Hemiarthroplasty: Indications and Technique



Hemiarthroplasty: Indications and Technique


Blake J. Schultz, MD

Kenneth A. Egol, MD



INTRODUCTION

Fractures involving the proximal humerus account for approximately 4% to 5% of all fractures.1,2,3 They occur in a bimodal distribution and are the second most common upper extremity fracture in patients older than 65 years.4 While the majority of proximal humerus fractures, especially in the elderly, can be treated nonoperatively,5,6 three- and four-part fractures and fracture-dislocations are often indicated for surgery. The popularization of locking plate technology has expanded the indications for open reduction and internal fixation (ORIF) of proximal humerus fractures,7,8,9,10,11,12,13,14 but locked plating of the proximal humerus has its own set of complications.15,16,17,18,19,20 Arthroplasty remains an option when there is concern about the viability of the humeral head or the ability to achieve an acceptable reduction and secure fixation. Hemiarthroplasty has proven to reliably reduce pain, but postoperative functional outcomes have been less predictable.21,22,23,24,25,26,27 More recently, reverse total shoulder arthroplasty (TSA) has been proven to be a safe and effective option for restoration of motion and function in elderly patients who sustain a proximal humerus fracture,28,29,30,31,32,33 but there is still a role for hemiarthroplasty in select patients. This chapter reviews the indications for shoulder hemiarthroplasty in the setting of proximal humerus fractures, including fracture pattern and pertinent patient factors, as well as surgical techniques to optimize outcomes.


FRACTURE CLASSIFICATION

The Neer classification classically used to describe proximal humerus fractures is based on the number of distinct fracture parts and their displacement.34 The four potential parts include the humeral articular surface, greater tuberosity, lesser tuberosity, and humeral shaft (FIGURE 28.1). Traditionally, displacement was defined as fragments with angulation of >45° or >1 cm of separation. In addition, literature suggests that only 5 mm of displacement of the greater tuberosity specifically should be accepted, but this is also based on the direction of fragment displacement.15,35,36 Fractures are described as two-, three- and four-part fractures with or without dislocations. Proximal humerus fractures can also be described according to the AO Foundation/Orthopaedic Trauma Association classification, which focuses on the extra-versus intra-articular location of the fracture37 (FIGURE 28.2). The Hertel classification is also used, noting specific fracture characteristics to predict the risk of fracture-induced humeral head ischemia.38 Fractures through the anatomic neck, metaphyseal extension less than 8 mm, loss of the medial hinge, and displacement of the humeral head all increase the risk of humeral head ischemia.38

Indications for hemiarthroplasty are discussed in detail below. However, they generally include certain classic four-part fractures, select three-part fractures, three- and four-fracture-dislocations, and head-splitting fracture patterns with substantial articular involvement that are not amenable to ORIF.


EVALUATION

Proximal humerus fractures typically occur in a bimodal distribution, with young patients often involved in high-energy trauma and elderly patients via low-energy mechanisms. Low-energy mechanism proximal humerus fractures should raise concern for poor bone quality. These fractures in the elderly are considered a “fragility fracture” and should lead to the implementation of appropriate medical care for the treatment of osteoporosis. As with any fracture, it is important to assess for any medical comorbidities or risk factors that could affect bone healing potential.


SOCIAL HISTORY

There is a wide range of treatment options for proximal humerus fractures, so a detailed social history is important, including occupation, handedness, activity level, and social habits including alcohol and drug use. Baseline functional status and activities of daily living goals (patient expectations) are particularly important to understand when considering hemiarthroplasty. Additionally, any conditions that predispose the patient to seizures (medications, trauma, strokes, etc) are important to document when considering any type of arthroplasty. The patient’s cognitive and physical ability to follow a structured postoperative rehabilitation course should also be considered.21,39,40







FIGURE 28.1 Neer took Codman’s original classification of proximal humerus fractures that divided the proximal humerus into the greater tuberosity, lesser tuberosity, humeral head, and shaft and expanded it to include fracture displacement (>1 cm) and angulation (>45°). General indications for hemiarthroplasty according to the Neer classification include select three-part fractures, classic four-part fractures, and fracture-dislocations. (Reprinted with permission from Jones CB. Proximal humeral fractures. In: Boyer MI, ed. AAOS Comprehensive Orthopaedic Review 2. American Academy of Orthopedic Surgeons; 2014:293-302.)







FIGURE 28.2 The AO Foundation/Orthopaedic Trauma Association classification focuses on the extra-versus intra-articular location of the fracture. Specific fracture patterns indicated for hemiarthroplasty including head-splitting and those with substantial articular involvement. (Redrawn with permission from Cadet ER, Ahmad CS. Hemiarthroplasty for three- and four-part proximal humerus fractures. J Am Acad Orthop Surg. 2012;20(1):17-27, Figure 3.)


