Subtalar Arthroscopy Masterclass: Comprehensive Approach to Hindfoot Pathology

Welcome, fellows, to the operating theater. Today, we're delving into the intricacies of subtalar arthroscopy – a powerful diagnostic and therapeutic tool for addressing a spectrum of hindfoot pathologies. This procedure demands meticulous anatomical understanding and precise technique, and we'll walk through it step-by-step, as if you're scrubbed in right beside me.

The Subtalar Joint: A Functional Overview

The subtalar joint, or talocalcaneal joint, is a critical component of lower extremity biomechanics, primarily responsible for the complex motions of inversion and eversion of the foot. It's a synovial joint, characterized by a posterior capsular pouch and small lateral, medial, and anterior recesses. Functionally, it's divided into two distinct articulations:

1. Anterior Articulation (Talocalcaneonavicular): This is a complex joint involving the talus, calcaneus, and navicular.
2. Posterior Articulation (Talocalcaneal): This is the focus of most arthroscopic interventions.

These two articulations are separated by the tarsal canal, which has a prominent lateral opening known as the sinus tarsi.

Within the confines of the tarsal canal and sinus tarsi, we find a dense network of soft tissue structures:
* The interosseous talocalcaneal ligament, a robust stabilizer.
* The medial and intermediate roots of the inferior extensor retinaculum.
* The cervical ligament, another key stabilizer.
* Adipose tissue and a rich vascular supply.

The lateral ligamentous support of the subtalar joint is also crucial to understand. It comprises:
* The lateral talocalcaneal ligament.
* The posterior talocalcaneal ligament.
* The lateral root of the inferior extensor retinaculum.
* The calcaneofibular ligament, part of the lateral ankle complex but with subtalar relevance.

Understanding these relationships is paramount to safe and effective arthroscopy.

Indications and Contraindications for Subtalar Arthroscopy

Subtalar arthroscopy serves both diagnostic and therapeutic purposes.

Common Indications:

• Chronic pain in the sinus tarsi: Often historically termed "sinus tarsi syndrome," though we now aim for a more specific diagnosis given its multifactorial etiology (e.g., interosseous ligament tears, arthrofibrosis, joint degeneration).
• Chondromalacia: Articular cartilage damage.
• Subtalar impingement lesions: Often related to soft tissue scarring or osteophytes.
• Lysis of adhesions: Addressing post-traumatic arthrofibrosis.
• Synovectomy: Removal of inflamed synovial tissue.
• Removal of loose bodies.
• Instability: Diagnostic and potentially therapeutic stabilization.
• Débridement and treatment of osteochondral lesions.
• Retrograde drilling of cystic lesions.
• Evaluation of coalition: Fibrous or cartilaginous connections.
• Removal of a symptomatic os trigonum.
• Evaluation and excision of fractures: Specifically, fractures of the anterior process of the calcaneus and the lateral process of the talus.
• Subtalar fusion: Arthroscopically assisted fusion for advanced arthritis.

Absolute Contraindications:

• Localized infection: A septic joint is an absolute contraindication, as arthroscopy risks spreading the infection.
• Advanced degenerative joint disease with significant deformity: In these cases, arthroscopy offers limited benefit, and open procedures or fusion may be more appropriate.

Relative Contraindications:

• Severe edema: Can obscure landmarks and increase surgical difficulty.
• Poor skin quality: Increases risk of wound complications and infection.
• Poor vascular status: Impairs healing and increases complication risk.

Preoperative Planning: Laying the Groundwork for Success

Effective preoperative planning is the cornerstone of any successful surgical intervention.

Patient History and Physical Findings:

Patients typically present with chronic lateral hindfoot pain, aggravated by standing, walking, and especially uneven terrain. They may describe a feeling of instability. On examination, we often find:
* Pain on firm pressure over the lateral opening of the sinus tarsi.
* Subtalar stiffness and pain, indicating pathology within or around the joint.
* Restricted motion, though subtalar motion (inversion/eversion) is complex and difficult to measure precisely. We test it by stabilizing the heel and moving the forefoot. This motion should be smooth and painless.
* Relief of symptoms with a diagnostic injection of local anesthetic into the sinus tarsi strongly supports the diagnosis.

