A Closer Look At Lateral Talar Process Fractures With Snowboarding Injuries

   As the winter season continues, physicians need to become more aware of snowboarding injuries. The number of ankle injuries continues to rise and, in particular, lateral talar process (LTP) fractures seem to be occurring more frequently within the snowboarding population.

   Kirkpatrick, et al., conducted a prospective study of 3,213 snowboarding injuries that occurred at 12 Colorado ski resorts between 1988 and 1995.1 These injuries consisted of 15.3 percent injuries to the ankle and 1.8 percent injuries to the foot. In regard to the ankle injuries, 44 percent of injuries were related to fractures and 52 percent were sprains.

   Specifically, there were 216 ankle fractures. Seventy-eight of these ankle fractures were talar fractures and 74 of these were LTP fractures. These LTP fractures accounted for 34 percent of ankle fractures and 15 percent of all ankle injuries. According to other research, there is a 15-fold increase in the risk of LTP injuries with snowboarding in comparison to the general population. 2

   Traditionally, patients with ankle injuries related to snowboarding presented to the hospital with lateral ankle pain, swelling and instability. Most new patients during the sport’s conception underwent workups for lateral ankle sprains. It soon became apparent that under-treating snowboarding injuries could result in long-term sequelae such as malunion, nonunion, subtalar and/or ankle arthritis.

   However, time has provided a greater understanding of the anatomy and the biomechanics involved with snowboarding. Currently, lateral ankle sprain treatment includes radiographic analysis for fracture and joint disruption. However, due to the nature and location of this particular injury, it is still difficult to differentiate between a lateral ankle sprain and a fracture of the lateral talar process.

Understanding The Relationship Between The LTP And The STJ

   Little is known about the functional significance of the lateral talar process, let alone what stabilizes it during activity. 3 We do know that the lateral talar process is a wedge-shaped prominence of the lateral aspect of the talar body that extends from its articulation with the medial aspect of the fibular articular surface distal to the posteroinferior surface of the talus. 4 Therefore, “a fracture of the lateral process of the talus involves both the talofibular articulation of the ankle joint and the posterior talocalcaneal articulation of the subtalar joint.”4

   Cadaveric studies have clarified how much these joints are affected by LTP injuries. In a 2007 study, researchers discussed the stability of the lateral side of the ankle by describing three ligamentous attachments to the LTP that create a “circumferential skirt” of tissue. These attachments include the lateral talocalcaneal, anterior talofibular and posterior talofibular ligaments.3 Historically, surgeons did not excise large fragments but utilized open reduction internal fixation (ORIF) due to the fear of creating instability to the subtalar joint (STJ).5,6

   DiGiovanni, et al., discovered with cadaveric anatomical dissection that this fear was unfounded.3 Their thesis, arbitrarily derived from Heckman in 1996 and DiGiovanni in 2003, was that excision of a LTP fracture fragment of 1 cm3 would only affect three lateral stabilizing ligaments that stabilize the ankle joint and not the STJ. 7,8

   The lateral talocalcaneal is the only ligament that crosses the STJ while the other two are specific to the ankle joint. The lateral root of the extensor retinaculum, cervical and interosseous ligaments still remain unaffected by LTP fractures because they do not insert into the LTP, and therefore continue to provide stability to the STJ.

   In relation to this study, further research examined the effect of excision of a 1 cm3 fragment from the LTP to the ankle and subtalar joints9 The results indicated that there was no instability at the ankle or at the subtalar joint upon removal of the fragment after comparing non-stressed and stressed measurements.

Examining Possible Etiologies Of LTP Fractures

   What exactly is the mechanism of LTP injuries? Many years of study have gone into identifying and determining appropriate ways of treating what was initially a very rare occurrence until the introduction of snowboarding.1,10

   Historically, Hawkins described the mechanism of injury as dorsiflexion of the ankle associated with inversion.11 Reinforcing this statement, Huson described the posterior talar and calcaneal facets as congruous in stance. 12

   However, upon inversion of the STJ, the talus rotates or shifts laterally with the posterior aspect of the lateral process of the talus abutting against the posterior articular process of the calcaneus. A dorsiflexory force initiated at this incongruous position would ultimately cause a fracture of the lateral process.

