Om Prasad Shrestha, David A. Spiegel, and James J. McCarthy
DEFINITION
Triple arthrodesis involves fusion of the talocalcaneal, calcaneocuboid, and talonavicular joints. The procedure is most commonly indicated for salvage in severe, rigid deformities of the hindfoot that are unresponsive to less invasive methods of treatment.
This procedure is typically considered in adolescents but has been reported in children as young as 8 years of age.
ANATOMY
Joints of the hindfoot include the ankle, subtalar, talonavicular, and calcaneocuboid.
Motions at the ankle joint include plantarflexion and dorsiflexion. As the ankle joint is oriented along the transmalleolar axis, dorsiflexion is associated with outward deviation of the foot, while plantarflexion is associated with inward deviation.
The subtalar joint consists of an anterior, a middle, and a posterior facet. The anterior and middle facets are confluent in a subset of patients. While there is considerable variation, this joint is oriented 23 degrees medially in the transverse plane and 42 degrees dorsally in the sagittal plane. The subtalar joint thus functions as a hinge along an inclined axis and serves as the linkage between the ankle and the distal articulations of the foot. During the gait cycle, the subtalar joint is everted at heel strike and then inverts progressively until the time of push-off.
The talonavicular and calcaneocuboid joints are known as the transverse tarsal joints. When the calcaneus is everted, these joints become parallel, and there is greater flexibility at the articulation. This aids in shock absorption during initial contact and early stance phase. In contrast, the transverse tarsal joints become nonparallel (more rigid) when the calcaneus is inverted. Functionally, the calcaneus becomes inverted during late stance phase, which locks the transverse tarsal joints and provides a rigid lever for push-off.
From a functional standpoint, the muscles crossing the ankle and subtalar joints may be classified based on their location with respect to each joint axis. There is plantarflexion (gastrocnemius and soleus, tibialis posterior, flexor digitorum longus, flexor hallucis longus) and dorsiflexion (tibialis anterior, extensor digitorum longus, extensor hallucis longus) at the ankle. The movements of inversion (tibialis anterior and posterior, flexor digitorum longus, flexor hallucis longus) and eversion (peroneus longus, brevis, tertius, extensor digitorum longus, extensor hallucis longus) occur across the subtalar axis.
PATHOGENESIS
Foot deformities in children most frequently result from a congenital condition (clubfoot, vertical talus, tarsal coalition) or occur in association with a variety of neuromuscular diseases. In the latter, the cause involves muscle weakness or imbalance, and examples include either flaccid or spastic neuromuscular dysfunction (cerebral palsy, poliomyelitis, myelomeningocele, hereditary motor and sensory neuropathies, other).
The most common deformities are equinovarus, equinovalgus, and cavovarus. Calcaneovalgus, calcaneovarus, calcaneocavus, and equinocavus may also be seen. This spectrum of deformities may result from soft tissue contractures, from bony malalignment, or from both.
While some deformities have a structural component at birth, most develop gradually, are initially flexible, and become fixed or rigid only over time. While a loss of passive motion may result from contracture of the soft tissue elements, progressive adaptive changes in the osteocartilaginous structures subsequently result in fixed bony malalignment.
The equinovarus deformity is present at birth in a congenital clubfoot, or may result from spastic muscle imbalance in patients with cerebral palsy (most often spastic hemiplegia) or flaccid muscle imbalance (poliomyelitis). While the cause of congenital clubfoot remains debated, and is most likely multifactorial, the pathogenesis in neuromuscular diseases involves muscle imbalance (strong inversion–plantarflexion and weak eversion–dorsiflexion).
An equinovalgus deformity is most common in patients with a congenital vertical talus or cerebral palsy (most commonly spastic diplegia). A valgus deformity of the hindfoot is common in patients with a tarsal coalition.
The cavovarus foot is most common in the hereditary motor and sensory neuropathies (Charcot-Marie-Tooth disease) and results from muscle imbalance. Weakness of the tibialis anterior (relative to the peroneus longus) is associated with plantarflexion of the first ray (forefoot valgus), a deformity that is initially flexible.
Over time, a contracture of the plantar fascia and neighboring intrinsic muscle groups develops. To compensate for forefoot valgus, the hindfoot aligns in varus during stance phase.
