Hand Surgery
1st Edition

Fractures and Joint Injuries of the Thumb
Elizabeth A. Ouellette
Anna H. Makowski
Three distinctive features of the human hand, each involving the thumb, give humans the ability to manipulate materials in unique ways: (a) thumb length that exceeds that of the anthropoids, (b) thumb orientation that allows angulation of the thumb toward the palm, and (c) presence of a flexor pollicis longus (FPL) tendon within the thumb. The first two features allow the motion that most distinguishes the human hand from that of other species—opposition of the thumb to the other four digits. The third feature stabilizes the thumb in opposition.
In the anthropoids whose hands most closely resemble human hands anatomically, the tip of the thumb usually reaches only the metacarpophalangeal (MCP) joint of the second digit. By contrast, the tip of the human thumb generally reaches the mid-portion of the proximal phalanx (Fig. 1A). In humans, the orientation, or “set,” of the trapezium with respect to the carpus allows more thumb abduction and a greater range of thumb positioning in abduction than in the anthropoids (Fig. 1B) (1). The FPL tendon is a long, broad structure that originates from a large area deep within the forearm and passes over the volar surface of the thumb MCP joint before attaching on the volar side of the distal phalanx of the thumb. Generally missing in the anthropoids, this tendon lends stability to the human thumb in opposition, preventing overextension of the thumb interphalangeal (IP) joint in key, lateral, and three-jawed chuck pinching activity and in abduction of the IP joint in pinch. The extra thumb length, increased abduction, and increased stability provided by the FPL tendon combine to permit gripping patterns that are more effective for manipulating objects (2).
The unique features of the human hand may have begun to evolve as early as 2.5 million years ago, as our ancestors started to use prehistoric stone tools. Anthropologic research suggests that three grips would have been particularly effective in controlled manipulation of those tools: (a) the pad/side grip by the thumb against the side of the index finger, (b) the three-jawed chuck “baseball” grip, (c) and a five-jawed “cradle” grip in which an object rests passively in the palm of the hand (2,3). The resultant exertion of force and tolerance of stresses while manipulating these early tools may have shaped the evolution of the hand’s distinctive features. Today’s humans are able to use their hands for purposes ranging from fine motor skills as in microsurgery to the use of extreme force as in rock climbing.
Millions of years of evolution have led to the intricate anatomy of the thumb, allowing us to use it in powerful grips or for delicate precision tasks. It is important as surgeons to understand the anatomic structures and their biomechanical function before attempting repair. If the structure’s function is not fully understood, a perfectly aligned anatomic repair may not give the patient the return of function as before injury or disease. Included in some of the description of the thumb’s anatomic part below is a brief description of the part’s importance in terms of sparing it during surgery.
Bones of the Thumb
The bones of the thumb are distal phalanx, proximal phalanx, metacarpal, and trapezium. The most important factor to consider regarding the bones in the thumb is the alignment of the joints and alignment of the bones. The thumb needs to sit in a relaxed position at approximately 45 degrees from the point of the palm. If the thumb does not sit at this angle, it is difficult achieving pinch grip (opposition) with the other fingertips. The restoration of this alignment after an injury to bones or ligaments is necessary for successful function in the thumb.
Ligaments of the Thumb
The radial and ulnar collateral ligaments are important in the MCP and IP joints in retaining stability and restraining

force in both flexion and extension. The tendon that acts across these joints is the FPL, flexing both the MCP and IP joints. The extensors of these joints are more complicated. The extensor pollicis longus (EPL) extends the IP joint. The extensor pollicis brevis and EPL extend the MCP joint. It is possible to have an EPL tendon laceration in which the IP joint can still extend through the action of extensor pollicis brevis by the oblique retinacular ligament, also called Landsmeer’s ligament. This small tendinous band originates from the abductor pollicis brevis or the adductor pollicis and passes parallel to the EPL and inserts with this tendon into the distal phalanx (Fig. 2) (4).
