Thumb Sprains: Overview

Thumb Sprains: Overview

A thumb sprain is a common soft tissue injury whereby a ligament called the thumb UCL, or ulnar collateral ligament of the thumb joint is suddenly torn or stretched over time. This ligament is located on the ulnar or front side of the thumb. The injury to this ligament can be sudden, also known as acute, or it can take some time. What is referred to as chronic, acute, or sudden injury is called a skier's thumb.

This is a disruption of the thumb UCL to an opposing force called valgus stress to the base of the thumb. The term comes from skiers who often acquire this type of injury by falling against planted ski poles. This leads to a quick partial or complete tear. Gamekeeper's thumb is a less common form of thumb sprain that occurs over time. It is due to a chronic attenuation or overuse of the UCL, leading to pain and instability.

The incidence of injury to the thumb UCL is common, approximately 200,000 patients in the United States per year. The mechanism of injury is an abduction, or away from the body, or valgus force moving through hyperextension of the thumb joint. It often occurs when falling onto an outstretched hand, a quick moment when the thumb is struck violently, or less commonly, through chronic repetitive strain.

To prevent thumb sprains, be sure to stretch the hand and fingers before exercises or sports, and use safety equipment. Prevent falls by exercising on flat surfaces and wearing comfortable shoes to avoid tripping. Try to avoid activities that require repetitive gripping or pinching motions.

Let us look at a bit of anatomy to understand the thumb joint a bit better. For orientation's sake, this is a right thumb showing the first metacarpal bone and the proximal phalanx bone. The thumb UCL or ulnar collateral ligament has 2 parts, the proper ulnar collateral ligament and the accessory ulnar collateral ligament. The proper UCL gets injured the most.

Notice how both of these parts of the ligament attach from up to down, or dorsal to volar, in an oblique fashion from the metacarpal to the phalanx bone. This obliquity is what gives so much stability to the thumb on this side and is important to maintain. The surgeon actually pays a lot of attention to this angle when fixing the ligament.

Taking this further to show complexity and severity, 3 types of injuries can occur to the UCL. The first, as we know by now, is a rupture of the UCL. The second is a tear and fracture called an avulsion fracture involving the base of the phalanx bone, and the rare third variation is when the UCL remains intact, but there is a fracture of the base of the phalanx bone.

For diagnosis during the initial physical examination, the doctor will look for symptoms of pain, tenderness, bruising, swelling, and instability over the UCL or thumb joint. The contralateral or opposite side thumb will be examined as well and compared for similarities and differences. A displaced stump or tender mass will be palpated as well. If this is present, this will be indicative of a Stener's lesion.

A further MRI would confirm this finding, as seen here. If a UCL rupture is suspected, a posteroanterior, lateral, and oblique radiograph or x-ray may be the next step to check the amount of laxity or loosening of the thumb. Once these diagnostic tests have been performed, the doctor will determine and communicate if the injury might heal with conservative nonoperative measures alone or if the injury severity warrants surgical repair or reconstruction.