DEFINITION

The subtalar joint is a complex and functionally important joint of the lower extremity. It plays a major role in inversion and eversion of the foot.

Subtalar arthroscopy can be applied as a diagnostic and therapeutic instrument.

Subtalar arthroscopy includes arthroscopy of the sinus tarsi and posterior and anterior subtalar joints.

 

 

ANATOMY

 

For arthroscopic purposes, the subtalar joint is divided into anterior (talocalcaneonavicular) and posterior (talocalcaneal) articulations (FIG 1).

 

The anterior and posterior articulations are separated by the tarsal canal, which has a large lateral opening called the sinus tarsi. The tarsal canal is filled with a thick interosseous ligament. Because of this ligament, there is usually no connection between the anterior and posterior joint complex.

 

Within the tarsal canal and sinus tarsi are found the interosseous talocalcaneal ligament, the medial and intermediate roots of the inferior extensor retinaculum, the cervical ligament, fatty tissue, and blood vessels.5,6,8,12

 

The lateral ligamentous support of the subtalar joint consists of the lateral talocalcaneal ligament, the posterior talocalcaneal ligament, the lateral root of the inferior extensor retinaculum, and the calcaneofibular ligament (FIG 2).

 

 

 

FIG 1 • A,B. The subtalar joint is divided into the anterior (talocalcaneonavicular) and posterior joints (talocalcaneal).

 

 

The anterior subtalar joint is generally thought to be inaccessible to arthroscopic visualization because of the thick interosseous ligament that fills the tarsal canal and the ligaments that insert on the floor of the sinus tarsi.2,3,4,18 However, when there is a tear of the ligaments or they are débrided, the anterior joint can be

visualized.

 

The posterior subtalar joint has a synovial lining. This joint has a posterior capsular pouch with small lateral, medial, and anterior recesses.

 

PATHOGENESIS

 

One of the most common indications for subtalar arthroscopy is chronic pain in the sinus tarsi, historically referred to as sinus tarsi syndrome.2

 

 

 

FIG 2 • The ligaments of the subtalar joint.

 

 

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Sinus tarsi syndrome has been described as persistent pain in the tarsal sinus secondary to trauma (80% of the cases reported).2

 

There are no specific objective findings in this condition.

 

The exact etiology is not clearly defined, but scarring and degenerative changes to the soft tissue structure of the sinus tarsi are thought to be the most common cause of pain in this region.

 

Therefore, sinus tarsi syndrome is an inaccurate term that should be replaced with a specific diagnosis, as it can include many other pathologies, such as interosseous ligament tears, arthrofibrosis, and joint degeneration.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patients with subtalar joint pathology often present with lateral ankle pain that is aggravated by standing and walking activities, particularly on uneven terrain.

 

 

Walking on uneven terrain can result in a feeling of instability.

 

 

Motion of the subtalar joint is not simple inversion and eversion.8,12 However, motion is best tested by holding the left heel in the right hand and vice versa, then using the opposite hand to hold the forefoot and move the foot from inversion to eversion. This motion should be smooth and painless.

 

Inversion and eversion are coming primarily from the talocalcaneal (subtalar) joint. Exact measurements are difficult using standard techniques. Restricted motion may be seen with acute ankle sprain, arthritis, posterior tibial tendon dysfunction, tarsal coalition, fracture, chondral injury, adhesions, synovitis, and inflammatory conditions.

 

There may be swelling or stiffness in the joint.

 

Subtalar stiffness and pain indicate pathology in and around the subtalar joint but are not specific to one diagnosis.

 

Clinical examination reveals pain on the lateral aspect of the hindfoot aggravated by firm pressure over the lateral opening of the sinus tarsi.

 

Relief of symptoms with injection of local anesthetic directly into the sinus tarsi confirms the diagnosis of pain or dysfunction in the sinus tarsi.

 

Pathology of the interosseous ligaments of the subtalar joint usually is associated with focal pain over the lateral entrance to the sinus tarsi. Patients often have slight restriction and discomfort with passive subtalar motion.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Differential injections may be required to confirm pathology in the subtalar joint.

 

 

Anteroposterior (AP), lateral, and modified AP views of the foot are necessary to identify the subtalar joint. The lateral and posterior processes are better seen on hindfoot oblique views.

 

The oblique 45-degree foot films show the anterior portion of the subtalar joint.

