[Significance of intraosseous pressure for pathogenesis of Kienböck disease].

Femoral head necrosis is thought to be the consequence of decreased venous drainage. To confirm this pathogenetic model in lunatomalacia, the intraosseous pressure in 16 necrotic, 16 normal lunates and 16 normal capitates was measured. Intraosseous pressure was recorded in different functional positions: neutral position, extension, flexion, venous stasis, and exsanguinated conditions. Both in extension and in flexion, the intraosseous pressures of all bones exceeded those in neutral position; this corresponded to the increase in pressure during venous stasis. The increase in pressure in normal lunates and capitates could not be explained by mechanical deformation. Lunates showed a much higher increase in pressure than did capitates. Some necrotic lunates showed an intraosseous pressure during extension which exceeded the systolic blood pressure. This implies that mechanical deformation contributed to increased intraosseous pressure in necrotic lunates. The variation of intraosseous pressure suggests a physiological but unstable balance. An increase in pressure reduces the bloodflow and in addition to other promoting influences can lead to pathological conditions. The daily load of the wrist in extension is in accordance with the model of the origin of osteonecrosis on the venous side. The model that lunate necrosis is the consequence of impaired venous outflow can be accepted.