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Sub-Talar Joint

- See:
      - 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.

Totally absorbable screws in fixation of subtalar extra articular arthrodesis in children with spastic neuromuscular disease: preliminary report of a randomized prospective study of fourteen arthrodeses fixed with absorbable or metallic screws.

Biomechanics of the subtalar joint complex.

Reconstructive osteotomy of the calcaneus with subtalar arthrodesis for malunited calcaneal fractures.

MR imaging of the tarsal sinus and canal: normal anatomy, pathologic findings, and features of the sinus tarsi syndrome.

Comparison of three methods used to obtain a neutral plaster foot impression.