" Rigid flatfoot is defined by significant restriction of mobility of the subtalar joint"
The development of the longitudinal medial arch of the foot can occur over several years with a wide spectrum of normal variations. The presence of flat feet in older children and adults is within the acceptable range of normal development.
Pediatric flatfoot can be empirically divided into flexible flatfoot and rigid flatfoot . A medial longitudinal arch of the foot that is present while sitting but nevertheless disappears with weight bearing is considered a flexible flatfoot.
- Flexible flat feet are physiological and comprise approximately 95% of cases.
- Rigid flatfoot is defined by significant restriction of mobility of the subtalar joint.
It is not physiological and is often associated with pain and more serious underlying pathology, such as tarsal coalition or a neuromuscular process. The vast majority of patients with neuromuscular flatfoot will have rigid flatfoot.
The management of neuromuscular flatfoot differs from the management of idiopathic and flexible flatfoot because it deserves prompt referral to an orthopedic specialist. Patients with pes cavus (high arched feet) also deserve a neuromuscular diagnostic study and consultation with a specialist.
Although less frequently, patients with painless idiopathic rigid flat feet should be treated with reassurance, as should other patients who do not have foot pain. The main objective of this article is to describe the diagnosis, treatment and current trends in the management of flexible non-neuromuscular pediatric flatfoot.
"Despite widespread prevalence, flat feet are often a misunderstood issue"
Despite widespread prevalence, flat feet are often a misunderstood issue. The lack of high-level evidence to guide indications for treatment perpetuates some confusion.
Additionally, there is no universally accepted classification system or definition of pediatric flatfoot. Several studies have suggested a definition based on footprints, heel-to-arch width, subjective evaluation, or radiographic testing.
Classically the diagnosis of pes planus is assigned to patients who appear to have a collapsed medial arch, however, this is a subjective measure that neglects etiology or specific anatomical considerations. Therefore, parental concern and physician preference tend to drive the evaluation and subsequent management of flat feet. This can lead to unnecessary treatment and expense for a condition that usually does not need intervention.
Occasionally, patients with flat feet who were previously pain-free become symptomatic. The pain can be persistent and debilitating, limiting participation in sports, recreation, and even normal daily activities.
These patients often benefit from some specialist consultation. The authors reviewed possible risk factors for flat feet, physical examination findings, and current surgical and nonsurgical options for the treatment of symptomatic flexible flat feet.
DEVELOPMENT
Babies are usually born with flexible flat feet. At birth, a fat pad is the dominant visible structure in the region of the medial plantar arch. During the first decade of life, the medial longitudinal arch develops along with the bones, muscles, and ligaments in the foot. By 2 years of age, a child usually develops a medial arch that is visible when he is sitting. This arch can collapse with weight support, causing the appearance of flat feet.
Flexible flatfoot usually resolves around age 10, however, in some patients it persists into adolescence and adulthood. It is unclear whether this should be considered a normal variant or a deformity that can lead to future pathology. In the absence of symptoms, most authors agree that flat feet are a variant of the normal foot shape throughout life.
EPIDEMIOLOGY
Cross-sectional epidemiological studies have shown that pes planus is the normal shape of the foot in the first years of life. In children 2 years of age or younger, Morley found a 97% prevalence of flat feet, as defined by the ratio of the width of the heel to the arch.
The prevalence decreased dramatically with age so that only 4% of patients had flat feet around the age of 10 years. This supports the belief that pediatric flatfoot resolves spontaneously over the first decade of development.
In a footprint analysis study of more than 800 patients, Staheli and colleagues found a similar trend with 54% of 3-year-old children having flat feet. The prevalence was reduced to only 26% of patients aged 6, suggesting that ages 3 to 6 years may be a critical period for the development of the medial longitudinal arch. This same study also analyzed footprints in patients up to 80 years old and found that flat feet are within normal limits for adults.
Recent articles analyzed the factors that may predispose children to the development and persistence of flat feet. A study by Chen et al found that greater joint laxity, W-leg sitting, male sex, obesity, and younger age were associated with an increased risk of flat feet in preschool children. from 3 to 6 years.
Similarly, Chang and colleagues found that male sex and obesity were also associated with a higher risk of having flat feet in children aged 7 to 8 years. Other studies confirm that obesity is associated with the persistence of flat feet in older children. There are no studies that have investigated factors that increase the risk of developing symptomatic flatfoot, and this is a potential area of future research.
