50 females) had dual X-ray absorptiometry (DXA) performed. Of these, 48 and 24 children had two to three scans, respectively over 10 years of follow-up. DXA data were expressed as lumbar spine bone mineral content standard deviation score (LSBMCSDS) adjusted for age, gender, ethnicity and bone area. Markers of disease, anthropometry and bone biochemistry were collected retrospectively.

RESULTS

Baseline LSBMCSDS was >0.5 SDS in 13% children, between -0.5; 0.5 SDS, in 50% and ≤-0.5 in the remainder. Seventy-eight percent of the children who had baseline LSBMCSDS >-0.5, and 35% of the children with poor baseline (LSBMCSDS<-0.5), showed decreasing values in subsequent assessments. However, mean LS BMC SDS did not show a significant decline in subsequent assessments (-0.51; -0.64; -0.56; p=0.178). Lower forced expiratory volume in 1 s percent (FEV1%) low body mass index standard deviation scores (BMI SDS) and vitamin D were associated with reduction in BMC.

CONCLUSIONS

Bone mineral content as assessed by DXA is sub-optimal and decreases with time in most children with CF and this study has highlighted parameters that can be addressed to improve bone health.

[Insights into cystic fibrosis-related bone disease]

With the increasing life expectancy of patients with cystic fibrosis (CF), prevalence of late complications such as CF-related bone disease (CFBD) has increased. It was initially described in 24% of the adult population with CF and has also been reported in the pediatric population. CFBD is multifactorial and progresses in different steps. Both decreased bone formation and increased bone resorption (in different amounts) are observed. CFBD is likely primitive (directly related to the CFTR defect itself), but is also worsened by acquired secondary factors such as lung infections, chronic inflammation, denutrition, vitamin deficiency, and decreased physical activity. CFBD may be clinically apparent (i.e., mainly vertebral and costal fractures), or clinically asymptomatic (therefore corresponding to abnormalities in bone density and architecture). CFBD management mainly aims to prevent the occurrence of fractures. Prevention and regular monitoring of bone disease as early as 8 years of age is of the utmost importance, as is the control of possible secondary deleterious CFBD factors. New radiological tools, such as high-resolution peripheral quantitative computed tomography, allow an accurate evaluation of cortical and trabecular bone micro-architecture in addition to compartmental density; as such, they will likely improve the assessment of the bone fracture threat in CF patients in the near future.

Evaluation of factors related to bone disease in Polish children and adolescents with cystic fibrosis

PURPOSE

The aim of the study was to evaluate factors related to bone formation and resorption in Polish children and adolescents with cystic fibrosis and to examine the effect of nutritional status, biochemical parameters and clinical status on bone mineral density.

MATERIALS AND METHODS

The study group consisted of 100 children and adolescents with cystic fibrosis with a mean age 13.4 years old. Anthropometric measurements, included body height, body mass and body mass index (BMI); bone mineral densitometry and biochemical testing were performed. Bone mineral density was measured using a dual-energy X-ray absorption densitometer. Biochemical tests included serum calcium, phosphorus, parathyroid hormone and vitamin D concentrations, as well as 24-h urine calcium and phosphorus excretion. Pulmonary function was evaluated using FEV1%, and clinical status was estimated using the Shwachman-Kulczycki score.

RESULTS

Standardized body height, body mass and BMI were significantly lower than in the reference population. Mean serum vitamin D concentration was decreased. Pulmonary disease was generally mild, with a mean FEV1% of 81%. Multivariate linear regression revealed that the only factors that had a significant effect on bone marrow density were BMI and FEV1%. There were no significant correlations between bone mineral density and the results of any of the biochemical tests performed.

CONCLUSIONS

Nutritional status and bone mineral density were significantly decreased in children and adolescents with cystic fibrosis. In spite of abnormalities in biochemical testing, the factors that were found to have the strongest effect on bone mineral density were standardized BMI and clinical status.

Cystic fibrosis-related bone disease: insights into a growing problem

PURPOSE OF REVIEW

This review will describe the clinical significance, pathogenesis and treatment of cystic fibrosis related bone disease (CFBD).

