Version May 2024
INTRODUCTION — Gamekeeper's thumb (or skier's thumb) derives its name from court gamekeepers who developed chronic degeneration of the ulnar collateral ligament (UCL) of the metacarpophalangeal joint from repeatedly twisting the necks of fowl and other game caught while hunting. Today, ski pole injuries and other athletic injuries are the most common cause of this condition.
The diagnosis and management of UCL injury of the thumb is reviewed here. Other thumb and hand injuries are discussed separately. (See "Evaluation of the patient with thumb pain" and "Overview of finger, hand, and wrist fractures" and "History and examination of the adult with hand pain" and "Overview of hand infections" and "Scaphoid fractures" and "Overview of carpal fractures".)
EPIDEMIOLOGY — Skiing accidents in which the thumb strikes a fixed ski pole and other athletic injuries involving thumb abduction are the most common cause of UCL tears [1-3]. Complete ruptures are often caused by non-sport-related falls [4]. The injury occurs more commonly in males, with a ratio of 3:2. Thumb injuries are second in frequency only to knee injuries among skiers [5].
MECHANISM OF INJURY — Forced abduction and hyperextension of the thumb metacarpophalangeal joint is the usual mechanism causing injury of the thumb UCL [1,6-9]. This can occur if someone falls onto their thumb or the thumb is struck, violently forcing it into abduction. A similar mechanism occurs when a ski pole becomes fixed in the ground and the momentum of the skier drives the thumb into the pole handle. This usually occurs when a skier falls. Disruption of the UCL may occur from repetitive use as well as acute injury, but this is less common.
CLINICAL FEATURES
Patient presentation — Patients with an UCL injury complain of pain, which is exacerbated by thumb extension or abduction, and swelling along the ulnar aspect of the thumb metacarpophalangeal (MCP) joint [1-3,6-10]. Paradoxically, pain may be minimal when presenting for medical evaluation in patients with a complete UCL tear compared to those with a partial tear. The patient often takes the thumb and first finger and rubs over the MCP joint when describing the condition. If the patient presents several weeks to months after the injury, pain, weakness, or loss of stability are the usual complaints. These may be exacerbated by pinching or grasping objects.
Examination findings — The diagnosis of UCL injury is confirmed by the following physical examination findings [1,2,6-11]:
●Physical examination has good sensitivity for ruling out UCL tears when compared with ultrasound and magnetic resonance imaging (MRI; 97 versus 95 and 99 percent, respectively) [11]. MCP joint tenderness is localized to the ulnar side of the joint. The entire joint may be swollen, or swelling may be localized to the ulnar side.
●Valgus stress testing reveals a loss of integrity of the UCL.
This is demonstrated by increased laxity of the MCP joint, particularly when compared to the uninjured thumb when a valgus stress is applied, as shown in the following video clips and photographs (movie 1 and picture 1 and picture 2 and picture 3) [7,11,12]. Note that some discrepancy in joint laxity between thumbs occurs normally in some individuals [13]. The absence of a discrete endpoint with valgus stress testing also suggests UCL injury [13,14]. With partial tears, loss of a distinct endpoint may be the most notable finding.
Valgus stress testing should be performed with the MCP joint in both neutral and flexed positions. With the MCP flexed to about 45 degrees, the UCL is isolated from other lateral stabilizers (eg, volar plate) [15].
Surgical texts commonly site an absolute increase in joint laxity of 30 degrees with valgus stress testing or a relative increase of 15 to 20 degrees compared to the uninjured thumb, as determining UCL rupture, but in practice, it can be difficult to make such measurements precisely [14].
It is safe to perform valgus stress testing prior to radiographs as this maneuver has not been shown to create Stener lesions or to displace fractures [16,17]. However, in cases of more significant hand trauma, it may be best to perform testing after radiographs are obtained to rule out a more severe injury.
Injection of a local anesthetic may improve diagnostic accuracy when pain limits the physical examination [18].
●The MCP joint may not fully flex to 90 degrees.
●The strength or holding power (pinch grip) of the thumb and first finger may be compromised.
DIAGNOSTIC IMAGING
Approach to and methods for imaging — Standard posteroanterior, lateral, and oblique radiographs of the thumb are indicated in patients with suspected UCL injury to identify bony avulsions at the ligament’s insertion at the base of the proximal phalanx, and other potential fractures (image 1 and image 2). In the absence of avulsion, plain films are usually normal; degenerative changes may be present years after the injury.
