2017 ISAKOS Biennial Congress ePoster #2411

 

Do Junior High School Rubber Baseball Player Have Fewer Shoulder And Elbow Injuries Than Hardball Pitchers?

Seiji Watanabe, MD, Toon, Ehime JAPAN
Toshiaki Takahashi, MD, PhD, Prof., Matsuyama, Ehime JAPAN
Jun Takeba, MD, PhD, Toon, Ehime JAPAN
Hiromasa Miura, MD, PhD, Prof., Toon, Ehime JAPAN

Ehime University Graduate School of Medicine, Toon, Ehime, JAPAN

FDA Status Not Applicable

Summary

In this study, OCD of the elbow was slightly less common and the range of motion in the shoulder and elbow joints was better in rubber baseball pitchers than in hardball pitchers, suggesting that rubber baseball can reduce the burden on shoulders and elbows.

Abstract

Do junior high school rubber baseball pitchers have fewer shoulder and elbow injuries than hardball pitchers?

Introduction

In Japan, junior high school students play both rubber baseball, in which soft rubber balls are used, and hardball, in which regular hard baseballs are used. Rubber baseball is an official extracurricular sport in junior high schools in Japan. Soft rubber balls were developed approximately 100 years ago in Japan. They are covered by rubber and 10g lighter than regular balls. Their diameter is 4 mm smaller than that of regular balls. Consequently, soft rubber balls are easier for children to throw. If they hit the body, the pain is relatively mild, and the risk of trauma, including fractures, is low.
In the present study, we examined the prevalence of shoulder and elbow injuries in first-year male senior high school students who had been rubber baseball or hardball pitchers during junior high.

Subjects and methods
We examined the musculoskeletal system of 258 first-year students on senior high school hardball teams soon after they entered senior high school. There were 75 students who had been rubber baseball pitchers when they were in junior high school (Group A) and 60 students who had been hardball pitchers when they were in junior high school (Group B). The prevalence of shoulder and elbow disorders and range of motion in the shoulder, elbow and hip joints were compared between these two groups. Diagnoses were made based on the physical examination of the shoulder and elbow as well as ultrasonography of the elbow. The presence or absence of shoulder or elbow disorders and range of motion were compared between the two groups using the chi-square test and Mann-Whitney U test, respectively.

Results

No significant difference was observed in height, body weight, body mass index, and number of years spent as a pitcher between the two groups. One student in Group A (1.3%) and four students in Group B (6.7%) had osteochondritis dissecans (OCD) of the elbow, showing that this condition was slightly less common in Group ANo significant difference was noted in the prevalence of shoulder disorders between the two groups. Among the indicators of elbow range of motion, Group A had better elbow extension angles (P = 0.04) and sum of elbow flexion and extension angles (P = 0.006) compared with Group B. In the shoulder joint, the sum of horizontal inner and external rotation angles was better in Group A than in Group B (P = 0.016). No significant difference was noted in the range of motion of the hip joint between the two groups.

Discussion

In this study, OCD of the elbow was slightly less common and the range of motion in the shoulder and elbow joints was better in rubber baseball pitchers than in hardball pitchers, suggesting that rubber baseball can reduce the burden on shoulders and elbows. Excessive pitching needs to be examined in the future by, for example, assessing the number of pitchers.