In The Name of GOD

The Soulder Instability A. Zarezadeh MD

Pathological anatomy No essential pathological lesion is responsible for every recurrent dislocation of the shoulder Bankart in 1938 reported two types of acute dislocations In the first type, the humeral head forced through the weakest capsule in the antero-inferior part of the shoulder. In the second type, the humeral head is forced anteriorly and tears the labrum and also the capsule and periosteum from the anterior neck of the scapula. This detach met of the glenoid labrum has been called the Bankart lesion. Most authors agree that Bankart lesion is the most common pathological lesion in recurrent dislocation of the shoulder.

Pathological anatomy Excessive laxity of the capsule also causes the instability of the shoulder (congenital collagen deficiency) A big humeral head impaction fracture at the postero-lateral aspect of the humeral head, that has been called Hill-Sachs lesion can produce shoulder instability. 3D CT is the best method for evaluating the extent of the defect.

Pathological anatomy It seems that no single essential lesion is responsible for all recurrent dislocations of the shoulder. No single operative procedure can be applied to every patient. The surgeon must search carefully for and identify the deficiencies to choose proper procedure.

Classification Successful treatment of shoulder instability is based on the through understanding of the pathological lesions and correct classification of the shoulder instability. Classification and treatment are based on: The direction, degree and duration of symptoms The trauma that resulted in instability The patient’s age, mental set and associated medical conditions (such as: seizures, neuromuscular disorders, collagen deficiencies and congenital disorders)

Classification The direction of instability can be categorized as: Unidirectional Bidirectional Multidirectional

Classification Anterior recurrent dislocation account for about 95% Posterior recurrent dislocation account for about 5% Inferior and superior dislocations are rare Superior instability generally arises secondary to severe R.C. insufficiency. About 50% of posterior dislocations can be missed

Classification Instability is categorized as: Subluxation or dislocation The duration of the symptoms should be recorded as: Acute Sub acute Chronic (when the humeral head has remained dislocated longer than 6 weeks.) Recurrent

Age Age is an important factor in predicting pathological lesions and outcomes. Recurrent rate is more than 90% in patients younger than 20 years old. Recurrent rate is about 10% in patients older than 40 years old. Associated R.C. tearing is about 30% in patients older than 40 years old. R.C. tearing in patients older than 60 years old is approximately 80%. Greater tuberosity fx is common in patients older than 40 years old.

In patients with medical conditions, such as: Primary collagen disorders (Ehlers-Danlos, Marfan) and neuromuscular disorders conservative treatment should be the initial approach.

Matsen’s Classification system is useful for categorizing instability patterns TUBS (Traumatic Unidirectional Bankart Surgery) AMBRII (Atraumatic Multidirectional Bilateral Rehabilitation if surgery is necessary Inferior capsular shift and Interval closure)

Matsen’s classification system

History The history is important in recurrent instability of the shoulder The amount of initial trauma should be determined. High-energy traumatic collision sports and motor vehicle accidents are associated with a risk of bone defect. The position, in which the dislocation or subluxation occurs, should be asked. Dislocations that occur during sleep or with the arm in overhead position often are associated with a glenoid defect that requires surgical treatment. Dislocations that are reduced by the patient often are subluxations or dislocations with ligamentous laxity.

History The signs and symptoms of any nerve injury should be recorded. In recurrent subluxations, the patient complaint is a sensation of the shoulder sliding in and out of glenoid. The patient may complain of having a “dead arm” as a result of axillary nerve injury or secondary R.C. syndrome. Posterior shoulder instability may present as posterior pain or fatigue with repeated activities.

Physical examination In physical examination of an unstable shoulder: The patient should be asked, which position creates instability? What is the direction of shoulder subluxation or dislocation? Both shoulders should be examined with the normal shoulder used as a reference. The examination includes: Evaluation for any atrophy or asymmetry Palpation for any tenderness in anterior or posterior capsule RC and AC joint. Active and passive ROM should be evaluated. The muscle testing of the deltoid, RC muscles and scapular stabilizers should be done, graded and recorded from 0 to 5.

Physical examination The “shift and load” test is done. The amount of anterior and posterior translation of the humeral head in the glenoid is observed. The sulcus test- is done with the arm 0 degree and 45 degrees of abduction and should be graded 0 to 3. The anterior apprehension -is evaluated with the shoulder in 90 degrees of abduction, elbow in 90 degrees of flexion and then slight external rotation force. This test is positive in anterior instability.

Physical examination Posterior instability of the shoulder can be evaluated with a posterior clunk test. (90 degrees abduction is brought to a forward flexion and internally rotated position while posterior stress is applied to the elbow) The clunk is felt and producing pain and feeling of subluxation in an unstable shoulder. The shoulder anterior drawer test (The patient in a supine position and extremity in abduction and external rotation) The Jobe relocation test can be used for evaluating instability. A feeling of subluxation or apprehension indicates anterior instability.

Radiographic evaluation Diagnosis of an unstable shoulder often is made by history and physical examination. An unstable shoulder can be documented by radiographs The initial radiographic examination is AP and axillary lateral views.

Radiographic evaluation If the initial radiographic evaluation is inconclusive Special views Gadolinium enhanced MRI CT arthrography can be used to show post traumatic changes

Radiographic evaluation The most common special views are: AP of the shoulder in internal rotation for evaluation of Hill-Sachs The west point or Rokous view to show calcification of antro-inferior glenoid rim. Stryker notch view Standard double-contrast arthrography CT scan, particularly 3D is the most sensitive test for detecting and measuring bone deficiency. Double contrast CT arthrography MRI is useful in evaluating soft tissue lesions associated with instability.

The End