Pes planus refers to a flat foot deformity where the normal medial longitudinal arch is low or absent. It is also sometimes described as fallen arches.
The structure and function of the medial longitudinal arch are influenced by several support systems including the tibialis posterior tendon (which runs behind the medial malleolus), the bones (via shape and position), complex ligamentous supports and the plantar fascia. If any fail, the delicate supporting balance is disturbed and deformity can result.
In infants and toddlers, the longitudinal arch is not developed, and flat feet are normal. As the child begins to walk the arch develops over several years, and by adulthood most people have normal arches. Flat feet may persist from childhood or develop progressively in adults.
In evaluating flat feet, it is important to determine whether the deformity is flexible or rigid. Most flat feet are flexible in that the arch appears when standing on tiptoe or when the great toe is extended toward the ceiling.
Flexible flat feet should be pain-free, with normal mobility, muscle power, and neurological examination. Rigid flat feet are pathological and can be painful, weak and stiff.
Causes of pathological flat feet include tarsal coalition (where two or more foot bones are abnormally fused together), neuropathic conditions such as Charcot’s joint, poliomyelitis, muscular dystrophies, pathological joint laxity, trauma (for example, malunion of some fractures), tendon rupture or joint erosion (for example, due to arthritis). Severe convex flat feet may be due to the congenital vertical talus.
Most flat feet do not cause pain or problems. The commonest presentation of flat feet is from parents reporting the appearance in a child who is otherwise asymptomatic. Other symptoms include frequent sprains or medial foot calluses. On examination, there is usually a larger plantar contact area with a degree of pronation and weight bearing on the inside border of the foot.
There may be an appearance of an abducted forefoot and valgus hindfoot.
The ‘too-many-toes’ sign indicates that when the patient’s stance is observed from behind, there is increased visualization of lateral toes.
Flexible flat feet with no pain and normal examination (especially neurological) need no treatment, although careful shoe selection may be advised and soft arch supports used.
Rigid or painful flat feet require referral for evaluation. The investigation can be directed toward the underlying cause and may include a weight-bearing lateral foot radiograph.
Treatment depends on the underlying cause. Conservative management includes shoe adjustments, specialized exercises or immobilization. Pain is managed with appropriate analgesia.
Operative management is reserved for cases of unsuccessful conservative management. Numerous procedures have been attempted, with no single solution appropriate for all. The goal is to relieve pain and maintain function.
Some operations target the problem, such as removing the fusion between bones in tarsal coalition or debriding or repairing damaged tendons. Advanced cases with disabling symptoms may be treated with a fusion of several joints in a corrected position. This results in some loss of ankle motion, but may improve both pain and function.
Complications of surgery include non-union, malposition and wear and tear at nearby joints.
– Dr. Lackey is a GP and Mr. Sutton is a consultant orthopedic surgeon in Northumberland
PES PLANUS KEY POINTS
– Flat feet should be assessed to determine whether they are flexible or rigid.
– A flexible flat foot will reconstitute an arch on tiptoe standing.
– Many flat feet are painless and flexible and cause no problems. Rigid, painful or neurologically abnormal flat feet should be considered for referral.
– Management can be conservative (such as specialized arch shoe supports) or surgical if conservative measures fail.