Radial Head Lag: A Possible Biomechanical Mechanism for Osteochondritis Dissecans of the Capitellum in Baseball Pitchers

Background: Osteochondritis dissecans (OCD) of the capitellum is common in throwing athletes and believed to result from repetitive overloading on radiocapitellar (RC) joint, although cause mechanism remain unclear. The torsional forces (moments) generated by triceps during elbow extension pull only ulna; therefore, radial head moves passively across effectively “dragged along” ulna. Any laxity proximal radioulnar joint could lead asynchronous motion between radius ulna, resulting lagging behind coronoid possibly malarticulating with such motion. Hypothesis: Radial lags ulnohumeral simulated throwing. Study Design: Controlled laboratory study. Methods: A total 8 cadaveric elbows were tested under throwing, including active pulling valgus stress, as well passive stress serve a reference. Ulnohumeral was tracked using video camera. an intra-articular, thin-film pressure sensor mounted capitellum, longitudinal movement center force (COF) measured. compared for each 10° 90° 20°. Results: Elbow reached angular velocity 366 deg/s. significantly lagged its at every angle examined 70° 20° ( P < .001). maximal lag mean 4 mm (range, 2-7 mm). In other words, RC Conclusion: This study describes novel phenomenon: rapid extension, baseball pitching, that seen According new proposed theory OCD lesion development, this should incongruency elevated shear due edge loading. Clinical Relevance: We propose biomechanical explanation pitchers: lag. Understanding process first step efforts prevent injury.