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Intracapsular pressure in transient synovitis of the hip
Insights
Transient synovitis in children causes hip effusion and increased intracapsular pressure. Flexing the hip to 45 degrees significantly reduces this pressure, preventing potential damage to the proximal femoral epiphysis (PFE) blood flow.
Area of Science:
- Pediatric Orthopedics
- Pediatric Rheumatology
- Diagnostic Imaging
Background:
- Transient synovitis is a common cause of hip pain in children.
- Intracapsular effusion is a hallmark of transient synovitis.
- The effect of hip position on intracapsular pressure is not well understood.
Purpose of the Study:
- To investigate the relationship between hip position and intracapsular pressure in children with transient synovitis.
- To assess the impact of intracapsular pressure on blood flow to the proximal femoral epiphysis (PFE).
- To determine optimal hip positioning for managing transient synovitis.
Main Methods:
- Sonography to evaluate intracapsular effusion.
- Scintimetry to assess blood flow in the PFE.
- Intracapsular pressure recording and aspiration.
- Hip pressure measurements in extension and 45 degrees of flexion.
Main Results:
- All 14 children presented with intracapsular effusion.
- Intracapsular pressure varied significantly with hip position.
- Mean pressure in extension was 22.6 kPa, while in 45 degrees flexion it was 2.3 kPa.
- Reduced PFE blood flow was observed in two cases, normalizing after aspiration.
Conclusions:
- Increased intracapsular pressure negatively affects PFE circulation.
- Hip flexion to 45 degrees is recommended to reduce intracapsular pressure in transient synovitis.
- Extension positioning poses a risk of PFE ischemia.
Abstract:
Fourteen consecutive children with symptoms of transient synovitis of the hip were examined with sonography regarding intracapsular effusion, with scintimetry regarding blood-flow in the proximal femoral epiphysis (PFE) and with intracapsular pressure recording and aspiration. All patients had an intracapsular effusion. Intracapsular pressure was found to depend on the position of the hip. The mean pressure with hips in extension and inward rotation was 22.6 kPa (170 mm Hg) whereas in 45 degrees of flexion it was 2.3 kPa. In two cases scintimetry demonstrated reduced blood flow to the PFE; after aspiration, isotope uptake returned to normal, indicating that increased intracapsular pressure has a harmful effect on circulation to the PFE. Children with transient synovitis should be treated with the hips in 45 degrees of flexion to reduce intracapsular pressure. Forcing the hip in extension causes a risk of ischaemia of the PFE.