**2.1 Definition & history of SCD**

SCD is a chronic hemolytic hemoglobinopathy that is genetically transmitted. During a crisis, red blood cells become sickle-shaped increasing blood viscosity, slowing blood flow, and consequently plugging small blood vessels creating widespread thromboembolic tissue infarction.

This genetic disease which is the most frequent genetic disease in black people, is also the most common cause of femoral head necrosis in them. In fact, SCD touches up to 0·74% of the births in sub-Saharan Africa, while this number is 10-20 times less in Europe and North America. In Nigeria, an estimated 45,000 to 90,000 babies are born each year with SCD. The African blacks are the main victims but the disease is also distributed in the south of Italy, Greece, Turkey, the Arabian Gulf, especially Saudi Arabia, and the Indian subcontinent. In the United States SCD occurs in approximately 1 out of every 500 African American births. People in the USA with sickle-cell disease number 90,000 of which 80,000 are black and 10,000 are Hispanic. The state with the highest sickle-cell population was New York with 8000, followed by Florida with 7500, and Texas with 6700 people with SCD. FLOUZAT-LACHANIETTE et al. report a series of SCD patients developing secondary avascular

Arthroplasty in HIV/SCD Carriers 491

Preoperatively the HbS level should be of less than 30% of the circulating hemoglobin before major surgery such as Arthroplasty; however, VICHINSKY et al., have shown in a randomized controlled trial that, exchange transfusion may not be necessary to avoid complications. In all cases, it is prudent to take the preoperative hemoglobin concentration to 100 g/L and to keep it at this level in the early postoperative phase; this objective may be obtained by ordinary transfusion of normal red blood cells as it may be confirmed by post transfusion electrophoresis or chromatography. This will also reduce the risk of perioperative thromboembolic complications. The above target hemoglobin level may be rich by preoperative oral folic acid of few weeks, in those SCD patients with less than 30% of HbSS during the initial work-up; however, at least postoperatively, blood transfusion will be needed. It should be clear that, to the best of current literature, there is no place for autologous blood transfusion in SCD patients; these patients should always be managed with homologous bank blood products. In the other hand, Reduction of HbS concentrations may be obtained by the chronically use of hydroxycarbamide because this increases the concentration of fetal hemoglobin (HbF) which reduces hemolysis and prevents vasoocclusion. It is also well known that that hypothermia, acidosis, hypoxemia and dehydration

Acute chest syndrome is a specificity of SCD and affects around 20% of the patients. A combination of thoracic pain, fever and infiltrates on thoracic x-ray characterizes this syndrome. The etiology is multifactorial including pulmonary embolism, microvascular occlusion and infection Severity varies, but 13% of patients require mechanical ventilation and 3% may die. In a post operative period of any arthroplasty procedure in SCD patient, this syndrome should be seriously considered in establishing etiologies of acute chest pain. In fact, it prevention and management include respiratory support, antibiotics, blood transfusions and deep venous thromboses prophylaxis/therapy. At times corticosteroids

Susceptibility to infection is an issue in SCD. Many of these patients are immunocompromised because of autosplenectomy and osteonecrotic tissues tend to be colonized by Gram negative organisms. Several organisms have been identified as important causes of infection including S pneumoniae, H influenza, and non-typhi Salmonella species and appropriate antibiotic prophylaxis and immunization must be instituted in these patients. Therefore, a systematic preoperative investigation should be undertaken prior to any Arthroplasty procedure in a SCD patient to rule out occult infection; this should a least include urine culture, ENT consultation and dental examination and corrections. If there is a suspicion of infectious foyers a full antibiotic

**2.4 Work-up and management of SCD systemic acute complications** 

Stage II: Sclerotic and cystic changes

Stage IV: Osteoarthritis on both sides

should be avoided pre and postoperatively.

**2.4.2 Acute chest syndrome** 

may be indicated.

**2.4.3 Infection** 

Stage III : Collapse

**2.4.1 General** 

necrosis that originated from Africa, the United States of America, the Indian subcontinent, the Persian Gulf and from Mediterranean countries. Multifocal secondary vascular necrosis was found to occur in at least 64 percent of patients.
