title: Anteroinferior acetabular rim damage due to femoroacetabular impingement.
abstract: BACKGROUND
  The most common location of labral tears and chondral damage in the hip is the anterosuperior region of the acetabulum, which is associated with pain in flexion and rotation. We describe a case series of patients with labral tears, ganglion formation, and chondromalacia isolated to the anteroinferior acetabulum. Clinically, patients had pain in extension and internal rotation.
  
  
  METHODS
  Isolated anteroinferior labral hypertrophy and ganglion were first observed in a patient with coxa valga. We retrospectively reviewed clinical and radiographic records and identified nine hips in seven patients with isolated anteroinferior damage. One patient with bilateral valgus femoral head tilt after slipped capital femoral epiphysis (SCFE) had impingement of the anteromedial metaphysis on the acetabulum from 3 to 6 o'clock. Five of seven had valgus neck-shaft angles and all had acetabular anteversion with damage isolated to the anteroinferior acetabular rim.
  
  
  METHODS
  Series on the diagnostic efficacy of MR arthrogram have noted anteroinferior damage adjacent to superior acetabular rim lesions. However, these do not describe isolated anteroinferior rim damage. In addition, available case series of patients with valgus SCFE do not describe a location of impingement or intraarticular damage.
  
  
  CONCLUSIONS
  In this small case series of patients with isolated anteroinferior chondrolabral damage, there are two potential causative mechanisms: (1) primary anteroinferior impingement with femoral extension and internal rotation and (2) posterior extraarticular ischiotrochanteric impingement causing secondary anterior instability of the femur. The pathoanatomy appears to be multifactorial, necessitating an individualized treatment approach.
authors.affiliation: , Zurich, Switzerland, lisa.tibor@gmail.com.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Tibor
authors.forename: Reinhold
authors.initials: R
authors.lastname: Ganz
authors.forename: Michael
authors.initials: M
authors.lastname: Leunig
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D060906:Coxa Valga / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging / Q000473:pathology*; D005270:Femur Head / Q000000981:diagnostic imaging / Q000473:pathology*; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D016059:Range of Motion, Articular