Take Home Points
Batter’s shoulder causes posterior instability leading to episodic subluxation of the lead shoulder during the baseball swing (Wanich 2012). A subluxation is defined as an incomplete dislocation. Posterior shoulder instability is typically the result of a posteriorly directed load to the shoulder in a position of forward flexion, adduction, and internal rotation (Wanich 2012). Posterior instability affects only 2% to 12% of patients with shoulder instability. There has been recent research in posterior shoulder instability as a cause of disability in the athletic population. Posterior instability in the athletes is usual caused from contact sports and this occurs from acute trauma or repetitive microtrauma. In the case of batter’s shoulder, the major rotational forces about the shoulder are believed to be the cause of the instability (Wanich 2012). The symptoms from posterior shoulder pain occur during batting and this causes the inability to generate power during the baseball swing. It is unknown impossible to pinpoint the exact mechanism of injury in batter’s shoulder; the problem is thought to be the result of repetitive microtrauma. This repetitive microtrauma could be cause by a swing and a miss on an outside pitch. During a missed pitch, it is presumed there is no counterforce to the momentum from the baseball swing leading to overdynamics in the shoulder and an excessive pulling force (Wanich 2012). Some studies have found an average shoulder abduction angle of 105° for outside pitches versus 90° for inside pitches. The American Sports Medicine Institute (ASMI) group suggested the increased shoulder abduction angle may increase shear forces across the joint (Fleisig 2009).
Wanich (2012) studied the rate of return to play after operative treatment for batter’s shoulder and whether ROM was restored. There were 14 baseball players that were chosen who were diagnosed with batter’s shoulder. Four played professionally, six were in college, and four were in varsity high school. The average age was 20.3 years. All had physical examinations and MRI findings consistent with posterior labral tears involving the lead shoulder. Treatment involved arthroscopic posterior labral repair (n = 10), débridement (n = 2), or rehabilitation (n = 2). Posterior labral tears were classified based on arthroscopic findings according to the classification in which a Type I lesion demonstrates incomplete stripping, Type II a marginal crack, Type III chondrolabral erosion, and Type IV a flap tear. The minimum follow up was 18 months. Eleven of 12 surgically treated patients returned to their previous level of batting at an average of 5.9 months after surgery. The one patient who was unable to return to play also had an osteochondral lesion of the glenoid identified at surgery. Players typically returned to hitting off a tee at 3 months and to facing live pitching at 6 months postoperatively. All patients regained full internal and external ROM as compared with preoperative data. Batter’s shoulder is an uncommon form of posterior instability in hitters affecting their lead shoulder. Most athletes are able to return to play at the same level after arthroscopic treatment of posterior capsulolabral lesions.
Posterior shoulder instability is an uncommon but disabling condition needing more research. Research has looked toward one-handed follow-through during the baseball swing, which could increase the microtrauma across the posterior labrum and capsule. Athletes with posterior shoulder subluxation should undergo a trial of nonoperative care prior to surgery. An exercise program that develops a pain-free range of motion, a normal scapulohumeral rhythm, and strengthening of the dynamic shoulder stabilizers.
At COR Physical Therapy, we take an individualized approach by first removing the cause of pain, then analyzing the batter’s biomechanics for Batter’s Shoulder Rehabilitation. This analysis provides detailed information of which muscles require strengthening and which require better control. Remember, biomechanical assessment is necessary for sports rehabilitation, as the issue will return if the biomechanics (likely the cause) is improved!
- Fleisig GS, Dun S, Kingsley D. Biomechanics of the shoulder during sports. In: Wilk KE, Reinold MM, Andrews JR, editors. The Athlete’s Shoulder. Philadelphia, PA, USA: Churchill Livingstone; 2009. p. 380.
- Wanich T, Dines J, Dines D, Gambardella RA, Yocum LA. ‘Batter’s shoulder’: can athletes return to play at the same level after operative treatment? Clin Orthop Relat Res. 2012 Jun;470(6):1565-70.
Written by Coach Chris