Anterolateral Approach for an Unusual Pediatric Capitellar Fracture: A Case Report and Review of the Literature

Abstract

A 9-year-old boy sustained a previously unreported salter-Harris III coronal plane fracture of the anterior capitellum after a 20-foot fall from a tree. the fracture was diagnosed on x-ray and an MrI confirmed the fracture pattern. During surgical treatment, an anterolateral approach to the elbow allowed direct visualization of the fracture fragment, anatomic reduction, and fixation with a bioabsorbable pin. At one year follow-up the patient's range of motion and function was symmetric to the contralateral extremity. this paper reviews the literature regarding the epidemiology, classification, and management of the rare pediatric capitellar fracture.

Introduction

Pediatric fractures of the capitellum are rare injuries. These fractures represent not only an injury to articular cartilage but also a potential insult to the physis. When present, pediatric capitellar fractures are often misdiag-nosed and may go untreated^1,2. The resultant malunion may compromise elbow function¹. There is debate over the ideal surgical intervention, with historical opinion recommending excision of the fragment^2,3,4 and more recent reports favoring open reduction and internal fixation^1,5,6,7,8. Fixation methods include smooth Kirschner wires, headless compression screws, lag screws and bioabsorbable pins^8,9,10. We present a case of an anterior capitellar Salter-Harris III fracture in a child that was treated using an anterolateral surgical approach. The parents of our patient consented to publishing the data regarding their son's case.

Case Report

A 9-year-old boy was using a rope to climb a tree when the rope broke at a height of 20 feet. He fell through branches onto a dirt surface landing on his outstretched right hand. He sustained an isolated injury to his right upper extremity. He was evaluated at his local hospital and diagnosed with a distal radial buckle fracture and placed in a splint. His neurovascular exam was normal. He subsequently saw a local Orthopaedic surgeon who noted abnormality of the capitellum on plain films (fig. 1a). His treatment was transferred to our institution 10 days following his injury. An MRI revealed a Salter-Harris III fracture through the capitellum with superior displacement of the anterior fractured fragment (fig. 1b). The remaining posterior portion of the capitellum was intact. The fracture did not extend into the trochlea or the lateral condyle. The patient was treated surgically 2 weeks after his injury with open reduction and internal fixation.

Figure 1. lateral radiograph (1a) and MRI (1b) showing displaced capitellar fragment.

Surgical Technique

General anesthesia was selected and the patient was placed in the supine position. To avoid the posterior blood supply to the humerus and allow direct visualization of the fracture for anatomic reduction, a standard anterolateral approach was performed.

The incision began proximally overlying the lateral aspect of the biceps muscle. It was then directed medially to cross the elbow joint obliquely and then directed back laterally over the proximal forearm (fig. 2). The surgical dissection continued between the biceps and brachioradialis origin. The lateral antebrachial nerve was protected. The radial nerve was identified on the deep surface of the brachioradialis and retracted laterally. Dissection continued distally to the biceps tendon. The brachialis muscle was reflected medially off the distal humeral metaphysis and elevated distally to expose the joint capsule. The capsule was opened longitudinally directly over the displaced fracture fragment. There was a large fracture fragment involving the anterior half of the capitellar ossification center. The fracture line did not enter into the trochlea and the posterior portion of the capitellum was intact. The fragment was reduced under direct visualization and provisionally fixed with an anterior to posterior Kirshner wire. Image intensifier was used to ensure that the physis was not violated and the wire remained entirely within the capitellar ossification center (fig. 3). The wire was exchanged for a 1.5 mm bioabsorbable pin (Trim-It, Arthrex, Naples FL). The elbow was then found to have full passive range of motion with good stability. The skin and subcutaneous layers were closed with absorbable sutures and the elbow was immobilized in neutral rotation and 70 degrees of flexion for 6 weeks.

Figure 2. Incision line used for approach.

Figure 3. Intra-operative image showing reduction of fragment with Kirschner wire which was exchanged for bioabsorbable pin.

Serial post surgical radiographs demonstrated maintenance of reduction and the patient was released to full activities at 3 months (fig. 4). His range of motion at six months showed full pronation, supination and extension with 15 degrees less flexion as compared to the contralateral extremity. At one year, his motion was complete and symmetric to the other side (fig. 5). He had no complaints of pain and his radiographs showed no resorption around the pin or signs of avascular necrosis.

Figure 4. Lateral radiograph 3 months post-op demonstrating healing of the fracture.