Both the forefoot valgus and the hindfoot varus eventually become rigid. The hindfoot also appears to be in equinus because of plantarflexion of the midfoot on the hindfoot. A common mistake is to assume that the equinus occurs at the ankle and to perform an Achilles tendon lengthening.
NATURAL HISTORY
The natural history depends on the underlying disease process.
Deformities associated with the neuromuscular diseases will usually progress (and become rigid) over time and will have a significant chance of recurrence despite treatment owing to the underlying disease process.
PATIENT HISTORY AND PHYSICAL FINDINGS
Patients present with an abnormality or change in appearance of the foot, gait disturbance, pain in the region of the hindfoot, difficulties with shoe wear, or more than one of these. While the deformities treated by triple arthrodesis may be diagnosed from birth to adolescence and have often been treated previously, we will focus on the older child or adolescent.
The history focuses on the presence of symptoms, including functional limitations, cosmetic concerns, and shoe wear, the family history (similar deformities, neuromuscular diseases), and previous treatment.
A detailed history is especially important in children of walking age, as a foot deformity may be the first clue to the presence of an underlying neuromuscular problem. While unilateral foot deformities may be seen with tethering of the spinal cord (or other problems such as a spinal cord tumor), bilateral deformities may be the initial finding in patients with a hereditary motor and sensory neuropathy.
The location and character of pain should be determined, in addition to the activities that produce discomfort.
A comprehensive physical examination is required. The spine should be examined to rule out any deformity or evidence of an underlying dysraphic condition, and a careful neurologic examination should be performed. The extremities are evaluated for alignment, limb lengths, and range of motion. Observational gait analysis should be performed. The shoes should be inspected for patterns of wear, which indicate weight distribution during stance phase.
The physical examination of the foot and ankle focuses on the skin (presence and location of callosities, points of tenderness), the overall appearance in both the weight-bearing and non-weight-bearing positions (relationship between the forefoot and hindfoot), the range of motion of the hindfoot joints, the relationship between the forefoot and the hindfoot, and the neuromuscular assessment.
Tests to perform during the physical examination include:
Range of motion at the ankle joint (plantarflexion and dorsiflexion) to diagnose and determine the magnitude of equinus contracture
Range of motion at the subtalar joint (inversion and eversion), which quantifies motion at the subtalar joint. Generally, the amount of inversion is twice the amount of eversion. The total range is 20 to 60 degrees.
Range of motion at the transverse tarsal joints
Relationship between forefoot and hindfoot alignment, which identifies any coexisting deformity of the forefoot, either varus (the lateral aspect of the forefoot axis is more plantarflexed than the medial aspect) or valgus (medial aspect of the forefoot axis is more plantarflexed than the lateral forefoot axis)
Coleman block test, which determines if hindfoot varus is flexible or rigid
Manual muscle testing, which assesses relative strengths of motor units across the ankle and subtalar joints. This helps to diagnose muscle imbalance and to plan tendon transfers if appropriate.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Imaging studies complement the history and physical examination, and plain radiographs in a weight-bearing position are required in all cases. In addition to a standing anteroposterior (AP) and lateral radiograph of the foot, a standing AP of the ankle should be obtained to determine whether the deformity is in the ankle joint, the subtalar joint, or both locations. Other imaging modalities such as a CT scan or MRI may be required in selected cases.
Plain radiographs are used to evaluate bone and joint morphology, and measuring the angular relationships between the tarsal bones (or segments of the foot) helps to further define both the location and the magnitude of deformities.
On the standing AP radiograph, measurements include the talocalcaneal (Kite) angle (10 to 56 degrees) and the talus–first metatarsal angle (range −10 to +30 degrees). For the AP talocalcaneal angle, values less than 20 degrees suggest hindfoot varus, while an angle greater than 40 to 50 degrees suggests hindfoot valgus. For the talo–first metatarsal angle, values less than −10 degrees indicate forefoot varus and values greater than +30 degrees indicate forefoot valgus.
On the standing lateral radiograph of the foot, measurements include the lateral talocalcaneal angle, the tibiocalcaneal angle, and the talus–first metatarsal angle.
For the lateral talocalcaneal angle (range 25 to 55 degrees), values greater than 55 degrees indicate hindfoot valgus or calcaneus, while values less than 25 to 30 degrees indicate hindfoot varus or equinus deformities.
