Introduction

In 2000, a 2-portal posterior approach for hindfoot arthroscopy was described. This approach was successfully used for arthroscopic subtalar arthrodesis in a series of patients with post-traumatic osteoarthritis.

Painful talocalcaneal coalition is a recognized indication for talocalcaneal arthrodesis in skeletally mature patients. A talocalcaneal coalition is a congenital osteofibrous, cartilaginous, or osseous union of the talus and calcaneus. A talocalcaneal coalition ossifies either completely or incompletely between 12 and 16 years of age. The presence of a talocalcaneal coalition presents a technical challenge since the bar only allows limited opening up of the joint during surgery. As standard arthroscopic techniques for subtalar arthrodesis do not provide means of opening up the joint, they are difficult to use in patients with limited subtalar joint space.

Therefore, an accessory posterolateral portal for introduction of a blunt trocar for subtalar joint distraction in arthroscopic subtalar joint arthrodesis was described.
However, the working space in the hindfoot is significantly reduced by using three posterior portals in the hindfoot. We present a technique for arthroscopic subtalar arthrodesis based on the 2-portal posterior approach with the patient in the prone position. Via an accessory third working portal at the level of the sinus tarsi, a large diameter blunt trocar is introduced in order to provide subtalar joint opening. The sinus tarsi portal is also used for introduction of ring curettes in order to remove cartilage of the anterior part of the posterior talocalcaneal joint.

Anatomy

A functional subtalar joint consists of an anterior, middle and posterior facet.

In case of a talocalcaneal coalition, the middle facet is predominantly involved. Limited movement between two or more bones of the subtalar joint complex leads to excessive stress in the hindfoot joint, thereby causing painful inflammations and premature bone degeneration. Congenital coalitions appear to represent a failure of rpimitive mesenchymal differentiation, the mode of inheritance is thought to be autosomal dominant. Some coalitions may resolve spontaneously during childhood due to weight-bearing biomechanics. In general, timing of onset of symptoms is explained by ossification of the cartilaginous coalition, at around 12 to 16 years of age.

History & Physical Examination

On history taking and physical examination a differentiation should be made between patients with posttraumatic osteoarthritis of the subtalar joint or patients with a talocalcaneal coalition.

Painful talocalcaneal coalition is a recognized indication for talocalcaneal arthrodesis in skeletally mature patients. A talocalcaneal coalition is a congenital osteofibrous, cartilaginous, or osseous union of the talus and calcaneus. A talocalcaneal coalition ossifies either completely or incompletely between 12 and 16 years of age 46. This is when the abnormality usually becomes symptomatic. Patients usually present with non-specific hindfoot pain. A forceful inversion trauma of the ankle may elicit complaints and history may reveal repeated ankle sprains.

Patients with posttraumatic (e.g. calcaneal fracture, chronic instability after inversion trauma(s)) osteoarthritis of the subtalar joint complain of chronic deep ankle pain and swelling, months to years after a trauma. Morning stiffness, night pain and starting pain may be present. In patients with a talocalcaneal coalition this pain may also occur after trauma, but in many cases the complaints develop spontaneously. Some patients report a limited range of motion.

On physical examination there may be abnormal gait and swelling over the subtalar joint. In- and/ or eversion are diminished or absent. Subtalar deformity should be ruled out since it is a contraindication for arthroscopic arthrodesis. In talocalcaneal coalitions hindfoot valgus is seen. A lump may be palpable under the tip of the medial malleolus indicating a prominence of the talocalcaneal coalition. The coalition itself may be painful to pressure, specifically after a recent ankle trauma. A tarsal tunnel syndrome may develop due to a large middle facet resulting in increased pressure on the median plantar nerve. Relative contraindications include severe oedema, poor skin quality, and poor vascular status. Signs of infection leading to a potential septic joint should also be carefully assessed.

Diagnostic Imaging

Conventional Radiography

Conventional weight- bearing anteroposterior and lateral radiographs can be made. In case of subtalar osteoarthritis, sclerotic bone, osteophytes, joint space narrowing, and possibly bone cysts can be expected.

The C-sign is a reliable diagnostic criterion for talocalcaneal coalition. This is a C-shaped line formed by the medial outline of the talar dome and the inferior outline of the sustentaculum tali on lateral radiographs of the ankle.

Additional Investigation 

To confirm diagnosis and for pre-operative planning (e.g. location of the coalition), a CT-scan can be made.

Surgical Treatment

Indications

Conservative treatment is the first treatment of choice. Conservative treatment of mild to moderate subtalar osteoarthritis or a talocalcaneal barr evolves around supportive measures to decrease the impact loading to the hindfoot as well as to limit the imposed range of motion in this region during normal activities. Placement of cushioned heels in the shoes to diminish loading of the hindfoot during heel strike can be helpful. Braces that limit in- and eversion of the hindfoot may also be beneficial.

These measures are often not sufficient in the sportsactive, nor in patients with severe osteoarthritis. In these cases, and in cases where pain persists after maximum conservative treatment, surgical treatment is indicated.

Contra- indications

An absolute contra- indication for isolated arthroscopic subtalar arthrodesis is degenerative changes in the surrounding ankle, talonavicular and calcaneocuboid joint. Significant angular or rotatory deformity in the talocalcaneal joint and signisifcant bone loss are also contra- indications. One should also be careful considering this procedure for a diabetic or patients with cardiovascular disease, although the risks of complications are reduced as compared to the open procedure. 

Post- operative Rehabilitation Protocol

A non-weightbearing lower leg cast is provided for 4-6 weeks, followed by a walker boot for another 4-6 weeks. At 4-6 weeks following surgery, anteroposterior and lateral weightbearing ankle radiographs are made. With radiographic signs of union of the subtalar arthrodesis, the patient is allowed full weightbearing in the walker booth. 

Recommended literature

Van Dijk CN, Fievez AWFM, Heijboer MP, et al. Arthroscopy of the ankle. Acta Orthop Scand 1993;64(suppl. 253):9.

Van Dijk CN, Scholte D. Arthoscopy of the Ankle Joint. Arthroscopy: The journal of Arthroscopic and Related Surgery, 1997;13(1):90-96.

Van Dijk, Verhagen RAW, Tol JL. Arthroscopy for problems after ankle fracture. J Bone Joint Surg (Br) 1997;79B(2):280-284.