Michael M. Romash
DEFINITION
An isolated subtalar arthrodesis can be used in the treatment of a myriad of different hindfoot conditions, including primary arthrosis of the subtalar joint, posttraumatic arthritis secondary to a talar or complex calcaneal fracture, rheumatoid arthritis, and talocalcaneal coalition.
Other indications include posterior tibial tendon insufficiency and any neuromuscular disorder presenting with instability of the subtalar joint.
When the pathologic process resides solely in the talocalcaneal articulation, isolated subtalar arthrodesis is preferred over a triple arthrodesis for its preservation of hindfoot motion, its decreased potential for development of degenerative changes in neighboring joints, its relative simplicity, and its lower potential for pseudarthrosis of the talonavicular and calcaneocuboid joints.
ANATOMY
The term subtalar refers to the articulation between the anterior, middle, and posterior facets of the inferior talus and the corresponding anterior, middle, and posterior facets located on the superior aspect of the calcaneus.
The subtalar joint is a “plane type” synovial joint with a weak fibrous capsule supported by medial, lateral, and posterior talocalcaneal ligaments, as well as an interosseous talocalcaneal ligament.
This important articulation provides for inversion and eversion of the hindfoot, which is critical for proper adaptation of the foot during ambulation on uneven terrain and for dissipation of heel strike forces.
Isolated fusions of the subtalar joint have been shown to reduce talonavicular joint motion by 74% and calcaneocuboid joint motion by 44%.1
PATHOGENESIS
Numerous causes of subtalar joint arthritis exist, including:
Primary osteoarthrosis: articular cartilage degeneration of unknown etiology
Secondary arthritis: caused by either traumatic articular cartilage damage or increased joint stresses following an arthrodesis of an adjacent joint
Inflammatory arthritis: autoimmune joint destruction (eg, rheumatoid arthritis, psoriatic arthritis)
Other etiologies that may necessitate an isolated subtalar arthrodesis include:
Talocalcaneal coalition: abnormal fusion between the talus and calcaneus, most likely secondary to a failure of segmentation of the primitive mesenchyme
Instability or deformity secondary to muscular imbalance (eg, posterior tibial tendon insufficiency, Charcot-Marie-Tooth disease, poliomyelitis)
NATURAL HISTORY
Depends on specific etiology
In general, the various forms of subtalar arthritis are progressive in nature.
Despite waxing and waning of symptoms, no spontaneous resolution of the pathologic process is noted.
PATIENT HISTORY AND PHYSICAL FINDINGS
A problem-focused history should include direct questioning regarding the exact nature of the symptoms, specific location, duration and progression of symptoms, aggravating or alleviating factors, prior therapeutic interventions, and functional disability.
Patients often complain of lateral ankle pain and difficulty ambulating on uneven terrain.
The pain often gets better with rest and may be mitigated by wearing high-top shoes.
Physical examination findings consistent with subtalar joint arthritis may include:
Hindfoot swelling
Tenderness within the sinus tarsi
Pain with inversion and eversion of the hindfoot
Limited range of motion of the subtalar joint
Antalgic gait
To help localize the pathology to the subtalar joint complex, palpate and observe the sinus tarsi (the soft tissue depression just anterior and slightly distal to lateral malleolus) for swelling.
Passively dorsiflex the ankle to neutral to lock the talus within the mortise. Descriptions of normal subtalar range of motion vary widely. Therefore, it is useful to describe the range as a fraction of the asymptomatic, contralateral side. Pain and decreased range of motion may be indicative of subtalar joint arthritis. Complete loss of range of motion is consistent with a tarsal coalition.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiographs should include standing AP, lateral, and oblique views of the foot, and standing AP, lateral, and mortise views of the ankle.
Additional plain radiographs may include a Broden's view (lower extremity internally rotated 45 degrees; x-ray tube angled 10 to 40 degrees cephalad) to evaluate the posterior subtalar facet, and a Canale view (AP view of the foot in 15 degrees of pronation with tube angled 75 degrees from the horizontal) to evaluate the sinus tarsi.
