Subtalar arthrodesis is the surgical fusion of the talocalcaneal joint, eliminating motion at this complex articulation between talus and calcaneus that controls foot inversion-eversion. Indications include advanced subtalar osteoarthritis (most commonly post-traumatic after intra-articular calcaneal fracture, with rates up to 30-50% requiring eventual fusion), inflammatory arthritis (rheumatoid, psoriatic), tarsal coalition (talocalcaneal coalition causing rigid flatfoot in adolescents/young adults), severe planovalgus deformity (failed conservative management of stage III-IV adult-acquired flatfoot deformity from posterior tibial tendon dysfunction), Charcot neuroarthropathy with midfoot/hindfoot collapse, peroneal tendon dislocations or tears with secondary subtalar arthritis, and selected hindfoot deformities not amenable to joint-preserving surgery.
Surgical techniques: open in situ subtalar arthrodesis—lateral approach (Ollier or extensile lateral) with sinus tarsi exposure, sural nerve protection, peroneal tendon retraction, joint preparation removing residual cartilage and exposing subchondral bone with curettes/burrs, microfracture/feathering for vascular ingrowth, bone grafting (autograft from iliac crest, calcaneus, or distal tibia; allograft; bone marrow aspirate concentrate for biological augmentation), positioning with hindfoot in slight valgus (3-5 degrees) and neutral plantarflexion, fixation with two parallel or convergent 6.5-7.0 mm cannulated screws (most common), or plate-screw construct, or staples for selected. Distraction bone block subtalar arthrodesis—indicated for calcaneal fracture sequelae with loss of height (talar declination, anterior tibiotalar impingement); inserts large structural bone block (typically iliac crest tricortical autograft or femoral head allograft) restoring calcaneal height. Arthroscopic subtalar arthrodesis—posterior or lateral portal approach, less soft tissue stripping, similar union rates with potentially faster recovery in selected cases.
Postoperative course: non-weight-bearing 6-8 weeks in cast or boot, then progressive weight bearing in boot 6-12 weeks based on radiographic union, transition to shoe and gradual return to activities. Outcomes: union rate 85-95% with rigid fixation and adequate biology; AOFAS hindfoot scores improve from 40-50 preop to 75-85 postop; patient satisfaction 75-85%. Complications: nonunion (5-15%, higher with smoking, diabetes, peripheral vascular disease, Charcot, prior failed surgery), malunion (varus malposition causing lateral overload, valgus malposition), wound complications (especially lateral approach near peroneal tendons), sural nerve injury (numbness/dysesthesia along lateral foot), peroneal tendon injury, hardware prominence requiring removal, deep vein thrombosis, infection, and importantly adjacent joint arthritis (talonavicular, calcaneocuboid—these are commonly arthritic at time of surgery suggesting triple arthrodesis if extensive). Patient counseling: residual hindfoot stiffness affects walking on uneven terrain, reduced shock absorption, may eventually require triple or pantalar fusion if disease progresses; smoking cessation strongly recommended (smoking increases nonunion 4-5x); BMI optimization; bone health assessment (vitamin D, calcium); prediabetes/diabetes optimization.