Reduction and Percutaneous Pin Fixation of Displaced Supracondylar Elbow Fractures in Children

1. Introduction
   
2. Historical Perspective
   
3. Indications/Contraindications 
   
4. Preoperative Planning
   
5. Technique
   
6. Results
   
7. Complications
   
8. Postoperative Management
   
9. Summary
   
10. Acknowledgements
    
11. References

Introduction

Supracondylar fractures of the humerus comprise 17% of all childhood fractures with a peak age incidence of approximately 6 years[1],[2]. Supracondylar fractures are also the most common fracture resulting in admission to the hospital in the age 4 to 7 year range. The nonoperative management of displaced supracondylar fractures of the humerus has historically been associated with a high rate of complications including failure to obtain and maintain reduction, nerve injury, vascular compromise, and compartment syndrome. The past 3 decades have witnessed the evolution of improved methods for maintaining reduction of displaced fractures with a variety of pin configurations utilizing both open and percutaneous pinning techniques.

Standardization of surgical approaches, including techniques for obtaining reduction and for performing pin fixation with radiographic control, has markedly reduced the incidence of poor outcomes in the management of displaced supracondylar humerus fractures. The incidence of iatrogenic nerve injury has been demonstrated to vary considerably depending both on the pin configuration (crossed pinning vs. lateral pinning) and the operative technique (percutaneous, mini-open, open) used for placement of medial pins. While there is general consensus that the management of supracondylar humerus fractures associated with open wounds or vascular injury constitutes a surgical emergency, it has recently been recognized that the majority of closed displaced supracondylar humerus fractures may be treated in a delayed fashion within 24 hours of injury without compromising long-term results.

Cubitus varus resulting from inadequate reduction or failure to maintain reduction has long been considered a strictly cosmetic problem. Recent literature suggests that cubitus varus may have other delayed consequences including increased risk of late lateral condyle fracture, tardy ulnar nerve palsy, and posterolateral rotary instability of the elbow.

This article will review the indications for percutaneous pin fixation of displaced supracondylar humerus fractures in children, our current surgical treatment algorithm, and techniques, outcomes, common complications, and current controversies in surgical management.

Historical Perspective

Supracondylar humerus fractures are broadly classified into extension-type and flexion-type depending upon the position of the distal fragment. Extension-type fractures comprise approximately 99% of all supracondylar fractures and are the subject of this article[2]. The most widely accepted and clinically useful classification system, devised by Gartland in 1959, is still used to describe extension-type supracondylar humerus fractures based on the degree of displacement of the fracture[3]. Type I fractures are non-displaced, type II are displaced with an intact posterior cortex, and type III are completely displaced without cortical contact. Extension-type supracondylar humerus fractures may also have other associated injuries including ipsilateral fracture (1%), open fracture (1%), compartment syndrome (0.5%), nerve injury (7.7%), and vascular insufficiency (2–4%) requiring operative intervention[4].

Treatment of displaced supracondylar fractures has included closed reduction and casting in hyperflexion, traction, and both open and closed reduction and pinning. The goal of all forms of treatment is the same: to obtain and maintain an anatomic reduction of the distal humerus with the lowest possible risk of nerve injury, compartment syndrome, or late displacement.

Closed reduction and casting may be contraindicated in the setting of significant displacement and elbow swelling. Hyperflexion beyond 120 degrees is typically required to maintain a closed reduction[5], and this amount of flexion with increased pronation of the elbow may result in decreased brachial artery blood flow, increasing the risk of compartment syndrome[6]. There is recognition that closed reduction and cast application is associated with both a greater incidence of cubitus varus and compartment syndrome compared with all other forms of treatment[7].

Although both skin traction and skeletal traction prior to cast application have been used for management of supracondylar fractures, traction is now largely of historical interest. In a retrospective comparison between skeletal traction and percutaneous pin fixation for displaced supracondylar humerus fractures, skeletal traction resulted in an unacceptable 33% incidence of cubitus varus compared with a 5% incidence with percutaneous pin fixation[8].

