Fractures of the Talus and Subtalar Dislocations

1. Fractures of the Talus and Subtalar Dislocations David Sanders MD, MSc, FRCSC London Health Sciences Centre University of Western Ontario London, Ontario, Canada Created March 2004; Revised August 2006

2. Outline: Talar Neck Fractures Anatomy Incidence Imaging Classification Management Complications Talar body, head and process fractures Subtalar dislocations Classification Management Outcomes

3. Anatomy • Surface 60% cartilage • No muscular insertions

4. Blood Supply Arterial supply: • Artery of tarsal canal • Artery of tarsal sinus • Dorsal neck vessels • Deltoid branches lateral medial Inferior view of talus, showing vascular anastomosis

5. Vascularity • Artery of tarsal canal supplies majority of talar body Top View Side View DeltoidBranches Superior Neck Vessels Artery of Tarsal Canal Posterior tubercle vessels Artery of Tarsal Canal Superior Neck Vessels Posterior tubercle vessels Artery of Tarsal Sinus Artery of Tarsal Sinus

6. Incidence • 2 % of all fractures • 6-8% of foot fractures • Importance due to high complication rates • avascular necrosis • post-traumatic arthritis • malunion

7. Mechanism of Injury • Hyperdorsiflexion of the foot on the leg • Neck of talus impinges against anterior distal tibia, causing neck fracture • If force continues: • talar body dislocates posteromedial • often around deltoid ligament

8. Injury Mechanism • Previously called “aviator’s astragalus” • Usually due to motor vehicle accident or falls from height • Approximately 50 % have multiple traumatic injuries

9. Biomechanics • Theoretical shear force across talar neck: • 1200 N during active motion [Swanson 1992]

10. Imaging Complex 3-D structure Multiple plain film orientations: Canale View

11. Canale View • Ankle plantarflexion • 15 degree pronation • Tube 15 degree off vertical Canale View

12. CT Scan • Can be a useful assessment tool • Confirms truly undisplaced fractures • Demonstrates subtalar comminution, osteochondral fractures

13. MRI Scan • Primary role in talus injuries is to assess complications, especially avascular necrosis • May be poor quality if extensive hardware present Zone of osteonecrosis following distribution of Artery of Tarsal Canal

14. Talar Neck Fractures: Classification • Hawkins 1970 • Predictive of AVN rate • Widely used

15. Hawkins 1 I: undisplaced AVN 0 – 13 %

16. Hawkins 2 Displaced fracture Subtalar subluxation A) fracture line enters subtalar joint B) subtalar joint intact AVN 20 – 50 %

17. Hawkins 3 Subtalar and ankle joint dislocated Talar body extrudes around deltoid ligament AVN 83 – 100 %

18. Hawkins 4 Incorporates talonavicular subluxation Rare variant Complex talar neck fractures which do not fit classification can be included

19. Classification: • Comminution: • An important additional predictor of results, especially regarding: • Malunion • Subtalar joint arthritis

20. Goals of Management • Immediate reduction of dislocated joints • Anatomic fracture reduction • Stable fixation • Facilitate union • Avoid complications

21. Treatment of Talar Neck Fractures • Emergent reduction of dislocated joints • Stable internal fixation • Choice of fixation and approach depends upon personality of fracture

22. Treatment of Talar Neck Fractures • Post operative rehabilitation: • Sample protocol: • Initial immobilization, 2-6 weeks depending upon soft tissue injury and patient factors, to prevent contractures and facilitate healing • Non weight-bearing, Range of Motion therapy until 3 months or fracture union

23. Hawkins I Fracture Options: Non-Weight-Bearing Cast for 4-6 weeks followed by removable brace and motion Percutaneous screw fixation and early motion

24. Hawkins II, III, and IV Fractures: • Results dependent upon development of complications • Osteonecrosis • Malunion • Arthritis

25. Case Example 29 yo male ATV rollover Isolated injury LLE

27. Diagnosis • Hawkins’ 3 talar neck fracture • Associated comminution, probably involving medial column and subtalar joint

28. Controversies for this Case: ???? • Surgical timing • Closed reduction • Surgical approach • Fixation

29. Surgical Timing • Emergent reduction of dislocated joints • Allow life threatening injuries to take priority and resuscitate adequately first

30. Closed Reduction? • May be very useful, particularly if other life threatening injuries preclude definitive surgery • Difficult in Hawkins’ 3 and 4 injuries

31. Closed Reduction Technique: • Adequate sedation • Flex knee to relax gastrocs • Traction on plantar flexed forefoot to realign head with body • Varus/valgus correction as necessary

32. Closed Reduction Example

33. External Fixation • Limited roles: • Multiply injured patient with talar neck fracture in whom definitive surgery will be delayed • Temporizing measure to stabilize reduced joints

34. Surgical Approaches: Options • 1 incision techniques: • Anteromedial or • Anterolateral • Problem: difficult to visualize talar neck and subtalar joint without significant soft tissue stripping • Benefit: potentially less skin injury

35. Surgical Approaches: Options • 2 incision technique: • Anteromedial and direct lateral • Problem: 2 skin incisions, close together • Benefit: excellent fracture visualization at critical sites of reduction and subtalar joint

36. 1st Approach: Anteromedial Medial to TA and Anterior Compartment contents Make incision more posterior for talar body fractures to facilitate medial malleolar osteotomy

37. 1st Approach: Anteromedial • Provides view of neck alignment and medial comminution

38. 2nd Approach: Direct Lateral • Tip of Fibula directly anterior • Mobilize EDB as sleeve • Protect sinus tarsi contents

39. 2nd Approach: Direct Lateral • Visualizes Anterolateral alignment and subtalar joint • Facilitates Placement of “Shoulder Screw”

40. Protect the Skin Post Op

41. Fixation Options • Stable Fixation to allow early motion is the goal • 1200 N stress across talar neck during early motion • (Swanson JBJS 1992)

42. Surgical Tactics: Fixation • Anterior • Partial threaded screws • Fully threaded screws • Mini-fragment plates • Posterior • Lag screws Implant selection depends upon injury, degree of comminution, bone quality But should be strong enough to withstand motion

43. Posterior to Anterior Fixation: 90° • stronger than anterior to posterior fixation with 2 screws • Able to withstand the theoretical shear force of active motion (Swanson, JBJS 1992) • Screws perpendicular to fracture site

44. Anterior Screw Fixation: Non-comminuted fractures: • Easy to insert under direct visualization and no cartilage damage • Displaced type 2: 3 A-P screws including medial “buttress” fully threaded cortical screws and lateral “shoulder” screws

45. Anterior Screw Fixation: Comminuted fractures: • Buttress screw: comminuted column; compression screws through non-comminuted column • Mini-fragment screws for osteochondral fragments • Consider Titanium for MRI

46. Anterior Plate Fixation: • Comminuted fractures: • Medial and / or lateral mini-fragment plates

47. Complications AVN Malunion Nonunion Arthritis

48. AVN: Incidence after Talus Fracture Canale (1972): I: 15 % II: 50 % III: 85 % IV: 100 % Behrens (1988): Overall 25 % Ebraheim/Stephen (2001): Overall 20 %

49. AVN: Diagnosis • Hawkins’ Sign: Xray finding 6-8 weeks post injury • Presence of subchondral lucency implies revascularization

50. AVN: Imaging • Plain radiographs: sclerosis common, decreases with revascularization • MRI: very sensitive to decreased vascularity