Figure 5. Photographs demonstrating symmetric range of motion.

Discussion

The orthopaedic literature on capitellar fractures reflects the infrequency of the injury. The prevalence of this fracture is unknown^11,12. Marion and Faysse reported on 2000 elbow fractures in children and described one capitellar fracture in their series¹³. Current classification is the same for adults and children(fig. 6). Type I is most common and is referred to as the Hahn-Stienthal type. This involves the capitellum and underlying cancellous bone^8,11,12. The Type II, or Kocher-Lorenz is rare in children and is a purely articular fracture with minimal underlying bone attached¹¹. Type III is similar but involves impaction of the capitellar surface with comminution and Type IV is described as a coronal plane fracture which involves a portion of the adjacent trochlea. The described patient sustained a type I fracture.

Figure 6. Capitellum fracture classifcation: type I, Hahn-stienthal type, involves the capitellum and underlying cancellous bone. type II, Kocher-lorenz, a purely articular fracture with minimal underlying bone. Type III involves impaction of the capitellar surface with comminution. Type IV a coronal plane fracture which involves a portion of the adjacent trochlea.

This case report proposes the anterolateral approach for pediatric capitellar fractures. Imtani et. al. published the results of 6 adults with distal humeral coronal shear injuries who were treated with this same approach and internal fixation. They described that the approach allowed excellent visualization for reduction of the fracture and placement of the implants. They showed a good outcome with no neurovascular complications¹⁴. The literature contains multiple reports of related fractures which have been addressed through the extensile lateral approach^{1,5,7,11,12,15,16,17}. For our patient, the decision to use the anterolateral approach was to permit fixation perpendicular to the plane of the fracture while avoiding the growth plate. In addition, the anterolateral approach does not require release of the common extensor origin, allows direct visualization of this type of fracture and avoids the posterior blood supply to the capitellum. Most papers on this topic are in the adult population where the physis and the blood supply may not represent the same concern.

Our nine year old patient is, to our knowledge, the youngest ever reported. His coronal plane Salter-Harris III fracture is previously undescribed and adds to the sparse data regarding this injury. The largest pediatric case series is by Letts et al. who reported on seven adolescent capitellar fractures in a seven year review of fractures at his institution. Five of the patients in his series were treated operatively and all had good results. All of his patients had full pronation and supination but only three of the fve had full fexion and extension as did our patient. The youngest age in the series was 11 with an average of 14.7 years¹⁸. Also, Sodl et al. described a type II injury in a twelve-year-old patient¹¹. Ruchelsman described a case series of 16 adults with fractures of the capitellum treated with operative fxation and reported average ulnohumeral motion arc of 123 degrees and overall 94 % good and excellent results¹⁵.

The infrequency of these injuries can be explained through an understanding of the mechanism and the maturation of the distal humerus. The proposed mechanism involves a sheering injury from the radial head during a fall on an outstretched hand with the elbow extended^4,6,17. The mainly cartilaginous nature of the capitellum prior to age 12 make this fracture less likely and a lateral condyle fracture more likely^2,8. It is thought that increased valgus and hyperextensibility places the elbow at risk for these injuries⁶. Accordingly, examination of our patient's contralateral elbow revealed 5 degrees of hyperextension.

There have been differing opinions in the orthopaedic literature regarding management of capitellar fractures. Historically some authors have proposed excision of the fragment^2,3,4 while others have favored open reduction and fxation ^1,5,6,7,8. Percutaneous reduction with a Stienmann pin has also been proposed¹⁸. The current literature refects the opinion that the Type I and IV fractures are addressed with some form of reduction and fxation while type II and III fractures are treated usually by excision ^5,16,19. There have been case reports of successful treatments of type II fractures as mentioned above¹¹. Historic and recent papers agree that malunion of the fracture fragment severely impacts elbow function^1,3,4.

The authors propose the anterolateral approach as an alternative exposure for capitellar fractures. The approach is limited in that it is not extensile and requires a plane of dissection much closer to the important neurovascular structures in the elbow. Further use of the anterolateral approach and comparison with the extensile lateral approach would be benefcial.

Conclusion

Although rare, capitellar fractures can be seen in children as young as 9 years old. In our case, the anterolateral approach allowed excellent visualization of the fracture facilitating anatomic reduction and internal fxation without violation of the physis. The authors recommend consideration of an anterolateral approach for selected pediatric capitellar fractures.