Carpal injuries represent 3% to 9% of all sports-related ailments, and carpal fractures constitute 8% to 19% of hand injuries. These injuries tend to be sport specific, and timely diagnosis is critical. Treatment is tailored according to severity, concomitant injuries, and potential consequences for late disability. The challenge in management is to discriminate between injuries that will allow early return to play and those that place the athlete at risk for future pain and dysfunction if not managed aggressively from the outset. Open communication among the athlete, the trainer, and the physician is paramount. This chapter reviews carpal anatomy and kinematics, patterns of injury, and management options.
Wrist Biomechanics
The wrist is a diarthrodial joint composed of eight carpal bones arranged in two rows. The geometry of the carpal bones and their attachments allows motion in two primary planes: flexion-extension and radial-ulnar deviation. The flexion-extension arc is derived from roughly equal motion through the radiocarpal articulation and the midcarpal articulation. Radial-ulnar deviation is similarly distributed, with the radiocarpal joint contributing 40% and the midcarpal joint contributing 60%.
Several theories have been proposed to explain carpal kinematics and function. Bryce described carpal bone motion based on radiographs of his own wrist. Since then, several tools have been used to evaluate wrist motion, including uniplanar radiographs, measurement of inserted wires into individual carpal bones, fluoroscopy, cineradiography, stereoscopic measurement, light-emitting diodes, and three-dimensional computed tomography (CT) imaging.
Navarro proposed that the carpus was arranged in three rigid, vertical columns. The central column (lunate and capitate) provided a base for axial loading. The medial column (triquetrum, pisiform, and hamate) created a pivot point around which the carpus could rotate. The lateral column (scaphoid, trapezium, and trapezoid) acted as a “mobile linkage column.” Taleisnik modified the three-column concept in 1976 by including the trapezium and trapezoid in the central column while eliminating the pisiform from the medial column. In 1984, Weber introduced the longitudinal column theory of a force-bearing column and a control column. The force-bearing column consisted of the radius, lunate, capitate, trapezoid, and the proximal two thirds of the scaphoid. The control column included the ulna, ulnocarpal complex, triquetrum, hamate, and fourth and fifth metacarpal bases. The column theories provided a model to account for axial load transmission from the hand to forearm, but they failed to explain the coupled motion between the proximal and distal rows. Additionally, they did not account for the small but significant independent motion present between carpal bones.
The row theory was introduced in the 1980s and suggested that the proximal and distal rows behaved as separate functional units. The distal row was fixed to the metacarpal bases with very little intercarpal motion, creating a distal hand segment. The forearm comprised the proximal stable segment. The proximal carpal row was the intercalated segment, with freedom of motion due to the bony configuration and ligamentous attachments. The scaphoid was thought to serve as a linkage and strut mechanism that maintained the integrity of the intercalated segment under axial loading forces. Years earlier, Linscheid and colleagues recognized that no muscles or tendons insert on the proximal carpal row, and as a result, they proposed that the scaphoid, lunate, and triquetrum acted as an intercalated segment between the rigid distal carpal row and the radius and ulna. The interosseous ligaments between the bones and the articular geometry allowed them to move in unison during wrist motion.
Linscheid and Dobyns and Weber observed carpal motion in the radial-ulnar plane and formulated different theories on the mechanics involved. Linscheid and Dobyns noted that as the wrist radially deviates, the scaphoid and proximal row flex. They believed that scaphoid flexion occurred in response to the pressure exerted by the trapezium and trapezoid. Weber postulated that it was the helicoid geometry of the triquetrohamate articulation that forced the distal row to translate palmarly during radial deviation. Volar translation of the distal row created a flexion moment on the proximal row. Conversely, Weber reported that during ulnar deviation, the distal row is forced to translate dorsally, creating an extension moment on the proximal row.
Different theories on kinematics have provided a greater understanding of the coordinated motion between rows and the tendencies for abnormal motion when the system breaks down. Gilford and colleagues took note of the flexion and extension motion of the wrist and the relative contributions from the radiolunate and lunocapitate articulations. They thought that each row rotated around a single axis of rotation located around its proximal articular surface. They observed the instability of the arrangement and believed that the scaphoid was part of both rows and functioned to “link” the radius and the distal carpus, offering stability to an otherwise “unstable” system. The oval ring concept was initially introduced by Lichtman and colleagues, who thought that the circular arrangement of ligaments provided a continuum of stability and allowed for reciprocal motion between the proximal and distal rows. The rows are linked by the scaphotrapezial joint (mobile radial link) and the triquetrohamate joint (rotatory ulnar link).
