The Diagnostic Value of the Vacuum Phenomenon during Hip Arthroscopy
Figure 2
(a) Fluoroscopy of the right hip of a 15-year-old boy with Perthes disease prior to traction. (b) One minute of traction: the vacuum phenomenon shows a “double bubble” effect—a dynamic detachment of cartilage from the femoral head that was not evident on MRI. Vacuum fails to develop in the medial half of the joint. (c) Eight minutes of traction: the hip was further distracted and the vacuum phenomenon disappeared. (d) Arthroscopic view of the right hip shows chondrolysis of the femoral head. Massive synovial proliferation obliterates the medial aspect of the joint.
