Snowboarder's Ankle
What exactly is the snowboarder's ankle?
The Snowboarder's Ankle is a fracture of the so-called Processus lateralis tali (the outer process of the talus) and was already described in the medical literature in 1965. Even though the history of snowboarding goes far back to Hawaii with the He'ehölua, to the Salzburger Land with the Knappenrößl or to Turkey with the Lazboard, the likelihood of the fracture occurring due to the use of the snowboard's ancestors during that time is very low, because the injury typically occurs during landing after a jump.
The initial description of this rare fracture (1.2% - 6.3% of lower extremity fractures)
became associated with snowboarding only in the late 1980s after systematic analyses of snowboarding and skiing injuries. Between 1994 and 1996, the terms "snowboarder's fracture" and "snowboarder's ankle" emerged.
According to a 1995 study, over 1/3 of ankle fractures in snowboarders were fractures of the lateralis tali process.
Note: the English term "ankle", in contrast to the German term "Knöchel", also includes the ankle bone.
Emergence and causes
The accident mechanism in snowboarder's ankle is considered specific to snowboarding, because only in this sport (and wakeboarding) the ankle joints are fixed by the snowboard boots as well as the snowboard bindings in a position of the feet during landing, which is between 70° and 90° to the direction of locomotion. During the landing after a jump, there is a large force impact (axial loading) and in case of an unclean landing, there is an increase in weight distribution on the front or back leg.
This leads to a so-called dorsal extension (stretching of the foot and toes towards the back of the foot) as well as to a so-called eversion (movement of the foot away from the neutral position towards the outside). The tight construction of the snowboard boots (even soft boots are usually tight enough) combined with the snowboard binding secure the ankle joint so that a classic twisting trauma (as in skateboarding, for example) does not occur and the axial (from top to bottom) force cannot "break out" to the inside.
The force is further transmitted along the outer ankle on the foot fixed in the snowboard boot to the ankle bone (talus) located below the fibula and in particular to the outer process of the ankle bone (processus lateralis tali). If sufficient force is applied, the bone breaks at this location. This trauma mechanism was confirmed in cadaver studies in 2003.
The fractures of the lateralis tali process can be pronounced in different ways. For this reason, a classification of the fractures was already attempted in 1965. The most common classification of the lateral process fracture today is the one according to McCrory and Bladin from 1996, which is also used in the diagnosis of snowboarder's ankle (also snowboarder's fracture).
The three types of fractures McCrory and Bladin classification (1996)
The classification of fractures of the Processus lateralis tali
has evolved over the years.
The initial classification by Hawkins was later reclassified by McCrory
and Bladin according to the severity of the injury:
Type I
small break-off at the tip of the process (avulsion)
Type II
large single bone fragment
Type III
similar extent of injury as type II, but as
comminuted fracture (many small fragments)
What is a talus?
The talus is a bone of the lower extremity that transfers the load of the body from the lower leg to the subtalar foot skeleton. The talus has several connections through joints with the neighboring structures - with the tibia and fibula in the upper ankle joint, with the calcaneus, navicular bone and with the spring ligament in the lower ankle joint. The talus is divided into a body, neck and head.
Ossification begins in the talus in the 28th - 32nd week of development with one or two bone cores. The so-called tuberculum laterale of the posterior process may develop as an apophyseal appendage. In about 6% of people, the bony fusion is incomplete, which results in an independent dorsal ossicle - the so called Os trigonum.
Complaints and symptoms
The typical symptoms of Snowboarder's Ankle are pain and swelling in the tarsal and outside of the foot. These symptoms can easily be confused with those of a sprain or torn ligament. This is true for both the affected person and the examining physicians - especially if the cause of the accident is unknown.
The diagnosis can be further complicated by the fact that this fracture is sometimes difficult to recognize on conventional X-rays. This is the case with small fractures (type I) that are not displaced. The probability of overlooking a fracture of the processus lateralis tali on radiographs is given in the literature as up to 50%.
For this reason, cross-sectional imaging is recommended when a snowboarder's ankle is clinically suspected.
MRI of the ankle joint can show the so-called bone marrow edema in the context of a fracture or a bone contusion very well. However, a fracture line cannot always be well delineated, so distinguishing between fracture or s.t. subtalar impingement can be difficult. Computed tomography can best show fracture lines without superimposition and should be considered the examination method of choice.
MRI can be helpful in identifying accompanying soft tissue injuries - e.g., cartilage damage, ligament and tendon tears.
What should I pay attention to as a snowboarder?
Snowboarder's Ankle is an injury of advanced snowboarders and typically occurs after a landing. If you have pain on the back and outside of your foot after a snowboarding session (especially kicking in the park) , take it seriously. Even if you are used to such pain from skateboarding, don't dismiss it as an ankle sprain. Have yourself examined and tell the radiologists that you are a snowboarder and have heard of Snowboarder's Ankle.
If you are unsure, you can always contact us!
Treatment of the Snowboarder's Ankle
Early recognition of the injury is particularly important for avoiding complications such as pseudarthrosis, impingement, bone necrosis, or post-traumatic osteoarthritis. The size of the fracture and the number of displaced fragments are important for treatment planning.
As a rule, the small so-called avulsion injuries are treated conservatively with symptomatic therapy, short-term immobilization, followed by mobilization of the joint and increasing weight-bearing.
If symptoms persist after 6 months, surgical remodeling of the process may be indicated.
Non-displaced fractures can be treated with immobilization without weight bearing for 4-6 weeks, followed by mobilization in a walking splint for another 2-3 weeks.
Fractures with displaced fragments are more problematic as they can lead to pseudarthrosis if not treated surgically. Closed reduction of the fragments is considered insufficient.
Individual fracture fragments that are larger than 1 cm or displaced more than 2 mm should be surgically reduced. This can be done with the aid of a screw or a so-called Kirschner wire. Headless screws such as the Herbert screw can be used for this purpose, as they can be countersunk below the articular surface.
Removal of larger or multiple fracture fragments may result in significant instability of the lower ankle joint and require fusion (arthrodesis) of the joint. If post-traumatic osteoarthritis develops as a result of the injury, fusion of the joint may be necessary because the lower ankle is more often affected than the upper ankle. It is very rare for osteoarthritis between the fibula and the talus to require joint fusion.
The snowboard shots were provided to us by
Sources:
- G. Hawkins: Fracture of the lateral process of the talus . In: The Journal of bone and joint surgery. American volume. Vol. 47, September 1965, pp. 1170-1175.
- C. Pino, M. R. Colville: Snowboard injuries . In: The American journal of sports medicine. Volume 17, Number 6, 1989 Nov-Dec, pp. 778-781.
- Nicholas, J. Hadley, C. Paul, P. James: "Snowboarder's fracture": fracture of the lateral process of the talus . In: The Journal of the American Board of Family Practice / American Board of Family Practice. Volume 7, Number 2, 1994 Mar-Apr, pp. 130-133.
- McCrory, C. Bladin: Fractures of the lateral process of the talus: a clinical review. "Snowboarder's ankle." In: Clinical Journal of Sport Medicine . Volume 6, Number 2, April 1996, pp. 124-128.
- Miller: Fractures of the Lateral Process of the Talus: Snowboarder's Fracture. In: PI Update 2008: Chapter 23, pp. 119-123.
- Bohyn, D. V. Flores, T. Murray, B. Mohr, M. Cresswell: Imaging Review Of Snowboard Injuries. In: Semin Musculoskelet Radiol 2022: 26: 54-68.
- In: Waldeyer Anatomy of Man, 17th edition, 2003, pp. 1106-1108.
