Hip Impingement

Hip impingement, also known as femoroacetabular impingement, is the abutment of the acetabular rim and the proximal femur.

Hip impingement is increasingly recognized as a common etiology of hip pain in athletes, adolescents, and adults. It injures the labrum and articular cartilage, and can lead to osteoarthritis of the hip if left untreated. Patients with hip impingement often report anterolateral hip pain.

Common aggravating activities include prolonged sitting, leaning forward, getting in or out of a car, and pivoting in sports. The use of flexion, adduction, and internal rotation of the supine hip typically reproduces the pain.

Radiography, magnetic resonance arthrography, and injection of local anesthetic into the hip joint confirm the diagnosis. Pain may improve with physical therapy.

Treatment often requires arthroscopy, which typically allows patients to resume premorbid physical activities. An important goal of arthroscopy is preservation of the hip joint. Whether arthroscopic treatment prevents or delays osteoarthritis of the hip is unknown.

In the early stages, there may be no symptoms associated with hip impingement or symptoms may be mild or vague.

There are three types of hip impingement: pincer, cam, and combined impingement.

• Pincer - This type of impingement occurs because extra bone extends out over the normal rim of the acetabulum. The labrum can be crushed under the prominent rim of the acetabulum.
• Cam - In cam impingement, the femoral head is not round and cannot rotate smoothly inside the acetabulum. A bump forms on the edge of the femoral head that grinds the cartilage inside the acetabulum.
• Combined - Combined impingement just means that both the pincer and cam types are present.

Some typical symptoms include:

• Stiffness in the thigh, hip, or groin.
• The inability to flex the hip beyond a right angle.
• Pain in the groin area, particularly after the hip has been flexed (such as after running or jumping or even extended periods sitting down).
• Pain in the hip, groin, or lower back that can occur at rest as well as during activity.

There are two main abnormalities that can cause hip impingement:

1. Abnormalities in femoral head: Any abnormality that affects shape of femoral head causes it to not properly fit inside the socket of acetabulum and hence, the resulting symptoms from activities like playing, tying shoes.
2. Abnormalities in acetabulum: If the acetabular rim is far beyond the normal boundaries due to any pathological reason, there can be problems for the femoral head to properly fit in the socket and can create mechanical disturbances in the normal functioning of the joints.

In some cases, both the reasons can be culprit.

Some of the diseases that cause such disturbances around joint include:

• Legg-calve Perthes disease which is the avascular necrosis around hip joint.
• Slipped Capital Femoral Epiphysis.
• Coxa Vara in which both the bones of hip joint do not grow at the normal pace as a result, discrepancy results.
• Repetitive activity involving recurrent movement of the legs beyond the normal range of motion may cause hip impingement, which has been observed in certain athletes (football, baseball, soccer, tennis, hockey, lacrosse players, dancers, and golfers).
• An injury may also cause symptoms of hip impingement.
• Some persons are predisposed to impingement by bony abnormalities, which can be congenital or developmental. Excessive overhang of the anterior acetabulum causes pincer impingement, which generally occurs during flexion or internal rotation. Exostosis or bony overgrowth of the femoral head and neck causes cam impingement. Although most persons with FAI have such bony abnormalities, some patients with normal radiography findings may have FAI and a labral tear.

Diagnosis of hip impingement is on the basis of history, physical examination and imaging modalities. Clues from history that point to disease include:

1. Anterolateral hip pain.
2. Patients pointing to the site of pain as a cup with the thumb and forefinger shaped as “C” called as “C sign”.
3. Factors that aggravate the pain include: prolonged sitting, rising from the seat, getting into and out of the car and leaning forward.
4. Patient is sharpened by turning or pivoting towards the affected side.
5. Pain is usually gradual and progressive.

Clues from the physical examination include:

• On Inspection of hips: Asymmetry suggests SI joint dysfunction or leg-length discrepancy, either of which can cause SI joint pain, pubic symphysis pain, or muscle strain.
• On Palpation of bone landmarks and muscles: Tenderness indicates that tissue is involved. Tenderness over the greater trochanter suggests trochanteric bursitis, which can coincide with intra-articular hip disorder; mass suggests tumor.

Looking for the Range of motion (flexion, extension, abduction, adduction, internal and external rotation)

• Assess for pain; localize pain;
  • Pain in a stretched muscle indicates strain; pain in groin suggests intra-articular hip disorder; pain with slight motion is concerning for septic arthritis.
• Passive (examiner moves the hip): Limitation of motion reflects severity of condition; pain helps to localize source of pain.
• Active (patient moves), resisted (examiner resists motion to test muscle strength): Weakness or pain in muscle suggests strain.
• Patrick (FABER) test;
  • Groin pain indicates an iliopsoas strain or an intra-articular hip disorder; SI pain indicates SI joint disorder; posterior hip pain suggests posterior hip impingement.
• FADIR test;
  • Reproducing the patient's anterolateral hip pain is consistent with FAI.
• Log roll (examiner rolls the supine leg back and forth);
  • Groin pain suggests an intra-articular disorder; posterior pain suggests posterior muscle strain
• Patient hops on the involved leg;
  • Pain can occur with strain, FAI, or other intra-articular disorder, but is concerning for hip stress fracture
• Examination of lower back, abdomen, and pelvis;
  • Certain conditions can refer pain to the hip; check for fever or tachycardia, which suggest septic arthritis.

