Reverse Total Shoulder Arthroplasty After Failed Fracture Hemiarthroplasty



Reverse Total Shoulder Arthroplasty After Failed Fracture Hemiarthroplasty


Surena Namdari, MD

Gerald R. Williams Jr, MD



INTRODUCTION

Hemiarthroplasty for the diagnosis of proximal humerus fracture is less commonly performed. Rates of hemiarthroplasty utilization have declined and are projected to decline further due to the expanding indications for reverse shoulder arthroplasty. While satisfactory results can be achieved with hemiarthroplasty for fracture, the technical demands of the operation and the unpredictability with regards to tuberosity healing and rehabilitation potential can compromise results. When hemiarthroplasty for fracture fails, unique challenges are encountered, including proximal humeral deformity, glenoid and humeral bone loss, and prosthetic loosening. The purpose of this chapter is to discuss the evaluation and complex management of the failed hemiarthroplasty for fracture with focus on conversion to reverse total shoulder arthroplasty.


EVALUATION

Patients present with dissatisfaction following hemiarthroplasty for fracture because of a number of reasons. Most often, the last recollection they have of their shoulder, before they broke it, is that it was normal. Therefore, a certain amount of dissatisfaction occurs even in patients who have a good result because of the lack of prior disability. Patient complaints usually center around pain and restricted function. Although both complaints are usually present to some degree, determining which is most prominent is important from a prognostic perspective. Pain is more responsive than function to revision surgery. Once the most prominent chief complaint has been identified, the remainder of the evaluation includes history, physical examination, and imaging. In addition, based on the presentation, other studies may be indicated. Finally, an attempt should be made to attain the prior operative report, as it can yield information regarding the specific implant used, whether or not cement was used, and specific surgical technique details that might impact the revision.

A thorough history will help elucidate shoulder complaints that were present before the fracture, the severity of the trauma that caused the injury, the presence of concomitant injuries, the presence of patient comorbidities that may affect outcome, as well as the postoperative course following the hemiarthroplasty. The presence of numbness or paresthesia, either at the time of the original injury or at presentation for revision, may be indicative of a brachial plexus or other nerve injury that likely will affect the outcome. Finally, the patient should be questioned about whether or not there were any wound healing issues such as drainage or redness that prompted temporary antibiotic treatment.

Careful physical examination will provide information that is helpful in determining the cause(s) of the patient’s complaints as well as potential strategies for surgical intervention. The location and physical characteristics of the scar should be noted. The presence of actively draining or apparently healed sinus tracts, widened scars, or hypertrophic scars should also be noted. In addition, all three heads of the deltoid should be inspected for atrophy. Observable atrophy of all three heads may indicate complete axillary nerve palsy; while individual atrophy of the anterior deltoid may indicate partially recovered axillary nerve injury, local trauma to the anterior deltoid muscle, or denervation of the anterior deltoid from the surgical approach. Specific atrophy of the supraspinatus or infraspinatus may suggest preexisting cuff tear, greater tuberosity nonunion, or suprascapular nerve injury.

Active and passive range of motion should be measured and compared to the opposite, normal side. Patients presenting for revision rarely have good motion, unless they are presenting with late pain following a good functional result. Most often, the shoulder is stiff with equal or nearly equal loss of active and passive range of motion in virtually all planes. Alternatively, patients with tuberosity nonunion may present with relatively preserved passive range of motion but poor active motion. This may be accompanied by the presence of a positive external rotation lag sign, a positive abdominal compression test, or anterosuperior humeral head escape with attempted elevation. It is also possible to have combined severe stiffness as well as cuff insufficiency, particularly with fibrous union or malunion of the greater tuberosity.