 

Broden view shows the posterior facet of the subtalar joint. This view is obtained by rotating the foot medially 45 degrees with dorsiflexion. The x-ray beam is pointed at the lateral malleolus and angled 10 degrees cephalad. Different views are obtained by changing the angle of the x-ray beam from 10 to 40 degrees.

 

Computed tomographic (CT) scans in the coronal plane are best for visualizing the talar body or posterior and lateral processes of the talus. CT can be used to show intraarticular pathology.

 

CT scans in the transverse or sagittal planes are best to visualize the talar neck and dome.

 

Magnetic resonance imaging (MRI) may detect chronic inflammation or fibrosis within the subtalar joint. Ligament injury, bone contusions, osteochondral lesions, chondral injury, impingement, synovitis, and fibrous or cartilaginous coalitions can be well demonstrated on MRI.

 

The preoperative imaging studies predict subtalar cartilage damage less accurately than does arthroscopy.

DIFFERENTIAL DIAGNOSIS

Chronic lateral ankle pain Chronic ankle instability Peroneal tendon pathology

Posterior tibial tendon dysfunction Superficial peroneal nerve pathology

Fracture of the anterior process of the calcaneus Fracture of the lateral process of the talus Fracture of the posterior process of the talus Navicular fracture

Calcaneal cuboid arthrosis/subluxation Calcaneus fracture

 

Coalition

Posterior ankle impingement

 

 

NONOPERATIVE MANAGEMENT

 

 

Injection of anesthetic agent or corticosteroid Foot orthosis, including a UCBL

 

 

 

Anti-inflammatory medication Ankle brace with a hindfoot lock Peroneal tendon strengthening

SURGICAL MANAGEMENT

 

Indications for subtalar arthroscopy include chondromalacia, subtalar impingement lesions, osteophytes, lysis of adhesions with posttraumatic arthrofibrosis, synovectomy, and the removal of loose bodies.1,2,4,7,11

 

Other therapeutic indications include instability, débridement and treatment of osteochondral lesions, retrograde drilling of cystic lesions, evaluation of coalition, removal of a symptomatic os trigonum, evaluation and excision of

 

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fractures of the anterior process of the calcaneus and lateral process of the talus, and subtalar fusion.9,10,15,16

 

 

 

FIG 3 • The patient is placed into the lateral decubitus position with the operative limb draped free.

 

Preoperative Planning

 

Confirm the diagnosis with testing, including differential injections to exclude ankle pathology.

 

The absolute contraindications to subtalar arthroscopy must be ruled out. These include localized infection leading to a potential septic joint and advanced degenerative joint disease, particularly with deformity.

 

Relative contraindications include severe edema, poor skin quality, and poor vascular status.

 

Positioning

 

The patient is placed in the lateral decubitus position with the operative extremity draped free (FIG 3). Padding is placed between the lower extremities as well as under the contralateral extremity to protect the peroneal nerve.

 

A thigh tourniquet is recommended.

 

Approach

Lateral Approach

 

Three standard portals are recommended for visualization and instrumentation of the subtalar joint (FIG 4).

The anatomic landmarks for lateral portal placement are the lateral malleolus, the sinus tarsi, and the Achilles tendon.

 

Careful dissection and portal placement help avoid the superficial peroneal nerve branches (anterior portal) and the sural nerve and peroneal tendons (posterior portal).

 

 

The anterior portal is established approximately 1 cm distal to the fibular tip and 2 cm anterior to it (FIG 5). The middle portal is just anterior to the tip of the fibula, directly over the sinus tarsi.

 

The posterior portal is at or approximately one finger width proximal to the fibular tip and 2 cm posterior to the lateral malleolus.

 

The posterior portal is usually safe when placed behind the saphenous vein and sural nerve and anterior to the Achilles tendon. With placement of the posterior portal, care must be taken to avoid the sural nerve.

 

 

 

 

FIG 4 • Standard portals and their positions.

 

Posterior Approach

 

Posterior subtalar arthroscopy can be performed using a posterolateral and a posteromedial portal. This twoportal endoscopic approach to the hindfoot with the patient in the prone position has been credited with offering better access to the medial and anterolateral aspects of the posterior subtalar joint (FIG 6).13,14,17

 

 

 

FIG 5 • A. Standard subtalar arthroscopic portals demonstrated on a cadaver. B. Anterior and posterior portals with the skin stripped away. Note the proximity of the sural nerve to the posterior portal.

