Introduction
Pain in the wrist is common and can be the result of strain, or fractures. Often the palm of the hand, under which the so-called scaphoid bone or os scaphoideum is located, is the most painful. The scaphoid is one of 8 carpal bones that form the connection between ulna and radius and the metacarpals.
Due to its elevated position, the scaphoid bone is particularly prone to injuries. When falling on the palm of the hand, it is usually the scaphoid bone, which absorbs the most energy during the fall, that is most frequently injured rather than the deeper lying, neighboring bones. Pain in the scaphoid is therefore particularly frequent after falls.
Unfavorably, the blood supply to the scaphoid – unlike usual – comes from the direction of the fingers. In addition, the supplying vessels of the scaphoid do not form anastomoses (connections) among themselves. This leads to complicated operations and complicated healings.
Causes of scaphoid pain
The most common cause of scaphoid pain is falling on the flat of the hand. This can happen during sports as well as in old age. It is a natural protective mechanism of the body to protect the head and neck, so we stretch out our arms reflectively when we fall.
A broken scaphoid is often accompanied by a distal radius fracture, the most common fracture of the human body. The parts of the radius near the wrist break, with or without the involvement of the adjacent wrist. Such a fracture with a fall on the outstretched hand is called a Colles fracture.
Fractures of the scaphoid typically cause only slight pain and sensitivity to pressure, but not the severe pain one is used to from fractures. Therefore, scaphoid fractures are often ignored, and “sat out”. As long as the fracture fragments are correctly positioned on top of each other, it is possible to regain freedom from pain.
However, if the fragments grow together crookedly, this can lead to permanent pain in the scaphoid and restrictions in movement. An operation is then very difficult, as the newly grown piece of bone has to be separated again and correctly aligned. In any case, the treatment of a scaphoid fracture is a particular challenge: Due to the complicated vascularization, fractures are difficult to treat.
In many cases, the supplying vessel is also damaged and can no longer supply the fragment. Many scaphoid fractures therefore do not heal completely. This is known as pseudoarthrosis.
Pseudoarthrosis, especially in the wrist, results in an altered force effect of the muscles on the wrist as a whole. This can result in a so-called SNAC-Wrist syndrome, from the English: SNAC: Scaphoid Nonunion Advanced Collaps, freely translated: Extended collapse [of the wrist] after the scaphoid has not healed. This can lead to a collapse of the wrist statics as a result of the altered force effects.
SNAC-Wrist Syndrome can lead to arthrosis if left untreated, i.e. premature, excessive wear and tear of the joint. All cavities and dissolutions of the bone are summarized as bone cysts. A common mechanism of origin is a growing ganglion, which originates from a tendon or ligament of the wrist.
In the case of minor irritation and inflammation of a tendon, the surrounding mucous membranes form increased amounts of lubricant, which cannot drain through the tendon sheaths and wrist structures. In many cases, the tendon sheaths bulge out, which can lead to an externally visible ganglion and lump on the wrist. In rare cases, however, the fluid presses on the bone and continuously hollows it out.
The fluid-filled cyst can vary in size and can therefore be treated differently. Smaller cysts do not pose a risk and do not require further treatment. Above a certain size, however, the stability of the bone is considerably reduced, which can easily lead to fractures of the bone.
To treat the cyst, the bone can either be stabilized with a nail or filled with cement. This can prevent complications of a scaphoid fracture. Necrosis of the scaphoid is a loss of bone due to insufficient blood supply to the bone.
The blood circulation at the wrist is ensured by small and fragile vessels, which can be damaged by injuries and heavy strain on the wrist. Typical is a permanent load by jackhammer, which leads to a slow destruction of the scaphoid. A typical symptom of scaphoid necrosis is thumb-side pain in the wrist.In the long term, pain and restricted movement in the wrist can occur.
Many conservative and surgical procedures can be considered for treatment. The wrist can be immobilized for several weeks with subsequent movement therapy. In many cases, however, necrosis has progressed so far that the wrist must be partially stiffened in order to ensure painless wrist mobility in the long term.
SLD is a scapholunar dissociation that can occur after an injury to the wrist with a rupture of the SL ligament. The scaphoid and lunar bone slide apart and can be dislocated from their anatomical position. There are several degrees of SLD, depending on the extent of the carpal bone malposition and the concomitant injuries.
The pain and movement restrictions in the wrist can be considerable. Depending on this, a conservative or surgical therapy can be chosen. The conservative therapy consists of repositioning the bones and immobilization for several weeks. In many cases, however, SLD must be treated surgically, by fixing the bones in their original position and suturing the torn SL ligament. In the case of advanced damage, partial stiffening of the wrist may have to be performed to achieve the best possible pain-free mobility of the wrist.
