Fig. 6.1
(a) The empty-can position for testing. (b) The scapular retraction position for testing. The arm is in the empty-can position. The scapula is lightly held in retraction by forearm pressure on the medial scapular border, while the patient exerts maximum resistance against the handheld dynamometer (Reprint from Kibler WB, Sciascia A, Dome D. Evaluation of apparent and absolute supraspinatus strength in patients with shoulder injury using the scapular retraction test. Am J Sports Med. 2006;34(10):1643–7, with permission from SAGE)
Hypertwist
Throwers achieve extraordinary degrees of external rotation due to increased retroversion and anterior capsular laxity and “pseudolaxity” of the anterior capsule due to GIRD [5, 6]. This supraphysiologic humeral rotation creates inordinate shear stress in the rotator cuff, which may manifest as interlaminar rotator cuff tearing. The superior and inferior laminae of the supraspinatus and infraspinatus may separate and form the partial articular tears with intratendinous extension (PAINT lesion) as described by Conway [82]. This shear stress can be exacerbated by a malfunctioning scapula. For example, if the scapula does not posterior tilt during maximum external rotation, the rotator cuff will experience additional twisting, thereby increasing the likelihood of a PAINT lesion.
Internal Impingement
Excessive scapular protraction and anterior tilting lessens the distance between the glenoid and greater tuberosity during the late cocking phase of throwing. Loss of scapular retraction also causes the thrower to increase horizontal abduction, thus throwing out of the scapular plane with resultant-increased contact between the posterior-superior labrum and greater tuberosity. “Pinching” of the supraspinatus may result with subsequent damage to cuff tendon fibers. This internal impingement [83] manifests with undersurface tearing of the supraspinatus/infraspinatus junction (Fig. 6.2). In time, this labral “pinching” may lead to posterior-superior labral fraying (Fig. 6.3). Scapular protraction and GIRD are inextricably linked. Loss of internal rotation will lead to scapula windup, as described by Kibler et al. [84], whereupon the scapula migrates into protraction in order to provide internal rotation. If a thrower is restrained from following through due to a tight posterior capsule, the scapula will migrate “up and around” the thorax in order to allow the arm to be directed toward home plate. Weakness of both static and dynamic restraints will eventuate in a scapula that rests in an internally rotated (protracted) position. In addition, posterior capsular contracture causes a relative posterior-superior shift of the humeral head in late cocking, further increasing “peel-back” stresses to the posterior-superior labrum and potentiating the creation of a type two labral injury [85]. The “relocation test” will be positive in this scenario as posterior pressure applied to the upper humerus will lessen tuberosity/glenoid contact with the scapula manually placed in an optimal position.
Fig. 6.2
Arthroscopic demonstration of undersurface rotator cuff tearing at the supraspinatus/infraspinatus junction
Fig. 6.3
Arthroscopic demonstration of posterior-superior labral fraying (arrow) with concurrent posterior-superior undersurface rotator cuff tearing (asterisk)
External Impingement
A protracted scapula diminishes space between the humeral head and acromion. As the scapula protracts and follows the contour of the ribs, it tilts forward and increases acromial—great tuberosity contact in forward flexion [54]. A painful abduction arc that is relieved with scapula assistance (scapula assistance test) may confirm the presence of a symptomatic functional impingement. In fact, Muraki et al. [86] showed that the presence of a tight posterior-inferior capsule increases humeral head-coracoacromial contact pressure during the follow-through phase of throwing.
