Clifford L. Jeng
DEFINITION
Severe rigid planovalgus foot deformity may be a result of multiple underlying causes.
In longstanding rigid hindfoot valgus deformities, the lateral skin and soft tissues may become severely contracted. In these cases, adequate correction of a severe valgus deformity may stretch and compromise the lateral soft tissues if a standard two-incision approach is used for triple arthrodesis.
Previous surgical incisions, soft tissue injuries, or infections may further compromise wound healing if a lateral incision is used.
A single-medial-approach triple arthrodesis technique offers adequate exposure of the subtalar, talonavicular, and calcaneocuboid joints for preparation without putting the lateral skin at risk.
ANATOMY
The posterior and middle facets of the subtalar joint lie directly deep to the excised posterior tibial tendon (FIG 1).
The flexor digitorum longus tendon and the posterior tibial neurovascular bundle lie just posterior and plantar to the subtalar joint. These must be protected with a retractor during joint preparation.
The talonavicular joint is easily accessible through the extensile medial approach.
The calcaneocuboid joint is directly lateral to the talonavicular joint across the foot. It can be adequately accessed through the extensile medial incision after the talonavicular joint is distracted with a lamina spreader (FIG 2).
PATHOGENESIS
The medial longitudinal arch is supported by both static and dynamic anatomic structures.
The static component includes the spring ligament (calcaneonavicular ligament), the plantar fascia, and the long plantar ligament.
FIG 1 • The subtalar joint lies directly beneath the excised posterior tibial tendon.
The dynamic component includes the posterior tibial tendon.
In the adult acquired flatfoot, the spring ligament, plantar fascia, and long plantar ligament become attenuated and the posterior tibial tendon becomes dysfunctional. It is controversial whether the static or dynamic stabilizers fail first.
In severe flatfoot patients, the peroneal tendons and the laterally shifted Achilles tendon overpower the dysfunctional posterior tibial tendon, forcing the subtalar joint into heel valgus.
The transverse tarsal joints (talonavicular and calcaneocuboid joints) are abducted by the relative overpull of the peroneus brevis, causing lateral subluxation of the talonavicular joint and uncovering of the talar head.
NATURAL HISTORY
Severe hindfoot valgus deformity, if left untreated, may lead to gradual attenuation of the deltoid ligament. Once this occurs, the tibiotalar joint becomes incongruent and tilts into valgus. This will eventually lead to ankle joint arthritis.
The association of severe hindfoot valgus and valgus tilt of the ankle is difficult to treat and generally requires either (1) a pantalar arthrodesis or (2) ankle arthroplasty with an underlying triple arthrodesis.
In my opinion, it is critical to intervene in these patients with severe hindfoot valgus before the deltoid ligament becomes incompetent in order to preserve the ankle joint.
PATIENT HISTORY AND PHYSICAL FINDINGS
While a single-incision medial triple arthrodesis is feasible in most patients recommended for triple arthrodesis, we favor employing this technique in the most severe cases of hindfoot valgus or in high-risk patients.
Risk factors exist that may predispose to severe pes planovalgus or may put the patient at risk for wound healing complications. Rheumatoid arthritis is a common cause of severe hindfoot valgus. Rheumatoid patients can sometimes present with greater than 30 degrees of valgus through the subtalar joint. Many of these patients will have gross subluxation of the posterior facet of the subtalar joint on radiographs.
FIG 2 • View of the calcaneocuboid joint from the medial approach.
Likewise, diabetic patients with Charcot-like subtalar joint subluxation or dislocation may present with severe hindfoot valgus. These patients are at increased risk of wound healing complications, and in our opinion represent patients in whom a lateral sinus tarsi approach is not advised.
Anyone with a history of previous soft tissue trauma laterally, open wounds, active infection, or recent surgical incisions that may compromise the ability of a lateral sinus tarsi incision to heal may benefit from a single-medial-incision technique.
Examination should include the following:
Standing hindfoot alignment. The examiner should visually inspect the posterior heel alignment with respect to the tibia with the patient standing. Physiologic hindfoot valgus is usually 5 to 7 degrees. Significantly greater valgus may be pathologic. In patients with severe hindfoot valgus greater than 30 degrees, a lateral sinus tarsi incision may be difficult to heal once the heel is reduced.
Subtalar range of motion. The examiner should maximally invert and evert the heel to determine the range of motion with respect to the tibial axis. Normal subtalar range of motion is 5 degrees of eversion and 20 degrees of inversion. Most severe, longstanding pes planovalgus deformities will be rigid. If the hindfoot is flexible, the surgeon may consider osteotomies or lateral column lengthening to correct the malalignment.
