Recurrent Dislocations

Clinical Features

In patients with recurrent dislocation or subluxation of the patella, an accurate history is still one of the most important diagnostic tools. Patellar problems can mimic various “internal derangements” of the knee. An accurate history of the mechanism of injury and the type and area of pain is important. Patients with patellar instability frequently report diffuse pain around the knee that is aggravated by going up and down stairs or hills. The pain usually is located anterior in the knee and often is described as an aching pain with intermittent episodes of sharp, severe pain. A feeling of insecurity in the knee and occasionally of “giving way” or “going out” of the knee may be present. Patellar crepitation and swelling of the knee are common. Physical findings include the previously cited factors that contribute to increasing the Q angle.

The examination begins by observing the patient’s patellar height, with the patient in the seated position. An upward tilt indicates patella alta. Dynamic patellar tracking is evaluated with the examiner standing in front of the seated patient while the patient slowly extends the knee. A positive J sign (slight lateral subluxation of the patella as the knee approaches full extension) indicates some degree of maltracking. Active patellar tracking also should be examined with the knee relaxed in the extended position. When the quadriceps muscle is tightened, motion of the patella is examined. Normally, the patella should move more superiorly than laterally. With the patient supine and the knee flexed 30 degrees with a bolster behind the knee, the Q angle is measured. Insufficiency of the femoral sulcus and the MPFL, which provide 60% of the medial stabilization, is tested by applying an inferolaterally directed stress while palpating the ligament. Displacement of more than two quadrants and a soft end point generally indicate MPFL insufficiency. The patellar grind test is done by applying pressure to the patella and manually displacing it medially, laterally, superiorly, and inferiorly in the trochlear groove. This test reproduces anterior knee pain when a patellofemoral pathologic condition is present.

For the “apprehension test,” the examiner holds the relaxed knee in 20 to 30 degrees of flexion and manually subluxes the patella laterally. When the test is positive, the patient suddenly complains of pain and resists any further lateral motion of the patella. The active apprehension test is more accurate: the same controlled maneuver is done while slowly flexing and extending the patient’s knee. Patella laxity is evaluated by visually dividing the patella into four quadrants and passively moving the patella medially and then laterally, measuring the amount of excursion in the patellar quadrants. This is done with the knee at 0 degrees and at 20 degrees of flexion. Normally, passive patellar glide is one to two quadrants medially and laterally; motion of more than two quadrants indicates soft-tissue laxity. Excessive lateral retinacular tightness is indicated by limited medial passive patellar glide and by a negative patellar tilt. The patellar tilt test is done with the knee in 20 degrees of flexion. The examiner’s fingers are placed along the medial side of the patella with the thumb on the lateral aspect. Inability to raise the lateral facet to the horizontal plane or slightly past indicates excessive lateral retinacular tightness. Tenderness along the MPFL, medial patellar facet, and lateral condyle are common with stability.

Thigh circumferences measured proximal to the patella often show quadriceps atrophy on the involved side. With the patient sitting and the knees flexed 90 degrees, a lateral or superior position of the patella sometimes can be seen. After careful examination of the uninvolved and injured knees, other joints should be examined for hyperlaxity. Hyperextension of the knees or elbows past 10 degrees, ability to touch the thumb passively to the forearm, hyperextension of the metacarpophalangeal joint of the index finger, and multidirectional laxity of the shoulder joint all are indicative of generalized ligamentous laxity. Patients with generalized ligamentous laxity have been found to have fewer articular lesions associated with dislocations than patients without ligamentous laxity. The thigh-foot angle is measured with the patient prone and the knee flexed 90 degrees. An angle of more than 30 degrees indicates significant rotational deformity of the lower extremity. The final part of the examination is done with the patient standing and consists of observation for malalignment (i.e., femoral anteversion, genu valgum, external tibial torsion, and pes planus) and core condition.

Radiographic Features ( Table 47.1 )

The anteroposterior view of the knee can be used to confirm valgus alignment and lateral position of the patella and to look for osteochondral damage. The lateral view of the knee is helpful in determining patella alta. Blumensaat showed that with the knee flexed 30 degrees, a line extending through the intercondylar notch should just touch the lower pole of the patella ( Fig. 47.1 ).

