Pes Planus

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Definition/Description

This text describes pes valgus in children. It is a problem commonly encountered in paediatric orthopaedics and is generally considered as caused by the collapse of the medial longitudinal arch in the foot. It was found that 42% of children between 3 and 6 years which normal weight develop pes valgus. Age, gender, obesity, cerebral palsy, syndrome of Down, … are known risk factors for the development of growth and musculoskeletal changes. Almost 20% of the adult population has pes valgus.;

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.

Middle aged women are most commonly affected, and the prevalence is known to increase with age. Pes planus, hypertension, diabetes mellitus, steroid injection around the tendon, high impact sports, Obesity, and seronegative arthropathies have all been identified as risk factors.

Anatomical Causes

There are 4 groups of anatomical peculiarities which predispose to flat foot. The inheritance of many of these peculiarities explains the frequent familial incidence of the disorder.

1. The lower limb may be wrongly ‘set’ on the trunk. The entire limb may be externally rotated or the leg only may be rotated from the knee downwards. In either case, the line of body weight falls too far medially. As a result, when the body moves forward in walking the force of the body weight imposes considerable strain upon the apex of the arch and tends to topple over it.
2. The leg may be wrongly ‘set’ on the thigh, for example in knock-knees. Here, too, as in external rotation, the line of the body weight falls to medially. The combination of knock-knees and flat foot is common in children aged 2 – 6 years.
3. The foot may be wrongly ‘set’ on the leg. A short calf muscle or Achilles tendon prevents adequate dorsiflexion of the ankle (unless the knee is bent). In walking, the knee is straight and, as the front leg swings forward, the back leg must dorsiflex considerably at the ankle. If adequate dorsiflexion is hindered by a tight calf the Achilles tendon bowstrings across the outer side; this is accompanied by a topple of the arch to the medial side.
4. The forefoot may be wrongly ‘set’ on the hind foot. The forefoot may be varus, with the soles of the feet tending to face each other; this is sometimes due to a relatively short tibialis anticus muscle, and sometimes to a short or elevated first metatarsal. Whatever the cause, as the weight comes on the forefoot in walking the first metatarsal is forced down from its elevated position on to the ground; the apex of the arch is pushed downwards and inwards and flatfoot results. There has been emphasized the varus forefoot is commoner than generally supposed, but the deformity may not be recognized unless the foot is correctly examined with the heel held square. Once weight is on the foot the obvious deformity is the valgus heel.

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.

1. 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.

1. 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 the fat middle aged house wife whose increase weight imposes great strain upon the arch. Moreover, a housewife stands still for long periods of time, for example, when washing dishes. 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

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. In flexible pas valgus, also called congenital pes cancaneovalgus, the foot lies against the lower leg, or can be extended without resistance until it impinges against the leg. In contrast to the congenital pes planovalgus, the foot can be restored to a normal position without great resistance. Plantar flexion is occasionally is reduced.

The skeletal framework of each foot is formed by 28 bones: 7 tarsals, 5 metatarsals, 14 phalanges and 2 sesamoid bones. From the functional point of view, the feet can be divided in three parts: the hind foot, formed by talus and calcaneus, the midfoot, consisting of navicular, cuboid and three cuneiform bones, and the fore- foot, formed by metatarsals and phalanges. The talus, calcaneus, cuboid, navicular and three cuneiform bones form the tarsus, comprising the hind-foot and mid-foot.

The hind foot extends from the calcaneal tuberosity to the transverse tarsal joint (Chopart’s joint); the latter consists of the talonavicular part of talocalcaneonavicular joint and the calcaneocuboid joint. The anterior limit can be traced on the surface along the S-shaped line (medially convex and laterally concave) connecting the tuberosity of the navicular bone (palpable infero-anteriorly to the tip of the medial malleolus) with the point located half-way between the lateral malleolus and the tuberosity at the basis of the 5th metatarsal. The movements of the mid-foot on the hind foot at the transverse tarsal joint augment the inversion (turning the sole towards the median plane) and eversion (turning the sole laterally), occurring mostly at the subtalar joint. The anterior limit of the mid-foot follows the tarsometatarsal joints (Lisfranc’s joint), traced on the surface by the slightly convex line between the tuberosity of the 1st and the prominent tuberosity of the 5th metatarsal bone. These joints allow only slight movement of sliding.

The shape of the tarsal and metatarsal bones accounts for the presence of longitudinal and transverse arches of the foot. The medial longitudinal arch extends between the calcaneus and talus (posterior pillar), and first three metatarsal and three cuneiform bones (anterior pillar). The keystone, corresponding to the talar head, is 15-18 mm above the ground. The lateral longitudinal arch is much flatter and rests on the ground in the weight bearing feet. It is composed of the calcaneus (posterior pillar), the lateral two metatarsals (anterior pillar) and the cuboid bone (keystone), which may be 3-5 mm from the ground in the non-weight bearing feet. The transverse arch runs from side to side at the tarsometatarsal joint level. Its medial pillar is represented by the medial cuneiform and the basis of the 1st metatarsal bone, the lateral pillar is formed by the lateral cuneiform, cuboid and the bases of the 3rd-5th metatarsals; the keystone corresponds to the intermediate cuneiform, which can be 18-20 mm above the ground.

The arches are passively maintained by plantar aponeurosis and ligaments (long and short plantar ligament, plantar calcaneonavicular ligament) and dynamically supported by tendons of extrinsic muscles (tibialis anterior, flexor hallucis longus and brevis, flexor digitorum longus and brevis for the longitudinal arch; peroneus longus, tibialis posterior for the transverse arch) and by intrinsic muscles that run between the pillars of the arches. These structures act together as a unit to support and distribute appropriately the body weight during walking.

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

X-rays are used to categorise the feet as having normal, slightly flat and moderate arches.

• Foot-posture index (FPI-6)

It is based on six specific criteria:

1. Talar head palpation
2. Curves above and below lateral malleolus
3. Inversion/eversion of the calcaneus
4. Bulge in the region of the talonavicular joint (TNJ)
5. Congruence of medial longitudinal arch
6. Abduction/adduction of the forefoot en rear foot

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. 

Resources

https://thrive.kaiserpermanente.org

http://jbjs.org/content/21/1/79

http://www.bcu.ac.uk/cmsproxyimage?path=/_media/docs/cd006311.pdf