Orthopaedic Surgery/Superior Labral Lesions

THROWING INJURIES & SLAP LESIONS
DAVID V RAJAN & CLEMENT JOSEPH Sports Injury and Arthroscopy Clinic, Coimbatore.

Sports that require overhead arm action (e.g. volleyball, swimming, tennis) and throwing (eg. baseball, cricket, javelin) place significant demands on the shoulder. Approach to the athletic shoulder is quite different from that of normal shoulders. More than 50% of the force of throwing is generated from lower limbs and trunk rotations. The shoulder is the main link in this kinetic chain.1,2 This article discusses the pathomechanisms involved in the problematic overhead shoulder and the prevention and management of superior labral lesions, which put an end to the athletic career.

KINEMATICS

The throwing action is divided into many phases. In the wind-up phase, the player gets ready with build-up of potential energy. During the cocking phase the player takes the arm high and back (abduction and external rotation). At this stage, the anterior capsule is stressed and rotator cuff, especially subscapularis is very active. The acceleration phase is from the cock-up position to the ball release. Though significant forces are generated in this phase, the shoulder is minimally stressed. The most violent phase is the deceleration phase, which is the arm follow-through, after the ball release. The arm is slowed down by the eccentric contraction (contraction while lengthening) of cuff muscles. During this phase the posterior capsule is stressed to maximum and is responsible for the reactive hypertrophy of the capsule resulting in contracture and loss of internal rotation. 3

PATHOMECHANISM

Two schools of thought exist regarding the basic pathomechanism of the disabled shoulder. The first one regards the stretched out anterior capsule as the primary pathology.4 The second one regards the acquired posterior capsular contracture resulting in a glenohumeral internal rotation deficit (GIRD) as the primary pathology. The latter is gaining widespread acceptance currently.3,5

Posterior Capsule tightness Significant internal rotation loss occurs in dominant shoulders when the players are not doing proper stretching exercises. With the rotations of humeral head, the capsule and glenohumeral ligaments also move accordingly. During external rotation, the tight band of posteroinferior capsule comes to lie inferior to the humeral head and pushes the glenohumeral rotation point posteriorly and superiorly(fig2). This altered resting position clears the greater tuberosity off the posterosuperior glenoid and allows excessive external rotation. Because of the excessive external rotation, the long head of biceps starts to pull on the superior labrum from a posterior direction. This altered force vector of the biceps results in avulsion of superior labrum resulting in SLAP lesions.3,5,6

ROTATOR CUFF PATHOLOGY

As we have already seen, the stress during eccentric contraction of rotator cuff can lead to fiber failure.3 In addition, the excessive external rotation of humeral head causes twisting of the cuff fibers causing an additional torsional overload.3 In extreme external rotation the articular side of posterosuperior cuff can impinge against the posterosuperior glenoid resulting in fraying and partial tears (Internal impingement).7,8 All these mechanisms are involved in rotator cuff pathology and in athletic shoulders most of the rotator cuff problems lie on the articular side of the cuff, hence subacromian injections and acromioplasty rarely help.

BICEPS TENDON Lesions of the long head of biceps could be minor fraying, partial or complete tears and subluxations. Subluxation is demonstrated by abducting and external rotating the arm while simultaneously palpating the tendon.

SCAPULA

The scapula and associated muscles provide the platform for the shoulder function. A drooped and protracted shoulder (tennis shoulder) is commonly seen in overhead athletes, which is due to fatigue of scapular muscles and heaviness of the hypertrophied playing arm. The malpositioned scapula can lead to impingement pain (altered acromion position, reducing the subacromial space) coracoid pain (traction tendinitis of pectoralis minor).5 The scapula rhythm is observed as the athlete elevates both the arms. Winging or prominence of medial border also indicate scapular muscle imbalance The management consists of rehabilitation by strengthening, flexibility and plyometric exercises.1,2

NEUROLOGICAL PROBLEMS

Mononeuropathies involving suprascapular nerve and nerve to latissimus dorsi are commonly seen. The suprascapular nerve can sustain injuries due to traction due to overhead activity or compression by a paralabral cyst arising from a labral tear. If the suprascapular nerve is compressed at suprascapular notch, both supraspinatus and infraspinatus will be affected and if compressed at spinoglenoid notch only infraspinatus is affected. Clinical diagnosis is by observation of wasting and weakness on isolated muscle strength testing.9

INSTABILITY Recurrent dislocations in the dominant shoulder preclude overhead athletic activity. Many an athlete have shoulders which are lax, but stable. Laxity (sign) should not be confused with instability (symptom). SLAP lesions can themselves create a pseudolaxity, which disappears after SLAP repair. Rarely a SLAP lesion occurs continous with a Bankart lesion. Gross anterior capsular laxity producing excessive external rotation (>130 degrees) may need capsular plication.5 Any demonstrable anterior instability in a throwing athlete occurs as a tertiary phenomenon due to a tight posterior capsule and SLAP lesion.3