Patellar height is more accurately evaluated by the Insall, Clanton, or Blackburn-Peel index (see Table 47.1 ). The crossover sign is the best indicator of trochlear dysplasia—the earlier the crossover, the more dysplasia present. A trochlear depth of less than 3 mm or trochlear bump of more than 4 mm indicates significant dysplasia.

The most important routine view of the patellofemoral joint is the axial view of the patella. Several methods have been described for taking this axial view ( Fig. 47.2B ). For this radiograph to be meaningful, both knees should be exposed at the same time for comparison. The plane of the film should be perpendicular to the x-ray beam to avoid distortion, the legs should be held vertical to prevent rotation that might simulate low lateral femoral condyles, the quadriceps muscles should be relaxed to prevent the patella from being reduced at the time the radiograph is made, and the knee should be flexed in the range of 20 to 45 degrees because more flexion generally reduces most patellofemoral abnormalities.

When the axial view has been obtained, the shape of the patella should be evaluated, along with the shape of the femoral trochlea and the relationship of the patella to the femur. Normally, the patella appears evenly seated within the trochlear groove of the femur, with an equal distance between both patellar facets and the adjacent femoral surfaces. Abnormalities include tilting of the patella or subluxation and complete dislocation of the patella ( Fig. 47.3 ). The trochlea is evaluated on the Merchant view for dysplasia, sulcus angle greater than 145 degrees, and congruence—normally 60 ± 11 degrees ( Figs. 47.4 and 47.5 ). For most dislocations or first-time dislocations, particularly in athletes, MRI or three-dimensional (3D) CT examination may be indicated to evaluate for chondral damage, loose bodies, dysplasia, and malalignment. An axial view at the superior trochlear groove is used to evaluate dysplasia; superimposed views are used to evaluate malalignment. Tibial tubercle–trochlear groove (TT-TG) distance of more than 20 mm on CT ( Fig. 47.6 ) or MRI may indicate malalignment and may necessitate distal realignment.

Conservative Treatment

Surgical Treatment of Patellar Instability

First-time dislocations generally are treated conservatively with good results, except for patients with open physes and trochlear dysplasia, two thirds of whom will have a recurrence. These patients and those who have recurrent instability of the contralateral patella may require more aggressive treatment ( Table 47.2 ).

Choosing treatment for malalignment requires thorough evaluation, imaging, and planning. Many instabilities are multifactorial and must be treated as such. Containment issues are most commonly treated by reconstruction of the medial quadriceps tendon–femoral ligament (MQTFL) or the MPFL. Avulsion from the patella can be repaired with some success. Severe dysplasia can be directly treated with trochleoplasty, with good stability results, but often with persistent pain and swelling and the potential for chondral damage.

Malalignment measured by a tibial tubercle–to–trochlear groove (TT-TG) distance of 20 mm with a normal trochlea or a TT-TG of more than 15 mm with a dysplastic trochlea is treated with tibial tuberosity osteotomy.

When patellar chondral damage is distal and lateral, an anterior medialization of the tuberosity can stabilize and unload the cartilage defect. Medialization procedures are contraindicated for proximal and medial chondral defects. It has been noted that an oblique tuberosity osteotomy of 30 degrees produces 1 mm of anterior elevation for each 2 mm of medial displacement. A 45-degree oblique osteotomy produces 1 mm anterior to 1 mm medial displacement. Rarely, for severe angulation deformities, distal femoral rotational osteotomy is indicated.

Patellar instability in patients with open physes can be treated by MPFL reconstruction avoiding the physis or, occasionally, soft-tissue distal patellar tendon realignment. For angular deformities, epiphysiodesis can be used to aid realignment; soft-tissue repairs have a high failure rate.

A number of factors may contribute to patellar instability, and all must be corrected for optimal results ( Table 47.3 ). For instability with normal alignment and Dejour type A or B dysplasia, MQTFL reconstruction is indicated. Distal realignment may be indicated for dysplasia for a TT-TG distance of 15 mm. Lateral release is not an operation for instability but is indicated as an additional procedure only if the tight tissues prevent the patella from relocating. Routine lateral release should not be done because it may create more instability.

