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Articles
Joint Preserving Strategies for the Hip
Wed May 29, 2013 by Dr. Tom Byrd
There is a growing understanding of conditions that lead to joint deterioration and arthritis. With this understanding, we are able to implement strategies that could prevent, or at least slow the eventual progression of these conditions. For an individual with painful arthritis, it is clearly understood that the single most important preventative factor is activity modification to protect and preserve the joint. For example, an avid runner may need to transition to low-impact activities such as swimming, cycling, or an elliptical trainer. A golfer who experiences pain when walking 18 holes may be better served by using a cart. We must each take responsibility for looking after our own joints because any surgery in the presence of arthritis is unlikely to restore it to normal.
Among patients undergoing arthroscopic surgery, labral tearing is the most common type of injury encountered, and this can often be diagnosed by MRI. However, many labral tears have associated articular damage which may not be detected before surgery. It is the articular damage that is the main long term problem. If the cartilage is broken down to the exposed bone underneath, a procedure called microfracture can be performed where small perforations are placed through the underlying bone, creating vascular channels to stimulate a cartilage healing response. Although the body will not grow new cartilage, it can form fibrocartilage which is a blend of scar tissue and cartilage. This fibrocartilage represents the body’s best effort at cartilage reformation and, while it may be imperfect, it is superior to leaving the raw bony surface to rub against the opposite side of the joint.
The microfracture technique is performed arthroscopically and adds little time to the surgical procedure. However, in order for this defect to heal, a period of protected weight bearing is required for 8-10 weeks following surgery. The initial healing cartilage tissue is like an immature scab. If the scab is not protected, it will repeatedly break open, and healing will be less successful. Microfracture is not effective for diffuse cartilage loss, but is better for focal defects with healthy surrounding cartilage. We have experienced an 86% success rate with 2 to 5-year follow-up in properly selected cases.
Femoroacetabular impingement (FAI), often referred to simply as “impingement,” is commonly found to be a cause of cartilage breakdown. There are two types: A lip of bone overhanging the front of the acetabulum can pinch the underlying labrum and articular cartilage; and a bony build-up on the front of the femoral head can squeeze against the cartilage as the hip is flexed. These can be assessed on xrays and with computed tomography (CT scan) which is a three-dimensional x-ray of the hip showing its bony contour. Impingement can be addressed with arthroscopic surgery by sculpturing down the front of the acetabulum and recontouring the shape of the bone around the femoral head.
Dysplasia, characterized by a shallow acetabulum, is another condition that can lead to articular breakdown of the acetabulum. Microfracture has been successful in treating this condition but a careful radiographic assessment is required to determine if a more extensive open operation to improve the depth of the socket would be of greater benefit. Deepening the socket is achieved by making cuts in the bone, repositioning the socket, and fixing it back with screws.
For inflammatory arthritis such as rheumatoid disease, chemotherapy drugs are often used in an effort to arrest the synovial proliferation. When these fail, arthroscopic synovectomy to remove the diseased synovium can aid in slowing the progressive destruction.
Femoroacetabular Impingement
The etiology of femoroacetabular impingement is variable. It is most clearly attributed to developmental abnormalities of the hip that occur during the childhood growing years. Perhaps more commonly, it is associated with osteophytes (bone spurs) that form during adulthood. Diagnosis of this condition can be made with xrays and is sometimes aided by computed tomography. The most easily diagnosed type is an abnormal shape of the femoral head and neck. There is a prominence of the bone on the front of the femoral head so that when the hip is flexed upward the bony prominence engages with the front of the acetabulum, resulting in breakdown of both the labrum and articular cartilage. The less distinct type is a lip of bone overhanging the front of the acetabulum that pinches the labrum and causes it to tear. Because of its location, it is harder to see on regular xrays. Many individuals may have this abnormally shaped bone without symptoms and do not require specific treatment. When symptoms do occur, it is usually as a consequence of cartilage breakdown. If arthroscopy is needed to address the cartilage damage, it is important to assess for, and address, impingement that may be the underlying cause.
Management of impingement has traditionally been described with open techniques. The transition to arthroscopic treatment carries the advantage of a less invasive procedure. This advantage is especially evident in more advanced cases. Once the articular loss has become severe, correcting the impingement becomes less critical since the irreversible damage has already been done. Sometimes it is simply hard to tell the severity of the articular loss prior to surgery. Arthroscopy has the advantage of being able to assess the severity in addition to addressing the impingement. If the joint is beyond help, at least the surgery has not been too extreme.
Dysplasia
Dysplasia is a word of Latin origin that means altered growth. In this case, the hip joint develops with an altered shape that is present from early childhood or even at birth. The most drastic example is a congenitally dislocated hip where the femoral head (ball) is dislocated outside of the acetabulum (socket) at birth. Left untreated, this results in a severely deformed hip. More commonly, the hip remains partially seated within the socket and only a mild amount of deformity ensues. This is best characterized by the acetabulum being abnormally shallow in the way that it surrounds the femoral head. Many people live with this condition their entire lives, never even aware that there is an abnormality. However, depending on the severity of the deformity, some people are more susceptible to developing arthritis and other hip joint problems that begin to manifest themselves during adulthood.
