Shoulder and Elbow

Chronic Glenohumeral Dislocation: Anterior and Posterior

The Problem

Chronic glenohumeral dislocations represent a therapeutic challenge for the orthopaedic surgeon. Patients with a chronic glenohumeral dislocation often present with a complex combination of pathologic findings, all of which impact the treatment strategy and ultimate prognosis. These include injuries to the humeral head articular surface, the glenoid, the rotator cuff, and the capsulolabral structures. The direction of dislocation and the duration are also important considerations. Due to the diversity of presentation of patients with these injuries, a wide array of treatment options exist. A systematic approach to the evaluation of these patients is essential in order to develop the optimal treatment strategy that will address all relevant pathoanatomy and provide a high likelihood of a successful outcome.

Clinical Presentation

A systemic approach to the management of chronic glenohumeral dislocations requires a consistent definition of terms. A chronic dislocation is defined as one that is not recognized at the time of the acute injury, and thus one for which treatment is delayed. This broad definition has proven more useful than an arbitrary objective definition based on number of weeks or months since the dislocation occurred.

Of all reported chronic dislocations, approximately 40% are anterior, and 60% are posterior; however, this may not reflect the true incidence of these injuries. In the acute setting, anterior dislocations are far more common, while posterior dislocations account for only 4-5% of all cases. However, up to 80% of these cases may be missed on initial presentation, which may explain the increased incidence of posterior dislocations in the chronic setting.

Anterior dislocations most commonly result from traumatic injury with the shoulder in the abducted, externally rotated position. In contrast, although posterior dislocations can also occur following a fall, they often occur in association with electric shock or seizure, metabolic abnormality, or alcohol withdrawal. As a result of these mechanisms approximately 15% of patients present with bilateral posterior dislocations. Due to the higher energy nature of these injuries, chronic glenohumeral dislocations may present with an associated fracture of the greater or lesser tuberosity, surgical neck or articular surface. Other associated fractures may have occurred at the time of the acute injury, including fractures of the coracoid or acromion. Associated neurologic injury is far more common with anterior than posterior dislocations, and more common in the acute versus chronic setting. The axillary and suprascapular nerves are the most commonly involved. In general, however, these nerve injuries may have resolved by the time a patient with a chronic dislocation presents for evaluation.

A detailed history is a critical element of a comprehensive evaluation. The patient’s age, hand-dominance, occupation, and activity level should be documented. The history should include a discussion of the mechanism of injury. Recent history of trauma, seizure activity, or electric shock should be asked specifically. Timing of the injury is important in the development of an appropriate treatment plan. The patient may describe a previous incomplete evaluation of an earlier injury, perhaps with inadequate radiographs. Often, the patient may have been treated for an alternative diagnosis, including bursitis, tendonitis, or frozen shoulder. These patients may then have been referred to physical therapy, with the diagnosis of a chronic dislocation discovered only after they plateau with regard to recovery of their range of motion.

Inspection of a patient with a chronic dislocation reveals a characteristic asymmetry depending on the direction of dislocation. Chronic anterior dislocations demonstrate an anterior fullness, flattening of the posterolateral aspect of the shoulder, prominence of the posterolateral acromion, and a void overlying the glenoid vault. The humeral head can be palpated anteriorly. In contrast, posterior dislocations demonstrate a posterior fullness and flattening of the anterolateral shoulder, with prominence of the anterolateral acromion and coracoid. The humeral head can be palpated posteriorly. In chronic dislocations, this asymmetry is often exaggerated due to deltoid atrophy, which may be accentuated in the context of a concomitant axillary neuropraxia.

Patients with chronic glenohumeral dislocations often present with mild discomfort. Over time, the degree of pain due to the dislocation improves. In addition, range of motion is often not as restricted as expected, due in part to enlargement of the associated humeral head impression fracture, and compensation of the scapulothoracic component of shoulder motion. Patients with chronic anterior dislocations present with some degree of restricted forward elevation and abduction, as well as internal rotation. In contrast, external rotation is limited in patients with a posterior dislocation. Though strength testing can be challenging, one should assess the rotator cuff and deltoid to identify an associated rotator cuff or neurologic injury. To that end, the examination of a patient with a chronic dislocation must include a detailed neurologic evaluation. Similarly, a careful vascular assessment should be performed to identify an associated vascular injury, although these injuries are rare.

