Pes Planus

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Introduction

Pes Planus A.k.a flat foot

Pes planus/ pes planovalgus (or flat foot) is the loss of the medial longitudinal arch of the foot, heel valgus deformity, and medial talar prominence. This is often observed with the medial arch of the foot coming closer (than typically expected) to the ground or making contact with the ground.

All typically developing infants are born with flexible flat feet, with arch development first seen around 3 years of age and then often only attaining adult values in arch height between 7 and 10 years of age.

Classification

The classification of the pes planus is based on three aspects:

• Arch height: The best parameter to characterize medial longitudinal arch structure was found to be a ratio of navicular height to foot length. It is accepted that the flatness of normal children’s feet and their age are inversely proportioned.
• Heel eversion angle: Heel eversion or hindfoot valgus is generally accepted as a normal finding in young, newly walking children and is expected to reduce with age. The eversion of the heel has been repeatedly used for determining the posture of the child’s foot. Resting calcaneal stance position is a more recent method. It has guided clinicians in assessment of the child’s foot posture and calcaneal eversion has been suggested to reduce by a degree every 12 months to a vertical position by age 7 years. A vertical heel is optimal for foot function. The average rear foot angle for children from 6 to16 years is 4° (raging from 0 to 9° valgus).

• Whether the flat foot structure is rigid or flexible

1. Flexible flat foot (flexible FF): The longitudinal arches of the foot are present on heel elevation (tiptoe standing) and non-bearing but disappear with full weight bearing on the foot.
   • FF is termed developmental FF when observed in infants and toddlers and is part of normal development. Between the ages of 8 and 10 however, a clinician may consider this a true FF.
2. Rigid flat foot: The longitudinal arches of the foot are absent in both heel elevation (tiptoe standing) and weight bearing.

Epidemiology

Roughly 20% to 37% of the population has some degree of pes planus, With most cases being the flexible variety. It is more common in children (about 20-30% of children with some form of flat feet) with most children going on to develop a normal arch by 10 years old. Genetics play a strong role with it typically running in families.

Etiology/Causes

The etiology of pes planus has several factors implicated and can be either congenital or acquired.

Congenital Pes planus

Congenital pes planus is classified as developing in the first years of life. Both flexible FF and rigid FF can present.

At birth and within early childhood pes planus is a typical observation of development and is termed flexible flat foot (FF). It is attributed to osseous and ligamentous laxity, immature neuromuscular control and the presence of adipose tissue under the medial longitudinal arch (MLA), making the arch appear flat.

When flexible FF is observed in older children (typically those above 8 years of age) and adults, the following must be considered:

• General/ global hypermobility, including conditions such as Ehlers-Danlos syndrome (EDH) and Down Syndrome.
• Conditions with increased tone, e.g. cerebral palsy.
• Higher body mass index (BMI).
  • A note: While increased BMI and even obesity have been attributed to increased predisposition to flexible FF, more recent investigations call these findings into question. These studies, which have taken into account a more comprehensive foot morphology (not simply footprint measurements) have not found higher rates of flexiable FF in paediatric populations. These have however, have been done with participants with higher BMI and not necessarily a diagnosis of obesity.
• Subtalar joint morphology.
  • Recent research has highlighted the variance in subtalar joints. One such study highlighted 2 different types: The first, a firmer supporting joint, and another weaker joint where the anterior articulation in the subtalar joint is absent. The absent articulation allowing the FF posture to develop.

An example of rigid FF is tarsal coalition, where there is a failure of the tarsal bones to separate. This causes a bony , sometimes cartilaginous or even fibrous bridge between two or more of the tarsal bones.

Other examples of congenital pes planus include:

• Congenital vertical talus
• Congenital talipes equinovarus
• Tibial torsional deformity
• Presence of the accessory navicular bone.
• General ligament laxity
• Genetic malformation such as Down syndrome and Marfan syndrome
• Familial factors
• Peroneal spasm
• Vertical talus

Acquired Pes planus

Acquired pes planus may arise from:

• Diabetes

• Foot and ankle injury such as rupture or dysfunction of the posterior tibial tendon.
• Some medical conditions such as arthritis, spina bifida, cerebral palsy, Arthrogyroposis, and muscular dystrophy.
• Flat feet can also occur as a result of pregnancy.
• Iatrogenic factors such as posterior tibialis tendon (PTT) transfer.

