Relationship between Throwing Side and Laterality of Lumbar Spondylolysis in Baseball Players

Abstract

Introduction: There are many reports on lumbar spondylolysis in adolescent baseball players, and a study has reported that 16.4% of college baseball players have spondylolysis. In addition, this study has reported that 44.1% of professional baseball players are affected with lumbar spondylolysis. In other words, spondylolysis is a common condition among baseball players. The occurrence of lumbar spondylolysis is thought to be related to stress concentration at the pars interarticularis due to lumbar extension and rotation. Especially during rotation, this stress is applied to the pars interarticularis opposite to the rotation direction. For this reason, it is thought that lumbar spondylolysis is often seen in unilateral cases in disciplines in which rotation in only one direction is repeated. In the present study, baseball players accounted for 35.2% of athletes diagnosed with lumbar spondylolysis at our hospital, and the majority of patients comprised those who were sportspersons. Also, in this report, bilateral cases accounted for 53.6% and unilateral cases accounted for 46.4% of athletes diagnosed with lumbar spondylolysis. The purpose of this study was to compare and evaluate the correlation between the laterality of spondylolysis and the throwing side or batting side, which are asymmetry behaviors in baseball players.

Methods: We investigated throwing side, batting side, and the laterality of spondylolysis for 93 lesions in 64 vertebrae of 57 players who belonged to a baseball club and were diagnosed with lumbar spondylolysis. In addition, we examined the fielding position ratio compared with that reported in a nationwide survey. Binomial test or Fisher exact test was used to determine a significant difference, i.e., p < 0.05.

Results: Statistics were obtained on the relationship with the laterality of spondylolysis during asymmetric movements in baseball players, and it was found that spondylolysis occurred on the side opposite to the throwing, but not batting, side. Furthermore, the occurrence of spondylolysis was significant in pitchers.

Conclusions: In this study, it was shown that lumbar spondylolysis in baseball players is strongly related to throwing and is likely to develop on the side opposite to the throwing side, especially in pitchers. In addition to throwing, fielders are involved in multiple actions such as batting and fielding.