General Patterns, With a Focus on Talus Fractures
Andrea J. Boon, MD; Jay Smith, MD; Edward R. Laskowski, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 27 - NO. 4 - APRIL 1999
In Brief: Injury patterns in snowboarding differ from those in Alpine skiing. Snowboarders tend to have fewer knee and thumb injuries than skiers but more upper-extremity trauma, fractures in general, and ankle injuries. Of particular concern in snowboarding is fracture of the lateral process of the talus (LPT), which masquerades as an inversion ankle sprain, is often missed, and can lead to significant disability. Signs are typically similar to those of inversion sprains, but pain on palpation of the lateral process can be helpful in diagnosis. Standard radiographs often do not show the fracture, so CT or lateral tomography may be required. The most minor, nondisplaced LPT injuries may heal with casting and rehab, but more severe fractures typically require surgery.
In recent years snowboarding has developed into a mainstream winter sport, with an exponential increase in popularity (see "Snowboarding History and How-to," below). This increased participation, of course, means that more and more primary care physicians are seeing patients who snowboard at various skill levels. To aid in early injury recognition and optimal management of such patients, clinicians should be familiar with the injury patterns associated with this sport.
Compared with Alpine skiing, snowboarding entails a significantly higher risk of upper-extremity and ankle injuries, particularly fractures (1-5). Fracture of the lateral process of the talus is unusually common among snowboarders, and knowledge of this injury is important because the condition masquerades as an anterolateral ankle sprain and frequently is undetected on plain radiographs. Misdiagnosis of this fracture may lead to severe degeneration of the subtalar joint and long-term morbidity (6-8).
Overview of Snowboarding Injuries
Overall snowboarding injury rates are remarkably similar to those of Alpine skiing, at about 5 injuries per 1,000 visits to the slopes (2,9-11). Significant differences in injury patterns, however, have been identified between the two sports, as well as differences in injury rate and patterns among subpopulations within each sport. For example, one study (9) found that only 4% of snowboard-related injuries required hospital admission for more than 5 days, as compared with 19% of skiing injuries.
The most common snowboarding injuries are simple sprains, followed by fractures and contusions (2,9). The more serious snowboarding injuries usually result from collisions and often involve contusions to the vital organs, particularly the spleen and less often the liver (3,10,12). Mild head injuries and coccygeal injuries can occur in backward falls and are well documented (1,3,5). There appears to be less risk of serious chest or spinal injury in comparison to skiers (12). Aerial maneuvers are associated with more abdominal, chest, spine, and head injuries than nonaerial maneuvers are (3).
Relative to skiers, snowboarders have 2.4 times as many fractures (particularly of the upper limbs), fewer knee injuries, and more ankle injuries (1,3,4,9,10,13). Knee injuries tend to be less severe in snowboarders than in Alpine skiers (9,10). It appears, though, that as the level of snowboarding expertise increases, so does the risk of more serious knee ligament injuries such as anterior cruciate ligament rupture (Peter C. Janes, MD, personal communication, February 1999). This observation, should it prove accurate, may relate to the increased frequency of aerial maneuvers and the use of hard-shell boots (4,5,9,14). Disruption of the ulnar collateral ligament of the thumb, which is relatively common in skiers, is virtually unheard of in snowboarders, presumably because they don't use poles (1,5,13).
Only limited data are available on snowboarding fatalities, but rates appear comparable to those of skiers (10). As with skiing, the major risk is from blunt trauma to the head or chest (10). A potential cause of death among snowboarders, though, is immersion, in which a snowboarder is buried head first in the snow, usually in a tree well, can't free himself or herself, and suffocates. This danger underscores the importance of snowboarding with a partner. The risk of avalanche applies equally to both sports.
Most studies have found that beginning snowboarders are relatively more likely than beginning skiers to be injured. Several studies (1,4,9) report that in Alpine skiing, only a third of those injured are beginners, whereas about 60% of snowboarding injuries occur in novices. A recent study (15), however, found that although injury rates for first-time snowboarders and skiers were similar, snowboarders sustained a higher percentage (53%) of upper-extremity injuries, while skiers had a higher percentage (63%) of lower-extremity injuries. This study also found that first-time snowboarders sustained more injuries that required emergency care (eg, concussion, fracture, dislocation, and dental injury).
In comparison to experts, beginning snowboarders have a higher rate of upper-extremity fractures, especially of the wrist (3,9), more lacerations and contusions resulting from collisions (4), and more head and spine injuries (4). The higher rate of head and spine injuries is thought to reflect an increased risk of totally losing control of the board. Snowboard equipment type (see "Boards and Bindings," below) may affect injury patterns, but current data are inconclusive (1,2,4,5,9,16).