Identification of localized tenderness is also important. Tenderness over the tip of the coracoid process is
common and may represent abnormal contact between the coracoid and the humeral head, especially if the humeral head has been placed too superiorly or the subscapularis has failed. Tuberosity failure may result in proximal humeral migration which, if severe and prolonged, may result in acromial erosion with subsequent stress fracture. This may present with direct acromial tenderness. Finally, symptomatic acromioclavicular arthropathy may rarely present concomitantly with painful hemiarthroplasty. Tenderness over the acromioclavicular joint should be noted.

Initial imaging should include anteroposterior views in internal rotation and external rotation, an axillary lateral view, and a trans-scapular Y view. All images should include the tip of the prosthesis. In addition, an attempt should be made to attain all preoperative images, including computed tomographic (CT) and magnetic resonance imaging (MRI) scans. The preoperative and serial postoperative radiographs may yield information with regard to the presence of dislocation, the type of fracture, the amount of comminution, as well as the size and quality of the tuberosity fragments, especially the greater tuberosity.

Plain radiographic examination most often reveals enough information to formulate a diagnosis and initial plan. Important findings include proximal humeral migration (FIGURE 30.1), tuberosity position, tuberosity union, presence or absence of cement, the size of the distal cement plug, humeral component loosening, endosteal humeral erosion or resorption, humeral head subluxation, and glenoid erosion. If proximal humeral migration is absent or mild, it suggests that rotator cuff function is reasonable. When proximal migration is severe, it is often associated with anterosuperior glenoid erosion. The greater tuberosity, especially if it is ununited, may be positioned severely posteriorly (FIGURE 30.2). This is often not seen well except on the axillary view. It is also commonly associated with anterior humeral subluxation and anterior glenoid erosion. The presence of severe endosteal erosion of the humerus is usually a sign that the component is loose. In addition, this should raise the suspicion for infection. However, cemented stems that are smooth and cylindrical and not supported by adequate proximal bone can loosen early in the absence of infection.1,2 If substantial proximal humeral bone loss is present, full-length views of both humeri with magnification markers should be attained to accurately measure the amount of humeral bone loss and shortening.3

Advanced imaging is performed in most patients who are being considered for revision of hemiarthroplasty following fracture to reverse total shoulder arthroplasty. The presence of the metal humeral head can make the recognition of glenoid erosion difficult on plain radiographs. CT scan is indicated in most cases to assess glenoid morphology tuberosity position (FIGURE 30.3). Three-dimensional reconstruction and metal suppression techniques are typically used. Although intra-articular contrast is helpful for determining cuff integrity, if the decision has already been made to convert to reverse arthroplasty, this information may not be as relevant. Although some centers have found postarthroplasty MRI scanning to be helpful, we prefer to add contrast to the CT if we are concerned about rotator cuff integrity rather than use MRI scanning.4






Additional studies may be indicated, depending on the presentation. Infection workup is performed in every case and is described in another chapter. Electromyography and nerve conduction velocity (EMG/NCV) studies are performed if there is suspicion of persistent nerve injury on physical examination. We have a low threshold for attaining EMG/NCV studies because patients with completely or incompletely recovered nerve injuries may be more susceptible to recurrent nerve injury at the time of revision. Finally, arteriography is rarely used and is reserved for patients with diminished pulses or abnormal Allen tests, especially if they complain of cold intolerance or forearm cramping.


SURGICAL MANAGEMENT

The decision to revise a painful, dysfunctional hemiarthroplasty that was placed for humeral fracture to a reverse total shoulder arthroplasty should be made carefully and with considerable discussion with the patient. Preoperative planning is critical in all revisions. In almost
all cases, it is possible to know the implant manufacturer. The prior operative report is extremely helpful. In addition, the appearance of the stem may be recognized by the surgeon. There is also a library of common implants with radiographic examples that was created by the University of Washington Shoulder Service and can be accessed at this link: faculty.washington.edu/alexbert/Shoulder/CommonUSShoulderProstheses.htm.