Diagnostic Imaging

The fact that chronic glenohumeral dislocations, most of them posterior, are missed at the time of the acute injury underscores the importance of a comprehensive radiographic examination. A scapular anteroposterior view, scapular lateral view, and axillary view should all be included in a complete trauma series. Together, these views provide invaluable information regarding the position of the humeral head relative to the glenoid. The humeral head should be examined for the presence and size of an impression fracture. In an anterior dislocation, this impression fracture, or Hill-Sachs lesion, will be located at the posterolateral humeral head. One can best appreciate glenoid bone loss on the axillary view. Bone fragments associated with a glenoid rim fracture may be present. Attritional bone loss of the glenoid is less common in chronic glenohumeral dislocations, as the soft cancellous bone of the humeral head often yields to the stronger cortical bone of the glenoid rim. In dislocations that have been present for at least several weeks, one might appreciate reactive bone formation along the anterior or posterior portion of the glenoic neck depending on the direction of dislocation.

Findings of a posterior glenohumeral dislocation on the scapular anteroposterior view can be subtle. The humeral head often overlaps the glenoid, even on a perfect anteroposterior view in the scapular plane. Further, an impression fracture might manifest as an area of density in the humeral head (Figure 1). Further, Moloney’s line, the analogy to Shenton’s line of the hip, is often disrupted in a posterior dislocation. Similar to anterior dislocations, an axillary view is instrumental in confirming the direction of dislocation, as well as in identifying and quantifying a reverse Hill-Sachs lesion, an impression fracture of the anteromedial humeral head that develops in association with posterior dislocation (Figure 2).

Figure 1.

In this 59-year old patient with a posterior dislocation, the humeral head and glenoid overlap, even on an AP radiograph in the scapular plane. In this case, Moloney�s line is preserved, but is often disrupted in posterior dislocations.

Figure 2.

In the same patient, axial imaging, in the form of an axillary radiograph or CT scan, confirms the posterior dislocation, and allows quantification of the humeral head impression fracture. Reactive bone formation can be appreciated along the posterior scapular neck.

Computed tomography (CT) is a powerful tool in the evaluation of chronic glenohumeral dislocations (Figure 3). The degree of bone loss both on the humeral and glenoid sides can be quantified. The axial images can be used to determine the percentage of humeral head articular surface affected by an impression fracture. The same calculation can be performed using an axillary radiograph, if a CT scan is unavailable (Figure 4). These same images can also be used to determine the percentage of glenoid articular surface affected by fracture or attritional loss. Three-dimensional reconstructions of these images can provide an enhanced understanding of humeral head and glenoid bone loss. Magnetic resonance imaging is not routinely required in the evaluation of these injuries, though this study can be obtained if there is concern for the presence of associated soft tissue injury, including rotator cuff tears.

Figure 3.

An axial CT image allows for the quantification of the size of the humeral head impression defect as a percentage of the overall humeral head articular surface.

Figure 4.

An axillary radiograph can also be used to calculate the relative size of the humeral head impression defect.

If the physical examination suggests a neurologic injury, electrodiagnostic studies should be obtained. These studies will reveal abnormalities at 3 to 4 weeks after the injury. It is advised to recognize and document this injury before proceeding with definitive treatment. Vascular injury is rare in the setting of a chronic glenohumeral dislocation. However, when suspected, potential vascular compromise should be evaluated by a vascular specialist with appropriate diagnostic studies.

Management

A wide array of treatment alternatives exists for the management of patients with chronic glenohumeral dislocations. A systematic approach to the evaluation of these patients is required to develop the optimal treatment strategy. First and foremost, the management strategy should be individualized, based on the patient’s age, activity level, occupation, and comorbidities. Other critical factors to consider include the functional limitations caused by the dislocation, the duration of dislocation, the presence and size of the humeral head impression fracture, the presence and degree of glenoid bone loss and the status of the articular cartilage.

Nonoperative Management

While limited, there is a role for nonoperative management in the treatment of patients with chronic glenohumeral dislocations. Patients with limited functional demands, who experience minimal discomfort, and who are able to perform most activities of daily living with minimal difficulty, can be treated nonoperatively. Similarly, patients with significant comorbidities, for whom operative intervention presents significant risks that outweigh the potential benefit, are perhaps better treated nonoperatively. Lastly, patients who demonstrate an inability to comply with a careful and judicious postoperative rehabilitation program are likely ill-suited for operative intervention.

Closed Reduction

The duration of dislocation represents the most important factor in determining the appropriateness of closed reduction. There is some disagreement regarding the threshold for this determination. In general, patients who present with a dislocation of less than 4 weeks' duration may be appropriate for this approach. The radiographs can be examined for an indication of the chronicity of the injury, including the size of the impression fracture, or the degree of reactive bone formation along the glenoid neck. The presence of a large impression fracture suggests the likelihood of failure of closed reduction.