Radiographic findings consistent with a degenerative process include joint space narrowing, osteophytes, and subchondral cysts or sclerosis (FIG 1).
FIG 1 • Posttraumatic arthritis of the subtalar joint. Note the narrowing of the joint space, subchondral sclerosis, subchondral cysts, and osteophyte formation.
Computed tomography and magnetic resonance imaging offer little additional information about the arthritic process involving the subtalar joint, but they may identify a previously undiagnosed tarsal coalition or concomitant soft tissue pathology.
A diagnostic injection of a local anesthetic into the subtalar joint may help localize the patient's complaints, and if a corticosteroid is added to the injection, this procedure may provide significant short-term relief.
DIFFERENTIAL DIAGNOSIS
Primary osteoarthrosis
Posttraumatic arthritis
Inflammatory arthritis
Acute fracture
Sinus tarsi syndrome
Instability of the subtalar joint or subtalar sprain
Fibrous or cartilaginous talocalcaneal coalition
Subtalar loose body
NONOPERATIVE MANAGEMENT
Subtalar joint arthritis is initially managed nonoperatively in all patients.
Nonoperative management strategies may include:
Activity modification
Nonsteroidal anti-inflammatory medications
Intra-articular corticosteroid injection
Use of an ankle–foot orthosis or UCBL orthosis to limit hindfoot motion. Other options include an air stirrup or high-top boot.
Patellar tendon–bearing brace to unload the subtalar joint
Conservative treatment may also be indicated in patients with significant peripheral vascular disease, active infection, inability to comply with the postoperative regimen, or a severe sensory neuropathy.
SURGICAL MANAGEMENT
For patients who do not achieve relief with an adequate trial of nonoperative management, surgical intervention is warranted.
Preoperative Planning
Plain radiographs are reviewed for deformity or malalignment, loose bodies, or retained hardware from a prior surgery.
Computed tomographic or magnetic resonance imaging scans are reviewed, if available.
Positioning
The patient is placed supine on the operative table, and the sole of the foot is aligned with the end of the bed to facilitate later screw insertion into the heel.
A pneumatic tourniquet is placed around the upper thigh, and a soft bump is placed beneath the ipsilateral sacrum to internally rotate the operative extremity. Placement of the bump beneath the sacrum, rather than beneath the buttock, will prevent any undue pressure on the sciatic nerve.
The fluoroscopy unit is brought in from the contralateral side of the bed.
Approach
A tourniquet is elevated to a pressure of 100 mm Hg greater than the patient's systolic pressure.
The incision begins approximately 1 cm below the tip of the lateral malleolus and progresses distally to a point just shy of the base of the fourth metatarsal (FIG 2A). Alternatively, a modified Ollier incision may be used.
The subcutaneous tissue is incised in line with the skin incision, and preemptive hemostasis of any crossing vessels is performed using electrocautery.
The origin of the extensor digitorum brevis muscle is identified and elevated along with the sinus tarsi fat pad as a distally based flap. A small cuff of tissue is preserved proximally for later reattachment of this flap (FIG 2B,C).
At this point, the subtalar joint is well visualized.
FIG 2 • Surgical approach. A. Incision. B. Exposure of the extensor digitorum brevis muscle, sinus tarsi fat pad, and peroneal tendons. C. Elevation of extensor digitorum brevis and sinus tarsi fat pad as a distally based flap.
TECHNIQUES
PREPARATION OF THE ARTHRODESIS SITE
After adequate visualization of the lateral aspect of the subtalar joint has been attained, any remaining fatty or ligamentous tissue is removed from the joint with a rongeur (TECH FIG 1A).
Using a straight curette or chisel, the articular cartilage is removed from the lateral half of the inferior talus and superior aspect of the calcaneal facets (TECH FIG 1B). Note that the goal is to maintain the normal, curved contours of the articular facets.
