Anatomy of the bones of the foot, part 1

Triangular bone syndrome (TCS) is characterized by pain in the posterior aspect of the ankle and decreased range of motion in plantar flexion. Together with the surrounding soft tissue, the triangular bone can become pinched between the tibia, talus, and calcaneus, which can lead to inflammation of the involved structures.

TTS may also be called talar compression syndrome or posterior tibiotalar impingement syndrome.

T1-weighted MR image shows the nutcracker phenomenon. The triangular bone, together with the surrounding soft tissues, is sandwiched between the talus, calcaneus and tibia.

Clinically Relevant Anatomy

At the stage of human embryological development, the body and the posterior process of the talus are separate centers of ossification. Between 7 and 13 years of life, the posterior process of the talus forms as a separate bone (triangular bone). However, within a year after its appearance, it fuses with the talus again (in 7% of people this does not happen). It can be on one or both sides. Has smooth or jagged edges. Size is less than 1cm but may vary.

Very soon there will be a seminar by Georgy Temichev “Diagnostics and therapy of problems of the lower extremities. Analysis of walking and running." Find out more...

This bone usually has three angles, anterior, inferior and posterior surfaces. The anterior surface has a cartilaginous connection with the lateral tubercle through cartilaginous synchondrosis. The lower part can articulate with the heel bone. The posterior surface does not articulate with anything, but is used as a point of attachment for ligamentous capsule structures. A triangular bone can also be round or oval in shape.

Superior projection of the talus

The flexor pollicis longus tendon is located medial to the triangular bone in the groove between the medial and lateral tubercles.

Functionality and anatomy

The complexity of this bone and its multiple connections with the rest of the foot and lower leg determine its importance and versatility.

Functional purpose

The role of the ram is to distribute the weight of the human body and additional loads that arise during movement on the foot, simultaneously in different directions.
One direction is to the heel, through the posterior subtalar joint located below, and the second is to the arch of the foot forward and inward, through the talonavicular joint; the third - to the arch of the foot forward, outside, through the anterior talocalcaneal joint. Uniform distribution of compression, multidirectional load, good shock absorption give the foot the following necessary for upright walking:

sustainability;
stability combined with great mobility;
optimal balance between the possibility of active movement of large amplitude and reliability of support.

Epidemiology/etiology

There are 3 mechanisms for the formation of triangular bone:

Incorrect fusion in ossification centers.
Fracture of the posterior edge of the tibia.
Fracture of the posterior process of the talus.

The presence of TCS can be caused by overuse or injury (for example, in ballet dancers or track and field athletes). Strong plantar flexion, which occurs in pointe or toe positions, as well as when running downhill (in athletes), puts pressure on the back of the ankle joint. The triangular bone can be displaced during forced plantar flexion due to injury.

The soft tissue structures, including the ankle capsule and surrounding ligaments, may be stressed by such movements/loads, painfully increasing in size (hypertrophy).

Ankle pain

General information

The ankle joint (ankle) consists of three bones (tibia, fibula and talus), which are connected by tendons, forming a trochlear joint.
Muscle groups in the joint area provide movement in it, mainly dorsal and plantar flexion. The bone stability of the joint is provided by the talus, located between the tibia. The talus is wider anteriorly than posteriorly, providing a secure connection to the distal tibia and both ankles.

In dorsiflexion, the wide part of the talus fits into the slightly oval notch of the tibia. This tight connection allows the ankles of the lower leg to bear the significant stress that occurs during rotational movements of the foot. During plantar flexion, the narrow posterior part of the talus occupies the intermalleolar notch, which allows for mobility in the joint and eliminates the occurrence of damage due to rotational forces.

Ankle ligaments. The bony structures of the ankle are connected by three sets of ligaments. The internal collateral, or deltoid, ligament is a thick, triangular band that provides medial support to the ankle. The ligament has superficial and deep layers of fibers originating from the wide, short and strong medial malleolus. The superficial layer runs in the sagittal plane and attaches to the scaphoid and talus bones, while the deep layer runs more horizontally and attaches to the medial surface of the talus.

