Peter M. Stevens
DEFINITION
Ankle valgus is a lateral and upward slope of the tibiotalar joint resulting in foot pronation and sometimes lateral translocation of the talus relative to the tibia.
In the anteroposterior (AP) plane, the weight-bearing axis and ground reaction force fall lateral to the virtual center of the joint. This may perpetuate the cycle of growth inhibition and progressive valgus.
ANATOMY
Normal alignment of the ankle involves a horizontal plafond, with a lateral distal tibial angle of 0 to 3 degrees (FIG 1).
Accordingly, the fibula normally bears 15% of body weight.
The talus lies sandwiched between the malleoli, stabilized by the deltoid ligament medially and the talofibular and calcaneofibular ligaments laterally.
In the growing child, the fibular physis lies at or distal to the plafond.
The physes and plafond lie parallel to the floor and perpendicular to the ground reaction forces.
FIG 1 • A. In the normal ankle, the longer fibula provides a lateral buttress and bears 15% of body weight. Its physis is at or below the level of the plafond.1 The ground reaction force (GRF) bisects the ankle, crossing the joint and tibial physis, which are parallel to the ground. B. When the fibula is foreshortened, the lateral buttress effect is lost and the GRF shifts laterally. There is wedging of the tibial epiphysis (Hueter-Volkmann effect) and the plafond tilts laterally. The distal fibular epiphysis broadens owing to impingement of the hindfoot, as a result of increased weight bearing. There may be medial ankle joint widening due to traction.
PATHOGENESIS
The common denominator of ankle valgus is a fibula that is relatively foreshortened and fails to buttress the lateral tilt and shift of the talus during weight bearing.
As the fibular epiphysis bears more than the customary 15% of body weight, it may expand owing to the Hueter–Volkmann effect (another example of form following function).
As the ground reaction force is displaced laterally, the compression of the lateral distal tibial physis exceeds its tolerance and inhibits normal growth, not only of the physis, but of the epiphysis as well (Hueter–Volkmann effect).
There may be widening of the medial clear space due to attenuation of the deltoid ligament.
Subject to chronic and unremitting medial tension, there may be delayed or fragmented ossification of the medial malleolus.
The physes remain horizontal and perpendicular to gravity.
With lateral tilt of the talus, shear forces are introduced and articular cartilage attrition may ensue, commencing at the lateral corner of the ankle.
Subtalar valgus alignment or instability may develop and exacerbate the clinical deformity.
Concomitant genu valgum imposes an eccentric load on the ankle and may compound the alignment problems (hereditary multiple exostoses, clubfeet; FIG 2).
NATURAL HISTORY
The natural history of ankle valgus typically is insidious and progressive. It may be noticed around school age and becomes self-perpetuating.
The natural history is unaffected by corrective shoes or bracing (FIG 3).
In some conditions (spina bifida, cerebral palsy), there may be skin breakdown over the medial malleolus with attempts to control valgus by bracing.
Left unattended, the ultimate method of salvage may require a supramalleolar osteotomy.
This can be avoided by means of medial malleolar epiphysiodesis using a transmalleolar screw or an eight-plate (FIG 4).
PATIENT HISTORY AND PHYSICAL FINDINGS
Typically the parents have noted chronic, progressively flat or pronated feet.
Asymmetric and accelerated shoewear is common.
Activity-related pain is typically lateral, beneath the fibula, as a result of impingement on the talus or calcaneus.
There may be medial pain, presumably due to tension on the deltoid ligament or to brace irritation.
Concomitant knee or hindfoot valgus will exacerbate the symptoms.
FIG 2 • A. Ankle valgus may be mistaken for (or coexist with) planovalgus deformity of the foot. This patient had progressive ankle valgus 6 years after Cincinnati clubfoot reconstruction. Note the prominent medial malleoli. B.This teenager with paralytic ankle valgus (spina bifida) had concomitant genu valgum. Note the increased intermalleolar distance.
While orthotics may provide support, they will have no beneficial effect. As the deformity progresses, brace tolerance diminishes.
The clinician should observe the patient's stance from the hindfoot position.
The patient's knee alignment is observed. Genu valgum or circumduction gait exacerbates hindfoot loading.
FIG 3 • While orthoses may provide comfort and extend shoewear, they will have no effect on the natural history of ankle valgus.
FIG 4 • The focal hinge effect provided by an eight-plate to correct valgus deformity. A. The nonlocking screws are free to swivel as lateral growth restores the ground reaction force to neutral. B. This flexible construct permits more rapid correction than the rigid transphyseal screw, without compromising the physis, and it is easier to remove.
The patient's gait pattern, medial–lateral ankle stress (secondary medial laxity may be evident), and sagittal strength and range of motion (equinus or calcaneus may need treatment) are observed.