PHYSICAL EXAMINATION

Patients with a proximal humerus fracture will have swelling, tenderness, and ecchymosis about the shoulder girdle and extending into the arm and forearm and often to the chest wall (FIGURE 28.3). They will have limited active and passive range of motion (ROM) secondary to pain or loss of rotator cuff function. Assessment for signs of anterior or posterior dislocation, including the ability to palpate the humeral head, may guide the need to assist or utilize alternative radiographic views. Overall, up to 90% of proximal humerus fractures are isolated injuries.41 However, in the elderly population, up to 16% of patients will have an associated fracture, with distal radius and proximal femur being the two most common fractures, so a thorough musculoskeletal examination is necessary.

It is essential to document a careful neurologic examination, especially axillary and musculocutaneous nerve function, as neurologic injury may be present in up to 45% of these injuries.39 Assessing deltoid motor function to evaluate axillary nerve function is particularly important when considering different arthroplasty options. While this can be difficult in the acute setting, assessing all three heads of the deltoid is essential. A vascular examination, both at the fracture site and distally in the hand, is also important to obtain. Any palpable thrill or bruit necessitates a vascular surgery consult.

Though it will be difficult to assess in an acute fracture due to pain, rotator cuff function should be evaluated in all patients with proximal humerus fracture, especially the elderly, because of the risk for associated injury.42 Previous studies have demonstrated that rotator
cuff tears may be present in up to 50% of patients who sustain proximal humerus fractures. This incidence increases to over 60% in patients older than 60 years.43,44,45,46 However, rotator cuff compromise is often present prior to the injury as a result of age-related degeneration, making it difficult to discern if a rotator cuff deficit is acute, chronic, or an acute exacerbation of a chronic problem. Regardless, rotator cuff function is an important factor to consider when determining a treatment plan and implant options. Concomitant injuries to the shoulder are also particularly important to diagnose and understand since they may dictate treatment. Patients with fracture-dislocations may have associated glenoid rim or neck fractures (especially in the elderly), so a thorough radiographic assessment is important.






FIGURE 28.3 Patients may have ecchymosis and swelling through the shoulder girdle extending into the axilla and down the humeral shaft.






FIGURE 28.4 A 64-year-old woman following a ground-level fall. A, Anteroposterior view of the right shoulder showing a four-part proximal humerus fracture involving the anatomic neck and greater and lesser tuberosities. There is inferior subluxation of the humeral head in relation to the glenoid. B, Lateral scapula view. C, Axillary view showing the glenohumeral joint is reduced.


RADIOGRAPHIC/IMAGING STUDIES

A standard shoulder trauma series should be obtained, including an anteroposterior (AP), lateral scapula, and axillary view (FIGURE 28.4). The axillary view is critical to evaluate the position of the humeral head on the glenoid and to assess for an associated glenohumeral dislocation. If the patient cannot tolerate positioning for the axillary view, a Velpeau axillary view can be obtained.47 Computed tomography (CT) scans can be helpful to assess tuberosity displacement, as well as to assess involvement of the humeral head, including head-splitting components (FIGURE 28.5). The soft-tissue window in the axial and sagittal views provides information about rotator cuff degeneration, including muscle atrophy or fatty infiltration, which can affect surgical decision-making.48 Three-dimensional reconstruction with glenoid subtraction can also be helpful to understand the tuberosity fracture lines.23

The four rotator cuff muscles attach to the proximal humerus and are responsible for the direction of fracture fragment displacement. The supraspinatus, infraspinatus, and teres minor attach to the greater tuberosity and displace the fragment superiorly or posteriorly, depending on the portion of the greater tuberosity involved. The subscapularis attaches to the lesser tuberosity and will displace this fragment anteromedially. The humeral shaft is also displaced medially and anteriorly by the pectoralis major49 (FIGURE 28.6). The articular segment is
typically displaced and rotated laterally, but this can be variable. The loss of soft-tissue attachments to the articular segment can significantly affect the blood supply to the humeral head, putting it at risk for osteonecrosis (ON). The length of medial humeral calcar involvement (<8 mm) is also a risk factor for head ischemia.38






FIGURE 28.5 A 64-year-old male patient who fell down the stairs with isolated right shoulder pain. A, Axial CT images showing involvement of the greater and lesser tuberosity fragments adjacent to the bicipital groove. Also confirms the glenoid is intact. B, Coronal CT cut showing the anatomic neck fracture with significant comminution and the displaced greater tuberosity fragment. Intraoperatively, the articular surface was rotated 180° away from the glenohumeral joint with extensive comminution of the anatomic neck fracture. Because of concern regarding the viability of the humeral head and ability to maintain an accurate reduction, the plan was changed from open reduction and internal fixation to arthroplasty. The patient’s main complaint preoperatively was pain control, so the decision was made to proceed with hemiarthroplasty.






FIGURE 28.6 Classic four-part fracture characterized by anterior and medial displacement of the shaft caused by the pull of the pectoralis major (A), posterior/superior displacement of the greater tuberosity caused by the supraspinatus, infraspinatus, and teres minor (B), anteromedial displacement of the lesser tuberosity caused by the pull of the subscapularis (C), and lateral displacement of the articular segment (D).