The high rates of complications associated with both cast and traction treatment led to the evolution of current techniques of percutaneous pinning for these difficult fractures. The use of percutaneous pinning as an alternative to closed reduction and casting or traction dates back over 50 years. Swenson described percutaneous “blind” pinning with cross pins using Kirshner wires once closed reduction was verified radiographically[9]. While warning about the risk to the ulnar nerve with the medial pin, he cited the advantages of this technique including easier management of extensively swollen elbows, avoidance of prolonged immobilization, better maintenance of reduction, and decreased risk of Volkmann ischemia.

Several authors have presented large series documenting the efficacy and advantages of percutaneous pinning over other methods for management of displaced supracondylar humerus fractures[7],[10],[11],[12],[13]. Flynn presented a series of 52 displaced supracondylar humerus fractures treated with crossed “blind pinning” with 98% satisfactory results, minor neurologic complications, and no Volkmann contractures[14]. An alternative pin construct utilizing 2 lateral pins was described by Fowles in 1974 with results equivalent to crossed pinning[11]. More recently, Cheng reviewed 180 type III fractures and found that both cross pinning and lateral pinning were equally effective with low rates of complications[12].

Current discussion about the management of displaced supracondylar humerus fractures centers around optimal stability of pin constructs[15],[16], risk to the ulnar nerve with crossed pins[17],[18],[19],[20],[21],[22],[23], timing of reduction (urgent vs. emergent)[24],[25],[26],[27], and long term impact of residual cubitus varus (risk of refracture[28],[29], tardy ulnar nerve palsy[30],[31],[32],[33], and posterolateral instability of the elbow[34],[35]).

Indications/Contraindications

Type I fractures are best managed by cast or splint immobilization in 90 degrees of elbow flexion and neutral forearm rotation. Most type II and type III supracondylar humerus fractures are best managed with closed reduction and percutaneous pin fixation. In one large series of 862 supracondylar humerus fractures, the indications for open reduction included the following: irreducible fracture (71%), vascular compromise (24%), open fracture (12%), and post-reduction nerve palsy in 1 patient[36]. The indications for open reduction may be viewed as contraindications to closed reduction and percutaneous pinning.

Careful history and physical examination will reveal the presence of a supracondylar humerus fracture. The mechanism of injury is frequently a fall from a height onto an outstretched hand[1],[37]. The typical child presents with a swollen elbow and refusal to use the affected extremity. Swelling and deformity are relatively greater in the type III fractures. The S-shaped deformity of the elbow is characteristic of a displaced fracture (Fig. 1).

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FIGURE 1. S-shaped clinical appearance of the distal humerus (A). Lateral radiograph of the elbow in this same patient demonstrates a fracture of the distal humerus with displacement (B). Note the ecchymosis over the anterior aspect of the distal humerus.

The anterior “pucker sign” with anterior ecchymosis and tethering of the skin may indicate trauma to the brachialis muscle and potential entrapment of the neurovascular bundle necessitating open reduction[38].

The mechanism of injury for supracondylar humerus fractures is related to the natural ligamentous laxity occurring in children in the peak affected age range of 4 to 7 years[39]. Ligamentous laxity permits elbow hyperextension with axial loading of the upper extremity. The olecranon is forced into the posterior fossa of the humerus acting as a fulcrum. With sufficient force, the weak metaphyseal bone of the distal humerus fails, resulting in the classic extension-type supracondylar humerus fracture.

