Subtalar Dislocations

A subtalar dislocation is the simultaneous dislocation of the talonavicular and talocalcaneal joints with the tibiotalar joint left intact. It is also called a peritalar dislocation, because the dislocation occurs around the talus, which stays in the ankle mortise. The injury is rare but dramatic, and it needs urgent reduction to prevent skin necrosis and long-term complications.

How common. Subtalar dislocation is quoted at approximately 1% of all dislocations and 1-2% of major joint dislocations; the Prada-Cañizares review gives 1% of traumatic foot injuries and 1-2% of all dislocations. Most patients are young men (70-80% male), most often aged 20-40, and the injury is associated with an active lifestyle and sport; it is rare in children and the elderly.

Mechanism. The energy is usually high:

• Motor vehicle accidents (40%)
• Falls from height (30%)
• Sports injuries (20%), such as basketball and football
• Direct trauma (10%)

The joints. Two joints dislocate together: the talonavicular joint, a ball and socket, and the talocalcaneal joint, the subtalar joint proper. The tibiotalar joint is not involved, and the talus stays in the mortise while the foot dislocates beneath it.

The blood supply. The talus is supplied by:

• Posterior tibial artery - the main supply, through the artery of the tarsal canal
• Anterior tibial artery - the talar neck and head, dorsally
• Peroneal artery - through the artery of the tarsal sinus

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Why it matters. About 60% of the talus is covered by articular cartilage, which carries no periosteal vessels, and the bone has no muscle attachments. It therefore depends on a tenuous, retrograde intraosseous supply through the tarsal canal and sinus. A prolonged dislocation stretches and can compromise those vessels, which significantly increases the risk of AVN, especially when reduction is delayed.

The blocks to reduction. The block sits on the side opposite the direction of displacement, because that side is stretched taut across the prominent talar head. Get this right and the operative approach follows: approach the side of the block, not the side of the deformity. Get it wrong and you open the wrong side of the foot.

A medial dislocation leaves the talar head prominent dorsolaterally, so it is blocked by dorsolateral structures:

• The talar head buttonholes through the extensor digitorum brevis (EDB) - the classic and best-described block
• The talar head is entrapped in the extensor retinaculum
• Talonavicular capsule and ligament interposition, and talonavicular impaction
• The peroneal tendons may wrap around the talar neck

A lateral dislocation leaves the talar head prominent medially, so it is blocked by medial structures:

• The posterior tibial tendon - the characteristic block, and the reason a lateral dislocation more often needs open reduction
• Flexor hallucis longus and flexor digitorum longus may also obstruct
• Talonavicular capsule interposition

The posterior tibial tendon is therefore not the block in a medial dislocation, and the peroneal tendons and extensor retinaculum are not the block in a lateral one: each obstructs the foot displaced away from it.

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Subtalar dislocations are named by the direction the foot goes relative to the talus: medial, lateral, anterior or posterior. The classic figures are 85% medial and 15% lateral; pooled modern reviews put the medial share nearer 68-72%.

Medial dislocation. A high-energy inversion force drives the foot into plantarflexion and inversion, in falls, motor vehicle accidents and sport (basketball, hence "basketball foot"), and the calcaneus, navicular and forefoot displace medially under the talus. The talar head is palpable and visible dorsolaterally, with the skin tense over it. Medial is the most common type, has the better prognosis, a lower complication rate and is easier to reduce.

Lateral dislocation. The less common type. A high-energy eversion force drives the foot into dorsiflexion and eversion, and it usually requires greater force than a medial dislocation. The talar head is prominent dorsomedially with the skin tense medially. Open injuries and fractures are more often associated, the complication rate (AVN, arthritis) is higher, and the outcomes are significantly worse.

Anterior and posterior dislocations. Both are very rare and less well described in the literature.