Varied techniques have been described to guide closed reduction of anterior and posterior dislocations. Closed reduction maneuvers should be performed under anesthesia - either general or regional - to ensure complete muscular relaxation and increase the likelihood of a successful attempt. Generally speaking, the humeral head impression fracture should first be unlocked, or disengaged from the glenoid rim, followed by a maneuver to reduce the humeral head. Careful, gentle manipulation should be performed to avoid propagating the impression fracture, thus creating a displaced iatrogenic anatomic neck fracture. An examination should be performed after reduction, to assess the stability of the reduction. If persistently unstable, operative intervention is indicated.

Indications for Surgery

Except for the rare instances where a chronic glenohumeral dislocation can be closed reduced, most patients require operative intervention.

Surgical Technique

Anterior Dislocation

Open Reduction

Most chronic glenohumeral dislocations require open reduction. Indications for open reduction include inability to perform a successful closed reduction due to the duration of dislocation, and those for which closed reduction is unlikely to confer sufficient stability due in part to the presence of a large humeral head impression fracture or glenoid bone loss. The approach will depend on the need for concomitant procedures to address associated injuries. Chronic anterior dislocations can be approached via a deltopectoral approach. The deltoid and cephalic vein are retracted medially, and the pectoralis major muscle laterally. The muscles of the conjoined tendon are identified and retracted medially. In chronic injuries, these muscles are often displaced and adherent to the deeper tissues. The lesser tuberosity and bicipital groove are identified. A subscapularis tenotomy is performed 1cm from its insertion to allow later repair. The anteroinferior capsule is released from the proximal humerus while protecting the axillary nerve. Once the glenohumeral joint is exposed, fibrous tissue is excised. The proximal humerus is gently manipulated to disengage the impression fracture, through internal rotation and lateral traction. After successful reduction, a humeral head retractor is inserted to allow examination of the glenoid articular cartilage. Care should be exercised when levering or retracting the humeral head, due to softening of the humeral head articular cartilage and subchondral bone in the chronic setting. Finally, stability is assessed to determine the need for additional procedures (Figure 5. Figure 6, Figure 7, Figure 8).

Figure 5.

An anteroposterior radiograph in a 39-year old patient reveals a chronic anterior dislocation.

Figure 6.

A scapular lateral radiograph in the same patient reveals a chronic anterior dislocation.

Figure 7.

An axillary radiograph in the same patient reveals a chronic anterior dislocation.

Figure 8.

This patient was treated with open reduction, and capsulolabral repair.

Humeral Head Defects

The ideal procedure for the treatment of humeral head defects depends on the duration of dislocation, and the size of the impression fracture. For dislocations that have been present for less than 3 to 4 weeks, with impression fractures that represent less than twenty 20 – 25% of the humeral head articular surface, in younger patients with good quality bone, disimpaction and bone grafting can be performed. A 1cm cortical window is created in the proximal humerus to allow access to the impression defect. A bone tamp is utilized to disimpact the cancellous and subchondral bone 1 to 2mm beyond the surrounding subchondral bone to allow for postoperative settling. Bone allograft or osteoconductive bone graft substitute can be used to fill the resultant defect. Cancellous screws can be placed perpendicular to the defect to provide support to the grafted area. This is frequently needed to provide support to the grafted area.

Transfer of the infraspinatus tendon, with or without the greater tuberosity, can be appropriate for a humeral head defect accounting for less than 40% of the total articular surface. This procedure requires a separate posterior approach in addition to the anterior deltopectoral approach, and is therefore less desirable. A posterior axillary incision is utilized. The deltoid can be split to expose the underlying infraspinatus tendon insertion. For defects of 20 – 25%, an infraspinatus tendon transfer alone can be performed. The tendon is elevated directly off of its insertion on the greater tuberosity. The tendon is docked into the defect with horizontal mattress sutures, which are then tied over a bone bridge on the lateral cortex of the proximal humerus. Suture anchors provide an alternative method of fixation. For large defects of less than 40%, the greater tuberosity can be osteotomized to the base of the defect, transferred medially into the defect, and secured with two cancellous screws. However, there is a role for allograft reconstruction in this setting to avoid further disruption to the proximal humeral anatomy that results from greater tuberosity transfer. Another advantage of allograft reconstruction is that it can be performed from the same anterior approach and avoids the need for a posterior revision.

For humeral head defects of greater than 40% in younger patients, allograft reconstruction represents a viable treatment alternative, in order to avoid or delay prosthetic replacement. A CT scan is required to precisely quantify the size and dimensions of the defect, so that a size-matched, fresh-frozen humeral head allograft can be obtained. Once the glenohumeral joint is reduced, the remaining articular surface must be examined to assure the absence of extensive degenerative joint disease. The humeral head impression defect is also examined. An oscillating saw is used to create a wedge and to expose cancellous bone. A matching wedge is harvested from the allograft, approximately 2mm wider. The allograft is impacted into the defect and secured with cancellous screws placed in a retrograde fashion, or countersunk beneath the articular surface.