The ankle joint is externally strengthened by the anterior and posterior talofibular ligaments, as well as the calcaneofibular ligament. Running along the lateral malleolus, these ligaments prevent lateral displacement of the talus. In the lower third of the tibia, the tibias are connected to each other by the syndesmosis, the anterior and posterior tibiofibular ligaments and the posterior transverse ligament.

The anterior and posterior tibiofibular ligaments contain fibers that run between the edges of the tibia bones anteriorly and posteriorly. The inferior transverse ligament is a group of fibers that support the posteroinferior aspect of the ankle. Finally, the interosseous ligament is simply the lower portion of the interosseous membrane. It ensures the strength of the tibiofibular joint.

The blood supply to the ankle and foot area is carried out by vessels from the external iliac artery basin - the anterior and posterior tibial and peroneal arteries. Innervation is carried out by the branches of the sciatic nerve.

The ankle joint is a ring made up of the tibia and talus bones, connected to each other by three large groups of ligaments. All ankle injuries are determined by pathological displacement of the talus, enclosed in the articular fork.

Most often, ankle pain is caused by one of two reasons: either arthritis or subluxation of the joint with subsequent development of arthrosis. It is quite simple to distinguish one from the other: arthritic inflammation of the ankle usually occurs against the background of inflammation of other joints. The ankle joint itself becomes inflamed and swollen, as they say, out of the blue, without prior trauma. Ankle pain due to arthritis is more pronounced at night (at about 3-4 am), and during the day when walking the pain is felt, but less intensely.

Causes of ankle pain

The largest group of trauma patients suffers from foot injuries. In descending order of frequency, the victims are distributed as follows:

ankle sprain;
fractures of the lateral malleolus;
fractures of the base of the fifth metatarsal bone;
fractures of both ankles and the posterior edge of the tibia;
fractures of the phalanges of the toes of the metatarsal bones;
calcaneal fractures;
foot sprains.

Mechanism of injury: sudden twisting of the foot inward or outward, a fall from a height onto the heels, a fall of heavy objects on the foot (fractures of the metatarsal bones, phalanges, fingers, feet, etc.).

Symptoms of an ankle injury:

Ankle sprain. Swelling quickly develops due to hemorrhage (on the inside or outside of the joint, sharp pain in the ankle during supination (turning the foot inward). When palpating under the ankles - sharp pain. If, simultaneously with a sprain, a fracture of the fifth metatarsal bone occurs, then sharp pain is detected on palpation its foundations.
Fracture of the outer ankle. The clinical picture is the same as for a sprained ankle, but upon palpation, pain is detected not only below the ankle, but also in the area of the ankle itself.
Fracture of both ankles with subluxation of the foot. The joint is sharply increased in volume, attempting to move causes significant pain. The foot is displaced outward, inward, or posteriorly, depending on the type of subluxation. Patients may feel crepitus of the fragments. Palpation of the outer and inner ankles reveals pain in the ankle, and a defect between bone fragments is often determined.
Heel bone fracture. The heel is sharply thickened and turned outward (pronated). In a displaced fracture, the arch of the foot is also flattened.
The patient cannot stand on his leg due to severe pain in the ankle. Putting pressure on the heel causes sharp pain. Movement in the ankle is limited due to heel pain, but is possible.
A fracture of the diaphysis of the metatarsal bones causes the formation of an extensive hematoma on the dorsum of the foot (“foot like a pillow”), flattening of the longitudinal arch of the foot; There is a sharp pain in the ankle with a load on the forefoot and upon palpation.
Dislocations and subluxations in the ankle are combined with fractures of the ankles; dislocation can occur at the junction of the talus and calcaneus (subtalar dislocation of the foot). In this case, there is significant thickening and deformation of the ankle and heel area. The heel is turned inward. Dislocations of the tarsal and metatarsal bones occur when the foot is compressed and causes its deformation with protrusion of the dislocated bones to the rear or to the sides. An extensive hematoma of the dorsum of the foot is noted.
Ankle subluxation usually occurs in obese people or people with weak ligaments. Weakness of the ligaments leads to the fact that a person twists his leg when walking. Usually, after a twisted leg, traumatic swelling of the joint occurs, which, with gentle treatment, goes away in two to three weeks. And if the ankle injury was isolated, the joint is completely restored in one to two months.

