Chapter 10 Reverse Shoulder Arthroplasty for Acute Fracture: Indications and Technique

10.1055/b-0037-146571

Chapter 10 Reverse Shoulder Arthroplasty for Acute Fracture: Indications and Technique

Wame N. Waggenspack, Jr., Benjamin W. Szerlip, and T. Bradley Edwards

Abstract

Reverse shoulder arthroplasty is an increasingly utilized treatment option for acute, complex proximal humerus fractures in the elderly and other select patients, where factors such as poor bone quality, rotator cuff pathology, and other comorbidities may preclude successful reconstruction and osteosynthesis of the proximal humerus and tuberosities. Early and midterm results are promising, with more predictable outcomes that may be less reliant on tuberosity healing, when compared to treatment with anatomic humeral head replacement. Long-term follow-up is still lacking, and surgeons utilizing reverse shoulder arthroplasty in their armamentarium should have a thorough understanding of complications unique to this implant design. We describe the current indications for reverse shoulder arthroplasty in the setting of acute fractures as well as our preferred surgical technique and outcomes.

10.1 Introduction

Acute proximal humerus fractures are the third most common fractures in patients older than 65 years, with an approximate unadjusted incidence of 82 per 100,000 person-years and a nearly 2:1 female to male distribution.1 Incidence of these injuries is expected to significantly increase with the growth in this population segment over the next decades.2,3 While the majority of proximal humerus fractures may be treated nonsurgically with satisfactory results, more complex fractures are typically treated surgically with the goal of preventing chronic pain and optimizing functional outcome.4 Optimal definitive management is challenging secondary to a lack of consensus on appropriate surgical treatment and surgical technical demands.5

10.2 Classification and Surgical Considerations

As classically described by Neer, the proximal humerus anatomy, as it relates to fractures and treatment, can be divided into four distinct parts: articular segment (head), greater and lesser tuberosities and their rotator cuff components, and the humeral shaft. Displacement of each part by 1 cm or more or angulation of more than 45 degrees is considered significant, regardless of number of fracture lines.6 Despite relatively poor interobserver reliability and intraobserver reproducibility, this classification system remains the most commonly utilized likely because of its simplicity.7

More recently, Hertel et al described a comprehensive fracture “binary description system” based on Codman’s original concept of fracture planes as opposed to fracture parts, and treats the tuberosities as interposed separate fragments between the articular humeral head and humeral shaft.8 Basic fracture planes lie between the greater tuberosity and the head, greater tuberosity and the shaft, lesser tuberosity and the head, lesser tuberosity and the shaft, and the lesser tuberosity and the greater tuberosity. As with any classification system, reliability and reproducibility are dependent on the ability to properly discern fracture lines.8

In deciding the optimal management of an acute proximal humerus fracture, the treating physician should consider fracture pattern, degree of comminution, bone quality, age and activity level of the patient, and individual skill level and preference.9,10 The vast majority, up to 85%, of proximal humerus fractures are minimally displaced and can be treated nonsurgically with a brief period of immobilization followed by a progressive rehabilitation program.6 Surgical treatment is typically reserved for patients with displaced and complex fracture patterns, with a variety of options described, including percutaneous fixation, open reduction internal fixation, and arthroplasty.

An additional surgical treatment consideration for displaced and complex fractures is risk of humeral head osteonecrosis, which is increased with more complex patterns. Hertel et al found metaphyseal head extension of less than 8 mm, medial hinge disruption of more than 2 mm, and basic fracture pattern to be good predictors of humeral head ischemia, with positive predictive value of 97% for combined short calcar, disrupted hinge, and anatomic neck fracture pattern.8 Valgus-impacted four-part fractures have a relatively low incidence of osteonecrosis and may warrant special consideration with more treatment options available without need for arthroplasty.8,11

10.3 Preoperative Evaluation and Planning

As with any orthopaedic injury, a detailed history and physical examination should be performed. Special attention should be paid to age, activity level, physical demands, and any comorbidity that may preclude successful treatment by osteosynthesis. A thorough neurologic examination should be performed, as acute neural injury is relatively common with proximal humerus fractures (67%), with important prognostic and management implications. The axillary (58%) and suprascapular (48%) nerves are most often affected.12 Visser et al reported higher incidence of nerve injury with displaced fractures. While all patients with acute nerve injury recovered normal nerve function, duration of recovery was prolonged with less favorable restoration of shoulder function.12

Simple radiographic evaluation of the acutely fractured shoulder, including the classic Neer trauma series of orthogonal views (anteroposterior, scapular “Y,” and axillary), may be sufficient if fracture lines are adequately visualized. In most cases, computed tomography (CT) is utilized to better identify fracture lines and displacement. In addition, CT provides information on glenoid bone stock and the rotator cuff fatty infiltration and atrophy. We routinely obtain CT scans as part of the arthroplasty preoperative workup.

