summary Femoroacetabular impingement (FAI) is the abnormal contact between the femur and acetabulum which may lead to labral damage, various degrees of chondral injury and progressive hip pain. Diagnosis is made radiographically with hip radiographs showing an aspherical femoral (Cam impingement) or anterosuperior acetabular overhang (Pincer impingement), or a combination of both. Treatment may be nonoperative or operative depending on the chronicity of symptoms, patient age, patient activity demands, and development of secondary insult to the hip joint (i.e. labral tear, secondary osteoarthritis). Epidemiology Incidence femoral and acetabular deformity common in general population and often asymptomatic may become more apparent with participation in activities requiring extreme range of motion (ballet, gymnastics, martial arts) Etiology Pathophysiology mechanism of injury proximal femur abuts acetabulum with range of motion, especially during flexion pathoanatomy Cam impingement login to view 8 more bullets Pincer impingement login to view 8 more bullets combined Cam/Pincer impingement login to view 3 more bullets Associated injuries labral degeneration and tears cartilage damage and flap tears secondary hip osteoarthritis Anatomy Osteology highly congruous joint formed by Acetabulum login to view 1 more bullet Femur login to view 1 more bullet Muscles 5 major muscle groups acting across hip hip flexors, extensors, abductors, adductors, and external rotators Capsule and Ligaments 3 ligaments of the form joint capsule iliofemoral ligament (Y ligament of Bigelow) ischiofemoral ligament pubofemoral ligament labrum horseshoe-shaped fibrocartilaginous tissue extending around periphery of acetabulum connected by transverse acetabular ligament at inferior acetabulum increases acetabular volume and provides suction seal ligamentum teres extends from cotyloid fossa to femoral head negligible contribution to vascular supply of femoral head in adult Presentation Symptoms common symptoms activity related groin or hip pain, exacerbated by hip flexion difficulty sitting mechanical hip symptoms of clicking or popping can present with gluteal or trochanteric pain login to view 1 more bullet Exam motion limited hip flexion (<90 degrees), especially with internal rotation (<5 degrees) anterior impingement test (flexion, adduction, internal rotation) elicits pain inspection externally rotated extremity login to view 1 more bullet Imaging Radiographs recommended views AP with true lateral view (hip placed in 15 degrees of internal rotation) optional views Dunn or modified Dunn view false profile view login to view 2 more bullets findings asphericity and contour of femoral head and neck login to view 2 more bullets examine for acetabular protrusio, retroversion, and coxa profunda login to view 3 more bullets measurements alpha angle login to view 8 more bullets head-neck offset ratio login to view 9 more bullets lateral center-edge angle (angle of Wiberg) login to view 1 more bullet anterior center-edge angle login to view 1 more bullet acetabular index or Tonnis roof angle login to view 1 more bullet CT indications can be used as adjunct to assess for structural abnormalities views 3D reconstructions aid in pre-operative assessment MRI and/or MR arthrogram indications best modality to evaluate for articular cartilage and labral damage can assess anatomy of femoral head/neck junction abnormalities views ensure MRI is formatted to be in-line with femoral neck findings labral fraying or frank tears, chondral damage, subchondral cyst formation Differential Various pathologies will refer pain to the hip region Ischiofemoral impingment adductor strains and athletic pubalgia lumbar radiculopathy iliopsoas pathology hip instability Treatment Nonoperative activity modification, PT, NSAIDs indications login to view 2 more bullets modalities login to view 2 more bullets Operative arthroscopic osteoplasty indications login to view 3 more bullets outcomes login to view 2 more bullets Arthroscopic labral repair or reconstruction indications login to view 4 more bullets open surgical hip dislocation and osteoplasty indications login to view 3 more bullets periacetabular osteotomy indications login to view 1 more bullet hip arthroplasty indications login to view 2 more bullets Techniques Arthroscopic osteoplasty approach arthroscopic approach to the hip soft tissue capsulotomy required to access peripheral component to address CAM labral repair/refixation required following acetabuloplasty if labrum is destabilized bony work trim femoral head/neck in Cam impingement acetabular rim trimming followed by labral debridement vs repair/reconstruction login to view 1 more bullet outcomes equivalent success compared to open procedure complications neurapraxias associated with hip arthroscopy Ganz open surgical hip dislocation and osteoplasty approach Kocher-Langenbeck incision while in lateral decubitus position, gluteus maximus split digastric "trochanteric flip" performed and fragment mobilized anteriorly capsulotomy performed, hip dislocated anteriorly, ligamentum teres likely transected allows safe access to proximal femur and acetabulum alternatively, a direct anterior approach may be utilized but grants limited visualization to posterior acetabulum bony work same as arthroscopic osteoplasty soft tissue labral repair/refixation/reconstruction required following acetabuloplasty if labrum is destabilized outcomes provides wide exposure of femoral head and acetabulum while preserving all external rotators and blood supply to femoral head (medial circumflex femoral artery) no increase in AVN risk median expected time to return to sports is 7 months in adolescent athletes professional athletes without osteoarthritis are expected to return-to-play at the same level at a rate of >85-90% complications trochanteric hip pain Combined arthroscopic and limited open approach combines aspects of both procedures to gain access to entire femur and acetabulum early results promising Complications Femoral neck fracture at risk during femoroplasty risk is minimized by limiting depth of femoral head-neck osteoplasty to <30% of femoral neck diameter, using multiple fluoroscopy views of femoral neck during procedure Heterotopic ossification Residual deformity following arthroscopic treatment use of multiple fluoroscopy views Postop capsular deficiency symptoms pain different than preoperative symptoms pain or apprehension with hip extension and ER loss of recoil with log roll gross instability risk factor no capsular closure trauma overaggressive rehab failure to comply with ROM restrictions treatment capsular repair capsular reconstruction with graft login to view 1 more bullet Prognosis Natural history believed to lead to early onset hip dysfunction and arthritis Relative femoral retroversion (anteversion < 5°) is associated with persistent dysfunction after isolated hip arthroscopy