Imaging and Diagnostic Studies:

• Standard Radiographs:
  • Anteroposterior (AP), lateral, and modified AP views of the foot: Essential to visualize the general joint architecture.
  • Hindfoot oblique views: Best for visualizing the lateral and posterior processes of the talus.
  • Oblique 45-degree foot films: Offer a good view of the anterior subtalar joint.
  • Borden’s view: Crucial for the posterior facet of the subtalar joint. This is obtained by rotating the foot medially 45 degrees with dorsiflexion, directing the x-ray beam at the lateral malleolus, angled 10 to 40 degrees cephalad.
• Computed Tomography (CT) Scans:
  • Coronal plane: Best for visualizing the talar body, posterior, and lateral processes of the talus, and the calcaneus.
  • Transverse or sagittal planes: Excellent for the talar neck and dome, and for showing intra-articular pathology like osteophytes or coalitions.
• Magnetic Resonance Imaging (MRI):
  • Detects chronic inflammation, fibrosis, ligamentous injury (e.g., interosseous ligament tears), bone contusions, osteochondral lesions, chondral injury, impingement, synovitis, and fibrous or cartilaginous coalitions.
  • While MRI is powerful, remember that arthroscopy often provides a more accurate assessment of cartilage damage than preoperative imaging.
• Differential Injections: Crucial to confirm the source of pain, especially to differentiate subtalar pathology from ankle pathology or other causes of chronic lateral ankle pain (e.g., peroneal tendon pathology, posterior tibial tendon dysfunction, superficial peroneal nerve pathology, various fractures, calcaneocuboid arthrosis).

Nonoperative Management:

Before considering surgery, a trial of nonoperative management is often warranted:
* Injection of anesthetic or corticosteroid.
* Foot orthoses, such as a UCBL.
* Anti-inflammatory medication.
* Ankle brace with a hindfoot lock.
* Peroneal tendon strengthening exercises.

Patient Positioning and Anesthesia

Anesthesia:

We have several options for anesthesia, including local, regional (spinal or epidural), or general anesthesia. The choice depends on patient comorbidities, surgeon preference, and the anticipated duration of the procedure. For subtalar arthroscopy, I typically prefer general anesthesia combined with a regional block for postoperative pain control.

Positioning:

Today, for our standard lateral approach to posterior subtalar arthroscopy, we'll place the patient in the lateral decubitus position.

1. Lateral Decubitus Setup:
   • The patient is positioned on their side with the operative extremity draped free.
   • Ensure adequate padding between the lower extremities to prevent pressure points.
   • Crucially, place padding under the contralateral extremity, particularly around the fibular head, to protect the peroneal nerve from compression.
   • The operative limb should be positioned to allow full range of motion of the ankle and subtalar joint.
   • A thigh tourniquet is recommended. We'll inflate it once the patient is prepped and draped to ensure a bloodless field, which is critical for clear arthroscopic visualization.

Surgical Warning: Always double-check padding and limb position. Nerve palsies, particularly peroneal nerve injury, are devastating and preventable complications.

For the posterior endoscopic technique, which utilizes posterolateral and posteromedial portals, the patient is typically placed in the prone position. This offers better access to the medial and anterolateral aspects of the posterior subtalar joint. Again, meticulous padding is essential, especially for the anterior aspect of the ankles, knees, and iliac crests.

Surgical Approach: Lateral Intra-Articular Arthroscopy

We'll begin with the standard lateral approach, which is a true intra-articular technique.

Comprehensive Surgical Anatomy for Portal Placement:

Before we make any incisions, let's review the critical neurovascular structures at risk.
* Superficial Peroneal Nerve (SPN): Branches of the SPN course anteriorly and are particularly vulnerable during anterior portal placement. It lies subcutaneously and can be easily injured.
* Sural Nerve: Located posterolaterally, it's at risk during posterior portal placement. It typically runs with the lesser saphenous vein.
* Peroneal Tendons (Peroneus Longus and Brevis): These tendons run posterior to the lateral malleolus and are anterior to the posterior portal.
* Achilles Tendon: The most posterior landmark, serving as a guide for the posterior portal.

Portal Placement:

We utilize three standard portals for visualization and instrumentation: anterior, middle, and posterior.

1. Landmark Identification:

   • Palpate the tip of the lateral malleolus (fibula).
   • Identify the sinus tarsi, which is the soft spot just anterior and inferior to the lateral malleolus.
   • Palpate the Achilles tendon posteriorly.

2. Anterior Portal:

   • Located approximately 1 cm distal to the fibular tip and 2 cm anterior to it.
   • Mark this point on the skin.