Iatrogenic Medial Patellar Instability

Iatrogenic medial patellar instability is diagnosed when manual medial subluxation re-creates a patient’s symptoms. Treatment consists of repairing the vastus lateralis if previously released and revising a distal realignment to a more lateral position. If the initial procedure was proximal and inadequate tissues remain, repair or reconstruction using the lateral portion of the patellar tendon is done ( Fig. 47.12 ).

Normal Functional Anatomy

An understanding of the normal functional anatomy of the shoulder is necessary to understand the factors influencing the stability of the joint. The bony anatomy of the shoulder joint does not provide inherent stability. The glenoid fossa is a flattened, dish-like structure. Only one fourth of the large humeral head articulates with the glenoid at any given time. This small, flat glenoid does not provide the inherent stability for the humeral head that the acetabulum does for the hip. The glenoid is deepened by 50% by the presence of the glenoid labrum. The labrum increases the humeral contact to 75%. Integral to the glenoid labrum is the insertion of the tendon of the long head of the biceps, which inserts on the superior aspect of the joint and blends to become indistinguishable from the posterior glenoid labrum. Matsen et al. suggested that the labrum may serve as a “chock block” to prevent excessive humeral head rollback. The shoulder joint capsule is lax and thin and, by itself, offers little resistance or stability. Anteriorly, the capsule is reinforced by three capsular thickenings or ligaments that are intimately fused with the labral attachment to the glenoid rim.

The superior glenohumeral ligament attaches to the glenoid rim near the apex of the labrum conjoined with the long head of the biceps ( Fig. 47.15 ). On the humerus, it is attached to the anterior aspect of the anatomic neck of the humerus ( Fig. 47.16 ). The superior glenohumeral ligament is the primary restraint to inferior humeral subluxation in 0 degrees of abduction and is the primary stabilizer to anterior and posterior stress at 0 degrees of abduction. Tightening of the rotator interval (which includes the superior glenohumeral ligament) decreases posterior and inferior translation; external rotation also may be decreased. The middle glenohumeral ligament has a wide attachment extending from the superior glenohumeral ligament along the anterior margin of the glenoid down as far as the junction of the middle and inferior thirds of the glenoid rim. On the humerus, it also is attached to the anterior aspect of the anatomic neck. The middle glenohumeral ligament limits external rotation when the arm is in the lower and middle ranges of abduction but has little effect when the arm is in 90 degrees of abduction. The inferior glenohumeral ligament attaches to the glenoid margin from the 2- to 3-o’clock positions anteriorly to the 8- to 9-o’clock positions posteriorly. The humeral attachment is below the level of the horizontally oriented physis into the inferior aspect of the anatomic and surgical neck of the humerus. The anterosuperior edge of this ligament usually is quite thickened. There is a less distinct posterior thickening, a hammock-type model consisting of thickened anterior and posterior bands and a thinner axillary pouch. With external rotation, the hammock slides anteriorly and superiorly. The anterior band tightens, and the posterior band fans out. With internal rotation, the opposite occurs. The anteroinferior glenohumeral ligament complex is the main stabilizer to anterior and posterior stresses when the shoulder is abducted 45 degrees or more. The ligament provides a restraint at the extremes of motion and assists in the rollback of the humeral head in the glenoid.

The muscles around the shoulder also contribute significantly to its stability. The action of the deltoid (the principal extrinsic muscle) produces primarily vertical shear forces, tending to displace the humeral head superiorly. The intrinsic muscle forces from the rotator cuff provide compressive or stabilizing forces. Concavity compression is produced by dynamic rotator cuff muscular stabilization of the humeral head when the concavity of the glenoid and labral complex is intact. Loss of the labrum can reduce this stabilizing effect by 20%. In the concavity of the glenoid-labral complex, synchronous eccentric deceleration, and concentric contraction of the rotator cuff and biceps tendon are necessary for humeral stability during midranges of humeral motion. Asynchronous fatigue of the rotator cuff from overuse or incompetent ligamentous support can result in further damage to the static and dynamic supports. MRI studies have shown fatty infiltration and thinning of the subscapularis tendon in recurrent anterior instability.