Table. EVALUATION OF ATHLETE SHOULDER - Outline History	Involvement of shoulder in the particular sport, Training details, Overtraining? faulty techniques ? Expectations & Goals? Pain – aggravating & relieving factors, Instability – degree ? direction? frequency? GENERAL	Posture, pelvic stability, spine- ROM, scoliosis & kyphosis, Hyperlaxity & Cervical spine examination – IVDP? Scapula	Drooping, winging ,dysrhythmia, wasting Inspection	Wasting, AC joint, Palpation	Tenderness- biceps groove, GT, AC joint, Posterosuperior aspect & coracoid Range of movements	Active & Passive, Compare, Painful range?Rotations- supine, arm at side (ER-S) and arm abducted to 900 (ER-A & IR-A) Strength testing	Isolated strength testing of supraspinatus, infraspinatus, subscapularis & deltoid Biceps	Fergusson’s & Speed tests, subluxation in AB-ER position Rotator cuff	Partial or Complete? Neer’s impingement sign, Hawkins-Neer’s test, Drop arm test Instability	Anterior – Load & Shift test, Jobe’s relocation testPosterior – Jerk test, Push pull test, MDI – Sulcus SLAP lesions	Clicks? O’Brien’s test, Jobe’s test, Kim’s biceps load test Others	Local injections – Subacromial space, biceps groove and AC jointAdson’s test, pulses - Thoracic Outlet syndromeNCS, EMG – neuropathies, MRI – Rotator cuff, labral tears and paralabral cysts
 * Painful tests can be performed at the end of examination*Painful provocative tests are highly positive if examined immediately after a game or exercise. Hence the athlete should be examined after a period of rest.

SLAP LESIONS The labrum serves as an attachment point for capsule, glenohumeral ligaments and long head of biceps. It acts as a bumper and deepens the glenoid. The long head of biceps inserts into the supraglenoid tubercle as well as superior labrum. This biceps – superior labral complex is disturbed in sports as well as other injuries. These lesions were first described by Andrews10 and later classified by Snyder, who gave the acronym SLAP (Superior Labrum Anterior Posterior)11. The superior labrum- biceps complex exhibits normal anatomic variations that should be distinguished from tears. (Fig 3)

Classification Superior labral lesions are classified into four major subtypes (Fig 4) and few other less common patterns also have been recognized.

Type I - fraying of the superior labrum Type II - avulsion of the superior labrum off the glenoid. Type III - buckethandle tear of the superior labrum Type IV The buckethandle tear of the superior labrum extends into the biceps anchor. Other types include a combination of SLAP with Bankart lesion (Type V) and extension of superior labral tear into the anterosuperior capsule (Type VI). Fig. 4 Mechanisms of Injury The many varieties of lesions suggest that more than one mechanism is involved in producing these lesions. 1.	Fall on outstretched hand. A fall with abducted and forward flexed arm can cause the humeral head to compress against the superior labrum 2.	Traction injury: Sudden inferior pulling of the arm as seen in water-skiing injuries can produce SLAP lesions14. 3.	Torsional Peel Back: In the cocking position (Abduction and Hyper-external rotation), the altered direction of pull of biceps tendon on the superior labrum can peel the superior labrum off the glenoid. This mechanism is also supported by recent biomechanical studies. This mechanism is responsible for the type II lesions seen in athletes.3,6,12 4.	Degeneration: It is common to find degenerative changes of superior labrum as well as long head of biceps in the elderly athletes.

Diagnosis: The diagnosis of SLAP lesions is clinical. SLAP lesions can be missed in routine MRI and a normal MRI does not exclude a SLAP lesion. The sensitivity of an MRI can be improved by an MR arthrogram with intraarticular gadolinium. On the other hand no SLAP test is specific and considerable overlap exists between other conditions like cuff, biceps and AC joint pathology.

O’Brien test (active compression test): In this test the subject’s arm is forward flexed to 90o and adducted to 20o and internal rotated to maximum. The examiner places his hand over the forearm and applies a downward force and the patient is asked to resist it. The test is repeated with the forearm supinated. In a positive test, pain produced with pronated forearm is reduced in supination. Pain, which is unaltered with supination, indicates other pathology like AC joint arthritis.13

Jobe’s test: Initially described for instability, the pain produced in the abducted external rotated position is relieved by a posteriorly directed force (relocation maneuver) applied to the proximal humerus. This test is positive in posterior SLAP lesions16 Compression-rotation test: In this test, the shoulder is abducted to 900 and an axial compression force is applied by pushing the elbow and then the arm is rotated internally and externally. SLAP lesions produce pain, or crepitus with this maneuver.14 Anterior Slide Test (Kibler): With the subject’s hand on his hip, the examiner stabilizes scapula with one hand and applies a superiorly directed force to the elbow and the patient is asked to resist the force. Pain or click indicates a positive test.14 Kim’s Biceps Load Test: With the subject supine, the arm is abducted to 120 degrees and elbow flexed to 90 and forearm pronated, the subject is asked to flex the elbow against the resistance. Pain indicates positive test. 15

