DEFINITION

Lateral or posterior subtalar arthroscopy confers diagnostic and potentially therapeutic value in treating subtalar trauma, arthrofibrosis, impingement, and cartilage pathology.

One must establish a definitive diagnosis of subtalar pathology based on physical examination and detailed imaging studies improve the likelihood of successful outcome with subtalar arthroscopy.

Exploratory, or diagnostic, subtalar arthroscopy is rarely indicated.

Based on preoperative physical examination and detailed imaging, determination may be made if lateral or posterior subtalar arthroscopy is favored to access subtalar pathology.

 

 

ANATOMY

 

The subtalar joint comprises the talus and three facets of the superior articular surface of the calcaneus: anterior, middle, and posterior facet.

 

 

Functionally, the subtalar joint is separated into an anterior (anterior and middle articular surfaces, often confluent) and posterior portion.

 

The posterior facet is the largest and bears the majority of the body weight.

 

The tarsal canal (contents: talar body blood supply, talocalcaneal interosseous, inferior extensor retinaculum, and cervical ligaments) separates the anterior and posterior portions of the subtalar joint. Its lateral opening is the sinus tarsi.

 

The anterior and middle facets are usually inaccessible unless the interosseous ligament is torn.

 

Subtalar motion is not pure inversion and eversion with inversion/eversion and measuring subtalar motion is rarely exact given the subtalar joint's couple with the ankle.

 

PATHOGENESIS

 

Not much literature is dedicated to osteochondral lesions of the subtalar joint.

 

Snowboarders, with their hindfoot held in place with stiff boots during a fall, in addition to lateral talar process fractures, may experience injury to the middle facet of the subtalar joint.

 

 

The sustentaculum tali and middle facet are impacted.1

 

 

Sinus tarsi syndrome is clinically described as lateral pain over the sinus tarsi. Although the etiology of sinus tarsi syndrome is unknown, several theories exist3:

 

Scarring and fibrosis of interosseous or cervical ligament

 

Subtalar synovitis

 

Sinus fat pad alterations and scarring

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Commensurate with the patient's complaint of hindfoot soreness, stiffness, and, occasionally, a sense of instability, particularly while walking on uneven surfaces, physical examination of the hindfoot demonstrates pain and limited motion.

 

By stabilizing the ankle, typically with thumb support on the medial talar neck, some sense of subtalar inversion/eversion compared to the contralateral hindfoot should identify pain and restriction of motion.

 

The patient often describes diffuse hindfoot pain, medially, laterally, and posteriorly.

 

Sinus tarsi tenderness is a consistent finding suggestive of anterior subtalar pathology, often due to interosseous ligament sprain or lateral process avulsion injury.

 

Pain with forced eversion may suggest lateral subtalar gutter impingement and is generally the most sensitive area on examination of a patient with subtalar pathology.

 

Pain with forced plantarflexion is not definitive for the ankle or subtalar joint but may be due to posterior subtalar impingement.

 

Due to the coupled ankle and subtalar mechanism, subtalar and ankle instability are often difficult to distinguish from ankle instability. Moreover, reliable and reproducible stress maneuvers that isolate subtalar motion have not been developed.

 

Although invasive, perhaps the best test to isolate subtalar pathology is local anesthetic subtalar injection via the sinus tarsi.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Radiographs

 

 

May not reveal diagnosis

 

Anteroposterior (AP), lateral, and oblique weight-bearing views of the foot

 

 

 

45-degree oblique view: anterior portion of the subtalar joint (FIGS 1A and 2A) Broden view: posterior facet (FIG 1B)

 

The foot is placed in neutral flexion, and the leg is internally rotated 30 to 40 degrees. The x-ray beam is centered over the lateral malleolus, and four x-rays are made with the tube angled 40-, 30-, 20-, and 10-degree cephalic tilt. The 10-degree view shows the posterior portion of the posterior facet and the 40-degree view shows the anterior portion.

 

Lateral oblique: posterior facet

 

 

Foot is dorsiflexed, everted, and externally rotated to 60 degrees.

 

Beam is centered 2 cm below medial malleolus with 10-degree cephalic tilt.