Clinically Relevant Anatomy

Medial arch of the foot

See Arches of the Foot

Pathophysiology

The pathophysiology of pes planus can vary greatly depending on whether it is congenital or acquired, and then whether it is flexible or fixed.

Dynamic factors

Insufficiency of the posterior tibial tendon: When this occurs, forefoot valgus occurs. Over the long term this produces achilles tendon contractures and transforms the gastrocnemius and soleus muscle complex into heel everters (rather than inverters).

When a peroneal spastic flatfoot is seen, the peroneal tendon which crosses over the subtalar joint often goes into spasm. This is secondary to subtalar inflammation.

Static factors

Boney architecture of the medial longitudinal arch. Here altered morphology of the joints of the midfoot would affect stability.

Fixed or rigid pes planus is due to a structural abnormality. As noted in etiology, this most often presents as a tarsal coalition. Limited range is seen in the subtalar and midfoot motion when there is failure of tarsal bones to separate. This coalition can be cartilaginous, fibrous or even boney. This condition often causes pain and inflammation of the joints.

The spring ligament complex has been noted as an important stabiliser, but clarity still lacks in the literature. Plantar fascia offers stability to the medial longitudinal arch via the windlass effect. In conditions where the laxity of these tissues is affected, for example in EDH, arch stability can be compromised.

The medial longitudinal arch of the foot normally develops by the age of 5 or 6 as the fat pad in babies is gradually absorbed, balance improves and skilled movements are acquired. In some children, however, the arch fails to develop which may be a result of tightness in the calf muscles, laxity in the Achilles tendon or poor core stability in other areas such as around the hips.

The bony arch of the foot is potentially unstable and is bound together by ligaments. They withstand short-term stresses. Their primary function is to act as sensory end organs, so when stretched, appropriate muscles are reflexively brought into action. Even the most anatomically perfect foot will become rapidly and grossly flat unless it has muscles of good bulk and tone to support it. The physiological fault may lie in the muscle itself or its nervous control:

1. Inadequate nervous control: In normal development, a baby has to learn to balance first its head, then its trunk and eventually to balance the whole body on the feet. The difficult art is not required during the early months of life; but sometimes the balancing reflexes fail to develop even after the child has begun to walk. In that event, the arch inevitably collapses with body weight. Myelination of the pyramidal fibers to the foot is incomplete at birth and the plantar responses in babies is extensor. If the infantile flat foot persists into early childhood, the extensor responses may persist too, and it is tempting to assume that balancing cannot be easily learned until myelination is complete.
2. Inadequate muscles:
   • After illness or enforced recumbency, the muscles may temporarily be weak and the arch consequently falls when walking is resumed.
   • A more lasting form of muscle weakness accompanies a generally poor posture.
   • The child (often a pre-adolescent girl) presents a familiar flabby contour with head stuck forward, mouth open, chest flat, back rounded and abdomen protuberant.
   • The gluteal muscles are concerned largely with posture (Wiles 1949). They help to straighten the hip and knee, and to twist the limb outwards. This twist can not be imparted to the foot which is anchored to the ground, and so the rest of the limb turns outwards relative to the foot. As a result, the arch is lifted and the line of weight corrected only when the glutei work properly.
   • Relative inadequacy of muscle is well illustrated by when extra strain is put upon the arch, for example in overweight individuals.
   • Prolonged standing is more harmful to the feet than walking because, during walking, the muscles supporting the arch alternately contract and relax which is the best training for a muscle.

Flat foot Xray

The calcaneus, navicular, talus, first three cuneiforms, and the first three metatarsals make up the medial longitudinal arch. This arch is supported by posterior tibial tendon, plantar calcanea navicular ligament, deltoid ligament, plantar aponeurosis, and flexor hallucis longus and brevis muscles. Dysfunction or injury to any of these structures may cause acquired pes planus. Also, excessive tension in the triceps surae, obesity, Achilles tendon or calf muscle tightness, ligamentous laxity in the spring ligament, plantar fascia, or other supporting plantar ligaments may result in acquired flat foot.

