Location of the Thumb MCP Joint Injury
Ligaments attach one bone to another. The ulnar collateral ligament is located at the base of the thumb, near the V-crease where the thumb and index finger meet, on the inside of the thumb. The ligament attaches two bones, the proximal and distal phalanx, to each other at the metacarpophalangeal (MCP) joint. The distal phalanx is the second bone in the thumb; the proximal phalanx begins where the thumb meets the V between the thumb and first fingers.
Symptoms of a Torn UCL
It can be difficult to tell whether the thumb ulnar collateral ligament is completely or partially torn. Tearing the ulnar collateral ligament makes your thumb unstable; it bends more than it should, which makes it hard to grip and squeeze. The thumb doesn’t bend completely away from the hand, even if the ligament is completely torn, because another ligament, the accessory collateral ligament, also attaches to the bones and keeps the thumb from dangling off the hand altogether. The injury is usually quite painful initially and afterwards whenever it’s stressed. There may be quite a bit of swelling around the joint and into the palm as well.
Diagnosing a UCL Tear of the Thumb
It’s best to see a hand specialist for a suspected UCL tear. He may take X-rays to see if the thumb is fractured or dislocated. From the ligament being torn, the bones can shift slightly. There may also be a visible piece of the born torn from the attachment site of the ligament, or a fracture.
The doctor will also take measurements of how far your thumb bends, called valgus stress testing, as opposed to the opposite thumb. Generally speaking, if the thumb has more than 35 degrees of laxity, or 15 degrees more than the opposite thumb, a complete tear is present. If the ligament has folded back on itself, it may be felt as a lump known as a Stener lesion.
Treating a UCL Thumb Joint Tear
If there’s a question about whether there’s a full tear or a partial one, the doctor may recommend wearing a hand splint for up to three to four weeks, to see if the thumb improves. The two ends of ligament may heal together if they're close enough to each other. But, according to an article entitled "Gamekeeper's Thumb: Injuries of the ulnar collateral ligament of the metacarpophalangeal joint" by A. Ganel, Z. Aharonson, and J. Engel, if a Stener lesion is present, the ends won't be close enough to heal. If the thumb still deviates more than it should, and/or there are still symptoms such as pain, he may recommend surgery. If there’s no question that the ligament is torn, surgery will be needed to repair it.
Surgery for Thumb Joint Pain From a UCL Tear
Surgery is done as an outpatient and generally takes between one to three hours. Sedation is given either as general anesthesia or as a block that numbs the entire arm with enough IV sedation to cause drowsiness. Pain medication will be given for the first week or so; the thumb will be extremely numb the first day or so and completely encased in a soft cast that extends almost to the elbow.
Recovery From a UCL Tear
Full recovery and use of the thumb can take three months; normal activities may not be able to be resumed until then, including work, depending on the job. A week or so after surgery, the soft cast is removed and a hard cast that goes halfway to the elbow is applied. Stitches are removed; the usual incision is a lazy “S” curve down the side and front of the thumb. There may also be a second incision on the opposite side of the thumb if the surgeon reattached the ligament by taking it through the thumb bone and anchoring it to the other side of the thumb.
Three weeks or so after that, a removable hard thumb splint is worn, and physical therapy is started. It’s very important not to stress the repair and re-injure the ligament. After a few more weeks, a soft removable brace will replace the hard splint; some normal activities can be undertaken without the splint at that time.
Life After Thumb Ulnar Collateral Ligament Repair
The hand surgeon will give the go-ahead when it’s safe to go back to normal activities. The thumb may remain stiff, with less ability to bend than previously. The joint should be more stable for pinching and gripping activities than it was before the surgery.
Wheeless' Textbook of Orthopaedics
Clifford Wheeless III, MD