FIGURE 1. A: Human and anthropoid (baboon) thumb in opposition. The tip of the primate’s thumb (shaded gray) reaches only the metacarpophalangeal joint of the second digit, whereas the tip of the human thumb reaches tip of the fifth phalanx. B: In humans, the orientation, or “set,” of the trapezium with respect to the carpus allows more thumb abduction and a greater range of thumb positioning in abduction than in the anthropoids.
The stabilizing ligaments of the trapezium and trapeziometacarpal joint with respect to osteoarthritis have been well described by Bettinger et al. (5). There are 16 ligaments in all. These are required to stabilize the trapezium, allowing pinch and grasping activities. Carpometacarpal (CMC) joint dislocations are rare and usually occur dorsally (6,7 and 8).
The IP and MCP joints have the usual configuration of collateral ligaments, volar plate, and capsule, which are important to the stability of the joints.
Muscles of the Thumb
The muscles of the thumb and their actions are listed in Table 1. The FPL flexes the IP and the MCP joint of the thumb. The thenar muscles are the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis, all of which are actively involved in facilitating opposition. The opponens pollicis muscle alone causes opposition, but the other thenar muscles are required to place the thumb in a position from which it can oppose. The adductor pollicis causes adduction of the thumb into the plane of the palm against the index finger.
The most important muscles are the opponens and abductor pollicis brevis because they create a force that places the thumb in opposition, allowing for fine motor control. The flexor pollicis brevis is not quite so important, nor is the

abductor pollicis brevis, which is an ulnar nerve–innervated muscle. The flexor pollicis brevis derives its innervation from the median and the ulnar nerve. An FPL tendon, responsible for IP joint flexion, is not absolutely essential. A fusion of the distal interphalangeal joint, if necessary, can give satisfactory thumb function. The thumb then achieves the specific functions that it is designed for in terms of pinch, turning keys, three-jaw chuck, and lateral pinch in spite of the loss of FPL.
FIGURE 2. The oblique retinacular ligament inserts with the extensor pollicis brevis (EPB) into the distal phalanx. This occurrence can make it possible to extend the interphalangeal joint even if the extensor pollicis longus (EPL) is lacerated.
Joint Muscle Muscle action Innervation
Interphalangeal Flexor pollicis longus Flexion Median C6–C8
Extensor pollicis longus Extension Radial C5–C8
Metacarpophalangeal Flexor pollicis longus Flexion Median
Extensor pollicis longus Extension Radial
Extensor pollicis brevis Extension Radial
Carpometacarpal Extensor pollicis longus Extension of thumb Radial
Abductor pollicis longus Abduction of thumb Radial
Abductor pollicis brevisa Abduction of thumb Median
Flexor pollicis brevisa Flexion/rotation of thumb Median/ulnar C6–C8, T1
Opponens pollicisa Palmar rotation of first metacarpal Median
Adductor pollicisa Adduction of thumb Ulnar C8, T1
C, cervical; T, thoracic.
a Thenar muscles.
The extensors are important to have the thumb clear an object. The EPL and the abductor pollicis longus (APL) are important in achieving abduction away from the plane of the palm. The extensor pollicis brevis function can be made up for by the EPL, but when it is absent, sometimes the EPL does not have the strength to extend the MCP joint. Consequently, the MCP joint is always in a slight amount of flexion, so even though the abductors are working, because of the flexion at the MCP joint, the thumb does not entirely clear the plane of the palm.
So, in fact, the EPL, extensor pollicis brevis, and APL are all important, depending on the anatomic variations in the person for allowing the thumb to clear and then grasp objects. The abductor pollicis brevis and the opponens muscle are important for positioning the thumb such that the thumb pad is opposite the fingertips, and this is a pronation situation for the thumb (Table 1).
Nerves of the Thumb
The sensory nerve supply to the thumb is via the median nerve to the radial and ulnar digital nerve, innervating the thumb for touch. The dorsum of the thumb receives innervation from the radial sensory branch. The muscles, which have activities across the thumb, receive innervation from several sources (Table 1).