A lamina spreader is then inserted to allow access to the medial half of the joint, which is then cleared of its articular cartilage using a combination of straight and curved currettes (TECH FIG 1C).
After complete removal of all articular cartilage, K-wire holes are created in the denuded inferior surface of the talus and the superior surface of the calcaneus to produce vascular channels that will aid in the fusion (TECH FIG 1D). These K-wire holes may be further augmented with larger holes created through the use of a 3-mm burr, and by feathering of the subchondral bone with a curved osteotome.
Cancellous autograft obtained from the proximal tibia (see Techniques) is inserted into the subtalar joint, and the extensor digitorum brevis muscle is reattached to its site of origin to help seal the fusion site (TECH FIG 1E).
TECH FIG 1 • Preparation of the arthrodesis site. A. Removal of soft tissues from the subtalar joint. B. Removal of the lateral articular cartilage with a curette. C. Insertion of a lamina spreader and removal of the remaining medial articular cartilage. D. Creation of vascular channels with a K-wire. E. Reattachment of the extensor digitorum brevis to its origin after insertion of a tibial bone graft.
INSERTION OF HARDWARE
At this point, the subtalar joint is positioned into 5 degrees of valgus.
A 1-cm incision is created at the apex of the heel for insertion of a guide pin, which is subsequently driven through the posterior tuberosity, across the subtalar joint, and into the talar neck (TECH FIG 2A). This guide pin is placed fluoroscopically using axial (Harris) heel and lateral views.
A second guide pin is placed through a 1-cm incision just medial to the anterior tibialis tendon into the dorsomedial aspect of the talar neck, across the subtalar joint, and into the posterior calcaneal tuberosity (TECH FIG 2B).
The initial guide pin is occasionally overreamed proximally (not necessary with self-drilling, self-tapping screws), and a 6.5-mm partially threaded cancellous lag screw of an appropriate length is inserted after minimal use of the cannulated countersink. This procedure is repeated for the dorsomedial lag screw.
Final fluoroscopic images are obtained to verify proper screw position (TECH FIG 2C).
TECH FIG 2 • Internal fixation A. Placement of the first guide pin and screw from the apex of the calcaneal tuberosity. B. Placement of the second guide pin and screw from the dorsomedial aspect of the talar neck. C. Final fluoroscopic images.
WOUND CLOSURE
The tourniquet is released and hemostasis is secured.
The wound is then closed using 2-0 Vicryl for the subcuticular layer and 3-0 nylon horizontal mattress sutures for the skin.
HARVESTING OF TIBIAL BONE GRAFT
An incision beginning 1 cm distal to the distal aspect of the tibial tubercle and 1 cm lateral to the anterior tibial crest is carried distally for a length of 4 cm (TECH FIG 3A).
The fascia overlying the anterior compartment musculature is divided in line with the skin incision.
Muscle and periosteum overlying the anterolateral face of the tibia is elevated using a periosteal elevator, thus exposing the anterolateral cortex (TECH FIG 3B).
A 1 by 1–cm square (or elliptical) window is created in the center of the anterolateral face, and a curette is inserted into the window for removal of cancellous graft (TECH FIG 3C,D).
After an adequate amount of cancellous graft is harvested, the window is sealed with the previously removed square plug of bone, and a layered closure of the fascia, subcutaneous tissue, and skin is performed.
Time from graft harvest to insertion into the fusion site should be less than 30 minutes.
TECH FIG 3 • Harvesting of the tibial bone graft. A. Incision. B. Periosteal elevation along the anterolateral cortex. C. Creation of a 1 by 1–cm square window. D. Removal of the cancellous autograft with a curette.
POSTOPERATIVE CARE
The extremity is placed in a well-padded, non–weight-bearing short leg plaster cast before the patient leaves the operating room.
In the recovery room, the cast is widely split along its anterior surface to allow for immediate postoperative swelling.
