Femoroacetabular Impingement Is Associated With Sports-Related Posterior Hip Instability in Adolescents: A Matched-Cohort Study.
Femoroacetabular impingement (FAI) deformity has been associated with posterior hip instability in adult athletes.



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.



Cross-sectional study; Level of evidence, 3.



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.



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.



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.
Sports Medicine Center and Department of Orthopaedic Surgery, Children's Hospital Colorado, Aurora, Colorado, USA.
Stephanie W
SW
Mayer
Department of Orthopaedic Surgery, Hospital Pequeno Principe-Curitiba, Curitiba, Brazil.
João Caetano Munhoz
JC
Abdo
Musculoskeletal Research Center and Department of Orthopaedic Surgery, Children's Hospital Colorado, Aurora, Colorado, USA.
Mary K
MK
Hill
Musculoskeletal Research Center and Department of Orthopaedic Surgery, Children's Hospital Colorado, Aurora, Colorado, USA.
Lauryn A
LA
Kestel
Department of Pediatrics, Children's Hospital Colorado, Aurora, Colorado, USA.
Zhaoxing
Z
Pan
Department of Orthopaedic Surgery, Boston Children's Hospital, Boston, MA, USA Eduardo.Novais@childrens.harvard.edu.
Eduardo N
EN
Novais
D000293:Adolescent; D056352:Athletes / Q000706:statistics & numerical data; D001265:Athletic Injuries / Q000453:epidemiology* / Q000209:etiology / Q000473:pathology; D002648:Child; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D057925:Femoracetabular Impingement / Q000453:epidemiology* / Q000208:ethnology / Q000473:pathology; D005270:Femur Head / Q000473:pathology*; D005272:Femur Neck / Q000473:pathology*; D006617:Hip Dislocation / Q000453:epidemiology* / Q000209:etiology / Q000473:pathology; D006801:Humans; D008297:Male; D014057:Tomography, X-Ray Computed
adolescent; femoroacetabular impingement; hip dislocation