Glenohumeral instability has a bimodal age distribution, with most affected patients younger than 40 years, but with a second peak in older patients. Glenohumeral dislocations in older patients often present with complex injury patterns, including rotator cuff tears, fractures, and neurovascular injuries. Glenohumeral instability in patients older than 40 years requires a different approach to treatment. An algorithmic approach aids the surgeon in the stepwise decision-making process necessary to treat this injury pattern.
Key points
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Shoulder instability in the older patient has a lower recurrence rate (0%–31%) compared with high recurrence rates in younger patients.
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Shoulder dislocations in older patients are more likely to be associated with fractures, neurovascular injuries, and rotator cuff tears.
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An older patient with inability to lift the arm after an anterior shoulder dislocation likely has a rotator cuff tear, as opposed to a nerve injury.
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Treatment of posterior shoulder instability in the older patient often presents as a chronic dislocation and depends more on length of time from injury and amount of humeral bone loss.
Incidence
The incidence of shoulder instability in older patients (age >60 years) has been estimated to be as high as 20% of acute anterior dislocations. The lowest rates of shoulder dislocations are in those 50 to 59 years old, with increasing incidence with increasing age after age 59 years. Women also had a higher incidence compared with men in the elderly, as opposed to a higher incidence in men in the younger population. Incidence in women 80 to 89 years of age is 38.8/100,000 person-years at risk.
Incidence
The incidence of shoulder instability in older patients (age >60 years) has been estimated to be as high as 20% of acute anterior dislocations. The lowest rates of shoulder dislocations are in those 50 to 59 years old, with increasing incidence with increasing age after age 59 years. Women also had a higher incidence compared with men in the elderly, as opposed to a higher incidence in men in the younger population. Incidence in women 80 to 89 years of age is 38.8/100,000 person-years at risk.
Recurrence
The low recurrence rate of instability in older patients is one of the biggest differences from shoulder instability in younger patients, which has been reported to be as high as 100%. Recurrence rates in various reports are listed here:
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Rowe J Bone Joint Surg Am 1956
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94% in ages younger than 20 years
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74% in ages 20 to 40 years
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14% in ages older than 40 years
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Simonet and colleagues Am J Sports Med 1984
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0% in 41 shoulder dislocations (>40 years old)
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Penvy and colleagues Arthroscopy 1998
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4% in 125 patients in ages older than 40 years
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Wenner Orthopedics 1985
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17% in ages older than 40 years
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Gumina and Postacchini J Bone Joint Surg Am 1997
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22% recurrence in ages older than 60 years
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50% of those only had 1 recurrent dislocation
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Rapariz and colleagues Int J Shoulder Surg 2010
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31% recurrence in ages older than 60 years
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Stayner and colleagues Orthop Clinic North Am 2000
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10.5% in ages older than 40 years
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Davy and Drew Injury 2002
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6% in age older than 40 years
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Mechanism of shoulder instability
An acute dislocation is usually the result of some traumatic event to the involved shoulder. The injury needs to impart enough energy to the glenohumeral joint to overcome either the soft tissue restraints or osseous restraints. The anterior soft tissue restraints generally include the anterior capsule, the anterior glenohumeral ligaments (specifically the anterior inferior glenohumeral ligament), the anterior labrum, and the subscapularis. The posterior soft tissue restraints to anterior instability generally include the superior and posterior rotator cuff. General teaching is that either the anterior or posterior supporting structures need to be disrupted for an anterior dislocation to occur.
Anterior Mechanism for Anterior Instability
The lesion most associated with anterior shoulder instability is the Bankart lesion. This is a tear of the labrum and capsuloligamentous structures off the anterior inferior glenoid. This is the most common finding in younger patients with shoulder instability as a result of the theory that the attachment site of the capsule and labrum to the glenoid is the weakest of the anterior elements in the younger patient.
Reeves evaluated 110 cadavers within 25 hours of death in regard to the strength of the different supporting structures of the anterior shoulder with relation to age. This investigator found that during the first 3 decades of life, the attachment of the labrum was weaker than the subscapularis tendon and its attachment as well as the anterior capsule. In older patients, the anterior capsule and subscapularis were weaker than the labral attachment site (which maintained a relatively constant strength throughout the remainder of life), and failure more commonly occurred with capsular rupture than labral avulsion from the labrum.
