Arthroscopy of the Subtalar Joint

CHAPTER PREVIEW

CHAPTER SYNOPSIS:

This chapter reviews the potential role for subtalar arthroscopy for subtalar arthritis. Subtalar arthroscopy is not as developed as ankle arthroscopy, but it is still of considerable benefit to surgeons and patients once the technique can be mastered. Arthroscopy avoids dissection of the tissues around the subtalar joint, potentially reducing postoperative pain, bleeding, and wound complications and maintaining better blood supply to the region. Minimal outcome data are available to date to determine the role for this procedure for arthritic patients, but early research is encouraging.

IMPORTANT POINTS:

1

Subtalar arthroscopy allows removal of loose bodies or a less invasive fusion for patients with arthritis.
2

The joint is tight to enter; therefore, advanced arthritis or a joint with marked deformity may not be suitable for arthroscopy.
3

A cadaver course is recommended to learn subtalar arthroscopy.

CLINICAL/SURGICAL PEARLS:

1

The joint can be approached either from the lateral side or posteriorly.
2

Subcutaneous sensory nerves are close to the portals, so dissection should be blunt in the subcutaneous plane.
3

A small scope (1.9 mm or 2.4 mm) is required.
4

The central axis of the subtalar joint lies under the tip of the lateral malleolus. Insertion of the scope from this point will allow the best visualization of the joint.
5

Arthroscopic fusion is the best procedure to perform first as part of the learning curve.

CLINICAL SURGICAL PITFALLS:

1

Do not use sharp dissection subcutaneously as this may damage the sural or peroneal nerve.
2

Avoid penetration of the posterior medial corner of the posterior facet as this may damage the tibial nerve.
3

Make sure extra time is booked for the first cases.
4

Learn the procedure first on a cadaver to avoid damage to cartilage and nerves.

VIDEO AVAILABLE:

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Arthroscopic subtalar arthrodesis; lateral approach.

HISTORY/INTRODUCTION/SCOPE OF THE PROBLEM

Subtalar arthroscopy has evolved as a result of the success of ankle arthroscopy and improved smaller arthroscopic equipment. However, the technique remains largely in its early stages. The indications and contraindications for subtalar arthroscopy continue to evolve as the techniques become more refined. The body of literature involving subtalar arthroscopy is largely retrospective in design and lacks control groups. Many authors have reported successful outcomes in managing subtalar pathology arthroscopically. Damage to the neurovascular structures and the articular surface remain a concern. This chapter will review all of these issues and speculate on the future of this technique.

Although arthroscopy of the subtalar joint may not be considered as mainstream as arthroscopy of the ankle joint, it is advantageous in several circumstances. Since the first description of arthroscopy of the subtalar joint by Parisien in 1986, there have been numerous techniques described and the indications have diversified. There are several advantages of subtalar arthroscopy over open arthrotomy including less morbidity and faster rehabilitation. Arthroscopy avoids detachment of the extensor digitorum brevis, fat pad excision, and transaction of the cervical ligament that delays recovery after an open arthrotomy.

INDICATIONS

Arthroscopy of the subtalar joint can be performed for diagnostic or therapeutic reasons. Pain, stiffness, and locking that are not adequately explained by other diagnostic modalities and that fail nonoperative management are indications for subtalar arthroscopy. The indications for theraputic subtalar arthroscopy includes debridement for chondromalacia, arthrofibrosis, synovitis, loose bodies, os trigonum excision, arthrodesis, and reduction of calcaneal fractures. The most common indications in our practice are for the removal of loose bodies or subtalar arthrodesis.

CONTRAINDICATIONS

Absolute contraindications include localized soft-tissue infection and severe degenerative joint disease. Relative contraindications consist of severe pedal edema, moderate degenerate joint disease, poor vascular status, and poor skin condition.

TECHNIQUE

The subtalar joint has limited space and limited capacity for distraction. Therefore, special instruments must be available to avoid iatrogenic articular cartilage injury and to allow adequate visualization and instrumentation of the joint. A 1.9-, 2.7-, or 2.9-mm 30-degree scope is generally selected. The 4-mm scope is generally reserved for posterior subtalar arthroscopy. We use the 1.9-mm scope. The 70-degree scope has been recommended in some situations but we have no experience with this. Smaller arthroscopic instruments such as the 1.5-mm arthroscopic probe and 2.0- and 2.9-mm shavers are required. Small, short-handled curved and straight curettes and osteotomes should be available. The use of invasive or noninvasive distractors has been advocated by some surgeons. Generally, an arthroscopic pump is not required and a simple gravity system is used.

Positioning the patient on the operative table is partly based on technique, surgeon preference, and concomitant procedures to be performed. The lateral decubitus position allows for direct access to the subtalar joint via a lateral approach. Arthroscopy of the ankle joint is also feasible in this position if required. The supine position also permits arthroscopy of the ankle joint on conjunction with the subtalar joint. The use of noninvasive traction is somewhat easier in this position. The portals are somewhat more challenging to work through in our experience. The prone position reserved for the posterior approach to subtalar arthroscopy.

The tight constraint of the subtalar joint has led some to use distraction. There is an option to use a noninvasive distractor or invasive traction. The noninvasive distractor fits onto the operative table and around the foot with a sterile stirrup strap. A femoral distractor or different external fixator may be used to distract the joint. The disadvantage of using invasive joint distraction is the risk of fracturing the talar neck or body, infection, and damage to soft-tissues including ligamentous structures. The distractor position should allow free motion of the scope and instruments. Subtalar joint distraction is limited by the strong supporting ligamentous structures regardless of the technique used. We have not found distraction helpful.

Arthroscopic Technique

The bony anatomy, Achilles tendon, superficial peroneal nerve, sural nerve, and dorsalis pedis neurovascular bundle should also be outlined on the skin. Regardless of the portals used, the arthroscopic visualization of the subtalar joint is limited to the posterior facet. Ligaments within the sinus tarsi make the anterior portion of the subtalar joint inaccessible. Access to the posterior facet of the subtalar joint can be achieved via a lateral or posterior approach.

Lateral Subtalar Arthroscopy

The lateral approach uses three arthroscopic portals for visualization and instrumentation of the posterior facet. The locations of the portals are drawn on the skin in FIGURE 25-1 . The portal locations in relation to neurovascular and deeper anatomy are depicted in FIGURE 25-2 .

The posterolateral portal is positioned in the palpable soft-spot lateral to the Achilles tendon slightly proximal to the level of the tip of the fibula. This portal is similar to the skin incision made for the posterolateral portal used in ankle arthroscopy. A cadaveric study by Frey et al. showed that this portal posed the greatest risk of nerve or vessel damage. The sural nerve, small saphenous vein, and peroneal tendons may be damaged. The sural nerve usually lies 4 mm anterior to the portal.

The middle or central portal is made just inferior to the tip of the lateral malleolus and approximately 1 cm anterior. This portal essentially lies over the sinus tarsi. The position of this portal placed no structures at risk in cadaveric assessment. The arthroscopic picture seen in FIGURE 25-3 was taken from the central portal.