In some people, the ankle ligaments are so weak that repeated subluxations of the joint may occur. After several subluxations, the structure of the cartilage in the joint is disrupted, and this, in turn, can lead to arthrosis.

Deforming arthrosis of the ankle is a serious disease of the musculoskeletal system, leading to a decrease in a person’s ability to work and possible disability. This term also refers to osteoarthritis, deforming osteoarthritis and some other diseases.

In most cases, arthrosis deformans is a consequence of a severe injury to one or more of its anatomical components - the outer and inner malleolus, tibia, and talus. As a result of injury, the surface of the bones entering the joint becomes uneven, which leads to impaired gliding of the articular surfaces and their additional trauma during movement.

Manifestations of deforming arthrosis are varied. Pain in the ankle and lower leg muscles, swelling of the joint, limited mobility in it, impaired gait, limited walking over long distances - this is just an incomplete list of suffering experienced by a patient with deforming arthrosis.

Osteoarthritis, or degenerative arthritis, is a common disease among people reaching middle age. With age, the smooth, sliding connecting surface of bones (cartilage) wears out and wears away. As a result, the joint becomes inflamed, swollen, and ankle pain occurs. Joint syndrome progresses slowly, and pain and stiffness in the ankle increases over time.

Arthritis

Rheumatoid arthritis. The exact cause of rheumatoid arthritis is not known. Although the disease is not hereditary, researchers believe that some people are more susceptible to the disease because they have a genetic predisposition. Typically, an infectious factor acts as a “trigger” that activates these genes. When the body is exposed to it, the immune system begins to produce substances that attack the joint. This is the likely mechanism for the development of rheumatoid arthritis.

Post-traumatic arthritis. The main reasons for the development of this type of arthritis are ruptures of the soft connective tissues of the joint and displacement. An injured joint is seven times more likely to develop arthritis, even after proper treatment. In fact, some time after the injury, the body begins to produce hormones that stimulate the degenerative process of cartilage cells. If you have pain in the ankle, you should immediately seek help from a rheumatologist or traumatologist.

Characteristics/clinical presentation

The first indicator of TCS is load-dependent, persistent pain between the Achilles tendon and the peroneus longus tendon. Stiffness, weakness, and swelling may also occur in this area. The second main symptom is a decrease in the range of motion during plantar flexion, compared to the healthy side. In some cases, the triangular bone can be felt. Eversion or inversion movements may cause discomfort. Pain in the back of the ankle may be felt when plantar flexing the foot or dorsiflexing the big toe.

Diagnostic procedures

X-ray examination in lateral projection; when the leg is loaded, the foot is in plantar flexion.
CT scan.
Magnetic resonance imaging (MRI) is the preferred procedure to determine the presence and extent of ossification, associated pathologies, and damage to soft tissue and bone. MRI during flexion/extension provides information about the mobility of the triangular bone.
Bone scintigraphy using technetium shows increased uptake in the triangular bone area.

Lateral fluoroscopy of the foot shows the triangular bone

Latin terms from this lesson:

Pes;
Tarsus;
Metatarsus;
Ossa digitorum;
Talus;
Corpus tali;
Collum tali;
Caput tali;
Facies superior ossis tali;
Trochlea tali;
Facies malleolaris medialis;
Facies malleolaris lateralis;
Processus lateralis tali;
Tuberculum mediale;
Tiberculum laterale;
Sulcus tendinis musculi flexoris hallucis longi;
Sacies articularis calcanea posteror;
Sulcus tali;
Facies articularis navicularis;
Tuber calcanei;
Facies articularis cuboidea;
Facies articularis talaris posterior;
Facies articularis talaris media;
Facies articularis talaris anterior.