   This is distinct from what researchers earlier thought of as an avulsion fracture caused by the tension on the lateral talocalcaneal ligament. Hawkins indicated that anatomical dissections have proven that the lateral talocalcaneal ligament is nothing more than a thickening of the lateral aspect of the STJ capsule, and an LTP fracture is not associated with STJ dislocation with rupture of this ligament.11 With this concept and theory, recent literature has expanded the understanding of a true LTP fracture and the mechanism of injury.

   In 2001, Boon, et al., recognized that axial loads on a dorsiflexed position of the ankle while being inverted may be a cause of the injury. 13 However, they continued to hypothesize that there may be an external rotational component. Due to the high number of nonunions and malunions with inadequately treated LTP injuries, researchers thought that “the rotatory and hinge movements of the talocrural and STJ are at a higher risk for avascular necrosis.” 13

   They obtained 10 fresh cadaveric ankles with an average age of 79 years. Researchers induced lateral talar process fractures under specific loading conditions. They placed four out of 10 specimens in 20 degrees of dorsiflexion and 10 degrees of inversion with axial loading only. There were no LTP fractures induced in this group. The group that experienced lateral rotation (external) of 20 degrees sustained LTP fractures.

   The minimum load was 2200 N while the maximum load was 8900 N. Researchers thought the variation in loading forces was due to the conditions of the specimens themselves.

Do The Boots Contribute To These Injuries?

   With these results, Boon, et al., noted that it is unclear whether boot design has an effect on injury outcomes.13

   With this in mind, researchers assessed three types of boots. Kirkpatrick, et al., indicated that 77.3 percent of snowboarders used soft boots, 8.5 percent of patients used hybrid boots and 14.1 percent used hard boots. 1 Soft boot wearing was more predictive of soft tissue ankle sprains and non-talar fractures as opposed to hard boots. They found that hybrid boots stabilize against ankle sprains better than soft boots and also significantly reduce the number of LTP fractures. According to Kirkpatrick and colleagues, there was a significant increase in the presence of LTP fractures with the use of hard boots.1

   However, Boon, et al., theorizes that given the fixed position of the foot when it is placed in a hard boot, it would be unlikely that the hindfoot would be subjected to inversion and dorsiflexion in the first place.13 Therefore, they suggested an alternate mechanism of the injury to the LTP: external rotation with dorsiflexion and inversion.

What The Studies Reveal About Inversion And Eversion With LTP Fractures

   In 2003, Funk, et al., introduced a new theory for the development of LTP fractures with snowboarding. 2 Researchers obtained 10 cadaveric legs to determine whether there was a difference in the number of LTP fractures with inversion or eversion coupled with dorsiflexion and axial loading. The result indicated the need for a rotational component to induce the fracture.

   The rationale began with the work of Wagner, et al., and Wang, et al. 14,15 These pressure-sensitive studies have contradicted that inversion is necessary to induce a fracture of the lateral process of the talus. In fact, these studies have demonstrated that stress distributed across the STJ upon inversion actually deviates medially, whereas the stress disperses and concentrates laterally in eversion.

   The position in which one rides a snowboard also favors eversion. Kirkpatrick, et al., noted that the most common mode of injury was from falling (74.7 percent). The next most common injuries were due to twisting (11.6 percent) and collision with a tree (8.2 percent).1

   When falling induces injury, it reportedly occurs parallel to the long axis of the snowboard. Most snowboarding injuries happen to the leading foot (the foot that points downhill) at the time of the injury. 1,10,16 This illustrates the importance of foot position to the mechanism of injury because the position of the foot is in a natural state of dorsiflexion, particularly when riding toe side (facing the mountain).

