Ulnar collateral ligament injury

UCL injury is short for ulnar collateral ligament injury of the thumb, most often due to a skiing accident, hence, the condition is now commonly referred to as skier’s thumb ¹. Injuries to the ulnar collateral ligament (UCL) were first recognized as an occupational condition in European gamekeepers. By repetitively wringing the necks of game (eg, chickens, birds and rabbits) between their thumb and index finger, these workers produced a chronic stretching of the UCL that resulted in degeneration and tears of the ulnar collateral ligament of the first metacarpophalangeal joint and instability at the first metacarpophalangeal joint. UCL injury became known as gamekeeper’s thumb ².

The ulnar collateral ligament is strong band of tissue, which is attached to the middle joint of the thumb (the metacarpophalangeal or MCP joint), keeps your thumb stable so that you can pinch and grasp things.

The ulnar collateral ligament can tear in different ways. For example, it may be pulled off its attachment at the base of the first bone (the proximal phalanx) in the thumb or from its origin on the metacarpal bone. It can also be torn through its middle, although this is less common.

Ulnar collateral ligament injury occurs in skiing accidents (when the thumb is forcefully driven into the ski pole), falls, and other sports-related injuries (e.g., baseball and javelin). UCL injury pattern occurs more frequently in males (60%) than females (40%) ³.

The ulnar collateral ligament acts as a lateral stabilizer of the metacarpophalangeal joint. In concert with the intrinsic hand and finger muscles, it allows for adequate grasp and pinch mechanism. Hyperextension abduction mechanisms can result in a partial, complete, or chronic injury to the ulnar collateral ligament. Swelling and inflammation at the metacarpophalangeal joint along with laxity and instability subsequently ensue.

The UCL is composed of a proper collateral ligament and an accessory collateral ligament. The proper collateral ligament originates from the dorsal third of the metacarpal head and inserts on the volar aspect of the proximal phalanx. The accessory collateral ligament originates palmar to the proper collateral ligament and runs continuously with the proper collateral ligament to insert on the volar plate. The proper collateral ligament is taut in flexion, while the accessory collateral ligament is taut in extension. Both ligaments ensure the ulnar stability of metacarpophalangeal joint. The adductor pollicis inserts on the proximal phalanx, functioning as a dynamic stabilizer of the metacarpophalangeal joint. It lies superficial to the UCL. Understanding the structural relationship between the adductor pollicis aponeurosis and the ulnar collateral ligament is crucial to understand the pathoanatomy of the “Stener lesion” ⁴. A Stener lesion occurs when a complete distal thumb ulnar collateral ligament tear results in the interposition of the aponeurosis of the adductor pollicis muscle between the metacarpophalangeal joint and torn ulnar collateral ligament ⁵. This interposition results in the adductor aponeurosis acting as a barrier separating the ruptured ends of the ligaments preventing healing ⁶. In short, a Stener lesion is UCL that is torn, displaced and entrapped ⁷.

Most cases of ulnar collateral ligament injuries require referral to a hand specialist to determine appropriate long-term care options. Acutely, clinicians should provide pain relief. Ice can be applied to the injury, and a thumb spica splint can be used to help immobilize the thumb’s metacarpophalangeal joint. Some ulnar collateral ligament tears can be treated with immobilization alone, but complete tears generally require surgery to avoid the Stener lesion and subsequent chronic arthritic changes.

Figure 1. Ulnar collateral ligament tear

Ulnar collateral ligament injury causes

Injuries to the UCL are caused either by chronic repetitive valgus stresses, such as originally described in gamekeepers or extreme thumb abduction trauma ⁸. Common causes include skiing injuries when the skiers fall on the abducted thumb with the ski pole in hand (skier’s thumb), or injuries in other sports such as hockey, soccer, handball, basketball, and volleyball ⁴. The ulnar collateral ligament acts to stabilize the thumb at its base; if a patient falls or has the thumb forcefully abducted the ulnar collateral ligament can be injured.

Ulnar collateral ligament injury grades

Ulnar collateral ligament injury are graded, depending on the degree of injury to the ligaments

• Grade 1 sprain (mild). The ulnar collateral ligaments are stretched, but not torn.
• Grade 2 sprain (moderate). The ulnar collateral ligaments are partially torn. This type of injury may involve some loss of function.
• Grade 3 sprain (severe). The ulnar collateral ligament is completely torn or is pulled off its attachment to the bone. These are significant injuries that require medical or surgical care. If the ligament tears away from the bone, it may take a small chip of the bone with it. This is called an avulsion fracture.

