Open Reduction and Internal Screw Fixation of Transitional Ankle Fractures in Adolescents.

UNLABELLED

A triplane fracture is an example of a transitional fracture of adolescence that occurs because the distal tibial physis closes in a predictably asymmetric way from central to medial and then lateral. The triplane fracture is so named because the fracture lines propagate in 3 planes (axial, sagittal, and coronal) and thus appear on radiographs as a Salter-Harris III pattern on anteroposterior images and Salter-Harris II or IV on lateral images. The fracture occurs via a twisting mechanism (usually supination and external rotation) through the relatively weak open portion of the physis (axial) and propagates out the metaphysis (coronal) and/or epiphysis (sagittal) at the transition to the relatively stronger closed portion of the physis. Because the distal tibial physis closes over approximately an 18-month period in female patients from 12 to 14 years old and male patients from 13 to 15 years old, this is the age range in which triplane fractures occur. Triplane fractures account for approximately 5% to 10% of pediatric ankle fractures. The purpose of the present video article is to review the indications for operative treatment of transitional ankle fractures in adolescents and to detail the surgical technique specifically for open reduction and screw fixation of triplane fractures. The procedure is performed in order to provide anatomic reduction of the fracture and rigid fixation.

DESCRIPTION

Surgical treatment of a triplane fracture is indicated if there is >2 mm articular displacement of the distal aspect of the tibia or if the fracture pattern is deemed unstable following closed reduction and casting. Preoperative planning (Step 1) involves the use of radiographs and computed tomography scans to determine accurate fracture classification, the intended reduction maneuver, possible blocks to reduction, and screw trajectory and length. Room setup and patient positioning (Step 2) include placing the patient in the supine position with a bump under the hip, as well as the placement of a ramp or stack of blankets under the affected limb and adequate general anesthesia with muscle relaxation to facilitate reduction. Incision and surgical exposure (Step 3) is performed with use of an anterior ankle incision at the anatomic plane between the extensor hallucis longus and extensor digitorum longus, protecting the neurovascular bundle (i.e., the anterior tibial artery and deep peroneal nerve). Open reduction and assessment of reduction (Step 4) begins by removing any soft tissue, such as the periosteum, that may be interposed in the fracture site precluding a reduction. The ankle is then put through internal rotation and dorsiflexion in order to reduce the fracture, utilizing direct visualization through the incision and fluoroscopy to verify reduction with <2 mm articular step-off. Screw placement (Step 5) typically involves a 2-screw construct, with 1 screw starting at the anterolateral distal tibial epiphysis aiming medially (and staying within the epiphysis) and a metaphyseal screw aiming from the anterior metaphysis to the posterior Thurston-Holland fragment. Closure and immobilization (Step 6) usually involve a layered skin closure, as no deep closure is necessary in most cases. A below-the-knee cast is applied with the ankle in neutral dorsiflexion.

ALTERNATIVES

Nonoperative treatment typically involves closed reduction and long-leg cast immobilization.

RATIONALE

Surgical treatment with reduction and screw fixation of triplane fractures is indicated for patients with >2 mm articular displacement or >3 mm physeal displacement of the distal aspect of the tibia. Achieving and maintaining reduction with screw fixation within these tolerances helps decrease the chance of arthritis development by 5 to 13 years postoperatively.

EXPECTED OUTCOMES

Following treatment of a triplane fracture with reduction and screw fixation, full ankle range of motion and normal growth are anticipated. Postoperative follow-up continues until skeletal maturity or until 1 year postoperatively with evidence of continued growth by Park-Harris lines on sequential radiographs. Short-term recovery is expected to be excellent, and long-term results are expected to be good as long as <2 mm articular reduction is achieved and maintained.

IMPORTANT TIPS

General anesthesia with muscle relaxation helps with closed or open reduction.Computed tomography is valuable for determining the maximum articular displacement and for 3D surgical planning for screw trajectories.Be aware of the periosteum and perichondrial ring as possible soft-tissue blocks to reduction, and do not hesitate to visualize the periosteum with an open technique to achieve anatomic reduction.

ACRONYMS AND ABBREVIATIONS

AITFL = anterior inferior tibiofibular ligamentAP = anteroposteriorCT = computed tomography.