title: Ulnohumeral chondral and ligamentous overload: biomechanical correlation for posteromedial chondromalacia of the elbow in throwing athletes.
abstract: BACKGROUND
  Previous studies have documented increased posteromedial contact forces with the elbow at lower flexion angles associated with valgus extension overload; however, the authors believe that posteromedial elbow impingement in association with valgus laxity is a complex pathological process that may occur throughout the entire throwing motion in the form of ulnohumeral chondral and ligamentous overload.
  
  
  OBJECTIVE
  Valgus laxity with the elbow at 90° of flexion may lead to chondromalacia secondary to a subtle shift in the contact point between the tip of the olecranon and the distal humeral trochlea.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Six fresh human cadaveric elbows were dissected and subjected to a static valgus load. Pressure-sensitive Fuji film measured the contact pressure, contact area, and shift in contact area across the posteromedial elbow before and after sectioning the anterior bundle of the ulnar collateral ligament.
  
  
  RESULTS
  The contact pressure between the tip of the olecranon process and the medial crista of the posterior humeral trochlea significantly increased, from an average of 0.27 ± 0.06 kg/cm² to 0.40 ± 0.08 kg/cm². The contact area also significantly decreased, from an average of 30.34 ± 9.17 mm² to 24.59 ± 6.44 mm², and shifted medially on the medial humeral crista, which corresponds to the position of the posteromedial chondral lesions that was observed in throwing athletes in the authors' clinical practice.
  
  
  CONCLUSIONS
  While simulating the early acceleration phase of the throwing motion with the elbow in 90° of flexion, the results illustrate that abnormal contact may occur as a result of valgus laxity through increased contact pressures across the posteromedial elbow between the medial tip of the olecranon and medial crista of the humeral trochlea. In addition, congruency of the ulnohumeral joint changed, as there was a statistically significant medial shift of the olecranon on the posterior humeral trochlea with the elbow at 90° of flexion after sectioning the anterior bundle of the ulnar collateral ligament.
  
  
  CONCLUSIONS
  In the throwing athlete who continues the repetitive, throwing motion despite valgus laxity from ulnar collateral ligament insufficiency, the authors believe that these results provide a plausible mechanism for injury throughout the entire throwing motion secondary to ulnohumeral chondral and ligamentous overload. As throwing athletes may produce a tremendous amount of force and subsequent chondromalacia within the posteromedial aspect of the elbow, the findings of this study illustrate the importance of prompt clinical recognition of ulnar collateral ligament insufficiency.
authors.affiliation: Hospital for Special Surgery, New York, New York, USA. osbahrd@gmail.com
authors.forename: Daryl C
authors.initials: DC
authors.lastname: Osbahr
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Dines
authors.forename: Nathan M
authors.initials: NM
authors.lastname: Breazeale
authors.forename: Xiang-Hua
authors.initials: XH
authors.lastname: Deng
authors.forename: David W
authors.initials: DW
authors.lastname: Altchek
mesh_terms: D001265:Athletic Injuries / Q000453:epidemiology* / Q000209:etiology; D001696:Biomechanical Phenomena; D002102:Cadaver; D002357:Cartilage Diseases / Q000453:epidemiology* / Q000209:etiology / Q000473:pathology; D019902:Chondrocytes / Q000473:pathology*; D006801:Humans; D006811:Humerus / Q000293:injuries* / Q000473:pathology; D056740:Olecranon Process / Q000293:injuries / Q000473:pathology; D019415:Torque; D014457:Ulna / Q000293:injuries* / Q000473:pathology