- Sub Talar Dislocation
- Subtalar Fusion
- Transverse tarsal joint
- Triple Arthrodesis
- Discussion:
- anatomy:
- axis of rotation:
- axis of subtalar joint is approx 42 deg upward from the horizontal in saggital plane & 16 to 23 deg medial to midline of foot in transverse plane;
- upward axis of rotation of the subtalar joint is about 45 deg, and therefore ratio of inversion and eversion versus internal and external rotation is about 1:1;
- medial axis is only 16 to 23 deg and therefore the amount of dorsiflexion and plantar flexion that occurs at the subtalar joint is slight;
- facets:
- anterior facet
- middle facet
- posterior facet
- Role of Ankle & Subtalar Joint in Gait:
- motion:
- coupled dorsiflexion, abduction, & eversion = pronation
- coupled plantar flexion, adduction, & inversion = supination
- articulation between talus & calcaneus allows further rotation of proximal limb to occur over fixed foot because of axis of rotation;
- average ROM of pronation is 5 deg & supination is about 20 deg
- joint normally has 40 deg of motion, w/ an axis of rotation that passes through medial dorsal navicular & plantar lateral aspect of the calcaneus;
- total ROM ranges from 10 deg to 65 deg w/ an avg range of 40 deg +/- 7 deg;
- function:
- articulation between talus & calcaneus allows further rotation of proximal limb to occur over fixed foot because of the unique orientation of the axis of rotation;
- subtalar inversion (w/ associated supination):
- axis of the talonavicular and calcaneo-cuboid joints are not parallel, and motion at this joint is markedly restricted;
- locks the midtarsal joints so that the foot is rigid at push off;
- subtalar eversion (with associated pronation):
- axis of the talonavicular and calcaneo-cuboid joints are parallel & thus motion can occur at midtarsal joint;
- allows maximal motion at the midtarsal joints which allows the foot to absorb energy during heel contact;
- effect of subtalar joint on flat feet
- Physical Exam of Sub Talar Joint
- Radiology of Subtalar Joint
- Subtalar Instability:
- can follow severe inversion ankle sprains;
- cervical ligaments:
- cervical ligaments assist the CFL in promoting lateral subtalar stability;
- the cervical ligament tend to elongate with injury of the CFL;
- not only could this lead to subtalar instability but it could lead to lingering subtalar instability even after the ankle regains its stability (w/ healing of the ATFL);
- references:
- Elongation behavior of calcaneofibular and cervical ligaments during inversion loads applied in an open kinetic chain.
- Ligament Structures in the Tarsal Sinus and Canal.
- stress radiographs including subtalar stress views (Broden 45 deg internal rotation and 20 deg caudal tilt);
- look for loss of parallelism on Broden's view;
- lateral heel wedges, ankle braces to limit inversion, and subtalar bracing are helpful;
- surgery can include Chrisman-Snook procedure, which rebuilds both ATFL and CFL, direct repair of the CFL and tightening of the inferior extensor retinaculum may be helpful;
- references:
- Instability of the subtalar joint: diagnosis by stress tomography in three cases.
- Subtalar Degenerative Disease:
- commonly post traumatic in origin;
- in advanced cases consider selective fusion;
- subtalar fusion for treatment of calcaneal fractures:
- selective arthrodesis of the talocalcaneal joint is indicated w/ post traumatic arthritis, and results in a less rigid foot (does not tie up the remainder of the subtalar joint
Posterior subtalar joint arthrography. A useful tool in the diagnosis of hindfoot disorders.
Biomechanics of the subtalar joint complex.
Comparison of three methods used to obtain a neutral plaster foot impression.