title: Correlation of pelvic incidence with cam and pincer lesions.
abstract: BACKGROUND
  The sacropelvic parameter of pelvic incidence (PI) is a position-independent anatomic parameter that regulates lumbar lordosis and pelvic orientation. While it has been extensively studied in relation to spine pathology, only a single study has correlated PI with femoroacetabular impingement (FAI).
  
  
  OBJECTIVE
  Decreased PI would be associated with an increased prevalence of cam and pincer lesions.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Measurements of the acetabulum, proximal femur, and sacropelvis were made bilaterally on 40 cadaveric specimens, for a total of 80 hips. Twenty specimens had the presence of bilateral cam deformities (alpha angle >55°), and 20 age- and sex-matched specimens had bilateral normal hips. Pincer lesions were defined as an anteversion <15°. Pelvic incidence and acetabular version were measured using standardized lateral photographs and a goniometer, respectively. Independent-samples t tests were performed to evaluate for differences in measured parameters between groups.
  
  
  RESULTS
  The mean PI was 43.1° ± 8.6° for hips with a cam lesion and 47.7° ± 9.3° for normal hips, demonstrating a significant association between decreased PI and the presence of a cam lesion (P = .02). The mean version of acetabula with pincer lesions (n = 28) was 11.4° ± 2.5°, and the mean version of normal acetabula (n = 52) was 20.1° ± 3.8°. The mean PI of hips with pincer lesions was 42.5° ± 8.5°, significantly less than that of normal hips, 47.0° ± 9.2° (P = .04).
  
  
  CONCLUSIONS
  This study supports a recent study that suggested patients with pincer impingement have a smaller PI than the healthy population, and it is the first to demonstrate a significant association between decreased PI and cam-type femoral deformity. Based on results of this study, further clinical study of the effects of pelvic geometry on FAI is warranted.
  
  
  CONCLUSIONS
  While the study results do not prove a causal relationship, it is theorized that the restriction of range of motion and biomechanical adaptations of the pelvis around the hip joints resulting from a smaller PI may affect hip development and FAI. The influence of mechanical factors beyond the hip joint in the development of FAI should be considered by clinicians.
authors.affiliation: Department of Orthopaedic Surgery, University Hospitals Case Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA jjg112@case.edu.
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Gebhart
authors.affiliation: Department of Orthopaedic Surgery, University Hospitals Case Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Streit
authors.affiliation: University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Asheesh
authors.initials: A
authors.lastname: Bedi
authors.affiliation: Midwest Orthopaedics, Rush University Medical Center, Chicago, Illinois, USA.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Bush-Joseph
authors.affiliation: Midwest Orthopaedics, Rush University Medical Center, Chicago, Illinois, USA.
authors.forename: Shane J
authors.initials: SJ
authors.lastname: Nho
authors.affiliation: Department of Orthopaedic Surgery, University Hospitals Case Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Salata
mesh_terms: D000077:Acetabulum / Q000473:pathology* / Q000503:physiopathology; D000328:Adult; D053587:Arthrometry, Articular; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D057925:Femoracetabular Impingement / Q000473:pathology* / Q000503:physiopathology; D005270:Femur Head / Q000473:pathology* / Q000503:physiopathology; D006621:Hip Joint / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular
keywords: acetabular retroversion; cam lesion; femoroacetabular impingement; pelvic anatomy; pelvic incidence; pincer lesion