I'll continue to cover the rest of the foot bones in the next tutorial to keep my articles from getting too long. At the end of this lesson, I would like to point out that all the bones of the foot are very dense and have many surfaces to connect to each other.

As you study the anatomy of each individual bone, pay special attention to the articular surfaces and what surfaces of other bones they connect to. This is the main thing you should remember about this topic.

Survey

Pain and swelling may be noted by palpation between the Achilles tendon and the peroneus longus tendon.

The passive-forced plantarflexion test should be performed with repeated rapid passive flexion movements in the neutral position and internal and external rotation at the point of maximum plantarflexion. When triangular bone syndrome is present, intense friction occurs between the tibia and heel bones.

Plantar flexion

Ligamentous and articular joints directly associated with bone

The spherical shape of the talus-calcaneal navicular joint includes: the talus bone head, the sphere of the anterior and superior calcaneus, and the navicular bone. The relationship between the movements of the subtalar and the talocalcaneal navicular joint is determined by the axis of rotation, which is common for both joints. It passes through the bony head, the calcaneal tubercle. The movement goes around this axis, its angle is approximately 55 degrees. In addition to being axially centered, the talocalcaneal navicular joint is integrated with the subtalar interosseous ligament.

The supracalcaneal bone has no muscle attachments, but is tightly surrounded by them and the tendons that connect the lower leg to the foot.

The blood supply to the ram is provided by a system of ligaments and several blood branches directly from nearby arteries. If the blood supply is impaired, for example, with cervical fractures, especially together with dislocations, serious consequences can occur: aseptic necrosis, formation of a false joint of the cervix.

Treatment

Non-steroidal anti-inflammatory drugs or corticosteroid injections are used to reduce soft tissue inflammation. In case of a fracture, a splint is applied below the knee for 4-6 weeks.

If symptoms persist, surgery is performed (strong evidence; all studies report a positive outcome), which includes removal of the triangular bone. After the operation, a bandage is applied for 5 days. This is followed by physical therapy, lasting 4-8 weeks. Full recovery takes 6 months.

Physical therapy

Factors such as rest, ice, massage or ultrasound may be used during treatment. Isometric and eccentric exercises are used to strengthen and stretch the muscles of the lower leg.

Exercises are also prescribed to improve muscle activity during plantar flexion. The deep-seated muscles (tibialis posterior, flexor digitorum longus, flexor pollicis longus) and peroneus longus are antagonistic to the gastrocnemius. During deep muscle activity, the talus moves anteriorly (particularly during plantar flexion), which may reduce the influence of the triangular bone on the posterior tibia. When the gastrocnemius muscle contracts, the heel bone is raised and the triangular bone is compressed.

Strengthening deep-lying muscles. Carrying out positions “on half toes” (2) and “on pointe shoes” (3), holding the heel bone in place with your hands. Bending the knee (90° angle) prevents contraction of the calf muscle.

Incline board proprioceptive exercises are also used to correct lower extremity abnormalities. All exercises were found in only one study, the study group of which consisted of 11 dancers with posterior ankle injuries, including 6 cases of TKA. Nine of them showed good treatment results using these exercises, the other two underwent surgical treatment.

Classification of the foot parts

The foot (pes) is divided into three sections:

Tarsus ;
Metatarsus ;
Finger bones (ossa digitorum).

I found an illustration on Wikipedia from Gray's atlas, in which the metatarsal bones are tinted:

Everything that is proximal to the highlighted zone (circled in blue) belongs to the tarsus, everything that is distal (circled in yellow) is the bones of the fingers. By the way, the bones of the fingers are also called “phalanges”.

This is quite similar to the terminology from hand anatomy, isn't it? There, as you remember, there were also three sections - the wrist, metacarpal bones and phalanges. Here, respectively, are the tarsus, metatarsus and phalanges.

Let's use an x-ray to mark these three parts: