CHAPTER 12 - Noninvasive Techniques for Bone Mass Measurement

Interest in pediatric bone health and osteoporosis has intensified considerably since the early 1990s. This change reflects increased awareness that numerous pathways bring about early gains in bone strength which influence the risk of fracture throughout life. This chapter discusses the mechanisms by which genetic and acquired disorders of childhood can compromise the development of bone strength, and reviews the current status of approaches to the diagnosis, treatment and prevention of osteoporotic disorders of childhood.

Determinar los valores de densidad mineral ósea (DMO) en niños y adolescentes con afectación moderada y severa, por parálisis cerebral infantil (PCI) de nuestra área de referencia, y comparar estos valores con pacientes sanos.

Estudio de pronóstico de casos y controles para la valoración de la DMO en pacientes con PCI de 2 a 18 años pertenecientes a los grupos IV y V de la clasificación Gross Motor Function Classification System (GMFCS). Las mediciones de DMO se realizaron a nivel del fémur distal, se dividió esta región en 3 zonas siguiendo el protocolo de antebrazo.

En la muestra final de 69 pacientes se objetivan valores de DMO para cada una de las regiones estudiadas muy por debajo de los niveles de referencia. Existe una diferencia estadísticamente significativa (p < 0,05) entre los valores de DMO en los 2 subgrupos estudiados.

La mayor afectación desde el punto de vista neurológico en los pacientes del grupo V condiciona una situación de muy baja DMO respecto a pacientes de igual edad y sexo. En pacientes con PCI la adquisición de capital óseo no se realiza siguiendo el patrón de normalidad de la población sana.

To determine the bone mineral density (BMD) values in children and adolescents with moderate and severe infantile cerebral palsy (ICP) in our catchment area, and compare these values with a healthy population.

A prognostic study of cases and controls for the assessment of BMD in patients from 2 to 18 years old with infantile cerebral palsy belonging to the Gross Motor Function Classification System (GMFCS) Groups IV and V. The BMD measurements were performed at distal femur level, dividing this region into 3 areas following the forearm protocol.

The BMD for each of the three areas studied results in the final sample of 69 patients were much lower than the reference levels. There was a statistically significant difference (P<.05) between the BMD values in the two sub-groups studied.

The greater the involvement, from a neurological point of view, in patients classified as Group V shows a very low BMD compared to patients of similar sex and age. The acquisition of bone capital in patients with ICP does not follow the normal pattern of the healthy population.

Reduced bone mass measurements are often found in HIV-infected youths. Both in vitro and human studies demonstrated a role of antiretroviral treatment in determining bone mass alteration. Nevertheless, the data regarding the responsibility of different antiretroviral drugs on bone health in children and adolescents are highly controversial. The purpose of the current study was to relate antiretroviral treatment to bone mass measurements in a large cohort of HIV-infected children and adolescents. Bone mineral content (BMC) was measured in 86 HIV-infected youths (aged 4.8–22.1 years), and in 194 healthy controls (aged 4.9–21.9 years). Fifteen patients were naive to antiretroviral treatment, 11 were receiving a dual nucleoside reverse transcriptase inhibitor (NRTIs) combination, 32 a protease inhibitor (PI)-based antiretroviral treatment, and 28 a non-nucleoside reverse transcriptase inhibitor (NNRTIs)-based regimen. Comparisons between healthy and HIV-infected children and adolescents have been performed by multiple regression analyses to correct for differences in age, sex, and anthropometric measurements. Patients receiving a PI-based treatment had lumbar spine and whole body BMC values significantly lower than healthy children (P < 0.05). BMC measurements of patients on other therapeutic regimens or naive to antiretroviral treatment did not differ significantly from those of healthy children. Among patients receiving a PI-based regimen, those receiving full dose Ritonavir had significantly lower lumbar spine BMC values compared to other patients. Lumbar spine and whole body BMC measurements of patients receiving a Stavudine-containing regimen were lower compared to healthy controls, naive patients, and patients on other antiretroviral regimens. Multivariate analyses showed that patients receiving both Stavudine and full dose Ritonavir had significantly lower BMC values both at the lumbar spine (P = 0.0033), and in the whole skeleton (P = 0.05). In conclusion, antiretroviral treatment may have a detrimental effect on bone health of HIV-infected youths: the use of Ritonavir full dose alone or in combination with Stavudine is associated to lower bone mass measurements. The use of antiretroviral regimens including these drugs should thus be monitored closely in HIV-infected youths.

The main areas of progress in osteoporosis research during the last decade have been the general recognition that this condition, which is the cause of so much pain in the elderly, has its roots in childhood and the identification of the structural basis accounting for much of the variations in bone strength among humans. Available data indicate that there is very little difference in measures of cancellous bone density in the vertebral body between sexes. In contrast, females have a smaller vertebral cross-sectional area when compared with males, even after accounting for differences in body size; a gender difference that becomes most apparent after puberty. Hence, vertebral fractures are likely more common in women than in men because women have smaller vertebrae. Although at present, the reasons for the reported gender differences in the incidence of hip fractures have yet to be clearly defined, it is tempting to think that complete phenotypic characteristics responsible for variations in femoral strength will be soon delineated. Such knowledge will provide a more rational way to identify those subjects prone to develop fractures and towards whom osteoporosis prevention trials should be geared.