Because no one concept adequately describes the complexity of carpal motion, most investigators agree that carpal kinematics can be best explained by a combination of theories. It is evident that in the intact wrist, a balanced synchrony exists between the carpal bones and between the proximal row and distal row.
Ligament Anatomy and Mechanics
Intrinsic and extrinsic ligaments of the wrist link and stabilize the carpal bones. Intrinsic ligaments, also known as interosseous ligaments, connect carpal bones to one another. Extrinsic ligaments connect the carpal bones to the radius and ulna and tend to be stronger than their intrinsic counterparts. Two intrinsic interosseous ligaments are found in the proximal row (the scapholunate and lunotriquetral ligaments) and three are found within the distal row (the deep capitolunate, deep trapeziocapitate, and trapeziotrapezoid ligaments). Extrinsic ligaments are classified as either volar or dorsal. Dorsal extrinsic ligaments include the dorsal radiocarpal and dorsal intercarpal ligaments. There are four volar radiocarpal ligaments (the radial collateral, radioscaphocapitate, long radiolunate, and short radiolunate), four volar ulnocarpal ligaments (the ulnar collateral, ulnotriquetral, ulnolunate, ulnocapitate), and one volar deltoid intercalated ligament. Volar extrinsic ligaments are thicker and stronger than the two dorsal ligaments. As noted earlier, tendons do not directly insert on the carpals (except the pisiform) but help to stabilize their motion when actively contracting. Wrist motion is initiated by the distal carpal row and metacarpals, which move as a unit. During wrist flexion, the distal row flexes and the ulnar deviates. As the distal row flexes, the proximal row flexes. Conversely, with wrist extension, the distal row extends and radially deviates. As the distal row extends, the proximal row extends. Radial deviation of the wrist causes the distal row to incline radially, extend, and supinate, which leads the proximal row to flex and translate in an ulnar direction. During ulnar deviation, the distal row inclines ulnarly, flexes, and pronates, causing the proximal row to extend and translate in the radial direction.
Carpal Instability
Carpal instability is a broad term used to describe the carpal position that results after disruption to bone and/or wrist ligaments. Acute instability usually results from violent trauma, such as a fall or a motor vehicle collision. Injury to an interosseous ligament can cause dissociation between carpal bones of a row. The most commonly injured structures are the scapholunate interosseous ligament between the scaphoid and lunate and the lunotriquetral interosseous ligament between the lunate and triquetrum. The thickest region of the scapholunate ligament is dorsal, whereas the lunotriquetral ligament is strongest volarly. Injury to these structures and adjacent extrinsic ligaments leads to altered carpal mechanics, called carpal instability dissociative . Disruption that alters motion between the proximal and distal carpal rows has been termed carpal instability nondissociative . A multiligamentous disruption occurring both within a row and between rows has been designated carpal instability complex .
Scapholunate and Lunotriquetral Injuries
A wrist hyperextension or hyperflexion injury places the athlete at risk of an intercarpal ligament tear. Scapholunate tears primarily affect proximal row mechanics. An associated injury to a secondary soft tissue restraint, such as the volar radiocarpal extrinsic ligaments, will allow the scaphoid and lunate to rotate independently, aptly termed scapholunate dissociation . Depending on the severity of energy, the spectrum of scapholunate injuries can vary from dynamic instability to static dissociation with dorsal intercalated segmental instability. Observational studies have shown that when these injuries are left untreated, a predictable pattern of carpal deterioration occurs, starting at the radioscaphoid joint and proceeding to the capitolunate joint, which is known as the arthritic progression of scapholunate advance collapse. Lunotriquetral tears usually have an associated dorsal radiocarpal ligament tear, as well as an ulnocapitate ligament injury. Lunotriquetral injuries also disrupt the synchrony of the proximal row; the scaphoid and lunate can be observed to flex together after injury, also known as volar intercalated segmental instability (VISI).