 

 

P.729

 

 

 

FIG 1 • A 25-year-old man with persistent right hindfoot pain. A. Lateral radiograph suggests possible posterior subtalar pathology. B. Broden view demonstrates lateral osteochondral defect. Sagittal computed tomography (CT; C) and magnetic resonance imaging (MRI; E) reveal osteochondral defect of posterior calcaneal facet. Coronal CT (D) and MRI (F) demonstrate large lateral osteochondral defect.

 

 

Computed tomography

 

 

 

Cystic component of osteochondral lesions of the subtalar joint (FIGS 1C,D and 2C,D) Subchondral sclerosis, cystic changes consistent with arthritis

 

Magnetic resonance imaging

 

 

 

Cartilage or osteochondral defects (FIGS 1E,F and 2E,F) Edema associated with osteochondral lesions

 

Sinus tarsi pad fat changes

 

 

 

Interosseous or cervical ligament tears Stress reactions

 

Fibrosis within subtalar joint

 

Cartilaginous coalitions

 

 

 

FIG 2 • A 22-year-old male with persistent right hindfoot pain. Lateral radiograph (A) suggests possible posterior subtalar pathology. The sagittal MRI (D) and CT (B) reveal an osteochondral defect of posterior calcaneal facet. The coronal MRI (E) and CT (C) confirm the centro-lateral posterior facet location of the osteochondral defect.

 

DIFFERENTIAL DIAGNOSIS

 

 

 

Lateral ankle instability Peroneal tendon pathology Fractures of:

 

Lateral talar process

 

 

Anterior beak of the calcaneus Stieda process

 

 

Navicular Calcaneus

 

 

 

Osteochondral lesions of the inferior surface of talus or posterior facet of calcaneus Edema associated with osteochondral lesions

 

 

 

Subtalar arthritis Stress reactions

 

 

Fibrosis within subtalar joint Cartilage coalitions

 

P.730

NONOPERATIVE MANAGEMENT

 

Functional rehabilitation includes range of motion for the ankle and hindfoot, concentric and eccentric muscle strengthening, endurance training with particular attention to the peroneal musculature, and proprioceptive exercises.

Anesthetic (with or without corticosteroid) injection into the sinus tarsi UCBL orthosis to limit inversion/eversion

Nonsteroidal anti-inflammatory agent

 

SURGICAL MANAGEMENT

Indications

Sinus tarsi syndrome with identifiable pathology Chondral and osteochondral lesions

Chronic synovitis Adhesions, arthrofibrosis Loose bodies

Mild arthritis

Impingement (os trigonum)

 

 

Contraindications

Local soft tissue/bone infection Severe arthritis/deformity

Poor vascular status Edema

Chronic regional pain syndrome

 

 

Preoperative Planning

 

 

Imaging studies must be reviewed so that the location of the lesion is identified. Plain films must be reviewed for degenerative changes, malalignment, and fractures.

 

Physical examination, combined with preoperative imaging, typically directs if lateral or posterior subtalar arthroscopy is favored to access the specific subtalar pathology.

 

 

In general, lateral subtalar arthroscopy is favored for sinus tarsi and anterior pathology, including the anterior one-half of the subtalar joint.

 

Posterior arthroscopy is favored for posterior hindfoot impingement and pathology isolated to the posterior half of the subtalar joint.

 

 

Lateral subtalar and lateral gutter pathology may be better accessed with the lateral subtalar arthroscopy. Medial subtalar pathology is difficult to access from either lateral or posterior portals.

 

 

TECHNIQUES

• Lateral Arthroscopy for Anterior and Lateral Subtalar Pathology

Background

 

A 25-year-old man with a 6-month history of hindfoot pain after inversion ankle/hindfoot injury, failing nonoperative measures.

 

Physical examination and imaging studies (see FIG 1) suggested lateral gutter impingement, sinus tarsi pathology, and lateral osteochondral lesion of the posterior calcaneal facet.

Positioning

 

A well-padded thigh tourniquet is placed.

 

 

Lateral subtalar arthroscopy set up for anterior and/or lateral subtalar gutter pathology (TECH FIG 1) The patient is maintained in a lateral decubitus position.

 

 

TECH FIG 1 • Lateral subtalar arthroscopy is facilitated with the patient in the lateral decubitus position and the operated ankle suspended from a support under the lower leg to open the subtalar joint.

 

 

In general, a beanbag or dedicated lateral positioning device is preferred to maintain the patient in proper position for lateral subtalar arthroscopy.

