Anatomy of the Hip Joint
To better understand the following discussion of hip arthroscopy and the various other forms of surgical treatment for hip conditions, it's necessary to discuss the anatomy of the area.
The hip joint is the ball-and-socket joint made up of the femur (ball) and the acetabulum. Articular cartilage covers the ball (head of the femur) as well as the socket (acetabulum of the pelvis). While the cartilage covers the entire head of the femur, the acetabulum cartilage is in the shape of a horseshoe with a depression (fossa) in the center of the socket. This fossa contains soft tissue and a ligament connecting the femoral head to the socket.
The socket has a rim of rubbery fibrocartilage called the labrum. The labrum acts as a gasket, sealing in fluid and helping to deepen the socket. This labrum is analogous to the knee meniscus and shoulder labrum. The entire joint is covered with a tough capsule to contain the joint fluid and maintain cartilage lubrication and nutrition.
In addition, numerous tendons surround the hip, as well as bursae, which are lubrication "cushions" where soft tissues glide over bony prominences.
Illustration of hip joint
Labrum and cartilage
For the hip to last a lifetime, the anatomy must be normal along with the absence of catastrophic problems such as trauma or infection. Hip "dysplasia" refers to a hip that does not develop properly because of congenital dislocation or if the femoral head is not fully seated in the acetabulum. Degenerative changes can occur very early in life; the greater the abnormalities, the sooner symptoms may occur.
Dysplasia can cause arthritis (loss of cartilage) because the shallow socket creates inadequate contact between the ball and socket. The overloaded cartilage can wear away if this situation is not corrected. In addition, the labrum (rim) is often torn, because of the high loads to which it is subjected in trying to maintain coverage of the head.
Dysplastic hip with poor head coverage
Total hip replacement is extremely effective at relieving pain and restoring function as well as range of motion. But, it is an artificial joint and should be performed only if other "joint saving" procedures are not appropriate. Fusion makes the hip permanently stiff by obliterated the joint via bone bridging across the joint. This procedure was performed much more frequently in the past and is still appropriate in certain conditions, such as severe arthritis of one hip in a young person.
Osteotomy (cutting the bone) is a technique were the anatomy of the femur or socket is altered to relieve pain and prolong survival of the joint by reducing the abnormal loads on the cartilage. Arthrotomy (opening the joint) is a procedure where the joint is opened to clean out bone spurs, loose bodies, tumors, or to repair fractures.
Hip arthroscopy has been slower to evolve than arthroscopy of other joints such as the knee or shoulder. The difficulty is that the hip joint is much deeper in the body and therefore harder to access.
To perform the arthroscopy adequately, it is necessary to use traction to distract the joint under anesthesia. This distraction temporarily opens the space between the ball and socket by approximately one-half inch. This space is necessary to insert the scope and small instruments without damaging the labrum and cartilage. While this is possible under general anesthesia, we prefer epidural anesthesia, which provides muscle relaxation and complete pain relief but does not require a tube to be inserted in the airway, resulting in a much safer outcome. Fluoroscopy (x-ray) is used during the case to ensure that the instruments and scopes are inserted properly.
The instruments are inserted through two tiny skin incisions. Occasionally, a third or fourth incision may be required depending upon the procedure. Excellent visualization of the entire joint is possible.
Through the second opening (portal) instruments are inserted to shave tissue, cauterize structures, or remove pieces. On occasion, holes may be drilled into patches of bare bone where the cartilage has been lost. This technique, called "microfracture" or "picking" incites localized bleeding and encourages the formation of fibrocartilage (repair cartilage). Saline is pumped through the joint during the procedure to improve visualization and flush out debrided tissue.
Traction creates space for instument insertion
Cleaning away torn cartilage
Torn labrum at rim of socket
Removal of loose body from inside the hip
Once the case is finished, the hip may be injected with local anesthetic to decrease postoperative pain and facilitate discharge from the hospital. The procedure is usually done on an outpatient basis. Patients are usually discharged on crutches but can often return to full weight bearing after a few days. Physical therapy may be used during the postoperative period to increase range of motion and strength. It may be necessary to protect weight bearing for as long as six weeks following the procedure if the microfracture technique is used.
It should be noted that while the procedure has vastly improved the ability to treat certain hip disorders with minimal surgical trauma, it is not always an appropriate replacement for other larger operations. If the hip has severe degeneration, total hip replacement may be the only procedure that will provide long-term pain relief. Conversely, in younger patients with skeletal deformities ( i.e. dysplasia, impingement) hip arthroscopy will usually provide relief. But the relief may be short-lived because the underlying pathologic condition has not been corrected.
For more information on the HSS Surgical Arthritis Service or HSS physicians, contact our Physician Referral Service.
• Diagnostic imaging examinations provided by HSS Radiologists