RECENT FINDINGS

CFBD continues to increase as the life expectancy of individuals with cystic fibrosis increases. According to clinical guidelines, individuals with cystic fibrosis should be initially screened at the age of 18 years via dual-energy x-ray absorptiometry, if not done so previously. The underlying pathogenesis of CFBD appears to be multifactorial, but increasing data imply a direct impact by the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR deficiency and/or dysfunction impair osteoblast activity and differentiation, and indirectly promote osteoclast formation. Unfortunately, once diagnosed with CFBD, few cystic fibrosis tested medical therapies exist.

SUMMARY

CFBD is an increasingly recognized complication that has a significant impact on the overall health of the individual. Recommendations to identify patients with cystic fibrosis who are at risk for fracture using dual-energy x-ray absorptiometry have been established. Therapeutic agents directly studied in patients with cystic fibrosis are limited to bisphosphonates, although other potential treatment agents exist. Finally, an improved understanding of the pathologic mechanisms will aid in the study and development of therapies.

[Endocrine complications of cystic fibrosis in childhood]

Since the 20 last years, the median age of survival has dramatically improved in children suffering from cystic fibrosis and complications such as growth retardation, pubertal delay and low bone mineral density are now more often than not observed in affected adolescents. The severity of the disease and the poor nutritional status due to pancreatic insufficiency and malabsorption are commonly implicated but recent data suggest that the disease could also play a role though the alteration of the chlore chanel (CFTR). Furthermore an increase prevalence of glucose intolerance and diabetes due to the progressive β cells destruction is observed in these children that make the life sometimes difficult for these adolescents already affected by an heavy chronic disease. The monitoring of the children should thus now become pluridisciplinary and include regular clinical evaluation of height and pubertal status, mineral bone density by DEXA and OGTT every two years since 10 years of age. Therefore, in addition to the standard treatment of cystic fibrosis is now added the vitamin D supplementation, the subcutaneous insulin therapy and may be the growth hormone that could be a new therapeutic demonstrating beneficial effects in these chronic disease. However further studies need to be performed to improve the management of these new endocrine complications more and more frequent in children and adolescents suffering from cystic fibrosis.

Update on cystic fibrosis-related bone disease: a special focus on children

A high prevalence of low bone mineralization is documented in adult patients with cystic fibrosis (CF). Osteopenia is present in up to 85% of adult patients and osteoporosis in 10% to 34%. In children, study results are discordant probably because of comparisons to different control populations and corrections for bone size in growing children. Malnutrition, inflammation, vitamin D and vitamin K deficiency, altered sex hormone production, glucocorticoid therapy, and physical inactivity are well known risk factors for poor bone health. Puberty is a critical period for bone mineralization and requires a careful follow-up to achieve optimal bone peak mass. Strategies for optimizing bone health, such as monitoring bone mineral density (BMD) and providing preventive care are necessary from childhood through adolescence to minimize CF-related bone disease in adult CF patients.

Revised pediatric reference data for the lateral distal femur measured by Hologic Discovery/Delphi dual-energy X-ray absorptiometry

Lateral distal femur (LDF) scans by dual-energy X-ray absorptiometry (DXA) are often feasible in children for whom other sites are not measurable. Pediatric reference data for LDF are not available for more recent DXA technology. The objective of this study was to assess older pediatric LDF reference data, construct new reference curves for LDF bone mineral density (BMD), and demonstrate the comparability of LDF BMD to other measures of BMD and strength assessed by DXA and by peripheral quantitative computed tomography (pQCT). LDF, spine and whole body scans of 821 healthy children, 5-18 yr of age, recruited at a single center were obtained using a Hologic Discovery/Delphi system (Hologic, Inc., Bedford, MA). Tibia trabecular and total BMD (3% site), cortical geometry (38% site) (cortical thickness, section modulus, and strain-strength index) were assessed by pQCT. Sex- and race-specific reference curves were generated using LMS Chartmaker (LMS Chartmaker Pro, version 2.3. Tim Cole and Huiqi Pan. Copyright 1997-2006, Medical Research Council, UK) and Z-scores calculated and compared by correlation analysis. Z-scores for LDF BMD based on published findings demonstrated overestimation or underestimation of the prevalence of low BMD-for-age depending on the region of interest considered. Revised LDF reference curves were generated. The new LDF Z-scores were strongly and significantly associated with weight, body mass index, spine and whole body BMD Z-scores, and all pQCT Z-scores. These findings demonstrate the comparability of LDF measurements to other clinical and research bone density assessment modes, and enable assessment of BMD in children with disabilities, who are particularly prone to low trauma fractures of long bones, and for whom traditional DXA measurement sites are not feasible.

