The bones of the webspace of the thumb are held stable by strong ligaments on either side of the thumb. Occasionally the ulnar collateral ligament, the ligament between the thumb and index finger, tears.
Nowadays, a fall on the outstretched thumb is the most common injury, seen especially in skiers. In previous times, the gamekeeper could injure his thumb while breaking the neck of the poor animals that were caught on the Master’s hunt.
Initially, there is pain and swelling at the base of the thumb, and pain using the thumb for pinching and gripping. Later on, the primary complaint may be that of thumb weakness or instability with pinching, opening jars, car door handles, etc.
Tenderness along the ulnar collateral ligament. Instability and discomfort with stress testing of the ligament.
X-rays are required to rule out a fracture. Selective stress testing, under x-ray or real-time fluoroscopy may be valuable.
Casting the wrist and thumb for several weeks.
Repair of the torn ligament, with reattachment to the bone.
There is controversy regarding surgery versus casting for acute ulnar collateral ligament tears. Sometimes, when the ligament tears off of the bone, it may fold back on itself or get caught under some other tissue. Thus the torn end of the ligament may not be next to the area of the bone that it was torn from. If this happens, the ligament will not heal, and chronic instability will result. There are arguments both for and against early repair of this torn ligament, and should be discussed with your doctor.