Proximal Humerus and Clavicle Complications

History

In the pediatric and adolescent populations, proximal humerus fractures most often result from moderate- or high-energy trauma, with a strong predilection for males. Indirect trauma to an outstretched, abducted, and externally rotated upper extremity is a more common mechanism than a direct blow to the shoulder girdle. The resultant injury is typically extracapsular, affecting the metaphyseal or physeal regions, with Salter-Harris II morphology being the most common pattern. Lower energy fractures should raise suspicion for pathologic or neoplastic etiology, as proximal humerus fractures are often associated with unicameral bone cysts (UBCs) and aneurysmal bone cysts. The “fallen leaf sign” is a classic radiographic finding associated with UBC, and may be helpful in diagnosis, which can be further corroborated by magnetic resonance imaging (MRI) versus computed tomography (CT).

Patient Considerations

The proximal humeral physis contributes to approximately 80% of longitudinal growth of the humerus, thereby exhibiting tremendous metabolic activity in adolescence and an underlying capacity for fracture remodeling. Predictably, younger patients have a higher propensity to remodel, and therefore nonanatomic reduction of the proximal humerus may be more readily accepted in children under 13 years of age ( Fig. 1.2 ). Because final fusion of the proximal humeral physis is typically anticipated at age 14 to 17 years in females, and 16 to 18 years in males, decision-making for patients 14 to 18 years of age must be more individualized based on displacement and angulation.

Relevant Anatomy

Vascularity to the proximal humerus is predominantly supplied by the posterior circumflex humeral branch off the axillary artery. This notion may be relevant in the prediction and prevention of humeral head osteonecrosis, an extremely rare complication in the skeletally immature population. An intact posteromedial metaphyseal hinge seen on plain radiographs is typically consistent with an intact posterior humeral circumflex artery.

The axillary nerve is in close proximity to the proximal humerus and may be vulnerable to insult with any proximal humerus fracture, glenohumeral dislocation, or operative intervention on the proximal humerus. Anatomic studies have demonstrated that lateral pins inserted for percutaneous treatment of proximal humerus fractures may reside as near as 3 mm to the axillary nerve. To mitigate the potential risk of axillary nerve injury with lateral percutaneous pin fixation, the starting point for the proximal most pin should be greater than 5 cm distal to the anterolateral corner of the acromion, which represents the typically level of the axillary nerve in adults with arm in neutral abduction and rotation. This distance may be inaccurate in skeletally immature patients with shorter appendages, and therefore care must be taken to identify other anatomic landmarks that can help identify the level of the axillary nerve. The glenoid neck is one such landmark. The axillary nerve enters the quadrangular space from its origin on the posterior cord of the brachial plexus, which coincides with the inferior margin of the glenoid neck. With a more anterior pin entry or errant lateral pin, the musculocutaneous nerve may be at risk as it enters the posterior aspect of the coracobrachialis in a medial to lateral direction inferior to the coracoid.

Physical Examination

Patients with minimally displaced or nondisplaced proximal humerus fractures will typically present with mild swelling and focal tenderness to the proximal humerus region, with minimal apparent deformity. Greater degrees of physeal displacement may be accompanied by more significant fracture hematomas, therefore accounting for increased edema and ecchymosis. Acutely, pain is exacerbated with attempted shoulder motion. A displaced proximal humerus fracture will typically present with the appearance of a shortened and rotated extremity, classically apex anterior and varus.

In both nondisplaced and displaced fractures, skin should be carefully assessed for any potential compromise or impending open injury. In conscious patients, while neurovascular injuries associated with proximal humerus fractures are relatively rare, occurring less than 1% of the time, an accurate neurovascular assessment is essential to evaluate for vascular, brachial plexus, or peripheral nerve injuries and to provide a baseline from which to gauge progression of symptoms.

Imaging

Standard radiographs of the shoulder, including anteroposterior (AP), lateral, and axillary views, should be routinely acquired in the assessment of proximal humerus fractures. In circumstances where axillary views may not be possible, a scapular Y view or Velpeau view should be obtained to ensure glenohumeral joint reduction, though dislocations associated with humerus fractures are rare, estimated at around 2%. Radiographs should be critically assessed for pathologic fracture.

