Chapter 25. Acquired foot deformities

Foot deformities are the most common group of orthopedic diseases with a diverse etiology. Depending on the causes, among the acquired deformities, post-traumatic (after injuries of the foot or ankle joint), static deformities (the result of overload) and those developed as a result of various musculoskeletal system diseases are distinguished.

Anatomical and physiological features

The foot plays a leading role in providing human ambulation - a cyclic motor act carried out as a result of complex coordinated activity of the trunk and extremity skeletal muscles. The main ambulation element is a step. In this case, two periods alternate: support (during the contact of the foot with the support, its rolling occurs, as well as toeing off and forward body movement) and transfer (when the free leg is brought forward, i.e., the next step is taken).

Foot structure

The foot has 3 sections: tarsus, metatarsus, and toes.

• tarsus consists of 7 short cancellous bones, which are arranged in 2 rows - anterior (cuboid, navicular and 3 cuneiform bones) and posterior (talus and calcaneus);
• metatarsus consists of 5 metatarsal (short tubular) bones, the bases of which form joints with cuboid and cuneiform bones;
• toes consist of 3 phalanges: proximal, middle and distal, except for the 1st toe ("hallux"), which consists only of the proximal and distal phalanges.

The plantar surface of the foot is abundantly equipped with receptors, which provide coordination of muscle load when standing and walking. The foot constantly "tracks" terrain irregularities to maintain control over the support. These reaction processes occur at a high speed and are provided through afferent-efferent nervous connections.

Foot functions

There are four main functions of the foot:

• support - allows to carry the body weight during bipedal locomotion;
• spring - manifests as elastic deformity of the foot arches under varying vertical loads;
• balance - serves for maintaining an erect posture and provides ambulation;
• jumping - provides motion by means of posterior and anterior jogs.

Foot arches

Arches are the most important structural elements of the foot, which are crucial for its functioning.

There are longitudinal (external and internal) and transverse arches (Fig. 25.1).

• The external longitudinal (supporting) arch is formed by the calcaneus, cuboid, IV and V metatarsal bones; it is in direct contact with the support surface, the foot is rolled through it during the step.
• The internal longitudinal arch is formed by a talus, navicular, 3 cuneiform, and 3 metatarsal bones; it is not in contact with the support surface and performs mainly a spring function.
• The transverse arch is formed by the heads of metatarsal bones arranged in an arch.

Fig. 25.1. Foot arches

Static foot deformities

Causes and classification

The cause of static deformities is chronic overload of the lower extremities, which may occur:

• under usual load, when the tissues forming the feet are impaired due to internal and external causes and even the usual load becomes excessive for them;
• with a significant additional load associated with an increase in human body weight, hard physical work involving heavy lifting, prolonged standing on the feet, when the increased load exceeds compensatory capabilities and becomes excessive.

Static foot deformities include:

• flat foot - longitudinal, transverse and combined (their combination);
• deformities of the toes - valgus deviation of the 1st toe (hallux valgus), varus deviation of the 5th toe, hammer toes;
• fibro-osseous over-growth of the I and V metatarsal bone heads.

Diagnosis

Early diagnosis based on relatively simple and objective research methods is of great importance.

In addition to clinical examination (reveal of complaints, examination at rest and under load, palpation, determination of the active and passive motion range), instrumental examinations are used.

Plantography

The easiest way to conduct plantography is to obtain a footprint (plantogram) on paper; however, there are also specific devices that allow to obtain such an imprint immediately in a digital version using computer technology. On the plantogram, a straight line is drawn through the center of the calcaneus imprint and between the 3th and 4th toe imprints, indicatively separating the external longitudinal foot arch. If the shaded area does not cross this line in the middle of the imprint, there is no height loss in the longitudinal foot arch. The ratio of the shaded area (the width of the foot contact with the support surface) to the set width of the external longitudinal arch characterizes the flat foot severity (Fig. 25.2):

• normal foot - 0.51-1.10;
• lowered arch - 1.11-1.20;
• stage I flat foot - 1.21-1.30;
• stage II flat foot - 1.31-1.50;
• stage III flat foot >1.51.

Fig. 25.2. Plantography: normal foot (a) and stage I (b), II (c) and III (d) flat foot

Podometry

Podometric index (percentage ratio of foot height to its length) is a parameter proposed in 1926 by M.O. Friedland, which consists in determining the ratio of the foot height (bridge) to its length. The foot height is measured as the distance from the support to the upper surface of the navicular bone, which is palpable in approximately a finger distance toward the front of the ankle joint. The foot length is measured as the distance from the tip of the 1st toe to the rear edge of the heel (Fig. 25.3). After that, the foot height is divided by the length, and the result is multiplied by 100. Normally, the podometric index is in the range from 31 to 29%. An index from 29 to 27% indicates a lowered foot arch (flat foot), below 25% - substantial flat foot.

Fig. 25.3. Measurement of the podometric index: h - foot height, l - foot length