Several authors have noted the importance of synchronous mobility of the scapula and glenoid to shoulder stability and emphasized the importance of this dynamic balance to appropriate positioning of the glenoid articular surface so that the joint reaction force produced is a compressive rather than a shear force. With normal synchronous function of the scapular stabilizers, the scapula and the glenoid articular structures are maintained in the most stable functional position. Strengthening rehabilitation of the scapular stabilizers (serratus anterior, trapezius, latissimus dorsi, rhomboids, and levator scapulae) is especially important in patients who participate in upper extremity-dominant sports. Although the glenoid is small, it has the mobility to remain in the most stable position in relation to the humeral head with movement. Rowe compared this with a seal balancing a ball on its nose. The glenoid also has the ability to “recoil” when a sudden force is applied to the shoulder joint, such as in a fall on the outstretched hand. This ability to “recoil” lessens the impact on the shoulder as the scapula slides along the chest wall.

Scapular dyskinesis is an alteration of the normal position or motion of the scapula during coupled scapulohumeral movements and can occur after overuse of and repeated injuries to the shoulder joint. A particular overuse muscle fatigue syndrome has been designated the SICK scapula: scapular malposition, inferior medial border prominence, coracoid pain and malposition, and dyskinesis of scapular movement.

The demonstration of Ruffini end organs and Pacinian corpuscles in the shoulder capsule helps solidify the concept of proprioceptive neuromuscular training as an important part of shoulder stabilization. Another force that has a lesser effect on glenohumeral stability is glenoid version. Glenoid version probably is not a significant contributor to instability except in a severely deformed shoulder. Cohesion produced by joint fluid and the vacuum effect produced by negative intraarticular pressure in normal shoulders play lesser roles in joint stability.

Pathologic Anatomy

No essential pathologic lesion is responsible for every recurrent subluxation or dislocation of the shoulder. In 1906, Perthes considered detachment of the labrum from the anterior rim of the glenoid cavity to be the “essential” lesion in recurrent dislocations and described an operation to correct it. In 1938, Bankart published his classic paper in which he recognized two types of acute dislocations. In the first type, the humeral head is forced through the capsule where it is the weakest, generally anteriorly and inferiorly in the interval between the lower border of the subscapularis and the long head of the triceps muscle. In the second type, the humeral head is forced anteriorly out of the glenoid cavity and tears not only the fibrocartilaginous labrum from almost the entire anterior half of the rim of the glenoid cavity but also the capsule and periosteum from the anterior surface of the neck of the scapula. This traumatic detachment of the glenoid labrum has been called the Bankart lesion . Most authors agree that the Bankart lesion is the most commonly observed pathologic lesion in recurrent subluxation or dislocation of the shoulder, but it is not the “essential” lesion.

Excessive laxity of the shoulder capsule also causes instability of the shoulder joint. Excessive laxity can be caused by a congenital collagen deficiency, shown by hyperlaxity of other joints, or by plastic deformation of the capsuloligamentous complex from a single macrotraumatic event or repetitive microtraumatic events. Hyperlaxity has been implicated as a cause of failure in surgical correction of chronic shoulder instability. An arthroscopic study of anterior shoulder dislocations found that 38% of the acute injuries were intrasubstance ligamentous failures, and 62% were disruptions of the capsuloligamentous insertion into the glenoid neck. The “circle concept” of structural damage to the capsular structures was suggested by cadaver studies that showed that humeral dislocation does not occur unless the posterior capsular structures are disrupted, in addition to the anterior capsular structures. Posterior capsulolabral changes associated with recurrent anterior instability often are identified by arthroscopy.

A humeral head impaction fracture can be produced as the shoulder is dislocated, and the humeral head is impacted against the rim of the glenoid at the time of dislocation. This Hill-Sachs lesion is a defect in the posterolateral aspect of the humeral head. Instability results when the defect engages the glenoid rim in the functional arc of motion at 90 degrees abduction and external rotation. In a cadaver model, humeral head defects of 35% to 40% were shown to decrease stability, whereas glenoid defects of as little as 13% were found to decrease stability. Glenoid rim fractures or attrition also can occur with an anterior or posterior dislocation. If these lesions involve more than 20% to 25% of the glenoid, they can result in recurrent instability despite having an excellent soft-tissue repair. These lesions are difficult to see on plain radiographs; if a defect is visible in an acute dislocation or one is evaluating recurrent instability, (3D) CT is the best method for evaluating the extent of the defect ( Fig. 47.17 ).