Physical examination must include a global survey, evaluation for additional ipsilateral injuries, and a specific neurologic and vascular examination of the affected extremity. This can be quite difficult in a young patient with a subtle neurologic deficit or with significant pain and swelling. The sensory examination must include specific assessment of median, ulnar, and radial nerve sensation. Motor evaluation should include specific assessment of radial nerve (finger, wrist, and thumb extension), anterior interosseous nerve (index distal interphalangeal and thumb interphalangeal flexion), median nerve (thenar function), and ulnar nerve (interossei function)[4]. Although some literature has suggested that the radial nerve is the most commonly injured nerve associated with supracondylar elbow fractures, Campbell found that the specific nerve injury seems to be associated with the direction of displacement of the distal fragment[40]. Posteromedial displacement is associated with radial/posterior interosseous nerve injury, and posterolateral displacement is associated with median/anterior interosseous nerve injury. Others have found that the anterior interosseous nerve is overall the most commonly injured nerve, but it is often overlooked since it results in motor loss exclusively[41].

The presence or absence of a radial pulse, the color and temperature of the hand, and capillary refill should all be noted. It is also important to document the compressibility of the forearm, especially the volar compartment, and the presence or absence of pain with passive finger flexion and extension[4]. Care must be taken to evaluate the patient for associated ipsilateral extremity fractures. The presence of an ipsilateral forearm fracture is an indication for surgical management and pin fixation of both fractures since compartment syndrome is a high risk and circumferential cast immobilization is contraindicated[42],[43],[44].

Preoperative Planning

After the initial examination of the patient and the affected arm, the injured elbow should be splinted in approximately 20 to 30 degrees of flexion prior to closed reduction in the operating room. In a well-perfused extremity with significant displacement and tenting of the skin, a partial reduction may be indicated in the emergency room followed by splinting in 20 to 30 degrees of flexion if surgical management is to be delayed overnight[27]. Splinting the elbow in full extension should be avoided, as this may further stretch the neurovascular bundle over the distal humerus metaphyseal spike[45]. Assessment of the carrying angle of the contralateral upper extremity should be noted, as this is a useful clinical indicator of adequate reduction in the operating room. Note should be made of the wound status (open vs. closed), neurovascular status, degree of deformity (carrying angle, S-shaped deformity), and clinical risk factors for difficulty of reduction (“pucker sign” and anterior ecchymosis).

Complete radiographic imaging of the involved extremity is necessary to rule out ipsilateral injury and to confirm the specific diagnosis. True anteroposterior (AP) and lateral x-ray images of the distal humerus are mandatory with the x-ray beam perpendicular to the distal humerus on both views (Fig. 2).

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FIGURE 2. AP (A) and lateral (B) radiographs reveal the true degree of extension and rotational deformity in this type III completely displaced supracondylar humerus fracture.

Care should be taken to avoid external rotation of the distal humerus while attempting to obtain the lateral X-ray, since external rotation of the arm may result in further displacement and angulation at the fracture site. A true lateral radiograph is best obtained with the shoulder in neutral rotation and the x-ray plate placed between the elbow and the patient’s thorax. Application of a splint prior to imaging increases comfort and cooperation by the patient and may facilitate appropriate imaging studies. Direct supervision of the radiology technician may be necessary.

The AP and lateral radiographs of the distal humerus are usually sufficient to confirm the diagnosis and to classify the fracture using the Gartland classification[3]. Occasionally two oblique radiographs of the distal humerus are required to visualize minimally displaced fracture lines through the medial or lateral columns. The posterior fat pad sign is a sensitive indicator of a joint effusion, which suggests a minimally displaced intracapsular elbow fracture. Displacement of the anterior fat pad also indicates a joint effusion. The anterior and posterior fat pads are seen on the lateral radiograph. A positive posterior fat pad sign is predictive of an occult fracture in 76% of cases in the setting of negative initial bony radiographs. In one large prospective study of children with a history of trauma and positive fat pad sign on otherwise negative elbow X-rays, over 50% of these fractures were non-displaced supracondylar humerus fractures[46].

The AP radiograph provides information regarding direction of displacement of the distal fragment (medial/ lateral), rotation (most commonly internal with posteromedial fractures), and angulation (varus/valgus). Varus angulation is assessed on the AP radiograph by measuring Baumann’s angle and comparing this to the opposite side. Baumann’s angle is the angle described by the intersection of the humerus axis and a line drawn along the growth plate of the lateral condyle of the elbow (Fig. 3).