Dysplasia has three life-long effects. First, because the acetabulum is shallow, there is less articular surface area over which to distribute the normal body weight that is carried across the joint. This results in higher than normal compressive forces on the articular cartilage. Over time, if the cartilage is not be able to withstand this force, it may begin to beak down. Second, during growth, the body attempts to compensate for this shallow bony socket by enlarging the labrum cartilage that surrounds its rim. This enlarged labrum is under greater stress from the weight-bearing forces and can tear.
Also, because of its altered shape, it can flip inside the joint and become entrapped causing pain and more cartilage breakdown. Lastly, because of the shallow socket, the femoral head tends to partially slip out of the socket. This causes the ligamentum teres to elongate and enlarge and makes it susceptible to rupture and becoming another source of pain.
Injury to the labrum, articular surface, and ligamentum teres can all be addressed by arthroscopy. However, the severity of the dysplasia must be carefully assessed on xrays. Sometimes an open operation is necessary to cut the bone and redirect the socket, creating a larger surface area for the acetabulum. This may improve the hip mechanics and potentially result in more long-term preservation of the joint.
Labral Tears
Labral tears are a common culprit in painful hip conditions. Xrays are usually normal since they only show the bone and not the cartilage and other soft tissue structures around the hip. MRI (magnetic resonance imaging) is a more sophisticated non-radiation imaging technique for showing the various soft tissues. This may sometimes include a technique where dye is injected inside the joint to enhance the images. Even these sophisticated studies will miss problems in the joint about one-third of the time. In general, they are best at showing injury to the labrum, but still poor at showing other problems especially damage to the articular cartilage.
Labral tears may occur from an acute injury, such as twisting, but often occur as a consequence of repetitive activities and can happen simply as a result of degeneration or deterioration of the cartilage. In general, a healthy labrum is pretty resilient. Thus, any time a torn labrum is encountered, it should be suspected that there may have been some underlying predisposition to this injury. Only a few specific causes have been identified. Sometimes the shape of the hip joint may make this cartilage easier to tear. Among competitive athletes, it can occur as a consequence of breakdown as the body is pushed beyond its physiologic limits. Degeneration of the labrum is also recognized as an inevitable consequence of the aging process.
Arthroscopic treatment of a simple labral tear can be very successful. However, labral tears are often not so simple. Studies have shown that the majority of labral tears have some associated damage to the articular cartilage. While MRIs are better at showing labral tearing, they usually will not show the associated injury to the articular cartilage. This is best identified and addressed during arthroscopy. However, the arthroscopic treatment of articular damage is generally less successful than the treatment of a labral tear alone. Thus, when performing arthroscopy for labral tears, it is often the uncertain, but expected, extent of associated articular damage that may be the limiting factor in the success of the procedure.
Neglecting a labral tear with worsening symptoms can result in more secondary damage. Treatment is not urgent but, in general, it is preferable to recommend arthroscopy to address these injuries rather than letting them go indefinitely if the symptoms are getting worse. However, some reports indicate that MRIs have shown evidence of injury to the labrum among asymptomatic volunteers and some patients with injury have come to be painfree over time. Thus, a trial of conservative management may be appropriate as long as the symptoms are not worsening and the joint is given a chance to rest.
Arthritis
Approximately 70 million Americans suffer from arthritis and about 300,000 total hip replacement procedures are performed each year for this condition. Arthritis is characterized by breakdown of the articular cartilage, with resultant pain and stiffness. Arthritis of the hip is often a great imitator as far as how it behaves. Typically, we expect it to come on gradually and be associated with advancing age. However, the onset of symptoms may sometimes be surprisingly sudden and people may experience intermittent episodes of spontaneous remission. It can also strike young adults, even those without a family history of disease, and may be isolated to a single joint. The two most common types are osteoarthritis and rheumatoid arthritis.
Osteoarthritis is simply accelerated wear and tear of the joint. A previous injury may leave the joint damaged and susceptible to progressive breakdown. Variations in how the joint is shaped may lead to abnormal joint mechanics and accelerated wear. This is especially true with “femoroacetabular impingement” (FAI), a condition where abnormal bony build-up around the acetabulum or femoral head may result in accelerated cartilage breakdown; and “dysplasia”, a condition where the socket is abnormally shallow. Arthroscopic surgery is sometimes helpful at alleviating the symptoms associated with osteoarthritis. However, it cannot reverse the joint deterioration and is ineffective for advanced disease.
Rheumatoid arthritis is the most common of a large group of inflammatory arthritides. It is characterized by a poorly controlled proliferation of the synovium, resulting in erosion of the articular surface. This is generally considered to be one of the most devastating non-lethal diseases. Chemotherapy agents are often used to try to arrest the synovial proliferation but, even if the synovium is brought into control, the resultant articular damage may continue to cause problems. Arthroscopic excision of the diseased synovium can be effective for cases unresponsive to pharmacologic management. Arthroscopy cannot reverse the articular damage that has occurred, but debridement of the fragments and associated diseased tissue may be beneficial in reducing discomfort.