Prosthetic replacement is indicated for older patients with humeral head defects of more than 40% of the articular surface. The duration of dislocation is also an important factor in the decision to proceed with arthroplasty. In duration of dislocation beyond 6 months, either the humeral head articular cartilage has often undergone sufficient degeneration, or the subchondral and metaphyseal bone has softened enough to necessitate replacement. For anterior dislocations, it is often helpful to perform the anatomic neck osteotomy during the exposure to facilitate soft-tissue releases. To enhance stability of the construct, increased retroversion by 10 – 15 degrees is often incorporated, but this should be considered carefully (Figure 9, Figure 10, Figure 11, Figure 12, Figure 13). The glenoid should be carefully examined during prosthetic replacement for chronic anterior dislocation, to determine if anterior bone loss will necessitate bone graft reconstruction or if articular cartilage loss necessitates resurfacing with total shoulder arthroplasty. Following prosthetic replacement, the extremity is immobilized in a sling. Passive motion is initiated immediately, including external rotation based on intraoperative assessment of the subscapularis repair. The sling is discontinued after 6 weeks, and active motion is then introduced followed by strengthening program.

Figure 9.

This anteroposterior radiograph reveals a chronic anterior glenohumeral dislocation with a significant humeral head impression fracture in a 69-year old patient with a history of trauma 6 months prior.

Figure 10.

This axillary view in the same patient demonstrates a chronic anterior glenohumeral dislocation with a significant humeral head impression fracture.

Figure 11.

Magnetic resonance imaging in the same patient demonstrates a chronic anterior glenohumeral dislocation with a significant humeral head impression fracture.

Figure 12.

This patient was treated with hemiarthroplasty.

Figure 13.

A postoperative axillary radiograph confirms concentric reduction of the glenohumeral joint.

Posterior Dislocation

Open Reduction

The sequence of steps for the open reduction of chronic posterior dislocations will depend on the nature of associated procedures to be performed. A subscapularis tenotomy 1cm from its insertion is performed if allograft reconstruction or prosthetic replacement is necessary. The subscapularis is elevated off of the proximal humerus if a subscapularis transfer will be performed. If a lesser tuberosity transfer will be performed, the lesser tuberosity is osteotomized beginning at the bicipital groove toward the base of the impression defect. Once the glenohumeral joint is exposed, fibrous tissue is excised. A gentle reduction maneuver is then performed to disengage the impression defect from the glenoid rim. A flat retractor can be used to gently lever the humeral head into a reduced position, taking care not to further injure the soft bone of the humeral head. The glenoid and humeral head articular surfaces, as well as the impression defect, are carefully examined. Glenohumeral joint stability is then assessed. If sufficiently stable, which may be the situation with small humeral head defects of 10-15%, the procedure is concluded, and the patient follows a postoperative rehabilitation program. Otherwise, additional procedures to address the relevant pathology are pursued. Depending on the surgical plan, a posterior approach may be necessary if significant glenoid fracture or bone loss requires attention.

Humeral Head Defects

As for anterior dislocations, the duration of dislocation and the size of the impression fracture will primarily determine the treatment strategy for humeral head defects. Disimpaction and bone grafting can be performed for injuries less than 3-4 weeks old, and an impression fracture less than 20 – 25% of the articular surface. Older age is a relative contraindication to this procedure, due to osteopenia or osteoporosis of the proximal humerus metaphyseal bone. In addition, the remainder of the articular cartilage must be intact without significant degenerative changes. With the shoulder internally rotated, a cortical window is created using an osteotome, and the articular surface is disimpacted using a bone tamp to achieve an overreduction of 1 to 2mm to account for postoperative settling. The resultant metaphyseal void is packed with cancellous bone allograft or bone graft substitute. Cancellous screws can be placed perpendicular to the defect to provide support to the grafted area.

Transfer of the subscapularis tendon, with or without the lesser tuberosity, can be appropriate for a humeral head defect accounting for less than 40% of the total articular surface. For defects of 20 – 25%, a supraspinatus tendon transfer alone, the McLaughlin procedure, can be performed (Figure 14, Figure 15, Figure 16, Figure 17, Figure 18). The tendon is elevated directly off of its insertion on the lesser tuberosity. The tendon is docked into the defect with horizontal mattress sutures, which are then tied over a bone bridge. Suture anchors provide an alternative method of fixation. For larger defects of less than 40%, the lesser tuberosity can be osteotomized to the base of the defect, translated medially into the defect, and secured with two cancellous screws (Figure 19, Figure 20, Figure 21, Figure 22, Figure 23). The medial wall of the lesser tuberosity should be preserved to prevent iatrogenic biceps instability. Although subscapularis transfer alone can be utilized for smaller defects, we prefer a lesser tuberosity transfer in these situations as well because it fills the defect and provides bony continuity with the articular margin.

