INTRODUCTION AND PATHOANATOMY

Subtalar dislocation, historically referred to as peritalar dislocation, is a rare and severe injury characterized by the simultaneous dislocation of the distal articulations of the talus at both the talocalcaneal and talonavicular joints. The tibiotalar and calcaneocuboid articulations remain anatomically intact. This injury disrupts the complex biomechanical linkage of the hindfoot, often referred to as the coxa pedis or acetabulum pedis.

Subtalar dislocations are broadly classified by the direction of the distal foot relative to the talus:
* Medial Dislocations (80-85%): Typically resulting from forced inversion of a plantarflexed foot. The calcaneus is displaced medially, and the head of the talus becomes prominent dorsolaterally.
* Lateral Dislocations (15-20%): Resulting from forced eversion. The calcaneus is displaced laterally, and the talar head is prominent medially. These are generally higher-energy injuries and carry a higher rate of open fractures and irreducibility.
* Anterior and Posterior Dislocations: Exceedingly rare, usually representing extreme variants of medial or lateral dislocations.

While the majority of subtalar dislocations can be managed with prompt closed reduction under conscious sedation or general anesthesia, approximately 10% to 15% of medial dislocations and up to 20% of lateral dislocations are irreducible by closed means. This irreducibility is almost universally secondary to soft tissue interposition or osteochondral impaction.

💡 Clinical Pearl: Blocks to Reduction

In medial dislocations, the talar head may become buttonholed through the extensor retinaculum, the extensor digitorum brevis (EDB) muscle belly, or the dorsal talonavicular capsule.
In lateral dislocations, the primary block to reduction is the tibialis posterior tendon, which can slip anteriorly and laterally, becoming incarcerated in the talonavicular joint. Less commonly, the flexor hallucis longus (FHL) or flexor digitorum longus (FDL) may block reduction.

INDICATIONS FOR OPEN REDUCTION

The decision to proceed with open reduction is dictated by the failure of closed management or the presence of specific injury characteristics:
1. Irreducible Dislocation: Failure to achieve concentric reduction after two well-executed closed attempts under adequate anesthesia and muscle relaxation.
2. Open Dislocation: Requires emergent operative debridement, irrigation, and open reduction.
3. Non-concentric Reduction: Post-reduction imaging demonstrating widening of the talonavicular or subtalar joints, indicating interposed soft tissue or osteochondral fragments.
4. Associated Unstable Fractures: Concomitant displaced fractures of the talar neck, body, or calcaneus that require internal fixation.

PREOPERATIVE PLANNING AND POSITIONING

Imaging

Standard trauma radiographs (Anteroposterior, Lateral, and Mortise views of the ankle, plus AP, Lateral, and Oblique views of the foot) are mandatory. If a closed reduction is successful but joint congruity is questionable, a fine-cut Computed Tomography (CT) scan is highly recommended to evaluate for osteochondral shear fractures of the talar dome, talar head, or posterior facet of the calcaneus, which occur in up to 45% of cases.

Patient Positioning

• The patient is placed in the supine position on a radiolucent operating table.
• A bump (sandbag or rolled blanket) is placed under the ipsilateral hip to internally rotate the leg, bringing the anterolateral aspect of the foot and ankle into a direct vertical orientation. This is particularly useful for the standard anterolateral approach.
• A well-padded thigh tourniquet is applied to ensure a bloodless surgical field, which is critical for identifying delicate neurovascular structures and incarcerated tendons.
• Prophylactic intravenous antibiotics are administered prior to tourniquet inflation.

SURGICAL ANATOMY AND APPROACHES

The choice of surgical approach is dictated by the direction of the dislocation and the suspected blocking structures.

The Anterolateral Approach

This is the workhorse approach for irreducible medial subtalar dislocations and provides excellent access to the talonavicular and subtalar joints. It allows for the extraction of the extensor retinaculum or EDB muscle from the talonavicular joint.

The Anteromedial Approach

Often required for irreducible lateral subtalar dislocations. Because the tibialis posterior tendon is the most common offending structure, a medial incision allows direct visualization, mobilization, and extraction of the tendon from the talonavicular joint space. In severe lateral dislocations, a combined approach (anterolateral and anteromedial) may be necessary.