Snowboarder's Ankle: Fracture of the Lateral Process of the Talus
The injury that is most particular to snowboarding and until recently was largely unrecognized is fracture of the lateral process of the talus (LPT). Recent epidemiologic studies of snowboarding injuries have highlighted LPT fractures (9,16). This is an unusual fracture, rarely seen in other clinical settings, with fewer than 65 cases reported in the English literature prior to the recognition of the fracture among snowboarders (17). Mukherjee et al (7) had estimated in 1974 that LPT fractures accounted for less than 1% of all ankle injuries.
Kirkpatrick et al (16), however, recently published a prospective study documenting more than 3,000 snowboarding injuries, specifically looking at the pattern of foot and ankle injuries. Fifteen percent of all injuries affected the ankle, and 44% of these were fractures. Fractures of the lateral process of the talus accounted for 32% of ankle fractures and 15% of all ankle injuries.
Anatomy and mechanics. The talus is important in rotatory and hinge movements at the talocrural and subtalar joints. Fractures of the talus carry a risk of avascular necrosis and nonunion. The lateral process is a portion of the posterior talar facet (figure 1). It is a large, wedge-shaped prominence spanning almost the entire lateral wall of the talus. The lateral process has two articular surfaces, one positioned inferomedial to the fibula and the other dorsolateral to the anterior portion of the posterior calcaneal facet. LPT fractures commonly involve the articular surface of the talus. In severe injuries, there may also be a chondral defect of the posterior calcaneal articular surface.
The mechanism of LPT fracture is controversial. Many authors believe sudden severe dorsiflexion with the hindfoot in inversion causes the fracture (7,18). This motion produces a shearing force transmitted from the calcaneus to the LPT, resulting in fracture fragments of variable size (2,11,19). This could occur when landing after an aerial maneuver, which is reportedly a common cause of injury in snowboarders (20) (Peter C. Janes, MD, personal communication, February 1999). This proposed injury mechanism, however, is not universally accepted.
Clinical features. Clinically, LPT fractures closely resemble inversion ankle sprains. Snowboarders report a dorsiflexion twisting injury, such as landing an aerial that included a twist. Often, but not always, they are unable to continue boarding. Symptoms include anterolateral ankle pain and swelling with painful weight bearing. Depending on the severity and the time interval since the injury, ecchymosis may be present.
Physical examination reveals swelling over and anterior to the lateral malleolus and pain with ankle dorsiflexion and plantar flexion and/or with subtalar inversion and eversion. The lateral process is tender on palpation just inferior to the tip of the lateral malleolus. Unfortunately, this potentially specific finding is often obscured by overlying swelling and soft-tissue tenderness. The location of pain from an LPT fracture contrasts with the site of pain in a lateral collateral ligament sprain, which typically is anteroinferior to the lateral malleolus.
In many regards, the history and physical exam findings parallel those of an inversion ankle sprain. Consequently, clinicians must have a high index of suspicion for LPT fractures in high-risk situations and seek a definitive diagnosis. LPT fractures should be considered in a "sprained ankle" that is persistently painful or unresponsive to treatment. Repeated clinical and radiologic examination are typically warranted.
Hawkins (8) and McCrory and Bladin (20) describe three different LPT fracture patterns (figure 2): Type 1 is a chip fracture off the anterior and inferior portion of the articular process of the talus that does not extend to the talofibular articulation. Type 2 is a simple fracture of the lateral process that extends from the talofibular articular surface to the posterior talocalcaneal articular surface of the subtalar joint. The fracture fragment may or may not be displaced. Type 3 is a comminuted fracture involving both the fibular and posterior calcaneal articular surfaces of the talus and the entire lateral process.
Diagnostic imaging. LPT fractures are notoriously difficult to recognize on plain radiographs (7,8,11,17,18), particularly if the clinician does not have a high level of suspicion. This fracture is best seen on a mortise view, just distal to the lateral malleolus, particularly with the foot in internal rotation (7,11,20,21). Some fracture patterns, particularly small chip fractures, are best seen on a lateral projection through the overlapping malleoli (8,11). McCrory and Bladin (20) recommend lateral radiographs be taken in 0° of dorsiflexion and 10° to 20° of inversion.
Computed tomography (CT, figure 3a) is useful when an LPT fracture is clinically suspected but plain radiographs are normal, when the patient has persistent pain after what appears to be an inversion ankle sprain, and to determine the size of fragments and extent of comminution when plain radiographs reveal an LPT fracture. CT can guide treatment by delineating the fracture pattern more clearly (19,22,23). Lateral tomography (figure 3b) is an alternative means of further evaluating LPT fractures, particularly if three-dimensional CT reconstruction is not readily available (24).