For the tibiocalcaneal angle (55 to 95 degrees), values greater than 95 degrees suggest equinus, while those below 55 degrees are suggestive of calcaneus.
For the talus–first metatarsal angle, or Meary angle (0 to 20 degrees), values greater than 20 degrees indicate midfoot equinus (cavus), while values less than 0 degrees indicate midfoot dorsiflexion (midfoot break).
The angle of the calcaneus relative to the horizontal axis (calcaneal pitch) is increased with calcaneus or calcaneocavus, or with cavovarus deformities.
DIFFERENTIAL DIAGNOSIS
Equinovarus: congenital clubfoot, poliomyelitis or other flaccid weakness or paralysis, spastic hemiplegia, other
Equinovalgus: congenital vertical talus, spastic diplegia or quadriplegia, tarsal coalition, flexible flatfoot with tight Achilles tendon, other
Cavovarus: hereditary motor and sensory neuropathies, poliomyelitis or other flaccid weakness or paralysis, myelomeningocele, other
NONOPERATIVE MANAGEMENT
The goals of nonoperative treatment are to achieve correction, to maintain correction, and to prevent recurrence of the deformity. The specific treatments are based on the underlying disease process, and options include physical therapy, injection of botulinum A toxin, serial casting, and orthoses.
Physical therapy is directed toward improving range of motion and improving strength.
Serial casting may help to improve range of motion.
Botulinum toxin injections result in a reversible chemical denervation of the muscle group (for 3 to 8 months) and have been used most frequently in patients with cerebral palsy to decrease spasticity and reduce dynamic muscle imbalance. Such treatment may prevent or delay the need for surgical intervention in patients with spastic equinovarus or equinovalgus.
Orthoses may be used to maintain alignment during ambulation, or as a nighttime splint to prevent the development of contractures. The deformity should ideally be passively correctable. Foot orthoses such as the UCBL may help to control varus–valgus alignment of the hindfoot during ambulation. An ankle–foot orthosis improves prepositioning of the foot during swing phase, provides stability during stance phase, and can be used as a night splint.
SURGICAL MANAGEMENT
Surgical treatment is offered when nonoperative measures have failed to alleviate the symptoms. Triple arthrodesis is a salvage procedure or “last resort” for rigid deformities in older patients, many of whom have been previously treated by both nonoperative and operative strategies.
The procedure is often performed for the correction of rigid deformities, which typically requires removal of bony wedges. As such, careful preoperative planning is required to determine the appropriate size and location of these wedges. Triple arthrodesis shortens the foot, which may be cosmetically objectionable.
Arthrodesis transfers additional stresses to neighboring joints, which may result in degenerative changes and pain. While there are reports of the procedure being successful in children as young as 8 years, it has been suggested that surgery should be delayed until the foot has reached adult proportions. One recent study concluded that growth rates were no different in those children treated before or after 11 years of age.
The deformity should be of sufficient severity that soft tissue releases and osteotomies would be unlikely to achieve correction, or when painful degenerative changes are observed in the joints of the hindfoot. The most common indications are recurrent or neglected (most commonly seen in developing nations) clubfoot, cavovarus associated with Charcot-Marie-Tooth disease, and severe equinovalgus deformities in patients with spastic diplegia.
The goal of surgery is to achieve a plantigrade foot by restoring the anatomic relationships between the affected bones or regions of the foot, and to relieve pain.
Additional procedures may be required. An equinus deformity of the ankle will require a lengthening of the tendo Achilles at the time of triple arthrodesis. The treatment of a coexisting forefoot may require soft tissue release, tendon transfer, or osteotomy, or some combination of these (usually as another stage). In patients with neuromuscular diseases, lengthening or transfer of tendons crossing the hindfoot may be required to restore muscle balance and prevent further deformity. Recurrence of deformity may occur when coexisting muscle imbalance has not been treated.3,15
A hindfoot arthrodesis should be avoided in patients with insensate feet (myelomeningocele, other).
While triple arthrodesis is routinely performed without fixation (or with minimal fixation such as Kirschner wires or staples) in many parts of the world, fixation with staples or screws reduces the chances of correction loss and pseudarthrosis.