STEP-BY-STEP SURGICAL TECHNIQUE: OPEN REDUCTION

1. Incision and Superficial Dissection

For the standard anterolateral approach:
* Make a longitudinal anterolateral incision approximately 7.5 cm long.
* The incision should begin just proximal to the ankle joint line, centered between the tibia and fibula, and extend distally toward the cuboid.
* Neurovascular Protection: Carefully dissect through the subcutaneous tissues. You must meticulously identify and protect the medial and lateral dorsal cutaneous branches of the superficial peroneal nerve. Retract these nerve branches gently using vessel loops to prevent traction neuropraxia, which can lead to debilitating postoperative neuromas.

2. Deep Dissection and Retraction

• Identify the extensor retinaculum and incise it in line with the skin incision.
• Identify the extensor tendons. Retract the extensor digitorum longus (EDL) and extensor hallucis longus (EHL) tendons medially.
• Retract the peroneus tertius tendon laterally.
• This retraction window exposes the underlying dorsal capsule of the talonavicular joint, the neck of the talus, and the anterior aspect of the subtalar (talocalcaneal) joint.

3. Capsulotomy and Joint Exposure

• Incise the capsule longitudinally over the head and neck of the talus.
• Extend the capsular incision distally into the midtarsus to fully expose the talonavicular articulation.
• Clear any hematoma, debris, or osteochondral fragments from the joint spaces. Inspect the talar head for impaction fractures.

4. The Reduction Maneuver

Reduction requires a coordinated effort between the primary surgeon and an assistant, combining mechanical leverage with specific multi-planar traction.

• Instrument Placement: Insert a smooth bone skid or a broad periosteal elevator into the subtalar joint. This instrument will act as a fulcrum to lever the calcaneus and navicular back into their anatomic positions beneath and distal to the talus.
• Leverage and Traction: Apply longitudinal traction to the forefoot and hindfoot to distract the impacted joints.

🚨 Surgical Warning: Directional Reduction Mechanics

The assistant's role is critical and must be tailored to the direction of the dislocation:
* For a Medial Dislocation: The assistant must simultaneously abduct and evert the foot while the surgeon applies leverage with the bone skid.
* For a Lateral Dislocation: The assistant must simultaneously adduct and invert the foot.

5. Managing the Incarcerated Tibialis Posterior Tendon (Lateral Dislocations)

In a lateral dislocation, the posterior tibial tendon frequently blocks reduction. It slips anteriorly and becomes tightly wedged between the talar head and the navicular.
* The tendon must be physically lifted out of the talonavicular joint before reduction is possible.
* If the tendon cannot be accessed from the anterolateral approach, or if the injury is an open lateral dislocation with a medial wound, you must extend the medial wound or create a separate anteromedial incision.
* Through this medial access, carefully lift the dorsal neurovascular bundle and the offending tibialis posterior tendon.
* Incise the dorsal capsule of the talonavicular joint. With this structure loosened and the tendon retracted, the navicular may be levered around the head of the talus using a periosteal elevator.

6. Assessment of Stability and Temporary Fixation

Once concentric reduction is achieved, assess the stability of the subtalar and talonavicular joints through a gentle range of motion.
* If the joints are stable, no internal fixation is required.
* If the joints are highly unstable (often due to severe capsuloligamentous tearing or concomitant fractures), temporary stabilization is mandatory to prevent early re-dislocation.
* Pinning Technique: Hold the reduction and insert longitudinally placed, stout Steinmann pins (typically 2.0 mm to 2.8 mm) across the calcaneocuboid and talonavicular joints. Ensure the pins do not cross the tibiotalar joint unless absolutely necessary.
* External Fixation: In cases of severe soft tissue compromise, massive swelling, or polytrauma, a spanning delta-frame external fixator may be utilized instead of, or in addition to, Steinmann pins.
* Pins or external fixators are typically left in place for 4 to 6 weeks.

7. Closure

• Irrigate the wounds copiously with sterile saline.
• Repair the joint capsules if the tissue quality permits, though watertight closure is rarely possible or necessary.
• Allow the extensor retinaculum to fall back into place; loose approximation is acceptable.
• Close the subcutaneous tissue and skin meticulously. Avoid excessive tension on the skin edges to prevent necrosis.

