Ulnar collateral ligament injuries of thumb were first described in gamekeepers who sustained the injury from the repetitive nature of breaking the neck of small game such as birds and rabbits. Hence, this was originally referred to as gamekeeper's thumb. The recurrent thumb hyperextension sustained by gamekeeper's would mechanically lead to degeneration and tears of the ulnar collateral ligament located at the base of the first metacarpophalangeal joint. More recently, this condition is also referred to as skiers’ thumb, since it is more commonly observed in falls in individuals holding ski poles that mechanistically cause the same type of hyperextension thumb injury.
When the thumb is placed in extreme abduction or extreme hyperextension, there is a risk of injury to the ulnar collateral ligament, which stabilizes the base of the thumb at the first metacarpophalangeal joint. In one specific group, skiers, this injury is more frequently observed since individuals can fall and strike their thumb on a fixed ski pole. The role of the ulnar collateral ligament is to assist in the stability of the thumb near its base as it meets the first metacarpal. Any mechanism such as a fall or strike injury that forces the thumb to become forcefully abducted can threaten the integrity of the ulnar collateral ligament. Also, if the patient experiences repetitive injury through abduction at the thumb, chronic ulnar collateral injury pattern may result.
Ulnar collateral ligament injuries are observed more frequently in the male population, with a 60% predominance in this gender. Specific patient populations that may be at risk include certain sporting activities where the mechanism of injury may occur, including, but not limited to, skiing, baseball, and javelin. Furthermore, simple mechanisms such as falls in the elderly may result in this injury pattern.
The anatomic function of the thumb is complex and beyond the scope of this article; however, it is important to recognize that the ulnar collateral ligament assists in stabilizing the thumb at the metacarpophalangeal joint. To adequately grasp and hold onto objects, the thumb acts in a coordinated fashion with hand muscles, finger muscles, and ligamentous structures, including the ulnar collateral ligament. By understanding this mechanism of thumb function, one can see how hyperextension (or extreme abduction) may result in a tear to the ulnar collateral ligament. These can be classified as partial, complete, or chronic. As observed in other acute joint injuries, the patient may have swelling and tenderness at the first metacarpophalangeal joint. Also, there may be instability or laxity noted at that joint.
History and Physical
The typical history obtained in a patient with ulnar collateral ligament injury includes fall or injury, causing extreme thumb abduction or hyperextension. The patient with localized discomfort to the first metacarpophalangeal joint area. Accompanied with the pain, there may be concomitant swelling near or at the thumb base. The patient may present acutely in the immediate post-injury timeframe, or the patient may not present for quite some time if the injury is more chronic. In both situations, pain and occasionally weakness may be present, especially when attempting to hold onto objects (pincer grasp mechanism in particular).
The physical examination can be especially helpful in discerning this diagnosis. Perform a valgus stress test by abducting the thumb at its base can help to determine if any laxity or complete disruption of the ulnar collateral ligament exists. Contralateral comparison with the unaffected thumb can help to establish a baseline to delineate the degree of tear or injury further. In situations where partial tears exist, there is increased laxity or mobility on valgus stress testing. A lack of any endpoint during such testing would portend a complete tear with complete instability at the thumb base. One method to help isolate the ulnar collateral ligament during testing is first to ask the patient to flex the first metacarpophalangeal to 45 degrees. This helps to more specifically test the ulnar collateral ligament rather than other ligaments at the thumb base.
Based on orthopedic studies, the typical degree of laxity, which should raise suspicion for ulnar collateral ligament injury, is any amount greater than 15 to 20 degrees on abduction or valgus stress testing. This should be compared to the unaffected thumb. Furthermore, if the degree of laxity is more than 30 degrees, this is very suggestive of ulnar collateral ligament tear. While this is described in the orthopedic literature, in the actual clinical environment, the provider may have difficulty accurately measuring the degree of ulnar collateral ligament laxity.