It seems that no single “essential” lesion is responsible for all recurrent dislocations of the shoulder. Stability of this inherently unstable joint depends on a continuing balance between the static and dynamic mechanisms influencing motion and stability. In addition to the various possible primary deficiencies influencing instability, secondary deficiencies can be caused by repeated dislocations. Erosion of the anterior glenoid rim, stretching of the anterior capsule and subscapularis tendon, and fraying and degeneration of the glenoid labrum all can occur with repeated dislocation. The primary deficiency and the secondary deficiencies need to be considered at the time of surgery and in postoperative rehabilitation to correct the instability. Because no single deficiency 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 present to choose the proper procedure.

Classification

Successful treatment of shoulder instability is based on a thorough understanding of the various posttraumatic lesions that can be associated with a deficient capsulolabral complex and on correct classification of the patient’s primary and secondary lesions. Classification and treatment of shoulder instability are based on the direction, degree, and duration of symptoms; the trauma that resulted in instability; and the patient’s age, mental set, and associated conditions, such as seizures, neuromuscular disorders, collagen deficiencies, and congenital disorders.

The direction of instability should be categorized as unidirectional, bidirectional, or multidirectional. Anterior dislocations account for 90% to 95% of recurrent dislocations, and posterior dislocations account for approximately 5% to 10%. Despite increased understanding of shoulder instability, 50% of posterior shoulder dislocations can be missed unless an adequate examination and appropriate radiographs are done. Inferior and superior dislocations are rare. Superior instability generally arises secondary to severe rotator cuff insufficiency.

Instability is categorized as subluxation with partial separation of the humeral head from the glenoid or dislocation with complete separation of the humeral head from the glenoid concavity. The duration of the symptoms should be recorded as acute, subacute, chronic, or recurrent. The dislocation is classified as chronic if the humeral head has remained dislocated longer than 6 weeks.

The type of trauma associated with the dislocation is important in determining whether conservative or operative treatment is appropriate. Instability should be categorized as macrotraumatic , in which a single traumatic event results in dislocation, or microtraumatic (acquired), in which repetitive trauma at the extremes of motion results in plastic deformation of the capsulolabral complex. Secondary trauma to the rotator cuff and biceps tendon may cause asynchronous rotator cuff function. These injuries most commonly occur in pitchers, batters, gymnasts, weightlifters, tennis players and others who play racquet sports, and swimmers, especially with the backstroke or butterfly stroke. The flexibility that allows an athlete to compete at a high level may be attributed to a generalized ligamentous laxity, which also predisposes the athlete to injury. Trauma may cause decompensation of a previously stable capsuloligamentous complex. A thorough history of the initial traumatic event, symptoms, and family history and a thorough examination of the injured shoulder, contralateral shoulder, and other joints are necessary.

Age also is important in predicting pathologic lesions and outcomes, with recurrence rates of more than 90% reported in patients younger than 20 years old compared with a recurrence rate of about 10% to 20% in patients older than 40 years old.

In most studies, the recurrence rate for adolescents treated with surgical stabilization was higher than that for patients in other age groups. These differences can be explained by the greater elasticity in adolescent ligaments that results in greater plastic deformation before failure of the system. This deformation must be considered in surgical treatment approaches.

Although recurrence of the dislocation is uncommon in patients 40 years old or older, associated rotator cuff tears are present in 30%, and such tears are present in more than 80% of patients older than 60 years. Fractures of the greater tuberosity also are more prevalent in patients older than 40 years old; some series report an incidence of 42%. In this age group, surgical treatment of rotator cuff tears or fractures of the greater tuberosity generally takes precedence over treatment of the capsular injury.

The mental set of the patient must be evaluated before treatment is started. Some patients with posterior instability learn to dislocate their shoulder through selective muscular contractions. Although voluntary dislocation does not indicate pathologic overlay, some of these patients have learned to use voluntary dislocation for secondary gain, and in these patients surgical treatment is doomed to failure.