The foot is examined to determine whether an orthotic or surgical treatment is needed.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiographs
Weight-bearing AP and lateral views of the ankles
Weight-bearing AP lateral of the feet to assess subtalar alignment
Weight-bearing AP of the lower extremities, if there is perceived valgus or varus deformity of the knee
EMED foot pressure studies (optional)
CT scan or MRI if a distal tibial physeal bar is suspecte.
CT scan of the foot if a concomitant tarsal coalition is suspected
DIFFERENTIAL DIAGNOSIS
The deformity is often bilateral: some of the conditions that are known to result in progressive ankle valgus include the following.
Neuromuscular
Cerebral palsy
Spina bifida
Neurofibromatosis
Hereditary—growt.
Hereditary multiple exostoses
Multiple epiphyseal dysplasia
Genetic
Down syndrome
Other syndromes
Traumatic
Clubfoot
Idiopathic
The underlying diagnosis (see above) has often been established, but the underlying cause has little relevance to the treatment. The degree of deformity and the evolution of symptoms dictate the timing and need for intervention.
NONOPERATIVE MANAGEMENT
Activity restriction and nonsteroidal anti-inflammatories are not helpful.
Physical therapy remedial exercises are of no benefit.
Soft orthoses or UCB inserts are temporizing means of reducing foot discomfort and extending shoewear.
They are relatively more efficacious for subtalar instability than ankle valgus.
They will not effect any growth modulation or improvement in skeletal alignment, however.
SURGICAL MANAGEMENT
The indications for surgery relate to the evolution of activity-restricting pain.
Valgus may be manifest in children under age 10 but is more prevalent during the adolescent growth spurt.
Many patients have already exhausted nonoperative options, such as shoewear modifications, nonsteroidal antiinflammatories, and activity restriction.
Preoperative Planning
Both the clinical examination and appropriate weight-bearing radiographs should verify the presence and magnitude of valgus deformities, not only of the ankles but also (occasionally) of the hindfeet and knees as well.
In specific conditions, multilevel surgery may be indicated.
When the cause involves neuromuscular conditions, concomitant muscle imbalance may warrant combined procedures such as gastrocnemius recession or tendon transfer.
When available, a pedobarograph may be useful for documenting pathologic foot stresses.
Positioning
The patient is positioned supine on the operating table.
The mini or standard C-arm may be used.
Calf or thigh tourniquets are optional, at the discretion of the surgeon.
Approach
For a transmalleolar screw, a 5-mm transverse incision below the tip of the medial malleolus will suffice.
For plate correction, a vertical 12-mm incision over the medial distal tibial physis is optimal.
The dissection is subcutaneous, with preservation of the periosteum.
The only nearby neurovascular structures are the saphenous nerve and vein. These are anterior to the incision and easily avoided.
Supramalleolar osteotomy is the option of last resort.
TECHNIQUES
MEDIAL MALLEOLAR SCREW HEMIEPIPHYSIODESIS
With the patient supine and a calf tourniquet inflated (optional), the tip of the medial malleolus is palpated and a 5-mm transverse incision is marked.
The subcutaneous tissues may be injected with 0.25% Marcaine.
The incision is made sharply and deepened with a hemostat, spreading the subcutaneous tissues down to the tip of the malleolus.
A vertical 1.6-mm guidewire is driven upward, with care taken to avoid the ankle mortise.
Its trajectory should be vertical, so that the screw will be just lateral to the medial cortex.
The more peripheral the fulcrum, the more efficient and rapid the correction will be.
The C-arm is used to check the guidewire placement in the AP, mortise, and lateral projections.
The tip of the malleolus is drilled with a 3.2-mm cannulated drill bit and a single 4.5-mm cannulated, fully threaded, cortical screw 40 to 50 mm in length is inserted (no washer is necessary; TECH FIG 1).
The guidewire is removed and the screw should be tightened so that the screw head is not prominent. However, if the head is buried, the screw may be hard to retrieve in the future.
The wound is closed with 4-0 Monocryl sutures and covered with Steri-Strips, OpSite, and an Ace bandage.
TECH FIG 1 • A. Transphyseal cannulated 4.5-mm screw insertion is performed percutaneously over a 1.6-mm guide pin for accuracy. The ideal fulcrum is near the medial cortex of the tibia for maximal angular correction. Screw removal is facilitated using the guide pin to seat the screwdriver. B. The growth line (arrows) indicates the angular correction achieved to restore a horizontal plafond. Note the downward slope of the physis and the slight bend in the screw, consequent to the intraphyseal fulcrum and the considerable forces of growth on a rigid implant.
GUIDED GROWTH USING AN EIGHT-PLATE
With the patient supine and under tourniquet control, the distal medial tibial physis is identified using the image intensifier.
A 12-mm incision is marked in the skin and (optionally) injected with 0.25% Marcaine.
The incision is made sharply, carrying the dissection through the subcutaneous tissues, with care taken to avoid injury to the periosteum (TECH FIG 2A).