Imaging in the setting of an acute ulnar collateral ligament injury is typically not helpful. However, plain films can be performed of the thumb to rule out fracture or bony abnormalities, in particular of the thumb base (proximal phalanx). The ulnar collateral ligament inserts along the medial (ulnar) aspect of the proximal phalanx of the thumb. Hence, an avulsion fracture may be present in the setting of ulnar collateral ligament injury. In the vast majority of cases, however, plain x-ray imaging is normal or unrevealing in these patients.
In the hands of experienced ultrasound providers, this modality can be used at the bedside in real-time to assess laxity at the first metacarpophalangeal joint. Similar to the physical exam, ultrasound imaging can be done on both thumbs to compare one side to another and to establish a baseline on the unaffected side.
Magnetic resonance imaging is difficult to obtain acutely, but this technique has the highest sensitivity and specificity for the diagnosis of ulnar collateral ligament injury, including tears or ruptures.
The differential diagnosis for ulnar collateral ligament injuries includes other musculoskeletal injuries that may be sustained to the hand and thumb. This includes tendinous injury such as adductor pollicis disruption. This may also include any dislocation of the thumb at the metacarpophalangeal joint. Bony injuries such as Rolando or Bennett fractures should also be considered. Arthritis of the thumb joint may also be considered.
Partial tears of the ulnar collateral ligament are usually treated with splinting alone and, despite the long duration of immobilization, tend to heal well. In a minority of patients, there may be persistent stiffness and pain. As discussed in the treatment and management above, surgery typically can be performed without significant complications in the setting of complete ulnar collateral ligament tears. In those individuals who develop Stener lesions or go without treatment, chronic changes can be observed to the metacarpophalangeal joint space.
Generally, the patient should wait at least six weeks before returning to work or sports.
Pearls and Other Issues
When the thumb is placed in extreme abduction or extreme hyperextension, there is a risk of injury to the ulnar collateral ligament, which stabilizes the base of the thumb at the first metacarpophalangeal joint. In one specific group, skiers, this injury is more frequently observed since individuals can fall and strike their thumb on a fixed ski pole. Hence the synonymous term of skiers' thumb.
Laxity at the first metacarpophalangeal joint (thumb base) on abduction stress testing is suggestive of ulnar collateral ligament injury. Providers should compare to the contralateral unaffected thumb for a baseline reference point.
As with most other musculoskeletal injuries, fractures should be ruled out with standard plain films, but typically imaging modalities are of limited utility acutely in this injury.
Enhancing Healthcare Team Outcomes
Although the majority of cases of ulnar collateral ligament injury do not require surgery, referral to an orthopedic or hand surgery specialist is prudent for long-term care planning and therapy referral. In the acute setting, such as the emergency department, the provider's goals for therapy should include acute pain relief and immobilization (thumb spica splint). Splint placement can be performed by providers, nurses, or techs. Splint care and patient education can be provided by the orthopedical specialty nursing staff. Further therapy that can be performed at home by the patient includes ice therapy, rest, and elevation. Complete ulnar collateral ligament tears usually mandate surgical intervention. Complications of an untreated complete tear include the Stener lesion and development of chronic arthritis. Judicious use of pain medication can be considered. Collaborating with specialists and working in the acute setting with an interprofessinoal team approach will help ensure the best outcome for these patients. [Level 5]
(Click Image to Enlarge)
Rupture of the UCL of thumb
Image courtesy S Bhimji MD
Agout C,Bacle G,Brunet J,Marteau E,Charruau B,Laulan J, Chronic instability of the thumb metacarpo-phalangeal joint: Seven-year outcomes of three surgical techniques. Orthopaedics & traumatology, surgery & research : OTSR. 2017 Oct [PubMed PMID: 28576699]
Jakubietz RG,Erguen S,Bernuth S,Meffert RH,Gilbert F,Jakubietz M, An anatomical study on the Stener-type lesion of the radial collateral ligament of the metacarpophalangeal joint of the thumb. The Journal of hand surgery, European volume. 2020 Feb [PubMed PMID: 31739733]