Ulnar collateral ligament injury symptoms

Patients with an ulnar collateral ligament injury typically complain of pain localized to the ulnar aspect of the thumb metacarpophalangeal joint ⁸. The discomfort is worsened by abduction or hyperextension of the thumb. There may be a complaint of swelling at the base of the thumb, perhaps more pronounced along the ulnar aspect. The patient may present acutely after an injury, but the presentation may also be delayed by weeks given ongoing pain and weakness of the injured thumb. Instability of the thumb, and grip and pincer grasp weakness may also be evident, especially in patients who delayed presentation ⁹. The weakness described by the patient is usually when he or she is attempting to grasp or pinch an object between the index finger and the affected thumb.

If the ulnar collateral ligament is completely torn, the end of the ruptured ligament may cause a lump or swelling on the inside of the thumb. Your thumb joint may also feel loose or unstable. You may have difficulty grasping items between your thumb and index finger.

Physical examination may be helpful in clinching the diagnosis. Valgus stress testing (thumb abduction) can reveal instability, laxity, or a complete tear of the ulnar collateral ligament. It is useful to compare this abduction stress testing to the unaffected thumb. Partial tears may result in increased mobility (laxity) in comparison to the uninjured side. Complete tears will reveal an obvious lack of endpoint in motion during the abduction stress testing.

When the metacarpophalangeal joint is flexed to 45 degrees, the ulnar collateral ligament is more adequately isolated from the remaining ligamentous stabilizers. Stress testing in this position can also aid in the diagnosis.

Classically, the orthopedic literature states that any laxity greater than 15 to 20 degrees with valgus stress testing (in comparison to the unaffected side) suggests ulnar collateral ligament tear. Absolute laxity of 30 degrees or more also is highly suggestive of a tear. In clinical practice, however, this may be challenging to measure accurately ¹⁰.

Ulnar collateral ligament injury diagnosis

Your doctor will want to know how and when your injury occurred and will ask you to describe your symptoms. He or she will then carefully exam your thumb and hand.

To help determine if the ulnar collateral ligament is partially or completely torn, your doctor will move your thumb in different positions to test the stability of the metacarpophalangeal joint. If the joint is loose and unstable, it is an indication that the ulnar collateral ligament may be completely torn.

Imaging studies

X-ray imaging of the thumb should be performed to rule out concomitant bony injury. Bony avulsion injury may be present at the base of the proximal phalanx at the insertion site of the ulnar collateral ligament. A special type of x-ray, called a stress x-ray, may also be ordered. During this test, your doctor will apply tension to your thumb while it is being x-rayed to learn more about the stability of the metacarpophalangeal joint. If the test causes pain, you may be given an injection of a local anesthetic. In most instances, however, x-ray imaging is normal in patients with an ulnar collateral ligament injury.

Magnetic resonance ( MR ) arthrography is considered the gold standard when evaluating for UCL injuries ⁶. Despite the reported sensitivity of 96% and specificity of 95%, MRI does come with a high cost and restricted availability ⁸.  Despite magnetic resonance imaging (MRI) has both high sensitivity and specificity for ulnar collateral ligament rupture but is not generally indicated.

Ultrasound can be performed real-time to assess for degree of laxity at the first metacarpophalangeal joint. This can be performed on both thumbs, comparing the degree of ulnar collateral ligament laxity between the injured and uninjured sides.

Recent literature has highlighted the growing advantage of ultrasound. In addition to being non-invasive, cost-effective, and less time consuming, ultrasound has been shown to have 100% sensitivity and specificity in discerning between non-displaced and displaced tears ⁶. Others have reported that depending on the experience of the examiner, the accuracy of ultrasound in diagnosing a Stener lesion ranges from 81% to 100% ⁸.

The real-time capability of the ultrasound can easily show the anatomic relationship of the UCL as it pertains to adductor aponeurosis ⁶. Dynamic ultrasound imaging with the interphalangeal joint of the thumb in passive flexion can distinguish between a non-displaced UCL tear and a Stener lesion ¹¹. Ultrasound also affords quick comparative imaging of the uninjured side ⁶.

