What are the collateral ligaments of the thumb?

The thumb metacarpophalangeal joint contains two important ligaments: the ulnar collateral ligament, which is on the pinky side of the thumb, and the radial collateral ligament, which is on the free side of the thumb. These collateral ligaments are critical for the stability of the thumb and for pinch and grip activities of daily living. The ulnar collateral ligament to the thumb is a complex ligament, comprised of the UCL proper and the accessory UCL. Together, they stabilize the thumb for pinch and grip activities; without this ligament, you would have very little pinch or grip strength and very poor overall dexterity.

How can you injure the UCL to the thumb?

UCL injuries were originally called “gamekeepers’ thumb,” although a more apt name would be “skiers’ thumb” because skiing is one of the most common mechanisms of injury. However, any blow to the inside of the thumb can cause the ligament to tear. It can also be weakened over time by the degenerative aging process. There is also a serious complication of UCL injuries known as a Stener lesion, in which the ulnar collateral ligament is torn, displaced and ultimately caught between the muscle that moves the thumb and the thumb bone. If this happens, there is no chance for healing, even if the tear is caught acutely and casted immediately. The ligament simply can’t get itself back into place if it is stuck beneath the muscle.

How is a UCL injury diagnosed?

UCL injuries are often immediately obvious because of swelling, pain, and instability at the joint.

However, x-rays are still needed to rule out a fracture or bone fragment from the ligament detachment. Finally, MRI is helpful to check for a Stener lesion and to look for other injuries that may have happened at the same time.

How are UCL injuries treated?

Partial tears and minimally displaced tears can be treated in a cast, which is worn for four weeks followed by a removable splint until motion and stability are returned. Complete tears that are displaced are treated surgically. This procedure requires your surgeon to surgically reattach the ligament. Most everyone can get back to the same level of function after surgery. This includes those that have been injured chronically.

What if the UCL injury is chronic?

Oftentimes, patients will present with instability long after an injury.  Fortunately, these injuries can usually be treated by mobilizing the ligaments and performing a primary repair; sometimes, a graft is used. In any case, these patients usually have good success.

What happens if a UCL does not heal properly?

If a UCL injury is not treated, the metacarpophalangeal joint will become arthritic due to prolonged instability. Once the joint is arthritic, the only treatment is an arthrodesis or fusion of the joint. An arthrodesis is well tolerated in this joint, but a reconstruction of the UCL is obviously a much better treatment option.

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