Vessels of the Thumb
Variations of the blood supply of the thumb are important to be aware of should you have a replantation or revascularization situation. A study by Brunelli and Gilbert shows that only 15% of their studied cases of vascularization of the palmar aspect of the thumb follow the traditional description of that area. Their study also gives a first in-depth description of the dorsal aspect of thumb vasculature (9).
According to the classic description of the palmar arterial system of the thumb, the princeps pollicis artery usually originates from the radial artery. The artery then runs alongside the ulnar aspect of the first metacarpal bone and the volar surface of the adductor muscle. At this point, it reaches the subcutaneous palmar tissue at the level of the cutaneous flexion crease of the MCP joint, dividing symmetrically into the radial and ulnar collateral artery.
Variations of origin occur most commonly in the ulnar collateral artery, which can arise from one of three sources: (a) from the princeps pollicis, (b) from an anastomosis from the superficial arcade, or (c) from an artery that originates from the radial artery (9). Caution must be taken not to injure the princeps pollicis because, in some cases, it is the only blood supply to the thumb.
In the classic description, the dorsal arteries of the thumb originate from terminal branches of the radial artery at the level of the anatomic snuffbox. From here, the arteries head distally toward the dorsum, ending up as periosteal and bony skin rami at the first phalangeal level.
According to Brunelli and Gilbert, the vasculature to the dorsal side of the thumb consists of two arteries originating from the palmar artery at the level of the first metacarpal. The arteries run laterally along the MCP joint and then transverse obliquely from volar to dorsal and continue in a distal direction, remaining on the side of the phalanges. At the distal phalanx, the two parallel dorsal arteries are joined together by three arcades: (a) under the extensor tendon at the neck of the first phalanx, (b) at the nail matrix, and (c) at the nailbed (9).

FIGURE 3. Thumb abduction/adduction at the carpometacarpal joint. The carpometa-carpal joint is shaped like a saddle, which allows for the thumb’s wide range of motion.
Surgeons should not focus on only structural anatomy when repairing the thumb. Many times, physicians fix everything perfectly and anatomically it is absolutely correct, and yet there is still no function. An understanding of the anatomy and the biomechanics of the different components of the thumb is necessary to achieve the functions desired after the repair.
The phalanges of the thumb, together with the metacarpal, trapezium, and scaphoid, form a relatively independent functional unit within the hand. The separation of the FPL, low in the forearm and at the muscle origin, from the other long flexor muscles of the hand contributes to this independence of the thumb, which enhances the hand’s ability to perform highly specialized maneuvers (10).
Joints of the Thumb
The configuration of the IP joint of the thumb is essentially the same as that of the proximal interphalangeal and distal interphalangeal joints of the other digits. This joint is a bicondylar hinge joint that is capable of flexion and extension, the only movements possible in this joint. The normal arc of motion is hyperextension of 15 to 20 degrees and flexion to 80 degrees (11). The functional range necessary for routine activities of daily living is 18 degrees. The MCP joint is also a hinge joint with a normal range that can be 0 to 56 degrees, but routine function of activities of daily living requires little motion (10 to 32 degrees) (11). Full range of motion of these joints is not required for performing activities of daily living.
Normal functioning of the IP joint and the MCP joint requires them to be stable, displaying flexion and extension only and very little to no lateral motion. Injury to the ligaments of the IP or MCP joints that allow lateral motion causes weakness at the joint, preventing the thumb from performing as a stable post. In this case, the thumb lacks the necessary stability for performing functions such as three-jaw chuck, pinch, and lateral pinch as well as buttoning, holding a key, turning a key, tying a shoelace, or working a zipper. Arthrodesis of the MCP joint generally does well functionally. The resulting stiffness may cause an increase in sprains and tears (12).
The position of the CMC joint also affects the position of the MCP joint. Radial or dorsal subluxation of the CMC joint causes a hyperextension deformity of the MCP joint, which limits the ability of the thumb to circumduct and get around objects and grasp them. This most commonly occurs in osteoarthritis but can occur after injury to the anterior beak ligament in a traumatic situation.