• Anterior - forced dorsiflexion or a direct anterior force on the heel displaces the foot anteriorly relative to the talus, the forefoot forward. Reduce with longitudinal traction, plantarflex to disengage, then reduce.
• Posterior - forced plantarflexion or a direct posterior force displaces the foot posteriorly, the forefoot backward. Reduce with longitudinal traction, dorsiflex to disengage, then reduce.

Pure dislocation or fracture-dislocation. A pure dislocation, without associated fracture, has the better prognosis, lower complication rates and follows the standard closed reduction protocol. Associated fractures are found in about 60% in pooled series, and they change the prognosis significantly, with higher AVN and post-traumatic arthritis rates. The sites:

• Talar dome and neck (most common)
• Talar body
• Posterior process of the talus
• Sustentaculum tali
• Anterior process of the calcaneus
• Navicular
• Cuboid
• Medial or lateral malleolus

Open or closed. Open injuries are more common with lateral dislocations, need urgent surgical debridement and carry a significantly worse prognosis.

The deformity. The deformity is obvious, with significant swelling and severe pain, and the patient is unable to bear weight. In a medial dislocation the foot is adducted and inverted with the heel in varus; in a lateral dislocation it is abducted and everted with the heel in valgus. Look at the skin over the talar head, which may be tented, and check carefully for open wounds, including between the toes.

Neurovascular examination. Examine and document before reduction, then again after it, recording any change in vascular status, any sensory change, and motor function once pain is controlled:

• Dorsalis pedis pulse (may be displaced)
• Posterior tibial pulse
• Capillary refill
• Sensation, if the patient can cooperate: superficial peroneal (dorsum of foot), deep peroneal (first web space), tibial (plantar foot) and sural (lateral foot)

Associated injuries. Locally, look for associated fractures (malleoli, talus, calcaneus, navicular, cuboid) and check the integrity of the ankle mortise. The mechanism is high energy, so assess for polytrauma: spine injuries, other extremity injuries and head injury.

Differential diagnosis. The deformed, swollen hindfoot has several mimics. The single most discriminating step is establishing whether the tibiotalar (ankle) mortise is intact and which articulations have lost congruity.

Before reduction. Plain radiographs confirm the diagnosis and the direction:

• AP foot
• Lateral foot
• AP ankle
• Lateral ankle

Read them for four things: the talonavicular and talocalcaneal joints disrupted, the tibiotalar joint intact, any obvious fracture, and the direction of dislocation. Do not delay reduction for perfect films: if the skin is compromised, reduce emergently on the clinical findings and whatever imaging is immediately available.

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After reduction. Radiographs confirm a congruent reduction of the talonavicular and talocalcaneal joints, check the alignment of the ankle mortise, and show any fracture now visible.

CT is mandatory after every reduction. Associated injuries are found in the great majority: the pooled osseous injury rate is about 60%, and in the Bibbo series CT found additional injuries missed on plain films in all 9 cases and changed management in 44%. Many of these injuries are occult on plain radiographs, and a large fragment may change management. CT is usually performed within 24-48 hours of reduction and looks for:

• Talar dome and neck fractures
• Posterior process fractures
• Calcaneal fractures (sustentaculum, anterior process)
• Navicular and cuboid fractures
• Loose bodies
• Congruency of the reduction

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MRI is rarely indicated acutely and is usually a delayed investigation. Its potential indications:

• Suspected chondral injury
• Soft tissue interposition preventing reduction
• Late presentation with concern for AVN

Algorithm

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In the emergency department. Examine and document the neurovascular status, assess the skin and look for open wounds, and control the pain. Skin tension is the primary driver of urgency. Set up with the patient supine under procedural sedation or regional anaesthesia, with an assistant for counter-traction; fluoroscopy is helpful but not mandatory.

