Femoroacetabular Impingement Is Associated With Sports-Related Posterior Hip Instability in Adolescents: A Matched-Cohort Study

Am J Sports Med. 2016 Sep;44(9):2299-303. doi: 10.1177/0363546516651119. Epub 2016 Jun 16.


Background: Femoroacetabular impingement (FAI) deformity has been associated with posterior hip instability in adult athletes.

Purpose: To determine if FAI deformity is associated with posterior hip instability in adolescents, the femoral head-neck junction or acetabular structure in a cohort of adolescent patients who sustained a low-energy, sports-related posterior hip dislocation was compared with that in a group of healthy age- and sex-matched controls with no history of hip injury or pain.

Study design: Cross-sectional study; Level of evidence, 3.

Methods: We identified 12 male patients (mean age, 13.9 years; range, 12-16 years) who sustained a sports-related posterior hip dislocation and underwent a computed tomography (CT) scan after closed reduction. For each patient, 3 age- and sex-matched healthy controls were identified. Femoral head-neck type was assessed by measurement of the alpha angle on the radially oriented CT images at the 12-, 1-, 2-, and 3-o'clock positions. Age, body mass index (BMI), alpha angle at each position, acetabular version, Tönnis angle, and lateral center-edge angle (LCEA) on the involved hip in the dislocation group were compared with those of the matched controls using a mixed-effects model. A logistic regression analysis using a generalized estimating equation was used to compare the percentage of subjects with cam-type FAI deformity (alpha angle >55°) in each group.

Results: The dislocation and control groups were similar in age distribution and BMI (P > .05). The mean alpha angles were statistically significantly higher in the dislocation group compared with the control group at the superior (46.3° ± 1.1° vs 42.7° ± 0.6°; P = .0213), superior-anterior (55.5° ± 1.9° vs 46.0° ± 1.3°; P = .0005), and anterior-superior (54.9° ± 1.5° vs 48.9° ± 1.0°; P = .0045) regions. Cam deformity was present in a larger proportion of patients in the dislocation group than in the control group (P < .0035). An alpha angle greater than 55° was present in 16.7% of the dislocation group and 0% of the control group at the 12-o'clock position (P = .1213), 41.7% versus 0% at the 1-o'clock position (P = .0034), 58% versus 6% at the 2-o'clock position (P = .0004), and 25% versus 2.8% at the 3-o'clock position (P = .0929). Acetabular anteversion was lower in the dislocation group (9.6° ± 1.4°) compared with the control group (15.1° ± 0.8°) (P = .0068). Mean acetabular LCEA was within a normal range in both groups.

Conclusion: A significantly higher mean alpha angle from the superior to the anterior-superior regions of the femoral head-neck junction and lower acetabular version were found in adolescents who sustained low-energy, sports-related posterior hip dislocations.

Keywords: adolescent; femoroacetabular impingement; hip dislocation.

MeSH terms

  • Adolescent
  • Athletes / statistics & numerical data
  • Athletic Injuries / epidemiology*
  • Athletic Injuries / etiology
  • Athletic Injuries / pathology
  • Child
  • Cohort Studies
  • Cross-Sectional Studies
  • Femoracetabular Impingement / epidemiology*
  • Femoracetabular Impingement / ethnology
  • Femoracetabular Impingement / pathology
  • Femur Head / pathology*
  • Femur Neck / pathology*
  • Hip Dislocation / epidemiology*
  • Hip Dislocation / etiology
  • Hip Dislocation / pathology
  • Humans
  • Male
  • Tomography, X-Ray Computed