Biomechanical studies have demonstrated no significant difference in stability when comparing fixation with staples versus cannulated screws.8,9
Preoperative Planning
Weight-bearing radiographs are used to evaluate the relationships between the tarsal bones, to identify any morphologic abnormalities or degenerative changes, and to identify the location of the deformity. These radiographs help to plan the location of wedge resections.
Positioning
The patient is placed supine, and a bump may be placed under the ipsilateral hip.
A tourniquet is applied around the thigh.
Approach
Several skin incisions have been described for triple arthrodesis, and the specific choice may depend on the type of deformity and the previous experience of the surgeon. These include the single lateral or anterolateral approach, the medial approach, and a combined lateral and medial approach.
The lateral approach (Ollier) is used most commonly and allows excellent visualization of all three joints (FIG 1).
A medial approach may be useful for calcaneovalgus foot, and the Lambrinudi procedure is considered for severe equinus deformity. The articular surfaces of the talonavicular, calcaneocuboid, and subtalar joints are removed to achieve arthrodesis.
Modifications of this basic technique are based on the underlying deformity and involve bony wedge resections to correct specific components of the deformity.
FIG 1 • The lateral approach is used most frequently. A. The skin incision extends from distal to the fibular malleolus across the sinus tarsi. B. All three joints can be visualized after dissection of the subcutaneous tissues, elevation of the extensor digitorum brevis off the anterior process of the calcaneus, and opening of the joint capsules. C. Placement of a laminar spreader may facilitate visualization of the posterior facet of the subtalar joint.
TECHNIQUS
PENNY'S MODIFIED LAMBRINUDI TRIPLE ARTHODESIS10
There are several unique features associated with the neglected clubfoot in adolescents that require special attention when performing a triple arthrodesis.5
A lengthening of the tendo Achilles is required and is performed as the first step.
The main components are hindfoot equinus and varus, midfoot cavus, and forefoot adduction.
In contrast to other hindfoot deformities, there is always significant obliquity of the calcaneocuboid joint, which requires a specially oriented lateral wedge excision of the calcaneocuboid joint.
The foot is typically severely plantarflexed, and this component of the deformity comes from both the hindfoot equinus and the midfoot cavus.
An aggressive resection of the talar head is commonly required to correct the midfoot cavus and bring the forepart of the foot to a plantigrade position.
TECH FIG 1 • The bony segments are removed to correct the neglected clubfoot. Conservative resection is shown in blue and aggressive resection in red.
The areas of bone to be resected are shown in TECHNIQUES FIGURE 1.
Incision and Dissection
The skin incision is started 1 cm distal to the tip of the fibula. It is curved dorsolaterally and extends to the lateral border of the talonavicular joint.
After spreading the subcutaneous tissues, the extensor tendons are retracted medially and the peroneal tendons are mobilized and protected. The sural nerve is also identified and protected (TECH FIG 2).
The extensor digitorum brevis is elevated off its origin and reflected distally, exposing the sinus tarsi, the calcaneocuboid joint, and the lateral aspect of the talonavicular joint.
Soft tissues are cleared from the sinus tarsi, which promotes visualization of the facets of the subtalar joint. The anterior and middle facets will be confluent in a subset of cases.
Arthrodesis
The first step of the procedure involves removing a lateral wedge (calcaneocuboid resection) to shorten the lateral border of the foot (TECH FIG 3A). One unique feature of the neglected clubfoot is the obliquity at the calcaneocuboid joint.
An osteotome or oscillating saw is used to make a transverse cut perpendicular to the long axis of the lower leg.
The second cut removes the joint surface of the cuboid and should be conservative (several millimeters). Most of this wedge resection comes from the calcaneus.
The second step involves removing an anteriorly based wedge from the anterior process of the calcaneus to correct equinus of the forepart of the foot (TECH FIG 3B).
The third step involves resecting a portion of the head and neck of the talus (TECH FIG 3C).
The cut begins at the dorsal articular margin of the talus and extends in a proximal and plantar direction through the posterior subtalar joint.
TECH FIG 2 • Lateral exposure. (From Penny JN. The neglected clubfoot. Tech Orthop 2005:7:19–24.)
