The Effect of Wrist Flexion/Extension on Radiocapitellar Joint Kinematics During Valgus Extension of the Elbow.

Abstract

Introduction: Osteochondritis dissecans (OCD) of the capitellum is prevalent among youth baseball pitchers. Repetitive shear forces during pitching are contributing factors. During the acceleration phase of pitching, the wrist joint moves from extension to flexion. The interplay between wrist position and elbow joint biomechanics has not been thoroughly examined, particularly within the radiocapitellar joint. This study aims to elucidate how different wrist positions affect the displacement of compression forces within the radiocapitellar joint during elbow extension and examine the change in contact pressure during simulated active wrist flexion and extension.

Methods: Seven fresh frozen cadaveric upper limbs were mounted in a custom testing machine and tested under simulated throwing conditions. Radial head motion was tracked using an intra-articular thin-film pressure transducer mounted on the capitellum. The contact pressure and location of the center of force (COF) in the radiocapitellar joint were measured during three wrist positions by loading the wrist flexors and extensors: flexion, neutral, and extension.

Results: Wrist flexion, compared to the neutral wrist position, displaced the COF significantly medially between 60° and 30° of elbow flexion (p<0.05). Wrist extension slightly directed the COF laterally compared to the neutral wrist, but the differences were not significant. The total horizontal displacement between the COF during active wrist flexion and extension ranged from 1.6mm to 1.8mm. Mean contact pressure was significantly higher with the wrist in extension from 80° to 40° of elbow angle and significantly lower with wrist flexion only at a 90° elbow angle (p<0.05).

Discussion: This study demonstrated that simulated active wrist flexion shifts the COF medially, potentially reducing the risk of lateral OCD lesions. In contrast, wrist extension increases contact pressure, explaining the higher susceptibility to loading in the lateral compartment. These findings highlight the importance of wrist dynamics in pitching mechanics and suggest that minimizing wrist extension during practice may prevent OCD development.

Conclusion: Wrist positions significantly influence the biomechanical behavior of the radiocapitellar joint during elbow extension. These insights are important for developing prevention and rehabilitation strategies for throwers at risk of OCD of the capitellum.