In patients nearing skeletal maturity, an assessment of skeletal age may be helpful. Historically, left hand bone age radiographs have been used to provide a more accurate determination of potential remaining growth. More recent work by Li et al. has provided a system by which to estimate skeletal age based on proximal humeral physeal features. While the fracture itself may confound one’s ability to accurately assess such features, all caregivers of pediatric patients with shoulder conditions should be familiar with the system. Overall, skeletal age information may have value in the management of highly unstable or severely displaced fractures, in which a fixation construct that crosses the physis may be desirable to maintain fracture stability. However, as upper extremity limb length differences are generally not a concern after adolescent fractures, bone age determinations are more relevant to estimating remodeling capacity than concerns about iatrogenic physeal closure.

If elastic stable intramedullary nailing (ESIN) is being considered for internal fixation, a calibrated radiographic assessment of the diaphyseal medullary canal diameter is necessary to select appropriate diameter nails, as achieving approximately 60% to 80% fill with the two implants at the level of the humeral isthmus is a frequently utilized parameter ( Fig. 1.3 ).

Advanced imaging is rarely indicated in the routine assessment of skeletally immature proximal humerus fractures. A CT scan can aid in the identification of complex concomitant bony pathologies that are sometimes seen with higher-energy mechanisms of injuries or pathologic fractures. These include glenoid fractures, glenohumeral fracture/dislocation, significant comminution, and/or neurovascular injury. Alternatively, MRI may provide a radiation-free adjunctive radiologic tool to aid in diagnosis and treatment algorithm for suspected pathologic fractures or suspected soft tissue injury.

Indications and Contraindications

Absolute indications for surgical intervention include open fractures, fractures with impending skin compromise, and fractures with associated or evolving vascular compromise.

Relative indications for surgery remain controversial. Most utilize an age-based algorithm for decision making, with lower thresholds for surgery in patients older than 12 years related to a diminished ability to remodel and inferior outcomes with increased age. Other significant considerations are radiographic translation of fracture fragments (>50%) and, perhaps most importantly, angulation (>40 to 45 degrees), alone. Varus angulation is common, given the strong pull of the rotator cuff sleeve on the proximal fragment. Definitive healing in this position, if excessive, may result in a malunion that limits normal degrees of shoulder abduction.

While uncommon in this population, concurrent glenohumeral dislocation should warrant prompt reduction to preserve blood supply. Possibility of open joint reduction should be anticipated, given the challenge of controlling and providing adequate leverage to the proximal segment with closed reduction.

In the setting of higher-energy trauma or polytrauma, triaging of limb- or life-threatening injuries should be prioritized, requiring expeditious but meticulous secondary surveys and adequate imaging. Polytrauma patients may benefit from operative care to facilitate overall management.

Fracture Reduction

The classic displacement for proximal humerus fractures is apex anterior and varus angulation. In performing closed reduction maneuvers, it is imperative to understand the primary musculotendinous deforming forces acting on the humerus. The distal component is typically internally rotated and adducted, secondary to pectoralis major, latissimus dorsi, and teres major attachments. The proximal component is typically abducted and externally rotated, as a result of the supraspinatus, infraspinatus, and teres minor (rotator cuff) forces. Thus, reduction is most often accomplished by initial abduction, forward flexion, and external rotation of the arm, bringing the distal to the proximal segment, with the addition of axial traction, to disengage the fracture.

