7 Proximal Humeral Malunions

Malunion can occur after open or closed treatment of a proximal humerus fracture, though it more frequently develops in cases treated nonoperatively. In many cases, the treating physician willingly accepts a nonanatomic alignment due to the age or underlying medical problems of the patient. On occasion, surgeons adopt a “wait and see” approach, allowing the fracture to heal prior to assessing the patient’s functional limitations. In rare instances, a proximal humerus fracture or the extent of the injury is not fully appreciated. An unfortunate example of this involves a missed posterior dislocation associated with a fracture because appropriate radiographs were not obtained. Axillary view radiographs should be included in any trauma series of the shoulder. It is important to remember that the results of late reconstruction are often inferior to those of acute anatomic restoration, so nonoperative treatment may not be indicated as often as it is.1

Other causes of malunions, or nonunions, include soft tissue interposition at the fracture site, inadequate immobilization, and overly aggressive rehabilitation. Rarely, the long head of the biceps tendon, capsule, or deltoid muscle interpose at the fracture site, blocking reduction and eventuating a non- or malunion.

Proximal humerus malunions can occur secondary to failure of internal fixation. It is often difficult to gain good screw purchase in the cancellous bone of the humeral head or tuberosity, and displacement may occur.

Types of Proximal Humeral Fractures

When evaluating a proximal humerus fracture, four parts are usually assessed: humeral head and articular fragment, greater tuberosity, lesser tuberosity, and humeral shaft. An understanding of the various types of proximal humerus fractures and the corresponding deforming forces on each fragment is helpful, as the position of malunions usually relates to these forces.

Two-Part Surgical Neck Malunions

Anterior displacement of the shaft secondary to the pull of the pectoralis major and possible abduction of the head by the rotator cuff result in anterior angulation and a varus or valgus deformity.² When severe, these deformities can cause limitation of forward flexion, and, in some cases, loss of abduction. The work of Keene et al showed that increased anterior angulation greater than 45 to 55 degrees causes limited forward elevation.³ In addition, in malunions of this type, the greater tuberosity impinges on the superior aspect of the glenoid, preventing sufficient external rotation to allow the arm to elevate properly. With each degree of varus angulation, one degree of overhead elevation is lost.⁴

Two-Part Tuberosity Malunions

Reports by Mclaughlin and Craig indicate that displacement of the greater tuberosity >5 mm may result in a symptomatic nonunion.^5,6 Two-part fractures involving the greater tuberosity may heal with the tuberosity fragment displaced posterosuperiorly secondary to the deforming forces of the rotator cuff muscles. In this fracture pattern, the normal architecture of the articular segment, humeral shaft, and glenoid are maintained. Malunions of this nature present with limited abduction and external rotation and possible secondary subacromial impingement.7 Relative losses of forward elevation or external rotation relate to the degree of superior and posterior malunion, respectively.

Isolated lesser tuberosity malunions result from pulling of the fragment medially due to the subscapularis pull. This displacement causes a spread in the anterior fibers of the rotator cuff at the rotator interval producing a bony prominence. Clinically, this is usually insignificant, though rarely a mechanical block to internal rotation or elevation develops and may result in coracoid impingement.^2,8

Three- and Four-Part Malunions

Three- and four-part malunions result in severely impaired function. Three-part fracture malunions with displacement of the greater tuberosity and surgical neck can cause deformity, avascular necrosis, and posttraumatic arthritis.⁴ When the lesser tuberosity remains intact, the humeral head is brought into internal rotation due to the pull of the subscapularis. The greater tuberosity is displaced posterosuperiorly, and the humeral shaft is pulled anteromedially. In these settings, the articular fragment often faces posteriorly. The end result is severely impaired abduction and loss of rotation.

Three-part fractures with displacement of the lesser tuberosity and surgical neck result in more severe limitation of internal rotation. In this situation, the articular segment externally rotates and abducts, causing it to face anteriorly and give the appearance of being dislocated (false fracture dislocation). Because the greater tuberosity remains attached to the humeral head, the supraspinatus, infraspinatus, and teres minor all act as deforming forces.

In four-part fractures, the blood supply to the humeral head is frequently compromised leading to high incidences of avascular necrosis. The head may be displaced laterally and may not even contact the glenoid.² Malunions of four-part fractures result in soft tissue contractures and adhesions and joint incongruity. Patients present with pain and severely restricted range of motion (ROM). In addition, these patients may suffer from chronic nerve injuries.⁷

Fracture-Dislocation Malunions

Malunions of fracture dislocations are extremely challenging cases to manage. The humeral head is no longer concentric within the glenoid, and the resultant displacement of the head may cause injury to the neurovascular bundle.⁹ Extensive soft tissue contractures are often present, and there is an increased incidence of myositis ossificans.⁴ In addition, the head location may be in close proximity to the brachial plexus and major vessels.

Patient Assessment

The patient with a proximal humerus malunion may present in a variety of ways. A thorough history and physical exam is crucial to determine the main disability. Is the primary complaint pain or lack of function? As the pain or disability associated with proximal humerus malunions varies, an assessment of the patient’s lifestyle and activity level is necessary. This will allow the physician to advise the patient of the relative benefits of surgical reconstruction. Successful treatment of these malunions demands that patients have realistic expectations of surgical reconstruction. Details of the initial injury should be elicited including mechanism, treatments received, and associated injuries. Previous injuries to the shoulder, hand dominance, and potentially complicating medical issues are all pertinent.

