Mark Lazarus
Vip Nanavati
Anterior dislocation of the glenohumeral joint is among the most common traumatic dislocations in the human body. The soft tissues to the glenohumeral joint must be disrupted for the humeral head to escape the glenoid fossa. The most important factor determining the location of tissue disruption is the age of the patient. In patients older than 40 years of age, the posterior mechanism of dislocation is common. This involves a tear in the rotator cuff with or without labral tissue involvement. In patients younger than 40 years of age, the predominant tissue injury is a tear of the anterior inferior glenoid labrum (Bankart tear). A study delineating the arthroscopic findings after initial traumatic anterior dislocation in patients younger than 24 years of age revealed that 61 of 63 patients (97%) sustained an avulsion of the anterior inferior glenoid labrum. Fourteen of the 63 patients (22%) had an associated osseous lesion of the glenoid rim. The most important risk for recurrence after initial dislocation may be the underlying pathologic tissue disruption. An arthroscopic study of 45 patients who sustained an initial traumatic dislocation showed that most had Bankart tears. Moreover, these patients also were found to have gross instability on examination under anesthesia. Six of the 45 patients who did not have labral pathology were found to be stable on examination under anesthesia.
Multiple studies have addressed the outcomes of patients after first-time traumatic anterior dislocation. The risk of recurrence after initial dislocation has been reported as high as 95% for patients younger than 20 years of age. For patients younger than 25 years of age, the recurrence rate has been reported as high as 50% to 75%. After the age of 25 years, the risk of recurrence has been shown to rapidly decrease. Despite the varying rates of recurrence that have been reported, studies have clearly demonstrated that the risk of recurrence after initial traumatic anterior dislocation is extremely high. This risk is inversely related to the age of the patient at the time of initial dislocation. Therefore, treatment should be based on the age of the patient.
Patient Presentation and Evaluation
Diagnosis of an anterior glenohumeral dislocation is normally a straightforward process. The patient's history most often presents a mechanism of an eccentrically applied load to the hand while the arm is outstretched. At presentation, the patient typically appears as leaning forward with the humerus in slight abduction, flexion, and internal rotation. Usually, the humeral head is palpable anteriorly with a concomitant hollowing and visible deficiency posteriorly under the acromion. Patients may present after the dislocation has spontaneously reduced, in which case the diagnosis may not be evident. The mechanism of injury, history of a “dead arm” event, and reported information of a pop at the time of injury or pain that was relieved after a pop often represent key clues toward diagnosis.
Initial evaluation must include a thorough neurovascular examination. The more common neurapraxias can be ruled out with resistance testing of the posterior and middle deltoids and biceps. Pulses, warmth, and capillary refill should be compared with the unaffected extremity. Symmetry, however, does not necessarily exclude axillary artery injury. In the case of a spontaneously reduced dislocation, the patient will present with prominent guarding against combined abduction and external rotation.
Preliminary radiographic evaluation, usually consisting of a single oblique view, has often been completed prior to orthopaedic consultation. This view can adequately rule out fractures about the humeral head and neck that may prevent closed reduction. If additional injuries are not present, the surgeon should reduce the shoulder prior to ordering further radiographs. In the event radiographs cannot be taken at the time of presentation, such as in the event of an on-field injury, a gentle attempt at reduction is warranted.
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Management
Reduction
Several reduction maneuvers have been described in the literature. These include the hippocratic technique, the Stimson technique, and the Milch technique. The hippocratic technique involves using countertraction either with the surgeon's foot across the axillary folds against the chest wall or with a sheet pulling countertraction from across the patient's body in a cephalad direction by an assistant. Simultaneously, axial traction is applied to the affected shoulder. Internal and external rotation of the humeral head will help reduce the glenohumeral joint. The Stimson technique involves placing the patient prone with approximately 5 pounds of axial traction strapped at the wrist. With the Milch technique, an abduction and external rotation maneuver with concomitant gentle pressure on the humeral head with the thumb enables reduction on the supine patient. Perhaps more important than any particular method of reduction is to ensure that the patient is adequately relaxed and that adequate analgesia has been provided. Intravenous sedatives and anxiolytics are often helpful. Several authors have reported the successful use of intra-articular lidocaine for anesthetic. The glenohumeral joint can be easily penetrated posteriorly with an 18-gauge spinal needle. Aspiration of hemarthrosis verifies joint penetration. Fifteen to 20 mL of 1% lidocaine will provide adequate analgesia for the patient to cooperate with reduction efforts. Regardless of the maneuver used, successful reduction is confirmed with the restoration of normal humeroscapular relationships and smooth glenohumeral rotation. Patients generally experience dramatic pain relief after reduction. A thorough postreduction neurovascular exam must be performed.
Imaging
Having had adequate analgesia and sedation, the postreduction patient can readily tolerate a more thorough radiographic evaluation. Radiographs generally include a true glenohumeral anterior posterior (AP) in internal and external rotation and an axillary lateral. A true shoulder AP view is an x-ray view taken in the plane of the scapula (at approximately 30 to 40 degrees). Internal and external rotation views provide information regarding humeral head and tuberosity injuries. An axillary view confirms reduction of the glenohumeral joint and aids in the diagnosis of tuberosity fractures and Hill-Sachs lesions.
