History

A thorough history is necessary to determine the best treatment options for a patient with suspected RI pathology. An isolated RI lesion is probably quite rare, and RI pathology is usually seen with concomitant instability conditions of the shoulder, including anterior, posterior, and multidirectional. Thus, in a patient with shoulder instability, it is imperative to evaluate the RI for possible deficiency. As suggested by Ho et al,¹⁵ injuries to the RI usually occur as part of a spectrum of glenohumeral pathology as opposed to a separate, isolated lesion. Surrounding structures including the labrum, coracohumeral ligament, biceps tendon, and rotator cuff are often injured along with an RI lesion; thus, presenting symptoms may be consistent with the same symptoms reported with injuries to any of these structures. The diagnosis of any additional pathology in addition to lesions to the RI is thus crucial for preoperative planning and appropriate surgical management.

Physical examination

Isolated pathology of the RI is difficult to assess on physical exam because examination findings may be vague and representative of other shoulder lesions, including anterior, posterior, and/or multidirectional instability. It is thus imperative to perform a complete examination of the shoulder, paying particular attention to signs for instability and glenohumeral pathology, including rotator cuff tears, impingement, and biceps pathology. Critical assessment of the shoulder will enable the surgeon to make appropriate decisions regarding potential operative care and will help determine if the patient actually has RI pathology or if the symptoms are due to some other cause.

As in any shoulder examination, the structure, function, neurologic status, and strength of the injured shoulder should be compared with the opposite shoulder. Loss of motion should alert the surgeon to pathology other than RI pathology, and if significant stiffness is noted, range of motion must be optimized before any operative stabilization procedure to avoid progressive loss of motion. Asymmetric loss of external rotation at the side (ERS) may indicate overconstraint (if prior surgery has been performed) or contracture of the subscapularis, the rotator interval, or the superior capsule (superior and middle glenohumeral ligaments), whereas asymmetric loss of external rotation in abduction (ABER) may identify nonanatomic overconstraint of the inferior ligaments. Strength in all planes also should be assessed, and weakness should indicate the possible presence of concomitant pathology such as rotator cuff tear or suprascapular nerve palsy. Because subscapularis rupture can occur following traumatic shoulder instability, it should be recognized preoperatively via the belly-press test and lift-off maneuver. Shoulder stability testing also should be addressed, with focus on the various glenohumeral ligaments because the type of laxity might change the surgical plan.

During examination, if downward traction of the arm causes inferior subluxation of the humeral head that does not resolve with external rotation of the shoulder, also known as the sulcus sign, a lesion of the RI should be suspected.¹¹ When the RI is intact, external rotation with the arm at the side will allow for resolution of the sulcus sign as the CHL becomes taught (Fig. 35-3).¹¹ In patients who have hyperlaxity, careful attention of the sulcus evaluation should be performed to assess for an incompetent RI. In addition, as demonstrated by Gagey et al¹⁶ if the arm is able to be abducted beyond 105 degrees when the scapula is stabilized as the shoulder is maximally passively abducted, the patient is said to have hyperlaxity of the inferior glenohumeral ligament (IGHL); however, it is not known if this is due to an inferior capsule that is enlarged or incompetent RI (Fig. 35-4).

FIGURE 35-3 Schematic of physical examination of the shoulder: the patient is sitting with the arm at the side and externally rotated, as the examiner puts downward force on the arm and assesses the sulcus.

FIGURE 35-4 The Gagey test is demonstrated with the patient sitting and the arm passively abducted to maximal position while the scapula is stabilized. A positive test occurs when the arm can be abducted beyond 105 degrees.

Radiographic findings

Various imaging modalities can be helpful in the diagnosis of RI pathology, including radiographic studies, computed tomography (CT) studies, and magnetic resonance image (MRI) and arthrogram studies. Radiographic studies, including the anteroposterior, scapular-Y, and axillary views should be performed preoperatively to assess the shoulder joint as a whole, particularly if there are concerns regarding glenohumeral joint space narrowing. Associated bony deformities, such as a Hill-Sachs lesion or glenoid bone loss, can be assessed with a Stryker notch radiograph and a West Point view radiograph, respectively. CT scanning is also extremely helpful in identifying any associated bone loss, in particular when used with software that allows for 3-dimensional visualization of surface lesions. MRI studies are typically used to evaluate soft-tissue structures surrounding the glenohumeral joint, including the labrum and capsular complex, and have been used to identify both the anatomy and pathology associated with the RI.^17,18 Magnetic resonance arthrogram (MRA) is the most sensitive of all imaging studies. Typical signs of RI injury include radiopaque dye in the subacromial and/or subdeltoid bursa through the RI,¹⁹ as well as radiopaque dye under the coracoid on the oblique sagittal images.^20,21 Improper MRA technique can result in dye being injected into the soft tissues as opposed to intra-articularly, producing a false-positive result.^22,23

Relevant anatomy

The RI is a triangular-shaped space of the anterior shoulder, bordered superiorly by the anterior margin of the SS tendon, inferiorly by the superior margin of the SSc tendon, medially by the base of the coracoid process, and laterally by the sulcus for the long head of the biceps (LHB) tendon and the transverse humeral ligament.^2,11 Complicating the anatomy is the amount of structures contained within the relatively small space of the RI, including the CHL, the superior and middle glenohumeral ligaments (SGHL and MGHL), the LHB tendon, and a thin layer of capsule.^1–3 The CHL is a fibrous structure that originates at the base of the coracoid and splits laterally into two bands. One band of the CHL inserts on the anterior edge of the SS tendon and greater tuberosity, while the other inserts on the SSc, the transverse humeral ligament, and the lesser tuberosity. The SGHL is relatively smaller than the CHL, originating from the glenoid labrum adjacent to the supraglenoid tubercle, crossing the floor of the RI deep to the CHL, and inserting on the fovea capitis on the lesser tuberosity.^2,18 The LHB tendon is located between the CHL and the SGHL.

The overall function of these various structures within the RI, and thus the overall role of the RI in preserving glenohumeral stability, is unclear. The SGHL has been shown to prevent inferior translation of the abducted shoulder, while the CHL has been demonstrated to be an important stabilizer against inferior glenohumeral translation in the adducted arm. The RI capsule, while only 0.06 to 0.1 mm thick,²⁴ is nevertheless vital in maintaining the negative intra-articular pressure and concavity-compression of the glenohumeral joint, and lesions may compromise overall shoulder stability (Table 35-1).

Table 35-1 Summary of RI Anatomy and Function