Lead in the human femoral head: Relationships of pathology, environmental exposure, micro-architecture, and biocultural contributions to bone quality
Prutsman-Pfeiffer, Jennifer Jill
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The purpose of this study is to investigate lead concentrations in the femoral heads of patients who had hip replacement surgery for the indications of fracture and osteoarthritis. The research is modeled after an anthropological biocultural approach, incorporating patient medical and social history with the biological and biochemical information as provided by the pathologic femoral head. Bone is a biomarker of cumulative environmental lead exposure, and this study establishes a database for lead concentrations and lead isotope ratios for a sample of individuals from western New York. Relationships between pathology, micro-architecture of the trabecular bone, and medical and social history of the patients are explored. Lead isotope ratios show that there are differences in the cortical bones for different age groups, and that individuals can be discriminated from each other based on unique isotopic signatures of lead in the bone. Lead is ubiquitous in the environment, and we are all exposed to varying degrees. Lead becomes sequestered in the skeleton and reflects the long-term environmental exposure from a variety of sources ranging from past leaded gasoline emissions to household dust containing lead from degraded painted surfaces. Lead continues to be a major health problem despite measures to curb exposure. High levels of lead have been clinically associated with hypertension, renal failure, and neurological deficits in humans, and may be an environmental risk factor for osteoporosis. Endogenous skeletal release of lead into the circulation may accelerate the deterioration of already compromised bone and interfere with normal bone healing. Much is known about the hazards of lead, yet studies are lacking as to the effect lead has on the skeleton. This investigation correlates the amount of lead in bone with patient demographics, medical history and diagnoses, bone pathology, and sociocultural habits of tobacco smoking and alcohol use. It is important to establish a baseline of cumulative lead exposure for a typical sample of osteoarthritis and fracture patients to provide the scientific community with precise measurements of lead in a modern population from direct sampling of bone. This study accomplished that objective through the use of Inductively Coupled Plasma Mass Spectrometry (ICP-MS), the gold standard for measuring inorganic trace elements. Portable X-Ray Fluorescence (pXRF) was a second analytical method used to determine the utility of this tool for field use in analyzing elemental concentrations in bone. Analysis of the results obtained by the pXRF was limited to lead. Results obtained were in agreement with ICP-MS. However, caution should be used when interpreting results at the lower limits of detection for the equipment, as is the case in this study. The results show that there are differences in the lead concentrations between fracture and osteoarthritis specimens, with fracture specimens having higher lead concentrations. Fractures occur more frequently in an older age group, and lead accumulates with age. The results may be reflective of this logic. The study results reveal that there is no relationship between lead concentrations of the cortical or trabecular bone and micro-architectural properties measured by Micro-CT imaging analysis. There is no association of bone lead and smoking or alcohol use. Lead concentration does not associate with any of the measured medical conditions. Lead isotope ratios show differences between cortical and trabecular bone types, and between individuals. This research contributes to the scientific knowledge of lead concentrations in pathologic specimens from a modern group of individuals. The study may be weakened by small sample size, lack of age-matched controls, and lack of detailed individual patient information regarding personal histories of occupation, residence, and personal habits.