MRI Detects Shoulder Damage in Young Baseball Pitchers

October 14, 2014

MRI identifies unique shoulder damage, termed acromial apophysiolysis, among young pitchers that could cause long-term problems.

MRI images have detected acromial apophysiolysis, characterized by incomplete fusion and edema at the acromial apophyses, in young patients who may overuse their arms while pitching in baseball games, according to a study published in the journal Radiology.

Researchers from Thomas Jefferson University Hospital in Philadelphia, PA performed a retrospective review of 2,372 patients, aged between 15 and 25, who presented for MR imaging for shoulder pain between 1998 and 2012. The majority of the patients, which included both males and females, were baseball pitchers.

The researchers looked for edema at the acromial apophyses, and no other abnormalities. The association of acromial edema with incomplete fusion, pitching, and clinical findings was determined in the study group. An age- and sex-matched control group was included in the study. The association with the development of an os acromiale and rotator cuff tears later in life was assessed with follow-up imaging after age 25.

“We kept seeing this injury over and over again in young athletes who come to the hospital at the end of the baseball season with shoulder pain and edema at the acromion on MRI, but no other imaging findings,” Johannes B. Roedl, MD, radiologist in the musculoskeletal division at the hospital said in a release.[[{"type":"media","view_mode":"media_crop","fid":"28459","attributes":{"alt":"Stages of fusion and degrees of edema at the acromial apophyses. Axial proton density fat-saturated fast spin-echo MR images","class":"media-image media-image-right","id":"media_crop_9513813993866","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"2888","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 321px; width: 300px; border-width: 0px; border-style: solid; margin: 1px; float: right;","title":"Stages of fusion and degrees of edema at the acromial apophyses. Axial proton density fat-saturated fast spin-echo MR images (repetitition time msec/echo time msec, 2000–3000/25–30) of the acromioclavicular joint. (a) Nonfusion (stage 0) and pseudoarthrosis (solid arrow) between the metaacromion and the mesoacromion with mild acromial edema (involving  25% of the acromion, dashed arrows) in an 18-year-old male patient. (b) Fusion of 25% or less of the physis (stage I, solid arrow) with moderate edema (involving . 25% and  75% of the acromion, dashed arrows) in a 15-year-old female patient. (c) Fusion of more than 25% and 75% or less (stage II, solid arrow) and severe edema (involving . 75% of the acromion, dashed arrows) in a 20-year-old male patient. (d) Complete fusion (stage III, . 75% fusion, arrow) and no edema in a 23-year-old male patient. Image provided courtesy of Radiology. © RSNA, 2014.","typeof":"foaf:Image"}}]]

The results showed that edema at the acromial apophyses was found in 61 subjects (2.6%) and was associated with incomplete fusion of the acromial apophyses and superior shoulder tenderness. The entity was named acromial apophysiolysis.

All 61 subjects stopped pitching for three months; 60 were treated conservatively with nonsteroidal analgesics and one underwent surgery. Twenty-one of the 29 patients with the overuse injury continued pitching after the rest period, and all 21 showed incomplete bone fusion at the acromion.

The researchers noted that a pitch count of more than 100 pitches per week was a risk factor for acromial apophysiolysis. Follow-up MRI or X-ray imaging studies conducted a minimum of two years after the subjects turned 25 were available for 29 of the 61 injured subjects and for 23 of the 61 controls. Follow-up imaging revealed that 25 of the 29 injured subjects (86%) with the overuse injury showed incomplete fusion of the acromion, compared to only 1 of the 23 (4%) controls. Rotator cuff tears were also more common among those who continued to pitch after the rest period (68%), compared with the control group (29%). Severity of the tears was also worse among the pitching group.

“This overuse injury can lead to potentially long-term, irreversible consequences including rotator cuff tears later in life,” Roedl said.

The researchers concluded that these injuries predispose patients to further shoulder injury as adults, and that pitching should be limited to no more than 100 throws per week for teenage and young adult pitchers.