Anatomy, Bony Pelvis and Lower Limb, Calcaneus

Article Author:
Marco Gupton
Article Editor:
Robert Terreberry
Updated:
9/17/2018 1:57:17 PM
PubMed Link:
Anatomy, Bony Pelvis and Lower Limb, Calcaneus

Introduction

The calcaneus bone is one of the 7 articulating bones that make up the tarsus. The calcaneus is located in the hindfoot with the talus and is the largest bone of the foot. It is commonly referred to as the heel and primarily articulates with the talus and cuboid bones. Numerous ligaments and muscles attach to the calcaneus and help with its role in human bipedal biomechanics. [1],[2]

Structure and Function

The calcaneus serves as an attachment point for the tendocalcaneous (Achilles) tendon which produces aids in plantar flexion of the foot vital for standing, walking, running, and jumping. The calcaneus also serves as an attachment point for muscles that move the toes. The calcaneus and the talus make up the subtalar joint or the talocalcaneal joint which allows for inversion, eversion, dorsiflexion, and plantarflexion of the foot. The calcaneus has a number of joint stabilizing ligaments attached to it, such as the calcaneofibular, talocalcaneal, calcaneocuboid, and calcaneonavicular ligaments. The plantar aponeurosis and long plantar ligament support the arch of the foot and attach to the calcaneus as well. [1],[2]

Embryology

Endochondral ossification forms the calcaneus, and its ossification center begins to form during weeks 4 to 7 of development.[3]

Blood Supply and Lymphatics

The calcaneus is surrounded by and receives its blood supply from a superficial network of arteries called the calcaneal anastomosis, which is formed by branches of the posterior tibial and fibular arteries. Much of the lymphatic flow follows the vasculature and flows up the leg through the popliteal and inguinal lymph nodes before passing through the thoracic duct. [1],[2]

Nerves

The calcaneus receives its nerve supply from branches of the tibial and sural nerves.[1],[2]

Muscles

There are 3 muscles that combine to form the Achilles tendon and attach on the calcaneal tubercle. These muscles are the primary plantar flexors and consist of the gastrocnemius, soleus, and plantaris. There are 6 muscles that originate on portions of the calcaneus and provide movement to the toes. The extensor digitorum brevis originates on the dorsal side of the calcaneus and provides extension of the 2 to 4 digits. The abductor hallucis originates on the medial process of calcaneal tuberosity and abducts the first digit. The extensor hallucis brevis originates on the dorsal aspect of the calcaneus and extends the first digit. The abductor digiti minimi originates on the calcaneal tubercle and provides flexion and extension of the fifth toe. The flexor digitorum brevis originates on the calcaneal tubercle and helps provide flexion to the 2 to 4 digits. The quadratus plantae originates on the lateral and medial processes of the calcaneus and helps provide flexion at the distal interphalangeal (DIP) joint. [1],[2]

Physiologic Variants

A Haglund deformity is a bony exostosis that extends from the posterior superior calcaneus where the Achilles attaches. The etiology of the condition is unknown but hypothesized causes are Achilles tendonitis, high arched feet, improper footwear, and other hereditary factors. It most commonly affects middle-aged males and females and is usually bilateral. Symptoms include pain, erythema, and other signs of inflammation. The diagnosis can be made clinically with radiographs providing further support. Treatment is usually conservative and involves NSAIDs, Achilles stretching, heel lifts, appropriate footwear, and orthotics. [4],[5]

Surgical Considerations

A Haglund deformity that has failed conservative treatment can be treated surgically by removing the bony exostosis.[5]

Plantar fasciitis that has failed conservative treatment can be treated with a surgical plantar fasciotomy. Minimally invasive endoscopic approaches have been introduced in the last decade, but there is a limited amount of literature with documented results, although most of the existing literature classifies the treatment as highly effective.[6]

Fractures of the calcaneus are relatively common and usually occur due to a fall from a height or a motor vehicle accident. Diagnosis can be made with x-ray or CT scan. Treatment depends on the extent and type of fracture. The Sanders classification system is often used to categorize intraarticular fractures of the calcaneus into 4 types with the II, III, and IV types usually requiring surgery. Fractures that are open, significantly displaced or comminuted also require surgical fixation. Regardless of the treatment, almost all calcaneal fractures are initially treated with a non-weight bearing status. [7],[8],[9]

Clinical Significance

Plantar fasciitis is a very prevalent condition that involves a noninflammatory structural breakdown of the connective tissue that makes up the plantar aponeurosis or fascia of the foot. The plantar aponeurosis provides support to the arch of the foot so anything that puts abnormal stress on, alters the biomechanics of, or changes the structure of this arch is a potential cause. Overuse in runners is a very common cause, but other causes can include obesity, tight Achilles, and a sudden increase in activity. Heel spurs are often found in association with plantar fasciitis, but it is unclear if they affect the pathophysiology of the condition. The condition consists of sharp pain and discomfort along the plantar surface of the foot and especially over the tuberosity of the calcaneus. It is more commonly unilateral and is worst when walking after long periods of rest. If the condition goes untreated with continued activity, then the plantar fascia can rupture and require extensive treatment. The diagnosis is usually made clinically although imaging modalities such as x-ray and ultrasound can be helpful. Treatment is primarily conservative with NSAIDs, rest, stretching, physical therapy, steroid injections and a number of other non-surgical approaches like extracorporeal shockwave therapy, iontophoresis, and platelet-rich plasma. [10],[11],[12],[13]

Sever's disease involves inflammation of the growth plate in the heels of growing children. It is considered a calcaneal apophysitis caused by repetitive stress. It is thought that children and adolescents get the condition because of the difference in bone growth rate between the calcaneus and the leg bones. The condition presents as sharp or achy pain in the heel that is aggravated by pressure during physical activity. As a result, the condition occurs in very active adolescents. Treatment consist of rest, ice, NSAIDs, stretching, physical therapy, heel inserts, and the condition usually resolves when the bone has completed growth. [14],[15],[16]

Other Issues

As stated previously plantar fasciitis is a very prevalent condition with a number of interesting non-surgical treatments. Extracorporeal shockwave therapy consists of high energy acoustic shockwaves being directed at the sight of injury to disrupt tissue in a manner that increases blood flow and promotes healing. There are very few if any side effects of the treatment and it is a simple, relatively fast, and a much less painful procedure when compared to surgery. The literature does seem to show benefits in the treatment of plantar fasciitis, but the extent is unclear. [17],[18]

Iontophoresis is a process of delivering anti-inflammatory drugs through the skin. A topical medication is applied to the skin, and then electrodes are attached to the skin over the medication, and electrical current is used to drive the medicine through the skin to the inflamed or injured tissue. Similar to shockwave therapy the literature does seem to show benefits in the treatment of plantar fasciitis, but the extent is unclear.[19]

Platelet-rich plasma (PRP) is a relatively new controversial treatment being investigated for a number of different conditions. The process involves centrifuging whole blood to remove the red blood cells and being left with PRP that is thought to contain concentrated growth factors and other growth-promoting cytokines. The concentrated growth factors are supposed to promote better and faster healing. The PRP is injected into the injury site in a series of injections. Data is limited and more research will have to be produced before any benefit in the treatment of plantar fasciitis can be confirmed. [20],[21]