Proximal tibia triplane fracture with apophyseal avulsion

Background

Tibial tuberosity fractures occur in fewer than 1% of all paediatric fractures, typically occurring in boys of adolescent age and are typically caused during athletic activities.1 Although relatively rare, they are well documented. Common sports include basketball, football and athletics.2 3 The mechanism of injury is through either concentric contraction of the quadriceps during jumping, or with an eccentric contraction while the knee is in forced flexion.4 These forces result in a pull of the patella tendon from its insertion at the tibial tuberosity.

In the proximal tibia, there are two ossification centres. The first is in the proximal tibia physeal plate itself, whereas the second is in the apophysis. During the early adolescent years, the physeal plate closes postero-anteriorly and proximo-distally with the second ossification centre closing later than the first.3

In the 1950s, Reginald Watson-Jones classified tibial tuberosity fractures into types I, II and III, respectively, representing avulsion of the tibial tubercle alone, extension across the physis without entering the knee joint and finally proximal extension into the knee.5 This classification was subsequently modified by Ogden et al to more accurately define specific fracture patterns and to guide treatment for different fracture types by considering displacement and comminution.6

We discuss an alternative presentation of a paediatric avulsion fracture, where the tibial tuberosity fracture extends into a triplanar fracture of the proximal tibia without intra-articular involvement.

Triplane fractures of the distal tibia have been well researched and considered in paediatric injuries over the last 50 years having been first described by Lynn et al.7 As the name suggests, triplane fractures occur in three planes (transverse, sagittal and coronal) and involve the metaphysis, physis and epiphysis of the bone. The distinctive fracture configuration is typically influenced by both the deforming forces applied during injury, but also as a result of the pattern of growth plate closure seen in the adolescent population. This has been described as beginning with central physeal closure followed by anteromedial, then posteromedial and finally lateral closure of the growth plate.8

Although triplane fractures of other joints have been reported in the literature,9 10 they are infrequent and rare. Physeal fractures of the proximal tibia in particular account for just 1%–3% of all physeal injuries.6 11 12

We present this unusual case of a tibial apophyseal fracture concurrent with a proximal triplane fracture following a secondary injury due to lack of appropriate management and compliance. This might be an underreported variant of the proximal tibial injuries in the adolescent sportive population that will shed light to future possible mechanism and guide management.

Case presentation

A healthy, fit and well, early adolescent football player presented to his local emergency department after hearing a click in his left knee while kicking the ball with his right foot. This was immediately followed by pain and inability to fully weight bear on the left leg. Plain radiographs showed an abnormal elevation of the tibial tubercle suggestive of a mildly displaced avulsion fracture (figure 1). He was treated conservatively in the first instance and advised to rest the leg for 2 weeks.

The patient re-presented to the emergency department 2 weeks later. Due to an improvement of symptoms, the patient had restarted football prematurely and sustained a tackle where again he noted a loud click, followed by a sharp pain in his left knee. This time, the injury was associated with immediate swelling over the knee and complete inability to weight bear. Subsequent plain radiographs showed further widening of the anterior growth plate of the upper tibial apophysis, consistent with a worsening avulsion growth plate injury (figure 2).

Investigations

A limited CT scan was performed confirming the widening of the apophyseal growth plate as well as a Salter-Harris type IV fracture of the posterior aspect of the tibia (figure 3A,B).

The patient’s management was subsequently escalated to our institution, a tertiary orthopaedic centre with a paediatric unit. Following multi-disciplinary team (MDT) discussion, an MRI of the knee was requested to assess any concurrent soft tissue injury given the history and mechanism of injury. It would also help to identify any early soft callus, visualise any periosteal interposition within the fracture site preventing reduction, as well as identifying associated intra-articular lesions, including cruciate ligamentous injury. Indeed, the MRI demonstrated periosteal entrapment at the tibial tuberosity alongside grade 1 sprains of the anterior cruciate ligament (ACL), superficial medial collateral ligament (MCL) and the myotendinous junction of popliteus.

Treatment

Initially, closed reduction with manipulation under anaesthesia was attempted without success. Therefore, a conversion to open reduction and internal fixation of the fracture was performed. A longitudinal incision was made over the tibial tuberosity with careful dissection down to the fracture site. A large periosteal sleeve was identified caught within the fracture site (figure 4), as demonstrated on the MRI. This was removed and any torn parts excised. The fracture was subsequently reduced and, with the knee in hyperextension and the reduction held by hand, fixed with two, 4 mm partially threaded, cancellous cannulated screws with washers.

Outcome and follow-up

Postoperatively, the patient was placed in an above leg cast with 15° of flexion, non-weight bearing (NWB), with gradual extension of a hinged knee brace on to 45° and 90° over the course of 6 weeks (figure 5A,B). At 6-week follow-up, scars were completely healed and the patient had an intact straight leg raise, but with minor lag due to pain along the patellar tendon. Weight bearing was commenced at this point. By 3 months, the patient had no leg length discrepancy or angular deformity seen and he returned to sport, participating in full sport by 4 months. Despite the concerns for growth plate deformity and potential for recurvatum, no obvious growth deformity was noted.