PATHOGENY
"The bony and ligamentous structures are the most important in maintaining the medial arch of the foot"
No factor has been identified as the fundamental cause of flexible flat feet in pediatrics. Two classic theories have been described for its etiology. One theory suggests that flexible flat feet are the result of decreased muscle strength in the foot. Another theory proposes that the arch is primarily created by the shape and strength of the osseous-ligamentous complex. The latter is supported by the observation that spring ligament incompetence is common in loss of the normal medial arch during weight bearing.
Current opinion generally accepts that bony and ligamentous structures are most important in maintaining the medial arch of the foot, although this remains a topic of debate. The intrinsic muscles of the foot contribute more to strength, stabilization of the foot during ambulation, and protection of ligamentous structures than to the actual shape of the foot. Mann and Inman demonstrated that people with flat feet require greater intrinsic muscle activity during ambulation by stabilizing the foot. This may be an explanation for the muscle pain experienced in symptomatic flat feet.
In support of the muscle weakness theory, Vitare et al recently investigated the activation of extensor muscle groups in patients with flexible flat feet. They used surface electromyography testing to find that patients with flexible flat feet demonstrate poor extensor muscle activity during the heel strike phase of the gait cycle.
Weakness was also present in patients with flat feet when at rest compared to patients without flat feet. Furthermore, extensor muscle weakness was directly proportional to the severity of medial arch collapse. The authors suggest that extensor muscle weakness causes a general imbalance between the muscles of the foot. They propose that this is the sentinel event that leads to the development and persistence of flat feet.
Another recent study by Singh et al looked at bony rotational alignment in children with flexible flat feet. They found that increased tibial torsion and increased hindfoot malalignment, as measured by bimalleolar foot angle, were directly correlated with the presence and severity of medial arch collapse. Patients with more severe bone malalignment were also less likely to respond favorably to conservative treatments.
Benedetti et al also analyzed limb alignment in 53 patients with flexible flat feet. They found that knee internal rotation was the most common limb malalignment in this population, as seen in 43.6% of patients. The presence of knee internal rotation was significantly correlated with the presence of foot symptoms, linking more stance limb abnormalities with the development of symptomatic flat feet.
The development of flat feet is undoubtedly multifactorial. The relationship between the bones, ligaments and muscles of the foot, along with overall limb alignment and comorbid medical conditions, all play a role in the development of flat feet.
CLINICAL FEATURES
Flat feet are generally painless, and most children present for evaluation due to parental concern. It is often helpful to obtain information about a family history of painful feet or special shoe wear, as several studies suggest that flat feet may have a family link. Obtaining a prior developmental history may provide clues to the presence of syndromes with musculoskeletal manifestations.
The physical examination begins with a generalized musculoskeletal examination, which should always include leg rotation profiles. This is best assessed by measuring the internal and external rotation of the hips along with the thigh-foot angle while the patient is prone. An examination of generalized laxity using the Beighton 9-point score is also useful in detecting hypermobility. A score ≥5 may indicate a laxity disorder in children older than 5 years.
The presence of widespread ligamentous laxity or external tibial torsion, especially if combined with excessive femoral torsion (sometimes referred to as "woeful malalignment") warrants ongoing monitoring due to the potential risk of developing symptomatic flat feet.
The shape of the foot is the sum of multiple interactions between a variety of joints, muscles, ligaments, and tendons. The back of the foot, midfoot, and forefoot are interrelated and affect the overall condition of the feet. Patients with flat feet often have posterior foot valgus, dorsiflexion, and midfoot abduction and pronation or forward external rotation of the foot. This combination in sum leads to the loss of the medial arch of the foot.
The examination should include inspection of the feet while standing, sitting, and while walking. The doctor should examine the feet from the front and back while the patient stands. The rear view may reveal a heel valgus, or "too many toes" sign.
Typically, the examiner should be able to see only the fifth and half of the fourth toe when the standing patient is viewed from the rear, even while walking. In the presence of flat feet, the toes are seen more due to external rotation and global abduction in flat feet. It is easy to use the number of toes, viewed from behind, as an objective measure to document the progression or resolution of flat feet.
Angular deformities or deformities in the hips, knees, ankles or feet may appear worse during walking and this may help explain the presence of painful symptoms. Documenting the angle of foot progression during walking is another way to track changes over time.