 

 

35

 

 

 

FIG 6 • A-C. Posterior endoscopic technique with the use of two portals.

 

 

36

 

The main difference between the two techniques is that the lateral approach for posterior subtalar arthroscopy is a true arthroscopy technique in which the arthroscope and the instruments are placed within the joint, whereas the twoportal posterior technique (using posterolateral and posteromedial portals) starts as an extra-articular approach.

 

With the two-portal posterior technique, a working space is first created adjacent to the posterior subtalar joint by removing the fatty tissue overlying the joint capsule and the posterior part of the ankle joint.

 

The joint capsule is then partially removed to enable inspection of the joint from the outside-in, with the arthroscope positioned at the edge of the joint without actually entering the joint space.

 

The maximum size of the intra-articular instruments depends on the available joint space.

 

 

TECHNIQUES

 

• Portal Placement

   

  Local, general, spinal, or epidural anesthesia can be used for this procedure.

   

  The anterior portal is identified first with an 18-gauge spinal needle, and the joint is inflated with a 20-mL syringe (TECH FIG 1).

   

  A small skin incision is made and the subcutaneous tissue is gently spread using a straight mosquito clamp.

   

   

   

  TECH FIG 1 • The subtalar joint is entered using an 18-gauge spinal needle. The joint is inflated (A) and an incision is made (B), followed by blunt dissection (C) and entry into the subtalar joint (D). The middle portal is made using direct visualization techniques.

   

   

  A cannula with a semiblunt trocar is then placed, followed by a 2.7-mm 30-degree oblique arthroscope.

   

  The middle portal is placed under direct visualization using an 18-gauge spinal needle and outside-in technique.

   

  The posterior portal can be placed at this time using the same direct visualization technique. The trocar is placed in an upward and slightly anterior manner.

• Inspection from the Anterior Portal

   

  Diagnostic subtalar arthroscopy examination begins with the arthroscope viewing from the anterior portal (TECH FIG 2A,B). The ligaments that insert on the floor of the sinus tarsi are visualized. It is easy to get disoriented, as the ligaments are closely packed and cross over one another in the sinus tarsi.

   

  More medially, the deep interosseous ligament (TECH FIG 2C) is observed to fill the tarsal canal.

   

  The arthroscope should now be slowly withdrawn and the arthroscopic lens rotated to view the anterior process of the calcaneus (TECH FIG 3A,B).

   

  The arthroscopic lens is then rotated in the opposite direction to view the anterior aspect of the posterior talocalcaneal articulation (TECH FIG 3C).

   

  Next, the anterolateral corner of the posterior joint is examined, and reflections of the lateral talocalcaneal ligament and the calcaneofibular ligament are observed (TECH FIG 3D). The lateral talocalcaneal ligament is noted anterior to the calcaneofibular ligament.

   

  The arthroscopic lens may then be rotated medially and the central articulation observed between the talus and the calcaneus (TECH FIG 3E). The posterolateral gutter may be seen from the anterior portal.

   

  It is often possible to advance the scope along the lateral and posterolateral gutter and visualize the posterior pouch and Stieda process (or os trigonum; TECH FIG 3F).

   

  37

   

   

   

  TECH FIG 2 • With the arthroscope in the anterior portal, the ligaments that insert on the floor of the sinus tarsi can be visualized. It is often difficult to tell one from the other, especially if they are injured. A,B. Examples of a torn interosseous ligament that is impinging into the anterior aspect of the posterior facet of the subtalar joint. This impingement lesion is referred to as the subtalar impingement lesion. C. The interosseous ligament of the tarsal canal fills the canal and can be seen with the scope in the anterior portal. The anterior (left) and the posterior (right) facets are well seen.

   

   

   

  TECH FIG 3 • Views with the arthroscope in the anterior portal. A. Anterosuperior process of the calcaneus. This view is useful for inspection and débridement or resection of a fracture in this location. B. Closer view of the anterior process. C. Anterior aspect of the posterior facet (to the right). D. Lateral gutter and lateral talocalcaneal and calcaneofibular ligaments. E. Anterior and central aspects of the posterior talocalcaneal articulation (to the right). F. It is possible to advance the scope from the anterior portal and visualize the

  lateral aspect of the posterior capsule and Stieda process or os trigonum.

