Anatomy
| Facets | Tuberosities | Process |
|---|---|---|
| Posterior facet / subtalar joint | Posterior - tendoacilles | Anterior - calcaneocuboid joint |
| Middle facet (sustenaculum tali) | Medial - adductor hallucis, plantar fascia | |
| Anterior facet | Lateral - abductor digiti minimi |
Etiology
Usually fall from height - calcaneum driven up against talus
Epidemiology
10% bilateral
10% associated with lumbar spine fracture
Fracture patterns
Primary fracture line
- lateral process of talus driven into crucial angle
- starts at lateral wall near tarsal sinus
- passes obliquely across posterior facet
- exits at medial wall posterior to sustentaculum tali
Secondary fracture lines
- passes immediately behind the posterior facet of the subtalar joint
- exits posterior to posterior facet & anterior to tendoachilles insertion
- creates thalamic portion containing posterior facet
Common fracture fragments
| Sustanacular | Superolateral | Lateral wall | Posterior tuberosity |
|---|---|---|---|
| Superomedial |
Lateral fragment of posterior facet
|
Tongue fracture | |
| Attached to talus by deltoid ligament | Thalamic fragement | Secondary fracture line exits below tendoacilles |
Examination
EMST
Lumbar spine
- log roll
- injury in 10%
Other heel
- 10% bilateral
Foot
- compartment syndrome
Effects
- loss heel height
- increased heel width
- varus heel
X-ray Views
Lateral
- Bohler's angle
- crucial angle Guisane
Harris axial views
- 45o axial of heel
- normally hindfoot 10o of valgus
- view varus malalignment & heel width
Oblique view
- CCJ
Broden's view
- visualise posterior facet
- IR foot 45 degrees with ankle neutral initially
- plantar flex the foot 10° increments from 10° to 40
- alternatively angle beam cephalad in 10 degree increments
- replaced by CT
- useful intra-op to assess congruency of STJ
Xray Angles
1. Bohler's angle (20-40°)
Highest point on anterior process to highest point on posterior facet to highest point on tuberosity
- represents the height of the calcaneus
- angle of </=0° is associated with a poor outcome
Indicates
- the posterior facet/ STJ has collapsed
- proximal displacement of tuberosity
2. Crucial Angle Guisane 120-140°
- lies inferior to lat process of the talus
- where the primary fracture line starts
- disrupted in joint depression fracture
Formed by 2 cortical struts
a) lateral border of posterior facet
b) anterior to beak of calcaneus
Thus see
- decrease in Bohlers angle
- increase in Gissanes angle
CT scan
3 mm cuts
- foot flat on table
- transverse and coronal
- sagittal reconstruction
1. Axial
- parallel to bottom of foot
- information regarding CCJ & sustentaculum
2. Coronal plane
- perpendicular to posterior facet
- information regarding posterior facet and number of fragments +
- sustentaculum / heel shape / position peroneal & FHL tendons
3. Sagittal
- Bohlers angle / depression of posterior facet
Sanders Coronal CT Classification
Summary
- calcaneum divided into 3 columns by 2 lines
- based on lateral, central & middle columns of posterior facet
- number of longitudinal fracture lines on coronal CT through post facet
Position
- patient positioned supine in scanner with hips & knees flexed 45°
Type I
- undisplaced, irrespective of number of parts
- cast
Type II
- 2 parts of the posterior facet
- > 2mm displacement
- subgroups A,B,C based on primary fracture line
- more medial the fracture line (C), the more difficult to ORIF
Type III
- 3 part (AB, AC, BC)
- ORIF / fusion
Type IV
- highly comminuted
- primary fusion