Scapula and the Elbow
The incidence of elbow injuries in pitchers has skyrocketed [87]. Surely increased pitch counts share the blame for this epidemic. However, the scapula plays a major role in the etiology of elbow injuries, especially the failure of the ulnar collateral ligament (UCL). There have been established relationships of GIRD [88] and total range of motion deficits [88–90] and UCL injuries. A loss of internal rotation (GIRD) essentially diminishes long-axis rotation of the upper arm. Proximal segment impairment will predictably transfer increased load distally (elbow) in order to achieve the internal rotation necessary to propel a baseball to home plate. In fact, Suzuki et al. [91] have shown that scapula fatigue leads to compensatory motions at the elbow. The loss of humeral external rotation seen in throwers suffering from UCL injury may serve as a protective mechanism [89] by which the thrower avoids the inordinate valgus elbow torque realized with extreme humeral external rotation. A protracted scapula potentiates throwing “out of the scapular plane”, i.e., in relative humeral horizontal abduction. This increases the duration of valgus loads application to the elbow during throwing. The longer the upper arm is behind the thorax, the more the elbow will realize a valgus moment. Secondly, a “dropped elbow” seen during some deliveries increases the distance from the center of the body’s rotational axis to the end of the moment arm (the hand). This increase in moment arm length merely increases the amount of centripetal force applied to the elbow. Reasons for lowering the elbow during pitching are many and include core weakness, posterior capsular tightness, scapular protraction, and cuff weakness.
Examination
Rotator Cuff
As stated, the throwing shoulder experiences cuff injury in three chief locations: leading edge of supraspinatus, due to eccentric load failure, interlaminar tears of the supraspinatus and infraspinatus due to hypertwist, and the junction of the supraspinatus and infraspinatus due to internal impingement. An effective examination should delineate a fairly precise zone of injury.
Supraspinatus
The “Whipple test” (Fig. 6.4) as described by Savoie et al. [92] detects weakness of the leading edge of the supraspinatus. The test is performed by asking the patient to forward flex and place the arm in extreme adduction. Pain and/or weakness during resistance of forward flexion constitute a positive result. While both the “full can” and “empty can” appear to equally load the supraspinatus proper, the “full can” may serve as a superior test to measure entire supraspinatus integrity since it is generally associated with less pain provocation [93]. Thus, weakness demonstrated with a positive Whipple test in the face of a normal “full can” test suggests a partial-thickness anterior supraspinatus lesion. Weakness during the Whipple test is truly positive when the scapula is held in retraction (scapular retraction test) since a protracted scapula (unstable base) will compromise supraspinatus function [75].
Fig. 6.4
The Whipple test is performed by positioning the patient’s shoulder in 90° of shoulder forward flexion with maximal horizontal adduction. The examiner then applies an inferior-directed force at the distal forearm, while the patient maintains the position. A positive test is weakness or pain
Internal Impingement
Compression of the supraspinatus between the posterior-superior glenoid and greater tuberosity occurs in the late cocking or ABER position. The relocation test (Fig. 6.5) is superb for detection of this phenomenon. In the ABER position, posterior pain that is relieved with a posterior force applied to the proximal humerus is considered a positive sign for internal impingement, i.e., a positive relocation maneuver. As stated previously, posterior force applied to the humerus lessens the impingement by increasing the tuberosity glenoid distance.
Fig. 6.5
The relocation test is performed by positioning the patient supine on the examine table with the shoulder in 90° of abduction and 90° of external rotation. In this position the examiner applies a posterior force to the anterior proximal humerus, thereby alleviating potential internal impingement symptoms
Labral Tear
Although numerous examination tests to detect labral injury have demonstrated inconsistent results [94], the dynamic labral shear (DLS) test has been shown by Kibler et al. [95] to demonstrate excellent sensitivity, specificity, and accuracy. During this maneuver, the abducted arm is brought into extreme external rotation and horizontal abduction. The arm is then forcibly lowered and thereby “shearing” the posterior cuff against the posterior-superior labrum (Fig. 6.6). Kibler et al. [95] have also shown that although the O’Brien’s test, whereby the forward flexed, adducted, and internally rotated arm resists downward pressure, was less sensitive than the DLS in labral tear detection, the combination of both tests demonstrated the most consistent prediction of arthroscopic findings of labral injury.