Knowledge of the specific implant will allow the surgeon to have the implants at surgery if the stem is convertible and instruments to facilitate extraction if they are needed. Assuming the stem is going to be replaced, the surgeon should have short, standard, and long-stem
implants available. A dedicated shoulder revision instrument set or a hip revision set should be available in addition to a C-arm, microsagittal saw, complete set of osteotomes, pencil-tipped burr, and cables. In cases with a large distal cement plug, ultrasonic cement removal devices may be helpful, particularly if the plan is to convert to a long-stemmed device.5 Structural proximal humeral allografts—with attached rotator cuff tendons, if possible—allograft struts, and nonstructural cancellous allograft chips should be available. Finally, metal-augmented humeral and glenoid components can be used as an alternative to allograft in cases with humeral or glenoid bone loss.6,7


SURGICAL TECHNIQUE

Revisions are always more complicated than primary procedures. These revisions are among the most challenging. The surgeon should take a systematic approach to all portions of the procedure and attempt to make each step as similar as possible to a primary reverse arthroplasty. Important principles include adequate development of all soft-tissue planes from the skin all the way to the glenoid, identification and protection of neurovascular structures, adequate capsular release or excision, avoidance of bone impingement, and reestablishment of adequate soft-tissue tension. Some cases will be more challenging than others, but the important steps in all include anesthesia and patient positioning, skin incision and superficial dissection, deep dissection, humeral exposure, greater tuberosity assessment, glenoid exposure, humeral stem extraction, humeral component placement, stability assessment, final implant placement, and subscapularis closure.

The ultimate choice of anesthesia is made by the patient in consultation with the anesthesiologist. Most often, a combination of general and regional anesthesia is chosen. After induction of anesthesia, the patient is placed in a beach chair position with the shoulder positioned over the edge of the table allowing unencumbered adduction and extension of the arm. The head and neck are stabilized in a neutral position and, all bony and neurological prominences are padded appropriately. The C-arm is positioned on the opposite side of the table, and verification of adequate x-ray visualization is performed. The shoulder is then prepared and draped in normal sterile fashion. A mechanical arm holding device is used to stabilize the arm throughout the procedure. Alternatively, a padded Mayo stand can be used.

The previous skin incision is often slightly vertical and lateral in comparison to the normal deltopectoral incision. This may be the result of the incision having been made on an extremely swollen shoulder and arm. However, in almost all cases, the previous incision can be utilized. If necessary, full-thickness subcutaneous flaps can be undermined superomedially and inferolaterally to expose the deltopectoral interval. The incision may need to be extended distally to facilitate an anterolateral approach to the humerus, especially if a humeral split or window is required for stem removal. The cephalic vein may not be easily identified. Rather than trying to dissect in a scarred deltopectoral interval, identify the tip of the coracoid and expose it by incising over it with an electrocautery. This allows taking a small (5 mm) strip of the pectoralis major laterally with the scarred deltopectoral interval and the remaining portion of the pectoralis major medially. This interval is dissected proximally to the clavicle and distally to the deltoid tubercle.

The superficial layers are typically scarred to one another because of the soft-tissue injury associated with the fracture as well as the prior surgery. There are usually dense adhesions between the pectoralis major and the conjoined tendon, the deltoid and underlying humerus, and within the subacromial space. Starting at the tip of the coracoid, dissect between the deep surface of the pectoralis muscle and the underlying conjoined tendon, from proximal to distal. The glistening fibers of the conjoined tendon are clearly discernible from the muscular pectoralis muscle. This interspace should be dissected completely to the pectoralis insertion. After identifying the pectoralis insertion on the humerus, dissect between it and the tendon of the deltoid until a space is created between the deltoid tendon and the humeral shaft. Place a blunt Hohmann retractor in this space and retract the anterior deltoid insertion laterally. Proceed to dissect the deltoid away from the humeral shaft from distal to proximal until a point just distal to the metaphyseal flare of the humerus to avoid injuring the axillary nerve. The subacromial space can be identified by palpating the coracoacromial ligament attachment on the exposed coracoid tip and dissecting bluntly under it with a curved Mayo scissors. A blunt Hohmann retractor is placed in this interval, and the adhesions in the lateral portion of the subacromial space are released. The arm is then slightly abducted and progressively internally rotated so that the adhesions between the proximal humerus and the deltoid can be released. Care is taken to keep the dissection on bone to protect the axillary nerve. With the superficial layers mobilized, the pectoralis major is retracted medially and the deltoid is retracted laterally with a self-retaining Koebel retractor. The anterosuperior deltoid is retracted superolaterally with a blunt Hohmann or Brown Deltoid retractor within the subacromial space.

