Osteonecrosis of the Femoral Head in Sickle Cell Disease



Osteonecrosis of the Femoral Head in Sickle Cell Disease





FUNDAMENTALS AND BACKGROUND

Sickle cell disease (SCD) is an inherited disorder of the red blood cells that leads to chronic hemolytic anemia and microvascular occlusion. One of the most common musculoskeletal complications associated with SCD is osteonecrosis of the femoral head. The incidence of osteonecrosis of the femoral head in patients with SCD is 2 to 4.5 cases per 100 patient-years with an overall prevalence of 10%.1 Typically, children with SCD who developed osteonecrosis of the femoral head present with new onset of hip pain and a limp. A high suspicion for osteonecrosis of the femoral head in patients with SCD encourages early advanced imaging. Often, in the initial phase of necrosis, plain films, including an anteroposterior (AP) and frog-lateral radiographs, may not suffice for the diagnosis, and a magnetic resonance imaging (MRI) should be obtained. Femoral head involvement can be assessed by measuring the arc of the necrotic segment (the necrotic arc angle).2 The size of the lesion is defined by the sum of the necrotic arc angles measured on the AP and frog-lateral radiographs. Collapse of the femoral head is measured as the distance from a perfect concentric circle around the femoral head to the area of collapse.3 Multiple classifications exist for quantifying the extent of osteonecrosis of the femoral head. We use the University of Pennsylvania system (Steinberg staging).4 According to the staging system, stage 0 is preclinical with normal radiographs and MRI; stage I has normal radiographs with abnormal MRI; stage II reveals diffuse or localized areas of cystic and sclerotic changes in the femoral head; in stage III, there is subchondral collapse without flattening of the femoral head (crescent sign); stage IV is identified by flattening of the femoral head but no acetabular involvement; stage V is characterized by the development of acetabular changes in addition to the collapse of the femoral head with joint space narrowing; stage VI is defined by advanced degenerative changes of the hip joint.4 Grades I to IV are subdivided into A (<15% femoral head is affected), B (15% to 30% of the femoral head is affected) and C (>30% of the femoral head is affected).

Osteonecrosis of the femoral head can have a deleterious impact on patient’s function and quality of life. Osteonecrosis can not only have a major impact on patient’s function and quality of life, but can also affect the long-term survival of the native hip. Osteonecrosis may ultimately lead to deformity of the femoral head and osteoarthritis of the hip. The natural history of patients with SCD and osteonecrosis during childhood or adolescence is unsatisfactory, with 80% of hips developing pain, restricted motion, limb-length inequality, and limp.5 Most asymptomatic patients develop symptoms later in life and may have radiographic progression to femoral head collapse.6 A recent prospective study of children with SCD followed by MRI for an average of 2 years reported that 65% of the patients developed progression of their necrotic lesions.7

Treatment of osteonecrosis of the femoral head in patients with SCD includes nonsurgical strategies and surgical treatment. There is no medical treatment to prevent femoral head collapse. Physical therapy is typically recommended along with provisional limitation of weight-bearing. A randomized prospective study compared 21 adult patients with SCD treated with physical therapy alone versus 17 patients treated with core decompression and physical therapy. After a mean follow-up of 3 years, there was no difference in patient-reported outcomes and hip survival between the two groups.8 Isolated core decompression was performed in the past for SCD osteonecrosis. However, contemporary techniques, including injection with osteoinductive cells, have improved the outcome of core decompression alone. Gangji et al9,10 reported better symptom resolution and lower risk of femoral head collapse in patients undergoing core decompression with implantation of autologous bone marrow cells compared to core decompression alone. Hernigou et al11 investigated 38 skeletally mature patients with SCD followed from 10 to 17 years and showed that core decompression with autologous bone marrow implantation brought about
pain improvement and delayed progression to collapse of the femoral head in 87% of the hips. Although adults with osteonecrosis may benefit from a total hip arthroplasty (THA), patients with SCD have a higher proportion of complications and implant failure. Therefore, THA is not commonly performed in pediatric patients with SCD and osteonecrosis of the femoral head.12,13,14,15

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May 10, 2021 | Posted by in ORTHOPEDIC | Comments Off on Osteonecrosis of the Femoral Head in Sickle Cell Disease
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