Rigid pes planus is rare but usually starts from childhood; tarsal coalition, accessory navicular bone, congenital vertical talus, or other forms of congenital hindfoot pathology. are usually the underlying factors.

Characteristics/Clinical Presentation

Evaluation should be based on the presentation at clinic.

Pes planus is very common in young children and asymptomatic. In some cases, flat feet can become painful or rigid, which may be a sign of underlying foot pathology, eg tarsal coalition. In adults, pes planus may be an incidental finding. In symptomatic patients, there may be complaints of pain due to strained muscles and connecting tissues in the midfoot, heel, lower leg, knee, hip, and or back. In more advanced changes client may complain of an altered gait pattern. Clients who typically overpronate will be at high risk for ankle sprains from chronic “rolling of the ankle.” Ask the client about the onset of deformity, timing of symptoms, severity of past and current symptoms, history of trauma, family history, surgical history, and past medical history (including hypertension, diabetes, rheumatoid arthritis, sensory neuropathies, seronegative spondyloarthropathies, and obesity).

Flat foot

Other signs may include:

1. Oedema at the medial side of the foot
2. Stiffness of one or both arches of the feet
3. Contractures of feet and ankle muscles att the lateral compartment
4. Uneven distribution of body weight with resultant one-sided wear of shoes leading to further injuries.
5. Difficulty in walking

Associated Co-morbidities

Co-morbidities include but not limited to neurological conditions such as cerebral palsy; genetics e.g downs syndrome, Marfan syndrome or Ehlers Danos; charcot joint; tibialis posterior dysfunction; Obesity; arthropathies; Shprintzen-Goldberg syndrome.

Diagnostic Procedures

• Footprints: It is still controversial if footprints reflect the real morphology of the medial longitudinal arch. Recent development found an initial correlation between dynamic pressure patterns and static foot-prints.
• X-rays are used to categorise the feet as having normal, slightly flat and moderate arches.
• Foot-posture index (FPI-6)
• Supination resistance test : This test is used to estimate the magnitude of pronatory moments. The foot is manually supinated. The higher the force required, the greater the supination resistance and the stronger the pronatory forces. This test is subjective.
• Jack’s test and Feiss angle (are related) : Performing the Jack’s test. The hallux is manually dorsiflexed while the child is standing. If the medial longitudinal arch rises due to dorsiflexion of the hallux, the foot is considered a flexible flat foot. If the medial longitudinal arch remains unchanged, the test designates a rigid flat foot. The purpose of this test is to check the foot flexibility and the onset of the windlass mechanism by tensioning the plantar fascia trough the extension of the first metatarsophalangeal joint. The Feiss line is the line interconnecting malleolus medialis, navicular and first metatarsal head. The inclination of this line with the ground increases when the first metatarsophalangeal joint is dorsiflexed (Jack’s test). This dorsiflexion activates forefoot supination and raises the arch height (140°± 6°).
• Ankle range : Children’s ankle range assessment is generally an unreliable measure, as typically assessed when the child is non-weight-bearing. So it is suggested that therapists look at a child’s ability to squat, heel walk and increase stride length.

Medical Management

The merit of treatment for all flexible flat feet remains ambiguous, with evidence showing that foot orthoses produces improvements in children with pes planus. It remains difficult to conclude if spontaneous physiological arch improvement occurred or the effect of intervention caused the arch improvement.

• There is little evidence for treatment of asymptomatic, flexible, pediatric flat feet in a child who have no underlying medical issues.
• Treatment of symptomatic, flexible flat feet is generally accepted for children with contributory background factors or secondary complications, or if pes planus persists past childhood.
• Evidence supports the use of non surgical interventions for painful pes planus.
• The child should be fitted with a flat, lace-up shoe with a firm heel and MLA support, a broad and deep toe box and the ‘toe break’ at the junction between the anterior third and posterior two-thirds of the shoe. 

Treatment is based on etiology and NSAIDS are sufficient for pain.

Surgery is required in rigid pes planus and in cases resistant to therapy to reduce symptoms. Most surgical methods aim at realigning foot shape and mechanics. These surgeries could be tendon transfers, realignment osteotomies, arthrodesis and where other surgeries fail, triple arthrodesis is performed

For the congenital pes valgus treatment, researchers have defined the best possible treatments depending on the age of the person/child.

