Diaphysis: Functions, Composition and Major Diaphyseal Fractures

The diaphysis It is the central part of the long bones. It is responsible for supporting the weight of the body as columns and, at the same time, increase the power of the muscles working as a lever. Not all bones have diaphysis, only long bones. The bony structures where it is located are located mainly in the extremities.

Thus, the bones of the body that have diaphysis are: in the upper extremities, the humerus, the radius, the ulna (previously known as the ulna), the metacarpals and the phalanges; and in the lower extremities the bones with diaphysis are the femur, the tibia, the fibula (formerly known as the fibula), the metatarsals and the phalanges.

In addition to those previously mentioned, the ribs and clavicles are also long bones with diaphysis although they are not in the extremities. All the bones with diaphysis are known as long bones and in addition to the central part (diaphysis) there are two additional parts.

These two parts are the epiphyses, located at the ends of the bone; and metaphyses, which are located at the junction of the diaphysis and the epiphysis. Each of these bone sections has specific functions for the proper functioning of the skeleton.

The rest of the bones of the organism do not have diaphysis. They are classified as flat bones, and their structure and function are different from those of long bones.

Diaphysis composition

In general, long bones are composed of two distinct parts: the cortex or cortical bone, and the bone marrow .

The cortex represents the exterior of the bone and is covered by the periosteum, while the medulla occupies the interior of the bone, with blood and lymphatic vessels running inside it.

Cortical bone

The cortex is composed of dense bone, laminar structure, very hard and with a certain torsion that allows it to withstand the great stresses to which the shaft is usually subjected.

The bark is organized like a tube, which allows the bone to be very resistant but at the same time light. However, it is not a hollow tube but with a very important tissue inside: the bone marrow.

On the outside, the diaphysis of the long bones is covered by a thin layer of richly innervated fibrous tissue known as the"periosteum", which is responsible for the sensibility and at the same time acts as an anchoring point for the insertions of muscles and tendons.

Bone marrow

The bone marrow is a soft tissue made up of hematopoietic cells (producers of red blood cells) during childhood. Subsequently, they are mainly composed of fatty tissue.

The bone marrow works as a shock absorber, absorbing the forces that are generated into the diaphysis.

Functions

Diaphyses have two main functions:

1- This structure is capable of supporting the weight of the human body as a"pylon or column", especially the diaphysis of the femur and the diaphysis of the tibia; The diaphysis of the humerus and the diaphysis of the ulna (radio) can also be done, although to a lesser extent and for a limited time.

2- It serves as an anchoring point to the muscles (through the tendons) and certain ligaments, allowing the force generated by the muscular system not only to be transmitted to the bones, but to be amplified by functioning as levers.

Since there is more than one muscle taking insertion in the diaphysis of the bones, these have specialized structures that allow to increase the insertion surface, (for example, the rough line in the diaphysis of the femur). These structures form grooves and valleys in the diaphysis where the tendons of the muscles take on an individual insertion.

Usually the muscles are inserted in two consecutive bones, passing in most cases on a joint (union between two specific bones). Then, according to the fixed point that the muscular contraction takes, there will be a movement or another in the limb.

Diaphyseal fractures

Diaphyseal fractures are the most frequent in long bones. They usually occur due to a direct impact, where the force is applied perpendicular to the major axis of the bone.

According to its characteristics, diaphyseal fractures can be classified as simple (when the diaphysis fractures in a single point), complex (when the fracture occurs in two or more points) and comminuted (when the diaphysis fractures in multiple fragments).

In addition, the fractures can be transverse (the fracture line has a direction perpendicular to the major axis of the bone), oblique (fracture line between 30 and 60º with respect to the major axis of the bone) and spirals (form a spiral around the bone). the diaphysis).

Depending on the type of fracture, the type of treatment for it is decided. There are two basic options: orthopedic treatment and surgical treatment.

Orthopedic treatment

The orthopedic treatment (conservative or non-invasive) is that which consists of immobilizing the limb where the diaphyseal fracture is presented by means of some orthopedic element.

Gypsum or plastic plaster casts are usually used, although immobilization devices such as skeletal traction can also be used.

The goal of this treatment is to keep the ends of the fracture in contact in order to allow the scar tissue to form a callus that will ultimately fuse both ends.

Orthopedic treatment is usually reserved for simple and transverse fractures, although it is not a condition sine qua non .

On the other hand, this is the treatment of choice as long as there is no contraindication in children, since surgical procedures can damage the growth cartilage and compromise the final length of the limb.

In cases of diaphyseal fractures of the long bones of the hands and feet - metacarpals and metatarsals - the treatment of choice is usually orthopedic (immobilization) although in certain cases it is necessary to require surgery.

Surgical treatment

Surgical treatment of diaphyseal fractures involves performing surgery. Through an incision in the skin you access the muscle planes, which are separated to access the fracture site.

Once in the area you can use different synthesis materials such as cortical plates with cortical screws, which are ideal for the diaphysis of bones that do not carry a load like the humerus, the ulna, the radius and the fibula.

You can also use the intramedullary nails (blocked or not with cortical screws), these are ideal for the treatment of bones that carry load, such as the femur and the tibia.

Regardless of the osteosynthesis material chosen, the procedure is performed by the orthopedic surgeon under general anesthesia. The aim is to keep all fragments of the fracture joined together by the nail or the plate, something that would not be possible in certain cases with orthopedic treatment.

In cases of diaphyseal metacarpal and metatarsal fractures, special wires or screws are usually used as synthesis material, although these procedures are reserved for very complex fractures that could not be resolved with orthopedic treatment.

In general, this treatment is reserved for spiral fractures, comminuted or complex, provided there is no contraindication.

References

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