Lateral process of the Talus

Fractures of the lateral process of the talus are rare, often overlooked initially and misdiagnosed as a severe ankle sprain.

Misdiagnosis can lead to malunion, nonunion and degenerative changes.

"Snowboarders fracture".

Ankles are involved in 12%–17% of snowboarding-related injuries. A fracture to the lateral process of the talus in snowboarder's, may account for as many as one-third of ankle fractures in this population.

When the fracture extends into the subtalar joint, persistent pain and subtalar stiffness frequently occurs. Nonunion is a frequent complication of displaced fractures.

Anatomy

The lateral process of the talus is a broad-based, wedge-shaped prominence of the lateral talar body. The lateral process articulates with the fibula, functioning as a load-bearing structure at that articulation, and with the posterior calcaneal facet, playing a part in subtalar motion. The lateral talocalcaneal ligament usually originates from the tip of this process.

Mechanism of injury

The mechanism of injury is thought to be due to a compression force that shears off the process when the inverted foot is severely dorsiflexed. Srinivasan et al (2002) in a cadaver study suggested, eversion of an axially loaded and dorsiflexed ankle may be an important injury mechanism in snowboarders.

Classification

Tucker et al. and Cantrell et al. both review classification and treatment of this fracture.

Hawkins classified three types of lateral process fractures:

Simple fracture extending from the talofibular to the talocalcaneal joint
Comminuted involving the entire lateral process
Chip fracture anteroinferiorly involving only the subtalar joint.

In comminuted fracture or small displaced fragment, it is recommended to excise the fragments. In large displaced fragment it should be anatomically reduced and fixed.

Clinical

The mechanism of injury, symptoms and signs are similar to sprains of the lateral colateral ligaments.

On examination one finds swelling and ecchymosis localized to the lateral aspect of the ankle. There is usually point tenderness over the lateral process just anterior and inferior to the tip of the lateral malleolus.

This similarity to lateral ankle sprains often leads to misdiagnosis and a delay. Hence in any patient with persistent symptoms following an ankle sprain the diagnosis of lateral process fracture should be considered.

Radiographs

Most of these fractures can be seen on standard radiographs of the ankle joint.

The mortise view helps because the lateral process lies in the frontal plane in this projection. Computed tomography may confirm a suspected fracture and help define size, comminution and degree of articular involvement.

Treatment

Unreduced, displaced fractures frequently do not unite, and if union does occur, a residual malalignment of the subtalar joint may produce persistent symptoms.

Treatment depends on:

Displacement
Degree of comminution
Fragment size - large fragments likely to involve subtalar joint

Type I

Large, Displaced fracture (>2mm, >1cm)

MUA and cast ( Must achieve anatomical reduction viz subtalar joint)
ORIF - K wires/ lag screw/ cannulated screw

Type II

Comminuted fracture

Fracture fragment excision

Type III

Chip fracture and undisplaced fractures

Below knee cast 6 wks (NWB for first 4 wks)

Complications

Non union
Pain - subtalar joint

References

Dimon JH. Isolated displaced fracture of the posterior facet of the talus. J Bone Joint Surg 1961;43A:275–281

Hawkins LG. Fracture of the lateral process of the talus. J Bone Joint Surg 1965;47A(6):1170–1175.

Unis, Douglas; Haddad, Steven L. Outcomes and advances in hindfoot fractures. Current Opinion in Orthopedics. 12(2):93-99, April 2001.

FRACTURE OF THE LATERAL PROCESS OF THE TALUS. M. Nyska, K. Marin, Y. Mattan; JBJS B November 1996; Vol 79-B Supplement

Srinivasan, S CM; Funk, J R; Crandall, J R LATERAL PROCESS OF TALUS (SNOWBOARDER'S) FRACTURE - MECHANISM OF INJURY. Journal of Bone & Joint Surgery - British Volume. 85-B SUPPLEMENT II:176, 2003.

Kouvalchouk, J. F.; Collin, Ph.; Haddoun, A. R. SEQUELAE AFTER FRACTURE OF THE LATERAL PROCESS OF THE TALUS. Journal of Bone & Joint Surgery - British Volume. 84-B Supplement I:69, 2002.

Weir, Erica Snowboarding injuries: hitting the slopes. CMAJ Canadian Medical Association Journal. 164(1):88, January 9, 2001.

Leibner, Efraim D; Simanovsky, Naum; Abu-Sneinah, Kareem; Nyska, Meir; Porat, Shlomo. Fractures of the Lateral Process of the Talus in Children. Journal of Pediatric Orthopaedics, Part B. 10(1):68-72, January 2001.

Mc Crory P, Bladin C. Fractures of the lateral process of the talus: a clinical review. "snowboarder's ankle" Clin J Sports Med. 1996;6:124-128.