If you have arthritis pain in your wrist that doesn’t go away, your doctor may want to operate. Joint fusion, also called arthrodesis, stabilizes joints and gets rid of wrist pain when options are limited for patients with wrist arthritis. Unfortunately, this procedure can reduce mobility in the wrist. Doctors have seen this effect when they fuse the joint formed by the radius, the bone on the thumb side of the forearm, and the scaphoid, the largest bone on the thumb side of the wrist. The connection of the radius with the scaphoid is called the radioscaphoid joint.
Is there a way to operate and avoid a stiff wrist? These authors thought so. They believed that the scaphoid was the bone limiting movement after surgery. By taking out part of the scaphoid, they hoped to free up movement in the wrist.
They tested this model on the wrists of five cadavers. The authors mimicked the effect of joint fusion by fixing the cadavers’ radioscaphoid joints with special wire. X-rays were used to measure wrist flexibility both up and down, and side to side. Next, the authors removed part of the scaphoid bone farthest from the radioscaphoid joint. Then they measured wrist movement again.
After joint fusion, wrist movement up and down was less than half of what it was before surgery. Side to side movements were also much less after the procedure.
But when the far edge of the scaphoid was taken out, movement in the wrist improved considerably. Up and down movements approached normal at 122 degrees. This was a 106 percent improvement over movement after the joint was fused. Side to side movements increased to 43 degrees, a 32 percent improvement.
The main increase in movement occurred in the mid-section of wrist bones (the midcarpal joint). The authors think the scaphoid blocks movement in this part of the wrist by forming a bony “bridge.” When the far end of the scaphoid is taken out, the midcarpal joint is released and more movement is possible. In this study, the midcarpal joint accounted for 86 percent of the improvement in up and down movements of the wrist.
Taking out part of the scaphoid is a simple step that makes a big difference. This procedure could get rid of the wrist stiffness that often goes along with fusion of the radioscaphoid joint. The next step is to test the procedure on patients who suffer from arthritis in this joint.