POSTOPERATIVE CARE AND REHABILITATION

The postoperative protocol must balance the need for ligamentous healing with the prevention of debilitating hindfoot stiffness.

Phase I: Immediate Postoperative Period (Weeks 0-6)

• Immobilization: A well-padded cast is applied from the base of the toes to the tibial tuberosity over a bulky compression dressing.
• Swelling Management: The cast must be bivalved immediately in the operating room or recovery area to accommodate anticipated postoperative swelling and prevent compartment syndrome of the foot.
• Positioning: The limb is strictly elevated above heart level for the first 48 to 72 hours.
• Early Motion: Active exercises of the metatarsophalangeal (MTP) joints are encouraged immediately to promote tendon gliding and reduce edema.
• Weight-Bearing: The patient is strictly non-weight-bearing on the operative extremity.

Phase II: Transition and Early Mobilization (Week 6)

• At 6 weeks postoperatively, clinical and radiographic evaluations are performed. If Steinmann pins were utilized, they are removed in the clinic.
• Cast Discontinuation: Cast immobilization is discontinued.
• Orthotic Support: A lace-up foot and ankle leather corset (or a rigid functional walker boot) is applied. This corset is worn for 1 month to control residual edema and provide proprioceptive support.
• Physical Therapy: Aggressive, active range of motion exercises are initiated. Patients are encouraged to perform active inversion, eversion, dorsiflexion, and plantar flexion of the foot and ankle.
• Weight-Bearing: Weight bearing to tolerance with the assistance of crutches is allowed.

Phase III: Maturation and Strengthening (Weeks 8 and Beyond)

• Full weight bearing should be comfortable by 6 to 8 weeks after the injury.
• The lace-up corset can be weaned as the patient's dynamic stability improves.
• Gait training, proprioceptive exercises (e.g., balance board), and peroneal strengthening are emphasized.

🗣️ Patient Counseling and Expectations

Patients must be explicitly advised during the preoperative and postoperative phases that the foot and ankle will likely swell for several months. Furthermore, the midfoot and hindfoot will feel stiff. Permanent loss of some subtalar inversion and eversion (up to 30-50% compared to the contralateral side) is a common and expected outcome, even with a perfectly executed open reduction.

COMPLICATIONS AND MANAGEMENT

1. Post-Traumatic Subtalar Arthritis: The most common long-term complication, occurring in up to 50% of patients, particularly those with associated osteochondral shear fractures. Management begins with NSAIDs, custom orthotics, and activity modification. Refractory cases may require a subtalar arthrodesis.
2. Avascular Necrosis (AVN) of the Talus: While less common than in talar neck fractures, AVN can occur due to the disruption of the artery of the tarsal canal and deltoid branches during the dislocation. Rates are higher in lateral dislocations and open injuries. Serial radiographs should monitor for Hawkins' sign (subchondral radiolucency indicating revascularization) at 6 to 8 weeks.
3. Hindfoot Stiffness: Universal to some degree. Aggressive early physical therapy at the 6-week mark is the best preventative measure.
4. Infection and Wound Breakdown: High-energy injuries with severe soft tissue compromise are at risk. Meticulous handling of the soft tissues, avoidance of tension during closure, and appropriate use of bivalved casts are critical preventative steps.
5. Neuroma Formation: Injury to the superficial peroneal nerve branches during the anterolateral approach can cause severe neuropathic pain. Careful identification and gentle retraction are paramount.

CONCLUSION

Open reduction of a subtalar dislocation is a critical procedure in the orthopedic trauma repertoire. Success relies on a profound understanding of peritalar pathoanatomy, the precise identification of the soft tissue structures blocking reduction, and the execution of a coordinated, atraumatic reduction maneuver. By adhering to strict anatomical dissection, ensuring concentric joint reduction, and following a structured postoperative rehabilitation protocol, surgeons can optimize functional outcomes and minimize the inherent risks of post-traumatic arthritis and hindfoot stiffness.

📚 Medical References

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