The American Journal of Orthopedics
Author: Mark r. Brinker, MD, Kevin A. Thomas, PhD, Steven J. Meyers, MD, Terry Texada, MD, James R. Humbert, MD, Stephen D. Cook, PhD, and Richard Gitter, MD
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Sickle cell anemia is a chronic hereditary disorder commonly found in the black population. It is characterized by chronic hemolytic anemia and tissue infarction, secondary to microvascular occlusion by sickled erythrocytes. Many organ systems are affected by the vaso-occlusive process of sickle cell anemia. including the musculoskeletal system. Repeated ischemic episodes affecting the musculoskeletal system are responsible for much of the morbidity associated with this disease.
The effects of sickle cell anemia in bones are the result of two processes: bone marrow hyperplasia and vaso-occlusion. Bone marrow hyperplasia is a response to the chronic anemia associated with this disease. The normal half-life of red blood cells is approximately 60 days. but with sickled erythrocytes. it is 5 to 20 days. Bone marrow hyperplasia is most evident in the first 6 months after birth. a time when fetal hemoglobin is being replaced by sickle cell hemoglobin.
The earliest changes in sickle cell anemia are found in the metacarpals. with the classic change being squaring of the first metacarpal head. The spectrum of changes are expansion of the medullary 'pace, connective-tissue replacement. coarsening of the trabeculation v.ith cortical intrusian. cortical thinning, and a periosteal reaction, As the disease process continues, there is decreased osteoblastic activity and decreased bony formation. leading to an osteoporotic state. These changes have been shown in the lumbar vertebrae by many investigators. It was found that lumbar vertebral bodies had a decrease in vertical height. an increase in width. and a biconcave or fish vertebra appearance.
The vaso-occlusive effects of sickle cell anemia are more responsible for the morbidity), and disability of the disease, unlike the hyperplastic changes that are more responsible for diagnostic purpose •. Vaso-occlusive changes begin early in the disease process when fetal hemoglobin is being replaced by sickle cell hemoglobin. Dactylitis or "hand-foot syndrome" is the first clinical manifestation experienced; it usually manifests during the first 6 years of age and is characterized bv infarction of the medullary cavity and diaphyseal cortex of the metacarpals, metatarsals, and phalanges. Medullary infarction is due to vaso-occlusion of the nutrient...