Under the Sesame bones medicine understands flat, round bones embedded in tendons. These bones improve the biomechanical effects of the tendons and keep the tendon apparatus at a distance from the bones in order to avoid pressure damage. Fatigue fractures are the most common symptoms of sesamoid bone.
What are sesame bones?
Sesame bones are tendon bones. Together with the long bones, the flat bones, the short and the irregular bones, the sesame bones form a total of five different types of bones. In humans, they occur particularly in the wrist and ankle. Each sesame bone is grown or embedded in a tendon. The bones hold the tendons and the surrounding bones apart at a certain distance. Usually the small bones appear in tendons on a joint.
The largest and most famous sesame bone is the patella, also known as the kneecap. The patella is embedded in the tendons of the so-called quadriceps femoris muscle and is involved in the articular surfaces of the knee joint. Like all sesame bones, the patella creates more space between the surrounding bones and tendons. How many sesame bones a person has is relatively individual. For example, not everyone has the fabella of the knee joint. Women are somewhat more often equipped with this spacer bone than men. Animals also have sesame legs. In the horse, for example, the legs between the fetlock and the tubular leg fall into this group.
Anatomy & structure
Usually sesame bones are flat and round bones. As far as their size and shape are concerned, the human sesame bones are relatively variable depending on their location. The patella of the knee joint, for example, runs triangularly in the tendon of the quadriceps femoris muscle and merges into the knee joint. The fabella on the lateral gastrocnemius head, on the other hand, is embedded in the shape of a bean in the tendon of the gastrocnemius muscle, but not found in every human being. The so-called ossa sesamoidea of the hand are also sesame bones.
This includes the pisiform bone, which belongs to the carpal bones and is embedded in the tendon of the flexor carpi ulnaris muscle. The most famous sesame bone of the hand is the pea bone. The metacarpal bone in turn consists of the metacarpal bone. Sesame bones can also occur in this area. As a rule, about two to three of the bones are located distally here. In the foot there are also sesamoid bones in the area of the sesamoid bone. They are embedded in the flexor tendons of the big toe.
Function & tasks
All sesame bones act as a spacer. They keep the tendon away from the surrounding bones and especially the adjacent joints, thereby making movement easier, among other things. The construction of the sesame bones helps the muscle on a tendon to have a greater pulling effect. The bones are therefore often referred to as switching points.
Thanks to the patella, the lower leg can be stretched, for example, even if the muscle involved in the thigh is not particularly strong. The stretching is associated with what feels like little effort, because the tendon connected to the sesame bone achieves better biomechanical leverage thanks to the bones. In this context, the sesame bones also take on the function of a pulley and thus provide the tendon with additional protection. Some tendons run along a joint.
In their course through a joint, tendons with sesamoid bones are protected from damage that could occur as a result of the pressure. For this purpose, the sesamoid deflects the tendons so that pressure damage is prevented. If a tendon runs along a joint, without the sesamoid bone it can also be damaged by bruising, for example. In this context, the sesamoid bones prevent the tendon from slipping into the joint space and becoming painfully pinched.
Diseases
Sesame bones are often affected by fatigue fractures. Such fractures are usually noticeable in the form of a stabbing pain that only occurs during stress. A fracture of the sesame bone in the foot could manifest itself during jogging, for example, and cause shooting pain, which completely disappears in a resting phase. Fatigue fractures are usually the result of recurring loads, for example those in the context of certain sports.
Usually, a fatigue fracture of the sesamoid bone is initially treated with immobilization. Under certain circumstances, however, flaked bone material is removed during an operation. In addition to fractures, inflammation of the sesamoid can also occur. Most of these inflammations are characterized by overheating and radiate to the metatarsophalangeal joint near the sesamoid. Inflammatory processes also appear as a side effect of sesamoid fractures or bone fractures in the immediate vicinity of the sesamoid bone, as this can lead to misalignments and incorrect loads.
If the sesame bones of the foot are affected by inflammation, an orthopedic insole is usually recommended as a therapeutic measure. Sometimes aseptic necrosis of the bone occurs as part of a fracture and inflammation of the sesamoid bone. In order to avoid this long-term consequence, discharge is strongly advised. Orthopedic insoles can support this relief in case of complaints in the foot, for example. The sesamoid bones of the hand can also be affected by fractures, inflammations or necrosis as a result of overloading in the context of chronic incorrect loading.
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