Murine model for cystic fibrosis bone disease demonstrates osteopenia and sex-related differences in bone formation

As the incidence of cystic fibrosis (CF) bone disease is increasing, we analyzed CF transmembrane conductance regulator (CFTR) deficient mice (CF mice) to gain pathogenic insights. In these studies comparing adult (14 wk) CF and C57BL/6J mice, both bone length and total area were decreased in CF mice. Metaphyseal trabecular and cortical density were also decreased, as well as diaphyseal cortical and total density. Trabecular bone volume was diminished in CF mice. Female CF mice revealed decreased trabecular width and number compared with C57BL/6J, whereas males demonstrated no difference in trabecular number. Female CF mice had reduced mineralizing surface and bone formation rates. Conversely, male CF mice had increased mineralizing surface, mineral apposition, and bone formation rates compared with C57BL/6J males. Bone formation rate was greater in males compared with female CF mice. Smaller bones with decreased density in CF, despite absent differences in osteoblast and osteoclast surfaces, suggest CF transmembrane conductance regulator influences bone cell activity rather than number. Differences in bone formation rate in CF mice are suggestive of inadequate bone formation in females but increased bone formation in males. This proanabolic observation in male CF mice is consistent with other clinical sex differences in CF.

Deficits in bone mineral content in children and adolescents with cystic fibrosis are related to height deficits

Despite reports of decreased bone density, children with mild to moderate cystic fibrosis (CF)-associated pulmonary disease do not have increased fracture rates. Short stature and delayed puberty complicate interpretations of bone mineral status in many children with chronic diseases. This study sought to characterize bone mineral content (BMC) in children with CF and determine its relationship to growth, body composition, and disease severity. Dual-energy X-ray absorptiometry measurements of whole body BMC (WB-BMC), spine BMC (Sp-BMC), and lean body mass (LBM) were converted to Z-scores in 82 CF and 322 healthy children. Effects of growth, body composition, and CF-disease characteristics on BMC were determined using linear regression. Children with CF had lower weight, height (HT), BMI, and LBM-Z. Females with CF had lower (p<0.001) WB-BMC-Z (-1.1+/-1.1) and Sp-BMC-Z (-0.9+/-1.1) than controls. Following adjustment for height standard deviation score (HT-Z), deficits were absent. Males with CF had lower (p<0.001) WB-BMC-Z (-1.3+/-0.9) and Sp-BMC-Z (-0.9+/-1.3). Following adjustment for HT-Z, WB-BMC-Z deficits were attenuated and Sp-BMC-Z deficits absent. HT-Z, LBM-Z, and pulmonary function had independent effects on WB-BMC-Z and Sp-BMC-Z. BMC deficits are related to altered body size, reduced LBM, and pulmonary function in children with CF. Interventions targeting improved growth, muscle mass, and pulmonary function may benefit bone health in CF.

Osteoporosis in children and adolescents

In recent years, the issue of low bone density in children and adolescents has attracted much attention. The classical definition of osteoporosis should be valid at any age, yet its practical applicability to children and adolescents remains a matter of debate and there is no consensus on a diagnosis based solely on the BMD value. The clinical relevance of uncomplicated low bone density in the young and its long-term consequences remain difficult to evaluate and there is only preliminary evidence that the BMD value is a predictor of fracture risk in growing subjects. Moreover, the interpretation of densitometric data in the young is difficult because the "normal" BMD values to be used for comparison are continuously changing with age, and in addition, depend on several variables, such as gender, body size, pubertal stage, skeletal maturation and ethnicity. Although Z-score values below -2 are generally considered a serious warning, most bone specialists make a diagnosis of osteoporosis in children and adolescents only in the presence of low BMD and at least one fragility fracture. The scope of this review is limited to presenting a picture of the available knowledge. The literature on fractures will be presented in detail, since fractures are one of the key elements in the debate. There are countless papers on fractures in childhood and adolescence, but very few of them attempt to identify fragility fractures, and still fewer develop the concept of osteoporosis in the young in relation to fractures. The different forms of primary and secondary osteoporosis, the more technical aspects of bone densitometry in pediatrics, and the delicate issue of treatment will be discussed only briefly.