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FIGURE 3. Baumann’s Angle (B) is the angle measured between the humerus axis and a line drawn along the growth plate of the lateral condyle. Increase in Baumann’s angle of 5 degrees or more compared with the opposite side is correlated with poor cosmetic outcome and varus deformity.

This angle correlates with the carrying angle of the elbow, and excess varus angulation (increased Baumann’s angle) correlates with a poor clinical outcome. A difference of 5 degrees or more is generally regarded as significant compared with the opposite side[47]. In one large prospective study involving 577 pediatric elbow radiographs, Baumann’s angle was shown to have no significant differences between sexes or at different ages, with an average value of 74 degrees in boys and 76 degrees in girls[48]. The measurement of Baumann’s angle, however, has significant variability and decreased reliability with increasing internal or external rotation of the distal fragment[49].

The lateral X-ray demonstrates the degree of angulation and displacement of the distal fragment and is used to classify the fracture based on the Gartland classification system (Fig. 4)[3].

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FIGURE 4. A. Gartland type I non-displaced fracture with large intraarticular effusion, as seen by elevation of the anterior fat pad and visualization of the posterior fat pad (arrows). B. Gartland type II fracture with minimal posterior displacement. C. Gartland type III fracture with complete displacement.

Although historically 75% of displacement in type III fractures is posteromedial[4], other studies have demonstrated nearly equal rates of posteromedial and posterolateral displacement[40].

The status of the anterior humeral line as seen on the lateral radiograph is a useful sign for significant displacement of the fracture (Fig. 5). The anterior humeral line demonstrates the anatomic relationship between the distal humerus and the unfused ossification center of the capitellum, a portion of the distal humerus.

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FIGURE 5. A. The anterior humeral line lies anterior to the capitellum in this type II extension fracture. B. The anterior humeral line bisects the capitellum postoperatively following closed reduction and pin fixation, indicating satisfactory anatomic reduction.

The anterior humeral line should pass through the middle third of the ossified capitellum on the lateral radiograph[50]. When the anterior humeral line is anterior to the capitellum, this suggests significant extension deformity and posterior displacement of the distal supracondylar fragment. The reliability of the anterior humeral line depends upon obtaining a true lateral radiograph, and rotation of the distal fragment

may result in a false positive radiographic finding[51]. In clinical practice, the most useful radiographic measurements both prior to reduction and post-reduction include Baumann’s angle, location of the anterior humeral line, and restoration of the anatomy of the olecranon fossa[45].

While plain radiographs are usually sufficient to confirm the diagnosis, arthrography may be helpful in unusual situations to rule out minimally displaced lateral condyle or T-condylar fractures. MRI and ultrasound may also play a role in the identification of intraarticular fractures in young children with minimal ossification of the distal humerus[50]. These imaging modalities are especially helpful in the setting of nondisplaced fractures and when the regional growth centers have not yet begun to ossify, making them unable to be seen on regular X-rays. Magnetic resonance angiography is also useful in evaluation of potential injury to the regional vascular structures in the setting of significantly displaced fractures.

The technique for closed reduction and percutaneous pinning described in the following section is a distillation of current best practices and the authors’ preferred method. Technical requirements are minimal but include good fluoroscopic imaging, appropriate smooth stainless steel pins, and knowledge and ability to perform open reduction and vascular exploration and repair as needed. It is a good idea to notify the appropriate consulting services (hand or vascular surgery) when a type III supracondylar fracture initially presents with vascular compromise, since intraoperative consultation and vascular repair may be indicated if perfusion is not rapidly restored following attempted closed reduction.