Patients with symptomatic scapholunate dissociation present with dorsal wrist pain and swelling, along with reduced wrist motion and grip strength. Examination may reveal tenderness over the carpus, a prominent proximal pole of the scaphoid, boggy synovitis over the radioscaphoid joint, and even a palpable gap at the scapholunate interval. Specialized tests can aid in making the diagnosis. For example, the Watson test examines the integrity of the scapholunate ligament. The examiner places gentle pressure on the distal pole of the scaphoid as the wrist is moved from an ulnar deviated position to a radially deviated position. A palpable clunk and pain occur as the scaphoid subluxes dorsally over the rim of the distal radius. The shear test assesses lunotriquetral stability. The examiner stabilizes the lunate by exerting gentle dorsal pressure and loads the pisotriquetral joint in the anteroposterior plane. Pain may signal a lunotriquetral injury.
Plain radiographs are obtained with contralateral views if the changes are subtle. Standard orthogonal views should be scrutinized for incongruity of arcs, intercarpal distance abnormalities, and disruption of angular associations between carpal bones ( Fig. 74-1 ). Normal balance is assessed by the collinear alignment of the radius, lunate, capitate, and third metacarpal. Deviated values for the scapholunate angle (30 to 60 degrees), radiolunate angle (<15 degrees), and carpal height ratio (>0.5) provide objective evidence for injury.
Posteroanterior (PA) and lateral views can demonstrate static instability patterns. Static instability is defined as carpal instability that can be detected with standard radiographs. PA views that demonstrate a cortical ring sign direct the clinician to consider a scapholunate ligament or lunotriquetral injury. The appearance of a cortical ring is consistent with a palmar flexed scaphoid in which the distal pole cortex is seen on end. If lunotriquetral dissociation is present, the lunate will be palmar flexed and appear triangular on the PA image; the scapholunate angle will be less than 30 degrees on the lateral view. Scapholunate dissociation, on the other hand, will demonstrate scapholunate widening of greater than 3 mm on the PA film, and a scapholunate angle of greater than 70 degrees will be present on the lateral view. Dynamic instability patterns require special views (i.e., axial loading view, ulnar deviation view, clenched fist view, and distraction view) to illuminate carpal malalignment. Radiographs should also be examined to decipher the chronicity of injury. Arthritis of the radial styloid, radioscaphoid, and midcarpal joints or carpal collapse indicates that the injury did not occur in the acute or subacute time frame. Computed tomography (CT) scans, fluoroscopy, and magnetic resonance imaging (MRI) arthrograms with gadolinium may all be useful adjuncts to plain images.
Partial tears of the scapholunate ligament may respond to immobilization. Arthroscopic debridement has been shown to be a satisfactory option for partial injuries, but it is less effective for complete tears.
Various surgical procedures have been developed to address complete injuries with scapholunate dissociation to improve pain and function while preventing the potential for delayed carpal arthritis. The existing literature suggests that operative treatment is necessary and that acute intervention affords favorable outcomes. However, this type of injury places the elite athlete in a difficult situation. Treatment means loss of the season, and full recovery of strength and motion is rare. Athletes often present weeks to months after sustaining what was thought to be a “sprained” wrist. Delayed treatment results in a worse ultimate outcome, and even with treatment, it cannot be guaranteed that posttraumatic arthritis will be avoided. The scenario that leads to the most difficulty in making a treatment decision is when an athlete presents 3 months after injury with nearly full motion and minimal discomfort. A frank discussion should include the option of providing no treatment with the possibility of performing reconstructive surgery in the future.
In the acute setting, ligament repair and Kirschner (K) wire fixation have been used in combination to maintain carpal alignment. Wires are inserted into the carpus to assist in reduction of the scapholunate or lunotriquetral articulations. Once reduction has been achieved, the scapholunate interosseous ligament is repaired with suture anchors. The carpus is then stabilized with 0.045-inch wires. In lunotriquetral injuries, pinning of the lunotriquetral joint without ligament repair seems to be sufficient. A recent biomechanical study evaluated the loads to failure after five different K wire configurations for scapholunate dissociation. The cadaveric study found no significant difference in load to failure for scapholunate fixation using one or two wires; however, scapholunate pinning coupled with scaphocapitate fixation achieved the greatest stabilization of both carpal rows.