A longitudinal medial arch of the foot that is present while sitting and yet disappears with weight bearing is a characteristic of a flexible flatfoot. The medial arch should also be reshaped when a patient stands on tiptoe. Observation of foot position in single-leg stance may reveal arch collapse that is not seen in the second supporting leg and is more indicative of foot position during walking.
The arch can also be reconstituted in flexible flatfoot by the "toe-raising test," in which the examiner dorsiflexes the big toe while the patient stands, allowing the plantar fascia to tighten and secondarily reconstitute an arch.
Each of these simple tests can be very reassuring when seeing a worried parent. If these findings are not present, the patient has a rigid flatfoot, which remains flat while sitting, on tiptoe, and tests for toe augmentation due to the relative immobility of the subtalar joint.
This is important to determine the location of any foot pain. Generally, the pain is in the medial part of the midfoot where localized pressure is generated on the head of the collapsed talus where callus formation may be evident.
Pain may also be located on the side of the foot in the sinus tarsi, due to excessive eversion compression of the subtalar joint. Pain that has a sudden onset, is worse at night, or is associated with fever should prompt a series of tests for other more urgent causes of foot pain, such as infection or neoplasia.
Finally, it is important to examine the Achilles tendon complex in the evaluation of a child with flat feet, as this may have important implications for treatment. This is best assessed by the Silfverskiold test. With the knee held in flexion, the foot is held in an inverted position and then dorsiflexed (dorsiflexion).
The amount of dorsiflexion is measured between the lateral edge of the foot and the anterior edge of the distal tibia. This is then done, with the knee held in extension. An angle of less than 10 degrees of plantigrade dorsiflexion with both the knee flexed and extended implies that the entire Achilles tendon is tightened. Less than 10 degrees of dorsiflexion with the knee extended alone implies isolated tightness in the gastrocnemius. This is an important distinction for an orthopedic surgeon in developing a treatment plan.
TREATMENT
The decision to simply observe versus treat a child with flat feet is based on the patient’s symptoms and physical examination findings. Lack of flexibility is often a sign of underlying foot pathology, and referral for further diagnostic workup is indicated. These conditions often require surgical intervention.
For patients with flexible, pain-free flat feet, there is no concrete evidence that any intervention can alter the natural course of foot shape development. Observation is the best resource.
Referral to an orthopedist is recommended for patients with pain, fatigue, or concerns regarding poor alignment. Treatment options for symptomatic patients include physical therapy, shoe wear modification, orthotics, and sometimes surgery.
Asymptomatic flexible flat foot
"Unnecessary treatment of asymptomatic pediatric flatfoot can be costly, with no evidence of change in patient outcome"
In the absence of pain, neither surgical nor nonsurgical management is superior to patient observation. In fact, a recent meta-analysis in 2012 concluded that there is a lack of quality evidence to guide the management of pediatric flatfoot. Clinicians should be aware of this when they are making management decisions for patients with flat feet.
An important debate in the management of patients with asymptomatic flexible flat feet has been the role of shoe and orthotic supports and accessories. A variety of supportive devices have been investigated, including heel cups, heel wedges, silicone insoles, and orthopedic footwear. A prospective study carried out by Wenger and collaborators studied the effectiveness of footwear modifications to alter the development of the longitudinal arch of the foot in 129 patients between 3 and 5 years old.
They were unable to show a significant difference in foot development between patients with shoe wear modifications compared to healthy controls after at least 3 years of follow-up. Whitford and Esterman compared over-the-counter orthoses, custom-made orthoses, and a control group in children aged 7 to 11 years with flat feet. There were no significant differences between groups in reported pain, gross motor skills, self-perception, or exercise effectiveness.
There are some studies that have reported correction of flat feet with the use of arch supports, heel wedges, and over-the-counter orthotics; however, these studies were largely limited by the absence of cross-over controls. Any correction may be due to the natural history of resolution with age. A recent study investigated radiographic characteristics in children with flexible flat feet older than 6 years (mean 10 years) and were treated with rigid foot orthoses.
After 2 years of follow-up, multiple radiographic measurements had improved, suggesting the development of the medial longitudinal arch. However, this study lacked a control group and clinical evaluations to evaluate any improved foot function. It remains to be demonstrated whether the use of orthotics can change the natural course of flat feet in any pediatric age group.