Technique

The treatment of a closed type II or type III supracondylar humerus fracture with a well perfused extremity is considered an urgent rather than emergent surgical problem[25],[27]. The patient should be taken to the operating room for closed reduction and pin fixation as quickly as possible, but delay in treatment of 8 to 24 hours does not increase the rate of complications or poor outcome. The child is placed supine on a regular operating room table with the shoulder of the patient positioned at the edge of the table. The image intensifier is brought into position from the direction of the patient’s head, parallel to the operating room table, so that the C-arm base serves as the operating room table for the procedure (Fig. 6).

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FIGURE 6. A. Typical operating room setup with the image intensifier serving as the operating table. B. After radiographic evaluation, the image intensifier is draped into the operative field.

The arm is prepped and draped up to the shoulder, and the image intensifier is draped into the surgical field.

Closed reduction is performed in stepwise manner with minor modification of Rang’s technique[52]. Longitudinal traction is applied to the forearm while countertraction is applied to the proximal humerus. Posterior translation of the distal fragment may be corrected as the fragments disengage. An AP image is obtained at this point, and appropriate force is applied to the distal fragment to correct medial or lateral translation. If internal rotation of the distal fragment is present, this is corrected. Reduction of the extension deformity is performed with flexion of the elbow to 120 degrees while the surgeon applies an anteriorly directed force to the olecranon with both thumbs[39]. The direction of displacement of the distal fracture fragment determines the position of the forearm. The forearm is held in pronation for posteromedial fractures and supination for posterolateral fractures[53]. At this point the elbow is flexed at least 120 degrees and the forearm is placed in the position of greatest stability (pronation vs. supination). The reduction is assessed with both AP and lateral images using the image intensifier. The Jones view as well as a 10-degree internal and external oblique AP view helps to visualize the medial and lateral columns as well as the anatomy of the olecranon fossa. If an anatomic reduction is achieved on the AP image, a lateral radiograph is obtained by externally rotating the shoulder. The anterior humeral line should pass through the middle third of the capitellum on the lateral view.

Once anatomic reduction is confirmed, percutaneous lateral pin fixation is performed under radiographic control. The lateral elbow entry point is confirmed using the AP image, and in the setting of severe swelling the entry point is also confirmed on the lateral image. Two parallel or slightly divergent lateral K-wires are inserted percutaneously (Fig. 7).

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FIGURE 7. AP (A) and lateral (B) X-rays demonstrating optimal lateral pin fixation for a type II fracture. The lateral pins should be parallel or divergent, and at least 1 cm apart at the fracture site.

One of the lateral pins generally engages the ossified center of the capitellum and passes proximally up the lateral column and engages the medial cortex of the humerus at least 1 cm above the fracture site. In many cases the second pin traverses the olecranon fossa prior to engaging the medial column above the fracture site. Care is taken to maintain approximately 1 cm spread between the pins and to avoid pins crossing at the fracture site to maintain maximal construct strength[7]. Optimally, the pins should be parallel or divergent. Once two lateral pins have been placed, the elbow is extended and the adequacy of reduction is assessed with AP and lateral images. Stability of reduction is assessed with dynamic fluoroscopic assessment of range of motion[19]. If the fracture is deemed unstable, either a third lateral pin or a medial pin is placed. Clinical assessment of the elbow carrying angle should also be performed at this point as confirmation of radiographic findings. The carrying angle of the elbow in extension should be identical to the opposite side.