Normal functioning of the CMC joint requires circumduction and opposition to place the thumb in a position to be able to pinch and grasp objects. The normal CMC motion averages 50 degrees of flexion and extension, 40 degrees of abduction and adduction, and 17 degrees of rotation to opposition (13). The CMC joint allows the thumb to position itself within a wide range of motions. The thumb swings against a stable immobile unit formed by the tight-fitting joints of the base of the second and third metacarpals, the trapezoid, and the capitate. The CMC joint is shaped like a saddle, which allows for the thumb’s wide range of motion. The motion can be described as a conical shape with its apex at the CMC joint (Fig. 3).
The CMC joint’s arc of motion requires the muscle groups to be functioning properly as well. The strength of thumb extension is normally 3 kg (14). The abductor pollicis brevis is consistent in subjects 20 to 59 years of age at 4.50 to 3.81 kg in males and 2.84 to 2.79 kg in females (15).
The loss of the median nerve innervation to the thumb can cause a decrease in grip strength of 32%. Pinch strength diminishes by 60%. Intrinsic muscle loss secondary to ulnar nerve injuries causes a grip strength loss of 38%, with pinch strength diminishing by 77% (16).
Three components are necessary for opposition, the most important motion of the thumb: (a) The saddle-shaped CMC joint allows circumduction, (b) the thenar muscles allow for adduction and opposition, and (c) the recurrent medial nerve triggers the thenar muscles’ action. Finally, the action of the FPL muscle–tendon unit causes

flexion at the IP joint of the thumb, allowing the thumb to easily touch the tip of the fifth finger.
Hypothetically, a patient may lose the thenar muscle action by injuring the medial nerve, for example, which causes the function of the thumb to revert back to primates—i.e., opposition is no longer possible; the thumb can only oppose to the side of the hand. The thumb with the loss of the opponens then functions in the plane of the palm, with pinch function to the side of the index affected by the FPL tendon.
Fractures of the Distal Phalanx of the Thumb
Most fractures of the distal phalanx of the thumb are associated with fingertip injuries. Even though there may be loss of bone and nail, these fractures are usually aligned and can be treated conservatively with splinting. Satisfactory use of the thumb can usually be attained by granulation of the tissues and secondary healing over the injured thumb tip.
Intraarticular fractures are usually associated with extensor tendon injuries caused by a forced flexion while extending the IP joint (17). Displaced intraarticular fractures of the distal phalanx that involve more than half of the articular joint space traditionally require fixation. An absolute indication for pin fixation is volar subluxation of the distal phalanx, which often occurs when the collateral ligament detaches from the volar fragment but remains attached to the dorsal fragment. With loss of the dorsal lip of the proximal distal phalanx, extensor tendon, and partial collateral ligament, the volar fragment of the distal phalanx subluxes volarly, causing IP joint dislocation volarly (Fig. 4) (18). In this case, pin fixation of the IP joint is required to maintain reduction of the joint. Normally, the pin can be left in place from 3 to 6 weeks, then removed, and motion begun gradually with splinting in hyperextension at all other times (17,18 and 19). Other fractures involving the articular surface can be fixed in a number of ways: Kirschner wires (K-wires), pullout sutures, or whatever method is deemed necessary to maintain joint alignment. Many times, just splinting these fractures in hyperextension maintains joint alignment sufficiently to allow full range of motion to be regained even when the alignment noted on the x-ray film is less than perfect.
Fractures of the Proximal Phalanx of the Thumb
Condylar fractures of the proximal phalanx of the thumb require fixation in a similar manner to that for any condylar fracture of a proximal phalanx (Fig. 5). If alignment of the condyles is lost or if there is an intraarticular displaced fracture, fixation is required to maintain joint alignment and restore the joint to an appropriate anatomic position. K-wires, single screws, or a minicondylar plate can be used as long as articular joint alignment is achieved and maintained. A simple traction system made of K-wires and rubber bands was devised by Suzuki et al. as an alternative to the banjo splint (20).