In patients with primary neuromuscular disorders or syndromes and recurrent dislocation, conservative, nonoperative treatment should be the initial approach. If instability remains after appropriate medical treatment, surgery may be necessary in conjunction with continued nonoperative treatment. Patients with primary collagen disorders, Ehlers-Danlos syndrome, or Marfan syndrome should be treated with extensive supervised conservative treatment. If surgical intervention becomes necessary, the possibility of the abnormal tissue stretching out and allowing dislocation to recur should be stressed to the patient and family. When severe dysplastic or traumatic glenohumeral deformity is present, capsular and bony procedures may be necessary. Reformatted 3D CT images are beneficial in determining the need for osteotomy or bone grafting procedures in these patients.

Matsen’s simplified classification system is useful for categorizing instability patterns: TUBS (traumatic, unidirectional Bankart surgery) and AMBRII (atraumatic, multidirectional, bilateral, rehabilitation, inferior capsular shift, and internal closure). Microtraumatic or developmental lesions fall between the extremes of macrotraumatic and atraumatic lesions and can overlap these extreme lesions ( Fig. 47.18 ). Classification of 168 shoulders according to four systems used for describing shoulder instability revealed variations in the criteria that resulted in marked variations in the number of patients diagnosed with multidirectional instability.

History

The history is important in recurrent instability of the shoulder joint. The amount of initial trauma, if any, should be determined. High-energy traumatic collision sports and motor vehicle accidents are associated with an increased risk of glenoid or humeral bone defects. Recurrence with minimal trauma in the midrange of motion often is associated with bony lesions, which must be treated. The position in which the dislocation or subluxation occurs should be elicited. In complete dislocations, the ease with which the shoulder is relocated is determined. Dislocations that occur during sleep or with the arm in an overhead position often are associated with a significant glenoid defect that requires surgical treatment.

Dislocations that are reduced by the patient often are subluxations or dislocations associated with generalized ligamentous laxity. The signs and symptoms of any nerve injury should be elicited. Most important, the physical limitations caused by this instability should be documented.

Recurrent subluxation of the shoulder is commonly overlooked by physicians because the symptoms are vague and there is no history of actual dislocation. The patient may complain of a sensation of the shoulder sliding in and out of place, or he or she may not be aware of any shoulder instability. The patient may complain of having a “dead arm” as a result of stretching of the axillary nerve or of secondary rotator cuff symptoms. It is important to differentiate primary from secondary rotator cuff impingement. Rotator cuff symptoms develop secondary to ligamentous dysfunction. Internal impingement of the undersurface of the posterior rotator cuff against the posterior glenoid and labrum is caused by anterior humeral subluxation with the shoulder externally rotated. This secondary impingement is more common than primary impingement in patients younger than 35 years old who are involved in upper extremity–dominant sports. Posterior shoulder instability may present as posterior pain or fatigue with repeated activity (e.g., blocking in football, swimming, bench press, rowing, and sports requiring overhead arm movement).

Physical Examination

The physical examination of a patient with instability begins by asking the patient which arm position creates the instability, what direction the shoulder subluxes, and if he or she can safely demonstrate the subluxation. Both shoulders should be thoroughly examined, with the normal shoulder used as a reference. The examination includes evaluation of the shoulders for atrophy or asymmetry, followed by palpation to determine the amount of tenderness present in the anterior or posterior capsule, the rotator cuff, and the acromioclavicular joint. Active and passive ranges of motion are evaluated with the patient upright and supine to record accurately the motion in all planes. The strengths of the deltoid, rotator cuff, and scapular stabilizers are evaluated, recorded, and graded from 0 to 5, with 5 being normal. Scapular winging or dysfunction should be noted during active range of motion and during strength examination. Winging may indicate scapular weakness and can be evaluated by having the patient do a press-up from the examination table or an incline type of push-up off the wall.

Stability is evaluated with the patient upright. A “shift-and-load” test is done by placing one hand along the edge of the scapula to stabilize it and grasping the humeral head with the other hand and applying a slight compressive force. The amount of anterior and posterior translation of the humeral head in the glenoid is observed with the arm abducted 0 degrees. Easy subluxation of the shoulder indicates loss of the glenoid concavity, which must be surgically treated.