Various axillary views have been described. These include a true axillary view, which involves placing the arm in 70 to 90 degrees of abduction and then directing the x-ray beam superiorly through the axilla. A safer, less traumatic axillary technique involves elevating the arm in the plane of the scapula. This modification tends to prevent the humeral head from being placed into a vulnerable position. Other axillary images include the West Point view. In this technique, the patient is placed prone with the shoulders raised approximately 7 cm off the x-ray table. With the head and neck turned away, the x-ray beam is directed 25 degrees inferior from the horizontal and 25 degrees medial. The Velpeau view places the patient standing and leaning backward over the radiographic cassette. The x-ray beam is then directed vertically downward.
If a glenoid rim osseous defect is suspected, an apical oblique (Garth) view should be obtained. This radiographic technique places the scapula flat against the x-ray cassette similar to a true AP view. The x-ray beam is then directed in a 45-degree caudad direction.
Special radiographic techniques used to view humeral head defects in addition to the internal and external AP views include the tangential view, the Hill-Sachs view, and the Stryker-Notch view. The tangential and Hill-Sachs views involve AP x-rays in increasing degrees of internal rotation. The Stryker-Notch view is taken with the patient in the supine position with the affected hand placed on the head. The x-ray beam is then directed 10 degrees in a cephalad direction.
With any of these radiographic techniques, the surgeon may be required to assist in patient and extremity positioning. Obtaining high-quality postreduction radiographs, however, will provide critical information that will aid the orthopaedic surgeon in formulating the proper treatment algorithm for the patient.
If radiographic assessment demonstrates the possibility of an osseous Bankart lesion that involves >25% to 30% of the glenoid width, further evaluation with CT imaging with three-dimensional reconstructions is required. A recent study quantitatively demonstrated that CT imaging was superior to plain radiographs in assessing the size of a bony defect of the glenoid.
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Figure 33-1 MRI of subscapularis tear. |
Magnetic resonance imaging (MRI) has a limited but specific use in the evaluation of acute anterior glenohumeral dislocations. An MRI should be obtained when examination in the subacute postdislocation period yields evidence of a rotator cuff tear, particularly a subscapularis rupture (Fig. 33-1). A prospective study analyzing the accuracy of subacute MRI scans to identify labral tears in
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patients with first-time traumatic dislocations showed only a 70% correlation with arthroscopically confirmed labral tears. Another prospective study examining the accuracy of MRI arthrography to identify labral pathology in patients with traumatic anterior instability showed a specificity of 98% (Fig. 33-2).
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Figure 33-2 MRI of an anterior labral tear. |
Diagnostic sensitivity, however, was only 76%.
In the event of persistent deltoid or rotator cuff weakness without other clinical evidence of rotator cuff tear, electromyographic studies are indicated.
Postreduction Treatment
Immobilization
Generally, a simple sling has traditionally been used for postreduction immobilization. A sling with strap padding is often better tolerated than a shoulder immobilizer. Patients are encouraged to wear the sling during sleep to protect the shoulder during this initial period. In addition, patients are encouraged to remove the sling to exercise the elbow, wrist, and digits frequently. The duration of immobilization has typically been continued for ≤3 weeks, but absolutely no longer. Investigators have demonstrated that the length of immobilization has had no effect on the rates of recurrent dislocation. Alternatively, recent studies have suggested that the position of immobilization may affect the healing potential of labral lesions, thereby potentially affecting the redislocation rates for first-time dislocators. In a recent study, 19 traumatic anterior dislocations with Bankart tears were evaluated with MRI scans with the shoulders placed in both external and internal rotation. Findings included decreased separation and displacement of the labrum from the glenoid when the arm was in external rotation compared with when it was in internal rotation. A follow-up study of 40 patients with acute traumatic anterior dislocations was recently conducted. The patients were equally randomized to immobilization in sling and swathe in internal rotation or in a prefabricated splint in external rotation for 3 weeks. Results showed that none of the 20 patients immobilized in external rotation had a recurrent anterior dislocation at a mean 15-month follow-up. Whether immobilization in external rotation prevents long-term recurrence rates still remains to be seen.
Assessment
Repeat examination is critical during the subacute phase after dislocation. Re-evaluation should be during the first week of index dislocation. A prospective study of 538 first-time traumatic anterior dislocation patients showed a redislocation rate of 3.2% within the first week after original dislocation. Factors associated with increased risk for redislocation included neurologic deficit, associated large rotator cuff tears, and associated glenoid rim fractures with or without fractures of the greater tuberosity.