Placement of a medial pin requires meticulous surgical technique to avoid the iatrogenic risk of ulnar nerve injury that occurs up to 8% of the time in some series[22]. The elbow is always taken out of the hyperflexed position for medial pinning since hyperflexion has been demonstrated to put the ulnar nerve at risk. In children with documented hyperlaxity, the rate of ulnar nerve anterior subluxation approaches 72% and true ulnar nerve dislocation rate is up to 25% with elbow flexion[54]. Since the fracture is already provisionally stabilized with two lateral pins, the elbow is extended to 50–70 degrees of flexion and the arm is externally rotated 90 degrees. A 1–1.5 cm skin incision is made obliquely over the medial epicondyle, and dissection is carried down to periosteum of the medial epicondyle. In our series of 65 cross pinnings[55], the ulnar nerve was encountered only once during exposure of the medial epicondyle. Direct exposure of the ulnar nerve is neither necessary nor desirable. Lateral fluoroscopic imaging may be used to confirm the posterior to anterior direction of the medial pin, which is placed directly through the center of the medial epicondyle. Others have described “blind” pinning of the medial side without an incision while simultaneously pushing the ulnar nerve posteriorly, and/or pinning of the medial side first with the elbow in flexion[4]. We do not recommend either of these methods because of the risk of injury to the ulnar nerve. We generally place the medial pin 5 mm posterior to the 1.5 cm medial wound to facilitate wound closure, but closure of the wound around the pin is acceptable. The pins are cut, bent, and dressed with xeroform outside the skin.

The radial pulse and perfusion of the hand should be reassessed at this point with the elbow in the planned position of immobilization. The arm is then placed in a bivalved long arm cast with the elbow flexed 90 degrees and the forearm in neutral rotation.

If the fracture is not reducible with three attempts at closed reduction with image guidance, the fracture is deemed irreducible and we proceed to open reduction. Further attempts at closed reduction may result in further soft tissue damage, swelling, and potential damage to neurovascular structures. Soft-tissue which may block reduction includes the brachialis muscle, periosteum, nerves, or brachial artery.

Results

Long-term follow-up studies have reported satisfactory outcomes from closed reduction and percutaneous pinning for displaced supracondylar elbow fractures in children. Flynn’s classic report in 1974 of 52 patients described 98% satisfactory results with closed reduction and “blind” percutaneous crossed pin fixation[14]. Only one patient had a poor outcome with a carrying angle greater than 15 degrees of varus, and this was attributed to pinning of the distal fragment in varus rather than loss of reduction. Two other patients had loss of reduction attributed to poor pin placement. One patient had a transient sensory ulnar neuropathy attributed to ulnar nerve injury from a medial pin.

In 1974, Fowles and Kassab reported on another large series of 80 children with long-term follow-up all treated by closed reduction and fixation with two lateral pins[11]. They reported satisfactory results in all but two cases with severe stiffness attributed to unrecognized infection in one case and prolonged 8-week immobilization in another case. However, seven patients had “fair” results secondary to varus deformities with carrying angles between 10 and 20 degrees. It was not reported whether the varus deformities resulted from inadequate initial reduction or late loss of reduction in the postoperative period.

In 1988, Pirone retrospectively reviewed outcomes of management of four different treatment methods in 230 children treated at one institution[7]. The highest percentage of excellent results (78%) was associated with closed reduction and percutaneous Kirshner-wire fixation. Both crossed pinning and lateral pinning were used in this series, and there were no neurologic injuries attributed to the pinning techniques. Closed reduction and cast application was associated with a significantly lower percentage of excellent results (51%). There was only one case of postoperative Volkmann ischemic contracture, and this was in the closed reduction and cast immobilization group.

More recent reviews of closed reduction and percutaneous pinning of displaced supracondylar fractures have consistently demonstrated 92–98% satisfactory results based on Flynn criteria[12],[13],[19],[23]. Very few poor results have been identified in these studies, and the few avoidable complications resulting from treatment were primarily iatrogenic nerve injuries and loss of reduction. The issue of pin placement, fracture stability, and iatrogenic nerve injury remains controversial, and recent studies have emphasized the trend toward increasing efforts to protect the ulnar nerve either utilizing a mini- open medial incision or placing lateral pins[22].

