Pediatric Ankle Valgus Treatment & Management

Medical therapy has no impact on the natural history of ankle valgus.

Surgical treatment of ankle valgus has an interesting history. Initially, there was some enthusiasm for fibular-Achilles tenodesis to stimulate fibular growth^[17] ; this was mainly applied in patients with evolving ankle valgus due to poliomyelitis or spina bifida. However, such tethering procedures afford slow and sometimes erratic correction. By comparison, bony procedures are more predictable and effective:

Distal tibiofibular synostosis

Commonly performed (temporarily) with a transdesmosis screw, distal tibiofibular synostosis is a prophylactic strategy to prevent the complication of iatrogenic ankle valgus during lengthening of the tibia and fibula or during fibular harvest for vascularized bone graft procedures. In some conditions, surgeons have actually bone grafted the syndesmosis, hoping to preserve permanent parity between the distal tibia and fibula. A bony synostosis will not correct ankle valgus, however.^[18]

Fibular lengthening

The technology exists to accomplish isolated fibular lengthening, either acutely with an intercalary graft or gradually with distraction osteogenesis. This technique has associated complications and drawbacks, however. Given the small diameter and dense cortical nature of the distal fibula, healing may be slow. The focus upon acquired (posttraumatic) fibular shortening in adults need not be extrapolated to children. Basically, if one can provide the latter with a horizontal plafond, correcting ankle valgus, the relative fibular length seems to be unimportant. (See Image below.)

Osteotomy

Supramalleolar varus producing osteotomy is indicated if there is physeal closure or after skeletal maturity. If the deformity is less than 15 º, a simple closing wedge osteotomy, leaving the fibula intact, works well. For larger deformities, including those with rotational deformity, osteotomies of the tibia and fibula may be preferred, with lateral translocation of the distal fragments to preserve the mechanical axis and avoid undue prominence of the medial malleolus. Fixation is either internal, supplemented with a cast, or by an external frame. Weight-bearing is delayed until healing is well under way. Because the procedure is often bilateral, the patient may need to use a wheelchair initially. The many techniques of osteotomy and fixation options are well detailed in standard texts.^[19]

Guided growth (hemi-epiphysiodesis)

Guided growth remains the simplest option. To achieve meaningful correction, there should be at least 1 year of skeletal growth remaining. When in doubt, a hand film for bone age may be helpful. By temporarily restraining the medial tibial physis, the lateral aspect of the physis is free to continue growing, rendering the plafond horizontal.^[20]

Depending on the etiology, it may be advantageous to allow slight overcorrection of up to 5º of varus, anticipating the potential for rebound growth. This will delay the need to repeat the procedure following implant removal. The fibula will grow at its own predetermined rate. This means that even with a horizontal plafond, the fibular station may be elevated. However, this does not seem to adversely affect the clinical outcome. It is not necessary to lengthen the fibula or to fuse it to the distal tibia.

Medial malleolar screw

A single 4.5-mm cannulated screw may be inserted vertically into the medial malleolus to tether the physis.^[21] This is placed percutaneously and is well tolerated. However, the potential disadvantages may include violation of the physis, relatively slow correction because the fulcrum is within the physis, and problems retrieving the screw after the requisite 18-24 months (or longer). (See Images below.)

8-Plate

This 2-hole plate is applied in an extraperiosteal position and secured with 2 cannulated screws. Because it is flexible (nonlocking), does not violate the physis, and provides a medial fulcrum at the center of rotational axis (CORA), the angular correction is more rapid. Importantly, hardware retrieval is simple. This technique may be repeated as necessary during growth. There may be asynchronous growth of the short fibula. However, if the plafond is horizontal, this causes no functional problems. It is not necessary to lengthen the fibula or fuse it to the tibia. (See Images below.)

The preoperative clinical examination should include evaluation of the stance-and-gait pattern, looking for associated deformities of the extremity such as genu valgum, crouch gait, and limb-length discrepancy. Other deformities may need to be addressed at the time of the ankle surgery.