Dorsal capsulodesis can be used to augment the repair. Slater et al. released the dorsal intercarpal ligament from the trapezoid and fixed it to the scaphoid, thereby tethering the scaphoid and triquetrum. Recently, ligamentoplasty of the dorsal intercarpal ligament has gained popularity. This procedure involves splitting the proximal portion of dorsal intercarpal ligament and advancing it proximally to recreate the dorsal component of the scapholunate ligament. It has been suggested that repair should be performed within 3 weeks, but delayed repair has been performed with success up to 6 months after the injury occurred. A retrospective review following outcomes of 17 patients who had scapholunate dissociation that was treated with interosseous ligament repair and dorsal capsulodesis, with follow-up for 61 months, showed that favorable short-term (1- to 2-year) outcomes may deteriorate over time in patients who place high demands on their wrist. Other options for stabilization of the scapholunate joint include Brunelli reconstruction or three-ligament tenodesis reconstruction using the flexor carpi radialis (FCR) tendon to reconstruct the scapholunate interosseous ligament. The reduction and association of the scaphoid and lunate procedure using a screw has been performed both as open surgery and arthroscopically. Some persons have theoretical concerns that this procedure does not reproduce the complex kinematics of scapholunate motion. However, no procedure consistently stabilizes the scapholunate joint in the setting of a subacute or chronic injury.
When the scapholunate joint is not reducible or when posttraumatic arthritis is present, the remaining options are proximal row carpectomy or scaphoid excision with capitolunate fusion plus or minus incorporation of the hamate and triquetrum in the fusion mass. In the general population, we would choose a proximal row carpectomy in a patient 50 years or older or in a younger patient who is a smoker. In athletes with disabling pain who place a high demand on their wrist, we would offer a scaphoid excision and capito-lunate-triquetrum-hamate fusion.
Perilunate Instability
Perilunate instability is a type of carpal instability complex and represents 7% of all injuries involving the carpus. In this case, the carpal anatomy is disrupted in a predictable manner. Progressive ligament and bone dissociation are dependent on the degree of force imparted on the wrist. The defining feature of the perilunate injury is dissociation of the capitate from the lunate; 95% to 97% are dorsal perilunate dislocations (i.e., dorsal displacement of the capitate with respect to the longitudinal axis).
Cadaver wrists loaded in wrist extension, ulnar deviation, and intercarpal supination produce a characteristic sequence of carpal disruption around the lunate as described by Mayfield and colleagues. This sequential disruption occurs in four stages. In stage I, the scapholunate ligament is disrupted and the radioscapholunate ligament is torn. The force is then transmitted to the lunocapitate articulation, where the capitate dislocates (midcarpal dislocation). Stage II is accompanied by injury to the radioscaphocapitate ligament, dorsal intercarpal ligament, and radial collateral ligament. In stage III, energy propagates into the lunotriquetral joint, tearing the lunotriquetral ligament. A triquetral dissociation results, but the lunate remains aligned with the radius. Finally, in stage IV, the lunate dislocates as a result of ulnotriquetral and dorsal radiocarpal tears. The lunate no longer remains within the lunate fossa of the radius and displaces volarly. The volar extrinsic ligaments, which usually remain intact, cause the lunate to rotate into the carpal tunnel.
Perilunate instability can occur via ligament injury alone or in combination with fracture, and consequently such cases are subdivided into perilunate dislocations and perilunate fracture dislocations. Lesser arc injuries describe those that involve only ligamentous disruption. Greater arc injuries describe a fracture of a bone or bones around the lunate. With greater arc injuries, the “trans-” prefix is used to describe the fractured bones involved. Although Gilula originally described the normal arcs for radiographic interpretation in his classic article in 1979, Johnson classified them into lesser arc and greater arc injuries. Recently, Bain and colleagues have modified Johnson’s classification to describe a third pattern of injury termed translunate arc, which occurs through the lunate ( Fig. 74-2 ).
Common variants of perilunate injuries are transscaphoid or transstyloid injuries. Uncommon variants include transtriquetral and transcapitate injuries. Patients frequently describe a high-energy injury and present with a swollen and painful wrist. The carpus is most commonly dislocated dorsally, and physical examination reveals a prominent, palpable capitate. In acute injuries, soft tissue swelling may obscure bone landmarks. If the lunate is dislocated, it can encroach on the carpal tunnel and cause symptoms consistent with median nerve compression. The incidence of acute carpal tunnel syndrome with perilunate injuries ranges from 16% to 46%.