In addition, it is believed that because the labrum and capsuloligamentous structures are static restraints to the shoulder joint, their disruption more likely leads to recurrence. This belief provides 1 proposed theory behind the higher rate of recurrence in younger patients. Araghi and colleagues found that only 11 of 265 patients (4.1%) requiring open anterior stabilization for recurrent instability were older than 40 years. However, in the low percentage of older patients with recurrent instability, a high rate of anterior capsulolabral injury necessitating repair has been reported.
Posterior Mechanism for Anterior Instability
As humans age, the rotator cuff weakens and is more prone to tearing. So, in the older patient with preexisting degenerative weakening of the rotator cuff, it is more likely that the posterior structures fail rather than the anterior structures. Shin and colleagues reported on 67 patients older than 60 years with a primary shoulder dislocation, finding 33 rotator cuff tears (RCTs) and only 3 isolated Bankart lesions. Because the rotator cuff is a dynamic structure, this might be an explanation for the lower recurrence rate in the older patient after a dislocation.
Hsu and colleagues showed that in a cadaver model, RCTs could result in abnormal glenohumeral translations. Small tears resulted in anteroinferior translation, and larger tears resulted in more direct anterior translation. This abnormal translation has recently been shown to correct with posterior rotator cuff reconstruction using a latissimus transfer.
Pouliart and Gagey showed that the humeral head dislocates in the presence of less extensive capsuloligamentous lesions when rotator cuff lesions are present. Also, the passive stabilization provided by the rotator cuff appeared more easily disrupted when associated with ligamentous lesions on the humeral side than with lesions on the glenoid side. The investigators postulated that this situation may be because interdigitation of the cuff tendons with each other and with the capsule through the rotator cable is maintained with glenoid-sided lesions. It is also possible that the higher prevalence of preexisting rotator cuff disease in the older patient may lead to abnormal glenohumeral motion and predispose an older individual to shoulder instability with a low-energy trauma.
Associated injuries
RCT
Reported incidence after anterior shoulder dislocation ranges from 35% to 86% in patients aged 40 years or older. Rotator cuff pathology can range from small tears to massive posterosuperior tears to anterosuperior tears. Neviaser and Neviaser reported that all patients older than 40 years with recurrent anterior instability had a subscapularis tear and anterior capsule tear.
Anteroinferior Labral (eg, Bankart) Lesions
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Interpretation of labral tears seen radiographically in this age group is difficult because tears may be degenerative or preexisting before dislocation.
Humeral Fractures
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Large Hill-Sachs lesions: osteoporotic bone more at risk
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Two-part, 3-part, and 4-part fracture dislocations
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Head-split fractures
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Isolated greater tuberosity (GT) fracture
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Incidence increases exponentially with age, with an average age of 69.3 years
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Less risk of recurrence if fracture heals than without fracture, because the rotator cuff is typically not torn with GT fracture
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Glenoid Fractures
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Osseous Bankart lesions
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Complex glenoid fractures
Neurologic Injuries
Neurologic injuries are more common with shoulder dislocations in the elderly and are also more severe. Rates as high as 50% to 65% have been reported after dislocation in older patients. Toolanen and colleagues looked at patients older than 40 years using electromyography after an anterior shoulder dislocation and found that 36 of 55 cases had electromyographically verified axillary nerve or brachial plexus injury. Robinson and colleagues reported on 3633 shoulder dislocations and found that the most common neurologic injury after an anterior dislocation was an isolated axillary nerve injury. This neurologic injury occurs in a similar distribution to an isolated anterior dislocation (bimodal age distribution, sex, mechanism of injury). However, patients suffering from multiple nerve lesions or diffuse brachial plexus injuries were typically older than 60 years and more likely to be female.
The primary mechanism is likely stretching of the infraclavicular brachial plexus, causing neurapraxia. Literature on infraclavicular neurapraxia reports complete resolution in 4 to 6 months in 80% of cases. However, most of the patients examined were young. Toolanen and colleagues found that 14 of 27 patients older than 40 years with a moderate to total axillary nerve injury were still symptomatic at 3 years, as were 3 of the 6 patients with more diffuse plexus injuries. The nerve recovery in the older patient is likely not as reliable as in the younger patient.
Combined Neurologic Injury and RCT
The patient older than 40 years who cannot raise their arm after an anterior shoulder dislocation provides a diagnostic challenge. Older individuals are at a higher risk for nerve injury after a dislocation but also at a higher risk for a RCT. The management of these 2 entities is different, because an acute RCT might be better managed with early surgical repair. Therefore, it is detrimental to attribute a lack of shoulder function to a neurologic injury without confirming the integrity of the rotator cuff, because delay may make a massive tear more difficult or impossible to repair. In a study of 31 such patients with an average age of 57.5 years, 29 were believed to be unable to lift their arm secondary to an axillary nerve lesion. However, all were found to have RCTs, and only 4 were found to have an axillary nerve lesion with further testing. In addition, the presence of a neurologic injury does not rule out a rotator cuff lesion. Robinson and colleagues found many patients with combined injuries.
