Sickle Cell Hemoglobinopathies

In sickle cell hemoglobinopathies there are three main orthopedic issues as a result of the disease process that the surgeon must consider: marrow hyperplasia, osteonecrosis, and pyogenic infections. The underlying cause of marrow hyperplasia in the patient with sickle cell disease is a result of repetitive end organ necrosis and infarcts. When the spleen is significantly infarcted, the marrow increases hematopoiesis, leading to marrow hypertrophy, in turn resulting in thinning of the cortex of long bones. As the process continues, the blood supply is compromised in small areas, resulting in ischemia and bone infarctions. These areas of bone infarcts become patchy areas of sclerotic bone and eventually lead to canal stenosis or even obliteration. In addition, because of these changes to the bone marrow, compromising its blood supply, as well as the presence of an autoinfarcted spleen, these patients are also at increased risk for pyogenic infections with Streptococcus pneumoniae , Salmonella , and Klebsiella (which can spread hematogenously and seed bone). Despite this, Staphylococcus aureus is still the most commonly reported pathogen in patients with sickle cell disease who undergo total hip arthroplasty and acquire an infection.

Several studies have reported comparable results of total hip arthroplasty in patients with sickle cell disease using cemented and uncemented components. The more recent studies support the use of uncemented components with favorable outcomes. There are limited numbers of patients in these studies and, because there are no prospective randomized trials, definitive knowledge regarding which method is superior is unclear. We use uncemented components and thus will focus our discussion on the use of this technique.

Paget Disease

Paget disease is a metabolic bone disorder that primarily affects individuals of Anglo-Saxon ancestry. Although there is evidence to suggest its etiology is a slow viral illness affecting patients with a genetic predisposition, definitive proof of this has not been established. In Paget disease there is a marked increase in bone resorption and formation in one or more isolated anatomic areas (e.g., monostotic or polyostotic Paget disease). The most common locations occur around the hip and include the proximal femur as well as the acetabulum and pelvis. There are two main phases of the disease: lytic and blastic. During the active lytic phase there is an increase in the vascularity to the bone ( Fig. 25-1 ), which is associated with increased bone pain. This is very important to the overall physiology of the patient because this demand for oxygen and shunting of blood to the bone may overload the circulatory system, resulting in high-output cardiac failure. Implant fixation can also be affected by this hypervascularity, such as in preventing good fixation with cemented components. By using serum alkaline phosphatase and urinary markers of bone collagen, turnover activity of the disease may be quantitated. This can help the surgeon or medical consultant to control disease activity before operative intervention.

Right hip with Paget disease shown on an anteroposterior radiograph and with a gross specimen demonstrating the highly vascular bone.

Pagetoid bone is also susceptible to bone deformities, such as coxa vara and femoral bowing, which should be clearly defined with proper preoperative radiographs, particularly if a long-stemmed prosthesis is to be used or if an osteotomy is planned ( Fig. 25-2 ).

Lateral radiograph of the right hip in a patient with Paget disease demonstrating bowing of the femur.

Osteoporosis

Very few studies have carefully evaluated the impact of osteoporosis on outcomes of total hip arthroplasty. However, whereas studies specific to osteoporosis are limited, several investigations have evaluated the outcomes of total hip arthroplasty in the elderly. In these reports, patients were not stratified by bone density but rather by proximal femoral morphology. Although it has been suggested that severe osteoporosis should influence prosthesis selection and whether to use cemented or uncemented components, no definitive investigations have addressed these concerns.

More recent studies suggest that uncemented stems are as efficacious as cemented stems and this is our implant of choice.

Dorr and colleagues described the effects of osteoporosis on the proximal femur as a means of understanding the potential impact of aging and metabolic bone disease in preparation for total hip arthroplasty. They correlated radiographic findings with histologic changes as they classified the morphology of the proximal femur. The classification system consisted of three morphologic types with type A representing one found in younger male patients with thick cortices, type C representing the femur of an older patients with thinner cortices and a wider intramedullary canal often found in elderly women, and type B as a transitional stage between the two. These findings indicated that as canal widening occurs the endosteal cortex becomes more porous and progresses to the periphery. The concern with using cementless stems in this population is that the resorption will prevent adequate bony ingrowth and result in aseptic loosening and pain.

As individuals age and bone loss occurs there is a loss of the trabecular scaffolding that adds support to the cylindrically shaped cortex. As endosteal bone loss increases, periosteal bone apposition occurs as a compensatory mechanism to protect the diaphysis mechanically. As a consequence, the geometry of the femoral diaphysis is altered such that the femur widens and resembles a stove pipe with thin cortices: the type C femur of the Dorr classification. However, despite the protection afforded the femur when loaded in torsion or bending, the so-called hoop stresses induced by broaching and implantation of the prosthesis are not influenced by cortical expansion. Instead, the osteoporotic and aged femur is susceptible to fracture during the operation and thus care must be exercised at key times, such as when the hip is dislocated in preparation for femoral and acetabular preparation and when the femur is machined to accommodate the stem component.