Standard orthogonal views are ordered to evaluate for injury. The PA view will demonstrate a loss of carpal arcs. The scaphoid and lunate will fall into a flexed position, and a cortical ring sign directs the clinician to consider a scapholunate and/or lunotriquetral ligament injury. The lunate will appear triangular and will be displaced relative to the extent of energy imparted. Loss of articular alignment, overlap of carpal bones, and fractures may also be present. The lateral image will demonstrate alteration of the collinear alignment of the radius, lunate, and capitate. The capitate is commonly displaced in a dorsal direction, and the lunate is displaced volarly. The lunate may be rotated 90 or 180 degrees, resembling a spilled teacup. CT can delineate subtle fracture lines that may be present.
Treatment for perilunate injuries has evolved over the years and includes closed reduction and immobilization, closed reduction and percutaneous fixation, external fixation combined with or without internal fixation, open reduction and fixation with K wires or screws, lunate excision, proximal row carpectomy, and four-corner fusion.
Initial closed reduction will relieve pressure on the median nerve and prevent further cartilage damage. Closed reduction by itself is rarely a definitive treatment, because restoration of anatomy is critical to optimize healing of ligaments and fractures. Persistent and evolving carpal tunnel symptoms following closed reduction necessitates emergent surgical intervention to release the transverse carpal ligament. Open injuries or the inability to achieve anatomic restoration after closed reduction are also indications for open treatment. If reduction is acceptable and median nerve symptoms are mild or nonprogressive, it is reasonable to perform delayed open reduction and fixation to ensure anatomic alignment. We know of no evidence that defines the time limits of when surgical treatment can be performed without compromising outcomes. However, conventional wisdom suggests that open reduction and internal fixation is best performed within the first few weeks after injury. A dorsal approach, volar approach, or combined dorsal and volar approach may be necessary and is often decided on the basis of the surgeon’s preference.
The dorsal approach provides easy visualization for carpal reduction, interosseous ligament repair, and fracture fixation. The volar approach allows decompression of the carpal tunnel and palmar capsule repair. Extensive volar dissection should be avoided, because Sotereanos et al. reported a case of flexor tendon adhesions after a combined volar approach with exploration and ligament repair. The technique for fixation varies but can include K wires, headless compression screws, and lag screws ( Fig. 74-3 ). Transscaphoid fractures can be treated with or without a bone graft from the distal radius; scaphoid comminution is a good indication for grafting. After open reduction and internal fixation of the scaphoid in transscaphoid perilunate dislocations, it is important to evaluate the integrity of the scapholunate and lunotriquetral ligaments. Garcia-Elias and colleagues found that transscaphoid patterns have a 3.8% incidence of concomitant complete scapholunate disruption. Stabilization with K wire fixation has been described, but ligament repair and K wire fixation seems to offer better maintenance of carpal alignment. Repair is assumed to confer improved patient outcomes, but this assumption has not been proved in the literature. K wires can be useful as joysticks to obtain adequate reduction of the scapholunate and lunotriquetral articulations. The scapholunate interosseous ligament often tears from the scaphoid and can be repaired with braided polyester sutures ( Fig. 74-4 ). The mechanically important portion of the lunotriquetral interosseous ligament is on the volar surface of the lunotriquetral joint. Because most of these injuries are amenable to a purely dorsal approach, pinning of the lunotriquetral joint without ligament repair seems sufficient ( Fig. 74-5 ).
The extent of chondral injury should be documented during the procedure. Because the capitate dislocates dorsally, a characteristic shearing or impaction lesion is often present on the capitate head. Neurovascular checks should be performed as part of the preoperative and postoperative protocol. After surgery, a cast is typically used for 8 weeks and a splint is used for an additional 4 weeks. If K wires are used for fixation, they are typically removed at 12 weeks, although lunotriquetral K wires are usually removed in 4 to 6 weeks.
The recent popularity of arthroscopic-assisted percutaneous fixation for scaphoid fractures has spurred use of these alternative treatment options for transscaphoid perilunate dislocations. Although results have demonstrated good functional outcomes in midterm follow-up (i.e., evidence of radiographic union and a low morbidity/complication rate), the authors caution that larger series with matched control subjects and long-term follow-up are needed to provide more information regarding the advantages and disadvantages of this technique.
Results following perilunate injuries depend on the severity of the initial injury, accurate and timely diagnosis, and the quality of the reduction ( Fig. 74-6 ). Patients should be counseled that loss of motion and diminished grip strength are common consequences despite appropriate treatment, as is the risk of posttraumatic arthritis. Athletes should understand that this injury could end their career.
