Treating Triplane Ankle Fractures in Children
Triplane fractures of the ankle affect three sections of the lower part of the tibia (lower leg bone). That's why they are called "triplane." The force of injury is strong enough to split the joint surface, fracture the epiphysis (round end of the tibia), move through the growth plate, and go out the metaphysis (area between the main part of the bone and the epiphysis at the end of the bone). The growth plate is contained within the metaphysis.
The location and severity of triplane fractures cannot be fully assessed from plain X-rays. CT scans must be taken in order to show the fracture line through multiple planes and angles of the tibia. Different fracture lines will be seen when viewed from the front/back (coronal view), side (sagittal view), and above (axial or transverse view). This is what is meant by a fracture that is triplanar.
A major complication in treating triplanar ankle fractures is the gap or step-off that occurs when the bones shift. When this happens, the bones no longer line up, which means the two sides of the ankle joint are no longer evenly matched. Such a situation has to be treated or the uneven weight-bearing surface will be painful. Down the road, arthritis will develop causing further problems.
The question addressed in this article relates to that gap. How much of a gap is acceptable? When does the gap have to be reduced (brought back together)? And what's the best way to accomplish this type of treatment? Dr. Alvin H. Crawford from the Cincinnati Children's Hospital Department of Orthopedic Surgery offers his recommended approach.
Using X-rays, CT scans, and arthrograms, he demonstrates treatment of several individual cases with a closed reduction under real-time image intensifier (arthrogram or fluoroscopy). Pins and screws are placed through the skin (called percutaneous) to hold the bones together during healing. He suggests on the basis of current evidence that a gap of more than 2 millimeters must be treated and reduced. This is advised in order to avoid complications and the potential for arthritis.
A second type of ankle fracture that affects the growth plate is also discussed. This is the Tillaux fracture. The front (anterior) and outside (lateral) portion of the lower tibia is broken off (called avulsion) while still attached to the anterior inferior tibial-fibula ligament.
Both the triplanar and Tillaux fractures occur most often during the teen years, the growth plate can be affected in a unique way. It's during this time period that the growth plate starts to fuse with the bone. But it does so in a rather uneven, asymmetric fashion. First the middle portion hardens and stops growing, and then the medial or inside edge completes its growth phase. The lateral (outside) edge is the last to solidify. The area that is still open is usually where the fractures occur.
These fractures can be treated with closed reduction if the patient makes it to the surgeon within the first 72 hours. Open surgery is only required when efforts to traction and place the bones in correct position fail. Any of these fractures that are not stable will need some type of fixation (metal plate, screws, pins, wires). Hardware is removed within a year's time to avoid screws breaking or stripping.
Studies show that arthritic changes can be seen on X-rays in Tillaux or triplane ankle fractures within six years. Anytime a gap is left untreated after these fractures, there are going to be problems. That's why the author wrote this article and strongly encourages surgeons to surgically restore the joint as close to its anatomic position as possible. He concludes by saying that a gap of less than two millimeters is acceptable; a gap greater than two millimeters is not.
Alvin H. Crawford, MD. Tripland and Tillaux Fractures: Is a 2 mm Residual Gap Acceptable? In Journal of Pediatric Orthopaedics. June 2012. Vol. 32. No. 1. Supplement. Pp. S69-S73.