Triple Arthodesis

Biomechanics

 

Able to achieve relatively high level of function after STJ fusion

- previously believed that isolated STJ fusion should not be performed

- believed that triple arthrodesis was operation of choice for hindfoot

- STJ fusion has superior result with less stress on AJ

 

Average loss of DF 30% / PF 10%

 

Position of hindfoot determines flexibility of transverse tarsal (CCJ & TNJ) joints

- imperative that fusion be positioned in ~ 5o valgus 

- permits TTJ mobility

- if varus TTJ locked & patient tends to walk on lateral aspect of foot 

 

Indications for STJ arthrodesis

 

 Subtalar Arthritis

 

Post traumatic / calcaneal fracture

 

RA

 

Primary OA

 

Coalition

 

Talar Coalition CN 1Calcaneonavicular coalition subtalar OA MRI

 

Tibialis posterior dysfunction

 

Neuromuscular disorders

- instability

- CMT / polio / nerve injury

 

Indication for Triple Arthrodesis

 

Valgus deformity

OA of CCJ / TNJ

 

Triple Arthrodesis

 

Technique STJ Fusion

 

Subtalar ArthrodesisSubtalar Arthrodesis 2

 

Approach

 

Position

- patient supine

- roll under hip to expose lateral aspect foot

- tourniquet, IV Abx, radiolucent table, II available

 

Incision 

 

1. Tip of fibula toward base of 4th MT (Ollier's)

- internervous plane between SPN and sural nerve

 

2.  Lateral longitudinal

- required if large correction required

- i.e. post calcaneal fracture

- must insert bone graft and might not be able to close wound

 

Superficial dissection

- peroneal tendons lifted dorsally

- elevate EBD

- fatty tissue over sinus tarsi

- expose STJ / CCJ / sinus tarsi

 

Deep dissection

- remove TC interosseous ligament

- clear out sinus tarsi

- diathermy artery of tarsal sinus

- insert lamina spreader to expose posterior facet

- need to expose medial facet medially

 

Debridement

- curette / osteotomes / burr

- simply remove cartilage if no deformity

- otherwise remove bone to correct deformity

- recreate 2 flat surfaces that come together in 5o valgus

- drill holes to stimulate bleeding +/- bone graft

- if previous calcaneal fracture lateral wall needs to be decompressed 

 

Reduction technique in valgus foot

 

Deformity

- talus internally rotated on calcaneum

- navicular abducted on talus

 

Issues

- need T Achilles lengthening

- need to perform TNJ and CCJ fusion

- likely need to have open reduced TNJ / CCJ before STJ reduction

- may need lateral bone block

- often deficient skin laterally

 

STJ

- reducing calcaneum back under talus difficult

- calcaneum also abducted like navicular

- lamina spreader between lateral process talus and anterior aspect of calcaneum

- open it up

- calcaneum internally rotates / talus externally rotates

- screw like motion

- need to have all joints opened and exposed for this to occur

- need care to ensure don't place foot into varus

 

Fixation

 

Insert K wires for 6.5 mm cannulated screw

 

A.  From talar neck (medial) down into calcaneum

 

B.  Two from inferior calcaneum via stab incisions into body and neck of talus

 

Check position of K wires on II before screw insertion

 

Bone graft

- best to do so

- take from proximal lateral tibia near Gerdy's tubercle 

 

TNJ fusion

 

Arthrodesis CCJ TNJ

 

Indications

- isolated TNJ OA (lose 80% subtalar joint motion)

- as part of triple arthrodesis

 

Midfoot Approach

 

Incision

- medial to T anterior, anterior to T posterior

- talar neck to naviculo-cuneiform joint

- protect saphenous nerve and vein

- Tibialis posterior guide to navicular

 

Exposure

- can sometimes only expose 2/3 of joint medially

- may need to utilize the lateral approach for full exposure

- inserting lamina spreader aids exposure to debride

- reduce forefoot onto navicular by adducting /plantar flexing and pronating it

- must not leave in varus

- provisionally fix with K wires

 

Fixation

- 2 x 4.0 mm cannulated screws

- from navicular into talus

- in parallel

- may need to make notch in medial cuneiform 

 

CCJ fusion

 

Incision

- continue normal incision anteriorly

- expose anterior process of calcaneum

- expose CCJ

 

Fixation

- 2 x screws

- must hug lateral border

- alternatively can use specific plates

 

T Achilles lengthening

 

Indication

- tight T Achilles

- if don't will have to take a lot of bone to get foot plantigrade

 

Technique

A.  Formal Z lengthen

B.  Hoke lengthening

- want to lengthen laterally more than medially

- 2 incisions halfway laterally

- 1 half incision medially between them

- stretch out the T Achilles