Mr Giugale is from the School of Medicine; Dr Jones-Quaidoo, Dr Diduch, and Dr Carson are from Department of Orthopaedic Surgery, University of Virginia, Charlottesville, Va.
The authors have no financial or proprietary interest in the materials presented herein.
Address correspondence to Juan M. Giugale, BA, 611-D Madison Avenue, Charlottesville, VA 22903; e-mail: firstname.lastname@example.org.
Overhead athletes develop anatomical adaptations in response to the tremendous forces and torsions required in their respective sports. In an elite-level throwing athlete, the arc of motion is shifted posteriorly with increased external rotation to generate more potential energy that will be translated into the power and speed of the ensuing throw. Over time, the arm undergoes increased humeral retroversion and tightness of the posterior capsule.1 The contracture of the posterior capsule insinuates a posterosuperior shift of the contact point between the humerus and the glenoid.2 Although this displacement allows for a greater external rotation, it will lead simultaneously to an acquired loss of internal rotation termed glenohumeral internal rotation deficit (GIRD).
There has been an increasing awareness of the relationship between GIRD and shoulder dysfunction in throwing athletes. The diagnosis of a clinically significant GIRD is an internal rotational difference >25° between throwing and nonthrowing arms or internal rotational loss that exceeds external rotational gain.3 In a series of 124 elite pitchers with a type II superior labrum anterior-posterior (SLAP) lesion (Figure 1), a common injury in this subpopulation, all had severe GIRD with an average preoperative internal rotation deficit of 53°.4
Figure 1. Illustrations Depicting the 4 Types of SLAP Lesions. Type I (A) Has a Frayed or Degenerative Labrum with the Labrum and Biceps Tendon Remaining Attached to the Glenoid. Type II (B) Has Detachment of the Superior Labrum and Biceps Tendon from the Glenoid. Type III (C) Has a Bucket-Handle Tear of the Labrum with an Intact Biceps Tendon Anchored to the Glenoid. Type IV (D) Has a Bucket-Handle Tear of the Labrum that Extends into the Biceps Tendon. (Reprinted with Permission from Mileski RA, Snyder SJ. Superior Labral Lesions in the Shoulder: Pathoanatomy and Surgical Management. J Am Acad Orthop Surg. 1998;6:121–131. Copyright ©1998, American Academy of Orthopaedic Surgeons.)
The type II SLAP tear in these athletes has been postulated to be caused by a “peel-back” mechanism. When an arm is abducted and externally rotated during the cocking phase of the overhead throwing motion, the direction of the biceps’ tendon force vector changes, causing torsion at the point of origin to the glenoid rim and superior labrum (Figure 2). Overhead athletes and other patients, who progressively develop an excess external rotation with an accommodating loss of internal rotation, suffer large torsions that “peel back” the labrum off the glenoid.5 After a lesion is initiated, each time the arm is externally rotated, the labrum will endure the torsion and the tear can enlarge. The deteriorating lesion eventually will lead to symptoms of clicking, catching, and deep aching pain in the shoulder.
Figure 2. Illustrations Showing Superior Views of the Biceps-Labrum Complex at Rest (A) and in the Cocking Phase (B) of the Overhead Throwing Motion, Displaying the Peel-Back Mechanism. The Force Vector of the Biceps Tendon Is in an Altered Position Causing Torsion. (Reprinted with Permission from Burkhart SS, Morgan CD. The Peel-Back Mechanism: Its Role in Producing and Extending Posterior Type II SLAP Lesions and Its Effect on SLAP Repair Rehabilitation. Arthroscopy. 1998;14:637–640. Copyright ©1998, Arthroscopy Association of North America.)
In future Pearls of Practice columns, the strategies to measure GIRD and the approaches to improve internal rotation range of motion with the intention of lowering the risk of labrum tears will be discussed.
- Tokish JM, Curtin MS, Kim Y-K, Hawkins RJ, Torry MR. Glenohumeral internal rotation deficit in the asymptomatic professional pitcher and its relationship to humeral retroversion. Journal of Sports Science & Medicine. 2008;7:78–83.
- Burkhart SS, Morgan CD, Kibler WB. The disabled throwing shoulder: Spectrum of pathology, part II: Evaluation and treatment of SLAP lesions in throwers. Arthroscopy. 2003;19:531–539.
- Braun S, Kokmeyer D, Millett PJ. Shoulder injuries in the throwing athlete. J Bone Joint Surg Am. 2009;91:966–978. doi:10.2106/JBJS.H.01341 [CrossRef]
- Morgan CD, Burkhart SS, Palmeri M, Gillespie M. Type II SLAP lesions: Three subtypes and their relationship to superior instability and rotator cuff tears. Arthroscopy. 1998;14:637–640.
- Burkhart SS, Morgan CD. The peel-back mechanism: Its role in producing and extending posterior type II SLAP lesions and its effect on SLAP repair rehabilitation. Arthroscopy. 1998;14:637–640.