10.4 Indications for Reverse Shoulder Arthroplasty

Traditional indications, as described by Neer, for management of acute proximal humerus fractures with arthroplasty include displaced three- and four-part fractures not amenable to open reduction internal fixation, fracture dislocations, and head-splitting fractures.13,14,15 Additional patient considerations for arthroplasty include complex fractures in severely osteoporotic bone, severely comminuted fractures, and risk of osteonecrosis. Krishnan et al elegantly outlined a treatment decision-making algorithm that accounts for age, bone quality, fracture pattern, and surgical timing.9 The unifying theme of these factors is unacceptable increased risk of internal fixation failure or complications such as screw penetration or cutout and humeral head osteonecrosis.

While patients older than 70 years are generally considered candidates for arthroplasty, chronological age should not be regarded as important as activity level, bone quality, and fracture pattern.9,13,14,16 Tingart et al described a reliable predictor of proximal humerus bone quality, obtained by measuring the medial and lateral cortical thickness at two levels.17 They reported significantly higher cortical thickness in patients younger than 70 years, with mean cortical thickness of 4.4 ± 1.0 mm. This simple tool may provide the treating surgeon additional information in the decision-making process of whether to proceed with arthroplasty.

While hemiarthroplasty has been shown to provide pain relief, functional outcomes are less predictable and dependent on tuberosity osteosynthesis for optimal results.18 Reverse shoulder arthroplasty was suggested as an alternative treatment option for elderly patients with complex fractures that would otherwise be treated with hemiarthroplasty.19,20,21,22 A reverse prosthesis relies solely on deltoid function for elevation, thus eliminating the absolute reliance on tuberosity healing for an acceptable functional outcome. Additional indications for reverse shoulder arthroplasty therefore include patients with severe tuberosity and/or metaphyseal comminution, preexisting rotator cuff pathology (cuff tear arthropathy, fatty infiltration, and atrophy of a massive tear), and any comorbidity that would affect tuberosity healing.23

In summary, our primary indication for reverse shoulder arthroplasty in acute proximal humerus fracture is a complex pattern, not amenable to open reduction internal fixation, in a patient with poor bone quality at high risk of tuberosity failure (► Fig. 10.1). We prefer to treat arthroplasty candidates with good bone quality with hemiarthroplasty and meticulous tuberosity repair.

**Fig. 10.1** AP radiograph demonstrates a four-part proximal humerus fracture with osteopenia.

The contraindications for reverse shoulder arthroplasty for proximal humerus fractures are similar to those for conventional shoulder arthroplasty. Active infection is an absolute contraindication, and poor overall health is a relative contraindication. Although there is no absolute minimum age for reverse shoulder arthroplasty, osteosynthesis should be attempted whenever possible for a physiologically young patient, even with a comminuted fracture.16,24,25 Arthroplasty should be approached with caution if the patient is unable to participate in a rehabilitation program to facilitate an optimal outcome. Deltoid insufficiency resulting from permanent axillary nerve palsy is a contraindication specific to reverse shoulder arthroplasty. However, this does not apply to transient or subclinical axillary nerve palsy, which occurs frequently in patients with proximal humerus fractures.

10.5 Surgical Technique

10.5.1 Setup

Surgery is performed under general anesthesia. It is important for the patient to be kept fully relaxed by anesthesia until implantation of components is complete to allow uniform assessment of soft-tissue tension during trialing. Similar to standard shoulder arthroplasty, the patient should be positioned in the modified beach-chair position, with care taken to position the patient sufficiently near the edge of the table to allow for full extension and adduction of the surgical arm for humeral preparation. A small folded sheet should be placed under the patient at the medial scapular border to stabilize the scapula for the glenoid portion of the procedure.

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