If the thumb examination is equivocal, stress radiographs can be performed to determine the degree of UCL laxity. Alternatively, ultrasonographic or fluoroscopic imaging while applying stress to the metacarpophalangeal (MCP) joint can be performed to identify UCL injury (image 3) [19-23]. Ultrasound has the advantage of not subjecting the patient to radiation and is generally accurate for making this diagnosis. (See 'Ultrasound' below.)
Both magnetic resonance imaging (MRI) and ultrasound have higher specificity for ruling in tears when compared with physical examination (100 and 91 percent, respectively, versus 85 percent) [11]. MRI has a high sensitivity and specificity for ligament rupture [9,23,24]. In patients with evidence of complete rupture by physical examination or stress radiography, MRI has slightly better specificity in identifying Stener lesions when compared with ultrasound (98 versus 94 percent), which may influence the need for surgery (picture 4) [23]. Ultrasound and MRI have similar sensitivities for Stener lesions (95 versus 93 percent) [23]. However, MRI is expensive and generally unnecessary [14]. (See 'Indications for surgical referral and surgical outcomes' below.)
Ultrasound — Musculoskeletal ultrasound can be used to assess UCL injuries of the thumb with accuracy according to small observational reports [25], although test characteristics have varied among studies. In one review, the overall sensitivity for UCL tears was reported to be 96 percent and specificity 91 percent [11]. Ultrasound has the advantage of not subjecting the patient to radiation.
A dynamic ultrasound assessment performed while a valgus stress is applied to the joint enables the clinician to compare the degree of laxity between thumbs, thereby assisting with diagnosis. If image resolution is good, the clinician can identify disrupted ligament fibers that do not span the metacarpophalangeal joint (image 4 and image 5) [21,26]. Complete UCL tears may be seen as a “stump sign,” in which the retracted ligament appears as a round heterogeneous mass proximal to the MCP joint. (See "Musculoskeletal ultrasound of the wrist", section on 'Ulnar collateral ligament of the thumb'.)
A common mistake is to believe the injured adductor aponeurosis contains intact UCL fibers. With a displaced UCL tear (ie, Stener lesion), the proximal edge of the adductor aponeurosis is often injured as well and appears hypoechoic and thickened on ultrasound. The presence of the adductor aponeurosis can easily be confirmed with passive flexion of the interphalangeal joint [25]. During this dynamic ultrasound examination, the adductor aponeurosis can be seen gliding back and forth over the MCP joint as the extensor tendon moves. A Stener lesion has a rolled-up appearance at the leading edge of the proximal adductor aponeurosis. The proximal stump may be seen superficial to the aponeurosis, or more proximally along the metacarpal.
DIAGNOSIS — The diagnosis of UCL injury is suspected on the basis of a history of thumb injury involving forced abduction, combined with suggestive examination findings, namely local signs of inflammation and laxity of the metacarpophalangeal (MCP) joint of the thumb with valgus stress. Diagnostic imaging to rule out other bony injury and confirm laxity of the MCP joint is generally performed, and helps to confirm the diagnosis. Although not required in all cases, a definitive diagnosis can be made using advanced imaging studies. (See 'Diagnostic imaging' above.)
DIFFERENTIAL DIAGNOSIS — Diagnosis of an acute UCL injury is generally straightforward. Should the presentation be delayed or unclear, alternative diagnoses may need to be considered. The causes of thumb pain are reviewed in detail separately. (See "Evaluation of the patient with thumb pain".)
INDICATIONS FOR SURGICAL REFERRAL AND SURGICAL OUTCOMES — Referral to an orthopedist or hand surgeon is indicated for patients who have a bony fragment on plain radiograph of the thumb at the metacarpophalangeal (MCP) joint that is more than 2 mm displaced or involves greater than 10 to 20 percent of the articular surface, or who manifest clinical signs of a complete UCL tear (valgus testing reveals more than 30 degrees of laxity, or laxity 15 to 20 degrees greater than the uninjured thumb) [27]. It is best to refer the patient to a hand surgeon for more definitive evaluation if the stability of the joint appears to be compromised in any way. According to a systematic review of 14 primarily retrospective observational studies, the outcomes of surgical repair of complete UCL tears are generally good and complications are uncommon [28].
