Review Question - QID 212019

This patient's exam and imaging are consistent with pincer-type femoroacetabular impingement. Classic findings include anterosuperior labral contusion/tearing and chondral damage to the posteroinferior acetabulum.

Femoroacetabular impingement (FAI) is now a well-described process of mechanical conflict between the femur and acetabulum. This can lead to damage to the interposed labrum and articular surface and is theorized to lead to arthritic change in the hip. The pattern of wear is reflective of the underlying structural abnormalities. With pincer-type impingement, the anterolateral over-coverage of the femoral head leads to crushing of the labrum (coup), and resulting levering of the femoral head reciprocally into the posteroinferior acetabular cartilage (countrecoup). Cam-type impingement differs in that the aspherical femoral head-neck is forced into the spherical acetabulum, causing chondrolabral separation and cartilage damage. While not in this patient, both these types of impingement most commonly coexist, which is termed mixed-type impingement.

Parvizi et al. provided an early overview on FAI and management options. The authors detail the pathoanatomy of each type of impingement and the efficacy of open surgical osteoplasty. They postulate that this may help delay or prevent the development of osteoarthritis.

Matsuda et al. performed a systemic review of surgical techniques in addressing femoroacetabular impingement. At the time, only 18 level III/IV studies fit the inclusion criteria, providing for a total of 1070 hips. The authors showed good outcomes with surgical dislocation, mini-open, and arthroscopic techniques, but noted that arthroscopy was associated with fewer major complications.

Byrd and Jones reviewed outcomes after arthroscopic labral repair using a labral base refixation technique. Of the 38 hips, 92% had excellent results. The authors found that in the four individuals who required subsequent arthroscopic management, the labrum was healed in all cases - a testament to the efficacy of labral repair.

Konan et al. described a acetabular chondral injury classification. The authors divided the acetabulum into a 9-square grid and assessed the damage on a scale analogous to Outerbridge grade. They found that the system was both simple to apply and demonstrated a high inter-observer reliability.

Figure A is an AP pelvis radiograph showing bilateral acetabular over-coverage and cephalad retroversion. Illustration A demonstrates the Flexion Adduction Internal Rotation (FADIR) test, which reproduces the impingement of the hip. Illustrations B depicts pincer-type impingement, in which the labrum is being crushed between the acetabular rim and femoral neck, levering the femoral head into the acetabular cartilage inferiorly. Contrast this with Illustration C, which depicts cam-type impingement.

Incorrect Answers:
Answer 2: This would be more characteristic of iliopsoas, or internal, impingement. FAI-associated labral tears involve the anterosuperior labrum, classically between the 10-2 o'clock positions.
Answer 3: These findings would be seen in greater trochanteric pain syndrome, with varying degrees of abductor weakness and lateral hip pain.
Answer 4: These findings would be more consistent with an individual with hip instability.
Answer 5: This is characteristic of Cam-type FAI. The asphericity of the femoral head causes chondro-labral separation and chondral damage.