   

• Inspection from the Posterior Portal

   

  The arthroscope is then switched to the posterior portal. From this view, the interosseous ligament may be seen anteriorly in the joint. As the arthroscopic lens is rotated laterally, the lateral talocalcaneal ligament and calcaneofibular ligament reflections again may be seen.

   

  The central talocalcaneal joint may then be seen from this posterior view and the posterolateral gutter examined (TECH FIG 4A).

   

  The posterolateral recess, posterior gutter, and posterolateral corner of the talus are visualized (TECH FIG 4B). The posteromedial recess and posteromedial corner of the talocalcaneal joint can also be seen from the posterior portal.

   

  38

   

   

   

  TECH FIG 4 • Views with the arthroscope in the posterior portal. A. Posterior and central aspects of the posterior talocalcaneal joint can be seen to the right. The posterior capsule is to the left. B. Lateral aspect of the posterior capsule and Stieda process or the os trigonum.

• Sinus Tarsi Pathology

   

  The best portal combination for the evaluation and débridement of pathology in the sinus tarsi is the arthroscope in the anterior portal and the instruments in the middle portal.

   

  One can débride torn interosseous ligaments, remove loose bodies, and perform lysis of adhesions. A radiofrequency wand is a useful tool to access the hard-to-get-to spots in the sinus tarsi and subtalar joint.

• Os Trigonum Pathology

   

  The best portal combination for evaluation and removal of the os trigonum is the arthroscope in the anterior portal and the instrumentation in the posterior portal.

   

  The os trigonum or a symptomatic Stieda process can be débrided with a burr or shaver and removed through an arthroscopic portal using a standard arthroscopic grabber (TECH FIG 5).

   

  Rarely, it is necessary to enlarge the portal for delivery of the os trigonum.

   

   

   

  TECH FIG 5 • A fracture of Stieda process or an injured os trigonum can be removed using standard arthroscopic grabbers. Rarely, the incision must be expanded to deliver the fragment.

• Arthroscopic Subtalar Arthrodesis

   

  Both the anterior and posterior portals are used in an alternating fashion during the procedure for viewing and for instrumentation.

   

  It is important to obtain a fusion of the posterior facet. The anterior facet is generally not fused. A primary synovectomy and débridement are necessary for visualization.

   

  Débridement and complete removal of the articular surface of the posterior facet of the subtalar joint down to subchondral bone is the next phase of the procedure.

   

  Once the articular cartilage has been resected, approximately 1 to 2 mm of subchondral bone is removed to expose bleeding cancellous bone.

   

  Spot weld holes measuring approximately 2 mm in depth are created on the surfaces of the calcaneus and talus to create vascular channels.

   

  The posteromedial corner is inspected to ensure adequate débridement.

   

  The guidewire for a large cannulated screw (6.5 to 7 mm) can be visualized as it enters the posterior facet.

   

  The foot is then put in about 0 to 5 degrees of valgus, the guidewire is advanced, and the screw is placed.

   

   

  Screw position and length are confirmed with fluoroscopy. Postoperative care is similar to open techniques.

   

  In general, no autogenous bone graft or bone substitute is needed.

   

   

  39

  PEARLS AND PITFALLS

   

  The subtalar joint can be difficult to distract, especially the posterior joint.

  • Use of a distraction device is not necessary or very useful for improving visualization of the subtalar joint. A high-flow system and an arthroscopic pump will improve visualization.

  • Rarely, invasive joint distraction, using talocalcaneal distraction with pins inserted from laterally, or tibiocalcaneal distraction can be used in a patient with a tight posterior subtalar joint. The disadvantage of using an invasive distractor is the potential damage to soft tissues (especially the lateral calcaneal branch of the sural nerve) and ligamentous structures and the risk of infection and fracturing the talar neck or body.

 

Visualization of the anterior joint and sinus tarsi can be difficult. It is easy to get disoriented, as the ligaments are closely packed and cross over one another in the sinus tarsi.

• The structures in the sinus tarsi, the anterior process of the calcaneus, and, occasionally, the anterior joint can be visualized best by placing the arthroscope through the anterior portal and instrumentation through the middle portal. This portal combination is recommended for visualization and instrumentation of the sinus tarsi and anterior aspects of the posterior subtalar joint. If the ligaments that insert on the floor of the sinus tarsi are torn or damaged or need débridement, the anterior joint can be visualized and accessed with this portal combination. Furthermore, this portal combination allows excellent visualization and access to the anterior process of the calcaneus.