A further finding that should not be overlooked is an inferior fibula avulsion fracture. These avulsion fractures are commonly associated with injuries of the lateral ankle ligaments and are typically managed the same as inversion ankle sprain. However, posterior fibular avulsion fractures (radiographically, the "flake sign") are diagnostic of peroneal tendon subluxation or dislocation and can be seen in association with LPT fractures (22) (Peter C. Janes, MD, personal communication, February 1999). It is helpful to note this preoperatively because surgery for peroneal tendon subluxation may involve deepening of the peroneal tendon groove on the fibula.
Management. Treatment of LPT fractures is evolving. The size of the LPT fracture and the degree of comminution and displacement are the primary determinants of treatment.
Type 1 and nondisplaced type 2 fractures may be treated with immobilization in a short non-weight-bearing cast for 4 weeks, followed by a walking cast for 2 weeks. When the non-weight-bearing cast is removed, the patient may bear weight as tolerated and should begin exercises for ankle flexibility, strength, stability, and proprioception (25). Active assisted range of motion exercise may be required for stiff tibiotalar and subtalar joints.
For displaced type 2 and for all type 3 fractures, many authors recommend attempted closed reduction by an orthopedist with subsequent casting if reduction is successful (8). If reduction cannot be achieved or maintained—or the fracture is comminuted—open reduction and internal fixation or excision is generally recommended.
Other authors suggest that prolonged casting is often unsuccessful in all LPT fractures (7). These authors recommend early surgery to avoid prolonged subtalar stiffness. Kirkpatrick et al (16) recommend operative management for all but the smallest nondisplaced LPT fractures. We favor early operative intervention for large displaced or any type of comminuted fractures.
Open reduction and internal fixation is used if possible. However, fracture comminution often prevents restoration of joint surface anatomy, necessitating debridement and possibly drilling of the chondral surface to salvage the joint.
Postoperatively, a short leg cast is applied for 2 to 3 weeks. During this time, active range of motion of the metatarsophalangeal joints is allowed. At 3 weeks, the cast is exchanged for a splint, and the patient begins ankle range-of-motion exercises. Weight bearing is typically allowed when osseous union is evident, at about 6 weeks.
Whether treatment is operative or nonoperative, the patient can maintain conditioning through cross-training, including resistance training of the upper body and unaffected lower limb.
Prognosis. An unrecognized LPT fracture may result in nonunion, persistent pain, and long-term disability. Malalignment and osseous overgrowth are not uncommon in such cases. Despite the lack of epidemiologic data regarding the outcome of LPT fractures in snowboarders, it is well established that similar fractures among other populations have a poor prognosis, particularly if misdiagnosed or inappropriately managed nonoperatively. Several studies (6,8,17-19,21,23) have evaluated outcomes when LPT fractures were managed with casting only. Unless anatomic alignment was maintained, there was significant residual disability. At this time there is a lack of formal outcome studies evaluating operative management of LPT fractures.
Recommendations for Physicians and Patients
Physicians need to know the peculiar patterns of injury in snowboarders, such as more upper-extremity, ankle, and abdominal injuries and fewer serious knee injuries (1,3-5,9,10). Clinicians must also raise awareness of the commonly misdiagnosed LPT fracture, which can masquerade as a simple ankle sprain. One must maintain a high index of suspicion, pursue an accurate diagnosis, and treat the injury promptly.
Novice snowboarders can reduce their injury risk by taking lessons, using protective equipment including helmets and knee and elbow pads, and wearing soft-shell or hybrid boots. The value of wrist guards would seem obvious because beginners have a significantly increased risk of wrist fracture. However, there is a legitimate concern that use of wrist guards may transmit forces proximally and lead to more shoulder injuries. More studies are needed to determine this.
Snowboarding History and How-to
Snowboarding did not develop as a mainstream winter sport until the 1970s. Since that time the number of recreational and competitive snowboarders has increased steadily. Snowboarding appeared as an Olympic sport for the first time at the 192021 Winter Games in Nagano, Japan. Recent reports (1-6) estimate that 80% of children who participate in winter sports will have ridden a snowboard by their 12th birthday.
Snowboarders typically are men in their early 20s; men outnumber women three to one (1-6). However, this profile is changing with the increased participation of children, females, and adults over the age of 60 (2). Many participants are former Alpine skiers who now snowboard exclusively.
Since the inception of the sport, snowboarding injuries have been studied and compared with injuries in Alpine skiing (1,6-9). Initially there was widespread concern regarding liability and risk to others (2,4,5,10). Snowboarders were believed to make the slopes more dangerous for all (10). For this reason, and to appease resistant Alpine enthusiasts, many ski resorts initially banned snowboarders (2,10).
