What is Acetabular Pincer Deformity?
Acetabular pincer deformity, also referred to as pincer impingement, is an abnormality of the acetabulum (hip socket) where the acetabulum is excessively deep or over covers the femoral head, resulting in impingement of the femoral neck and rupture of the labrum.
The hip joint is a ball-and-socket joint in which the head of the femur forms the ball, and the pelvic acetabulum forms the socket. The joint surface is covered by smooth articular cartilage that cushions and enables smooth movement of the joint. A fibrous cartilage ring called the labrum lines the acetabular socket. It deepens the cavity, increasing the stability and strength of the hip joint.
Acetabular pincer deformity involves the acetabular side of the hip joint and occurs when the socket or acetabulum rim has overgrown and covers too much of the femoral head, resulting in the labral cartilage being pinched. Pincer impingement may also occur when the hip socket is abnormally angled backwards, causing abnormal impact between the femoral head and the rim of the acetabulum.
Risk Factors for the Development of Acetabular Pincer Deformity
A risk factor is something that is likely to increase a person’s chance of developing a disease or condition. Risk factors for developing acetabular pincer deformity may include the following:
- Congenital hip dislocation
- Anatomical abnormalities of the hip joint at birth or during adolescent development
- Legg-Calves-Perthes disease
- Trauma to the hip
- Inflammatory arthritis
- Heavy laborers
- Repetitive hip flexion
- Athletes such as football players, weightlifters, and hockey players
Signs and Symptoms of Acetabular Pincer Deformity
Signs and symptoms of acetabular pincer deformity include:
- Pain, which may be a dull ache or a sharp pain
- Groin pain associated with hip activity
- Complaints of pain in the front, side or back of the hip
- A locking, clicking, or catching sensation in the hip
- Pain in the inner hip or groin area after prolonged sitting or walking
- Difficulty walking uphill
- Restricted hip movement
- Lower back pain
- Pain in the buttocks or outer thigh area
Acetabular pincer deformity is diagnosed based on a review of your medical history, a thorough physical examination to check for any abnormality in hip motion and gait/walking pattern, and diagnostic studies, such as X-rays, MRI scans, and CT scans to check for any anatomical differences in the alignment of the hip bone which confirms the diagnosis.
Treatment for Acetabular Pincer Deformity
Most cases of acetabular pincer deformity can be treated with non-surgical interventions. Surgical intervention is only reserved for severe cases of pincer deformity and when non-surgical treatment has failed to achieve the desired results.
- Activity modification
- Non-steroidal anti-inflammatory drugs (NSAIDs)
- Corticosteroid injections
- Physical therapy
Acetabuloplasty is the surgical procedure performed for the treatment of pincer deformity non-responsive to conservative treatment. The surgery is usually performed arthroscopically in a minimally invasive technique in which an arthroscope, a narrow tube with a tiny camera and light source on the end, and miniature instruments are inserted through small incisions over the hip to access the acetabulum and correct abnormalities. The procedure involves trimming the area of over coverage or pincer lesion on the acetabular side to relieve bony impingement and reshaping the acetabulum to enable normal hip motion. Additionally, damage to the soft-tissue structures such as cartilage and labrum, if any are also repaired during the operation.
Surgery is immediately followed by rehabilitation and involves a focused physical therapy program under the guidance of a physical therapist to improve hip movement and strength.