Core decompression is a surgical procedure used to treat hip pain in the early stages of avascular necrosis. One of the causes of pain in AVN is increased pressure in the bone marrow of the diseased portion of the femoral head. Reducing the pressure in this area may relieve the pain of AVN and allow healing to take place.
Core decompression involves drilling of the femoral neck and femoral head. Drilling of the diseased area reduces pressure in the small vessels of the bone mar-row. This allows for greater blood flow and promotes healing of the bone. The procedure can be done under spinal or general anesthesia. The patient is placed in the supine or lying down position on a fracture table.
A special x-ray machine called an image intensifier pro-vides either intermittent or continuous x-ray in several planes. In this way, the exact area of necrosis can be identified and the position of the instruments can be followed during the course of the procedure.
After a skin incision is made, a guide wire is passed from the side of the hip in to the diseased portion of the femoral head. The location of the guide wire is checked with the image intensifier. When this is satisfactory, a channel is made over the wire with a larger drill.
This will drill out the zone of necrosis and relieve pressure in the area. The surgeon may choose to fill the defect with bone graft material. Some grafts are vascularized and have a blood supply from an adjacent area. An alternate procedure is to place a small nail within the femoral neck to support the bone while it is healing.
Core decompression can only be done in the early stages of avascular necrosis. At this point there is pain but little loss of motion. The changes may be seen only on an MRI study and not a plain x-ray. The joint surface of the femur should remain smooth and round. If the joint surface has collapsed it means the disease is more advanced. When this happens, core decompression is not likely to be successful in relieving pain.
Since the procedure requires removal of bone, many surgeons will recommend a period of partial or non-weight bearing with crutches for 6 to 12 weeks until the hip has fully healed. This may have to be modified if surgery is done on both sides.
Core decompression can relieve the pain of avascular necrosis in early stages. It may help to preserve the normal femoral head and be an alternative to hip replacement.