FIGURE 4. A: Well-aligned avulsion fracture at distal phalanx that does not require open reduction and internal fixation. A well-placed splint is sufficient. B: Volar subluxation of the distal phalanx requiring pin fixation.
Even if alignment is not lost at the time of initial evaluation, a condylar fracture should be stabilized with some form of fixation to prevent loss of alignment. The forces across these joints from flexor and extensor tendons cause these fractures to displace routinely (Fig. 6). Most shaft fractures of the proximal phalanx can be held stable in a thumb spica cast and usually heal satisfactorily. Shaft fractures with loss of alignment or rotation alignment or severe angulation of more than 20 to 30 degrees in the lateral plane require open reduction and internal fixation with K-wires or plates (21).

FIGURE 5. Unicondylar fractures of the distal proximal phalanx may be treated and stabilized by multiple Kirschner wires, mini-screw(s), or a combination of both. K-wire, Kirschner wire.
FIGURE 6. A: Thumb metacarpal shaft fractures commonly displaced with dorsal angulation due to the deforming forces of the abductor pollicis longus (APL), abductor pollicis brevis (APB), adductor pollicis (AP), and flexor pollicis brevis (FPB). B: Extraarticular base of the metacarpal angulation of fracture causing hyperextension at the MCP joint. This amount of deformity requires open reduction and internal fixation.
Intraarticular fractures of the base of the proximal phalanx or metacarpal head fractures require open reduction and internal fixation to restore anatomic joint alignment with no gap or step-off at the joint surface (Fig. 7).
Fractures of the Thumb Metacarpal
Thumb metacarpal fractures represent 10% of all hand fractures and 25% of all metacarpal fractures (22). The majority of thumb metacarpal fractures occur at the base in one of three patterns: (a) Bennett’s, (b) Rolando’s, and (c) extraarticular. Rolando’s or Bennett’s fractures, which are intraarticular fractures of the base of the thumb, require open reduction and internal fixation to maintain the articular surface and prevent arthritis as well as to give stability to the base of the thumb. The displacement and depression of the intraarticular fragment as well as the displacement of the shaft are best examined on anteroposterior lateral x-ray view of the thumb, not the hand (23). These fractures are generally approached through a Gedda and Moberg surgical volar approach (24).
FIGURE 7. Intraarticular fractures of the thumb metacarpal base may need open reduction and internal fixation for stability. In this case, a T condylar plate (T-plate) is used.
Bennett’s fractures are intraarticular fractures that tend to displace dorsomedially and supinate secondary to the pull of the APL, thenar muscles, and FPL (17,22,23,25,26 and 27). The posterior oblique CMC ligaments are disrupted, now causing dislocation (28). Acute Bennett’s fractures sometimes remain undiagnosed and are noted later when patients develop arthritis but no pain. The fact that reconstruction is not required in these cases demonstrates that a CMC joint arthroplasty secondary to a Bennett’s fracture should not be automatic but should be based on the existence of pain and discomfort.
Although Bennett’s fractures are difficult to hold with casting techniques, malunions actually result in satisfactory outcomes (29,30,31,32,33 and 34). When fracture intraarticular gaps or step-off of more than 2 mm were allowed, only 46% of patients were asymptomatic compared with 83% asymptomatic with less than 1-mm gaps or step-offs (29,35,36 and 37). Anatomic reduction and maintenance with a technique surgeons are comfortable with are necessary for acceptable outcome (29,38,39,40 and 41).

The reduction can be accomplished by K-wires, tension band techniques, and screw fixations (Fig. 8) (42).
FIGURE 8. Indirect reduction with Kirschner wire fixation is an ideal treatment option for displaced Bennett’s fractures.
Rolando’s fracture is a comminuted intraarticular fracture at the base of the metacarpal. The treatment of this is essentially identical to that of a Bennett’s fracture except that there is the added difficulty of more comminution. If internal fixations by any means are not possible, distraction techniques such as banjo casting or bridging external fixators are good alternatives (43).
