Anatomy
Can be divided into 6 surfaces: supererior, inferior, medial, lateral, anterior, and posterior.
- Superior - Beak of calcaneus supports anterior facet, sustentaculum tali supports middle facet
- Lateral - flat with groove and trochlea centrally for the peroneal tendons. Impingement of the peroneal tendons are a common complication of lateral displacement (lateral wall "blow-out") of calcaneal fractures.
The calcaneus is composed of a shell of thin cortical bone. The inner cancellous bone displays a pattern which resembles the static and dynamic stresses placed on the bone.
- Traction trebeculae radiates from inferior cortex
- Compression trebeculae converge to support anterior and posterior facets
- Intersection of trebecular bone known as "thalamic portion of calcaneus".
-
Neutral triangle or Ward's triangle - area of sparse trebecular bone between compression and traction trebeculae.
- Lies beneath the angle of Gissane's and carries blood vessels to medullary cavity of calcaneus. This is the weakest portion of the calcneus as it is almost completely void of bone.
Superiorly:
- interosseous talocalcaneal ligament plays an important role in calcaneal fracture patterns.
Lateral
- Thin cortical wall (involved in blow outs)
- Soft tissue: can get tendonitis and nerve entrapment with fracture
Medially
-
Sustentaculum tali – keystone of calcaneal fracture repair
- Sustentaculum tali fragment – a.k.a. – anterior medial fragment, McReynold’s fragment, thalamic fragment
- Sustentaculum tali retains its position in fxs (maintains its anatomic relationship)
- Strong ligamentous attachment – deltoid, talocalcaneal ligaments and flexor hallucis longus à all play a role in maintaining the fx fragments
Anteriorly
- CC- joint – often have fractures that extend through the CC joint
Talar relationship to calcaneus
- Calcaneus is laterally displaced on the main body of the talus
- Force of ground pushes calcaneus up, most of weight is centered medially over the sustentaculum tali