Closed reduction. The principles are the same for every direction:

1. Flex the knee to relax the gastrocnemius
2. Apply longitudinal traction
3. Accentuate the deformity first, which unlocks the dislocation
4. Reverse the deformity to reduce

For a medial dislocation, momentarily increase plantarflexion and inversion, then, maintaining traction, evert and dorsiflex the foot; direct dorsal pressure on the talar head may assist. For a lateral dislocation, momentarily increase eversion, then, maintaining traction, invert the foot, with direct pressure on the talar head. An audible or palpable "clunk" usually accompanies successful reduction.

Closed reduction succeeds in 80-90%, more often for medial than lateral dislocations, and needs adequate sedation or muscle relaxation. Afterwards, confirm the reduction on radiographs, apply a below-knee backslab, reassess the neurovascular status and schedule the CT.

When it will not reduce. Closed reduction fails because of:

• Soft tissue interposition (tendons, capsule), the cause of most failures
• A buttonholed extensor retinaculum
• Associated fracture fragments blocking reduction
• Inadequate analgesia or muscle relaxation

Consider general anaesthesia with complete muscle relaxation and try again; if that fails, proceed to open reduction, which is required in 10-20% of cases. A medial dislocation is approached anterolaterally, which gives direct access to release the buttonholed talar head; a lateral dislocation is approached anteromedially, and may need dual incisions (see Surgical Technique).

Associated fractures. Fragment size decides management. Small fragments (under 25% of the joint surface) usually do not affect stability and are managed conservatively with serial radiographs; they may be excised if a loose body causes symptoms. Large fragments (over 25%) are considered for ORIF, particularly if they affect joint congruency or stability.

• Talar neck and body fractures often require ORIF, with screws from anterior to posterior, following Hawkins classification principles; the AVN risk is higher
• Malleolar fractures are fixed if the ankle mortise is unstable, by standard ORIF techniques
• Calcaneal fractures of the sustentaculum or anterior process are usually treated conservatively unless large
• Navicular and cuboid fractures may need fixation if large; small fragments are often treated conservatively

Is the reduction stable? After any reduction, closed or open, confirm a concentric reduction of both the talonavicular and talocalcaneal joints on fluoroscopy, then stress the hindfoot under the image intensifier through the arc that produced the injury (inversion and eversion, dorsiflexion and plantarflexion). A pure dislocation that reduces with a clear clunk is usually intrinsically stable once the capsuloligamentous sleeve is back in place, and a simple below-knee cast or backslab suffices.

Instability that warrants supplementary fixation is the exception, and it clusters in predictable settings:

• Associated fractures that remain displaced or leave a joint incongruent after reduction (such as talar neck, large talar head or navicular fragments); fix the fracture and the dislocation usually becomes stable
• Re-dislocation or gross subluxation on stress despite a concentric reduction
• Open reduction that has extensively disrupted the stabilising capsule, retinaculum and ligaments, or an open injury with severe soft-tissue loss

When it is unstable, use temporary percutaneous K-wire transfixion across the unstable joint (talonavicular, subtalar or both), removed at about 4 to 6 weeks before the subtalar joint is mobilised. A spanning external fixator suits the grossly unstable, highly comminuted, soft-tissue-compromised or open injury, and allows wound access. Do not prolong immobilisation unnecessarily: the original DeLee and Curtis teaching is that prolonged casting worsens subtalar stiffness, so remove temporary fixation and begin motion as soon as stability allows.

Skin necrosis. The most urgent acute complication. It follows a prolonged dislocation with the skin tented over the talar head, can develop within 6-12 hours, may progress to full-thickness loss and can convert a closed injury to an open one. Urgent reduction prevents it.

Neurovascular injury. Seen in 5-10% of cases. The nerve injuries are usually neurapraxia from stretch and most recover with time:

• Superficial peroneal nerve (most common)
• Deep peroneal nerve
• Tibial nerve

Injury to the dorsalis pedis or posterior tibial artery is rare.

Compartment syndrome. Very rare but possible, after high-energy injuries, with associated fractures or after a prolonged dislocation. Keep a high index of suspicion and monitor closely for the first 48 hours.