In a 35-month follow-up study of displaced, comminuted fractures of the thumb CMC joint, the axial rotation averaged 79%, radial abduction 89%, key pinch 88%, and grip strength 81% compared with the uninvolved side (44). Treatments used in these patients were intermetacarpal external fixation, anatomic reduction of the joint surfaces, bone grafting, and adjunctive internal fixation. Langhoff et al. showed that 6 years after reduction of Rolando’s fracture, some patients were still symptomatic (six of 16), and a few had developed osteoarthritis (six of 11), although it was not established whether the symptoms present at follow-up were related to the quality of reduction (45).
An intraarticular fracture of the metacarpal head of the thumb is addressed in the same manner as any other intraarticular fracture. Any volar angulation of the metacarpal head must be adjusted so that the thumb MCP joint does not have to compensate with hyperextension to abduct the thumb and be able to clear objects and grasp them. The same is true for a metacarpal shaft fracture or proximal metaphyseal fracture. Often, the metacarpal fragments display apex volar angulation of 25 degrees or more if allowed to heal. This position of the metacarpal results in hyperextension of the MCP joint, which necessitates an osteotomy and realignment of the malunited fracture to provide better thumb function (21,46,47). The method of fixation can be percutaneous pinning or plate fixation depending on the degree of comminution (Fig. 6B).
Fractures of the Sesamoids of the Metacarpophalangeal Joint of the Thumb
Fractures of the sesamoid bones are associated with volar plate injuries at the MCP joint of the thumb. They are rare but are often associated with sports injuries caused by hyperextension of the thumb (48). Sesamoids can also be bipartite because of a failure of fusion of the ossification centers, found in 0.6% to 6% of hands (49,50 and 51). The sesamoids contribute to the stability of the MCP joint, the ulnar sesamoid through the adductor pollicis, and the radial sesamoid through the flexor pollicis brevis (49,52,53 and 54). This feature caused Patel et al. to classify sesamoid fractures into two types: those with the palmar plate intact and those with the palmar plate ruptured (55).
The treatment of sesamoid fractures thus depends on the stability of the MCP joint. If it is stable, a cast with the MCP joint in 20 to 30 degrees of flexion for 2 to 4 weeks is adequate for a satisfactory outcome. Taping is also acceptable (49). If unstable, the volar plate requires repair surgically and casting for 4 to 6 weeks with the MCP joint in 20 to 30 degrees of flexion.
Chronic sesamoiditis, if it occurs posttrauma, can be treated with sesamoidectomy successfully in 80% of patients (56). The MCP joint has a 17% decrease in motion and the thumb a 16% decrease in strength after this operation (57).
Fractures of the Trapezium
Trapezial fractures are rare, but when they do occur, the trapezium tends to be fractured into dust with no remaining bony structure whatsoever. A banjo cast in which traction is applied through the proximal phalanx to the thumb and to an outrigger thumb spica cast often maintains some integrity of the trapezium, and an arthroplasty can be performed later if necessary.
There are three types of trapezoid fractures: (a) body, (b) trapezoid ridge, and (c) undisplaced (marginal). The majority of fractures can be treated conservatively with casting. Those that are intraarticular without a great deal of comminution can be treated with internal fixation using K-wires or screws (58,59,60,61,62 and 63). Trapezial ridge fractures generally can be treated with splints but occasionally require excision of the ununited fracture fragment (58,61,64).
Ligament Injuries of the Interphalangeal Joint
Two main ligamentous injuries are associated with the IP joint. The first is loss of integrity of the extensor tendon, which can produce a mallet deformity of the IP joint. The second is when

the collateral ligament is associated with a large dorsal fragment and is detached from the volar fragment—i.e., mallet deformity secondary to intraarticular bony fragment. This causes volar angulation of the distal phalanx and the volar fracture fragment. An isolated collateral ligament injury is rare.