A Keith needle is inserted into the physis and its position is checked with the C-arm (TECH FIG 2B).
A 12-mm eight-plate is inserted, placing its center hole over the needle, and applied extraperiosteally (TECH FIG 2C).
1.6-mm smooth guide pins are inserted, first into the epiphysis and then the metaphysis, avoiding the ankle joint and physis (TECH FIG 2D).
The cortex is drilled to a depth of 5 mm using the cannulated 3.2-mm drill.
Fully threaded, cannulated screws are then inserted (TECH FIG 2E). For the ankle, the 16- or 24-mm screws may be used. There is no particular advantage to the short (16-mm) screw, but sometimes there is not sufficient room for the 24-mm one. The screws do not have to match or to be parallel.
After the plate and screw positions are confirmed on the AP and lateral views, the guide pins are removed and the screws are countersunk into the plate (TECH FIG 2F).
After routine wound closure, a soft compression dressing is sufficient.
TECH FIG 2 • A. For the eight-plate technique, a 12-mm medial incision is made, preserving the periosteum. B. The physis is localized with a Keith needle. C. The eight-plate is slipped over the needle to center this on the physis. D,E. Two 1.6-mm guide pins are inserted parallel to the physis, followed by the self-tapping, cannulated, fully threaded 4.5-mm screws. F. The guide pins are removed and the screws countersunk into the plate. Shown here are 24-mm screws; the alternative is to use the 16-mm screws.
SUPRAMALLEOLAR OSTEOTOMY (SKELETAL MATURITY)
An incision is made over the medial metaphyseal flare of the tibia.
Kirschner wires are inserted to guide the saw or osteotome, and the surgeon triangulates for the closing wedge.
The tibia is cut, leaving lateral cortex intact if possible.
The fibula is left intact unless the surgeon intends to correct more than 20 degrees of rotation.
The tibial wedge is removed.
Smooth, crossed Steinmann pins or plate fixation is used to stabilize = tension band vs. intact fibula.
A below-knee cast is applied and the patient is kept nonweight bearing for 4 weeks.
POSTOPERATIVE CARE
Hemiepiphysiodesis
No immobilization is required.
Immediate weight bearing is permitted.
There are no activity restrictions.
Follow-up is at 6-month intervals with weight-bearing AP radiographs of the ankles.
The implant is removed when the plafond is horizontal, regardless of fibular length.
Supramalleolar osteotomy
The patient uses a cast and crutches for 1 month.
The patient can use a 3D boot for the second month.
Implants are removed after healing.
OUTCOMES
Initially there is no visible difference, and the family needs to be aware of this.
The correction is slow and subtle, so routine follow-up (every 6 months) is imperative.
Correction to neutral, or slight varus, will take 12 to 24 months on average.
The implant is removed on correction of the valgus deformity.
Follow-up should continue until maturity to watch for recurrent deformity.
Premature physeal closure is exceedingly unlikely.
COMPLICATIONS
Complications are predominately related to the transphyseal screws, which are rigid, transgressing the physis and pitted against the dynamic forces of growth (FIG 5).
FIG 5 • A. On the left, the physis blew past the retained screw. B. As a result of stripping, this screw spun in place, migrated proximally, and could not be removed. C. As the valgus deformity corrected, this screw head ended up within the ankle, notching the talus (with pain) and proved challenging to retrieve. D. This patient failed to return before overcorrecting into varus. E. The screw could not be removed, necessitating a corrective opening wedge osteotomy (through the screw). F. This 17-year-old boy with Marfan syndrome presented with a bent implant and varus overcorrection. Luckily his hindfoot valgus compensated and no osteotomy was needed.
FIG 5 • G. After 3 years' absence, this 11-yearold autistic boy returned for follow-up with symptomatic ankle varus. The screws were removed with some difficulty, and time will tell if there is sufficient rebound growth to avert osteotomies.
Stripping, bending, or breakage of the transphyseal screw may make implant removal difficult or impossible.
If the physis closes in the presence of varus deformity, the only recourse is a corrective osteotomy.
Compared to the transphyseal screw, the medial plates are easier to locate and remove.
REFERENCES
· Malhotra D, Puri R, Owen R. Valgus deformity of the ankle in children with spine bifida aperta. J Bone Joint Surg Br 1984;66B:381–385.
· Stevens P. Effect of ankle valgus on radiographic appearance of the ankle. J Pediatr Orthop 1988;8:184–186.
· Stevens P, Aoki S, Olson P. Ball and socket ankle. J Pediatr Orthop 2006;26:427–431.
· Stevens P, Belle R. Screw epiphysiodesis for ankle valgus. J Pediatr Orthop 1997;17:9–12.
· Stevens P, Otis S. Ankle valgus and clubfeet. J Pediatr Orthop 1999;19:515–517.
· Tickle C. Genetics and limb development. Develop Genet 1996;19:1–8.