   

  Visualization of the posterior joint and lateral capsule and access to Stieda process (os trigonum)

• The best portal combination for access to the posterior joint is placement of the arthroscope through the anterior portal and instrumentation through the posterior portal. This allows direct visualization and access of nearly the entire surface of the posterior facet, the posterior aspect of the ligaments in the sinus tarsi, the lateral capsule and its small recess, Stieda process (os trigonum), and the posterior pouch of the posterior joint with its synovial lining.

 

POSTOPERATIVE CARE

 

After completing the procedure, the portals are closed with sutures.

 

A compression dressing is applied from the toes to the midcalf. Ice and elevation are recommended until the inflammatory phase has passed.

 

 

The patient is allowed to ambulate with the use of crutches and weight bearing is permitted as tolerated. The sutures are removed approximately 10 days after the procedure.

 

The patient should begin gentle active range-of-motion exercises of the foot and ankle immediately after surgery. Once the sutures are removed, if indicated, the patient is referred to a physical therapist for supervised rehabilitation.

 

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 al2 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 arthroscopy. 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 American Orthopaedic Foot and Ankle Society (AOFAS) and Karlsson scores.

Williams and Ferkel19 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 Conti4 retrospectively reviewed 12 patients who underwent subtalar arthroscopy for symptomatic subtalar pathology with nonspecific radiographic findings.

The preoperative diagnoses were subtalar chondrosis in 9 patients and subtalar synovitis in 3 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.

Surgical removal of the contents of the lateral half of the sinus tarsi improves or eradicates symptoms in roughly 90% of cases of patients with sinus tarsi pain or dysfunction.2

 

 

COMPLICATIONS

Although rare, the most likely complication to occur after subtalar arthroscopy is injury to any of the neurovascular structures in the proximity of the portals, including the sural nerve and superficial peroneal nerve.

Other possible complications following subtalar joint arthroscopy include infection, instrument breakage, and damage to the articular cartilage.

 

 

REFERENCES

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

    

    

3. Frey C, Gasser S, Feder K. Arthroscopy of the subtalar joint. Foot Ankle Int 1994;15:424-428.

    

    

4. Goldberger MI, Conti SF. Clinical outcome after subtalar arthroscopy. Foot Ankle Int 1998;19:462-465.

    

    

5. Harper MC. The lateral ligamentous support of the subtalar joint. Foot Ankle 1991;11:354-358.

    

    

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6. Inman VT. The subtalar joint. In: Inman VT, ed. The Joints of the Ankle. Baltimore: Williams & Wilkins, 1976:35-44.

    

    

7. Jaivin JS, Ferkel RD. Arthroscopy of the foot and ankle. Clin Sports Med 1994;13:761-783.

    

    

8. Lapidus PW. Subtalar joint, its anatomy and mechanics. Bull Hosp Joint Dis 1955;16:179-195.

    

    

9. Lundeen RO. Arthroscopic fusion of the ankle and subtalar joint. Clin Podiatr Med Surg 1994;11:395-406.

    

    

10. Mekhail AO, Heck BE, Ebraheim NA, et al. Arthroscopy of the subtalar joint: establishing a medial portal. Foot Ankle Int 1995;16:427-432.

     

     

11. Parisien JS. Posterior subtalar joint arthroscopy. In: Guhl JF, Parisien JS, Boynton MD, eds. Foot and Ankle Arthroscopy, ed 3. New York: Springer-Verlag, 2004:175-182.

     

     

12. Perry J. Anatomy and biomechanics of the hindfoot. Clin Orthop Relat Res 1983;(177):9-15.

     

     

13. Scholten PE, Altena MC, Krips R, et al. Treatment of a large intraosseous talar ganglion by means of hindfoot endoscopy. Arthroscopy 2003;19:96-100.

     

     

14. Sitler DF, Amendola A, Bailey CS, et al. Posterior ankle arthroscopy: an anatomic study. J Bone Joint Surg Am 2002;84-A(5):763-769.

     

     

15. Tasto JP. Arthroscopic subtalar arthrodesis. Tech Foot Ankle Surg 2003;2:122-128.

     

     

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.

     

     

18. Viladot A, Lorenzo JC, Salazar J, et al. The subtalar joint: embryology and morphology. Foot Ankle 1984;5:54-66.

     

     

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