SURGICAL INDICATIONS

Indications for prosthetic replacement include the significantly displaced four-part fractures (excluding the valgus impacted), four-part fracture-dislocations, select three-part fractures and fracture-dislocations, and
specific fracture patterns including head-splitting fractures and head depression fractures involving more than 40% of the articular surface.23,35

Locked plating technology has expanded the indications for ORIF for most three-part and even some four-part fractures, especially in young patients with good bone stock and an intact rotator cuff.7,8,9,10 However, patients with severe osteopenia or inadequate bone stock may be better candidates for arthroplasty than for internal fixation.49,50 ON of the humeral head is a known sequelae of certain proximal humerus fracture patterns and may guide treatment toward arthroplasty rather than ORIF in high-risk patients or fracture patterns. ON after surgical fixation is generally a predictor of poor outcomes.51 However, some authors have found that patients with ON after proximal humerus fixation had comparable functional outcomes to patients with hemiarthroplasty, which may indicate that the risk of ON should not necessarily be an absolute indication for hemiarthroplasty.52

Four-part fractures and fracture-dislocations occur more commonly in elderly patients.53 The deforming muscle forces causing displacement of each part make adequate closed reduction difficult to maintain.34,53 In addition, closed reduction of fracture-dislocations specifically has an increased risk of neurovascular injury secondary to traction and manipulation attempts.49 Increasing displacement also impacts the blood supply to the humeral head, with four-part fractures having the highest risk of developing ON23 with a reported incidence of 20% to 30%.54 Patients with selected three-part fractures, including fracture-dislocations, head-splitting fractures, or compression fractures of 40% or more of the humeral head may also be candidates for hemiarthroplasty.23,24

When deciding between anatomic TSA, reverse TSA, and shoulder hemiarthroplasty, it is important to consider rotator cuff integrity since rotator cuff compromise is a contraindication to hemiarthroplasty and anatomic TSA. In addition, patient-specific social and functional factors need to be noted. Hemiarthroplasty has been shown to reliably reduce pain, but functional outcome has been less predictable.1,21,22,23,52 With this in mind, the patient’s age, baseline functional status, and activity goals will all play significant roles in treatment choice. If the initial decision is ORIF, the surgeon should still be prepared to change plans intraoperatively to a hemiarthroplasty if the humeral head is not reconstructable or to a reverse TSA if there is concern for rotator cuff dysfunction. While there has been a shift away from hemiarthroplasty toward reverse TSA,11 the issues surrounding glenoid bone stock and the potential for future revision surgery allow hemiarthroplasty to remain a viable option in select patients such as younger patients with unreconstructable fractures, those with an axillary nerve injury that compromises deltoid function, or those with compromised glenoid bone stock not amenable to glenoid resurfacing.


CONTRAINDICATIONS

Contraindications for hemiarthroplasty include patients with global neurologic injury that limits use of the involved upper extremity and those with known rotator cuff dysfunction.23 Reverse shoulder arthroplasty is a better option for patients with significant preexisting rotator cuff compromise as long as deltoid function is intact. As with all arthroplasty procedures, contraindications include patients not medically stable for surgery and those with active infections.


SURGICAL TECHNIQUE


Implant Options

Manufacturers have developed fracture-specific stems to help address the traditional pitfalls of hemiarthroplasty, including component malposition and tuberosity reduction, fixation, and healing.55

To address tuberosity reduction, stems have strategically placed slots for suture fixation and keel cutouts for tuberosity fragment placement (FIGURE 28.7). To facilitate tuberosity healing, there are various implant coating options as well as fenestrations in the stem to allow for bone grafting. For stem positioning, there are temporary intra- and extramedullary fixation jigs that allow for provisional assessment of stem placement, as well as various stem size and shape options to optimize canal fit. To enhance stability, there is a range of head sizes available, and some systems have radiopaque trial heads that allow for intraoperative fluoroscopy to assess stem position and greater tuberosity to head height.

Newer stems also have the ability to convert a well-fixed hemiarthroplasty to a reverse TSA, which is an important benefit should a revision be necessary.56 Surgeons should be familiar with the specific design characteristics and stem options of whichever implant system they use to optimize outcomes.23


APPROACH

We prefer that the patient be seated in the beach chair position with the head firmly secured in the head rest, similar to that for anatomic or reverse TSA described in Chapters 13 and 23 (FIGURE 28.8). For hemiarthroplasty, it is important to be able to fully adduct and extend the arm for canal preparation. Hemiarthroplasty is most often performed through a deltopectoral approach, but the anterolateral deltoid-splitting approach is an acceptable alternative, and may have some advantage for addressing posterior fracture fragments and managing rotator cuff issues.57,58 The anterior branch of the axillary nerve traverses the deltoid 4 to 6 cm distal to the edge of the acromion,59,60 so particular attention is needed to identify and protect the nerve throughout the procedure.58 The deltopectoral approach is our preferred approach and is described here.

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Jun 23, 2022 | Posted by in ORTHOPEDIC | Comments Off on Hemiarthroplasty: Indications and Technique

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