In general, unnecessary treatment of asymptomatic pediatric flatfoot can be costly, with no evidence of change in patient outcome. A study by Pfeiffer et al found that nearly 10% of pediatric flatfoot patients wear some type of orthotic, despite only 2% reporting pain.
Many doctors justify the use of orthotics in asymptomatic children by assuming there is no harm. However, studies have suggested that wearing unnecessary orthotics can lead to orthotic dependence and even long-term negative psychological effects in adulthood.
A notable area of concern is whether the persistence of pediatric flatfoot predisposes patients to chronic foot pain or other pathology in adulthood. If a patient has flexible flatfoot without pain, then it is generally believed that there is a low probability of the condition developing into painful flatfoot.
However, Kosashvili and colleagues found that adolescents with severe to moderate flatfoot had almost double the rate of anterior knee pain and intermittent low back pain. The authors suggested that prophylactic treatment of severe persistent flatfoot deformity may prevent future joint pain, although this has not been proven. As of now, more evidence is needed before prophylactic treatment of asymptomatic flexible flatfoot can be recommended.
Symptomatic flat foot
The hindfoot reverses normal foot mechanics and provides a rigid lever arm for propulsion during push-off in gait. In flexible flatfoot, especially with associated Achilles tendon contracture, the hindfoot may lack the investment necessary to create a rigid lever arm for propulsion. Inefficient push off during walking can cause lower leg pain and foot muscle fatigue.
Symptomatic flatfoot includes a constellation of symptoms such as activity-related pain, foot muscle fatigue, midfoot calluses, and rapid shoe wear. Patients may also experience recurrent ankle sprains, especially with shoes or insoles that provide substantial arch support.
This is because the ankle has a tendency to invert with less contact between the foot and the ground while the heel is neutralized by the special insert. In the presence of these symptoms, referral to an orthopedic surgeon is recommended.
Custom orthopedic accessories have not been proven to be superior to over-the-counter ones, so it makes sense to recommend the least expensive one first.
The initial treatment of painful but flexible flat feet is non-surgical . There are different conservative treatment modalities, such as rest, change of activity, ice application, and non-steroidal anti-inflammatory drugs, which are the initial interventions to reduce pain. In patients with a tight Achilles tendon, the talus remains plantarflexed, and orthotics may increase pain due to pressure against the head of the talus.
The first recommendation should be a home physical therapy program that consists of Achilles tendon stretching and calf muscle strengthening. A recent study by Blitz et al showed that Achilles tendon stretching can help counteract an equinus deformity, but there is still no definitive evidence to show that physical therapy alters the clinical symptoms or structure of flat feet. However, it is a reasonable starting point for management. When a patient has symptomatic flat feet without a tight Achilles tendon, the doctor may consider orthotics as the initial treatment of choice.
Contrary to asymptomatic flexible flat feet, the use of generic orthotics may reduce pain in symptomatic flexible flat feet for some patients. Custom orthopedic accessories
have not been proven to be superior to over-the-counter ones, so it makes sense to recommend the least expensive one first. Only one study has quantitatively demonstrated pain reduction with the use of customized orthoses in patients with concomitant juvenile chronic arthritis and flat feet. Surgery is rarely indicated in flexible flatfoot except in the presence of persistent pain despite a period of observation and nonsurgical management.
The overall goal of surgery is to provide lasting reduction in symptoms throughout the child’s growth into adulthood. There are several surgical methods to achieve this general goal of altering the mechanics and shape of the foot. These include soft tissue reconstruction (e.g., tendon transfers), realignment osteotomies, and motion-limiting non-fusion techniques (e.g., arthrodesis).
Isolated soft tissue surgical options include medial foot capsular tightening procedures, peroneus brevis lengthening, or Achilles tendon lengthening. In general, these have had very poor results with high failure rates because the underlying structural anatomy of the foot is not altered.
Therefore, these procedures are usually performed in conjunction with osteotomies, which result in bone reduction and repositioning in a more anatomical position to help restore normal foot anatomy.
Although one of the mainstays in the treatment of painful flatfoot deformity in adults is fusion of selected joints in the foot, it is not recommended in the pediatric population unless a neuromuscular deformity of the foot is present. The fusion is irreversible and ultimately leads to increased stress on the adjacent midfoot and ankle joints due to the lack of mobility of the joint fusion.