Renal Disease

Because the kidney plays a major role in maintaining mineral hemostasis of bone, renal disease significantly alters the metabolic activity of bone. Arthroplasty surgeons need to be familiar with the osseous changes secondary to renal failure because these metabolic changes affect the quality of bone. Two types of osteodystrophy have be described similar to the phases of Paget disease, a high-turnover and a low-turnover osteodystrophy. Classic renal osteodystrophy is a high-turnover state in response to secondary hyperparathyroidism with high levels of parathyroid hormone being produced. These high levels of parathyroid hormone cause an increase in osteoblast and osteoclast activity. Low turnover renal osteodystrophy occurs because of the advances in treating renal disease. It occurs in patients whose disease is being treated adequately and who have normal levels of parathyroid hormone and adynamic bone. The defect here is believed to be due to the inability to excrete aluminum. Aluminum impairs osteoblastic proliferation and maturation, resulting in these adynamic or aplastic bone lesions.

Regardless of the cause, as a result of renal disease the arthroplasty surgeon will encounter skeletal deformity due to osteomalacia and heterotopic calcifications. These patients often present with pain and weakness and may have extraskeletal manifestations such as periarticular calcifications. There is a high incidence of total hip arthroplasty in patients on dialysis or with kidney transplants. Osteonecrosis is the leading diagnosis for a total hip arthroplasty in this patient population. As a result of the soft osteomalacic bone, cemented femoral stems have been recommended. Loosening has been a problem identified with total hip arthroplasty, and high revision rates (46%-58%) have been reported, with a mean follow-up of 8 years. Understanding renal disease and its musculoskeletal significance is very important for arthroplasty surgeons, and recognizing that a total hip arthroplasty in this patient group in not a routine total hip replacement is critical.

Sickle Cell Hemoglobinopathies

Osteonecrosis is the most common problem associated with sickle cell disease leading to total hip arthroplasty. Usually, sickle cell patients who have symptomatic osteonecrosis progress rapidly to show collapse of the femoral head. Hernigou and colleagues reported an 87% rate of collapse within 5 years from initial diagnosis for stage I or II osteonecrosis. In this natural history study of 90 symptomatic hips, 88 required surgical intervention. The time until surgery from the onset of symptoms was 40 months for stage 1, 10 months for stage II, and immediately for stage III and IV osteonecrosis. Interventions such as core decompression have been reported with variable success, but because the disease is progressive the inevitable solution for pain relief will ultimately be total hip arthroplasty. Other relative indications for arthroplasty are intractable hip pain, significant acetabular involvement, restricted range of motion, and antalgic gait.

Contraindications to total hip arthroplasty in sickle cell patients include a history of pulmonary hypertension as a result of the increased risk of postoperative acute chest syndrome, where patients develop respiratory distress as a result of a vaso-occlusive crisis or indirectly as an infectious process in the lungs. Acute chest syndrome is defined as a new infiltrate on chest radiography with associated fever, shortness of breath, and chest pain. The etiology is unclear and can include fat emboli, pulmonary infarct, infections, or unknown causes, as is usually the case. Patients who are experiencing a vaso-occlusive crisis should not undergo total hip arthroplasty. These crises can be triggered by a low hematocrit or dehydration, both of which will be exacerbated by the physiologic stresses of a major operation.

Paget Disease

Almost half the patients with Paget disease develop degenerative hip arthritis. Patients can also develop deformity secondary to the disease process such as coxa vara and diaphyseal bowing. These can alter the biomechanics of the hip.

Operative treatment should be avoided during the active, lytic phase of the disease, because this phase is associated with increased vascular proliferation, which can lead to increased blood loss at the time of operation. A theoretical concern exists for impaired bone ingrowth with the hypervascular bone, but only small series exist to refute this assumption. This phase of the disease is associated with high levels of alkaline phosphatase and urinary markers of bone turnover such as pyridinoline crosslinks and N -telopeptides.

Osteoporosis

Recognition of the impact of osteoporotic bone on potential difficulties encountered at the time of operation is important in the preoperative evaluation and intraoperative period. Although osteoporosis is neither an indication for nor contraindication to the treatment of degenerative arthritis of the hip with arthroplasty, surgeons must be careful to avoid creation of a fracture at key times during the procedure such as hip dislocation, seating of a press-fit acetabular component, broaching of the femur, and insertion of the femoral implant. In addition, reaming and medialization of the hip socket must be performed with care because the inner wall of the acetabulum is frequently thin and perforation can easily occur.