Figure 14.

An anteroposterior radiograph in a 72-year old patient with a history of posterior dislocation suggests the presence of a reverse Hill-Sachs lesion.

Figure 15.

Intraoperative examination of the defect confirms that it accounted for less than 25% of the humeral head articular surface.

Figure 16.

The subscapularis is tagged, mobilized, and transferred into the defect.

Figure 17.

The subscapularis is transferred into the defect, and the sutures are tied over a bone bridge.

Figure 18.

A postoperative anteroposterior radiographs demonstrates elimination of glenohumeral overlap.

Figure 19.

An anteroposterior radiograph in a 47-year old patient with a history of posterior dislocation due to electric shock 1 month prior.

Figure 20.

An axillary radiograph in the same patient demonstrates the presence of a large reverse Hill-Sachs lesion.

Figure 21.

A lesser tuberosity osteotomy was performed with a microsagittal saw.

Figure 22.

The lesser tuberosity was transferred into the defect, and fixed with two partially-threaded, cancellous screws with washers.

Figure 23.

Postoperative CT scan demonstrates the lesser tuberosity transfer with concentric reduction of the glenohumeral joint.

Allograft reconstruction represents a viable treatment option for young patients with a humeral head defect of greater than 40%, in whom prosthetic replacement is less desirable (Figure 24, Figure 25, Figure 26, Figure 27, Figure 28, Figure 29, Figure 30, Figure 31, Figure 32). These patients should have excellent bone quality, with preserved articular cartilage on the remainder of the humeral head. A CT scan is required to precisely quantify the size and dimensions of the defect, so that a size-matched, fresh-frozen humeral head allograft can be obtained. An oscillating saw is used to create a wedge and to expose cancellous bone. A matching wedge is harvested from the allograft, approximately 2mm wider. The allograft is impacted into the defect and secured with cancellous screws placed in a retrograde fashion, or countersunk beneath the articular surface.

Figure 24.

An anteroposterior radiograph in a 55-year old patient with a history of seizure disorder demonstrates a chronic posterior dislocation.

Figure 25.

A scapular lateral radiograph is the same patient demonstrates a chronic posterior dislocation.

Figure 26.

An axillary radiograph in the same patient demonstrates a chronic posterior dislocation with involvement of at least 50% of the humeral head articular surface.

Figure 27.

An axial CT image of the same patient demonstrates a chronic posterior dislocation with involvement of at least 50% of the humeral head articular surface.

Figure 28.

Intraoperative examination of the humeral head confirms involvement of at least 50% of the articular surface.

Figure 29.

This patient was managed with size-matched humeral head allograft transplantation.

Figure 30.

A wedge of humeral head allograft was harvested to correspond to the humeral head defect.

Figure 31.

The humeral head allograft fixed with countersunk partially-threaded cancellous screws.

Figure 32.

A postoperative axillary radiograph in the same patient.

Older patients with humeral head defects of more than 40% can be effectively treated with prosthetic replacement (Figure 33, Figure 34, Figure 35, Figure 36). The duration of dislocation is also an important factor in the decision to proceed with arthroplasty. For duration of dislocation beyond 6 months, either the humeral head articular cartilage has often undergone sufficient degeneration, or the subchondral and metaphyseal bone has softened enough to necessitate replacement. The anatomic neck osteotomy is typically performed after reduction of the glenohumeral joint. To enhance stability of the construct, decreased retroversion by 10 – 15 degrees can be incorporated if necessary. The glenoid should be carefully examined to determine whether total shoulder arthroplasty is required. In the case of posterior capsular redundancy, or posterior instability of the construct during trialing, a posterior capsulorrhaphy can be performed from inside the glenohumeral joint at the time of arthroplasty to enhance stability.

Figure 33.

An anteroposterior radiograph in a 59-year old patient with a posterior dislocation of 4 months duration.

Figure 34.

An axial CT image in the same patient demonstrates involvement of at least 50% of the humeral head articular surface.

Figure 35.

 This patient was treated with hemiarthroplasty.

Figure 36.

A postoperative axillary radiograph in the same patient.