Fig. 6.6
(a) Dynamic labral shear (DLS) test. With the patient in a standing position, the involved arm is flexed 90° at the elbow, abducted in the scapular plane to above 120°, and externally rotated to tightness. It is then guided into maximal horizontal abduction. (b) The examiner applies a shear load to the joint by maintaining external rotation and horizontal abduction and lowering the arm from 120° to 60° of abduction. A positive test is indicated by reproduction of the pain and/or a painful click or catch in the joint line along the posterior joint line between 120° and 90° of abduction (Reprint from Ben Kibler W, Sciascia AD, Hester P, Dome D, Jacobs C. Clinical utility of traditional and new tests in the diagnosis of biceps tendon injuries and superior labrum anterior and posterior lesions in the shoulder. Am J Sports Med. 2009;37(9):1840–7, with permission from SAGE)
Imaging Findings in Thrower’s Shoulder
Advanced imaging modalities, especially MRI scans, can greatly aid in diagnosis of scapula-related cuff and labral injury. MRI arthrograms, whereupon dye is injected into the shoulder capsule, have enhanced the yield of detecting cuff and labral injury [96] (Fig. 6.7). However, it must be noted that the highly sensitive new-generation MRI scanners may detect many “inconsequential” labral tears [97]. In fact, some labral stretching may be adaptive and allow the thrower to obtain the “slot.” Thus, all imaging findings must support the exam findings. For rotator cuff undersurface tearing, the MRI ABER view, whereupon axial images are obtained in ABER, has been shown to increase sensitivity in detection of partial articular-side damage [98]. Furthermore, the ABER view has been found to increase detection of both internal impingement and glenoid labrum tears [99, 100] (Fig. 6.8). Subtle undersurface tearing of the infraspinatus, as seen in internal impingement, may present with a small cystic change on the posterior humeral head in the vicinity of the supraspinatus/infraspinatus junction (Fig. 6.9).
Fig. 6.7
MRI arthrogram indicating enhanced visibility of a cord like MGHL (asterisk) and Buford complex—anatomic variant mimicking labral tear (arrow)
Fig. 6.8
MRI arthrogram in the ABER position. The posterior-superior glenoid, rotator cuff, and labrum are easily identified (asterisk)
Fig. 6.9
MRI indicating cystic changes on the insertion site of the supraspinatus (arrow) due to chronic internal impingement
Treatment
Key Principles of Rehabilitation
Scapula-related throwing injuries are chiefly treated conservatively with restoration of “shoulder homeostasis” being the goal. A principle goal should be restoration of symptomatic scapular malposition. Tate et al. [101] have discovered that not all scapular asymmetry is accompanied by symptoms. In fact, relief of cuff or labral-related pain with scapula reposition (retraction or scapular assistance test) indicates a consequential scapular position issue. Repositioning of the scapula is realized through strengthening the scapular retractor muscles and stretching tightened structures which potentiate protraction. Many athletes who engage in weight training pay nearly undivided attention to protraction-lending exercises (bench press) while neglecting important scapular retraction exercises such as scapular pinches, close-grip rows, and prone horizontal abduction with external rotation [102], which are necessary for shoulder homeostasis. The “low row” is ideal for selectively activating serratus anterior and rhomboids. Blackburn exercises [103] are superb at training retractors as well. “Lawn mower” pulls, as popularized by Kibler et al. [104], introduce more core activation, while concomitantly training scapular retraction. Comprehensive kinetic chain evaluation is paramount in returning the thrower to full activity. Subtle findings in the overhead athlete may include a weakness in stance leg abduction, lead leg loss of hip internal rotation, lead leg quad tightness, and loss of stance leg ankle dorsiflexion. Posterior capsule and cuff tightness must be addressed with sleeper stretches and cross-body adduction stretches in order to prevent the recurrence of scapular “windup” [84].
Indications for Surgery
Failure of at least 3 months of quality and “enlightened” physical therapy with positive examination findings of a consequential labral tear warrants arthroscopic evaluation. In addition, the presence of overt mechanical symptoms such as locking, catching, and persistent “dead-arm” sensation is also an indication for arthroscopic intervention. As stated, one must be mindful that not all labral separations are pathologic and that some labral stretching may, in fact, be adaptive.