Timing of surgical management of supracondylar humerus fractures has received significant attention. While displaced supracondylar humerus fractures have traditionally been managed as surgical emergencies, several authors have demonstrated that an overnight delay in the surgical management of displaced supracondylar humerus fractures is both safe and prudent[24],[25],[26],[27]. If a surgeon opts for delayed treatment of a displaced fracture, the extremity should be elevated and splinted in 20 to 30 degrees of flexion, and the patient should be admitted to the hospital for frequent neurovascular checks. The advantages of delayed surgical management include the availability of experienced operating room staff and equipment. These studies have demonstrated no differences in terms of outcomes or perioperative complications between the emergent and delayed treatment groups. It should be noted that there are several well- recognized contraindications to delayed surgical management of displaced supracondylar humerus fractures including open fracture, vascular compromise, and ipsilateral extremity fracture[27].

Complications

Complications resulting from displaced supracondylar humerus fractures include acute or delayed vascular impairment, nerve injury, and loss of reduction. This section focuses on the complications that stem from treatment choices rather than the injury itself.

The incidence of vascular impairment is between 12% and 19% in type III supracondylar humerus fractures[40],[56],[57],[58]. Vascular impairment is recognized by diminished pulse, coolness, and pallor of the hand[59]. Injury to the brachial artery is most often a consequence of the injury itself rather than a complication of treatment. Etiology for vascular injury includes tethering of the brachial artery or its supratrochlear branch over fracture fragments leading to thrombosis or spasm, and laceration, intimal tear, or entrapment of the artery between fracture fragments. Most brachial artery injuries occur in association with posterolateral displacement of the distal fragment, presumably as the artery is stretched over the metaphyseal spike of bone[40]. Approximately 80% of the time the pulse is restored after emergent closed reduction and pin fixation of the fracture[57],[59]. If the pulse does not return with closed reduction, then open arterial exploration should be performed. Both Shaw and Copley recommend open exploration in the rare circumstances in which a previously well-perfused extremity loses the radial pulse following closed reduction and pinning. Controversy still exists regarding best management of the extremity with a pink, warm, well-perfused hand with an absent pulse following reduction. Some have recommended observation without any intervention since the pulse returns spontaneously in most cases[60].

Historically, supracondylar humerus fractures are the fracture most closely associated with compartment syndrome and Volkmann contracture[61]. Volkmann contractures have been demonstrated to result from closed reduction and cast immobilization specifically, and not from traction or closed reduction and pin fixation[7]. Since Flynn’s report in 1974, none of the large series of displaced supracondylar fractures has reported Volkmann contractures following closed reduction and pin fixation[14]. Compartments should be evaluated in every case prior to and after reduction, and pressures should be measured based on clinical suspicion, especially in the setting of a crush injury or arterial injury.

The incidence of nerve injury associated with displaced supracondylar humerus fractures is between 10 and 20% in several modern studies[12],[13],[19],[23]. While the radial nerve has been noted to be the nerve most commonly injured, recent literature has brought attention to anterior interosseous nerve injury[14],[40],[62],[63],[64]. Several recent studies suggest that the anterior interosseous nerve in is fact the most commonly injured nerve, representing between 40% and 50% of nerve injuries in supracondylar fractures[41],[65]. Most nerve injuries recover spontaneously within 2 to 6 months[18],[41],[56]. Routine nerve exploration is recommended if there is no recovery by 3 months, or if nerve function deteriorates following closed reduction and pin fixation[50].

Iatrogenic nerve injury almost always involves the ulnar nerve following placement of the medial pin for crossed pin fixation. The reported incidence of iatrogenic ulnar nerve injury with crossed pinning is between 0% and 8% in several large studies[17],[18],[19],[20],[21],[23],[55],[56]. Technical factors that increase the risk of ulnar nerve injury during medial pinning include “blind” pinning and medial pinning with the elbow in hyperflexion. Generalized ligamentous laxity increases the likelihood of ulnar nerve subluxation or dislocation anteriorly, thus increasing risk of injury to the ulnar nerve with medial pinning in hyperflexion[54]. The nerve may be injured by stretch over the medial pin[21], direct penetration of the nerve, anterior fixation of the ulnar nerve over the medial epicondyle[67], and laceration of the nerve[68]. Large series of ulnar nerve injury following medial pin fixation have demonstrated spontaneous nerve recovery by 4 to 6 months postoperatively[20],[21]. Permanent nerve injury following medial pin fixation has been reported rarely[67].