TECH FIG 3 • A. Wedge resection of the calcaneocuboid joint. B. Wedge resection of the anterior process of the calcaneus. C. Excision of the head and neck of the talus back to the posterior facet of the subtalar joint. D. The anterior talus is placed into a notch in the navicular. E. The joint is pinned with the foot in a corrected position. The heel varus corrects with the subtalar joint resection. (From Penny JN. The neglected clubfoot. Tech Orthop 2005:7:19–24.)
This cut is oriented perpendicular to the long axis of the tibia. This essentially removes the entire talar head and a portion of the talar neck.
The fourth step involves a conservative resection of the articular surface of navicular, as well as removal of the tuberosity of the navicular.
A notch is made in the inferior articular surface of the navicular to accept the anterior portion of the talus.
With the surfaces of the talus and calcaneus apposed, the anterior end of the talus is pushed into the notch under the navicular while abducting the forefoot (TECH FIG 3D).
Fixation is usually achieved with Kirschner wires, staples, or screws (TECH FIG 3E).
The heel varus usually corrects spontaneously.
LAMBRINUDI TRIPLEARTHRODESIS 5
The incision begins 1 cm distal to the tip of the fibula; it curves dorsolaterally and extends to the lateral border of the talonavicular joint.
The extensor tendons are retracted medially, while the peroneal tendons are mobilized and protected. The extensor digitorum brevis is reflected distally, exposing the sinus tarsi, the calcaneocuboid joint, and the lateral aspect of the talonavicular joint.
The sinus tarsi is cleared of soft tissue to expose the anterior, middle, and posterior facets of the subtalar joints.
Sequential osteotomies are made with a broad osteotome or power saw (TECH FIG 4A).
TECH FIG 4 • Lambrinudi technique. A.The shaded area represents the bone to be removed. B. Realignment of the foot is achieved after removal of bony wedges.
The first osteotomy is made along the inferior part of the talus perpendicular to the long axis of the tibia in both planes.
The second osteotomy is made along the superior part of the calcaneus parallel to the sole of the foot in both the longitudinal and transverse planes.
The third cut is made at the distal end of the calcaneus at a right angle to the long axis of the calcaneus.
The final cut is made along the proximal end of the cuboid at a right angle to the longitudinal axis of the forefoot.
A groove is fashioned in the inferior proximal part of the navicular to accept the anterior end of the talus.
The osteotomized surfaces are approximated (TECH FIG 4B) and held with staples.
The extensor digitorum is lightly sutured back into place, and the subcutaneous tissue and skin edges are reapproximated.
TRIPLE ARTHRODESIS USING A SINGLE MEDIAL INCISION7
A 2-cm longitudinal incision is made over the peroneal tendons 10 cm above the level of the ankle joint, and both tendons are delivered using a mosquito clamp and divided sharply.
An 8-cm medial longitudinal incision extends from the undersurface of the posterior medial malleolus across the talonavicular joint.
The talonavicular joint is exposed, and the tibialis posterior tendon is released from its insertion. The talonavicular capsule is released. Flexor digitorum longus tendon, flexor hallucis tendon, and neurovascular bundle are protected by a retractor.
The talocalcaneal interosseous ligament is divided, and the anterior, middle, and posterior facets of the subtalar joint are visualized.
The subtalar and talonavicular joint surfaces are denuded and prepared.
The calcaneocuboid joint capsule and bifurcate ligaments are released sharply, and a lamina spreader is inserted to facilitate removal of the joint surfaces.
Fixation of the subtalar joint is achieved with a single 6.5-mm cannulated screw from the posterior calcaneus into the talar body.
The talonavicular and calcaneocuboid joints are realigned and stabilized with 5-mm cannulated screws.
BEAK TRIPLE ARTHRODESIS FOR SEVERE CAVUS DEFORMITY13
A lateral approach is employed, as outlined above. Wedges to be removed are shown in TECHNIQUES FIGURE 5A.
The articular cartilage of the subtalar and calcaneocuboid joints is denuded.
The talar neck is osteotomized from inferior to superior, forming a beak superiorly. The soft tissue structures on the superior aspect of the talus anterior to the ankle are left undisturbed.
The dorsal cortex of the navicular is excised.
The forefoot is displaced plantarward and the navicular is locked beneath the remaining part of the talar head and neck.
Stability can be maintained while plaster is applied by slight upward pressure under the forefoot (TECH FIG 5B). A staple may be used for fixation.