 

Positioning the patient in less than the full lateral decubitus position will limit satisfactory access to the posterior portal for the lateral approach.

 

A support placed under the medial malleolus allows the subtalar joint to fall open and improve access.

Establishing Portals

 

Mark the three portals (TECH FIG 2).

 

Anterior portal

 

2 cm anterior and 1 cm distal lateral malleolus tip (distal portion of the sinus tarsi)

 

 

Mostly a viewing portal Middle portal

 

Just distal and inferior lateral malleolus tip

 

 

Mostly an instrument portal; best for sinus tarsi pathology Posterior portal

 

 

1 cm proximal lateral malleolus tip and anterior to Achilles Just distal and inferior lateral malleolus tip

 

Mostly an instrument portal

 

From this portal, one can débride hypertrophic or inflamed synovium, remove impinging structures, and remove an os trigonum.

 

The location for the anterior portal is first identified with palpation, dorsal to the calcaneal angle of Gissane in the sinus tarsi. Prior to creating the portal, the proper trajectory for passing anterior portal instrumentation is confirmed with a spinal needle. (TECH FIG 2B).

 

P.731

 

 

 

TECH FIG 2 • A. Lateral subtalar joint arthroscopy portals. Tip of fibula marked. Middle portal, immediately distal and inferior to the tip of the fibula. Anterior portal, 1 cm inferior and 2 cm anterior to the tip of the fibula. The posterior portal is just proximal to the tip of the fibula and immediately posterior to the peroneal tendons. B. To determine the anterior portal, a spinal needle is placed into sinus tarsi immediately superior to anterior calcaneus at the angle of Gissane. C. Sterile saline is introduced to expand the anterior subtalar joint. D. Introduction of the arthroscope into the anterior portal. Note skin tension due to anterior portal made too proximally; ideally, portal should be created at the proper location without tensioning the skin. E. To create the middle portal, a spinal needle is introduced to determine the ideal trajectory for instrumentation. Direct visualization is possible with the anterior arthroscope. F. Shaver introduced in trajectory determined with spinal needle.

 

 

 

The subtalar joint is insufflated with 10 mL of saline (TECH FIG 2C). A stab incision is made with a no. 10 blade.

 

Protect the sural nerve by making only a superficial skin incision and perform blunt dissection to the

subtalar joint.

 

The subcutaneous tissue is spread with a hemostat clamp.

 

This nick and spread technique helps to avoid sural nerve injury.

 

The trocar, followed by the arthroscope and camera with a fluid inflow source, is inserted (TECH FIG 2D).

 

The middle portal is created.

 

A spinal needle may be inserted to determine the optimal trajectory based on direct visualization within the joint (TECH FIG 2E).

 

The shaver is introduced into the anterior subtalar joint under direct visualization from within the joint (TECH FIG 2F).

Viewing from the Anterior Portal and Working from the Middle Portal

 

Viewing from the anterior portal, inspect the floor of the sinus tarsi.

 

Approximately 75% of the posterior facet may be visualized from this position.

 

The initial view may be obscured by sinus tarsi scar or inflammatory tissue (TECH FIG 3A).

 

With an arthroscopic shaver introduced through the middle portal, the reactive synovium and scar may be débrided to expose the anterior aspect of the posterior subtalar joint (TECH FIG 3B).

 

Medially, the talocalcaneal interosseous ligament fills the tarsal canal.

 

Medial scar tissue may be visualized medial to the ligament (TECH FIG 3C) and débrided under direct visualization (TECH FIG 3D).

 

The lens is rotated to visualize the middle facet medially and anterior calcaneal process laterally.

 

Occasionally, more anterior débridement may be facilitated by placing the arthroscope in the middle portal and the shaver in the anterior portal.

 

After anterior débridement, the camera is rotated to inspect the posterior subtalar joint and the posterior calcaneal facet.

 

In this case, the lateral posterior facet osteochondral defect is noted and the unstable cartilage is mobilized with a probe (TECH FIG 3E).

 

With the camera in the anterior portal and the shaver in the middle portal, the osteochondral defect can be effectively débrided (TECH FIG 3E-G).

 

After débridement is complete, a dedicated small joint awl may be substituted for the shaver to perform microfracture of the osteochondral defect (TECH FIG 3H) followed by further débridement (TECH FIG 3I).

