Introduction
Under the term lunatum malacia (composed of lunatum malacia), a layman can imagine little to nothing. If one has received the diagnosis oneself, one knows at least already that it must be a disease of the hand, because there it hurts. But what is this disease, what in the hand is affected and will it pass?
Definition
Lunatum malacia is a disease of a carpal bone, the so-called “moon bone”. Untreated, the disease can lead to the death of the bone. Several causes are responsible for the development of lunatum malactia, although the exact mechanism of the disease development is still partly unclear.
Other names for lunatum malacia are “Kienböck’s disease” and aseptic bone necrosis of the Os Lunatum. The Os lunatum is one of the eight small carpal bones of the hand skeleton and is called moon bone. It is located in the middle of the upper row of carpal bones and forms, among other things, a joint surface with the radius of the forearm.
Malacia of a bone or organ means softening or even dissolution. In medical jargon, lunatum malacia is also called idiopathic vascular osteonecrosis of the lunate bone. This term contains all important information about this disease.
Idiopathic means of unknown origin and indicates that a bacterial inflammation of the bone does not play a role here (aseptic = without bacteria/virus involvement). Vascular has something to do with the vascular supply of the bone. Osteonecrosis is the technical term for the death (necrosis) of a bone (osteo-). Lunatum malacia is therefore a vascular death of the carpal bone Os lunatum that occurs of its own accord.
Causes
Lunatum malacia is caused by reduced blood flow to the lunate bone, a small bone in the hand. This reduced blood supply then leads to slow damage to the bone, which becomes increasingly unstable over time until it finally breaks. One can imagine the mechanism similar to a heart attack, only in the bone, which happens very slowly, because bones have a much slower metabolism than the heart.
But in the end, the bone tissue that is not supplied with blood also dies. So where does this reduced blood supply come from and why does it occur mainly in this bone? Since very often people who work with pneumatic hammers for a long time are affected, it is assumed that either like vibration or the direct damage caused by the shocks are disease-causing.
The vibrations are suspected to stimulate the vessels that supply the carpal bones to contract by an unknown mechanism. This reduces the blood supply and damages the bone. A further factor seems to be that when working with a jackhammer, the hand is usually overstretched, which prevents sufficient drainage of the blood.
Another theory is that the lunar bone is directly damaged by the repeated vibrations causing microscopic cracks in the bone. But why exactly is the lunate bone, i.e. the “Os Lunatum”, damaged? After all, there are eight carpal bones!
The Os Lunatum is located in the middle of the row of carpal bones close to the trunk of the body and is therefore exposed to a particularly high level of stress and is therefore particularly affected by vibration. A shortened ulna, i.e. one of the forearm bones, also carries an increased risk of lunatum malacia. A shortened ulna is not actually pathological and does not cause any complaints in itself, but the shear forces on the wrist are considerably higher due to the changed position of the joint, so that 70% of all patients with lunatum malacia also have a shortened ulna.
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