The sulcus test is done with the arm in 0 degrees and 45 degrees of abduction. This test is done by pulling distally on the extremity and observing for a sulcus or dimple between the humeral head and the acromion that does not reduce with 45 degrees of external rotation. The distance between the humeral head and acromion should be graded from 0 to 3 with the arm in 0 degrees and 45 degrees of abduction, with 1+ indicating subluxation of less than 1 cm, 2+ indicating 1 to 2 cm of subluxation, and 3+ indicating more than 2 cm of inferior subluxation that does not reduce with external rotation. Subluxation at 0 degrees of abduction is more indicative of laxity at the rotator interval, and subluxation at 45 degrees indicates laxity of the inferior glenohumeral ligament complex.

Anterior apprehension is evaluated with the shoulder in 90 degrees of abduction and the elbow in 90 degrees of flexion, with a slight external rotation force applied to the extremity as anterior stress is applied to the humerus. This generally produces an apprehension reaction in a patient who has anterior instability. Control of the proximal humerus should be maintained during any of the apprehension or stress tests to prevent dislocation during these procedures. Posterior instability can be evaluated with a Kim test or a posterior clunk test, in which the 90-degree abducted extremity is brought to a forward flexed, internally rotated position while posterior stress is applied to the elbow. The clunk is felt as the humeral head subluxes posteriorly, producing pain or a feeling of subluxation in an unstable shoulder.

The shoulder anterior drawer test should be performed with the patient supine and the extremity in various degrees of abduction and external rotation in the plane of the scapula. When examining the patient’s right shoulder, the examiner’s left hand is used to grasp the proximal humerus while the right hand is used to hold the elbow lightly. Anterior stress is applied to the proximal humerus using the left hand, and the amount of translation and the end point are evaluated. In performing this and other anterior or posterior instability tests, the amount of instability is graded from 0 to 3. Grade 1 means that the humeral head slips up to the rim of the glenoid, and grade 2 means that it slips over the labrum but then spontaneously relocates. Grade 3 indicates dislocation. A grade 3 instability should not be exhibited in an awake patient. Anterior stress is applied with the shoulder in various degrees of abduction and external rotation, and posterior stress is applied to evaluate for posterior instability with the arm in 90 degrees of abduction and various degrees of flexion. When examining the patient’s right shoulder, posterior stress is applied with the examiner’s right hand, starting at 0 degrees of forward flexion and internal rotation and proceeding to 110 degrees. The examiner’s left hand stabilizes the scapula and palpates the posterior part of the glenohumeral joint with the palm. It also can be used as a buttress to ensure that posterior dislocation does not occur during this procedure. Apprehension is evaluated with anterior and posterior stress during these procedures.

The Jobe relocation test can be used for evaluating instability in athletes involved in sports requiring overhead motion ( Fig. 47.19 ). This test is done with the patient supine and the shoulder in 90 degrees of abduction and external rotation. Various degrees of abduction are evaluated while anterior stress is applied by the examiner’s hand to the posterior part of the humerus. If this produces pain or apprehension, posteriorly directed force is applied to the humerus to relocate the humeral head in the glenohumeral joint while the shoulder is placed in abduction and external rotation. The posteriorly directed stress used to relocate the humerus is released. A feeling of apprehension or subluxation on the part of the patient indicates anterior instability.

Bony deformity of the glenoid or humerus is indicated by apprehension or instability at low ranges of motion (<90 degrees of abduction) and when inferior instability is prominent. Hyperlaxity is indicated by a positive sulcus test, a positive Gagey hyperabduction test, and the Beighton hyperlaxity scale ( Table 47.4 ). The hyperabduction test is done by stabilizing the scapula with one hand placed superiorly while passively abducting the shoulder with the other hand. A side-to-side difference of more than 20 degrees is suggestive of inferior capsular laxity. External rotation of more than 85 degrees at 0 degrees of abduction is indicative of hyperlaxity, which may need to be corrected with rotator interval closure.

