Type IV capitellum fractures in children

Abstract

Capitellum fractures represent 1% of elbow fractures. A coronal shear fracture which involves the trochlea is classified as a type IV McKee fracture. The combination of its rarity in the paediatric population as well as its unique appearance on X-ray make diagnosis of this fracture a challenge. We present the case of a 14-year-old boy who sustained this fracture falling from his bike. It was diagnosed from the double arc sign on X-ray. In addition, a CT scan was obtained to aid preoperative planning. It was treated by open reduction and fixation with two headless compression screws. Follow-up at 6 months showed no avascular necrosis. The patient could achieve full extension, while flexion was reduced only by 5°. Final follow-up was conducted at 15 months. Anatomic reduction and stable internal fixation are essential for a good outcome in these uncommon paediatric fractures.

Background

True capitellum fractures are rare in the paediatric population and have been reported as 1 in 2000 paediatric elbow fractures.¹ As a result, they can potentially be overlooked when presenting at a paediatric hospital where capitellum fractures usually involve part of the metaphysis, constituting the relatively frequent lateral condyle fractures. We reported this case to alert paediatric departments regarding the diagnosis and treatment of this fracture.

Case presentation

A 14-year-old boy presented to the emergency department of our paediatric hospital after falling off his bicycle onto his outstretched left dominant arm. His elbow was swollen and he had restricted extension and flexion. The arm was neurovascularly intact.

Investigations

Initial X-ray revealed a double arc sign evident on the lateral view (figure 1) described by McKee et al ² which is pathognomnic of a type IV capitellum fracture in the modified Bryan and Morrey classification.² However, this sign is not always present.^{3 4} On the anteroposterior view X-ray the fracture is not clearly evident (figure 2). A CT scan was obtained to further characterise the injury (figures 3 and 4). CT also revealed an undisplaced medial epicondyle fracture which did not need treatment (figure 3).

Figure 1.

Initial fracture lateral X-ray depicting double arc sign. Olecranon has not yet fused.

Figure 2.

Initial fracture anteroposterior view X-ray. The fracture is not clearly evident in this view. Medial epicondyle has not yet fused.

Figure 3.

CT scan three-dimensional reconstruction antepsoterior view depicting fractured capitellum and trochlea. Medial epicondylar fracture is also evident.

Figure 4.

CT scan three-dimensional reconstruction lateral view depicting capitellum coronal shear as well as detachment of lateral epicondyle.

Treatment

The fracture was treated 4 days post injury to allow the organisation of a CT scan and the order and arrival of the fixation material which was then not available at our institution, in this case, headless compression screws. While awaiting surgical treatment, the patient was discharged with an above elbow half cast and a prescription for paracetamol by mouth. In theatre, an above-elbow tourniquet was applied. An extended lateral approach was performed with anterior detachment of the extensor mechanism. Homann retractors were placed at each side of the distal humerus. The articular surface was visualised anteriorly, and the fracture was reduced with the aid of a reduction clamp. Two headless compression screws were inserted from anterior to posterior, their threads buried in the capitellum. A percutaneous k-wire was inserted laterally to stabilise the lateral epicondyle to the capitellum evident in the 2 week post op X-rays (figures 5 and 6). The patient was discharged 1 day postoperatively, with an above-elbow half cast. Indomethacin was prescribed at a dose of 25 mg two times per day for the prevention of heterotropic ossification, for the duration of 4 weeks. At 3 weeks postoperatively, the k-wire was removed at the outpatient clinic, and a hinged elbow brace was applied allowing progressive mobilisation. It was removed 6 weeks postoperatively allowing for full mobilisation. The fracture was healed at that time.

Figure 5.

Two weeks postoperative X-ray anteposterior view.

Figure 6.

Two weeks postoperative X-ray lateral view.

Outcome and follow-up

The patient was followed up initially 6 months postoperatively. There was no radiological evidence of avascular necrosis (figures 7 and 8). He had returned to full activities. He had a range of motion of 0°–135° with a deficit of 5° of flexion compared with the uninjured side (figures 9 and 10). He did not have any complaints. Final follow-up was conducted at 15 months. Patient was asymptomatic and X-rays did not reveal avascular necrosis (figures 11 and 12). By that time, he had achieved full flexion.

Figure 7.

Six months postoperative X-ray anteroposterior view showing healing and no evidence of avascular necrosis. Medial epicondyle has fused.

Figure 8.

Six months postoperative X-ray lateral view showing healing and no evidence of avascular necrosis. Olecranon has fused.

Figure 9.

Patient review 6 months postoperative elbow extension.

Figure 10.

Patient review 6 months postoperative elbow flexion.

Figure 11.

Patient review 15 months postoperative X-ray anteroposterior view. No evidence of avascular necrosis.

Figure 12.

Patient review 15 months postoperative X-ray lateral view. No evidence of avascular necrosis.

Discussion

Capitellum fractures, in particular type IV McKee fractures are especially rare in the paediatric population. They can also be associated with ligamentous injuries (lateral or medial collateral ligament lesions) or ipsilateral fractures (radial head fractures or epicondylar fractures of humerus).^5–9 The original paper by McKee et al ² reports six type IV fractures including paediatric patients, treated by Open Reduction Internal Fixation (ORIF). One of these developed post-traumatic osteoarthrosis. Mean follow up (FU) was 22 months and mean range of motion (ROM) was 15°–141°. A recent case series reported six type IV fractures in adolescents treated with fully threaded compression screws and posteroanterior placement. These patients achieved full functional recovery, and none of them developed avascular necrosis. Mean FU was 24.6 months and mean flexion extension arc was 135°.¹⁰ Another small case series reported one 15-year-old patient with a type IV fracture treated by partially threaded 4 mm cancellous screws placed from posterior to anterior.¹¹ A 16-patient case series of both paediatric and adult patients included 8 type IV capitellum fractures, treated with acutrak screws. In this series, four patients developed post-traumatic arthrosis and six heterotropic ossification. Mean FU was 27 months and mean flexion extension arc was 10°–133°.⁴ A case series of 15 patients of both adults and adolescents included 3 type IV fractures. These were treated with fine threaded k-wires. In this series, eight patients developed post-trauma arthrosis. At a minimum of 12 months FU, they had a mean flexion extension ROM of 124°.¹² Finally, there was one case report of a type IV fracture in a 9-year-old girl with a bony avulsion of the lateral collateral ligament. It was treated by headless compression screws from anterior to posterior, and the associated injury was treated with anchor sutures. She was followed up at 6 months with no signs of avascular necrosis.¹³ To conclude, there are few type IV fractures in paediatric patients reported in the literature. They have been treated with different although similar means of fixation.

Learning points.

• True capitellum type IV fractures are rare in the paediatric population, but the injury should not be overlooked.

• They can be diagnosed by the double arc sign on X-ray.

• CT scan is useful for preoperative planning.

• Treatment should include anatomic reduction and stable fixation.

• Headless compression screws with anterior to posterior placement are a good treatment option.