Post-traumatic arthritis. The most common long-term complication. Its incidence by injury type:

• Pure closed medial dislocation: 30-40%
• Fracture-dislocation: 50-70%
• Open or lateral dislocation: 60-80%

It may take 5-10 years to develop, with progressive symptoms, subtalar crepitus and pain, and joint space narrowing on radiographs. Treat it with activity modification, orthotics and supportive footwear, NSAIDs and corticosteroid injections, and subtalar fusion if severe. Fusion gives reliable pain relief at the cost of further loss of inversion and eversion, which is often well tolerated.

Avascular necrosis. Its incidence by injury type:

• Pure dislocation: 5-10%
• Fracture-dislocation: 15-20%
• Open injury, and lateral or open dislocations: 20-30%

The risk is higher with delayed reduction (over 6 hours), a high-energy mechanism, an associated talar neck fracture, an open injury and the need for open reduction. AVN is initially asymptomatic; pain develops as collapse occurs, followed by progressive deformity and eventually arthritis, and the peak incidence is 12-24 months after injury. Look for the Hawkins sign at 6-8 weeks: subchondral lucency means a good blood supply, and its absence may indicate AVN. MRI, requested if clinical suspicion is high, is the most sensitive test for early detection; radiographic sclerosis and collapse come later. Protected weight bearing is used if AVN is detected early; core decompression is rarely beneficial, and symptomatic AVN usually progresses to fusion, which may need to be talonavicular or triple.

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Subtalar stiffness. Universal to some degree. Normal subtalar motion is 20-30 degrees of inversion and 10-20 degrees of eversion, and a 50-70% loss is typical after this injury, inversion more than eversion. The ankle and midfoot often compensate well, and the stiffness may protect against arthritis pain. Walking on flat ground is usually normal; uneven terrain, slopes, inclines and stairs are harder, and some patients need orthotic support. Treat with aggressive physiotherapy for range of motion, orthotic devices and, if severe, an ankle-foot orthosis; most patients adapt well.

Chronic pain. Its incidence is quoted at 10-40% depending on injury severity, although the lateral or open group in Outcomes reaches 40-60%. Its sources are post-traumatic arthritis, subtalar stiffness, nerve injury (neuroma, dysaesthesia) and, rarely, complex regional pain syndrome. Treat it with multimodal pain management, physiotherapy, psychological support and orthotics, and surgery if there is a structural cause.

Malunion and nonunion of associated fractures. A talar malunion alters hindfoot alignment and accelerates arthritis, and may need osteotomy or fusion. Nonunion is rare with adequate immobilisation, may occur with talar neck fractures, and usually requires surgical fixation.

Prevention. Early reduction is the single most important factor, with a target of reduction within 6 hours: it reduces the risk of skin necrosis and AVN and improves overall outcomes. Post-reduction CT allows appropriate fixation, prevents displacement during healing and improves long-term outcomes. Adequate immobilisation, typically for 4-6 weeks, prevents redislocation; non-weight bearing is essential, followed by progressive loading with serial radiographs. Aggressive rehabilitation afterwards (range of motion, strengthening, proprioception and a return-to-activity programme) optimises function.

The same protocol follows closed and open reduction, with the additions below for an open reduction.

Weeks 0-2. A below-knee backslab or cast, strictly non-weight bearing on crutches or a knee scooter, with elevation, ice and DVT prophylaxis (rivaroxaban or enoxaparin). Monitor for compartment syndrome over the first 48 hours.

Weeks 2-6. Change to a CAM boot or short leg cast and stay non-weight bearing. Begin ankle range of motion, gentle active dorsiflexion and plantarflexion, if the tibiotalar joint is stable, but do not invert or evert: the subtalar joint is healing.

Weeks 6-8. Radiographs confirm healing. Begin partial weight bearing (25-50%) in the CAM boot, increasing as pain allows, continue ankle motion and begin gentle subtalar motion.

