Hand Surgery

Thumb Saddle Joint Arthrosis, Rhizarthrosis, Saddle Joint Arthrosis, Carpometal Carpal Joint Arthrosis

Cause / development

The saddle joint of the thumb is located in the proximity of the wrist. It is referred to as the saddle joint because the first middle hand bone sits on the trapezium bone (one of the hand trapezoid bones) like a rider in the saddle. Wear and tear is one of the effects of genetic predisposition or may occur after a bone involving this joint has been fractured. The carpal joint layer is worn off more and more until bone touches against bone. Ultimately, the joint is stiff.

Symptoms

Saddle joint arthrosis is evident in pain. Different patients experience different levels of severity of this pain. In some cases even slight changes in the X-ray appearance of the joint may result in extreme pain. The problems are frequently increased by stress and often impacted by weather conditions. Due to this pain the thumb is used only sporadically, which further perpetuates the pain-based joint weakness. As a result of the body’s attempts to reconstruct the area, which can affect bone as well as soft tissue structures, the thumb saddle joint begins to swell. This may result in the loosening of band structures and joint instability. Once the arthrosis has reached a progressive state, X-ray images show substantial changes to the base of the first middle hand bone and the trapezium bone (Os Trapezium). In this case, the joint gap is no longer visible.

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