• In a child younger than 2 years, an extensive release with lengthening of the Achilles tendon and fixation procedure is recommended. It is less invasive than other techniques, because there is no tendon transfer or bony procedures needed. The explanation could be because of the greater adaptability of the cartilaginous structures.
• In a child with neural tube defect, younger than 2 years of age, an extensive release with tendon transfer procedure is recommended. A neuromuscular imbalance between a weak Tibialis Posterior tendon and a strong evertor of the foot could be responsible for this condition. Good results are found for this operation which aims to correct this imbalance.
• In a child older than 2 years of age, an extensive release with tendon transfer procedure is proposed. Surgical correction becomes increasingly difficult in older children because of secondary changes of the bone. This procedure resulted as the best for children whose walking and standing potential has been established.

In case of failure of precedent procedures, a bony procedure may be considered. There are good results for children of 4 years and older with these procedures. Every surgery is usually followed by a plaster cast for two to three months. The recovery after surgery takes about 6 months to 1 year to heal completely and to recover completely on a functional level. 

Physical Therapy Management

The aim of Physical therapy is to minimize pain, increase foot flexibility, strengthen weak muscles, train proprioception, and patient education and reassurance. As part of the assessment process, the physiotherapist can assist in evaluating the gait, gross motor skills and the impact the foot deformity has on functional activities. Assess endurance, speed, fatigability, pain and ability to walk on different terrains, with a focus on assessing function, not just structural abnormalities.

Pain management includes rest, activity modification, cryotherapy, massage, and nonsteroidal anti-inflammatory medication. Ultrasound and pulsed electrical stimulation can also be used for pain relief. Electric stimulation will aid blood circulation, promoting healing processes and diminishing discomfort and oedema.

• Flexibility exercises are passive ROM exercise of the ankle and all foot joints; Stretching of gastrocnemius soleus complex and peroneus brevis muscles to facilitate varus and foot adduction; Heel-cord stretch for the Achilles tendon and calf muscles to relief tight heel cord.
• Strengthening Exercises:
  • Strengthening exercises are given to anterior and posterior tibialis muscles and the flexor hallucis longus, Intrinsic, interosseus plantaris muscles, and the abductor hallucis to prevent valgus and flattening of the anterior arch. Arch muscle strengthening exercise with theraband
  • Global activation of the muscles known to support the medial longitudinal arch and the varus with and without resistance.
  • Single leg weight bearing
  • Toe walking

• For Proprioception, Toe and heel walking, Single leg weight bearing, and Descending an inclined surface are exercises that could be prescribed. Also, Toe clawing of towel and pebbles, forefoot standing on a stair, toe extension and toe fanning/spreading, and heel walking are all good exercises to maintain viable foot arches.
• Counselling on proper footwear, recommendation on motion control shoes, orthotics and braces are also needed. Foot orthotics such as shoe inserts are used to support the arch for foot pain secondary to pes planus alone or combination with leg, knee, and back pain.
• Obese and overweight individuals should be counseled on weight loss through exercise and dieting; Possibly refer to a dietician for appropriate insight.
• Other co-morbidities amenable to physiotherapy can also be treated following a proper examination and treatment plan.

• For children with pes planus treatment includes:
  • Advice on appropriate footwear.
  • Advice on appropriate insoles to improve foot position and referral to an podiatrist and an orthotist: in-shoe wedging, foot splints, night stretch splints and cast orthoses. The primary action splint therapy is aimed at stabilising the rear foot and midfoot but not blocking the forefoot. Age-expected foot position, stance and gait are dynamic considerations and need to be well understood.
  • Reducing pain and risk of secondary joint problems. .
  • Providing an exercise program to increase strength in the muscles that stabilise the arches. Examples being: walking up on tip-toes; walking on the heels; activities to improve the dynamic arch such as walking barefoot on soft sand, flexing the toes (eg picking up a tissue with the toes), rolling a ball under the arch of the foot when seared; encouraging climbing and other gross motor activities. Try to engage the family in the exercise therapy eg incorporating games and activities that can be part of child’s day

References