Arthroplasty for Chronic Glenohumeral Dislocations



Arthroplasty for Chronic Glenohumeral Dislocations


Jason B. Smoak, MD

Matthew J. DiPaola, MD



EPIDEMIOLOGY AND BACKGROUND

A chronic glenohumeral dislocation (GHD) is generally defined as one whose recognition has been delayed by at least 3 weeks, although the exact definition is inconsistent in the current literature.1,2 Some suggest that a chronic dislocation is best defined as any dislocation that was not identified at the time of the original injury.2

Chronic GHDs account for less than 2% of all shoulder dislocations.3 Anterior GHDs are more frequent than posterior dislocations, but the incidence of chronic posterior GHDs is higher than chronic anterior GHDs.2 Chronic posterior GHDs are often misdiagnosed by initial treating physicians, which may help to explain why nearly 80% of posterior dislocations may not be discovered until they have become chronic.4

Chronic GHDs often occur in elderly or mentally unstable patients.5 Alcoholism, polytrauma, seizures, or electrical shock injuries are also well-known culprits for development of chronic GHD in young patients.3,4,5,6 Delayed diagnosis is usually due to poor patient communication, negligence, inadequate examination, and incomplete or misinterpreted radiographs.4

Undiagnosed GHDs inevitably lead to loss of function in the affected shoulder. As the delay to diagnosis increases, humeral and glenoid bone defects are perpetuated by deterioration of articular cartilage, soft-tissue contractures, and rotator cuff tears. These patients frequently have poor bone quality and low rehabilitation potential, which makes treatment of these injuries even more challenging.7

A number of treatment options have been described for chronic GHD including closed or open reduction, tendon transfers, osteotomies, osteochondral grafting, and arthroplasty. Several factors including size of bone defects, presence of a torn rotator cuff, and chronicity of the dislocation must be considered when formulating a treatment approach. Although there are no large cohorts in the current literature, several case series have demonstrated successful treatment of chronic GHDs by shoulder arthroplasty including hemiarthroplasty, anatomic total shoulder replacement, and reverse total shoulder arthroplasty (RTSA).3,5,6,7,8,9,10,11,12


EVALUATION



Physical Examination

Physical examination should always include detailed cervical spine and neurovascular examinations in addition to a complete shoulder evaluation. Neurological examination is particularly important in this population as there is a high risk for traction injury and neurological compromise. Comparison to the contralateral side is particularly useful when examination findings are subtle and may help to identify important asymmetries. Asymmetry typically worsens over time as atrophy accentuates the deformity. The clinician must be aware that patients with large body habitus may mask GHD more easily than patients with a smaller build.

In chronic anterior GHD, physical examination is often diagnostic and is characterized by fullness over the anterior glenohumeral joint in the subcoracoid region, which corresponds to the displaced humeral head.5 This finding will be more evident in thinner patients. Flattening of the posterior and lateral contours of the shoulder along with prominence of the acromion
posteriorly may be present (FIGURE 46.1). The humeral head is frequently palpable in its anterior location. Range of motion (ROM) of the affected shoulder is highly variable depending on the chronicity of the dislocation. Initially, patients may lack significant internal rotation as well as forward flexion and abduction. This may be especially true when a humeral impression fracture is locked on the glenoid rim, which is commonly known as a locked GHD. With locked GHDs, repeated attempts to move the shoulder may enlarge humeral and glenoid bone defects, which allow for a much greater arc of motion. This can be a falsely reassuring sign. The clinician must guard against misinterpreting this finding as clinical improvement.

An axillary nerve palsy may present clinically with deltoid dysfunction and/or numbness over the lateral aspect of the shoulder. The axillary nerve is the most commonly injured nerve associated with anterior GHDs. Most axillary nerve deficits resolve over a period of months; however, persistent deficits may result in less predictable outcomes following operative treatment.2,13,14 It is important to understand that a neurological examination may be unreliable in the setting of chronic GHD since it is often difficult to test deltoid function and sensation is not a reliable indicator of axillary nerve function.