Glenoid Defects

Careful attention must be paid to the status of the glenoid to assure success of operative intervention. Although this is much less common than humeral head bone loss, if preoperative or intraoperative evaluation reveals significant glenoid bone loss that compromises glenohumeral joint stability, reconstruction with bone graft should be considered. Extensive research has been performed to determine the threshold amount of glenoid bone loss that leads to persistent instability. In general, glenohumeral joint stability is often compromised when bone loss accounts for approximately 20 – 30% of the anterior to posterior diameter. Three sources for bone graft are available to address this pathology: coracoid autograft, iliac crest autograft, or allograft. The Latarjet procedure refers to the use of coracoid autograft, with the attached conjoined tendon, which acts not only to increase the surface area of the articular surface, but also as a dynamic sling in the abducted, externally rotated position. The graft is decorticated along the surface to be fixed to the glenoid to optimize healing. Proud positioning of the graft relative to the articular surface must be avoided to prevent postoperative humeral head chondrosis. The graft is fixed with two 4.5mm malleolar screws. Extra-articular fixation of the graft with capsulolabral repair can further protect the humeral head articular cartilage from the graft, though concern exists regarding increased nonunion with the extra-capsular technique. The coracoacromial stump can be used to reinforce the capsular repair. Debate exists regarding fixation of the osteotomized surface of the graft directly to the glenoid - i.e. an intra-capsular placement - to increase the surface area of the graft.

Iliac crest autograft can also be used to address glenoid bone loss. The concave surface of the graft should be oriented in line with the glenoid articular surface. As with the coracoid, iliac crest graft can be placed intra-articularly or extra-articularly. The latter technique allows for more anatomic repair of the capsule, and theoretically protects the humeral head articular cartilage, but may increase the risk of nonunion. Various allografts have been described for the treatment of glenoid bone loss in the context of chronic glenohumeral dislocation. Distal tibia allograft has been described, with the advantage of a similar radius of curvature to the glenoid articular surface. With allograft, there is a concern for lack of incorporation, resorption, and hardware complications.

In the case of prosthetic replacement for significant humeral head defects or articular cartilage degeneration in treatment of chronic anterior and posterior dislocation, the glenoid articular surface must be carefully assessed not only for bone loss, but also for degeneration. In the case of significant glenoid chondrosis, total shoulder arthroplasty should be considered. Glenoid resurfacing should be considered in conjunction with humeral head replacement only in the appropriate patient. There must be sufficient subchondral bone to support the implant. In the presence of significant bone loss, adjunctive bone grafting, or the use of a step-cut glenoid implant, can be considered. However, in these situations the use of reverse shoulder arthroplasty should be considered if patient age and activity level are consistent with this procedure. A detailed discussion of glenoid implants is beyond the scope of this text. While version of the humeral head implant can be modified slightly to enhance stability of the construct, the glenoid component should always be implanted with the goal of restoring native glenoid version while preserving bone and optimizing fixation.

Pearls and Pitfalls of Technique

A complete radiographic examination consisting of anteroposterior, scapular lateral, and axillary views will assure prompt recognition of a chronic glenohumeral dislocation.

Reduction of a chronic glenohumeral dislocation requires careful, gentle manipulation to avoid propagating the impression fracture, thus creating a displaced iatrogenic anatomic neck fracture. Careful manipulation of the humeral head is also required to avoid further damage to the softened articular cartilage and subchondral bone.

For small humeral head defects associated with chronic posterior dislocation, the modified McLaughlin procedure, consisting of transfer not only of the subscapularis tendon, but also of the osteotomized lesser tuberosity, can be performed to achieve more reliable bone-to-bone healing.

When performing humeral head allograft reconstruction, the graft is cut 2mm larger than the recipient site to allow for press fit in addition to screw fixation.

When performing humeral head replacement for chronic anterior dislocation, performing the humeral head resection during the approach can facilitate capsular releases.

During insertion of a humeral head replacement for chronic anterior dislocation, version can be adjusted to enhance stability by increasing retroversion of the implant. Conversely, for posterior dislocations, retroversion of the implant can be decreased to enhance stability if necessary.

Glenoid bone loss and articular cartilage damage must be recognized and treated with either bone graft or resurfacing to optimize the outcome following operative intervention for chronic glenohumeral dislocation.

Potential Complications

The treatment of chronic glenohumeral dislocations represents a therapeutic challenge. A common concern following treatment of this condition is recurrent dislocation. This may result from inadequate capsular releases, or failure to adequately recognize and address bone loss associated with this injury. Iatrogenic nerve injury may occur following treatment of a chronic glenohumeral dislocation. The most commonly injured nerves include the musculocutaneous and axillary nerves. It is important to recognize that the muscles of the conjoined tendon are often displaced and scarred laterally in these patients. Failure to recognize this may result in injury to the musculocutaneous nerve during the approach. Similarly, the axillary nerve should be identified and protected, particularly during capsular release and glenoid exposure. Stiffness may occur in these patients, particularly following tendon or lesser tuberosity transfer.

