Sickle Cell Disease

Epidemiology

 

Black population

- heterozygote protective from malaria

- AD

 

Pathogenesis

 

Abnormal peptide substitution in ß chain of Hb

- HbS

 

Homozygous 1%

- HbSS

- sickling occurs with relative hypoxia

- trapped in blood vessels

- necrosis & pain

 

Heterozygous 8%

- sickle cell trait

- Hb SA

- sickling only with extreme hypoxia

 

NHx

 

High risk of pneumococcal septicaemic and meningitis

 

Clinical

 

1.  Vaso-Occlusion

 

Suffer recurrent crises of abdominal & bone pain

- bone crisis

- finger pain

- can get bone infarcts / medullary or juxtacortical

 

Treatment

- opioid analgesia

- hydration

 

2.  Anaemia

 

Sickled cells have shorter T½

 

3.  Osteomyelitis

 

Bone crises difficult to distinguish from OM

- infarcted bone becomes infected

- Salmonella associated with sickle OM

 

Chambers et al J Paediatr Orthop 2000

- retrospective review of cases of OM / septic arthritis

- salmonella most common cause of OM

- temp > 38.2, WCC > 15 000

- bone scan and xray not helpful

- blood cultures and tissue biopsy most useful in diagnosis

 

4.  Femoral head AVN

 

Incidence

- very common in homozygotes (30%)

 

Progression

 

Mont et al JBJS Am 2010

- systematic review

- asymptomatic medium to large lesions tend to progress (59%)

- small, medial lesions did not tend to progress (10%)

 

5.  Humeral head AVN

 

Incidence

- homozygotes (50%)

 

Operative Management

 

Issues

 

Tourniquet

- avoid in homozygous

- beware in heterozygous

 

Perioperative Management

 

High risk of crisis peri-operative

- transfuse preoperatively to reduce percentage of HbS

- keep well hydrated and oxygenated

- avoid hypothermia

- avoid post operative anaemia

 

Femoral Head AVN

 

Core Decompression

 

Neumayr et al JBJS Am 2006

- RCT of core decompression v physio in stages I, II and III

- no evidence of improved outcome with core decompression at 3 years

 

THR

 

Hernigou et al Clin Orthop Rel Research 2008

- retrospective review 312 THR with average follow up 13 years

- average patient age 32 years

- 3% revision for infection

- 13% revison for aseptic loosening

- 25% incidence of peri-operative medial complications