Weeks 8-12. Progress to full weight bearing and wean from the boot to a supportive shoe, with physiotherapy two to three times a week for proprioception, balance and strengthening.

Months 3-6. Full weight bearing in regular shoes, progressive strengthening, balance and proprioception work, and sport-specific training where it applies. From months 4-6 the patient returns to full activity and to sport as its impact allows (see Outcomes); persistent subtalar stiffness is possible, and signs of post-traumatic arthritis are watched for.

After open reduction. Add neurovascular checks every 2 hours for 24 hours, a wound check at 2 weeks and suture removal at 2-3 weeks, with the CAM boot at 2-3 weeks. Non-weight bearing typically lasts 6 weeks, and full weight bearing is reached by 8-10 weeks, with gait retraining added to the rehabilitation. The complication risk is higher than after closed reduction, so watch closely for infection, AVN and arthritis; rehabilitation may be prolonged and the immobilisation period may be slightly longer.

How long to immobilise. DeLee and Curtis found that immobilisation beyond three weeks produced poor results, several series report good results with shorter immobilisation and early subtalar motion, and the optimal duration is not well defined (see Evidence Base and Practice Variation).

Follow-up. Radiographs after reduction, at 2 weeks and at 6 weeks; clinic review at 6 weeks, 12 weeks, 6 months and 12 months, then as needed if symptomatic. At each visit assess pain, range of motion (subtalar inversion and eversion above all), gait, return to work or sport, and radiographic change of arthritis or AVN. For arthritis, take serial radiographs if symptomatic, and consider subtalar fusion if symptomatic arthritis develops.

Prognostic factors. The factors below separate better from worse outcomes.

Outcomes by injury type. The subgroup percentages below are conventional estimates from the case-series literature, not measurements from a single cohort. The pooled all-comer anchor is Hoexum 2014 (528 cases: 52.3% good, 25.2% fair, 22.5% poor), with open injury and associated fracture driving the poor results. Arthritis and AVN rates by group are given under Complications.

Salvage is by subtalar fusion (most common), triple arthrodesis, or below-knee amputation in severe cases.

Return to work and sport. After a pure closed medial dislocation most return to work, sedentary work at 2-3 months and manual labour at 4-6 months, and many return to sport, which may be delayed; contact sport takes 6-9 months, and full subtalar motion may never return. Across injuries, the typical return to sport is:

• Low impact (walking, cycling): 3-4 months
• Moderate impact (running): 6-9 months
• High impact (basketball, football): 9-12 months
• Elite athletes may not return to their pre-injury level

Global Epidemiology

Subtalar dislocation is rare worldwide, accounting for approximately 1% of all traumatic foot injuries and 1-2% of all dislocations, almost always from high-energy trauma (Prada-Cañizares et al, 2016). Pooled data from large systematic reviews give a consistent demographic and directional profile:

Guidelines and Society Guidance

No high-level (Level I/II) guideline or randomised evidence exists for this rare injury - management rests on consistent narrative/systematic reviews and expert consensus. The table summarises how the major bodies frame hindfoot trauma principles relevant to subtalar dislocation.

Registry Evidence

There is no dedicated joint registry for subtalar dislocation; national arthroplasty registries (AOANJRR, NJR, AJRR) do not capture this injury. Where late post-traumatic subtalar arthritis proceeds to subtalar or triple arthrodesis, those fusion procedures are captured only indirectly in some national trauma/procedure datasets, and outcome evidence remains limited to single-centre series.

Practice Variation

Reported management varies chiefly in three areas with no consensus standard (Byrd et al, 2013): adjunctive percutaneous K-wire fixation (used selectively for residual instability vs not at all), immobilisation type (below-knee cast vs CAM boot), and duration of immobilisation (under 4 weeks vs around 6 weeks). Several series report good results with shorter immobilisation and early subtalar range of motion, consistent with DeLee and Curtis's original recommendation against prolonged casting.

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