3. Middle Portal:

   • Just anterior to the tip of the fibula, directly over the sinus tarsi.
   • This is often our primary viewing portal.

4. Posterior Portal:

   • At or approximately one finger width proximal to the fibular tip and 2 cm posterior to the lateral malleolus.
   • This portal must be placed with extreme caution to avoid the sural nerve and peroneal tendons. A good rule of thumb is to place it behind the lesser saphenous vein and sural nerve, and anterior to the Achilles tendon.

Surgical Warning: Careful, meticulous dissection and precise portal placement are non-negotiable. Always be mindful of the superficial peroneal nerve branches (anterior portal) and the sural nerve and peroneal tendons (posterior portal). Use blunt dissection to protect these structures.

Step-by-Step Intraoperative Execution: The Operating Surgeon's Viewpoint

Let's begin the procedure.

A. Initial Joint Access and Anterior Portal Establishment:

1. Anesthesia and Tourniquet: The patient is under general anesthesia, and the thigh tourniquet is inflated to 250-300 mmHg, or 100 mmHg above systolic pressure.
2. Joint Distension: Take an 18-gauge spinal needle. We'll identify the anterior portal site. Now, carefully insert the needle into the subtalar joint at this anterior portal location. You'll feel a subtle give as you enter the joint capsule.
   

   
   
   

* Fellows, observe: Once confirmed intra-articular, we'll inflate the joint with approximately 10-20 mL of sterile saline solution using a 20-mL syringe. This distension helps to open the joint space, making subsequent portal placement safer and visualization clearer.

B. Diagnostic Inspection from the Anterior Portal:

Our diagnostic examination begins with the arthroscope viewing from this anterior portal.

1. Sinus Tarsi Visualization:
   • Initially, you'll visualize the ligaments that insert on the floor of the sinus tarsi. These can be closely packed and often appear scarred or injured, making differentiation challenging.
   • Rotate the arthroscopic lens slowly to get a panoramic view. We're looking for signs of inflammation, synovitis, or ligamentous tears.
     

     
     
     

* More medially, you'll observe the deep interosseous talocalcaneal ligament filling the tarsal canal. This ligament is a strong divider between the anterior and posterior joint complexes. We often see impingement lesions here, where a torn interosseous ligament or hypertrophic tissue impinges into the anterior aspect of the posterior facet.
* The anterior (left) and posterior (right) facets of the subtalar joint should be visible.

1. Anterior Process of Calcaneus:
   • Slowly withdraw the arthroscope slightly and rotate the lens. We want to view the anterior process of the calcaneus. This area is prone to fracture or impingement.
     

     
     
     

* Get a closer view to inspect for chondral damage or osteophytes.

1. Anterior Aspect of Posterior Talocalcaneal Articulation:
   • Now, rotate the arthroscopic lens in the opposite direction to focus on the anterior aspect of the posterior talocalcaneal articulation. Inspect the cartilage surfaces meticulously for any signs of degeneration, chondromalacia, or osteochondral lesions.
     

     
     
     

1. Lateral Gutter and Ligaments:
   • Next, examine the anterolateral corner of the posterior joint. You'll observe reflections of the lateral talocalcaneal ligament and the calcaneofibular ligament. Note that the lateral talocalcaneal ligament is typically anterior to the calcaneofibular ligament.
     

     
     
     

1. Central Articulation and Posterior Pouch:
   • Rotate the arthroscopic lens medially to view the central articulation between the talus and calcaneus.
   • It is often possible, with careful manipulation and slight distraction, to advance the scope along the lateral and posterolateral gutter. This allows us to visualize the posterior capsular pouch and the Stieda’s process (or os trigonum) if present. This area is common for impingement or loose bodies.
     

     
     
     

C. Middle and Posterior Portal Placement (Under Direct Visualization):

1. Middle Portal:

   • With the arthroscope still in the anterior portal, use an 18-gauge spinal needle to localize the middle portal site from the outside. You'll see the needle tenting the capsule from the inside.
   • Once the position is ideal, make a small skin incision and perform blunt dissection as before. Insert a cannula with a semi-blunt trocar under direct arthroscopic visualization. This "outside-in" technique maximizes safety. The middle portal often serves as our primary working portal.

2. Posterior Portal:

   • Similarly, localize the posterior portal using an 18-gauge spinal needle under direct arthroscopic visualization.
   • Make the skin incision and perform blunt dissection.
   • Insert the trocar in an upward and slightly anterior manner, carefully advancing it into the joint. Again, confirm intra-articular placement and then insert the cannula. This portal often serves as an accessory working portal or for scope exchange.

