• Shuichi Kaneyama, Minoru Doita, Kotaro Nishida, Takatoshi Shimomura, Koichiro Maeno, Yuichi Tamura, Masahiro Kurosaka, and Kazuo Yonenobu.
• Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
• J Spinal Disord Tech. 2008 Feb 1;21(1):68-71.

Study DesignCase series.ObjectivesTo report rare cases of thoracic myelopathy due to ossification of the yellow ligament (OYL) in relatively young baseball pitchers and show clinical evidence of the role of dynamic mechanical stress on the development of OYL.Summary Of Background DataThe pathogenesis of OYL is still unclear. The majority of cases of OYL occur in middle-aged men whereas younger people are rarely affected. This has lead to the hypothesis that diffuse mechanical stress and degenerative changes correlate with the development of OYL. However, there have been no clinical reports demonstrating the critical role of mechanical stress in the ossification.MethodsTwo young highly active baseball pitchers with thoracic myelopathy due to OYL are presented. Both had no previous systemic disorders or family history of treatment for OYL. Magnetic resonance imaging and computed tomography demonstrated compression of the spinal cord by unilateral left sided OYL at the level of the thoracolumbar junction.ResultsBoth patients were treated with posterior decompression. They recovered full muscle power after operation and resumed pitching training.ConclusionsPatients had no other factors influencing the development of OYL and the lesions were localized at the left side in the thoracolumbar junction, indicating that repeated, localized rotatory mechanical stress caused by the pitching motion probably influenced the development of OYL in these young baseball pitchers.

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