   In the aforementioned study by Funk and colleagues, they dorsiflexed the specimens at the ankle 30 degrees to the horizontal and subjected them to various amounts of inversion rotation or eversion rotation (48 to 62 degrees excursion).2 All inverted positions (four total specimens) with dorsiflexion failed to produce a fracture of the LTP. The remaining six were subjected to eversion and all produced fractures to the LTP. All specimens, both inverted and everted, were exposed to a constant axial loading force of 2.5 kN.

A Pertinent Primer On Injury Classification

   Hawkins described the fracture of the lateral talar process in 1965. At this time, there was lack of consensus in descriptive terminology and minimal data from small population samples. The largest accumulation of data was from a study in 1943 by Marotolli, who added four patients of his own with LTP fractures to six already collected with no follow-ups to treatment.17 Hawkins developed a classification system based on 13 patients with LTP fractures for identification and treatment. 11 He described the following three types of LTP fractures.

   Type I. This is a simple fracture of the lateral process of the talus that extends from the talofibular articular surface down to the posterior talocalcaneal articular surface of the subtalar joint.

   Type II. This is a comminuted fracture that involved both the fibular and posterior calcaneal articular surfaces of the talus and the entire lateral process.

   Type III. This is a chip fracture of the anterior and inferior portion of the posterior articular process of the talus. Be aware that one can only view type III fractures on a lateral radiograph or CT scan within the region of the sinus tarsi.

   Bladin and McCrory, as well as others, are reorganizing Hawkins’s original classification in an attempt to better guide treatment regimens.11,18,19 According to their categorization, type I is a chip fracture, type II is a single large fragment and type III is a comminuted fracture.

   After determining the fracture type, identify whether the fracture is displaced or non-displaced. As for primary therapy, non-displacement injuries receive conservative treatment whereas displacement injuries receive ORIF or surgical debridement. If necessary, one can perform secondary therapy (debridement) upon non-displaced primary therapy failures (debridement).

   Funk, et al., describes yet another organization of the original classification in order to provide more detail, which may lead to a better understanding of diagnosing these injuries and making decisions on appropriate treatment.2 This classification follows the current logic of the Orthopaedic Trauma Association’s AO coding (fracture type=A,B,C; severity=1,2,3).

   Type A: extraarticular ligamentous avulsion
   Type B1: simple chip fracture of the posterior talocalcaneal (TC) joint surface
   Type B2: comminuted chip fracture of the posterior talocalcaneal joint surface
   B1 and B2: do not involve the talofibular joint surface
   Type C1: single large complete fragment fracture
   Type C2: comminuted fracture involving both surfaces of the posterior talocalcaneal and talofibular joints
   C1 and C2 both involve the TC and the talofibular joint surfaces.

   Funk, et al., indicated that by using this classification, one can make better decisions in treatment planning for LTP fractures.2 They suggested that type A and B1 fractures respond well to conservative casting methodology while types B2, C1 and C2 may respond better to surgical intervention.

What You Should Know About Treatment

   Surgical texts describe treatment regimens for LTP fractures in terms of the Hawkins classification. Mann and Coughlin indicate that size, degree of comminution and displacement of the LTP are critical in determining the appropriate treatment plan. 4 Historically, Hawkins and Shelton recommend initial closed reduction of all fractures of the lateral talar process and subsequent non-weightbearing with a below knee cast for four weeks, and partial weightbearing for an additional two weeks.11,20

   Further, Mann and Mukherjee, et al., state that a single large fragment requires accurate reduction by ORIF to restore and maintain STJ congruity while one would treat comminuted fractures by removing the fragments.4,21 Funk, et al., describe surgical intervention as acceptable and necessary when the fragments are large (>1 cm), and significantly displaced (>2 mm) or comminuted.2

   A recent study by von Knoch, et al., reported treatment outcomes of 23 LTP fractures from 1995 to 2001 with a mean follow-up of 3.5 years.10 Treatment was based on fracture type, the degree of displacement of the fracture, and the presence or absence of associated injuries.