Scaphoid
The scaphoid is the most commonly injured carpal bone. According to Kozin, the true incidence is unknown but has been reported to be as high as 68% of carpal bone fractures. Scaphoid injuries occur from falls onto an outstretched hand. The wrist is loaded in a position of hyperextension and slight radial deviation, according to Weber and Chao, or slight ulnar deviation, according to Mayfield. An axial load to a clenched fist has also been described.
Avulsions of the scaphoid tubercle can occur because of the strong volar ligaments. Other patterns of injury include waist (the most common), distal pole, or proximal pole fractures. Proximal pole fractures can be problematic because of interruption of the integrity of the dorsal vascular supply and retrograde intraosseous blood flow.
Standard PA, lateral, and oblique views can demonstrate the fracture pattern. PA views with the wrist in ulnar deviation place the scaphoid in an extended position. False-negative results on initial plain radiographs have been estimated to be as high as 25%. Conventional wisdom suggests that patients with anatomic snuffbox tenderness should have their wrist immobilized and be reevaluated in 2 weeks. Studies have demonstrated, however, that follow-up radiographic views may not be more revealing than initial injury films. Performing additional studies early in an acutely injured athlete can help define the injury and can be cost-effective. Intraosseous edema on T2-weighted MRI may be the only evidence of an otherwise occult fracture of the scaphoid. A CT scan best defines whether the fracture is displaced or angulated but also may be used to diagnose the radiographically occult scaphoid fracture if MRI is not available.
Nondisplaced fractures in the waist and distal pole of the scaphoid have a high rate of healing with cast immobilization. Whether the cast should be long arm, short arm, or extend over the thumb is still debatable. Nonskill position players (e.g., a football player who does not have to handle the ball) can be treated with a padded short-arm thumb-spica cast for most nondisplaced fractures, with the caveat that they may be increasing their risk of nonunion. Athletes who require wrist motion to perform (e.g., a quarterback, running back, or wide receiver in football) may be able to return to play earlier with immediate internal fixation using open, percutaneous, or arthroscopic-assisted approaches ( Fig. 74-7 ). Immediate fixation also may be recommended for nondisplaced proximal pole fractures, which carry a higher risk of nonunion.
For athletes who choose immediate fixation, we prefer arthroscopic-assisted fixation. A 1-cm incision is made in the soft spot between the extensor pollicis longus and extensor digitorum communis. The proximal pole of the scaphoid and the scapholunate ligament are visualized with the wrist flexed. The guide wire for a cannulated screw is inserted down the central axis of the scaphoid in line with the thumb metacarpal. The wire is advanced until it exits the skin overlying the distal pole of the scaphoid. The wire is withdrawn until it is flush with the surface of the scaphoid. The wrist is extended and fluoroscopy is used to confirm central placement of the wire. The wrist and hand are then placed in an arthroscopic wrist tower. The midcarpal joint is entered via the radial midcarpal portal with a 2.7-mm arthroscope. The reduction of the fracture is evaluated. If unexpected step-off or malrotation is encountered, the wire is withdrawn until the proximal pole disengages. Percutaneous joysticks can be placed into the fracture fragments to facilitate reduction of the fracture. The guide wire is advanced into the proximal pole. The wrist is taken out of the tower, and the wrist is flexed. The guide wire is advanced out of the mini open incision. Drills are passed over the wire. Displaced fractures require internal fixation to realign carpal anatomy. Both volar and dorsal approaches have been used; we prefer the dorsal approach for fixation of the most proximal fracture patterns.
Treatment results for scaphoid fractures improve when the injury is addressed early. A delay in diagnosis can lead to malunion or nonunion, causing secondary carpal instability and early posttraumatic osteoarthrosis.
Triquetrum
The triquetrum is the second most commonly injured carpal bone, representing 3% to 5% of all carpal fractures. Fracture patterns include dorsal cortical fractures and fractures through the body. Dorsal cortical fractures are more prevalent, accounting for 93% of all triquetral fractures. The mechanism of injury for dorsal cortical fractures primarily involves either palmar flexion and radial deviation or dorsiflexion and ulnar deviation of the wrist. During wrist dorsiflexion and ulnar deviation, it is surmised that the ulnar styloid drives into the triquetrum, leading to a “dorsal chip.” Triquetral body fractures occur with the wrist in extension and ulnar deviation. Body fractures typically follow high-energy mechanisms, and the clinician should suspect related injuries. Perilunate dislocations are present in 12% to 25% of body fractures.