Imaging modalities for diagnosis include:

1. X-Ray: producing two-dimensional images of the hip joint. They show abnormal shape of bones and also features of arthritis, Modified Dunn’s view is suggested in which hip is flexed 90̊ and abducted to 20̊ should be ordered.
2. Magnetic Resonance Arthrography: To evaluate the labrum and look for labral tears.
3. CT Scans: More detailed than a plain x-ray, CT scans help your doctor see the exact abnormal shape of your hip.

Conservative treatment for hip impingement includes:

1. Reducing levels of physical activity
2. Anti-inflammatory medication
3. Physiotherapy: Physical Therapy optimizes alignment and mobility of the joint, thereby decreasing excessive forces on irritable or weakened tissues. It may also identify specific movement patterns that may be causing injury.
4. Surgical techniques: Various surgical techniques have been developed with the goal of preserving the hip joint. 

Surgery may be arthroscopic or open, peri-acetabular or rotational osteotomies being two common open surgical techniques employed when an abnormal angle between femur and acetabulum has been demonstrated. These primarily aim to alter the angle of the hip socket in such a way that contact between the acetabulum and femoral head are greatly reduced, allowing a greater range of movement. Femoral sculpting may be performed simultaneously, if required for a better overall shape of the hip joint. 

• Predictors of favorable outcomes from arthroscopy include mechanical symptoms (e.g., locking, catching, popping) and sharp pain. The presence of osteoarthritis reduces the likelihood of a positive result.
• Risks of surgery include neurovascular injury, infection, deep venous thrombosis, and heterotopic bone formation. Theoretic risks unique to arthroscopic treatment of FAI are femoral neck fracture and avascular necrosis of the femoral head, but few cases have been reported.

It is hypothesized that arthroscopic treatment of FAI can prevent or delay the onset or progression of osteoarthritis of the hip, but this has yet to be demonstrated with long-term clinical follow-up.

There are currently no formal prevention programs for hip impingement.

Certain sports cause a lot of wear and tear at the hip joint like: football, hockey, netball, rugby, dancing, swimming. Patients with femoroacetabular impingement should play these sports with utmost caution.

Also, they should manage their lifestyle according to what suits them best as the joint anatomy is different for each individual.

It is best to speak with your doctor regarding alternative remedies for hip impingement, as pain needs to be managed accordingly.

The day after surgery, patients start hydrotherapy to work on range of motion exercises to the hip and gentle strengthening. 

Usually, the patients are encouraged to use 2 crutches for a period of 2 to 4 weeks (depending on the extent of surgery). After that, the emphasis is on a low impact exercise program such as using an exercise bike and cross trainer. Swimming and pool based exercises are also encouraged.

This low impact exercise program continues for 2 to 3 months following the operation. After this period, impact exercises are started such as jogging and gradually built up.

Lifestyle modifications are necessary in order to cope with hip impingement.

When symptoms first occur, it is helpful to be self-vigilant to identify factors that are causing pain and avoiding them can usually help to prevent distress caused by pain. Over-the-counter anti-inflammatory medicines (ibuprofen, naproxen) may help.

If your symptoms persist, you will need to see a doctor to determine the exact cause of your pain and provide treatment options. The longer painful symptoms go untreated, the more damage FAI can cause in the hip.

The main complications of hip impingement are those that are associated with surgical repair.

Specific complications that can occur following hip arthroscopy include:

• Infection
• Nerve Damage
• Hemarthrosis
• Blood Clots
• Avascular Necrosis
• Failure to Relieve Pain

Infection: Infections can occur superficially at the portal insertion sites or in the joint space of the hip, a more serious infection. 

Nerve Damage: Trauma to nerves may be temporary or permanent and can cause numbness, tingling, pain, and weakness. The nerves most at risk for damage include lateral femoral cutaneous from portal insertion and pudendal and sciatic nerve from traction.

Hemarthrosis: A condition caused by excess bleeding into the joint after the surgery is completed. This may require additional arthroscopic surgery to irrigate the joint and evacuate the blood.

Blood Clots: These can form in the calf muscles and can travel to the lung (Pulmonary embolism). These can occasionally be serious and even life threatening. If you get calf pain or shortness of breath at any stage, you should notify your surgeon.

Avascular Necrosis: AVN of the femoral head causes bone death due to lack of blood supply to the bone.

Failure to Relieve Pain: This is rare but may occur especially if some pain is coming from other areas such as the spine.