A mallet deformity can be treated with splints that maintain hyperextension. The extensor tendon scars and heals as long as the joint is not subluxed volarly. It is not necessary to repair of the ligaments per se, as they heal by scar formation. The same is true generally for the extensor tendon. Immobilization in a splint is usually successful at healing IP joint injuries. Occasionally, an irreducible IP joint dislocation occurs. This is secondary to the FPL becoming caught in a condyle of the proximal phalanx with the volar plate interpositioned within the joint. This requires an open reduction but is generally stable after reduction (65,66,67 and 68).
Metacarpal-Phalangeal Ligament Injuries
In the thumb, the ulnar collateral ligament is the most commonly injured ligament at the MCP joint. The radial collateral ligament is rarely injured (69). The injury to the ulnar collateral ligament is termed gamekeeper’s thumb, so named because the gamekeeper’s repeated use of the thumb to break the necks of the rabbits they had caught eventually caused the ulnar collateral ligament to give way and tear. Three grades of the injury have been identified: (a) The ligament is intact but strained, (b) the ligament demonstrates mild laxity, and (c) the ligament shows complete laxity (70). Grade I and II injuries can be treated conservatively with a cast and routinely do well. In grade III injuries, a Stener’s lesion develops, and the ulnar collateral ligament is displaced above the adductor tendon aponeurosis. Healing by casting is not possible because the ligament is no longer apposed to the bone, necessitating an operative procedure. The authors’ preferred method of repairing a grade III ulnar collateral ligament injury is to use a suture anchor for repair (71,72). The suture anchor is placed after abrading the surface where the collateral ligament usually originates on the proximal phalanx.
Ulnar collateral ligament injuries must be assessed with x-rays for avulsion fractures, but stress views are not, in fact, usually necessary, as the clinical examination is sufficient (64,65,70,71,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97 and 98). The acute injury usually occurs with skiing or sports, although this has been called gamekeeper’s thumb in the past. The mechanism of injury is an abduction force across the metacarpal phalangeal joint. The structures injured along with the ulnar collateral ligament are the dorsal capsule and volar plate and occasionally the adductor aponeurosis (65,73,77,99,100,101,102 and 103) or bone (a small avulsion fracture of the proximal phalanx) (74,77,101,102,103,104,105 and 106).
The ulnar collateral ligament is an important stabilizer of the MCP joint with two components, a formal collateral ligament and an accessory collateral ligament. These both provide lateral stability, but just as important, provide support preventing volar subluxation. If the injury is an acute but partial tear such that there is stability laterally as well as in a volar/dorsal plane, simple casting is sufficient. When there is a Stener’s lesion or laxity in both lateral and volar vectors, an open repair is necessary.
FIGURE 9. In a Stener’s lesion, the ulnar collateral ligament (UCL) is displaced away from its attachment on the proximal phalanx by the adductor aponeurosis, which interposes itself. In this case, an avulsion fracture fragment is seen at the distal end of the ulnar collateral ligament and may be visualized radiographically. MP, metacarpophalangeal.
Stener’s lesion is a complete rupture with displacements of the ligaments above the adductor aponeurosis such that it cannot heal back to bone (Fig. 9) (71,90,92,107). There are many diagnostic tests from x-ray to ultrasound, magnetic resonance imaging, and arthroscopy to confirm this diagnosis, but the clinical examination with routine x-rays is still the most consistent (64,70,79,81,82 and 83,85,88,92,95,96 and 97).
In choosing treatment, when the joint is stable or with only mild laxity, with or without a fracture, casting for 4 to 6 weeks is sufficient (108). If the joint is unstable, fixation is required and can be performed with multiple techniques (70,80,86,88,89,91,92,94,109). These range from pullout sutures to K-wires, tension band wires, and screws for bony fragments large enough to suture anchors.
The outcomes for ulnar collateral ligament repairs have revealed that cast immobilization in avulsion fractures can still lead to a poor result but, after open reduction and internal fixation, can have satisfactory result (84,94). This is because the fractures, even though appearing minimally displaced, can actually be rotated. Nonunion can result in 25% of fractures, but the MCP joints are still stable (93).
