Patrón de fractura de tobillo tillaux juvenil en un adulto esqueléticamente…

«Patrón de fractura de tobillo tillaux juvenil en un adulto esqueléticamente maduro.»

Closure of the growth plate begins in adolescence, leading to unique fracture patterns in this age group. By approximately age 13, the distal tibial epiphysis closes centrally and then medially, with the anterolateral side of the distal tibial physis closing last [1] and [2]. This pattern of physeal closure makes the anterolateral portion of the distal tibia epiphysis susceptible to an avulsion injury by the distal anterior tibiofibula ligament. The juvenile Tillaux fracture is defined as a Salter Harris III fracture of the distal tibial anterolateral epiphysis. These fractures typically occur in children between the ages of 12–14 and account for 3–5% of pediatric ankle fractures. The mechanism of this fracture is typically supination with external rotation [1] and [2]. With external rotation, the anterior inferior tibiofibular ligament becomes taught and after additional force, the anterior tibial lateral epiphysis fractures, with the size of the fragment depending on the extent of the fusion medially [3]. In adults, the supination external rotation mechanism often causes a direct bony avulsion of the anterior inferior tibiofibula ligament. We have found reports that associate Tillaux fractures with syndesmotic injuries [3] and [4]. We present the case of a 19-year-old skeletally mature male who sustained a displaced intraarticular distal tibia fracture in which the fracture plane exited anterolaterally through the physeal scar.

1. Case report A 19-year-old male with no significant past medical history presented after twisting his right ankle while falling down several steps at a party. The patient was unable to bear weight on his right lower extremity and developed immediate swelling around the ankle. On physical examination, he had limited range of motion of the ankle with distal anterior tibia tenderness but no medial or lateral malleolus tenderness. The neurovascular examination was normal. Radiographs showed a displaced intraarticular distal tibia fracture in which the fracture exited anterolaterally along the plane of the physeal scar. In the anteroposterior radiographic image, the epiphyseal fragment consisted of approximately 50% of the articular surface. There were no medial or lateral malleolus fractures. The medial joint space did not appear widened and there was no radiographic evidence of distal tibiofibular syndesmosis diastasis. This fracture was classified as a B1 according the AO classification for distal tibia fractures [5]. However, the patient suffered a low energy injury and the fracture pattern was more consistent with a rotational ankle injury rather than a Pilon fracture. Contralateral ankle radiographs were obtained and showed the physis to be completely closed. The fracture was reduced with internal rotation and dorsiflexion of the ankle, which was then placed into a long leg cast. The extent of the articular step-off and diastasis was difficult to assess using radiographs alone. After the reduction, a computerized tomography (CT) scan with 1 mm cuts was obtained, which demonstrated a 2 mm articular step-off in the coronal plane with 3 mm of diastasis in both the axial, coronal, and sagittal planes.

Most authors believe that operative fixation is warranted if an intraarticular step-off or diastasis ≥2 mm persists after closed reduction [1] and [2]. Based on the displacement seen on the CT scan, operative management was chosen. The ankle was exposed via an anterior approach and the fracture was reduced with a 0.62 K-wire. It was subsequently stabilized with one 3.5 partially threaded cannulated screw and washer. After fixation, the articular surface of the distal tibia was directly visualized. No articular step-off could be appreciated and the diastasis was completely closed. After closure, a short leg cast was placed in the neutral position, and the patient was instructed to remain non-weight bearing for 6 weeks. After 6 weeks, the short leg cast was removed, the patient began active range of motion, and weight bearing was advanced. At 12 weeks, the patient had complete range of motion without pain. He did not complain of any ankle pain with weight bearing. By 12 weeks postoperatively, the radiographs demonstrated complete healing of the fracture with no appreciable articular step-off.

2. Discussion Juvenile Tillaux fractures occur in the adolescent once the distal tibial growth plate has closed centrally and medially, with the lateral portion remaining open. In skeletally mature adults, an avulsion of the anterior inferior tibiofibula ligament occurs but is not typically associated with an intraarticular distal tibia fracture. Thus, the juvenile Tillaux fracture pattern is unique in the adult population and has not been described in the literature. In this case, the fracture propagation along the physeal plate may have occurred because the lateral physis was weakened due to incomplete ossification [6]. There are several basic science studies in the literature, which may help to explain some potential causes of delayed ossification of long bones. Childhood hypothyroidism has been shown to cause growth arrest and delayed growth plate ossification. Thyroid hormone (T3) regulates chondrocyte proliferation and hyperthrophic differentiation which is necessary for enchondral ossification [7]. Also elevated levels of parathyroid hormone-related peptide (PTH-rp) and Indian Hedgehog expression have been found in the articular cartilage of horses with osteochondrosis. Histologic specimens from equine cartilage with ostoechondrosis will consistently show delayed ossification. Semevelos SA has suggested a possible link between elevated levels of PTH-rp expression and delayed ossification of growth plates in horse models [8]. Finally, mouse studies been shown that deletion of the c-Cbl gene causes decreased osteoclast recruitment and subsequent vascular invasion of growth plate cartilage [9]. These steps are critical in order for enchondral ossification to occur. We have not seen these finding applied to any human studies in the literature. This patient had no history of endocrine or calcium metabolism disorders that could lead to delayed physeal closure. Furthermore, contralateral ankle radiographs demonstrated that the physis was completely closed with no abnormalities. This patient possibly has had a delayed ossification of both of his distal tibia growth plates, but the contralateral side may have recently closed while the affected side remained open. Unfortunately, we do not know at what age this patients contralateral distal tibia growth plate completely closed.

As mentioned before, one would expect the avulsion of the anterior inferior tibiofibula ligament to be accompanied with a small bony fragment (Chaput fragment). This particular fracture was treated in a similar fashion to the classic juvenile Tillaux fracture in that partially threaded screws were used to obtain compression across the fracture site. By 3 months postoperatively, this patient had no ankle pain and had regained his pre-injury range of motion. Several studies have shown that if anatomic reduction of the articular surface is achieved, long-term prognosis is good and the vast majority of patients have minimal pain and a return to previous level of function [10] and [11]. This case illustrates the necessity in obtaining a CT scan with 1 mm axial sections in order to accurately assess the diastasis and the articular step-off of the Tillaux fragment which can determine if the fracture will be treated operatively or with a long leg cast. Although up to 29% of patients who sustain Salter Harris III or IV ankle fractures will develop radiographic evidence of osteoarthritis, many of these patients will be asymptomatic [2]. Thus, based on available data, patients with these ankle fractures appear to have a good clinical prognosis. We learn from this case that pediatric fracture patterns may occur in older patients if there is delayed ossification of the affected growth plate.

The Foot. Volume 16, Issue 1 , March 2006, Pages 54-59.

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