Isolated Musculocutaneous Nerve Injury in a Professional Baseball Player: A Case Report

Introduction: Musculocutaneous nerve lesion in a throwing athlete is a rare condition. We report the case of a professional baseball pitcher with an isolated musculocutaneous nerve lesion that occurred during a pitching motion. Case Presentation: The patient had radiating pain in the upper arm and weakness of elbow flexion. Physical examination revealed flaccid paralysis of the biceps brachii muscle and paresthesia in the right lateral forearm. Musculocutaneous nerve injury was suspected. Because some signs of recovery were observed within a few days, the patient received non-operative management. Nerve conduction studies at 2 weeks after the injury showed low-amplitude compound muscle action potential of the right biceps brachii muscle by stimulation of the musculocutaneous nerve. Needle electromyography showed markedly reduced motor unit potential recruitment in the biceps brachii muscle. He was diagnosed as having isolated musculocutaneous nerve injury. At 2 months after the injury, the muscle contraction and strength of the biceps brachii muscle improved. At 7 months after the injury, muscle weakness was fully recovered. His pitching ability returned to that of a competitive player. Conclusion: Because the neuroparalysis was incomplete and began to recover within a few days, we considered the pathology of this injury to be incomplete axonotmesis, which was successfully treated conservatively. Keywords: Isolated musculocutaneous nerve injury, baseball pitcher, axonotmesis.

Training with Lighter Baseballs Increases Velocity Without Increasing Injury Risk

Objectives: Pitch velocity has become an increasingly popular metric by which pitchers are graded and compared. Training programs that utilize weighted balls have been effective in increasing velocity but at the cost of increased injury risk. The purpose of this study was to determine if a baseball pitcher-training program utilizing lighter baseballs could increase fastball velocity without increasing injury risk. The author’s hypothesized that the training program with lighter baseballs would increase fastball velocity without causing injuries during the training program to the participants Methods: All baseball pitchers who participated in a 15-week pitching mechanic and velocity training program were included. Training program was broken down into three phases, and each participant went through the same program. Lighter balls (4oz and 3oz) and standard baseballs (5oz) were utilized as part of the training program. Weighted (heavier) balls were not used. Velocity was measured at four time points throughout the program. Injury rates for all players were recorded throughout the entire program. Results: 48 male pitchers aged 10-17 (average age: 14.7 +/- 1.8) years started the program and 44 had complete data and were included in the analysis. No pitcher sustained a baseball-related injury while participating in the training program (one player broke his ankle playing basketball, one player moved, one did not have baseline velocity data, and one experienced biceps soreness after participating in back to back showcases against recommendations). Fastball velocity increased by an average of 4.8mph (95% confidence intervals 4.1 - 5.5mph). Overall 43/44 players (98%) had an increase in fastball velocity over the course of the program. Conclusions: A 15-week baseball pitcher-training program with lighter baseballs significantly improved pitching velocity without significantly increasing injuries. Lighter baseballs should be considered instead of weighted baseballs when attempting to increase a pitcher’s velocity.

Quantification of a Ball-Speed Generating Mechanism of Baseball Pitching Using IMUs

The purpose of this study was to propose a methodology which quantifies the ball-speed generating mechanism of baseball pitching with the use of inertial measurement units (IMUs). IMUs were attached to the upper trunk, upper arm, forearm, and hand segments. The initial orientation parameters of each segment were identified using the differential iteration method from the acceleration and angular velocity of the sensor coordinate system output by IMUs attached to each segment. The motion of each segment was calculated and the dynamic contributions were then calculated. The motion of a baseball pitcher, who was instructed to throw at the target, was measured with a motion capture (mocap) system and IMUs. The results show that quantitative analysis of the ball-speed generation mechanism by the proposed method is almost similar to that conducted by the mocap system. In the future, this method will be employed to evaluate the ball-speed generation mechanism outside controlled laboratory conditions in an effort to help understand and improve the player’s motion.