Considering the likelihood of concomitant injuries, eliciting point tenderness over the triquetrum may be challenging. Pain with wrist motion is often present with dorsal avulsion injuries. PA, lateral, and oblique plain radiographs are typically sufficient for the diagnosis of a triquetral fracture. CT can be useful to identify the occult fracture.
Dorsal cortical fractures can be treated with a brace or a short-arm cast for 3 to 6 weeks ( Fig. 74-8 ). Athletes should be counseled regarding fracture fibrous union, a common result with little potential consequence. A cast or splint is applied for 1 week and the athlete is reexamined at weekly intervals until he or she is ready for unrestricted play. An MRI can be ordered in instances in which recovery does not progress and a concurrent scapholunate or lunotriquetral tear is suspected.
The guidelines for treatment of the triquetral body fracture are less clear. Some authors advocate open reduction and internal fixation. When a triquetral fracture is associated with a perilunate dislocation, it is our practice to pin the lunotriquetral joint along with the scapholunate joint and midcarpal joints, bypassing fixation of the triquetral fracture. In cases of symptomatic malunion, nonunion, or pisotriquetral arthritis, excision of the pisiform may provide adequate symptom relief.
Hamate
Hamate fractures represent close to 2% of all carpal fractures. The hamate lies in close proximity to surrounding neurovascular structures. It forms the radial border of the Guyon canal and serves as an attachment site for the transverse carpal ligament. As a result, hamate injuries may lead to paresthesias and/or motor dysfunction in the ulnar or median nerve distribution ( Fig. 74-9 ). The superficial position of the hook predisposes it to injury from compressive trauma to the palm. Missed hamate fractures are common.
Mechanisms of injury for fractures of the hook of the hamate involve direct compression or shear forces from adjacent tendons during forceful twisting of the wrist. The most common activities relating to this injury include baseball, golf, and various racquet-related sports. Body fractures of the hamate, on the other hand, may occur as a result of axial loads through the fourth and fifth metacarpals. These fractures are classified as either coronal or transverse. Carpometacarpal dislocations can accompany these injuries ( Fig. 74-10 ).
Hamate fractures present as ulnar-sided wrist pain. Pain over the ulnar side of the palm may be worsened with grasping. Tenderness can often be elicited over the hook. Resisted finger flexion with the wrist in ulnar deviation is a useful provocative maneuver for detecting an injury ( Fig. 74-11 ). A thorough motor and sensory examination is important. Irritation of the adjacent ulnar nerve may lead to paresthesias. Abrasion of the adjacent flexor tendons against the fractured hook may lead to tendinosis or flexor tendon rupture ( Fig. 74-12 ).
A cortical circular ring, representing the end-on view of the hook of the hamate on standard PA views, may be missing on injury radiographs. When images demonstrate increased sclerosis around the circular ring, a nondisplaced nonunion should be considered. The fourth and fifth metacarpals must be inspected for injury or dislocation, especially on PA and lateral images. A CT scan is used when suspicion is high for an occult fracture versus an anatomic variant, the os hamuli ( Fig. 74-13 ). If CT is not available, specialized radiographic views can assist with diagnosis and include (1) the carpal tunnel view, (2) the supinated oblique view with the wrist in dorsiflexion, and (3) the lateral view through the first web with the thumb abducted ( Fig. 74-14 ).
Displaced hamate body fractures are treated with open reduction and internal fixation. Despite reports that strength diminishes with removal of the hamate hook, we prefer hook excision for both acute fractures and nonunion. Excision, in our experience, offers a predictable outcome—a mild loss of grip that does not seem to adversely affect even professional athletes and allows early return to play.
When approaching the hook of the hamate, particular attention should be directed to the proximity of the deep motor branch of the ulnar nerve. An S-shaped incision is centered over the hook. We avoid crossing the wrist flexion creases to minimize scar sensitivity and facilitate return to play. The ulnar nerve and artery are dissected proximal to distal toward the hook. The ulnar motor branch, which exits dorsal and ulnar to the ulnar nerve proper, dives deep as it travels in a radial direction toward and around the ulnar border of the hamate hook. Once mobilized and retracted, the hook can be exposed; the periosteum is elevated, and the hook is uncovered. Removal of the entire hook is preferred to avoid irritating the adjacent flexor tendons with residual exposed bone ( Fig. 74-15 ).