Patients with partial injuries (with or without joint laxity) generally do well with splinting rather than immediate surgery [29]. Patients with complete tears and avulsion injuries may do well with splinting as well, with up to 85 percent of patients healing without residual instability, pain, or stiffness [9,23]. However many hand surgeons consider early surgical repair the treatment of choice for complete tears because of the risk of a Stener lesion, in which the aponeurosis of the adductor pollicis becomes trapped between the ends of the torn UCL (picture 4) [7,30,31]. Stener lesions can be difficult to diagnose, both clinically and with imaging. Nevertheless, similar functional outcomes are reported for patients treated with late surgery (>6 weeks after the initial injury), although it appears that many patients develop radiographic evidence of MCP osteoarthritis [31,32].
In patients with a normal radiograph or images showing bony fragments that are less than 2 mm displaced, and minimal joint laxity with stress examination, conservative treatment may be sufficient. However, if there is any doubt about the nature or extent of a possible UCL injury, it is best to refer the patient to a hand specialist.
NONSURGICAL MANAGEMENT
Acute therapy, splinting, and rehabilitation — Ice should be applied acutely to the thumb metacarpophalangeal (MCP) joint. The nonsurgical treatment of choice is immobilization with a thumb spica splint (picture 5 and figure 1). Prefabricated splints are acceptable (picture 6). The MCP joint is typically flexed to about 20 degrees. The wrist does not need to be immobilized.
For injuries amenable to nonsurgical management (ie, no significant avulsion injury, no significant joint instability, normal radiographs, and no other concerning clinical findings), the thumb should be protected from valgus stress for at least three weeks, after which gentle passive and active range of motion exercises may be performed out of the splint, along with isometric strengthening of thumb flexors and intrinsic muscles of the hand (pinch and handgrip). Repeat valgus testing should be performed at this time. If significant instability continues to exist, surgical referral is indicated.
Immobilization should continue for another three weeks when the patient is not performing exercises, until swelling and pain have completely subsided. Once the splint is discontinued, patients should be advised to avoid heavy gripping or grasping until grip strength has returned to normal. Assuming the patient regains normal function of the thumb MCP joint following nonsurgical management and there is no instability, no additional imaging or referral is necessary.
Persistent symptoms — In addition to the indications mentioned above, surgery may be needed in patients who do not respond to conservative therapy. Reattachment of the torn distal ligament, tendon graft repair, or arthrodesis (fusion of MCP joint) can be performed with a high success rate [33]. Late surgical repair (>6 weeks post injury) generally results in reasonable outcomes; however, neglected injuries may lead to chronic instability of the MCP joint, which can result in persistent pain, decreased pinch strength, or degenerative joint changes. Surgical repair is not recommended if the MCP joint has developed osteoarthritic change [9].
RETURN TO WORK OR SPORT — Published data discussing return to sport after surgical reconstruction are limited; however, many athletes are able to return within four to seven weeks post-operatively with good results and maintained performance, including sports such as American football and baseball [34-37].
PREVENTION — Strapless poles do not prevent UCL injury in skiers because falls, even when the hands are not in a strap, can force radial deviation of the thumb [27].
SUMMARY AND RECOMMENDATIONS
●Mechanism – Ulnar collateral ligament (UCL) injury is caused by forced abduction and hyperextension of the metacarpophalangeal (MCP) joint, as might occur when a downhill skier falls and their thumb is thrust against a planted ski pole. (See 'Mechanism of injury' above.)
●Clinical presentation and examination – Patients complain of pain and swelling along the ulnar aspect of the thumb MCP joint initially. Weakness and instability may be the primary complaints of patients who present several weeks or months following the injury.
Clinical findings include tenderness and swelling along the ulnar aspect of the thumb MCP joint, weakness with pinch grip, and increased joint motion with valgus stress testing (movie 1) compared to the contralateral MCP joint. (See 'Examination findings' above.)
●Diagnostic imaging – Standard posteroanterior, lateral, and oblique plain radiographs of the thumb are indicated in patients with suspected UCL injury. Stress radiographs, fluoroscopy, or ultrasound examination may be needed to reveal increased joint laxity and confirm the diagnosis. (See 'Diagnostic imaging' above.)
●Management – Experienced clinicians may follow patients designated for conservative care. Referral to a hand surgeon is prudent in most cases of known or suspected UCL injury, particularly if there is increased joint laxity. (See 'Indications for surgical referral and surgical outcomes' above.)
Ulnar-sided thumb injuries amenable to nonsurgical management (no significant joint instability, normal radiographs, and no other concerning clinical findings) may be treated initially with immobilization and close follow-up. The thumb should be protected from valgus stress. (See 'Nonsurgical management' above.)
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