The diagnosis of a chronic posterior GHD may be more challenging from physical examination perspective due to more subtle findings and its striking resemblance to other pathologies such as adhesive capsulitis. We have encountered patients treated for adhesive capsulitis whose posterior chronic GHD is only discovered when imaging studies are finally obtained. While the shoulder often lacks prominent deformity, some hallmark signs include a subtle posterior fullness with flattening of the anterior and lateral contours. Prominence of the acromion and coracoid process anteriorly is also frequently present (FIGURE 46.2). ROM is once again highly variable, yet in contrast to chronic anterior GHD, decreased external rotation is the classic finding and often presents as an internal rotation contracture. Loss of forward flexion and abduction are also often encountered in the early stages, yet enlargement of bone defects may ultimately allow for functional motion of the involved extremity. Neurovascular injury may be less common with chronic posterior GHD, but it remains critically important to examine for any deficits. Clinicians and therapists should be alert to a patient that presents with significant external rotation deficit and a firm endpoint. Overly aggressive therapy in the setting of a locked posterior GHD may result in massive erosion of the humeral head requiring a more aggressive surgical solution such as arthroplasty.







Radiographic Studies

Complete radiographic examination should be performed as part of any shoulder evaluation. A complete series of standard radiographs including a scapular anteroposterior (AP), scapular lateral (Y view), and axillary lateral or Velpeau axillary are essential in the initial evaluation of suspected chronic GHD. They should also be obtained prior to any shoulder manipulation to prevent any displacement of occult fractures. An axillary lateral or Velpeau radiograph is essential to avoid missed dislocations (FIGURE 46.3).

A chronic anterior GHD will show an empty glenoid in AP shoulder radiographs as a result of anteroinferior dislocation of the humeral head. Scapular Y images may also demonstrate the anteroinferior location of the humeral head relative to the glenoid. An axillary lateral or Velpeau view is essential to confirm the diagnosis and may also help to elucidate the extent of any anterior glenoid and posterior humeral head bone defects (FIGURE 46.4).













The AP radiographs of a chronic posterior GHD, similar to the physical examination, may only demonstrate subtle findings upon initial review. A crescent-type sign indicating the overlap of the humeral head and glenoid may be seen. A lightbulb sign, demonstrating loss of normal humeral head contour on AP radiographs such that it appears similar to a lightbulb, indicates that the humerus is in maximal internal rotation (FIGURE 46.5). Although neither of these images are diagnostic, they should alert the provider to have a high level of suspicion for posterior GHD. Once again, axillary lateral or Velpeau views are required to confirm the diagnosis. Concomitant posterior glenoid and anterior humeral head bone defects are also best represented on these radiographs.






Although diagnosis may be confirmed with standard radiographs, computed tomography (CT) is helpful to evaluate the extent of humeral and glenoid osteochondral injuries with greater accuracy. CT scan will allow for accurate and precise calculation of the percentage of articular surface defects. The arc of the humeral head defect divided by the total humeral articular surface arc is considered to be the percentage of humeral articular surface defect (FIGURE 46.6). This value is used in most treatment algorithms for chronic GHD.

In cases of chronic anterior GHD, the surgeon may want to include a CT angiogram as part of preoperative planning to delineate the path and proximity of the vasculature to the dislocated humeral head. This can be included as part of a routine CT scan and help guide decision-making if a vascular complication were considered to be an intraoperative risk. While rare, vascular complications during open reduction have the potential to produce devastating complications. To this end, the authors routinely perform these procedures with a vascular surgeon and intraoperative angiography available in case of a potential bleeding complication.

CT scans are useful for defining the extent of bony injury, they do not provide sufficient detail regarding the soft tissues. Magnetic resonance imaging (MRI) is the study of choice to evaluate the extent of injury to soft tissues of which the status of the rotator cuff and condition of the articular cartilage is most important for decision-making. However, we do not recommend routine use of MRI in all patients with chronic GHD. Rather, we reserve its use for cases where the quality of the remaining soft tissues may significantly alter our treatment plan.








TREATMENT OPTIONS AND DECISION-MAKING

Once the diagnosis of a chronic GHD has been made, a treatment strategy must be chosen. Several factors must be considered to formulate an effective treatment plan. Age, preinjury functional status, duration of dislocation, status of the rotator cuff, and extent of humeral and glenoid articular surface damage are some of the most important variables to consider.






Nonoperative treatment is generally divided into two categories: supervised neglect and closed reduction.
Supervised neglect may be appropriate for patients that have significant medical comorbidities and pose an unacceptable surgical risk or patients with minimal pain and acceptable function (FIGURE 46.7).






