Shepherds Fracture Overview
Shepherds fracture is the fracture of the lateral tubercle of posterior process of the talus and is sometime mistaken for symptomatic Os Trigonum.
Possible Causes of Shepherds Fracture
- Inversion ankle injury / sprain may avulse tubercle leaving posterior talofibular ligament intact
- Extreme ankle plantarflexion / equinus
Symptoms of Shepherds Fracture
- Patients may present with ankle sprain history or symptoms
- Patient may have posterolateral ankle tenderness on palpation
- Pain with range of motion of ankle joint, especially with plantar flexion of the ankle
- Motion of the great toe may cause pain to the back of the ankle as flexor hallucis longus rubs over the fracture site (between medial and lateral tubercle)
– lateral x-ray view of the foot:
- postero-lateral tubercle is seen on the lateral view
- look for marrow edema in the back of the talus
- with fluid surrounding the Os and associated marrow edema (absence of talar marrow edema), then consider os trigonum as the cause of symptoms
Hawkins described three different patterns in his series of lateral process fractures.
I. Simple fractures: extending from the talofibular articular surface to the posterior talocalcaneal articular surface of the subtalar joint.
II. Comminuted fractures: involving both the articular surfaces and the entire lateral process.
III. Chip fractures: arising from the anterior and inferior portion of the posterior articular process involving only the subtalar joint and not extending into the talofibular articulation.
Boack described a modified classification system that can be applied to fractures of either the lateral or the posterior processes.5 This classification includes four types of fracture, each type subdivided according to severity of bony injury, degree of chondral lesion and ligamentous stability. Based on their description, lateral and posterior process fractures are classified into four types.
Type 1: a small chip or avulsion fracture (< 0.5 cm):
1a - Small (extra-articular) fragment of the lateral process of the talus;
1b - Small fragment of the isolated medial tubercle of the posterior process;
1c - Small (intra-articular) fragment of the lateral process of the talus.
Type 2: an intermediate fragment (0.5 to 1.0 cm) with some displacement:
2a - Extends into the subtalar joint but not to the talofibular joint;
2b - Isolated fracture of the entire lateral tubercle of posterior process.
Type 3: a large fracture fragment (> 1 cm) with associated damage to both the ankle and the subtalar joints:
3a - Single large fragment of the lateral process extending from the talofibular articular surface to the posterior facet of the subtalar joint;
3b - Comminuted fracture of the entire lateral process;
3c - Fracture of the entire posterior process of the talus.
Type 4: a severe form of fracture of either of the processes and associated instability or dislocation of the subtalar joint.
Shepherd’s Fracture Treatment Classification
The treatment strategy based on Boack’s classification is summarized
|1a, 1b||< 0.5 cm,
|1c||< 0.5 cm, displaced, intra-articular||Arthroscopic excision|
|2a, 2b||0.5-1 cm, displaced||Arthroscopic assessment of chondral lesion|
|3a||> 1 cm single fragment||Arthroscopic assisted screw fixation|
|3b||> 1 cm or multifragmentary||Open reduction and internal fixation|
|3c||Entire process fracture||Open reduction and internal fixation|
|4||Fracture associated with subtalar dislocation||Emergency reduction, subsequent arthroscopic assessment of chondral lesion|