Peroneal tendon contracture. With the heel maximally inverted, the examiner should palpate the peroneal tendons to determine how much they are contributing to valgus contracture. If the peroneal tendons are excessively tight, they will need to be released for the heel alignment to be corrected to neutral.
Contracture of the skin overlying the lateral hindfoot. The examiner should visually inspect the lateral skin to see whether it is loose or taut. If the lateral skin is tight before correcting the heel valgus, a sinus tarsi incision will be very difficult to close once the heel is neutral.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Standard weight-bearing radiographs of both the foot and ankle are critical in evaluating severe pes planovalgus deformities. The foot films will determine the amount of subluxation or dislocation of the subtalar and transverse tarsal joints that must be corrected. They can also determine whether there is deformity or bone loss that demands the addition of structural bone grafts. The ankle radiographs are required to confirm that the severe heel valgus is isolated to the hindfoot. Occasionally, severe valgus hindfoot deformity leads to increasing deltoid ligament incompetence, creating a valgus tilt of the talus within the ankle mortise. Deltoid ligament incompetence and valgus tilt of the ankle may necessitate surgical correction of the ankle as well should hindfoot realignment with triple arthrodesis fail to rebalance the tibiotalar joint (FIG 3).
DIFFERENTIAL DIAGNOSIS
The possible underlying causes of flatfoot in an adult include:
Posterior tibial tendon dysfunction
Inflammatory arthritis
FIG 3 • Radiographs of a 56-year-old diabetic woman with severe pes planovalgus deformity and gross subluxation of the subtalar and transverse tarsal joints radiographically.
Osteoarthritis
Calcaneus fracture
Navicular fracture
Spring ligament rupture
Lisfranc fracture-dislocation
Crush injury
Tarsal coalition
Accessory navicular
Charcot neuroarthropathy
Cerebral palsy
Poliomyelitis
Nerve injury
Longstanding idiopathic flatfoot
NONOPERATIVE MANAGEMENT
In patients with longstanding pes planovalgus feet, the deformity is frequently fixed, meaning that the deformity cannot be actively or passively corrected. Orthotics and braces can only help by supporting the arch, unloading prominences, or immobilizing arthritic joints. Several over-the-counter braces are available commercially that may be effective in immobilizing and supporting the painful flatfoot. The gold standard is a custom-made relatively rigid lace-up ankle brace. In-shoe orthotics for rigid flatfeet should be custom-molded to accommodate the deformity and any prominences.
Nonsteroidal anti-inflammatory medications may be helpful in alleviating arthritic pain or synovitis. Occasionally a cortisone shot may be beneficial to relieve an acutely painful joint.
SURGICAL MANAGEMENT
Positioning
The patient is positioned supine on the operating table with a small bump beneath the contralateral hip. This places the operative foot nearly parallel to the table, which is critical because all of the exposure and preparation will be performed through the medial incision. A well-padded thigh tourniquet is placed on the proximal thigh.
Approach
An extensile medial incision affords satisfactory exposure to the talonavicular and subtalar joints. With talonavicular joint distraction, the calcaneocuboid joint may also be accessed.
TECHNIQUES
RELEASE OF THE PERONEAL TENDON CONTRACTURE
Make a 3-cm longitudinal incision posterolaterally about 10 cm above the level of the ankle joint. This incision is made directly over the peroneal tendons, immediately behind the posterior border of the fibula.
Open the peroneal tendon sheath longitudinally in line with the skin incision.
Use a hemostat to remove the peroneus longus and brevis tendons from their sheath. Transect each tendon completely and return them into the sheath (TECH FIG 1).
Close the sheath and skin in layers.
TECH FIG 1 • The peroneus longus and brevis contractures are released through a small incision well above the level of the ankle joint to avoid wound complications.
EXPOSURE AND PREPARATION OF SUBTALAR JOINT
Make an extensile longitudinal incision medially from the tip of the medial malleolus to the tarsometatarsal joint level.
Open the sheath of the posterior tibial tendon longitudinally in line with the skin incision.
Completely release the posterior tibial tendon from its insertion onto the navicular. Use a Köcher clamp to pull out the tendon as far as possible, and excise the posterior tibial tendon proximally in the incision (TECH FIG 2).
Using a retractor, pull the flexor digitorum longus tendon posteriorly. This will protect the posterior tibial neurovascular bundle behind it.
Use a scalpel blade to localize the posterior and middle facets of the subtalar joint by probing deep to the excised posterior tibial tendon. Once the joint is identified, use an osteotome or elevator to release the joint capsule and ligaments (TECH FIG 3).
Insert a lamina spreader between the talar neck and calcaneus and open it to expose the subtalar joint for preparation (TECH FIG 4).
