Thumb CMC Joint Arthritis
Thumb CMC Joint Suspensionplasty Surgery
Suspensionplasty refers to the step that some surgeons perform after removing the trapezium bone to suspend the metacarpal base some distance away from the scaphoid bone that now sits underneath it. This step is aimed at preventing the metacarpal base from settling over time, possibly leading to some recurrence of pain as the space narrows. The historic way of doing this involved drilling metal pins ( K-wires) into the neighboring second metacarpal bone during the healing process so that the scar tissue stabilizes the first metacarpal base in a spaced-out position; these pins are removed at four to six weeks after surgery. The pins can get infected and are sometimes painful. Another common way to suspend the first metacarpal base is to weave a tendon, harvested from nearby in the wrist, through the base of the bone and secure it back to itself. This technique requires borrowing a tendon from nearby, and it may be prone to some amount of settling over time as the body partially resorbs the tendon. Because of these concerns, surgeons looked for an implant or device that could be placed through the metacarpal base to stabilize it. The ideal implant could be left in place and would not degrade over time.
Thumb CMC Joint Interposition Arthroplasty Surgery
Surgical treatment of thumb CMC joint arthritis involves removing the damaged cartilage surfaces of the metacarpal and the trapezium bones where they meet at the joint. There are several ways to put metal implants in one or both of the bones, such as happens with total hip or knee replacements. These procedures seem to wax and wane in popularity and the implants have been prone to complications historically. As such, a more tried and true way to treat thumb CMC joint arthritis focuses on removing the trapezium bone all together. Following this step, surgeons often place some type of cushion under the base of the metacarpal bone; this is called interposition arthroplasty, because the surgeon is placing a cushion between (interposing) the joint surfaces. One of several available tendons from the wrist, or several biologic membrane substances can be used to create the cushion. Some surgeons just allow the blood and scar tissue to congeal into a natural cushion during the healing process. This type of surgery has been performed for close to a century, which means it works well!
The Arthrex CMC Mini Tightrope® Fixation System is a smaller version of the Tightrope® device, also by Arthrex. These implants consist of a span of very strong suture material with a button at either end. The device goes across two bones that are being stabilized at a certain distance from each other. The length of the suture span can be adjusted as it is implanted, and then the buttons are fixed in place and the extra suture is cut. Orthopaedic surgeons became familiar with this device in the ankle, where it is used to stabilize the fibula and tibia together if the syndesmosis ligaments are injured. Shoulder surgeons began using it to stabilize the coracoid to the clavicle in AC joint injuries (shoulder separations). More than a decade has passed since hand surgeons started using a smaller version of this device, the Mini Tightrope®, to fix the first metacarpal base to the second metacarpal base. Studies have shown that the stability of this implant is superior to using a tendon, so movement can be started earlier after
surgery safely. Other studies have shown that the implant results in the same amount of space over time compared to using K-wires, but without the issues of pain and infection.