Cubitus varus results either from inadequate initial reduction or from late coronal plane angulation of the distal fragment during healing. The incidence of cubitus varus has diminished significantly since the era of routine pin fixation for displaced fractures[7],[14]. Inadequate initial reduction is avoidable with high quality intraoperative imaging and clinical evaluation of the extremity in extension in the operating room after pin fixation. Late angulation and loss of reduction does occur, and in one series of 87 children, late displacement occurred in 2% of fractures stabilized with crossed pins and 28% of fractures stabilized with two or three lateral pins (Fig. 8)[69].

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FIGURE 8. Late angulation and loss of reduction is associated with poor pin placement. Initial AP and lateral radiographs (A and B) demonstrate anatomic reduction. AP and lateral radiographs (C and D) 1 week later demonstrate loss of reduction secondary to inadequate distance between the pins.

Biomechanical studies have also demonstrated that cross pinning is more stable than lateral pinning in rotational testing as well as varus and valgus loading[15],[16]. Despite these facts, several large series have demonstrated no clinical difference in stability between crossed and lateral pins[12],[19],[66],[70]. The issues of fracture stability and risk to the ulnar nerve frame the debate between advocates of lateral pinning and cross pinning. We support the recommendations outlined by Gordon et al[19]: Type II fractures are stabilized with two lateral pins. Type III fractures are initially fixed with two lateral pins, and if the fractures are unstable on dynamic fluoroscopic assessment, then a medial pin is placed.

Historically, cubitus varus was considered a cosmetic deformity. However, review of the recent literature has identified several late complications of cubitus varus including posterolateral rotary instability of the elbow[34],[35], tardy ulnar nerve palsy[31],[32],[33], and secondary lateral condyle fracture[28],[29].

Postoperative Management

Following closed reduction, pinning, and application of a bivalved long arm cast in the operating room, the child is admitted to the hospital overnight for neurovascular monitoring and elevation of the affected extremity. The arm is suspended by a stockinette sling attached to an IV pole positioned by the contralateral shoulder to maintain the shoulder in internal rotation. Patients are typically discharged 24 hours later with a sling, and followup is weekly with AP and lateral radiographs in the cast. The cast is removed three weeks postoperatively and pins are removed in the office. Parents are instructed in active elbow range of motion exercises and patients are permitted unrestricted elbow motion out of the cast. In general patients return to full activities at 6 weeks from the date of injury. Length of cast immobilization may be increased to 4 weeks in the setting of open fractures, open reduction, or children age 10 or older.

Summary

Supracondylar humerus fractures comprise up to 32% of inpatient hospital admissions for fracture in the age 4 to 7 year range[71]. Standardized treatment algorithms have yielded predictably good results. Most closed type II and type III extension supracondylar fractures may be managed urgently as opposed to emergently with closed reduction and percutaneous pinning in the operating room within 24 hours[24],[25],[26],[27]. Indications for open reduction include irreducible fractures, associated vascular compromise, open fracture, and post-reduction nerve palsy[36]. Stable fixation may be achieved with two lateral pins, but a medial pin may be necessary for management of unstable fractures. Medial pin fixation places the ulnar nerve at risk unless specific precautions are taken to protect the nerve. Our recommendations to increase safety of medial pin placement include the following:

(1) Pin the medial side in relative extension after provisional fracture stability is obtained with two lateral pins,

(2) Use a 1.5 cm incision over the medial epicondyle for placement of the medial pin[55]. Current techniques for reduction and pinning of displaced supracondylar humerus fractures have resulted in excellent functional outcomes with low rates of complications.

Acknowledgements

The authors thank Daniel W. Green, MD, FACS, FAAP, and the Department of Radiology and Imaging for the generous use of their images (Figs. 1A and 8A–D).

References