 

P.732

 

 

 

TECH FIG 3 • A. Shaver initially obscured by sinus tarsi scar tissue. B. Débridement to expose anterior subtalar joint. C. Scarring noted medial and deep to the anterior aspect of the posterior facet and interosseous ligament. D. Débridement of the medial scar tissue. E. Visualizing of the osteochondral defect form the anterior portal. F. Probing the defect to identify unstable cartilage in the defect with probe through the middle portal. G. Débridement of the defect with the shaver introduced through the middle portal. H. The small joint awl introduced through the middle portal to perform microfracture of the defect.

I. Further débridement after microfracture. J. With the arthroscope in the anterior portal, the spinal needle is directly visualized entering the posterolateral joint. K. Shaver introduced posteriorly. L. Visualization from anterior arthroscope of lateral gutter débridement with shaver introduced into the posterolateral portal.

 

 

P.733

 

With the camera still in the anterior portal, a posterior portal may be created by directing the arthroscope into the lateral subtalar gutter and directly visualizing the spinal needle inserted from the intended posterior portal (TECH FIG 3J).

 

To protect the sural nerve, the posterior portal should be created with a superficial stab incision in the skin and blunt dissection through the posterolateral subtalar capsule.

 

 

The shaver is then introduced through the posterior portal (TECH FIG 3K). Scar tissue in the lateral gutter may be readily débrided (TECH FIG 3L).

 

 

 

TECH FIG 4 • A. Arthroscope introduced from posterior portal with shaver in anterior portal. B. Visualization of subtalar joint and débrided osteochondral defect from posterior portal. C. Further lateral gutter débridement with visualization from posterior portal and shaver introduced from middle portal.

Viewing from the Posterior Portal

 

The arthroscope is removed from the anterior portal and the trocar and camera are introduced into the posterior portal (TECH FIG 4A).

 

The subtalar joint may be visualized, and in this case, the débrided lateral osteochondral defect may be inspected (TECH FIG 4B).

 

The lateral gutter may also be viewed from the posterior portal and further débridement is possible by introducing the shaver from the middle or anterior portal (TECH FIG 4C).

• Posterior Arthroscopy for Isolated Posterior Subtalar Pathology

Background

 

A 22-year-old man presented with a 6-month history of persistent hindfoot symptoms after inversion ankle/hindfoot injury.

 

Physical examination and imaging suggested posterior hindfoot pathology.

 

Although forced plantarflexion reproduced the symptoms, imaging suggested that the symptoms were due to a central and posterior osteochondral lesion of the posterior calcaneal facet (see FIG 2).

Positioning

 

The patient is positioned prone with the chest and iliac crest well padded.

 

 

A support is placed immediately proximal to the ankle so the tibiotalar joint can plantarflex and dorsiflex. Airway is well maintained.

 

 

No tension on the brachial plexi and ulnar nerves at the elbows free of pressure All bony prominences well padded

Approach

 

Two small skin incisions are made at the level of the fibula 1 cm from the medial and lateral border of the Achilles tendon.

 

These incisions should not be made too close to the Achilles tendon, as this can cause overcrowding and difficulties maneuvering the instrumentation.

 

The skin incisions should be superficial only and blunt dissection is carried through the posterior soft tissues to the posterior subtalar joint.

 

Laterally, the sural nerve is at risk.

 

Medially, the posteromedial neurovascular bundle is at risk.

 

Viewing from the Posterolateral Portal and Working from the Posteromedial Portal

 

The arthroscope is routinely placed in the posterolateral portal (TECH FIG 5A,B).

 

The camera should be directed medially to visualize the instrumentation.

 

The shaver is introduced into the medial portal.

 

Routinely, considerable adipose and fibrous tissue must be removed from the space immediately posterior to the subtalar joint (TECH FIG 5C).

 

Before any pathology is addressed, the flexor hallucis longus (FHL) tendon must be identified, as it serves as the medial reference point to protect the posteromedial neurovascular bundle (TECH FIG 5D).

 

One of the most common indications for posterior hindfoot arthroscopy is to remove a symptomatic os trigonum.

 

In this case, inspection of the posterior facet demonstrates a central posterior osteochondral lesion with unstable cartilage (TECH FIG 5E-G).