An overall sense of the patient’s health should be assessed during the physical exam. If the patient is dependent on the affected upper extremity to remain ambulatory and independent, one might have a lower threshold to indicate a reconstruction. The converse is also true. If it seems that a patient may not be able to participate in the extensive postoperative rehabilitation process, the threshold to operate might be raised.

On inspection, atrophy of the shoulder musculature can be expected, but signs of infection, including erythema, fluctuance, and wound drainage necessitate further infection work-up. Previous scars should be noted, as these might affect the choice of surgical approach.

Loss of motion is often the primary problem after proximal humerus malunions. ROM, especially passive ROM, allows assessment of soft tissue contractures and joint congruity. External rotation should be checked with the arm at the side and at 90 degrees of abduction. A classic finding on exam of patients with greater tuberosity malunions is the absence of external rotation with the arm maximally abducted.⁶ Impingement may also limit motion.

Rotator cuff injury may have occurred during the initial injury and should be addressed at the time of reconstruction.⁷ External rotation strength allows evaluation of the infraspinatus and teres minor. Supraspinatus function can be tested with opposed abduction at 90 degrees. Both the “lift off” test and the abdominal compression test can help assess the integrity and strength of the subscapularis. When the tuberosities are displaced there is less mechanical advantage to the rotator cuff muscles. In these instances, even with the rotator cuff intact, weakness may result. Instability is sometimes present, and should be evaluated. It is important to remember that in cases when the greater tuberosity is malunited posteriorly, it may lever the humeral head from the glenoid, simulating anterior instability.⁶

Neurologic injuries may have occurred secondary to the initial trauma, or even during the initial treatment. Careful evaluation of the motor strength of the axillary, musculocutaneous, and suprascapular nerves should be performed. Axillary nerve injury is often associated with inferior subluxation of the proximal humerus. It is important to remember that sensory deficit at the lateral border of the deltoid is not a reliable indicator of axillary nerve injury. Brachial plexus involvement may also be seen in patients with proximal humerus malunions. Fracture-dislocations have the highest incidence of accompanying neurologic injuries. In patients older than 50 with proximal humerus fractures, the incidence of electromyography- (EMG) diagnosed neurologic injuries is 50%.6 Thus, in patients with suspected nerve injury, preoperative EMG studies should be obtained.

Radiologic Assessment

Appropriate imaging assessment of patients with malunions begins with a plain radiograph trauma series of the shoulder. This includes an anteroposterior and lateral view in the plane of the scapula and an axillary view. These views usually provide sufficient information regarding the position of the fragments as well as the bone quality; however, supplemental internal and external rotation views can provide more information if necessary. In patients previously treated with internal fixation, radiographic evidence of loosening may be an indication of infection. In these cases, one should consider aspiration and culture of the joint.

Computed tomography (CT) is often essential to evaluate the full extent of injury. The degree of tuberosity displacement and certain fracture patterns, such as head splitting fractures, articular impression fractures, and chronic fracture-dislocations are best visualized with CT scans that allow three-dimensional evaluation of the fragments.^10,11 Morris et al reported that CT identified axial malposition of the greater tuberosity that was not appreciated on plain x-ray in 10 of 18 patients. Furthermore, plain films were inadequate in assessing displacement of the lesser tuberosity in all 18 patients.¹¹ Three-dimensional CT reconstructions also aid in the understanding of the position of malunited fragments.¹²

Other imaging modalities that can be useful to the surgeon include magnetic resonance imaging (MRI) and scanograms. MRI helps delineate soft tissue pathology, especially with regard to the rotator cuff and labrum. MRI also allows earlier identification of avascular necrosis than is provided by plain films. In patients with hardware from previous surgery, artifact can diminish the information available from MRI. Scanograms aid in determining the proper length of the humerus and are especially useful in proximal humerus reconstruction with hemiarthroplasty. The scanogram can establish the proper height for the prosthesis; thereby allowing the surgeon to reestablish the appropriate tension of the soft tissues.

Classification

To date, no universally accepted classification system for proximal humerus malunions exists. Many authors have simply modified the commonly used classification of acute proximal humerus fractures developed by Neer and applied it to their series of malunions.^1,9,12 Other authors have attempted to develop original classification systems useful in determining the treatment approach to the malunion.

Beredjiklian et al¹³ proposed a system of categorizing osseous and soft tissue defects. Osseous abnormalities were categorized as malposition of the greater or lesser tuberosities by more than 1 cm (type I malunion); intraarticular incongruity or a step-off of the articular surface of >5 mm (type II malunion); and malalignment of the articular segment by more than 45 degrees in any of the three planes (type III malunion). They categorized soft tissue abnormalities more broadly: soft tissue contracture, rotator cuff tear, and subacromial impingement. Although not all-inclusive, this classification system is useful in providing an overview of the involved pathology with the goal of treating each component.

Boileau et al¹²

Related posts:

Nonunions and Malunions of Monteggia Fracture Dislocations Nonunions of the Clavicle Reconstruction of Posttraumatic Stiffness and Instability Arthroplasty for Proximal Humeral Fractures Total Elbow Arthroplasty for Distal Humeral Fractures Complex Fractures of the Distal Humerus

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