The patient is seen in clinic at 2 weeks postoperatively, at which point the initial cast and sutures are removed.
A short leg fiberglass cast is applied and the patient is kept non–weight-bearing.
At the 6-week mark, radiographs are obtained, and the patient is converted to a fiberglass short leg walking cast.
If radiographic union is appreciated at the 12-week appointment, casting is discontinued and gentle range of motion of the foot and ankle is initiated. At this point, the patient is often placed in a CAM walker to ease the transition from the cast to normal shoe wear.
OUTCOMES
At an average of nearly 5 years' follow-up, Mann et al reported a 93% satisfaction rate with isolated subtalar arthrodesis.12
In another study by Mann and Baumgarten, subtalar joint fusion in 6 degrees of valgus resulted in the maintainence of approximately 50% of the transverse tarsal joint motion as compared with the unaffected, contralateral extremity. In this same study, minimal degenerative changes were noted at the talonavicular and calcaneocuboid joints, a finding that was not clinically significant.11
In a retrospective study, Dahm and Kitaoka demonstrated a 96% union rate in 25 adult feet.3
Similarly, Easley et al demonstrated a 96% subtalar fusion rate after excluding smokers, revision arthrodeses, fusions using a structural graft, and subtalar fusions performed in an extremity with a previously fused tibiotalar joint.4
COMPLICATIONS
Infection8
Nonunion4,7,10
Malalignment
Varus leading to increased lateral column forefoot pressures6,10
Valgus leading to subfibular impingement6,10
Symptomatic hardware4
Superficial wound breakdown2
Reflex sympathetic dystrophy5
REFERENCES
· Astion DJ, Deland JT, Otis JC, Kenneally S. Motion of the hindfoot after simulated arthrodesis. J Bone Joint Surg Am 1997;79A:241–246.
· Chandler JT, Bonar SK, Anderson RB, Davis WH. Results of in situ subtalar arthrodesis for late sequelae of calcaneus fractures. Foot Ankle Int 1999;20:18–24.
· Dahm DL, Kitaoka HB. Subtalar arthrodesis with internal compression for posttraumatic arthritis. J Bone Joint Surg Br 1998;80B: 134–138.
· Easley ME, Trnka H-J, Schon LC, Myerson MS. Isolated subtalar arthrodesis. J Bone Joint Surg Am 2000;82A:613–624.
· Flemister AS, Infante AF, Sanders RW, Walling AK. Subtalar arthrodesis for complications of intra-articular calcaneal fractures. Foot Ankle Int 2000;21:392–399.
· Kile TA, Bouchard M. Degenerative joint disease of the ankle and hindfoot. In: Thordarson DB, ed. Orthopaedic Surgery Essentials: Foot and Ankle. Philadelphia: Lippincott Williams & Wilkins, 2004: 195–220.
· Kitaoka HB. Talocalcaneal (subtalar) arthrodesis. In: Kitaoka HB, ed. Master Techniques in Orthopaedic Surgery: The Foot and Ankle, ed 2. Philadelphia: Lippincott Williams & Wilkins, 2002:387–399.
· Lin SS, Shereff MJ. Talocalcaneal arthrodesis: a moldable bone grafting technique. Foot Ankle Clin 1996;1:109–131.
· Lippert FG, Hansen ST. Subtalar arthrodesis. In Lippert FG, Hansen ST, eds. Foot Ankle Disorders: Tricks of the Trade. New York: Thieme, 2003:133–139.
· Mann RA. Arthrodesis of the foot and ankle. In: Coughlin MJ, Mann RA, eds. Surgery of the Foot and Ankle, ed 7. St Louis: Mosby, 1999: 651–699.
· Mann RA, Baumgarten M. Subtalar fusion for isolated subtalar disorders: preliminary report. Clin Orthop Rel Res 1988;226:260–265.
· Mann RA, Beaman DN, Horton GA. Isolated subtalar arthrodesis. Foot Ankle Int 1998;19:511–519.