It is imperative to distinguish secondary rotator cuff impingement from primary impingement. The relocation and anterior apprehension tests are valuable in young athletes in sports requiring throwing or overhead motion. It also is imperative to rule out scapular dysfunction that can be corrected with physical therapy. Although rarely associated with shoulder instability, neck problems should be also ruled out, such as degenerative discs or degenerative arthritis that causes pain radiating into the posterior or lateral aspect of the shoulder.

Radiographic Evaluation

The diagnosis of an unstable shoulder often is made by history and physical examination, but an unstable shoulder can be documented by routine radiographs. The initial radiographic examination should include anteroposterior and axillary lateral views of the shoulder. If the initial radiographic evaluation is inconclusive, special views, gadolinium-enhanced MRI, or CT arthrography can be used to show posttraumatic changes not otherwise detected. The most common special views that can be obtained in the office are the anteroposterior view of the shoulder in internal rotation, the West Point or Rokous view, and the Stryker notch view. An anteroposterior radiograph of the shoulder in internal rotation often shows a Hill-Sachs lesion that may not be apparent on routine views. Garth et al. also described an apical oblique radiograph that frequently shows posterior humeral head defects that might not be seen on routine films ( Fig. 47.20 ). The West Point view is used to show calcification or small fractures at the anteroinferior glenoid rim. This is a modified, prone, axillary lateral view of the shoulder obtained with the shoulder abducted 90 degrees and the elbow bent with the arm hanging over the side of the table. The x-ray beam is directed 25 degrees medially and 25 degrees cephalad with the cassette placed above the shoulder perpendicular to the table ( Fig. 47.21 ). The Stryker notch view is obtained with the patient supine and the elbow elevated over the head. The x-ray beam is directed 10 degrees cephalad ( Fig. 47.22 ).

MRI or MRA is indicated for evaluating soft-tissue lesions associated with instability. MRI obtained within a few days of dislocation generally shows blood in the joint, which can aid in visualization and make MRA unnecessary. MRA is helpful in evaluating humeral avulsion glenohumeral ligament (HAGL) lesions, but occasionally it may show a tear but actually cover up the details of the exact tear site ( Fig. 47.23 ). Evaluation of the glenoid track, as described by Yamamoto et al., evaluates Hill-Sachs lesions based on both the location and size of the humeral head defect and the amount of glenoid bone loss. It has been shown to be highly predictive in a clinical setting. Metzger et al. found that lesions falling outside the track engaged more than 85% of the time. The examination is measured on MRI ( Fig. 47.24 ) and is essential in determining appropriate surgical intervention for on-track versus off-track lesions.

CT, particularly 3D CT, is the most sensitive test for detecting and measuring bone deficiency or retroversion of the glenoid or humerus for evaluation of recurrent instability. CT is indicated when there is blunting of the glenoid cortical outline or an obvious bone defect on plain radiographs. CT also is indicated for evaluating recurrences that occur with trivial trauma, low-angle instability, and failed surgical procedures ( Fig. 47.25 ).

Examination Using Anesthetic and Arthroscopy

Examination with the patient under anesthesia may support the clinical diagnosis or sometimes show unsuspected planes of instability, especially in multidirectional instability patterns. For anterior instability, the arm is abducted. Anterior and posterior stress is applied with the scapula stabilized. Minimal anterior translation of the humeral head occurs unless there is instability. The most significant findings of instability are demonstrable at 40 degrees and 80 degrees of external rotation. Translation of two grades more than the opposite uninvolved side resulted in 93% sensitivity and 100% specificity for instability. For posterior instability, the arm is pushed posteriorly. Normal shoulders may permit posterior displacement of 50% of the diameter of the glenoid without pathologic instability.

Arthroscopy can be combined with examination using anesthesia and is an excellent technique for confirming the presence of shoulder instabilities. The examiner should grade the instability in all planes as previously described, remembering that this examination under anesthesia is used to support the clinical history and examination with the patient awake. Arthroscopy should be performed to identify all intraarticular pathology so that treatment may be rendered accordingly. Arthroscopy portals and time should be limited to reduce extravasation into the soft tissues, which can make surgical exposure more difficult.

Anterior Instability of the Shoulder