 

Débridement of unstable cartilage from the posterior facet osteochondral defect (TECH FIG 5H,I).

 

 

P.734

 

 

 

TECH FIG 5 • A. Patient prone and posterior hindfoot portals created. B. Arthroscope posterolateral and instrumentation posteromedial so that the instrumentation and FHL tendon (reference structure to posteromedial neurovascular bundle) may be simultaneously and safely visualized. C. Arthroscope viewing from posterolateral portal and shaver introduced from posteromedial portal. D. Posterior subtalar joint visualized with shaver immediately anterior and medial to the FHL tendon. E. Identifying unstable posterior facet cartilage. F. Probe introduced through posteromedial portal. G. Unstable cartilage assessed. H. Débridement of unstable cartilage using curette introduced through posteromedial portal. I. Shaver from posteromedial portal to remove débrided unstable cartilage fragments. J,K. This small joint microfracture awl system uses a tamp that directly impacts on the dorsal aspect of the awl. (continued)

 

 

P.735

 

TECH FIG 5 • (continued) L. At the conclusion of microfracture, the tourniquet is released and inflow discontinued to determine bleeding from the microfractured osteochondral defect. M. In this case, bleeding from the microfractured area serves as an indicator for a favorable healing potential.

Microfracture using dedicated small joint microfracture instrumentation.

In this case, two different systems are demonstrated. The external images demonstrate a system that includes a tamp to impact more vertically on the awl. The internal images demonstrate a more traditional awl where the impact occurs directly on the proximal aspect of the awl handle (TECH FIG 5J,K).

At the conclusion of microfracture, the tourniquet is released and inflow discontinued to demonstrate bleeding from the microfractured osteochondral defect, in anticipation that bleeding is an indicator for a favorable healing potential (TECH FIG 5L,M).

 

 

 

Anterior or lateral

subtalar pathology

• Consider using lateral subtalar arthroscopy technique.

Posterior subtalar

pathology

• Favor using posterior subtalar arthroscopy technique.

Medial subtalar

pathology

• Accessing medial subtalar pathology is difficult from either the lateral or

posterior subtalar arthroscopic technique.

Avoid nerve injury

• Superficial skin incisions only and blunt dissection to enter the subtalar

joint

PEARLS AND PITFALLS

 

 

POSTOPERATIVE CARE

 

Early range of motion is possible, but if an osteochondral defect was managed surgically, consideration may

want to be given to protected weight bearing for 3 to 4 weeks.

 

An initial cam boot is recommended to protect the foot while the portal sites are healing.

 

 

Partial weight bearing allowed immediately and continued for to 4 weeks if microfracture performed. Consideration may be given to physical therapy to be started after portal sites are healed.

 

 

Initial follow-up at approximately 7 to 10 days for wound inspection and possible suture removal Return to full activity may take 3 months or more.

With an osteochondral defect, recommend low-impact exercise

OUTCOMES

Data on the 45-month follow-up of 49 patients was published by Frey et al.2

These patients had subtalar arthroscopic débridement for various pathologies including arthrofibrosis, sinus tarsi syndrome, interosseous ligament tears, coalition, and osteochondral lesion of the subtalar joint.

Of the patients who had a preoperative diagnosis of sinus tarsi syndrome, all of their postoperative diagnoses changed to either interosseous ligament injury, arthrofibrosis, or arthritis.

Ninety-four percent of patients had excellent/good results, which meant that they had, at the very most, some pain or lifestyle restrictions.

 

 

COMPLICATIONS

Wound complications Sural or tibial nerve injury Persistent pain

Iatrogenic cartilage damage

 

 

REFERENCES

1. Clanton TO, Chacko AK, Matheny LM, et al. Magnetic resonance imaging findings of snowboarding osteochondral injuries to the middle talocalcaneal articulation. Sports Health 2013;5(5):470-475.

    

    

2. Frey C, Feder KS, DiGiovanni C. Arthroscopic evaluation of the subtalar joint: does sinus tarsi syndrome exist? Foot Ankle Int 1999;20(3):185-191.

    

    

3. Lee KB, Bai LB, Song EK, et al. Subtalar arthroscopy for sinus Tarsi syndrome: arthroscopic findings and clinical outcomes of 33 consecutive cases. Arthroscopy 2008;24(10):1130-1134.