D. Inspection from the Posterior Portal:

Once all portals are established, we can switch the arthroscope to the posterior portal for a different perspective.

1. Interosseous Ligament: From this posterior view, the interosseous ligament may be seen anteriorly within the joint.
2. Lateral Ligaments: As you rotate the arthroscopic lens laterally, the reflections of the lateral talocalcaneal ligament and calcaneofibular ligament will again come into view, but from a different angle.
3. Central Talocalcaneal Joint: The central talocalcaneal joint can then be thoroughly inspected from this posterior vantage point. This view is excellent for assessing the posterior facet cartilage.

Surgical Approach: Posterior Endoscopic Technique (Extra-Articular)

This technique offers a distinct advantage for addressing certain posterior hindfoot pathologies. It is typically performed with the patient in the prone position.

Portal Placement for Posterior Endoscopy:

This approach utilizes a posterolateral and a posteromedial portal.

1. Landmarks:

   • Achilles tendon.
   • Lateral malleolus.
   • Medial malleolus.
   • Tubercle of the calcaneus.

2. Posterolateral Portal:

   • Typically located just lateral to the Achilles tendon, approximately 1-1.5 cm proximal to the superior border of the calcaneal tuberosity.
   • This portal is used for the arthroscope.

3. Posteromedial Portal:

   • Located just medial to the Achilles tendon, also approximately 1-1.5 cm proximal to the superior border of the calcaneal tuberosity.
   • This portal is typically used for instrumentation.

Surgical Warning: For the posterior approach, be acutely aware of the sural nerve (posterolateral) and the lesser saphenous vein (posterolateral). Medially, the posterior tibial neurovascular bundle (posterior tibial artery, nerve, and vein) and the tendons of the flexor digitorum longus (FDL) and flexor hallucis longus (FHL) are at risk. Meticulous blunt dissection is paramount.

Step-by-Step Intraoperative Execution (Posterior Endoscopic View):

The key difference here is that this technique starts as an extra-articular approach.

1. Extra-Articular Working Space Creation:
   • After skin incision, gently spread the subcutaneous tissues.
   • Using a blunt trocar and cannula, create a working space adjacent to the posterior subtalar joint.
   • This involves meticulously removing the fatty tissue overlying the joint capsule and the posterior part of the ankle joint. This step is critical for clear visualization and instrument mobility.
     

     
     
     

1. Capsular Resection and "Outside-In" Inspection:
   • Once the extra-articular space is clear, the joint capsule is partially removed. This allows us to inspect the joint from the outside in, with the arthroscope positioned at the edge of the joint rather than fully entering the joint space.
   • This approach is particularly useful for addressing posterior impingement, os trigonum excision, or débridement of the posterior subtalar joint without significant intra-articular instrumentation.
   • The maximum size of intra-articular instruments will depend on the available joint space and the extent of capsular resection.

Pearls and Pitfalls: Navigating the Challenges

Subtalar arthroscopy, while minimally invasive, carries its own set of challenges and potential complications.

Pearls for Success:

• Meticulous Preoperative Planning: Thorough review of imaging, especially CT and MRI, is crucial for identifying specific pathology and anatomical variations.
• Anatomical Fluency: A deep understanding of the neurovascular structures and ligamentous anatomy is paramount for safe portal placement. Always anticipate where nerves and vessels lie.
• Joint Distraction: While not explicitly mentioned in the raw text, gentle distraction of the hindfoot can significantly open the subtalar joint space, improving visualization and instrument maneuverability. Consider using a non-invasive ankle distractor.
• Systematic Visualization: Follow a consistent pattern of inspection from each portal to ensure no area is missed.
• Blunt Dissection: Always use blunt dissection (e.g., mosquito clamp) after the initial skin incision to protect underlying neurovascular structures.
• Fluid Management: Maintain adequate inflow and outflow to keep the joint distended and clear of debris and blood. Use gravity or a low-pressure pump.
• Experience with Small Joints: The subtalar joint is tight; experience with wrist or elbow arthroscopy can be beneficial.

