Fractures around the distal humerus are common in pediatric age ^[1]. They are most commonly supracondylar fractures, followed by lateral condyle fractures and medial epicondyle fractures. Transphyseal separations of the humerus are rare and occur in children younger than 3 years, such as birth injuries in neonates or non-accidental injuries ^[2]. Lateral condyle fractures are classified based on their displacement. Weiss type 1, type 2, and type 3 are lateral condyle fractures with displacements of <2 mm, 2–4 mm, and more than 4 mm, respectively. Types 1 and 2 are treated by cast application or closed reduction with pinning. Type 3 fractures have articular incongruence and may need open reduction ^[3]. Transphyseal separations need closed reduction and pinning. It is challenging to differentiate transphyseal humerus from type 3 Weiss lateral condyle humerus fractures on plain radiographs ^[2]. Magnetic resonance imaging (MRI) is costly and needs sedation. Only limited literature is available to help the Orthopedician distinguish these fractures with overlapping clinical and radiological features, but different managements. In this case report, we describe the clinical and radiological features and provide a flowchart to help with decision-making.

A 4-year-old child was brought to the emergency department following an elbow injury due to a fall on the outstretched hand. Clinical examination showed swelling and deformity. There was no distal neurovascular deficit.

Diagnostic assessment

We preoperatively performed standard anteroposterior (AP) and lateral views of the elbow (Fig. 1). We performed a radiograph of the uninjured elbow for comparison. The differential diagnoses were transphyseal separation, lateral condyle humerus fracture, and elbow dislocation.

Therapeutic intervention

Under general anesthesia and in a supine position, closed reduction was done with longitudinal traction, mediolateral correction, and elbow flexion to stabilize the fracture. We did percutaneous pinning with two lateral 1.5 mm K-wires. We did arthrography by injecting Iohexol from the lateral aspect of the elbow. The arthrogram showed articular congruity (Fig. 2). Pins were bent, cut, left outside for easy removal, and immobilized at seventy degrees with a back slab. We did a post-operative CT to assess the fracture pattern and reduction. (Fig. 3).

Follow-up and outcome

The post-operative period was uneventful. We removed K wires at four weeks and started elbow mobilization. At the end of 3 months, a full range of movements was present, and the fracture showed good callus bridging over the medial and lateral metaphysis on the radiograph (Fig. 4).

Clinical presentation

Transphyseal separations are rare and often occur under 3 years of age ^[2]. They occur in newborns due to traumatic deliveries and child abuse. More common elbow injuries in children include supracondylar humerus fractures, lateral condyle fractures, and medial epicondyle fractures. Neurovascular injuries are uncommon after transphyseal separation and lateral condyle fractures when compared to supracondylar humerus fractures.

Investigations

Radiographs include standard AP and lateral views. Transphyseal fractures are classified by DeLee into three groups based on ossification of the capitellum. Group A fractures (Salter-Harris Type-I) occur before the lateral condylar ossification center appears, usually in infants. Group B in ages 12 months to 3 years has a definite ossification center. They can be Salter–Harris II fractures with a small flake of metaphyseal bone. Group C includes large metaphyseal fragments (Salter–Harris II fractures), mostly seen in children aged 3–7 years. The classification was later modified by Zhou in 2019 to emphasize more on the size of the metaphyseal fragment rather than the age of the child ^[4]. In Weiss type 1 lateral condyle or medial epicondyle fractures, it is important to take internal and external oblique views ^[5,6]. We can detect Weiss type 2 and 3 injuries in standard AP and lateral views due to the higher displacement. The table shows the relation of various landmarks in different conditions (Table 1). Elbow dislocation also appears similar on radiographs but is uncommon in children. Intercondylar fractures can occur in older children and adolescents. They are often undisplaced, requiring only closed reduction and pinning, unlike in adults, where they are often displaced and rotated, requiring open reduction ^[1].

In inconclusive cases or suspected capitellum or intercondylar fractures, we can perform a CT or MRI or ultrasonography preoperatively or arthrogram intraoperatively. In transphyseal separations, CT can help identify the Thurston–Holland fragment. In our case, the CT showed a large medial Thurston-Holland fragment, a feature suggestive of entire distal humeral physeal injury, differentiating it from lateral condyle fracture. MRI is useful in differentiating these injuries accurately, but it needs sedation. Ultrasound is helpful in transphyseal separation of infants where the ossification of the lateral epiphysis has not started ^[1]. Treatment: Arthrography helps differentiate transphyseal separation and Type 3 Weiss lateral condyle fracture. It is a common conception to general orthopedic surgeons that lateral condyle requires open reduction. However, some lateral condyle humerus may be amenable for closed reduction. Hence, arthrogram is necessary during the surgery ^[6,7]. The continuous articular margin on the arthrogram suggests transphyseal separations, type 1, 2, or well-reduced type 3 Weiss lateral condyle fractures ^[8]. Type 3 Weiss fractures with displacement of more than 2 mm, even after closed reduction, need open reduction and pinning or cannulated cancellous screws ^[9]. A transverse column pin adds stability to the two lateral pins for lateral condyle fractures. Transphyseal separations can be treated similarly to supracondylar fractures with two to three lateral or cross wires ^[2]. Postoperatively, periosteal new bone formation is also an indicator of the type of fracture. The lateral condyle has a callus predominantly on the lateral column, and transphyseal separations have a callus on both medial and lateral columns. The flowchart (Fig. 5) can help in management.

Outcomes

If not reduced adequately, significant cubitus varus deformity can occur at later ages, needing corrective osteotomies. In contrast, lateral condyle fractures can have a wide range of complications, including osteonecrosis, nonunion, tardy ulnar nerve palsy, and cubitus valgus, which make long-term follow-up necessary ^[7,9,10].

Limitations of the case report include the need for proper pre-operative radiographs without backslab, including true AP, lateral, internal, and external oblique views. Furthermore, a pre-operative MRI is helpful in a more accurate diagnosis.

A careful assessment of alignments on radiographs and intraoperative arthrogram findings can help distinguish type 3 Weiss lateral condyle fracture from transphyseal separations. It can avoid unnecessary open reduction and its related complications.

Though distal humerus fractures are common injuries in children, it is important to know some rare injuries like transphyseal separation of the humerus. Following the flowchart provided in the report can help in streamlined management.