Osteonecrosis of the hip is a well-described entity in which a portion of the hip wall loses its blood supply and thus the bone underneath the cartilage dies. This oftentimes can cause increases in pressure in the hip joint and if the lesion is large enough, the cartilage above the dead bone will collapse causing arthritis in the hip joint. Hip osteonecrosis is felt to be associated with approximately 10% of all hip replacements done in this country, the majority of which are done on young patients under the age of 50. There are several things that are associated with the occurrence of hip osteonecrosis. They include the use of steroids, excessive alcohol consumption, deep sea diving, subtle coagulopathies, and trauma.
The symptoms are similar to that of arthritis of the hip where the patient oftentimes has an achy-type pain which he or she will describe as being deep within the hip joint itself. On x-rays, you oftentimes will not see any joint destruction. Instead, you will see some changes within the substance of the bone on initial presentation. As the osteonecrosis (AVN) progresses, the area of necrosis may collapse and arthritis may ensue. Physical findings are also consistent with hip arthritis in that the patient will complain of pain with internal or external rotation of the hip joint. Their range of motion is not limited. They will have oftentimes full range of motion. They may or may not have a limp and the limp is associated with pain. There is no leg length inequality.
Treatment options include core decompression either with a single coring device or a multiple pin technique. We prefer using the multiple pin technique since it reduces the complication rate of fracture. It also allows the procedure to be done as an outpatient and allows the patient to begin weight bearing or walking immediately after the surgery. With Stage I disease, the success rate with core decompression is reported as high as 90%.
Other treatment options include osteotomies which is a breaking of the bone and redirecting the bone in a different orientation so that the area of bone necrosis is no longer under the weight bearing aspect of the hip. There is vascularized fibular grafts in which they take the leg bone and put it into the hip. This has been popularized by Dr. Urbaniak. He has reported reasonable results with this technique. There is though a 10% incidence of ankle pain associated with this procedure. There are techniques such as vascularized pedicle grafting done primarily overseas. This has met with marginal success. My partner and I have done techniques such as trapdoor where you will bone graft the area of dead bone in hopes to prevent collapse and thus save the femoral head and save the hip joint.
Another new technique based on an old idea is the placement of a tantalum rod, which is a new type of metal, into the femoral head in the hopes that this will provide structural support to the area of necrosis. There is limited data on this new technique. In Italy they report reasonable results using this technique. Something that is currently gaining tremendous popularity which we currently are doing under FDA approval, is a resurfacing hip replacement. This is done using a minimal incision and replacing only the area of dead bone with a resurfaced metal onto the femoral head and putting in an acetabular component. The advantage of this technique is that there is a lower dislocation rate and ideally an improved range of motion. It also potentially allows the patient to increase his activities and live a fuller life feeling more normal. If a revision operation is necessary, then the revision is potentially an easier one to perform. Other treatment options for hip osteonecrosis also include hip replacement. This historically has done very well, although not as well as hip replacement for purely osteoarthritis.
Labral Tear
The labrum of the hip is the cartilage lip that surrounds the socket. It allows the socket to be deeper and keeps the femoral head within the socket itself. Labral tears can occur from trauma, as well as the normal process of degeneration from hip arthritis. The classic labral tear occurs in the superior anterior portion of the labrum and is felt to be associated with some type of twisting or impact injury. Patients will oftentimes complain of a deep type pain that is associated with a locking type sensation and a clicking sensation as well. The pain is oftentimes activity related and is minimally improved with medication. The diagnosis of a labral tear can oftentimes be made via an MRI, but there is a false-negative rate so a hip arthroscopy is ultimately the definitive tool used to both treat and diagnose a labral tear. Hip arthroscopy is a relatively new idea on an old procedure. It is where you take a scope and you distract the hip and place the scope into the hip joint thus allowing you to visualize the entire hip joint. This technique should be done by someone who is experienced in both hip arthroscopy and hip anatomy. About 10% of hips require an open type procedure and thus should be performed by someone who is well-versed with the anatomy about the hip. We at the Rubin Institute for Advanced Orthopedics perform approximately 100 arthroscopies per year.