Musculoskeletal Manifestations of Sickle Cell Disease
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Chwechweechw, ahotutuo, nwiiwii, and nuidudui are names the native
Africans have for centuries called sickle cell disease. The disease has
persisted in realatively high incidence among this population because
of its "protective" effect against malarial parasite infection.
Although individuals with the sickle cell gene are not immune to
infection, they are afforded an advantage at resisting serious illness.
Invasion by the merozoites of the red cells of individuals with sickle
cell disease or trait causes sickling of the cells which triggers their
destruction in the spleen before the parasite can gain access to the
In 1910, Dr. James Harrick described a patient from
the West Indies with anemia, whose red cells were "sickle shaped," and
thus introducing the western hemisphere this unique hemoglobinopathy.
A point mutation of the B-globin gene produces a missense mutation yielding a substation of valine for glutamine at the 6th
codon and the production of Hemoglobin S. Hemoglobin S in the
deoxygenated state undergoes aggregation and polymerization with in the
red cell, leading to the sickle formation of the cell membrane along
with problems of cell volume regulation and endothelial adhesion.
Sickle cell disease is autosomal recessive. In the individual with
homozygous HbS, sickling causes severe organ damage and reduces life
expectancy here in the United States to less than 50 years. Eight to
ten percent of African-Americans carry the trait, and 0.2% of this
population is affected by the disease.
The primary pathological results of this hemoglobinopathy are
hyperbilirubinemia, anemia, and vaso-cclusive disorders. The latter
two, along with their sequelae, are of most importance when considering
musculoskeletal radiographic features of the disease.
Acute anemia and Vaso-Occlusive Disorders
- Bone infarction
- Secondary osteomyelitis
Any anemic state has the potential to cause persistent red marrow in
abnormal locations. Sickle cell patients retain the majority of their
marrow as red cell forming, and in severe cases even the commonly fatty
marrow epiphysis may be involved.
The systemic oxygen requirement may also cause expansion of existing
red marrow, leading to enlargement of marrow spaces. As with persistant
red marrow, this is a finding common to any severe chronic anemic
state. The classic manifestation is the "hair on end" appearance and
widening of the outer table of the skull by expansion of marrow in the
diploic space seen on radiography and MR.
The following four MR images demonstrate extensive marrow
hemosiderosis, AVN of the right hip and both knees, and bone infarcts
Flow patterns in the marrow predispose it to infarction. The slowing
of blood flow through the marrow space allows for regional hypoxia and
thus sickling of red cells, leading to infarction. The proximal
epiphysis of long bones, especially the humerus and femer is the most
common location of infarction in sickle cell patients. Vertebral
osteonecrosis and the formation of "fish vertebrae" is a classic
The most significant consequence of infaction is osteonecrosis.
Osteonecrosis during childhood can lead to abnormal development, and
during adulthood it may cause osteoarthritis or joint distruction. Age,
the presence of leg ulcers, previous ostyeonecrosis of the humeral or
femoral head, and higher hemoglobin levels all raise the risk of
Osteonecrosis and collapse of multiple
thoracic vertebral end plates, giving the appearance of "fish
vertebrae" in this 28 year old woman with sickle cell disease
and recurrent bone pain.
Humeral head infarction and osteonecrosis in a 50 year old female with sickle cell disease.
Films of a 38 year old female with
bilateral hip pain showing bilateral femoral head infarcts and
osteonecrosis with subchondral collapse of the superior femoral
Individuals with sickle cell disease are predisposed to
osteomyelitis secondary to ischemic injury of both bone and GI tract.
This results in a high incidence of seeding of infarct beds with GI
flora, most commonly Salmonela; as opposed to the more common cause of
osteomyelitis in the general population, S. aureus.
Osteomyelitis is difficult to distinguish from bone infarction, and
occurs much less commonly. Findings on plain film are nonspecific and
include periostitis and osteopenia. MR is the preferred method for
evaluation and demonstrates high signal on T2 weighted images and STIR.
The most sensitive study is a T1 fat saturation study performed post
gadolinium. Abnormal enhancement in this series is indicative of
- A Brief History of Sickle Cell Disease. http://sickle.bwh.harvard.edu/scd_history.html
- Sickle Cell Disease. Grainger & Allison's Diagnostic Radiology. Churchill Livingstone, Inc. 2001, pp 1904-8.
- Robins: Pathological Basis for Disease. W.B. Saunders Co. 1999, pp 611-15.
- Prevalence, clinical features, and risk factors of
osteonecrosis of the femoral head among adults with sickle cell
disease. Mukisi-Mukaza et al. Orthopedics. 2000 Apr;23(4):357-63.
- Sickle Cell Anemia. Lonergan et al. Radiographics. 2001(21):971-94.