Surgical Pearls
The lateral decubitus position affords excellent exposure to all aspects of the shoulder, especially the posterior and inferior recesses, and is strongly preferred by the senior author. A standard posterior viewing portal approximately 2 cm medial and 2 cm distal to the corner of the acromion is established first. Two anterior portals, one at the anterolateral corner of the acromion (AL portal) and another 2 cm lateral to the tip of the coracoid (standard anterior portal—AP), are established next. While viewing from the AL portal, a liberating type instrument is used from the AP to free the labrum from the glenoid. Attritional labral stretching does not warrant repair. Complete labral separation with concomitant fissuring of glenoid and/or labral surface usually indicates a consequential labral injury. A dynamic “peel-back” test whereupon the arm is removed from traction and placed into ABER will reveal not only frank labral separation but also increased posterior-superior humeral translation and contact with supraspinatus fibers (internal impingement).
Signs of cuff failure, whether fraying of the supra/infra junction as seen in internal impingement or undersurface supraspinatus fiber disruption due to eccentric load-induced cuff failure, further confirm that the labral injury may have engendered adverse consequences. With the AL viewing, portal percutaneous anchor insertion is accomplished via the “Port of Wilmington” [78]. Sutures are shuttled via a Neviaser portal, and great care is taken to capture labral tissue only. Over constraint, especially of any posterior capsular tissue, can be disastrous to a thrower. The senior author favors less compliant suture material as the superior labrum has inherent flexibility. Some of the newer suture materials available today are extremely stiff and do not afford the labral excursion necessary to negotiate overhead throwing. Secondly, the senior author favors horizontal mattress knotted configuration for two reasons (Fig. 6.10). First, a horizontal suture pattern restores labral height to its native configuration [105]. As Yoo et al. [106] have shown, shoulder function post-instability surgery correlates with labral height. Knotless suture configurations “push” the labrum onto the glenoid and do not roll the labrum onto the articular surface such as seen with knots. Secondly horizontal mattress configurations displace suture material well away from the articular surface. The senior author has witnessed considerable suture abrasion from prominent suture material in several cases (Fig. 6.11). If one chooses a simple suture configuration, then an absorbable suture material, such as PDS, is recommended (Fig. 6.12).
Fig. 6.10
Arthroscopic view of a horizontal mattress suture knot used to secure the labrum (double arrow)
Fig. 6.11
Arthroscopic view demonstrating chondromalacia to humeral head (asterisk) due to suture abrasion from prominent suture material (arrow)
Fig. 6.12
Arthroscopic view demonstrating the use of a simple suture configuration using PDS absorbable suture
Posterior Capsular Release
The senior author only rarely performs posterior capsular release. Indications include true stretch nonresponders, which are encountered only rarely when the help of a shoulder therapist is enlisted [6]. Furthermore, the capsule must be demonstrated to be thicker and more robust. If a thin posterior capsule is encountered, then release is contraindicated. Stretch nonresponders tend to be more mature throwers (late collegiate or professional) who maintain a symptomatic internal rotation deficit of at least 25° or a total arc of motion loss of at least 5°. Angled capsular punches are used, lifting “upward” while cutting in order to avoid axillary nerve injury (Fig. 6.13).
Fig. 6.13
Arthroscopic view of the posterior-inferior shoulder with the (H) humeral head superior and the (L) labrum inferior. Posterior capsule release (double arrow) is confirmed by visibility of the infraspinatus muscle (IF)
Prevention
The large preponderance of throwing-related injuries to both the shoulder and elbow is indeed preventable. A comprehensive kinetic chain evaluation in the adolescent overhead athlete is paramount in sidestepping cuff and labral injury. A chief component of the kinetic chain is the scapula. Scapular asymmetry may initially be a subtle adaptive change to the thrower, but in time the adverse mechanical consequences of scapular malposition will exact its toll resulting in muscle inhibition and sometimes tissue breakdown of the rotator cuff and labrum. Symptomatic scapular asymmetry, if recognized and corrected early, can avert labral and rotator cuff injury in the throwing athlete.
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