Post–operative Rehabilitation

The appropriate postoperative rehabilitation protocol will depend upon the nature of the procedure performed. Following open or closed reduction alone of a chronic dislocation, if stability is determined to be acceptable, the patient should be immobilized for 3 - 4 weeks before initiating range of motion exercise. A period of immobilization will decrease the risk of re-dislocation even if the construct appears to be stable. For chronic anterior dislocations, a standard sling is used.

For chronic posterior dislocations, a gunslinger type orthosis is utilized to maintain the arm in 10 degrees of extension, 15 - 20 degrees if abduction and external rotation of zero to 20 degrees. Following immobilization, physical therapy initially consists of active and active-assisted range of motion, and proceeds to isometric strengthening, and then to resistive exercise by 12 weeks.

After disimpaction of humeral head defects for chronic anterior dislocation, the extremity is placed in a sling for 6 weeks. The patient begins passive range of motion immediately, but motion is restricted to minimize load across the affected area of the articular surface. The sling is discontinued after 6 weeks, and active range of motion is initiated.

For both infraspinatus and greater tuberosity transfer procedures, the extremity is immobilized in a sling for 6 weeks. External rotation is limited, as is combined external rotation and abduction. After 6 weeks, the sling is discontinued, and active range of motion is progressed.

Following arthroplasty for chronic anterior dislocation, the extremity is immobilized in a sling. Passive motion is initiated immediately, including external rotation based on intraoperative assessment of the subscapularis repair. The sling is discontinued after 6 weeks, and active motion is then introduced followed by a progressive strengthening program.

Following humeral head disimpaction, subscapularis transfer, or lesser tuberosity transfer for posterior dislocation, the patient is placed in an orthosis postoperatively, with the shoulder in 15 - 20 degrees of abduction, 10 - 20 degrees of extension, and 10 degrees of external rotation. Passive external rotation and abduction are initiated immediately. After 4 - 6 weeks, the orthosis is replaced with a sling, which is used for an additional 2 weeks. Active motion is introduced at 6 weeks followed by progressive stretching and strengthening.

After prosthetic replacement for chronic posterior dislocation, if a posterior capsular plication is performed, the patient is immobilized postoperatively in an orthosis in neutral rotation. If the construct is stable a basic sling can be used. Passive motion is initiated immediately, including external rotation based on intraoperative assessment of the subscapularis repair. If posterior capsulorrhaphy is performed, composite adduction and internal rotation is avoided. At 6 weeks, the sling or orthosis is discontinued, and active range of motion is initiated, followed by strengthening.

Outcomes/Evidence in the Literature

Wooten, C, Klika, B, Schleck, CD, Harmsen, WS, Sperling, JW, Cofiel, RH. "Anatomic shoulder arthroplasty as treatment for locked posterior dislocation of the shoulder". J Bone Joint Surg Am. vol. 96. 2014. pp. e19.

(Thirty-two patients who had undergone arthroplasty for chronic posterior glenohumeral dislocation were followed for a minimum of 2 years. Eighteen patients were treated with hemiarthroplasty, and 14 with total shoulder arthroplasty. Overall, pain scores and external rotation improved on average. Nineteen patients demonstrated excellent or satisfactory results, three patients experienced recurrent instability, and nine patients underwent reoperation.)

Rowe, CR, Zarins, B. "Chronic unreduced dislocations of the shoulder". J Bone Joint Surg Am. vol. 64. 1982. pp. 494-505.

(Twenty-four shoulders with an anterior or posterior dislocation untreated for at least 3 weeks were treated and followed for an average of 4.5 years. Eight shoulders were managed conservatively without formal treatment, with a score of 56/100. Seven shoulders treated with open reduction demonstrated an average outcome score of 79/100. Three patients were treated with arthroplasty, one of whom received a total shoulder arthroplasty, with an average score of 75/100. Finally, four patients were treated with resection arthroplasty, with an average score of 74/100.)

McLaughlin. "Posterior Dislocation of the Shoulder". JBJS (Am). vol. 34-A.

(Twenty-two patients with posterior glenohumeral dislocation were identified. The mechanism, signs and symptoms of these injuries were illustrated. Six patients with acute injuries were managed with closed means. Three of nine patients with chronic dislocations were treated with subscapularis transfer. Operative findings and technique are described in detail. Three others were treated operatively with an alternative procedure. Three of seven patients with recurrent dislocations were treated with subscapularis transfer. The author underscores the importance of early recognition and appropriate treatment of chronic or recurrent glenohumeral dislocation.)

Diklic, ID, Ganic, ZD, Blagojevic, ZD, Nho, SJ, Romeo, AA. "Treatment of locked chronic posterior dislocation of the shoulder by reconstruction of the defect in the humeral head with an allograft". J Bone Joint Surg Br. vol. 92. 2010. pp. 71-6.