TECH FIG 5 • Beak triple arthrodesis technique. A. Wedges to be removed. B. Final alignment after correction.
INLAY GRAFTING METHOD FOR VALGUS DEFORMITY (MODIFIED TECHNIQUE OF WILLIAMS AND MENELAUS)
The original technique by Williams and Menelaus16 involves placing an inlay graft from the tibia. El-Batouty et al4 modified this to obviate the need for a medially based closing wedge osteotomy for valgus deformity of the hindfoot.
An anterolateral exposure is used, as described previously.
The joint surfaces are removed, and the hindfoot is realigned and stabilized with two Kirschner wires.
An inlay graft is taken from the tibia and placed into a rectangular trough created across the talonavicular, calcaneocuboid, and anterior subtalar joints (TECH FIG 6).
The posterior subtalar joint is then denuded and local bone graft is placed.
A cast is applied, and the Kirschner wires are removed.
TECH FIG 6 • Modified Williams and Menelaus's inlay grafting technique.
POSTOPERATIVE CARE
The limb is typically immobilized in a shortor long-leg cast for at least 6 weeks, and weight bearing is permitted after 6 weeks.
An ankle–foot orthosis may be required in patients with a neuromuscular diagnosis.
OUTCOMES
Most studies have involved mixed populations (children and adults) with a variety of diagnoses at early to midrange followup, using variable criteria (objective and subjective) to assess outcome.
Overall, successful results have been reported in most patients, with patient satisfaction in the range of 50% to 95%.11,12 Rates of union are 89% to 95%.7,12
In general, poor outcomes have been associated with residual deformity or pseudarthrosis.
Outcomes seem to be similar when comparing children and adults. The results vary somewhat based on the underlying diagnosis, and they seem to deteriorate with longer-term follow-up.
Most patients have difficulty walking on uneven surfaces. Instrumented motion analysis studies by Beischer et al2 and Wu et al17 revealed an increase in ipsilateral knee flexion during stance phase (including push-off) and a loss of ankle plantarflexion during push-off. Power generation at the ankle is decreased up to 45%.
Degenerative changes are common in the surrounding joints at long-term follow-up but do not imply the presence of pain or a deterioration in results. Chronic pain is seen in a subset of cases.
In cerebral palsy, Ireland et al6 found excellent results in all patients at 4.5 years of follow-up. Tenuta et al14 found that 80% of patients were satisfied at 18 years of follow-up, although 25% had occasional pain and 14% had persistent pain. Lack of satisfaction was correlated with residual deformity or pain.
The results in patients with cavovarus feet (Charcot-MarieTooth) are less predictable.
At 12 years of follow-up, Wukich and Bowen18 observed excellent or good results in 88%, with 15% pseudarthrosis and degenerative changes in 64%.
At 21 years of follow-up, Wetmore et al15 found excellent or good results in only 24%, with recurrence in nearly 50% because of progressive weakness or muscle imbalance. Twenty percent required conversion to a pantalar arthrodesis for ankle pain associated with degenerative changes.
With flaccid neuromuscular imbalance (poliomyelitis), the results have been adequate in most patients, provided that adequate muscle balance has been achieved in addition to the arthrodesis. Crego et al3found recurrence in 20% of patients, mostly due to persistent muscle imbalance.
COMPLICATIONS
Injury to neurovascular or tendinous structures. The medial neurovascular bundle and flexor hallucis longus tendon must be protected during resection of the posterior facet of the subtalar joint.
Wound infection
Wound breakdown or skin necrosis
Pseudarthrosis of one or more joints, most commonly the talonavicular
Residual deformity
Recurrent deformity may be observed in patients with progressive neuromuscular disease (Charcot-Marie-Tooth) or persistent muscle imbalance (poliomyelitis, cerebral palsy).
Degenerative changes are commonly observed at longerterm follow-up (longest study is 44 years) and result from increased stress transmission to the neighboring joints. These changes may be observed in the midfoot (54% to 99%1,11,18) or the ankle joint (24% to 100%11,14,18).
Pain from persistent malalignment, degenerative changes, or avascular necrosis of the talus
Difficulties with shoe wear
Need for orthotic support or an assistive device for ambulation
REFERENCES
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