One should carefully assess the feet for flexibility, deformities, contracture, or muscle imbalance. Corrective foot surgery may be combined with guided growth of ankle valgus. Weight-bearing radiographs of the ankles and feet is a prerequisite for intervention.^[15]

The following guidelines pertaining to guided growth may prove to be sufficient for the vast majority of cases of pediatric ankle valgus correction, regardless of the etiology^[19] :

• Supine (tourniquet control) fluoroscopic imaging
• Localize distal medial tibial physis and mark 2-cm incision
• Infiltrate (optional) with 0.25% Marcaine with epinephrine
• Incise skin/subcutaneous tissues but preserve the periosteum
• Insert Keith or similar needle into physis (midsagittal)
• Insert 12-mm 8-plate over needle
• Place distal (epiphyseal) guide pin first; avoid joint or physis
• Place metaphyseal guide pin
• Insert cannulated 4.5-mm screw over each guide pin (length = 16 or 24 mm)
• It is permitted to mix hardware lengths and colors (all are titanium)
• Remove guide pins and countersink screws into plate

These titanium plates are intentionally not locking. The strength is predicated upon serving as a flexible tension band that can bend as the screws reach their maximum divergence of approximately 30º (most ankle valgus deformities are < 25º). The length of the screw is not critical, as long as it does not violate the far cortex.

• Depending on the circumstances, this is typically an outpatient procedure
• A soft dressing will suffice
• Immediate range-of-motion and weight-bearing are encouraged

• Follow-up every 6 months (slow growth at distal tibia) is sufficient
• Allow for up to 5 º of varus overcorrection, depending upon hindfoot alignment
• Remove plate(s) when desired correction is obtained
• Continue to monitor and repeat guided growth as needed

Osteotomy

The potential complications of supramalleolar osteotomy include overcorrection, undercorrection, loss of fixation, would-healing problems, and recurrent deformity.

Guided growth

Occasional problems with hardware retrieval have been eliminated by the use of the 8-plate. Because of the flexible construct that does not violate the physis, the observed correction is more rapid and hardware removal is simplified.

Biological

• Premature physeal closure will not occur if you preserve the periosteum.
• Rebound growth is a poorly understood biological phenomenon and is not necessarily a reflection of the hardware. As long as the parents are informed beforehand, it is readily managed by repeat guided growth if necessary. This is certainly more acceptable than a repeat osteotomy.
• Overcorrection is a matter of judgment; this author often allows slight overcorrection (up to 5º), which may compensate for flexible or rigid hindfoot valgus. If a patient is lost to follow-up and has more overcorrection, one may remove the 8-plate and maintain closer observation. To date, this author has not had to reverse the guided growth or perform an osteotomy.
• Skin breakdown: In very slender children who are wearing ankle-foot orthoses, it is important to shape and pad the orthoses so as to minimize friction on the medial malleolus. As the valgus improves, the hardware prominence lessens proportionally.
• Infection: If a wound infection develops, the implant should be removed (temporarily).

Mechanical

• Plate breakage has not been observed.
• Screw migration may occur. The solution is to redirect the screw percutaneously, under fluoroscopic guidance. If a 16-mm screw does not provide sufficient “purchase,” a 24-mm screw may suffice.
• Screw breakage has not been observed.

As ankle valgus corrects, bracing is facilitated or, in some cases, obviated and shoewear improves. Lateral impingement and subfibular pain are ameliorated.

Compared to the knee, where rapid improvement is noted, the ankle grows slowly. This is especially true in patients with neuromuscular compromise or skeletal dysplasias. Nevertheless, over the course of 18-24 months, most children will manifest signs of clinical and radiographic improvement. The flexible extraphyseal implant may be left in situ longer, if necessary. The theoretical risk of physeal closure is progressive ankle varus (not encountered to date); this may be remedied with an opening wedge supramalleolar osteotomy.

The era of rigid physeal constraint (transphyseal screws) may be drawing to a close. The advantages of a flexible tension band are evident in more rapid correction with fewer hardware-related problems. However, plate retrieval is still necessary. Perhaps, in the future, biodegradable implants will become available. The challenges of control and “planned obsolescence” of such implants still need to be elucidated. Guided growth via chemical or electrical manipulation may someday become a reality.