The appearance of a Stener lesion on the ultrasound has been called the “tadpole sign” or “yo-yo on a string sign.” Ridley et al. ¹² note “The head of the tadpole is formed by the retracted proximal fragment of the UCL which displaces to be adjacent to the head of the metacarpal. The tail of the tadpole is formed by the adductor aponeurosis which is often thickened and lies deep to the retracted UCL fibers.” The “yoyo on a string sign” appearance presents by the small mass displaced superficial to the adductor pollicis from the torn ligament fibers that retracted proximally. The “yoyo on a string sign” can also be seen in an MRI ¹³.

Ulnar collateral ligament injury treatment

Treatment for a ulnar collateral ligament injury depends on the severity of the injury. In the acute phase of ulnar collateral ligament injury, rest, ice, and immobilization (RICE) should be utilized. Partial ulnar collateral ligament tears may do well with splinting only but still need a referral to a hand surgeon. After a period of immobilization for approximately 3 weeks, these nonsurgically managed injuries can begin gentle rehabilitation: passive and active physical therapy, thumb strengthening, and hand strengthening. However, the immobilization should be continued for at least 3 additional weeks while the patient is not actively rehabilitating the thumb and hand. If instability, weakness, pain, and swelling persist, a surgical referral is required. Splint immobilization in the acute setting is achieved with a thumb spica splint.

Nonsurgical treatment

The RICE protocol:

• Rest. Try not use your hand for at least 48 hours.
• Ice. Apply ice immediately after the injury to keep the swelling down. Use cold packs for 20 minutes at a time, several times a day. Do not apply ice directly on the skin.
• Compression. Wear an elastic compression bandage to reduce swelling.
• Elevation. As often as possible, rest with your hand raised up higher than your heart.

Additionally, nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen, can help reduce pain and swelling. If pain and swelling persist for more than 48 hours, however, see a doctor.

For a moderate sprain, your doctor will probably immobilize your thumb joint with a bandage, thumb spica cast, or splint until it heals. To ease pain and swelling, you can apply a cold pack to your thumb twice a day for 2 to 3 days after the injury. Do not apply ice directly on your skin.

Depending on the severity of the injury, you may be instructed to wear the splint or cast at all times. It is important that you avoid applying any pressure or resistance to your thumb until you are permitted by your doctor.

Because immobilization may cause some stiffness in your thumb joint, your doctor may recommend some stretching exercises to help you regain full range of motion.

Figure 2. Thumb spica splint

Footnote: For a partial ulnar collateral ligament tear, wearing a thumb spica cast for a period of time will allow the ligament to heal.

Surgical treatment

Bony avulsion fractures in association with ulnar collateral ligament injury require urgent referral to a hand specialist. Also, any valgus stress laxity greater than 15 to 20 degrees in compared to the uninjured side (or 30 degrees of absolute laxity) should be referred to a hand surgeon.

Complete ulnar collateral ligament tears repaired surgically tend to do well and are mostly without complications. Early repair is recommended for most complete tears to prevent the development of the Stener lesion. Normally, the ulnar collateral ligament lies deep to the adductor pollicis tendon. In a Stener lesion, the torn end of the ulnar collateral ligament slips and becomes superficial to the adductor aponeurosis and muscle. Therefore, with this lesion, the adductor pollicis muscle lies between the ulnar collateral ligament and the metacarpophalangeal joint, preventing appropriate healing ¹⁴.

Surgery involves reconnecting the ulnar collateral ligament to the bone and/or repairing the avulsion fracture using a pin, screw, or special bone anchor.

After surgery, you may have to wear a short arm cast or a splint for 6 to 12 weeks to protect the thumb ligament while it heals.

Ulnar collateral ligament injury prognosis

Surgery is generally well tolerated in complete ulnar collateral ligament tears and outcomes are good. Ninety percent of patients with complete rupture of the UCL treated with primary repair within 3 weeks have been reported to have good-to-excellent outcomes regardless of repair method ¹⁵. Most partial ulnar collateral ligament tears treated with splinting alone also tend to heal without residual pain, laxity, instability, or stiffness. Patients who develop Stener lesions or who may go undiagnosed for weeks tend to develop metacarpophalangeal arthritic changes. Return to work or sporting activities can occur in approximately 6 weeks.

If these late complications develop, surgery may be needed to rebuild the ligament using tissue from your upper arm. If there is significant arthritis, a joint fusion procedure may be needed to address both the arthritis and the instability of the metacarpophalangeal joint.

References

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