It is best for a pediatric patient to preserve as much range of functional motion as possible, so fusion is generally avoided in the treatment of flexible common flatfoot. However, in adolescents or adult patients with neuromuscular flatfoot, fusion is a viable option as it can provide definitive treatment with reliable results in patients who are minimally ambulatory at baseline.
Osteotomies address the underlying deformities in flexible flatfoot. These surgeries include the medial calcaneal displacement osteotomy, the lateral calcaneal lengthening osteotomy (e.g., modified Evans osteotomy), and the Triple-C osteotomy (calcaneus, medial cuneiform, cuboid).
The calcaneal medial displacement osteotomy effectively compensates for a heel valgus by displacing the heel medially, allowing for a more medial vector and reversal of Achilles tendon output. Postsurgical series have demonstrated significant improvement in foot shape, along with improvements in fatigue symptoms in 89.5% of patients studied after calcaneal medial shift osteotomy.
Lateral lengthening osteotomy is a powerful osteotomy that lengthens the anterior process of the calcaneus, and at the same time can correct hindfoot valgus and forefoot abduction. Mosca demonstrated a good or excellent clinical outcome in 93.5% of cases.
After lateral calcaneal lengthening osteotomy, patients showed significant biomechanical plantar pressure measurement improvements. The postsurgical results of a Triple-C osteotomy have also been generally favorable in a clinical and radiographic evaluation, although these results have been observational without the support of a control group.
In general, positive results after surgical treatment are possible when performed on the right patient. A recent study by Oh et al demonstrated a significantly increased American Orthopedic Society Foot and Ankle Outcome Scale for a mean of 5.2 years after certain osteotomy procedures.
Importantly, return to sports activities occurred in 15 of 16 patients, and all patients who underwent the procedure were satisfied. Akimau and Flowers also demonstrated favorable outcome scores in pediatric patients with flexible flatfoot after a mean of 5.6 years of surgical follow-up.
In summary, osteotomies appear to provide the true improvement in pain and symptoms. More research is needed regarding long-term outcomes in adulthood. Arthrodesis is a type of non-fusion procedure in which the movement of a joint is limited but not completely eliminated.
First introduced in the mid-1900s, this procedure involves placing a metal or bioabsorbable implant into the sinus tarsi of the foot. This is done with excessive eversion of the subtalar joint, subsequently preventing collapse of the arch. Some find this procedure attractive because it is less invasive since no osteotomy is involved. In addition to relieving pain, the goal of this procedure is to prevent loss of posterior tibial tendon function, thereby minimizing the need for future reconstructive foot surgery.
Studies have shown increased ankle dorsiflexion, decreased foot pain, improved radiographic features, and even improved foot impression after this procedure. A recent case series has also demonstrated the potential for maintaining the feet in a correct position, even after subsequent removal of the implant. One of the main concerns regarding this procedure is its high complication rate at 4% and 18% of cases in a recent literature review.
Reported complications frequently include malposition of the implant, inadequate correction of the deformity, extrusion of the implant from the sinus tarsi, foreign body reaction with the implant, peroneal spasm, and persistent foot pain. These complications are generally managed with removal of the implant.
The most serious complications are fracture of the talar neck and development of subtalar fusion. Although most available case series of arthrodesis provide favorable radiographic results and improvement of foot alignment, the complication rate is high and long-term results in adulthood are insufficient.
CONCLUSIONS AND FUTURE DIRECTION
Based on current literature, treatment of flexible flat feet in children is indicated only for those who have painful symptoms. Both orthopedic and surgical treatments can improve levels of pain and function, although the literature clearly lacks rigorous comparative studies for each intervention. A better understanding of the natural history of asymptomatic flatfoot until adulthood needs to be clarified.
It is well known that there is a subset of adults with flat feet who develop disabling pain, posterior tibial tendon dysfunction, and progressive posterior arthritis of the ankle and subtalar joint. It is unclear whether there is a relationship between pediatric flexible flatfoot and the development of posterior tibial tendon dysfunction in adults or whether the altered biomechanics of pediatric flatfoot predisposes to tendon failure.
Prophylactic treatment of asymptomatic flat feet, pain, and expensive orthotics or surgery is not justified until the natural history of flat feet is further investigated. A validated outcome measure for pediatric foot and ankle conditions should be standardized so that outcomes reported across all interventions for symptomatic flatfoot can be clearer and objectively understood.
Highlighted Final Points
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