PREVENTION Having seen that the posterior capsular contracture being the root cause of SLAP lesions, most of them are preventable. There exists a stage of “SHOULDER-AT-RISK” in which the GIRD exists without any pathology. Posterior capsular stretching exercises (fig 6) at this stage will stop the progression to SLAP lesions. 3

MANAGEMENT The basic principle of treatment depends on whether the biceps anchor is intact or not. If the biceps anchor is detached it has to be reattached. Preoperative stretching exercises for posterior capsule are advised. Rotations are examined under anaesthesia; gross loss of internal rotation (IR < 250) may need selective posteroinferior capsulotomy at the end.5,16 Superior labral fraying in Type I lesions requires debridement alone. Avulsions of superior labrum (Type II) require reattachment of the superior labrum to the glenoid. This is accomplished by the placement of suture anchors into the glenoid and the repairing the labrum on to it. The glenoid and labral tissue are freshened before the repair. (Fig 5)

In type III lesions, the inner rim of the labrum is detached from the rest and the biceps’ attachment to the labrum is intact. All that is needed is excision of the buckethandle segment. But in Type IV lesions, the buckethandle tear extends into the biceps root. The management depends on the involvement of biceps root. If the tear involves less than 50% of the biceps root, it can be excised and if it is more than 50% the torn segment is repaired to the remaining tissue. .

REHABILITATION After SLAP repair, pendular exercises are started from 3rd day onwards. Sling is used for 3 weeks. Posterior capsular stretching is continued indefinitely. Flexion, extension, passive external rotation with arm at side and posterior capsule stretching (sleeper stretches) are started immediately. onwards. (Fig 6) External rotation in abduction is started from 4 – 6 weeks. Rotator cuff strengthening and biceps strengthening are started from 6th & 8th weeks respectively. Rehabilitation of scapula muscles is also given importance. Gradual return to full overhead activity by 7 – 8 months is advised. 5,16 (Graphics and Line diagrams, except fig 1 by Dr. Clement Joseph)

REFERENCES : 1.	Burkhart SS, Morgan CD, Kibler WB. Current concepts. The disabled throwing shoulder. Part III Arthroscopy 2003;19:641-661 2.	Kibler WB. The role of scapula in athletic shoulder function Am J Sports Med 1998: 26:325-337 3.	Burkhart SS, Morgan CD, Kibler WB. Current concepts. The disabled throwing shoulder.Part I Arthroscopy 2003;4:404-420 4.	Jobe FW, Tibone JE, Pink MM. The shoulder in sports, in The Shoulder, Ed. Rockwood CA, 3rd Ed, Saunders, 2004 5.	Morgan C.D. Thrower’s Shoulder: two perspectives, in Operative Arthroscopy, Ed McGinty JB et al Lippincott Williams & Wilkins 2003 6.	Kuhn JE, Lindholm SR, Huston LJ, Soslowsky LJ, Blasier RB Failure of the biceps superior labral complex: A cadaveric biomechanical investigation comparing the late cocking and early deceleration positions of throwing Arthroscopy  2003 Vol. 19, 373-379) 7.	Jobe CM. Posterior superior glenoid impingement: expanded spectrum. Arthroscopy1 995;11:530-537 8.	Walch G, Boileau J, Noel E, et al. Impingement of the deep surface of the supraspinatus tendon on the posterior superior glenoid rim: An arthroscopic study. J Shoulder Elbow Surg 1992, 1:238-245. 9.	Rubin BD, Evaluation of the overhead athlete: Examination and Ancillary testing.Instructional course 104, Arthroscopy, 2003;19:42-46 10.	Andrews JR, Carson WG, et al: Glenoid labrum tears related to the long head of the biceps. Am J Sports Med 13:337-341, 1985 11.	Snyder SJ, Karzel RP et al : SLAP lesions of the shoulder. Arthroscopy 1990,6:274-279 12.	Burkhart SS, Morgan CD, Technical note : The “Peel-back mechanism: its role in producing and extending posterior type SLAP lesions and its effect on SLAP repair rehabilitation Arthroscopy 1998;14:637-640 13.	O’Brien SJ, Pagnani MJ. The active compression test: A new and effective test for diagnosing labral tears for diagnosing labral tears and acromioclavicular joint abnormality. Am J Sports Med 1998;26:610-613 14.	Maffet MW, Lowe WR, Superior labral injuries, Orthopedic Sports Medicine, vol. 1 Ed DeLee JC et al, WB Saunders, 2003, 1046-1064 15.	Kim SH et al Biceps Load Test II : A Clinical Test for SLAP lesions of the shoulder. Arthroscopy 2001;17:160-164 16.	Burkhart SS, Morgan CD, Kibler WB. Current concepts. The disabled throwing shoulder. Part II Arthroscopy 2003;19:531-539