title: Low Prevalence of Anterior and Posterior Cruciate Ligament Injuries in Patients With Achondroplasia.
abstract: BACKGROUND
  Anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) injuries and their subsequent reconstructions are common in the general population, but there has been no research regarding ACL or PCL injuries in patients with achondroplasia, the most common skeletal dysplasia. Our goals were to (1) evaluate the prevalence of ACL and PCL injuries in adolescents and adults with achondroplasia, (2) compare this prevalence with that reported for the general population, (3) determine how many patients with ACL or PCL injuries underwent ligament reconstruction as treatment, and (4) determine patient activity levels as they relate to the rate of ACL/PCL injuries and reconstructions.
  
  
  METHODS
  We reviewed medical records of 430 patients with achondroplasia seen in the senior author's clinic from 2002 through 2014. Demographic data were reviewed, as well as any documentation of ACL or PCL injury or reconstruction. We called all 430 patients by telephone, and 148 agreed to participate in our survey, whereas 1 declined. We asked these patients about their history of ACL or PCL injury or reconstruction, as well as current and past physical activity levels.
  
  
  RESULTS
  No ACL or PCL injuries were found on chart review. One patient reached by telephone reported an ACL injury that did not require reconstruction. This yielded a theoretical prevalence of 3/430 (0.7%). Of the 148 patients surveyed, 43 (29%) reported low physical activity, 75 (51%) reported moderate physical activity, and 26 (17%) reported high physical activity. There was no significant difference in the rate of ACL injury when stratified by physical activity level (P=0.102).
  
  
  CONCLUSIONS
  ACL and PCL injuries and reconstructions are extremely rare in patients with achondroplasia, which cannot be completely ascribed to a low level of physical activity. One possible explanation is that patients with achondroplasia, on an average, have a more anterior tibial slope compared with those without achondroplasia, which decreases the force generated within the ACL and may protect against ACL injury. Further research is needed to explore possible causes.
  
  
  METHODS
  Level IV-retrospective review.
authors.affiliation: *Department of Orthopaedic Surgery, The Johns Hopkins University/Johns Hopkins Bayview Medical Center †The Johns Hopkins School of Medicine ‡The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
authors.forename: Jaysson T
authors.initials: JT
authors.lastname: Brooks
authors.forename: Alim F
authors.initials: AF
authors.lastname: Ramji
authors.forename: Tatyana A
authors.initials: TA
authors.lastname: Lyapustina
authors.forename: Mary T
authors.initials: MT
authors.lastname: Yost
authors.forename: Michael C
authors.initials: MC
authors.lastname: Ain
mesh_terms: D000130:Achondroplasia / Q000150:complications* / Q000453:epidemiology; D000293:Adolescent; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D010043:Outcome and Process Assessment, Health Care; D016119:Posterior Cruciate Ligament / Q000293:injuries / Q000601:surgery; D015995:Prevalence; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology