Anatomy, Pathology, and Treatments:
The hip is composed of two bones, the head of the femur (ball on top of thigh bone) and the acetabulum (socket) that is a portion of the pelvis. The ends of these bones that move about each other have a layer of cartilage, which forms the surface of the joint. There have been multiple studies looking at different risk factors for osteoarthritis in the hip and one of the factors is impingement. This may occur as a result of extra bone placed on either the femoral head (ball) or the acetabular rim (socket).
“Cam Impingement”
The term “Cam Impingement” is used to describe extra bone formation in front of and at the superior aspect of the femoral head and neck junction. In this scenario, as the hip is flexed the area of extra bone growth called the “cam deformity” will engage the anterior aspect of the socket. When this happens repetitively, like when one performs squatting or sits for a long period of time, this can cause damage to the cartilage of the socket and the overlying labrum. The labrum is a fibro-cartilaginous lip of tissue that lines the rim of the acetabular socket. The labrum is an important structure involved in joint fluid regulation into and out of the hip socket. When there is a labral tear, or tear in the labrum, there may be an abnormal regulation in this joint fluid that may lead to micro-instability in the hip and thus further increase the risk of cartilage damage. The term “Pincer Impingement” is used to describe the scenario where there is too much bone on the acetabular socket. This may also cause repeated damage to the acetabular labrum and cartilage and also the femoral head cartilage.
Symptom Improvement
Patients may experience improvement in symptoms with a hip steroid injection and potentially physical therapy. There are also minimally invasive arthroscopic hip surgeries, which attempt to remove excess bone that causes impingement and cartilage damage. In this procedure it is also possible to perform a labral repair or debridement. Severe cases may be indicated for a minimally invasive anterior approach total hip replacement surgery or total hip arthroplasty.