   Utilizing Hawkins classification type I, II and III fractures that were displaced less than 1 mm without any other associated injuries (30 percent), researchers provided non-operative treatment. The non-operative regimen included six weeks of Aircast immobilization with partial weightbearing (15 kg) until there was radiographic evidence of healing, and then patients could begin full weightbearing.

   The researchers performed open reduction on the majority of individuals (70 percent) with a severely displaced or comminuted Hawkins type II or III LTP fracture. When it came to fragmentary injuries, the surgeons applied fixation in a craniomedial direction through the talus while they removed comminuted fragments.

   The researchers used the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot (ankle-hindfoot) scoring to measure postoperative pain, function and alignment to determine the degree of success. Non-operative treatment and open reduction of fractures both had an average mean score of 94. Individual scoring is worth noting because alignment was a perfect 10 out of 10 for both conservative and invasive modalities. The average pain score was 36 out of 40 and the average function score was 48 out of 50.

   However, what researchers deduced from this was that approximately 45 percent presented with mild to moderate degenerative changes (subchondral lesions) of the STJ. Most of the degenerative changes occurred in the surgically treated patients with the more severe injury.10

   A similar study by Valderrabano, et al., reviewed 26 patients from 1999 to 2001 for sustained LTP fractures. 16 Researchers obtained appropriate radiographic views due to a high suspicion of LTP fracture. Eighty percent of all reported cases were classified as type II fractures, type I fractures accounted for 15 percent and type III fractures accounted for 5 percent, according to the Bladin-McCrory injury classification system.

   Again, patients underwent treatment according to type and severity. Type I and III cases were non-operative. In regard to patients with type II injuries, researchers used non-operative treatment in two cases and employed open reduction in 14 cases. Each type had only one that required revision.

   The AOFAS hindfoot scoring system determined that the mean average score was approximately 93 points out of 100. Again, alignment was a perfect 10 out of 10 at 3.5 years. Function was approximately 47 out of 50.

   According to Sariali, et al., in their review of 43 patients over 17 months, delayed diagnosis and under-treatment of LTP fracture inevitably result in specific pseudoarthrosis and/or STJ osteoarthritis.22 Still, with such results, it is hard to deduce exactly how many will experience degenerative changes of the STJ secondary to trauma and by how much. Understandably, though, there will be some degree of change nonetheless. These results continue to illustrate that early detection and appropriate treatment will result in satisfactory outcomes.22

   Based on these results, Langer and DiGiovanni have recently conducted further evaluation about the incidence of fracture types of the LTP.23 These injuries were not specific to the snowboarding mechanism as researchers assessed these as isolated LTP fractures in the general trauma population. This retrospective review of patients between 2000 and 2005 demonstrated that there was a 10.4 percent incidence of LTP fractures in the general trauma population. They found that the most common presentation was a single large fracture fragment. This was followed by a non-articular chip fracture and ended with the comminuted type of fracture.23

In Conclusion

   Since its conception, snowboarding has increased the number of ankle injuries we see in practice. With the knowledge that we have gained from the early works of Hawkins as well as recent contributions by Boon, Funk, Kirkpatrick and many others, there is a better understanding about LTP injuries that occur with snowboarding.1,2,11,13

   One may utilize one of the aforementioned classifications to help determine the appropriate treatment regimen. However, it remains up to the physician’s knowledge and experience to determine whether the injury is significant enough to require ORIF or whether one should administer conservative methodology.

Mr. Robertson is a fourth-year medical student at the New York College of Podiatric Medicine.
Dr. Khan is a Clinical Assistant Professor in the Department of Medical Sciences at the New York College of Podiatric Medicine.

Dr. Richie is an Adjunct Associate Professor in the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt College. He is a Past President of the American Academy of Podiatric Sports Medicine.

Editor’s note: For related articles, see “Secrets To Treating Ankle Fractures In Athletes” in the January 2007 issue of Podiatry Today or “Ski Boot Orthotics: Plowing Through The Options” in the December 2002 issue.

References:

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