Effect of various forearm axially rotated postures on elbow load and elbow flexion angle in one-armed arrest of a forward fall

Background: Falling onto the outstretched hand is a major cause of upper extremity injury. The overall objectives of this study were to develop an experimental model for elbow load during a simulated fall onto one-armed arrest using three different forearm axially rotated postures as alternative fall arrest strategies. Additionally, the relationship between the elbow flexion angle and different axially rotated postures were also investigated. Methods: Fifteen healthy young male Taiwanese graduate students with an average age of 23 years were studied. Subjects performed a one-armed arrest of a 5 cm fall onto a force plate. Each subject fell onto the force plate with his forearm 45° axial externally rotated (ER), non-rotated (NR), and 45° axial internally rotated (IR) postures. Kinematics and kinetics of the upper extremity were calculated and analyzed by using laboratory-developed motion analysis procedures. Findings: The valgus-varus shear forces in the ER group were 1.4 times greater than the NR group, and 2.7 times greater than the IR group. The elbow joint remained at almost full extension in the ER (3.9°) group, while elbow flexion angle was observed in the NR (24.6°) and IR (40.3°) groups. Interpretation: A fall onto the outstretched hand with an externally rotated forearm should be avoided in order to reduce excessive valgus-varus shear force on the elbow joint. Knowledge of elbow kinematics and kinetics during a forward fall with various forearm axially rotated posture may be helpful in preventing injuries.