Using a combination of osteotomes and curettes, remove all remaining articular cartilage from the joint down to the subchondral plate.
Use a curved osteotome to aggressively “feather” the articular surfaces of the posterior and middle facets of the subtalar joint, creating increased surface area for fusion and serving to provide local bone graft.
TECH FIG 2 • The posterior tibial tendon is detached from its insertion on the navicular and excised to expose the underlying subtalar joint.
TECH FIG 3 • A scalpel or osteotome is used to identify the subtalar joint.
TECH FIG 4 • With a lamina spreader between the talar neck and the calcaneus, the middle and posterior facets of the subtalar joint are easily visualized.
EXPOSURE AND PREPARATION OF THE TALONAVICULAR JOINT
Through the medial incision, the talonavicular joint is easily approached. Make a longitudinal capsulotomy in line with the skin incision over the talonavicular joint.
Elevate the dorsal and plantar capsule off the joint to expose the articular surfaces.
Insert an elevator across the talonavicular joint and use it to release the lateral capsule. This will permit distraction of the joint.
Use a small lamina spreader to distract open the joint for preparation.
Using curettes and osteotomes, remove the articular cartilage down to the subchondral plate.
Use a curved osteotome to aggressively feather the articular surfaces of the talus and navicular.
EXPOSURE AND PREPARATION OF THE CALCANEOCUBOID JOINT
Insert a large lamina spreader into the talonavicular joint and open it to gain access to the calcaneocuboid joint across the foot.
Identify the calcaneocuboid joint using a scalpel or elevator. Check this position with intraoperative fluoroscopy.
Use the elevator to open the joint. Pass a scalpel across the joint to release the lateral capsule and bifurcate ligaments (ligaments that bifurcate from the anterior process of the calcaneus and the cuboid and navicular). Be careful not to violate the lateral skin from inside to out as it will be placed on stretch with correction.
Remove the articular cartilage with a combination of curettes and osteotomes down to subchondral bone.
Aggressively feather the articular surfaces with a curved osteotome (TECH FIG 5).
TECH FIG 5 • The calcaneocuboid joint is easily accessed across the foot after distracting open the talonavicular joint with a lamina spreader.
REDUCTION OF THE DEFORMITY AND INTERNAL FIXATION
Based on the surgeon's preference, the talonavicular or subtalar joint is reduced and fixed first.
Position the subtalar joint in 5 to 7 degrees of hindfoot valgus and fix it with a partially threaded 6.5-mm cannulated screw from the heel into the body of the talus. I also make sure that the calcaneus is translated fully under the talus; residual hindfoot valgus may look good on the operating table but will fail to do so once the patient bears weight.
Reduce the transverse tarsal joints by adducting the transverse tarsal joints and pronating the forefoot. Fix the talonavicular joint with two parallel 4.5- to 5.0-mm cannulated screws from the navicular into the talar body.
Fix the calcaneocuboid joint percutaneously. Insert the 4.5- or 5.0-mm cannulated screw dorsally on the cuboid and pass it retrograde into the tuberosity of the calcaneus (TECH FIG 6).
TECH FIG 6 • The calcaneocuboid joint is fixed percutaneously with a screw from distal to proximal.
POSTOPERATIVE CARE
The patient is placed in a well-padded plaster splint until the incisions have healed. A cast or removable cam-boot is then used for immobilization until 12 weeks postoperatively. Patients are instructed to be strictly non–weight-bearing for the first 6 weeks; they then may progressively bear weight as tolerated. At 12 weeks, immobilization is discontinued and the patient is sent to physical therapy.
OUTCOMES
Seventeen patients underwent single-medial-incision triple arthrodesis.
All 17 demonstrated clinical improvement in alignment and pain relief.
All talonavicular and subtalar joints healed (FIG 4).
Radiographic correction was comparable to previous series describing traditional two-incision triple arthrodesis.
In a cadaver study, 90% of the calcaneocuboid joint articular surface was able to be prepared successfully from the medial incision.
COMPLICATIONS
Two of the 17 patients (12%) developed a nonunion of the calcaneocuboid joint. Neither of these was symptomatic.
Three patients developed valgus ankle arthritis after successful triple arthrodesis. These were managed with total ankle replacement in two patients and ankle arthrodesis in one patient.
FIG 4 • After single-medial-incision triple arthrodesis, the patient shown in Figure 3 had excellent correction of her deformity without wound-healing complications.
REFERENCES
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· Sammarco VJ, Magur EG, Sammarco GJ, et al. Arthrodesis of the subtalar and talonavicular joints for correction of symptomatic hindfoot malalignment. Foot Ankle Int 2006;27:661–666.