During physical examination, range of motion will likely demonstrate appreciable tightening of the shoulder, especially with external rotation in the unelevated position. External rotation that is greater than the unaffected side suggests a possible subscapularis rupture. Rotator cuff function should be assessed, particularly in patients older than 40 years of age as several studies have demonstrated the increased incidence of rotator cuff tears in this age group. Focused attention should be placed on examination of the subscapularis in all age groups. The lumbar lift-off test as described by Gerber has been shown to accurately predict subscapularis integrity and function. This test can usually be performed at the 3-week postdislocation assessment. An examination that reveals evidence of a rotator cuff tear mandates further evaluation with an MRI.
Nonoperative Therapy
The patient is started on a gentle supine self-passive stretching program at 3 weeks postdislocation. Exercises consist of gentle forward elevation and external rotation, with an external rotation limit of 40 degrees. An over-door pulley may be used for assistance in regaining forward elevation. Next, a scapular strengthening and postural program are used. Pendulum exercises are avoided as they promote poor scapular mechanics and increase anteroinferior translation of the humeral head. Formal, supervised therapy is instituted during the sixth week postdislocation. Passive stretching is used to correct any residual contractures. The mainstays of treatment at this stage are rotator cuff and scapular strengthening. Devices that promote normal humeroscapular rhythm are implemented: the body blade, pulleys, and upper body ergometers. Athletes generally can return to their sport midseason. Harnesses and prophylactic taping may provide proprioceptive feedback against extreme abduction and external rotation. At 12 weeks postdislocation, sport-specific exercises are started. Plyometrics for athletes and work hardening for heavy laborers may be necessary.
Early Surgical Intervention
The ability to prevent recurrent dislocation through exercise therapy is controversial. Studies involving cadets at military
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academies have demonstrated success rates of ≤75% after coordinated therapy programs for first-time dislocators. It is unclear whether such results could be reproduced in a more general population over a longer period of time. One study demonstrated only a 16% decrease in recurrence rates in patients treated with exercise therapy after traumatic subluxation.
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Figure 33-3 Algorithm for the management of first-time traumatic dislocations. |
The role of early surgical intervention for patients with initial dislocation has become more accepted with the advent of more refined arthroscopic techniques and instrumentation. Theoretically, these generally young patients have more clearly defined pathology and healthier tissue, making them good candidates for arthroscopic repair. In a prospective study comparing nonsurgical management and arthroscopic repair in West Point military cadets with initial dislocations, the recurrence rate was 80% in the nonsurgical group and 14% in the surgical group. In another study comparing randomized patients younger than 30 years of age with initial dislocations, those treated with immobilization and rehabilitation had a recurrence rate of 47% at 33 months compared with 15.9% in the group treated with arthroscopic Bankart repair. Although repair techniques vary among studies, most data suggest that arthroscopic Bankart repair is most advantageous if done after the initial dislocation, before the development of chronic pathologic changes associated with recurrent instability.
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Treatment Algorithm
The treatment of patients with first-time dislocations should be based on current science. The surgeon's algorithm must take into account the patient's age, activity level, and goals (Fig. 33-3). Several key points must be recognized in formulating a treatment plan. Tuberosity fractures displaced more than 5 mm require reduction and fixation. In young patients, concomitant arthroscopic Bankart repair should be strongly considered. Repair of traumatic subscapularis rupture should be performed as soon as possible to avoid musculotendinous retraction and scarring, regardless of age. Glenoid rim fractures equaling >20% of the intact glenoid width will often require bone augmentation in addition to a Bankart repair. For patients who lead an active lifestyle or are involved in a high-demand occupation and who have sustained a full-thickness rotator cuff tear from a dislocation, surgical treatment should involve both a rotator cuff repair and Bankart repair, if present. For the older patient with a large full-thickness rotator cuff tear and axillary neuropathy, rotator cuff repair should be considered if deltoid function does not return in 6 to 12 weeks postdislocation. For competitive athletes younger than 25 years of age, arthroscopic Bankart repair should be considered in the off season. For any patient younger than 25 years of age with a first-time dislocation, the benefits and risks of early arthroscopic Bankart repair should be discussed and offered as a reasonable option.
Open versus Arthroscopic Repair
Open Bankart repair has traditionally been advocated as the technique of choice for collision and contact athletes. A recent study demonstrated excellent long-term results in American football players treated with open Bankart repair. No patient had recurrent dislocations postoperatively, and only 2 of 58 had recurrent subluxation. In another study involving 194 patients with arthroscopically repaired Bankart lesions, 101 of whom were contact athletes, a recurrence rate of only 6.5% was present in patients without associated bone defects. In contrast, a recurrence rate of 87% was reported for those patients with marked bone loss.
Despite the advances in shoulder arthroscopy, there are a few absolute indications for open surgical repair in first-time dislocators. These include substantial humeral and/or glenoid bone loss, or irreparable rotator cuff deficiency, particularly those of the subscapularis. Relative contraindications to arthroscopic repair include humeral avulsions of the glenohumeral ligaments and capsular ruptures. In general, however, arthroscopic Bankart repair is probably indicated for first-time dislocations as there has never been any significant difference demonstrated in the surgical ease or outcome between early and late open Bankart repair.
Suggested Readings
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