Pes Planus

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Definition/Description

Pronated-Kids-Feet

Pes planus is fairly common in infants, as they are prone to absent arches secondary to ligamentous laxity and lack of neuromuscular control. Additionally infants have a fat pad under the medial longitudinal arch(MLA), procting the arch in early childhood, making the arch appear flatter. Most children by age 5 o6 have developed normal arches. The majority cases of pes planus in children are flexible ie a normal arch without bearing weight, which disappears with weight-bearing. Only a few children fail to develop a normal arch by adulthood. Obesity in children is a risk factor for MLA to collapse in early childhood, as are gender(female), cerebral palsy and syndrome of Down.

Epidemiology/Etiology

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 and balance improves as 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.Over time it may lead to an altered walking pattern, clumsiness, limping after long walks, and pain in the foot, knees or hips. Beside the aforementioned causes for pes valgus, tarsal coalitions, peroneal spasm and vertical talus are common aetiologies during the childhood. It is therefore important that appropriate treatment starts at an early age.

Physiological causes

The bony arch of the foot is potentially unstable. It is bound together by ligaments, but these are capable of resisting short term stress only; indeed, their main function is to act as sensory end organs, and when they are stretched appropriate muscles are reflexly 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 psychological fault may lie in the muscle itself or in its nervous control.

Inadequate nervous control: We are not here concerned with the gross and obvious inadequacies which result from poliomyelitis or spina bifida, for in these conditions flat foot is overshadowed by other disabilities. An example of inadequate nervous control is infantile flat foot. 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.

Inadequate muscles: After illness or enforced recumbence 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.

Clinically Relevant Anatomy

Foot Arches Tripod

The classification of the pes valgus 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 (cf. Jack’s test)

Rigid pes valgus, also called congenital pes planovalgus (convex), is often a result of tarsal coalition, which is typically characterized as a painful unilateral or bilateral deformity.

See Arches of the Foot

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.

Physical Therapy Management

In congenital pes valgus, surgery is most recommended, but conservative treatment is also available. For children with pes valgus it usually consists of:

• 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 advice on exercise to help stretch tight muscles and strengthen weak areas to aid development of correct foot posture.  

Acquired pes valgus because of a tibialis posterior dysfunction is treated according to different stages of this pathology. In stage 1 and 2 the foot is still flexible, while in stage 3 and 4 the foot becomes more rigid.

Stage 1 and 2

Possible inflammation surrounding the sheath of the tibialis posterior tendon should be dealt with before the chronic aspect is treated. As therapy it is recommended to be immobilised during 4 to 8 weeks in a plaster cast below the knee or removable boot as to control accompanying inflammation. In conjunction Rice and anti-inflammatories can be used. Footwear has an important role, and patients should be encouraged to wear flat lace-up shoes or lace-up boots, which accommodate orthoses. Stage 1 patients may be able to manage with an off the shelf orthotic or may try first a laced canvas ankle brace. The various casted and semirigid orthoses support the medial longitudinal arch of the foot and either hold the heel in a neutral alignment in a stage 1 patient. In stage 2 it corrects the outward bent heel to a neutral alignment. This therapy has several functions, those are to alleviate stress on the tibialis posterior, to make gait more efficient by holding the hindfoot fixed and to prevent progression of the deformity.

Stage 3 and 4

In this stage the inflammation is a less common feature. The treatment revolves around accommodating the deformity, rather than attempting to correct it, with a customised moulded rigid orthoses, used in conjunction with appropriate footwear.

Characteristics/Clinical Presentation

Patients may complain of medial ankle pain caused by posterior tibial tenosynovitis and/or tendinosis. Further in the deformity progress, patients commonly experience lateral foot pain, arising at the angle of Gissane from talocalcaneal impingement or in more rare cases from fibular abutment against the calcaneus. They may also experience pain on palpation of arthritic joints.

Differential Diagnosis

• Chronic ankle sprain
• Tarsometatarsal osteoarthritis
• Charcot arthropathy
• Inflammatory arthritis 
• Unrecognized tarsal coalition
• Neuromuscular disease 

Examination

During gait, it must be noted whether the heel touches the ground and what degree normal toe-off is possible.

The position of the heel is examined from behind, patient having heel down as far as possible. If pain occurs that must be noted. Also the joint motion and position of the subtalar joint must be evaluated with the heel in everted and inverted position. The affected heel will stand in a valgus position, and flattening of the medial longitudinal arch, forefoot abduction is visible. The tightness of the Achilles tendon is assessed with forced dorsiflexion, this way we can evaluate tightness and the flexibility of the foot.

Also the area posterior to the medial malleolus should be examined for swelling and palpation along the distal portion of the posterior tibial tendon (PTT) is highly suggestive of PTT degeneration.

The inability to perform a single heel rise is suggestive of PTT insufficiency. 

Medical Management

Researchers define different possibilities of surgery depending on the type of pes valgus. Congenital pes valgus is usually treated at a young age, while acquired pes valgus is being treated later on when diagnosed. 

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 they recommend an extensive release with lengthening of the Achilles tendon and fixation procedure. 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 they recommend an extensive release with tendon transfer procedure. 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 they recommend an extensive release with tendon transfer procedure. 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.

Only in extreme cases and when the child is older than 4 years of age a subtalar or triple arthrodesis may be considered. In acquired pes valgus they only apply surgery if all conservative therapies are inefficient, in certain cases they define different stages. Every stage has a different surgical therapy.

Stage 1 A calcaneal osteotomy is performed with the aim to correct the underlying foot deformity and to attempt to preserve the foot’s function in conjunction with either debridement of the tendon or tendon transfer.

Stage 2 This treatment entails a tendon transfer in combination with corrective osteotomy. The rationale behind this surgery is that osteotomy is required to correct the bony architecture of the foot in order to optimise the biomechanics of the reconstructed tibialis posterior tendon. Various osteotomies of the calcaneus can correct the bony alignment and may augment with a lengthening of the tibialis anterior tendon. The tendons used to reconstruct the tibialis posterior are either a split tibialis anterior tendon or a flexor digitorum longus.

Stage 3 The goal of surgical treatment is to correct the deformity and alleviate pain trough a triple arthrodesis of the subtalar, calcaneocuboid, and talonavicular articulations.

Stage 4 In this stage there are additional degenerative changes present in the ankle joint. Surgery consists usually of a salvage treatment with a pantalar arthrodesis of the ankle (the subtalar, calcaneocuboid and talonavicular articulations).

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.