Protrusio acetabuli and bilateral basicervical femoral neck fractures in a patient with Marfan syndrome.

A 22-year-old man with Marfan syndrome and bilateral protrusio acetabuli presented with bilateral femoral neck stress fractures after vigorous stretching exercises for hip "stiffness." Fifteen years later, his fractures, which were treated with internal fixation, have healed, his acetabular protrusion has not worsened, and his perceived hip "stiffness" persists. This case demonstrates a rare manifestation of Marfan syndrome, protrusio acetabuli, and a possible side effect of vigorous stretching in the face of abnormal joint mechanics.