No one is too surprised when an older adult is hampered by hip pain. Usually it’s arthritis-related and we know just what to do. But when it happens to someone in their 30s or 40s, it creates more of a stir. Preventing hip osteoarthritis as early as possible is important, so hip pain early on must be attended to.
In this report, surgeons from the American Academy of Orthopaedic Surgeons (AAOS) present an instructional course lecture to other surgeons on the recognition and treatment of a painful hip impingement in younger adults. Understanding the types and causes of hip impingement is important in planning the optimal treatment approach.
The full medical term for this problem is femoroacetabular impingement. Impingement just means pinching. Femoroacetabular refers to the place in the hip where the round head of the femur (thigh bone) comes in contact with the acetabulum or hip socket. Two types of impingement are known to cause pinching of the soft tissues in this area.
The first is called cam-type impingement. This occurs when the round head of the femur isn’t as round as it should be. It’s more of a pistol grip shape. It’s even referred to as a pistol grip deformity. The femoral head isn’t round enough on one side and it’s too round on the other side to move properly inside the socket.
The result is a shearing force on the labrum and articular cartilage, which is located next to the labrum. The labrum is a dense ring of fibrocartilage firmly attached around the acetabulum (socket). It provides depth and stability to the socket. The articular cartilage is the protective covering over the hip joint surface.
Sometimes cam-type impingement occurs as a result of some other hip problem (e.g., Legg-Calvé-Perthes disease, slipped capital femoral epiphysis or SCFE). But most of the time, it occurs by itself and is the main problem.
The second type of impingement is called pincer-type. In this type, the socket covers too much of the femoral head. As the hip moves, the labrum comes in contact with the femoral neck just below the femoral head. Repeated microtrauma at this site can cause the bone to overgrow, a condition called heterotopic bone growth.
Pincer-type impingement is usually caused by some other problem. It could be as a result of 1) hip dysplasia, 2) a complication after osteotomy surgery to correct hip dysplasia, or 3) an abnormal position of the acetabulum called retroversion. Hip dysplasia is a deformity of the hip (either of the femoral head or the acetabulum, or both) that can lead to hip dislocation.
Identifying hip impingement as the cause of painful groin symptoms starts with a patient history and physical exam. Most patients report the pain occurs when the hip is bent or flexed. Although the condition is often present on both sides, the symptoms are usually only felt on one side. In some cases, the groin pain doesn’t start until the person has been sitting and starts to stand up. There is often a slight limp because of pain and limited motion.
Through a series of questions and clinical exam, the surgeon is able to rule out referred pain (coming from someplace other than the hip but felt in the hip). One test that can be performed in the physician’s office for this problem is called the impingement sign.
The patient lies on the table on his or her back. The examiner bends the leg up, internally rotates the hip, and presses the knee toward the other leg. This position puts the hip in such a position that impingement occurs and reproduces the painful symptoms.
If this sign is positive, then X-rays may be needed. Regular X-rays don’t always show this condition. So, the authors advise surgeons on the specific X-ray views required (e.g., Dunn view, cross-table lateral view). The details of X-ray findings are presented in depth with photos to demonstrate what to look for.
Retroversion is confirmed by the presence of three signs seen on X-rays: the crossover sign, the posterior wall sign, and the ischial sign. Photographs of X-rays with each of these signs are presented in the article.
More advanced imaging such as MRIs, CT scans, and dye-enhanced arthrography may be needed before surgery. The details offered from these tests help the surgeon plan the best approach to the problem. MRIs in particular alert the surgeon to the presence of other problems such as labral tears, cysts, or damage to the articular cartilage. The presence of any of these additional problems can complicate surgery.
But before surgery is done, patients are advised to try nonoperative therapy first. They are given antiinflammatory medications and physical therapy. Whether or not this is the best approach remains to be seen. Studies have not been done to see if delaying surgery in this way has a good or bad (or any) effect on the problem.
Once it has been decided that surgery is the way to go, the surgeon has three choices: 1) full open incision and correction of the problem, 2) arthroscopic surgery, and 3) osteotomy. With the fully open surgical procedure, the head of the femur is dislocated from the socket to make the changes and corrections. With arthroscopic surgery, dislocation is not required. Osteotomy (reshaping the socket) is done for pincer-type impingement.
With photos and a detailed description, the authors walk the reader through each of these surgeries. They describe recommended techniques for surgical dislocation. When to use each procedure (based on type of impingement and imaging findings) is outlined. The results of these operations as reported in other studies are also reported.
Complications such as overcorrection or undercorrection, loss of correction, joint or wound infection, nerve or blood vessel injury, and unintended bone fracture are a few of the complications discussed. Results are compared between open incision and arthroscopy. The use of arthroscopic techniques for this problem is still new enough that long-term results aren’t available yet.
Whenever possible, the surgeon tries to save the hip. But when there is extensive damage to the cartilage, hip resurfacing or total joint replacement may be needed. There are many factors to consider when making this decision. The patient’s age, findings on imaging studies, type and severity of deformity, and presence of arthritic changes are important.
The best time for surgery isn’t known. Delays may result in even worse cartilage damage that can’t be repaired. But waiting can also give the patient a better chance for the development of better choices in the future, such as cartilage grafting or computer-assisted surgery. Less invasive approaches to hip surgery are being developed all the time. Young patients with minimal signs of osteoarthritis may want to take the chance and wait to see what comes in the future.