Cam Impingement
- FibonacciMD
- 1 day ago
- 2 min read
Understanding the Causes, Symptoms, Diagnosis, and Treatment of Femoroacetabular Impingement (FAI)
FibonacciBrief Orthopedics
Author: Allan Strongwater, MD
AKA
FAI
femoral acetabular impingement
femoral cam morphology
Cam impingement is a form of femoral acetabular impingement (FAI) that results from a misshapen femoral head. The femoral head is more ovoid than spherical. As the ovoid femoral head passes through a range of motion, the radius of curvature changes. The reduced radius allows the relatively widened femoral neck to contact the acetabular rim, resulting in pain and injury to the labrum and adjacent articular cartilage. FAI may also be associated with femoral head cysts that are degenerative in nature.
Causes and Risk Factors
FAI is usually the result of a misshapen femoral head due to childhood illnesses such as Legg Calve Perthes disease, slipped capital femoral epiphysis, or avascular necrosis. Certain genetic or familial diseases (e.g., multiple epiphyseal dysplasia, developmental coxa vara) can also produce femoral head malformation.
Signs and Symptoms
The pain from cam impingement of the hip usually occurs with activities that bring the hip close to its maximum range of motion in adduction, flexion, and internal rotation. The pain is often referred to the groin.
Diagnostic Evaluation and Differential Diagnosis
Generally, cam impingement can be diagnosed by reproducing the patient's pain during physical examination. The pain from cam impingement is increased by placing the hip into flexion and internal rotation. However, pain elicited by this maneuver is not unique to FAI, and radiographic and magnetic resonance imaging is needed to rule out other pathological conditions (e.g., osteoarthritis, fracture, tumor).
Treatment and Recommended Follow-Up
A majority of patients with cam impingement can be managed successfully with physical therapy, activity modification, and anti-inflammatories. Because FAI causes injury to the acetabular labrum and surrounding articular cartilage, degenerative arthritis of the hip will ensue. If possible, activity modification to avoid impingement may be helpful. Exercise that causes pain is not good and can further injure the joint. Surgical reduction of the area of impingement (i.e., cam bump) is now possible arthroscopically. Use of nonsteroidal anti-inflammatory medications may alleviate the pain. Last resort is THR.
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