Neale's Disorders of the Foot and Ankle E-Book

J. Gordon Burrow, Keith Rome, Nat Padhiar

• Editore: Elsevier
• Anno: 2020
• ISBN:
  9780702065040
• Edizione: 9
• Argomento: Medicina
• Categoria: Teoria, pratica e riferimenti medici

Now in its 9th edition and fully updated to reflect 21st century podiatric practice Neale's Disorders of the Foot and Ankle continues to be essential reading for students entering the profession, qualified podiatrists and other health care professionals interested in the foot. Written by a renowned team of expert editors and international contributors it gives up-to-date, evidence-based content of the highest quality. Podiatric students should find everything they need within its covers to pass their exams, whilst qualified clinicians will find it a useful reference during their daily practice. All the common conditions encountered in day-to-day podiatric practice are reviewed and their diagnoses and management described along with areas of related therapeutics.

• Fully illustrated in colour throughout including over 500 photographs and illustrations.
• Complete coverage of podiatric conditions, including Circulatory Disorders, Rheumatic Diseases, Imaging, Foot Orthoses, Pediatric Podiatry, Podiatric Sports Medicine, Podiatric Surgery, Leprosy and Tropical Medicine.
• Brand new chapters covering key topics including Complimentary and Integrated Medicine, Forensic and Legal Medicine, Evidence Based Practice in Podiatry and Pharmacology & Therapeutics.

1

Structure and Function of the Foot

James Watkins

1. Introduction,
2. Skeleton of the Foot,
3. Movements of the Ankle and Foot,
   1. Ankle Joint,
   2. Subtalar Joint,
   3. Pronation and Supination,
4. Arches of the Feet,
   1. Passive Arch Support,
   2. Active Arch Support,
5. The Windlass Mechanism of the Foot,
   1. Interaction of the Windlass and Arch-Spring Mechanisms,
   2. Hallux Valgus,
6. Structural Adaptation of the Musculoskeletal System,
   1. Structural Adaptation in Bone,
   2. The Chondral Modelling Phenomenon,
   3. Modelling of Metaphyses and Epiphyses,
   4. Modelling of Articular Surfaces,

Keywords

Ankle joint

Arch support mechanisms

Midtarsal joint

Modelling

Pronation

Rearfoot complex

Structural adaptation

Subtalar joint

Supination

Windlass

Introduction

In weight-bearing activities, such as walking, running, jumping and landing, the main function of the musculoskeletal system is to generate and transmit internal forces to create the ground reaction forces necessary to maintain upright posture, transport the body and manipulate objects, often simultaneously. The ground reaction forces act on the feet; in general, the greater the speed of movement and change in speed of movement, the greater the magnitude of the ground reaction forces (Nigg et al 1981, Voloshin 2000). The greater the ground reaction forces, the greater the associated muscle–tendon forces and joint reaction forces. For example, when running at moderate speed (4–5 m/s), peak ground reaction forces will be in the region of 2.5–3.0 body weight (BW). However, the associated Achilles tendon force and ankle joint reaction force will be in the region of 6–8 BW and 10–14 BW, respectively (Scott & Winter 1988).

In dynamic situations the foot is required to act as both a shock absorber, to cushion the impact of contact of the foot with the ground, and as a propulsive mechanism to propel the body in the desired direction (Blackwood et al 2005). The foot often performs these functions on a variety of support surfaces. Whereas floor surfaces tend to be firm and level, there are many other situations, such as in cross-country running, where the surface of the ground is neither firm nor level, but continually changes in terms of slope, evenness and hardness. The ability of the foot to function effectively in relation to such diverse environmental constraints is due to its structure, in particular to its arched shape and complex movement capability (Holowka & Lieberman 2018).

Skeleton of the Foot

The foot consists of seven tarsals, five metatarsals and 14 phalanges (Fig. 1.1). The tarsals constitute the tarsus, which forms the rear part of the foot. The foot articulates with the lower leg at the ankle joint (talocrural joint), i.e. the joint between the tibia, fibula and talus. The talus, the second largest tarsal, has a convex pulley-shaped articular surface on its superior aspect, called the trochlear surface of the talus, which articulates with the trochlear surface of the tibia. The trochlear surface of the talus is continuous with articular surfaces on its lateral and medial aspects that articulate with the lateral malleolus and medial malleolus, respectively.

The inferior aspect of the talus articulates with the anterior half of the superior aspect of the calcaneus by means of two or, in some cases, three articular facets, which together constitute the subtalar joint (talocalcaneal joint). The anterior aspect (head) of the talus articulates with the posterior aspect of the navicular, on the medial aspect of the foot, to form the talonavicular joint. The anterior aspect of the calcaneus articulates with the posterior aspect of the cuboid, on the lateral aspect of the foot, to form the calcaneocuboid joint. The calcaneocuboid and talonavicular joints are continuous with each other and constitute the midtarsal joint, also referred to as the transverse tarsal joint (Czerniecki 1988). The anterior aspect of the navicular articulates with the posterior aspects of the three cuneiforms (medial, middle, lateral), which lie side by side and articulate with each other. The posterior-superior-lateral aspect of the lateral cuneiform articulates with the superior-medial aspect of the cuboid. The anterior aspects of the medial, middle and lateral cuneiforms articulate with the bases of the first, second and third metatarsals, respectively. The anterior aspect of the cuboid articulates with the bases of the fourth and fifth metatarsals. The joints between the four anterior tarsals and the metatarsals are referred to as the tarsometatarsal joints. The lateral four metatarsals are similar in length, but tend to increase in girth from the second to the fifth. In comparison, the first metatarsal is usually shorter, but has a greater girth than the other four. The metatarsals are collectively referred to as the metatarsus. The heads of the metatarsals articulate with the proximal phalanges of the toes to form the metatarsophalangeal (MTP) joints. The great toe (also referred to as the big toe or the hallux) is composed of two phalanges and each of the other toes is composed of three phalanges. The phalanges of the toes become progressively shorter from proximal to distal.

Fig. 1.1 The bones of the right foot. (A) Medial aspect. (B) Lateral aspect. (C) Superior aspect.

In addition to the tarsals, metatarsals and phalanges, a number of small accessory bones and sesamoid bones occur during fetal life (Anwar et al 2005, Williams et al 1995 ). There are normally about 10 irregular-shaped accessory bones distributed around the tarsus; most of these bones fuse with one of the tarsal bones prior to skeletal maturity. There are normally about 12 sesamoid (seed-shaped) bones. Each sesamoid bone is partially embedded in a tendon or ligament, with the free surface of the bone forming a synovial joint with a bone over which the tendon or ligament slides during normal function. In addition to preventing the tendon or ligament from rubbing on the adjacent bone, sesamoid bones tend to increase the mechanical efficiency (leverage) of the associated musculotendinous unit or ligament. The two most important sesamoid bones of the foot, which contribute significantly to stabilising the foot during propulsion (see the section on the windlass mechanism later in this chapter), are the sesamoids in the plantar aponeurosis (see later section on arches of the foot) beneath the base of the first MTP joint; the medial sesamoid is shown in Fig. 1.1A.

Movements of the Ankle and Foot

Many of the 26 bones in each foot articulate with two or more other bones such that there are approximately 40 joints in each foot. Consequently, most movements of the foot involve a large number of joints, and the movement of individual joints in each movement is diffi...