Reference data for jumping mechanography in healthy children and adolescents aged 6-18 years.

OBJECTIVES: To present gender-specific pediatric normative data on the main parameters of muscle function assessed using jumping mechanography. METHODS: The study population included 796 non-selected Caucasian children and adolescents (432 girls and 364 boys) aged 6-19 years recruited from 6 primary schools and 3 high schools. Maximum peak power (Pmax) was examined by a single two-legged jump, and maximum force (Fmax) was examined by a multiple one-legged hopping. All measurements were performed using a portable force platform (Leonardo Mechanograph, Novotec). Pmax, Pmax/mass, Fmax and Fmax/body weight were analyzed as the main outcome parameters. LMS method was used to generate age- and weight-specific reference smooth curves. RESULTS: Both Pmax and Fmax were strongly dependent on age and weight in both genders (all p<0.001). In prepubertal children, there was no intergender difference in Pmax or Fmax. Both parameters steadily increased in boys and plateaued in girls aged >13 years. Whereas Pmax/mass was more dependent on anthropometric parameters, Fmax/BW remained nearly constant with respect to age and weight. CONCLUSIONS: These reference data are intended to assist clinicians in the assessment of muscle function by jumping mechanography in pediatric patients.

Prepubertal girls with Turner syndrome and children with isolated SHOX deficiency have similar bone geometry at the radius.

CONTEXT: The low bone mineral density (BMD) and alterations in bone geometry observed in patients with Turner syndrome (TS) are likely caused by hypergonadotropic hypogonadism and/or by haploinsufficiency of the SHOX gene. OBJECTIVE: Our objective was to compare BMD, bone geometry, and strength at the radius between prepubertal girls with TS and children with isolated SHOX deficiency (SHOX-D) to test the hypothesis that the TS radial bone phenotype may be caused by SHOX-D. DESIGN AND SETTING: This comparative cross-sectional study was performed between March 2008 and May 2011 in 5 large centers for pediatric endocrinology. PATIENTS: Twenty-two girls with TS (mean age 10.3 years) and 10 children with SHOX-D (mean age 10.3 years) were assessed using peripheral quantitative computed tomography of the forearm. MAIN OUTCOMES: BMD, bone geometry, and strength at 4% and 65% sites of the radius were evaluated. RESULTS: Trabecular BMD was normal in TS (mean Z-score = -0.2 ± 1.1, P = .5) as well as SHOX-D patients (mean Z-score = 0.5 ± 1.5, P = .3). At the proximal radius, we observed increased total bone area (Z-scores = 0.9 ± 1.5, P = .013, and 1.5 ± 1.4, P = .001, for TS and SHOX-D patients, respectively) and thin cortex (Z-scores = -0.7 ± 1.2, P = 0.013, and -2.0 ± 1.2, P < .001, respectively) in both groups. Bone strength index was normal in TS as well as SHOX-D patients (Z-scores = 0.3 ± 1.0, P = .2, and 0.1 ± 1.3, P = .8, respectively). CONCLUSIONS: The similar bone geometry changes of the radius in TS and SHOX-D patients support the hypothesis that loss of 1 copy of SHOX is responsible for the radial bone phenotype associated with TS.

Bone geometry and volumetric bone density at the radius in patients with isolated SHOX deficiency.

UNLABELLED: The short stature homeobox-containing gene (SHOX) plays an important role in bone development and growth. We aimed to assess bone geometry and volumetric bone mineral density at the radius in patients with isolated SHOX deficiency and to relate these bone parameters to the severity of disproportion between the upper and the lower body segment. 17 patients with isolated SHOX deficiency (median age 12.3 yrs, range 6.7-37.2, 12 children and 5 adults) were examined by peripheral quantitative CT (pQCT) at the non-dominant forearm. Results were expressed as Z-scores using published reference data. Linear regression analyses were performed to describe associations between pQCT parameters and the severity of disproportion expressed as sitting height to standing subischial leg height ratio. Trabecular volumetric bone mineral density (vBMD) at the distal radius was normal, whereas cortical vBMD was decreased (mean Z-scores 0.34±1.5, n.s., and -2.2±2.2, p<0.001, respectively). Total bone cross-sectional area was enlarged at the diaphysis (2.1±1.2, p<0.001), while cortical bone cross-sectional area was normal (-0.51±1.4, n.s.). Consequently, cortical thickness was decreased (-1.2±1.3, p<0.01). The polar strength-strain index as a surrogate of long bone strength was normal (0.40±1.4, n.s.). We found no associations between pQCT parameters and the severity of disproportion. CONCLUSIONS: Patients with isolated SHOX deficiency are characterized by decreased cortical vBMD and cortical thickness and enlarged diaphysis. As similar changes have been described in girls with Turner syndrome, these findings suggest that haploinsufficiency of SHOX could cause characteristic skeletal anomalies at the radius.

Boys with haemophilia have low trabecular bone mineral density and sarcopenia, but normal bone strength at the radius.

Although a decreased areal bone mineral density (BMD) has been reported in patients with haemophilia, data are lacking that would reflect the three-dimensional structure of the bone and the muscle-bone relationship. We aimed to assess volumetric BMD, bone geometry and muscle-bone phenotype in boys with haemophilia, and to describe the association between clinical characteristics of haemophilia and bone quality and structure. A cross-sectional study was conducted in 41 boys with haemophilia (mean age 12.4, range 6.6-19.8 years) using peripheral quantitative CT (pQCT) at the nondominant forearm. Results were transformed into Z-scores using previously published reference data. Significant differences were tested by one-sample t-test or sign test. Two-sample t-test and anova were used to compare results between subgroups of patients divided according to the severity of the disease, the fracture history and the number of joint and muscle bleedings. Boys with haemophilia had a decreased trabecular volumetric BMD (mean Z-score -0.5, P < 0.01), while their cortical volumetric BMD was increased (mean Z-score 0.4, P < 0.05). The volumetric bone mineral content and the bone geometry at the radial diaphysis were normal when adjusted for patients' shorter body height. Muscle area was decreased (mean Z-score -1.0, P < 0.001), irrespective of age. No association was observed of bone quality parameters and bone geometry with the disease severity, fracture history or number of bleedings. Bone strength measured at the diaphysis of the radius is not impaired in boys with haemophilia. The finding of the decreased trabecular bone density can be most likely attributed to their sarcopenia.