The attachment site of the ligament is also important, and care needs to be taken that the repair is anatomic. If

palmar in its placement, radial deviation increases from 18 to 27 degrees; dorsal placement causes a similar increase in radial deviation. Placement too distal or proximal results in a decreased range of motion at the MCP joint (87,110). Repair of the dorsal and volar structures at the time of fixation is critical to the success of the outcome, as these structures control supination and volar translation of the proximal phalanx on the metacarpal (87).
The radial collateral ligament is a far rarer injury than that of the ulnar collateral ligament but can be approached in a similar manner (65,77,111). If there is motility of more than 30 degrees and volar subluxation, a repair of the ligaments needs to be performed surgically.
MCP dislocations are most commonly hyperextension injuries, and displacement is dorsal. These are associated with sesamoid fractures. The majority is stable and can be treated by immobilization. For those that are irreducible, usually with volar dislocation or interposition of FPL, sesamoids, or volar plate within the joint, an open reduction with repair of ligaments is necessary (49,55,65,73,82,105,112,113,114 and 115).
Thumb MCP joint ligament injuries are rare. They tend to be associated with other injuries such as fractures at the base of the metacarpal, trapezoid fractures, and even distal radius fractures (65,116,117,118,119,120,121,122 and 123).
The anterior oblique ligament is responsible for the subluxation and/or dislocation of the CMC joint (124). If the joint is stable, casting for 4 to 6 weeks is usually sufficient. If there is instability with subluxation of the metacarpal at the CMC joint, an acute or chronic repair reconstruction is necessary. This repair reconstruction can be accomplished using the FPL tendon to recreate the ligament (119,125,126,127,128,129 and 130).
Patients who undergo ligament repairs infrequently progress to degenerative disease (8% of the time). In those who do develop basal joint arthritis, it is possible to relieve their symptoms and restore function with a CMC arthroplasty (131).
The CMC joint rarely dislocates, but when it does, it dislocates dorsally. The ligaments are disrupted dorsally, and the volar ligaments are stripped subperiosteally from the meta-carpal (132,133,134,135 and 136). Tears can be partial or complete, causing variable degrees of displacement of the metacarpal in the trapezium. If the joint is reduced in spite of a dislocation, usually casting is sufficient (137,138 and 139). If the joint is subluxating or dislocating, it is necessary to perform a more formal repair such as the Eaton/Littler’s technique described below (6).
The ligament that stabilizes the thumb CMC joint is the volar oblique ligament. Therefore, it is this ligament that must be reconstructed to stabilize a subluxating CMC joint of the thumb. A volar approach is used. The thenar muscles are reflected toward the palm. The joint is then exposed, reflecting the volar radial capsule and removing any structures that may be within the joint preventing reduction. An interosseous channel in the first metacarpal is created from dorsal to volar, parallel with the metacarpal joint surface. The flexor carpi radialis then donates one-half of its width, leaving the donated tendon’s insertion at the second meta-carpal intact. The tendon strip is routed through the meta-carpal from volar to dorsal using a loop of wire to grab the tendon and pull it through the channel. The joint is reduced, and the tendon sewn to dorsal periosteum, setting a tension that maintains the reduction. Any remaining tendon is passed underneath the APL insertion and back to the flexor carpi radialis tendon. Sewing it securely at each of these points, it is possible to set the tension too tight, thus restricting motion at the CMC joint.
It is sometimes necessary to pin the MCP joint in 20 degrees of flexion. This is done to prevent hyperextension at the MCP joint and maintain the position of the CMC joint. The cast and the pin, if used, are removed at 4 to 6 weeks postoperatively and progressive range-of-motion exercises are begun.
Elmaraghy (140) makes several points in critique of this repair. Donor tendons require longer incisions, a ligament is replaced by tendon, use of the FCR may compromise future reconstructions of the thumb, and this repair does not simulate the volar oblique ligament well. Elmaraghy describes a repair using the transverse carpal ligament flap based on the palmar tubercle of the trapezium. There is no report of this being performed clinically yet.
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