Vascular Injuries
The axillary artery in elderly patients is less elastic and more sclerotic and, therefore, is more prone to tearing. Most reported axillary artery injuries occur when chronic dislocations are reduced but can occur with acute dislocations. Calvet and Lacroix reported on the largest series of arterial injuries associated with shoulder instability, with 64 axillary artery ruptures occurring after closed reduction of 91 chronically dislocated shoulders. These investigators reported 50% mortality, with the remaining patients losing their upper extremity or having a functionless limb.
The third part of the axillary artery (lateral to the pectoralis minor) is most commonly injured, but the second part (behind the pectoralis minor) can also be injured with avulsion of the thoracoacromial trunk. The third part of the axillary artery is fairly fixed and tethered by the subscapular and circumflex humeral arteries. With abduction and external rotation, the artery becomes taut and the pectoralis minor may act as a fulcrum to injure the vessel when the shoulder is dislocated anteriorly.
The presentation of this injury has been described as having a pathognomonic triad, consisting of an anterior shoulder dislocation, an expanding axillary hematoma, and a diminished peripheral pulse. This injury is associated with a brachial plexus injury in 60% of cases, which can be a large determinate of functional outcome. The presence of signals in the distal vessels that can be noted with Doppler does not exclude an axillary artery injury, because those signals may be secondary to collateral blood flow, and if the clinical picture is consistent with an arterial injury, an angiographic study should be obtained. There is also some thought that in the presence of an axillary artery lesion and brachial plexus injury, the brachial plexus should be explored at the time of vascular repair to reconnect any transected nerves.
Acute Anterior Dislocation
Initial treatment
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Gentle closed reduction if diagnosed early
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Consider closed reduction under general anesthesia for:
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Dislocation more than a few days old
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Severe osteoporosis
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Elderly patients can often have humeral head fractures during dislocation, and therefore, reduction techniques need to be gentle. General anesthesia should be considered sooner than with a younger patient. It is also imperative to be aware of the presence of a nondisplaced surgical neck fracture before reduction, especially if there is a GT fracture, because the reduction technique may displace the fracture.
Thorough radiographic evaluation is critical. Radiographs should include at least a true scapular anteroposterior (AP) and an axillary view. Internal rotation, external rotation, and scapular Y views are often helpful for identifying and evaluating tuberosity fractures. In addition, signs of chronic RCTs such as undersurface acromial changes or proximal humeral head migration should be recognized, because these may help to determine the chronicity of a RCT if one is found radiographically.
Two-dimensional and especially three-dimensional computed tomography (CT) scans can be helpful for evaluation of osseous irregularities. A CT scan should be ordered for any of the following:
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Any radiographic evidence of glenoid fracture
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Any suspicion of head-split humeral fracture
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To adequately assess the size of any Hill-Sachs lesion
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Persistent (chronic) dislocation
Magnetic resonance imaging, ultrasonography, or CT arthrography should be used to evaluate the rotator cuff of any patient older than 40 years who presents with continued symptoms consistent with a RCT for 4 weeks after a dislocation (abduction weakness, external rotation weakness, positive provocative testing, positive testing for subscapularis weakness). This procedure should be carried out regardless of the presence or absence of a suspected neurologic injury.
Definitive treatment
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Nonoperative management is appropriate for:
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First-time dislocation
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No or nondisplaced fracture
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No or chronic appearing RCT with quick return of cuff function
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Subscapularis intact
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Stable arc after closed reduction
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Sling immobilization for 7 to 10 days, then begin range of motion exercises and proceed to strengthening as tolerated
Surgical Treatment
Instability in the elderly often results from a combination of diseases including: soft tissue injury, RCT, Bankart tear, capsular tear ( Fig. 1 ), glenoid fracture, and humeral fracture. Failure to address all of the disease surgically leads to a higher incidence of recurrence. Preoperative planning is critical, and deciding which combination of diseases to address leads to the best approach to use. For a posterosuperior RCT and Bankart repair, an arthroscopic technique is likely better. For a subscapularis avulsion and a Bankart repair with a Hill-Sachs lesion, an open anterior approach is likely more suitable, depending on the degree of subscapularis tear and amount of the bony deficiency.
