2015 ISAKOS Biennial Congress ePoster #2601
Difference in the Range of Motion Between Dominant and Nondominant Sides of Hip Internal Rotation of Baseball Pitchers in Growth Period
Yoshihiro Kotoura, MD, PhD, Kyoto, Kyoto JAPAN
Toru Morihara, Kyoto, Kyoto JAPAN
Yoshikazu Kida, MD, PhD, Kyoto JAPAN
Toshikazu Kubo, MD, PhD, Kyoto, Kyoto JAPAN
Kyoto Prefectural University of Medicine, Kyoto, Kyoto, JAPAN
FDA Status Not Applicable
Summary: The physical characteristics of teenage baseball pitchers
Several reports have shown that the restriction of hip internal rotation (HIR) may cause throwing injuries in shoulder and elbow. But the symmetrical properties of HIR in young throwing athletes have not been clarified. The purpose of this study was to investigate the range of motion (ROM) of HIR in baseball pitchers in growth period.
233 young baseball pitchers were classified into middle school group (n=93, 13.9±0.6 y.o., started to play baseball since 8.5±1.9 y.o.) and high school group (n=140, 16.7±0.5 y.o., started to play baseball since 8.8±2.2 y.o.). Passive ROM of dominant (D) and nondominant (ND) HIR were measured. Significance was set at P < 0.01 for Paired t-test.
ROM of HIR of nondominant side was significantly wider than HIR of dominant side both among middle school pitchers (D=42.4±13.5°, ND=46.6 ± 13.2° ) and among high school pitchers( D=35.4±12°, ND=38.1±12.6°). Middle school pitchers had significantly larger HIR than high school pitchers irrespective of dominant or nondominant side.
Many reports have pointed to ROM of HIR decreasing gradually with age. The results of this study were similar to them. Several studies have shown that the mean femoral anteversion angle is 30-40° at birth and diminishing throughout childhood and adolescence to a mean value of 10-15° at maturity. This is one of the reasons, why ROM of HIR decreases gradually with age. HIR of the nondominant side was significantly wider than the dominant side. Kinetic force of internal rotation and adduction occurs in the nondominant hip joint during cocking and following through, because pitching is an asymmetric motion. We think that is one of the causes of a lateral difference of ROM of HIR.
Wider ROM of HIR in nondominant side than that in dominant side is one of the characteristics of baseball pitchers in growth period.