Unusual Chest Wall Pain in a Professional Baseball Pitcher: A Case Report

Introduction Chest wall pain in athletes has a broad differential that involves bony and soft tissue structures as well as visceral and referred-pain generators. It is a challenging region to evaluate, given the lack of awareness of injury patterns and infrequent presentation in athletes. Pitching places particularly high amounts of load on the chest wall musculature (1,2). The latissimus dorsi (LD) reaches an estimated 88% to 168% of its maximum voluntary contraction during the pitching motion (3–5). Along with the pectoralis major, the LD is a predominant driver of shoulder internal rotation torque, which is estimated to reach up to 70 Nm (3,6). These high loads may increase the risk of muscle injury. This case describes a tear in the thoracolumbar portion of the LD, a region of the muscle that is rarely involved. Case Report A 30-year-old male right-handed professional baseball player had a sudden onset of right-sided chest wall pain, radiating from under the axilla to his abdomen, while relief pitching during a game. He described an acute onset of pain that began during arm acceleration and continued through the deceleration and follow-through phases of a pitch. The severe pain caused him to exit the game. It was worsened by deep inspiration. There was no associated shortness of breath. On examination 3 d later, there was ecchymosis, which developed after 48 h, over the right anterolateral chest wall and tenderness just anterior to the midaxillary line at the level of L1, just above the iliac crest. There was no palpable defect. There was normal, painless thoracic and lumbar spine motion, apart from painful resisted rotation. The right shoulder exam showed full range of motion; full strength in the supraspinatus, infraspinatus, and subscapularis; and negative Speed’s, O’Brien’s, impingement, and apprehension-relocation testing. Pain was provoked by the throwing motion, shoulder adduction, and shoulder internal rotation. Additional LD-focused testing included “pull downs,” which consisted of shoulder extension, scapular downward rotation, and elbow flexion; “rows,” which consisted of shoulder extension, scapular retraction, and elbow flexion; and modified rows, which added thoracolumbar extension and rotation to replicate deceleration forces placed on the LD during pitching. These tests all provoked mild pain. Differential diagnosis included internal or external oblique injury, rib fracture, intercostal strain, serratus anterior strain, LD strain, thoracolumbar fascial injury, and thoracic radicular pain. Magnetic resonance imaging (MRI) of the chest wall without contrast was notable for partial thickness myofascial tearing of the right inferior LD, 2 cm above the thoracolumbar fascia (at the L2–L3 area) with resultant hematoma formation, as well as low-grade muscular strains of the right external and internal oblique musculature (Fig. 1).Figure 1:: MRI imaging of the injury. Partial thickness myofascial tearing of the right inferior latissimus dorsi, 2 cm above the thoracolumbar fascia (at the L2–L3 area) with resultant hematoma formation.Rehabilitation emphasized sequential goals: pain control and relative rest, followed by posterior chain and core activation, restoration of hip and thoracic spine mobility, thoracolumbar fascia extensibility, and detailed shoulder and forearm strengthening. A throwing program started with light throwing at week two, progressing to mound work by week three, and returning to full pitching by week four. Discussion LD injuries are rare, comprising 0.7% of all Major League Baseball injuries, with all previously reported cases occurring proximally at the tendon or musculotendinous junction (7–10). Given the LD’s large area, it is reasonable to hypothesize that distal injuries, located over the trunk, may have unique etiologies or clinical courses compared with those located more proximally, toward the arm. While there is a paucity of literature on distal LD injuries, in reports on other large muscles, myotendinous junction injuries are felt to be due to high-energy, eccentric contractions, whereas muscle belly injuries often have a different mechanism and are more commonly seen in the setting of contusion or direct trauma (11). In addition, more distal LD injuries may not be visualized on imaging that is limited to the shoulder girdle. Injuries to the LD are primarily seen in professional pitchers as they have significantly higher LD forces than amateur pitchers during the throwing motion (7). The LD is a broad muscle that originates from various structures (Fig. 2). It contributes to adduction, internal rotation, and extension of the shoulder and is highly active during the late cocking phase of the pitch, when the stride foot has landed and the arm is abducted and externally rotating, and during the acceleration phase, when the arm begins to move forward with shoulder internal rotation, horizontal adduction, and elbow extension as the pitcher releases the ball. The LD eccentrically contracts during the late cocking phase to halt further external rotation, then concentrically contracts to internally rotate and propel the arm forward during the acceleration phase (4). It is during this transition from eccentric to concentric contraction that most LD injuries occur, with athletes commonly describing a sudden pulling sensation in the posterior shoulder (7,9,12). While the athlete in this case experienced LD pain at an atypical location, the pain began during the acceleration phase, which is consistent with prior reports and suggests a similar mechanism. The LD is also active to a lesser degree during arm deceleration, which may explain why pain is often felt during this phase as well. Common exam findings include ecchymosis and tenderness of the posterior axillary fold and pain and weakness in shoulder internal rotation, adduction, and extension. Proposed risk factors for LD injury include glenohumeral internal rotation deficit, relative leg and core weakness, and overuse (9). Given that the LD is a primary driver of arm acceleration, it may take more stress to compensate for relative weakness in the kinetic chain, particularly as fatigue builds. Therefore, preventive efforts may focus on kinetic chain conditioning in pitchers. In this athlete, it was felt that the injury was in part due to overuse, as the athlete experienced two acute workload spikes leading up to the injury.Figure 2:: Latissimus dorsi anatomy. The latissimus dorsi originates from the spinous processes of T7–T12, thoracolumbar fascia, lower 3 to 4 ribs, iliac crest, and inferior angle of the scapula. It inserts onto the intertubercular sulcus of the humerus.The unique location of injury in this case raises questions regarding the mechanism and predisposing factors. While the transition from external to internal shoulder rotation may lead to the more common proximal LD injury, perhaps trunk rotation or lateral bending contributed to lower LD injury in this case (13). Additionally, this athlete strained both his internal and external obliques and had MRI findings of disc degeneration and loss of lumbar lordosis. He also underwent an L4–L5 microdiscectomy approximately 2 years earlier. The functionally intimate relationship between the LD, internal/external obliques, and the lumbar spine, through the central thoracolumbar fascia, should be highlighted, as this athlete sustained injuries to three of these structures, indicating a highly biomechanically significant etiologic region that may be the focus of rehabilitation and future studies on co-occurrence. In addition, an MRI of the chest wall may be useful to simultaneously evaluate both the LD and abdominal obliques in a pitcher presenting with chest wall pain. Given the rarity of LD injuries, there is no clear rehabilitation protocol or return to play (RTP) timeline. Erickson et al. (12) report a mean return to competition duration of 170 ± 169 d for professional pitchers with LD or teres major tears who were treated nonoperatively. Faster RTP in this athlete was likely related to the fact that this was a tendon-sparing injury (7,14). Prior studies suggest that rehabilitation strategies for pitcher RTP should include symptom resolution at the affected site, restoration of shoulder strength and range of motion to baseline levels, and an individualized throwing progression that systematically reintroduces mound work with volumes and intensities that replicate game demands (7,9,12,15,16). Conclusions This case highlights a first report of an inferior LD injury that is most likely to occur in athletes undergoing high upper extremity and chest wall forces. It is important for sports medicine providers caring for throwing athletes to consider this injury in the differential diagnosis of lateral chest wall pain, incorporate abdominal oblique muscle and thoracolumbar spine assessment into the workup, and understand steps for successful RTP. The authors declare no conflict of interest and do not have any financial disclosures.