These safety concerns, however, were never fully borne out. Because of this and the increasing popularity of the sport, it has become financially prohibitive to continue the ban on snowboarding. Over 95% of ski resorts now allow snowboarding, and many cater specifically to this population by designating snowboard parks with man-made jumps and half pipes (see "Speaking Snowboard-ese," below) for enthusiasts to perform freestyle maneuvers (2).
Snowboarding is similar to skateboarding or surfing. The rider is fixed to the board, with both feet planted almost perpendicular to the direction of movement. Turns are "carved" by throwing body weight either forward or backward (right or left relative to the direction of travel), thus moving the rider's center of gravity so that one edge of the snowboard cuts into the snow and the other edge rises. Aerial maneuvers can be performed by launching off an upward incline—either the wall of a half pipe or a natural rise in terrain. In this way the snowboarder can perform any combination of rotation, inversion, or other aerial maneuver, often landing facing uphill.
Competitive snowboarding has several different classes of competition, including freestyle, slalom, and giant slalom, which are comparable to the similarly named Alpine ski events. A fourth class is "cross," which involves five snowboarders racing as a group down varied terrain that includes jumps. The riders must pass through designated gates, with the first three finishers entering the next round of competition. Finally, in "extreme" snowboarding, competitors are judged on style, control, fluidity, aggressiveness, and, most important, choice of line through the terrain.
Boards and Bindings
The spread of snowboarding has been accompanied by rapid advances in equipment design. Snowboards fall into two general categories. Slalom boards are longer and made for "carving" turns in a racing situation. They frequently have tips and tails that are wider than the center, similar to the "parobolic" skis that are now so popular. In comparison, freestyle boards are shorter and facilitate rapid turns and aerial maneuvers. Some freestyle boards are "twin tip" boards, with an identical nose and tail, allowing the snowboarder to ride "switch," ie, with either end forward (see "Speaking Snowboard-ese," below).
Boots are either soft-shell (typically a boot with a soft leather outer shell and a stiff inner boot for ankle support) or hard-shell (similar to a ski boot, but with more ankle flexibility). A "hybrid" boot has also been developed that has a hard-shell base and a soft synthetic or leather upper.
Soft-boot bindings consist of molded plastic shells with an extended Achilles ankle support and boot-encircling straps. Hard-boot bindings consist of a steel or plastic base plate with a heel and toe clip into which the hard-shell boot clicks securely. Both types of bindings are nonreleasable.
The following are terms commonly used in snowboarding circles—and half pipes. Physicians may want to brush up on them so that when a patient mentions a "stale fish" during history-taking, food poisoning won't necessarily be the first thing that comes to mind.
Carving/laying it out: Making a turn with the body almost parallel to the ground.
Catching air: Intentionally or unintentionally performing an aerial maneuver or otherwise leaving the ground during transit.
Digger/head plant/wreck: Wipeout.
Fakey/riding switch: Riding backward with board tail first and rear foot forward.
Goofy foot: Riding with the right foot forward.
Half pipe: A large, semicircular trough made of snow that allows the snowboarder to ride from side to side.
Jibber: A trickster who spends most of the time in the half pipe (uses a twin tip board).
Regular: Riding with the left foot forward.
Stale fish: An aerial maneuver in which the snowboarder catches air, grabs the front part of the board, and extends the legs ( performs a "stiff leg") while airborne.
Switch 540: Going into a jump backwards, then performing a 540° rotation in the air.
720: Performing two full rotations in the air (a 360 in skiing terminology would be a "heli").
Alpine, carving, or asym board: An often-asymmetric board used in conjunction with hard boots and a plate binding for high-speed "laid out" turns or racing.
Freeride or freestyle board: Of uniform width from nose to tail; shorter than carving boards and more maneuverable.
Twin tip or dual tip board: Has upturned nose and tail ends to allow the snowboarder to ride either way (switch); preferred by those who perform a lot of tricks and aerials.
Dr Boon is the chief resident, Dr Smith a senior associate consultant, and Dr Laskowski a consultant in the Department of Physical Medicine and Rehabilitation at the Mayo Clinic in Rochester, Minnesota. Dr Smith also is an assistant professor at the Mayo Medical School and a staff physician at the Mayo Sports Medicine Center in Rochester. Dr Laskowski also is an associate professor at the Mayo Medical School and a co-director of the Mayo Clinic Sports Medicine Center. Address correspondence to Jay Smith, MD, Dept of Physical Medicine and Rehabilitation, Mayo Clinic, 200 1st St SW, Rochester, MN 55905; address e-mail to [email protected].