For the last 20 years, injuries resulting in time out of play have been on the rise in Major League Baseball (MLB), and those affecting the back are no exception.1,2 In the first comprehensive report on injuries in MLB players, back injuries resulted in a mean of 1016 disabled list days per season from 1995 to 1999.1 Similarly, core and back injuries were responsible for 359 disabled list designations from 2002 to 2008. This represented 11.7% of all injuries resulting in time out of play during that time span.2 During that time, back injury prevalence ranked 6th highest of all possible body regions (out of 17), and both position players and pitchers were similarly affected (7.8% and 7.4% of all injuries, respectively).2 These injuries often result in a significant time out of play and can have a tremendous impact on player health. A healthy, stable, and well-functioning lumbar spine is a prerequisite for nearly all baseball-related activities, including pitching, throwing, batting, and running. Accordingly, even minor lumbar spine injuries may profoundly influence baseball performance. Despite this, less is currently known about the true epidemiology and impact of back injuries in professional baseball compared to other professional sporting organizations.3
The most common causes of low back pain and injury in elite baseball players include muscle strains, stress fractures (spondylolysis), annular tears, disc herniation, stenosis, transverse process fractures, facetogenic pain, and sacroiliac (SI) joint arthropathy.4-8 These injuries present in a variety of ways with varying symptomatology. Accordingly, a thorough understanding and comprehensive approach to the diagnosis and treatment of these injuries is necessary. The purpose of this article is to discuss the current state of lumbar spine injuries in professional baseball players. Specifically, we will discuss the critical role of the spine in baseball activities, common causes of injury, tips for making the diagnosis, treatment options, outcomes, and injury prevention and rehabilitation strategies.
Role of the Spine in Baseball
The spine and core musculature are responsible for positioning the head, shoulders, and upper extremities in space over the hips and lower extremities. Proper maintenance of this relationship is required during all phases of throwing, pitching, running, and hitting. During these activities, the spine may dynamically flex, extend, rotate, and laterally bend as needed to keep the body balanced with the head centered over the trunk.
Pitching and Throwing
Whether pitching from the wind-up or the stretch, the head begins centered over the hips and pelvis. As the pitching motion progresses, the hips undergo rotation, flexion, extension, abduction, and circumduction. While this is occurring, the shoulders and upper truck must bend, rotate, and translate toward home plate with the body. Just prior to front foot contact, trunk rotation averages 55 ± 6° with a maximal mean angular acceleration of 11,600 ± 3100°/s2. 9 In order for the body to remain balanced, controlled, and synchronized throughout this delivery, the lumbar spine and core musculature must work diligently to stabilize the entire kinetic chain. Of all the trunk muscles (paraspinal, rectus abdominis, obliques, and glutei), the lumbar paraspinal muscles often work the hardest during the pitching motion, demonstrating activity increases ranging from 100% to 400%.10 Accordingly, it is not uncommon for pitchers to develop SI joint or lumbar facet joint pain due to this high degree of torsional strain exerted on the low back.4 Poor lumbopelvic control has been shown to be a predictor of subsequent injury, and the degree of lumbopelvic dysfunction is proportional to injury severity in MLB pitchers.5
Hitting
Similar to pitching, hitting involves a complex combination of movements from the upper and lower extremities that must be balanced by the core and spine. Although numerous movements occur simultaneously, rotational motion is primarily responsible for generating power. The trunk rotates an average of 46 ± 9° during the swing and reaches a maximal angular acceleration of 7200 ± 2800°/s2 just after contact.9 During this period of rapid torsion, the spine must rotate in conjunction with the hips and shoulders to create a stable cylinder and axis of rotation. The spine and core are responsible for synchronizing rotation to ensure that hip and shoulder parallelism is maintained from swing initiation to ball contact. If the body does not rotate as a unit, the position of the head is affected and the batter’s ability to see the ball may be compromised. Additionally, if delivery of the shoulders lags too far behind that of the hips, the position of the hands (and bat) in space is adversely affected. The entire kinetic chain must remain balanced, coordinated, precisely timed, and standardized throughout the entire swing from initial trigger to final follow-through. The lumbar spine plays a critical role in each of these steps. If lumbar spine mechanics are not sound, this can have significant adverse effects on batting performance and may predispose hitters to injury.4