Deep dissection is comprised of developing the layer between the posterior surface of the conjoined tendon and the anterior surface of the subscapularis in addition to biceps exposure and tenodesis. The easiest and safest place to start the dissection deep to the conjoined tendon is superiorly, just distal to the base of the coracoid. In almost all cases, the space deep to the coracoid elbow and tip, and distal to the coracoid base is relatively devoid of adhesions. Blunt dissection is performed
with a curved Mayo scissors in this area from lateral to medial. Once this space has been enlarged, digital palpation can usually identify the axillary nerve, and occasionally, the axillary artery. Distal and lateral dissection can then proceed until the axillary nerve can be palpated at the inferior aspect of the joint progressing into the quadrilateral space. The surgeon should also palpate for the musculocutaneous nerve, which, if present in the surgical field, will be slightly lateral and anterior to the axillary nerve. All neurovascular structures should be protected throughout the procedure. In some cases, the subscapularis and anterior capsule may be deficient. The process of finding the neurovascular structures is the same, but the surgeon should proceed with even greater caution.

A special mention should be made regarding the course of the musculocutaneous nerve and axillary artery in these cases. As the dissection is carried distally, along the lateral aspect of the conjoined tendon, the musculocutaneous nerve can occasionally be found in an extremely lateral and anterior location. Utilization of an electrocautery to dissect slowly along the lateral aspect of the conjoined tendon while mobilizing it away from the subscapularis can provide the surgeon a warning when the nerve is getting close to the dissection plane. One can then proceed with blunt dissection to identify and protect the nerve. The axillary artery can be scarred into the subscapularis and be damaged, even with blunt dissection. When this happens, the rate of blood loss is substantial. The situation can be stabilized with application of direct pressure. Exposure of the axillary artery can be gained quickly by releasing the conjoined tendon origin and the pectoralis minor tendon insertion from the coracoid.8 Occasionally, release of the pectoralis major tendon from the humerus is also required.8 These maneuvers allow immediate and extensile visualization of the axillary artery. Vessel loops can be passed around the artery, proximal and distal to the injury, to gain control. Definitive management may require vascular consult. This is a rare event but one that requires quick recognition and management.

After complete mobilization of the conjoined tendon, it is retracted medially. The arm is placed in slight internal rotation using the mechanical arm holder. An attempt is made to aspirate the joint for fluid to send for culture. The biceps tendon is palpated slightly superior to the upper border of the pectoralis major tendon. It is then exposed by incising the sheath from the upper border of the pectoralis tendon proximally, through the bicipital groove, and across the rotator interval to the supraglenoid tubercle. This rotator interval incision is often made parallel to the upper border of the subscapularis, leaving the rotator interval tissue with the supraspinatus. Our preference is to angle slightly more posteriorly, along the anterior edge of the supraspinatus, so that the rotator interval stays with the subscapularis. This helps with visualization of the greater tuberosity junction with the prosthetic head. The long head of the biceps, when present, is then tenodesed to the upper border of the pectoralis major tendon with two nonabsorbable sutures and excised proximally. Soft-tissue cultures are sent from the bicipital groove area and the rotator interval.

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Jun 23, 2022 | Posted by in ORTHOPEDIC | Comments Off on Reverse Total Shoulder Arthroplasty After Failed Fracture Hemiarthroplasty
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