Foot & Ankle

Isolated subtalar arthritis can result from:

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• Trauma (calcaneal/talus fractures)

• Primary osteoarthritis (instability/deformity)

• Symptomatic residual congenital deformity (talocalcaneal coalition)

• Tibialis posterior tendon dysfunction (Adult Acquired Flatfoot Deformity)

• Inflammatory arthritis isolated to the subtalar joint

 

In a review of subtalar arthrodesis, Davies et al. reported on 92 patients with 95 feet requiring fusion, and the aetiology included with 67% post-traumatic arthritis, 23% primary osteoarthrosis, 5.3% tarsal coalition, and 4.2% inflammatory arthropathy.

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Anatomic variations of the sustentaculum tali may predispose to long-term instability and lead to subtalar arthritis. A cadaveric study by Drayer-Verhagen assessed the morphology of sustentaculum tali and associated arthritis found significantly higher rates of arthritis in specimens with long continuous facets (65%) and medial only facets (50%) when compared to separate anterior and medial facets (35%).

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Classification

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• Stage 1 - Presence of osteophytes without joint-space narrowing

• Stage 2 - Joint-space narrowing with or without osteophytes

• Stage 3 - Subtotal or total disappearance or deformation of joint space

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Clinical Presentation

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Patients often present with pain, swelling and stiffness of the foot, aggravated by weight-bearing, especially on uneven grounds and often get better with rest or by wearing high-top shoes. Pain is often felt in the lateral hindfoot and may be associated with instability, catching, or locking sensation.

Specific findings to the subtalar joint include hindfoot swelling, tenderness within the sinus tarsi, pain with inversion/eversion of the hindfoot, limited range of motion of the subtalar joint and an antalgic gait. The heel cord and gastrocnemius should be evaluated for tightness.

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Imaging

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Weight-bearing radiographs are essential to accurately assess alignment and the degree of degenerative changes (AP, oblique, and lateral radiographs of the foot and ankle).

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Additional radiographs may include:

Broden’s view (internally rotated 45 degrees; X-ray angled 10-40 degrees cephalad) to evaluate the posterior subtalar facet

Canale view (AP view of foot in 15 degrees of pronation with X-ray aimed 75 degrees from horizontal) to evaluate the sinus tarsi

 

CT and/or MRI may be necessary to evaluate for avascular necrosis or subtle arthritic changes.

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Treatment

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Conservative Treatment

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Always the first line of management in symptomatic patients and modalities include:

• Analgesia

• Physiotherapy (for range of motion, strengthening, and proprioception)

• Activity modification

• Braces (to limit painful joint motion, accommodate rigid deformity, correct flexible deformity)

• Shoe modifications

• Orthotics

 

Subtalar injections

 

Injections can be a valuable diagnostic tool, but there is little literature to support therapeutic treatment with corticosteroid. Peterson et al. in a review article, found a significant improvement in pain and motion for up to 6 months following a corticosteroid injections.

 

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Surgical Treatment

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Subtalar arthrodesis is indicated for pain, instability, residual coalition and deformity of the talocalcaneal joint that has failed conservative treatment. In trauma patients, subtalar arthrodesis is a common salvage operation for posttraumatic subtalar arthritis, mainly caused by calcaneal or talar fractures.

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It is considered superior to double or triple arthrodesis with regards to preservation of motion at the talonavicular and calcaneocuboid joints. The primary goals of surgery are to achieve pain relief and improve function by restoring hindfoot alignment.

 

The traditional approach is by open technique however arthroscopic joint preparation is gaining popularity in selected patients. The gold-standard option for fixation is by the use of screws however staples are also used.

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Some authors prefer the single screw technique, but this configuration may not be adequate in all situations as rotation cannot be controlled with one point of fixation. Single lag screw placement from posteroinferior calcaneus to anterior talar neck is effective for subtalar fusion. No significant differences have been observed in union rate, postoperative complication incidence, or subsequent surgeries when comparing single-screw to two-screw fixation of isolated subtalar fusions.

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Biomechanically, the double diverging two-screw configuration has been shown to achieve the most compression and torsional stiffness and the least joint rotation. Regardless of the number, size or directionality (calcaneotalar or talocalcaneal) of the lag screw in fixation, union rates ranging from 86% to 100% have been reported.

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Easley et al. in a retrospective review of 148 patients reported an overall union rate of 86% after an isolated subtalar arthrodesis, with an average age of 43 years, average follow up of 51 months and 80 patients being smokers. Union rates were 84% after primary arthrodesis and 71% after revision arthrodesis, 92% in non-smokers and 73% in smokers. Complications included prominent hardware requiring screw removal (20%), lateral impingement (10%), symptomatic valgus malalignment (3%), symptomatic varus malalignment (3%), and infection (3%).

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Hollman et al. in a retrospective review reported the outcomes of 40 patients who underwent subtalar fusion for post-traumatic arthritis. Of these, 90% patients stated that they would recommend the procedure to others, walking abilities improved in 69% and pain improved in 76%.

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A recently published level IV evidence compared subtalar fusion with and without bone graft (autograft, allograft, bone substitutes) and did not find any significant differences in the union rates. In fact the union rates were found slightly better in the group without bone graft (88% vs 83%).

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Haskell et al. in a retrospective review of 101 subtalar arthrodesis, reported a union rate of 98% using a single lag screw and local autograft, with an average age of 52 years and 7 revision fusions. Prior ankle fusion, smoking and revision fusion were strong predictive factors to delay the time to union.

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Arthroscopic subtalar arthrodesis is gaining popularity based on evidence of union in over 90% of cases, with a shorter time to healing, a simpler postoperative course, and fewer complications compared to open technique. However, it is fraught with potential difficulties of identifying the subtalar joint (especially with previous deformity), accessing the whole joint for preparation and surgeon’s learning curve.

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