Accessory bones
overview
Accessory bones, i.e. additional bones that only occur in a few people, are particularly common on the hand and foot. Most of these bones are bones that have been lost in the course of evolution and are considered obsolete, i.e. are no longer needed by humans. One speaks of so-called atavisms. The accessory bones do not always have to be innate; they can also arise in the course of growth or maturation of the bones.
Accessory bones are often mistaken for fracture fragments, which is why it is important, for example, for radiologists or orthopedic surgeons to be familiar with these variants in order not to draw incorrect conclusions. The discovery of an accessory bone is usually a chance diagnosis because it usually does not cause symptoms. Accessory bones are to be distinguished from the so-called sesame bones, some of which only occur in some people. But in contrast to accessory bones, the sesamoid bone has a function of being embedded within a tendon and protecting it, as well as avoiding unnecessary friction.
foot
Besides the hand, the foot is the most common place where accessory bones are found. They occur in a not inconsiderable proportion of the population. For example, the Os tibiale externum occurs in a fifth of all people. In addition, the os trigonum is relatively common with a proportion of 3-15%. In about 50% of the cases, these bones appear on both sides. Some people also have multiple accessory bones in the tarsal area.
From the accessory bones mostly go no symptoms out. However, if the bones protrude outwards, this can lead to pressure points, chafing on the shoe or the like. The Os tibiale externum is a variation of the navicular bone of the foot (Os naviculare). The external tibial bone can sometimes cause pressure or stress pain, especially in people who also have flat feet at the same time. In these cases, a special shoe insert is made to reduce symptoms. In most cases, however, the external tibial is asymptomatic.
hand
Step on the hand very often Hand bones on. Examples are the os styloidum, os vesalianum, os hypolunatum, os triangulare, os epilunatum, os radiale externum, os centrale. The extra bones of the hand are actually always asymptomatic. They often raise questions when diagnosing a fracture. An important distinguishing feature between fracture and accessory bone is the shape. Accessory bones of the hand are always plump formed while fracture fragments irregular contours and Sclerosis exhibit.
Elbow
Accessory bones are rarely formed in the elbow area. The so-called sesamum cubiti, an accessory bone, occurs most frequently in the elbow. Often this extra bone is mistaken for a fracture of the elbow. As a rule, the additional bone in the joint is not associated with restricted mobility.
Upper ankle
in the upper ankle there is often an accessory bone. It is the os trigonum, which is the second most common accessory bone in the area of the foot after the os tibiale externum of the foot. The os trigonum lies against the talus from behind. The os trigonum occurs in 3-15% of the population. The os trigonum arises between the eighth and thirteenth year of life. Earlier in girls than boys. Often the bone core of the os trigonum unites with the main bone of the talus. In athletes who suffer from ankle injuries more often, the os trigonum can cause discomfort. One speaks of the os trigonum syndrome. The os trigonum is in close proximity to three important ligaments of the ankle. If the ligaments are subjected to severe stress, this can lead to irritation of the os trigonum. Those affected then usually experience stress-dependent pain in the area of the outer ankle. Sometimes the pain is accompanied by a feeling of weakness and stiffness of the joint. As a rule, the os trigonum syndrome is treated conservatively. In extreme cases, however, the accessory bone must surgically removed become.
Spine
In the spine, more precisely in the Cervical spine, the os odontoideum occurs in some people. This bone is a core of bone that is not connected to the second cervical vertebrae (Axis) is merged. It represents the vertebral body of the first cervical vertebra. The os odontoideum is often mistaken for a fracture. A cervical rib occurs in less than one percent of the population. It is more common in women than in men. These Cervical rib starts from the seventh cervical vertebra and is connected to the breastbone (sternum) via cartilage or connective tissue.
In rare cases, this cervical rib can lead to a cervical rib syndrome, which can lead to compression of nerves in the area of the arm plexus and impaired blood circulation in the area of the arm. An additional rib can occur not only in the area of the cervical spine, but also on the Lumbar spine. The lumbar rib is much more common than the cervical rib (in around 8 percent of the population. The lumbar rib usually starts at the first lumbar vertebra, rarely also the second lumbar vertebra. Sometimes it is only very small, but can also be laid out as a full rib. Lumbar rib do not cause any symptoms and are therefore of no importance to the person concerned.