Potential Pitfalls and Salvage Strategies:

1. Nerve Injury (Superficial Peroneal, Sural):

   • Prevention: The most critical step. Precise portal marking, careful blunt dissection, and using an "outside-in" technique for secondary portals under direct visualization. For the posterior approach, identify the sural nerve and lesser saphenous vein and ensure portals are safely away.
   • Intraoperative Management: If a nerve is seen or suspected to be injured, immediately stop, identify the nerve, and reassess. If transected, consider immediate primary repair if feasible, or tag the ends for later repair. Postoperatively, monitor for sensory deficits or motor weakness.
   • Postoperative Management: Nerve injury can lead to chronic pain, paresthesia, or even causalgia. Referral to a nerve specialist for evaluation and potential secondary repair or neurolysis may be necessary.

2. Chondral Damage:

   • Prevention: Avoid aggressive instrument manipulation in tight spaces. Always visualize the tip of your instruments. Use smooth, atraumatic cannulas.
   • Intraoperative Management: If iatrogenic chondral damage occurs, assess its size and depth. Small, stable lesions may be left alone. Larger, unstable lesions might require microfracture or débridement, depending on the patient's age and activity level. Document thoroughly.

3. Inadequate Visualization:

   • Cause: Insufficient joint distension, bleeding, synovitis, or extensive adhesions.
   • Salvage:
     • Bleeding: Increase inflow pressure (if using a pump) or elevate the fluid bag. Ensure the tourniquet is fully inflated. If bleeding persists, identify the source and use electrocautery (if appropriate for the location) or temporarily pack the joint.
     • Synovitis/Adhesions: Use a motorized shaver to débride hypertrophic synovium or lyse adhesions.
     • Distension: Re-inflate the joint. Consider additional portals for better instrument access or visualization.
     • Scope Exchange: Sometimes switching to a 70-degree arthroscope can provide a different angle and better view.

4. Infection:

   • Prevention: Strict aseptic technique, prophylactic antibiotics, and minimizing operative time.
   • Postoperative Management: If infection develops (pain, redness, swelling, fever), aspirate the joint for culture and sensitivity. Start empiric antibiotics. May require repeat arthroscopic lavage and débridement.

5. Equipment Failure:

   • Prevention: Always have backup equipment (arthroscope, camera, light source, pump, instruments).
   • **Int

Additional Intraoperative Imaging & Surgical Steps

REFERENCES

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12. Perry J. Anatomy and biomechanics of the hindfoot. Clin Orthop 1983;177:9–15.

13. Scholten PE, Altena MC, Krips R, van Dijk CN. Treatment of a large intraosseous talar ganglion by means of hindfoot endoscopy. Arthroscopy 2003;19:96–100.

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16. Tasto JP, Frey C, Laimans P, et al. Arthroscopic ankle arthrodesis. Instr Course Lect 2000;49:259–280. 17. van Dijk CN, Scholten PE, Krips R. A 2-portal endoscopic approach for diagnosis and treatment of posterior ankle pathology. Arthroscopy 2000;16:871–876.

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19. The patient should be able to return to full activities at 6 to 12 weeks postoperatively.

OUTCOMES
- Compared with open techniques, arthroscopy of the subtalar joint has advantages for the patient, including a faster postoperative recovery period, decreased postoperative pain, and fewer complications.

• Frey et al 2 demonstrated a success rate of 94% good and excellent results in the treatment of various types of subtalar pathology using arthroscopic techniques.

• All of 14 preoperative diagnoses of sinus tarsi syndrome were changed at the time of arthrosocpy.

• The most common finding in these cases was a tear of the interosseous ligaments.

• In a more recent study of 126 cases followed for more than 2 years, a significant improvement (61 to 84) was noted using both the AOFAS and Karslon scores. Williams and Ferkelz 19

reported on the 32-month (average) follow-up of 50 patients with hindfoot pain who underwent simultaneous ankle and subtalar arthroscopy.

• Preoperative diagnoses included degenerative joint disease, sinus tarsi dysfunction, and os trigonum.

• Good to excellent results were noted in 86% of the patients.

• Overall, less favorable results were noted with associated ankle pathology, degenerative joint disease, increased age, and activity level of the patient.

• No operative complications were reported.

• Goldberger and Conti 4 retrospectively reviewed 12 patients who underwent subtalar arthroscopy for symptomatic subtalar pathology with nonspecific radiographic findings.

• The preoperative diagnoses were subtalar chondrosis in nine patients and subtalar synovitis in three patients.

• At 17.5 months (average) of follow-up, the postoperative AOFAS hindfoot score was 71 (range 51 to 85) compared with a preoperative score of 66 (range 54 to 79). All patients stated that they would have the surgery again.