Nutritional management of cystic fibrosis patients

PURPOSE OF REVIEW

We critique recent advances in nutritional care of patients with cystic fibrosis focusing on our understanding of the role of fecal elastase as a pancreatic function test, enzyme replacement therapy and bone health.

RECENT FINDINGS

Fecal elastase measured by the monoclonal antibody method is a useful screening test for delineating cystic fibrosis patients with pancreatic insufficiency (needing enzyme replacement therapy) from those with pancreatic sufficiency. Cutoff levels, however, have not been clearly defined, particularly in infancy. Newer enzyme products that attempt to improve the intralumenal intestinal pH with bicarbonate or using a combination of unprotected and enteric coated products fail to completely correct nutrient maldigestion. Compromised bone health in cystic fibrosis patients may be due to multiple factors including calcium, vitamin D, and vitamin K deficiencies and lung inflammation. Current recommendations for treatment of bone health in cystic fibrosis are not evidence-based.

SUMMARY

Fecal elastase is a useful marker of pancreatic function but limitations for this test exist. The presence of an acidic intestinal milieu and hitherto poorly defined intestinal factors may contribute to the failure of current enzyme preparations to correct nutrient assimilation in cystic fibrosis. The many factors that contribute to bone health must be evaluated when developing treatment strategies.

Update on maintaining bone health in cystic fibrosis

PURPOSE OF REVIEW

The high prevalence of decreased bone density in adults with cystic fibrosis is now well recognized, and guidelines for screening and treatment of cystic fibrosis-related bone disease have recently been published. This review summarizes the current best practices for optimizing bone health in cystic fibrosis and highlight recent findings that provide insight into the etiology of cystic fibrosis-related bone disease.

RECENT FINDINGS

Recent research suggests that cystic fibrosis-related bone disease actually starts during childhood, when individuals with cystic fibrosis fail to demonstrate normal bone calcium accretion. The failure to reach peak bone mass is made worse by increased osteoclast activity and bone resorption. This combination results in decreased bone density and an increased risk of fracture. Recent clinical studies suggest that multiple contributing factors need to be addressed in cystic fibrosis to optimize bone health: malnutrition, vitamin and mineral malabsorption, recurrent infections, inadequate sex hormones, and lack of exercise. Oral bisphosphonates have been demonstrated to be effective in cystic fibrosis and should be used when osteoporosis or progressive osteopenia is present.

SUMMARY

Research suggests cystic fibrosis-related bone disease actually begins during childhood, and guidelines now exist to aid in identifying and treating those with decreased bone density.

Childhood onset arthritis is associated with an increased risk of fracture: a population based study using the General Practice Research Database

BACKGROUND

Childhood onset arthritis is associated with low bone mass and strength.

OBJECTIVE

To determine whether childhood onset arthritis is associated with greater fracture risk.

METHODS

In a retrospective cohort study all subjects with onset of arthritis between 1 and 19 years of age in the United Kingdom General Practice Research Database were identified. As controls, all sex and age matched subjects from a practice that included a subject with arthritis were included. Incidence rate ratios (IRRs) for first fracture were generated using Mantel-Haenszel methods and Poisson regression.

RESULTS

1939 subjects with arthritis (51% female) and 207 072 controls (53% female) were identified. The median age at arthritis diagnosis was 10.9 years. A total of 129 (6.7%) first fractures were noted in subjects with arthritis compared with 6910 (3.3%) in controls over a median follow up of 3.90 and 3.95 years in the subjects with arthritis and controls, respectively. The IRR (95% confidence interval) for first fracture among subjects with arthritis, compared with controls, according to the age at the start of follow up were 1.49 (0.91 to 2.31) for age <10 years, 3.13 (2.21 to 4.33) at 10-15 years, 1.75 (1.18 to 2.51) at 15-20 years, 1.40 (0.91 to 2.08) at 20-45 years, and 3.97 (2.23 to 6.59) at >45 years.

CONCLUSIONS

Childhood onset arthritis is associated with a clinically significant increased risk of fracture in children, adolescents and, possibly, adults. Studies are urgently needed to characterise the determinants of structural bone abnormalities in childhood arthritis and devise prevention and treatment strategies.