Closed reduction followed with a period of immobilization has been utilized in several case series with mixed results. Satisfactory outcomes were obtained in patients with small or nonexistent humeral head impression fractures and those that had been dislocated for less than 4 weeks.15,16,17,18,19 Adequate anesthesia is required for any attempted closed reduction. In addition, it should be avoided if a locked dislocation is identified.

Operative treatment is usually required for GHDs older than 4 weeks or when a sizable humeral head articular surface defect is present resulting in a locked dislocation. Treatment may be further categorized by patient age and percentage of articular surface involvement.

Joint preservation operations consisting of open reduction and stabilization are typically reserved for younger patients, those with smaller bone defects, and well preserved articular cartilage. In the setting of a 20% to 40% humeral articular surface defect, a subscapularis or infraspinatus tendon transfer with or without the lesser or greater tuberosity is often required for stabilization of chronic posterior and anterior GHD, respectively. Younger patients with humeral defects ≥40% of the articular surface may be considered candidates for osteochondral allograft reconstruction. In contrast to humeral-sided bone loss, the glenoid is much less tolerant to bone loss. Defects larger than 20% to 25% are likely to fail an isolated soft-tissue reconstruction, and glenoid bone grafting is frequently necessary. Although meticulous preoperative workup may suggest that joint preservation is possible, it is wise to have arthroplasty components available in the event that intraoperative findings preclude such surgery.

Arthroplasty is generally indicated in older patients when humeral defects are greater than 40% to 50%, of the humeral articular surface arc, in the presence of large potentially irreparable rotator cuff tears, when significant glenoid erosion and bone loss is identified, and dislocations of greater than 6 months duration. Dislocations beyond 6 months typically have unsalvageable articular cartilage as well as marked osteopenia, which makes reconstruction both challenging and unpredictable. Prosthetic options generally fall into three categories: hemiarthroplasty, anatomic total shoulder arthroplasty (ATSA), and RTSA. Each of these options has advantages and disadvantages.

Hemiarthroplasty has the advantage of preserving glenoid articular cartilage and bone stock while allowing for conversion to total shoulder arthroplasty in the future. Disadvantages may be related to the unconstrained nature of the prosthesis and difficulty with obtaining a balanced, stable articulation. Significant soft-tissue releases, capsular plication, or tendon transfers may be required in order to obtain a stable construct. Indications include younger patients or patients with poor humeral bone quality not amenable to allograft reconstruction and those with intact glenoid articular cartilage (FIGURE 46.8). It may also be used as a salvage operation for noncompliant patients or patients that lack enough glenoid bone stock for glenoid resurfacing.

The main advantage of ATSA over hemiarthroplasty is glenoid resurfacing. Disadvantages are similar to hemiarthroplasty with regards to the unconstrained nature of the prosthesis and difficulty with achieving stability. As previously mentioned, glenoid resurfacing requires sufficient glenoid bone stock; supplemental bone grafting in addition to custom or augmented glenoid prostheses may be required in the setting of significant glenoid erosion (FIGURE 46.9). ATSA may be ideal for chronic GHD with an unsalvageable humeral head and irreversible articular cartilage changes on both the humeral head and the glenoid.







RTSA is an important option for the treatment of chronic GHD for several reasons. The main advantages of RTSA include the constrained nature of the prosthesis, as well as its reliable use in the setting of rotator cuff insufficiency. A significant disadvantage is the requirement of a functioning deltoid. In situations where there is significant uncertainty concerning the status of the axillary nerve preoperatively, the surgeon may consider obtaining a preoperative electromyogram (EMG) to assess the status of the axillary nerve. This may lend some reassurance regarding deltoid function. If an axillary nerve deficit is present, it may be reasonable to delay RTSA until there is evidence of recovery at which time the procedure can be performed.

Our indications for use of RTSA in the setting of chronic GHD include elderly patients, patients in which there is significant humeral and glenoid bone loss, and those in which soft tissue balancing required for ATSA or hemiarthroplasty would prove to be challenging or lead to protracted recovery (FIGURE 46.10). As technique and implant designs continue to improve, the indications for RTSA can be expected to expand.








Jun 23, 2022 | Posted by in ORTHOPEDIC | Comments Off on Arthroplasty for Chronic Glenohumeral Dislocations
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