The scaphotrapeziotrapezoid (STT) joint is a dome shaped joint in the radial wrist that is important in transfer of load from the thumb and radial hand to the scaphoid and the radioscaphoid and scaphocapitate joints. Arthritis in this joint is the second most common degenerative arthritis in the wrist, reported in 15% of wrist radiographs. The true incidence of arthritis in the STT joint however is unknown though we assume that most cases of arthritis are not clinically significant. Furthermore, the clinical and biomechanical significance of arthritis in this joint is unclear. The investigators' clinical impression is that the incidence of STT joint arthritis is inversely related to that of radiocarpal joint arthritis. In an ongoing study, we are examining the relationship between STT joint arthritis and radiocarpal joint arthritis on radiographs. We suggest that STT joint arthritis alters the biomechanics of the wrist by limiting movement of the scaphoid within the STT joint thereby protecting the wrist from radiocarpal arthritis by limiting instability of the scaphoid. The specific aims of this pilot study are to evaluate the movement of the arthritic scaphoid within the STT joint using a computer-generated model based on CT scan of the wrist and to compare this model with the already established model of the normal STT joint. The investigators' hypothesis is that there is significantly less motion in the arthritic STT joint.
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motion in the STT joint
Timeframe: 1 year