(Thirteen patients with chronic posterior glenohumeral dislocation were treated with reconstruction of a humeral head defect between 25% and 50% of the articular surface with femoral head allograft. After mean follow-up of 54 months, no patient demonstrated persistent instability, nine patients were able to perform activities of daily living without pain or restriction, and the Constant-Murley score averaged 86.8.)

Martinez, AA, Navarro, E, Iglesias, D, Domingo, J, Calvo, A, Carbonel, I. "Long-term follow-up of allograft reconstruction of segmental defects of the humeral head associated with posterior dislocation of the shoulder". Injury. vol. 44. 2013. pp. 488-91.

(Six patients with humeral head defects measuring 40% of the articular surface due to chronic posterior dislocation of the shoulder were treated with humeral head allograft reconstruction. All patients returned to their occupation 4 months postoperatively. Half of the patients had no complaints of pain, instability, or mechanical symptoms. Half of patients developed either collapse of the allograft or eventual osteoarthritis, which eventually required conversion arthroplasty.)

Sperling, JW, Pring, M, Antuna, SA, Cofield, RH. "Shoulder arthroplasty for locked posterior dislocation of the shoulder". J Shoulder Elbow Surg. vol. 13. 2004. pp. 522-7.

(Twelve patients with a locked posterior dislocation treated with shoulder arthroplasty were followed for an average of 9 years. Significant pain relief and improved external rotation were observed. Seven patients demonstrated an excellent or satisfactory result. Two patients developed postoperative posterior instability, and one experienced component loosening, all of whom required revision surgery.)

Goga, IE. "Chronic shoulder dislocations". J Shoulder Elbow Surg. vol. 12. 2003. pp. 446-50.

(This manuscript summarizes the author’s experience in the treatment of thirty-two patients with chronic glenohumeral dislocations, 31 of which were anterior. Ten patients were left unreduced. Closed reduction was successful only in one patient. Twenty-one patients required open reduction, and ten of these underwent coracoid transfer and temporary acromiohumeral wire placement. These cases demonstrated improved outcomes compared to the patients managed conservatively.)

Checchia, SL, Santos, PD, Miyazaki, AN. "Surgical treatment of acute and chronic posterior fracture-dislocation of the shoulder". J Shoulder Elbow Surg. vol. 7. 1998. pp. 53-65.

(Sixty-six patients with 73 posterior glenohumeral fracture-dislocations were followed for an average of 32.7 months. Thirty-six patients were treated in the chronic phase. Treatment consisted of closed reduction and immobilization, open reduction and internal fixation, McLaughlin procedure, hemiarthroplasty, total shoulder arthroplasty, resection arthroplasty, or arthrodesis. Treatment within 2 years of injury was correlated with good to excellent results, whereas treatment beyond 2 years was associated with a fair outcome.)

Cheng, SL, Mackay, MB, Richards, RR. "Treatment of locked posterior fracture-dislocations of the shoulder by total shoulder arthroplasty". J Shoulder Elbow Surg. vol. 6. 1997. pp. 11-7.

(Seven shoulders in five patients with locked posterior dislocations were treated with total shoulder arthroplasty. The ASES score improved from 20.1 to 55.6. Pain, motion, and function were all improved postoperatively. Patients continued to experience difficulty with activities above shoulder level and with heavy lifting. The authors describe the utility of a secondary posterior incision to extricate the humeral head.)

Flatow, EL, Miller, SR, Neer, CS. "Chronic anterior dislocation of the shoulder". J Shoulder Elbow Surg. vol. 2. 1993. pp. 2-10.

(Seventeen patients were treated for a chronic anterior shoulder dislocation, with average time between injury and intervention of 2.3 years. Seven patients were treated conservatively. The remaining patients were treated with surgery, including coracoid transfer and shoulder arthroplasty. For the six patients who underwent arthroplasty, meticulous soft tissue repair was performed, humeral retroversion was increased, and rehabilitation was modified. Four patients required glenoid bone graft, and two required rotator cuff repair. For nine patients followed for an average of 3.9 years, eight patients demonstrated excellent or satisfactory results, with one unsatisfactory case.)

Summary

Patients with chronic glenohumeral dislocations can frequently present with a constellation of injuries to the humeral head articular surface, the glenoid, the rotator cuff, and the capsulolabral structures. Therefore, management of these patients can be a challenge. Treatment of this condition should be first and foremost prophylactic. Through a careful history, physical examination, and complete radiographic examination, these injuries can be identified and managed acutely, thus preventing chronic sequelae. When confronted with a chronic glenohumeral dislocation, the treating surgeon must approach this patient with a systematic approach in order to develop the ideal treatment strategy to address all relevant pathoanatomy.

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