Percutaneous Pin Fixation

Percutaneous pin fixation is most often performed with smooth k-wires, though some surgeons may favor threaded k-wires in some situations or fracture patterns. The planned skin incision for pin introduction is marked 5 to 6 cm distal to the anterolateral corner of the acromion to minimize the risk of iatrogenic axillary nerve injury. This corresponds to the described level of the axillary nerve and should be the proximal-most entry point for a lateral pin. Appropriate trajectory of the pin is confirmed with fluoroscopy prior to making an incision. A 1-cm longitudinal skin incision is then made slightly more distal to minimize skin tension. Blunt dissection to bone is undertaken to minimize risk to the axillary nerve and posterior humeral circumflex artery. A slightly broader deep dissection may better accommodate mobilization during imaging and minor adjustments to starting point and trajectory. External rotation during pin placement may further protect the posterior humeral circumflex artery. For distal to proximal pins, these may be safely advanced into the epiphysis, due to the typical brief duration of pin retention ( Fig. 1.5 ). Pins should be advanced to within 5 mm of subchondral bone, with care taken not to penetrate the glenohumeral joint. Alternatively, pins may be directed proximal to distal, with care taken to avoid neurovascular structures inferior to the humeral head and neck. Advancing pins on oscillate may also decrease risk of injury to nearby structures. Construct stability is typically achieved with two divergent or, less commonly, cross pins. Following definitive fixation, we recommend dynamic fluoroscopic assessment to ensure adequate fracture stability throughout and absence of glenohumeral penetration. Any pins appearing to be too long should be withdrawn to appropriate length.

In determining whether pins should be buried or left exposed, this should be considered on an individualized basis, with excessive adjacent soft tissue movement posing greatest threat for pin site infection with exposed pins. We recommend relief of any tension at the skin–pin interface. Buried smooth pins may minimize the incidence of pin migration or pin site infections. With buried pins, it is essential to ensure pins are sufficiently deep to not compromise overlying soft tissue, with the obvious disadvantage of requiring a secondary surgery with anesthesia to remove the pins, whereas pins that are left percutaneously may be removed in the office setting.

Postoperatively, we recommend sling immobilization, with or without a swath component, or a supportive abduction pillow, for 4 to 8 weeks, with adequate fracture stability often obtained after this period due to early healing.

Percutaneous Cannulated Screw Fixation

Although less commonly used, historically, than smooth k-wire fixation, some emerging literature and technique papers have led to increased popularity of screw fixation, which may be particularly suited for older adolescents. The technique is fairly similar to the smooth k-wire technique but involves smaller wires that serve as guidewires for the cannulated drill and screws, which may be fully threaded or partially threaded, with 4.5-mm diameter cannulated screws representing the most commonly utilized size.

Elastic Stable Intramedullary Nailing

ESIN is typically performed retrograde, with two lateral entry nails placed through an entry point proximal to the olecranon fossa. Nail diameter is predicted preoperatively based on the goal of 60% to 80% canal fill at the isthmus. Nail diameter can be additionally confirmed prior to incision by laying the nail over the humerus and radiographically ensuring appropriate canal fill. A 2-cm skin incision is made proximal to the lateral epicondyle of the humerus. Blunt dissection is carried down to bone, which minimizes the risk of injury to the lateral antebrachial cutaneous and radial nerves. The lateral cortex is penetrated obliquely in a distal to proximal direction with a drill or awl, and the first nail is advanced gently to fracture site. Care is taken to avoid perforation of the opposing cortex. A second nail is inserted into an adjacent lateral cortex insertion point and advanced in similar fashion. Under fluoroscopic guidance, the fracture is reduced, and the nails are slowly malleted beyond the fracture site into the proximal fragment and appropriately rotated for divergence, to complement desired alignment and counteract tendency for varus collapse. Attention must be given to avoid fracture overdistraction and ensure the nails do not wind around each other during rotation. Once final fixation has been achieved, dynamic fluoroscopic assessment with the arm in different positions is warranted to confirm fracture and construct stability and to rule out cortical or joint violation. Following satisfactory fixation, nails are cut near their distal cortical insertion point, approximately 5 to 10 mm from the cortex, to minimize adjacent soft tissue irritation and to maintain access for future retrieval.

Antegrade nails are not advocated in skeletally immature patients, as they would have to cross the proximal physis and/or rotator cuff. Medial epicondylar entry points are typically avoided, due to proximity to the ulnar nerve.

Plate Osteosynthesis

Plate osteosynthesis is much less common in skeletally immature patients. Given the need for open approach for fixation, we recommend this be performed in a biologically friendly manner, with emphasis on preservation of periosteum and soft tissue, and care taken with screw fixation to minimize risk of joint penetration and physeal-sparing screw placement.