Introduction
Carpal fractures account for approximately 18% of fractures of the hand, and between 60% and 85% of them are injuries to the scaphoid. The incidence of other carpal fractures also varies depending on the literature source. The second most common carpal fracture are injuries to the triquetrum (15%–18%). The remaining carpals are less frequently involved: trapezium (4%–5%), lunate (1%–4%), capitate (1%–2%), hamate (1%–2%), pisiform (1%–2%), and trapezoid (<1%). In other words, carpal fractures apart from the scaphoid are infrequent. ,
Due to the rarity of those injuries, experience treating them is often limited, with indications for operative or conservative treatment being controversially discussed and based on personal experiences, single case reports, or small case studies.
Important requirements treating these injuries properly are a broad understanding of the underlying anatomy as well as the pathomechanisms that lead to certain fractures.
First of all, knowing about the particular fractures enables one to correctly make the diagnosis and avoid missing less obvious injuries. Second, by understanding the underlying trauma mechanism, ligamentous lesions can be excluded.
Trying to classify the specific fractures in regard to functional units of the individual carpals helps to judge whether there is an unstable situation needing reduction and fixation or whether conservative treatment with immobilization is appropriate. Possible complications such as posttraumatic joint degeneration, avascular necrosis, nonunion, and tendon rupture also have to be considered.
Over the last decades, the development of smaller fixation devices has presented new treatment options. In combination with the fact that most carpal fractures occur in young and active individuals with high demand, there is an increasing trend toward surgery.
Essential knowledge
Anatomy
The carpus has a highly complex arrangement of small joints that interact with each other during wrist motion. , The bones of the distal row and the bases of the metacarpals, with exception to the first carpometacarpal joint, are connected to each other with short, stout ligaments that allow only minimal motion in the carpometacarpal joints II to V and between the carpals of the distal row. They form an amphiarthrosis, which is a true joint with minimal range of motion. So an axial force is directly transmitted via the carpometacarpal (CMC) joints to the carpal bones in the distal row.
The intercarpal connection of the proximal row is less rigid, which allows more movement between the bones during wrist motion. For example, there is a difference in rotation between the scaphoid and lunate from extension to flexion of about 30 degrees. There are no tendon attachments to the proximal row; therefore it is often referred to as an intercalated segment. So in contrast to the distal row the whole proximal row is highly mobile and balanced between the joint surfaces of the radius, the ulna, and the distal row. As a result, the main trauma mechanisms leading to fractures of the proximal row are extreme wrist extension or flexion.
Furthermore, there are accessory bones that can mislead the interpretation of an x-ray and resemble a fracture. These anatomical variations are important in the differential diagnosis of an apparent fracture in the face of minimal trauma or an unusual clinical presentation.
The blood supply to the carpus occurs via three dorsal and three palmar transverse arches that originate from the radial and ulnar arteries as well as from the palmar and the dorsal branches of the anterior interosseus artery. Several longitudinal and transverse anastomoses connect the arches together. In general, the nutrient vessels to the individual carpals enter the bones on their noncartilaginous surfaces, often in the area of ligament attachments. Panagis et al divided the interosseous blood supply to the carpals into three groups with different patterns of vascularization.
Group 1 consists of the ones with only a single area where vessels enter the bone or with large areas of bone supplied by a single vessel. This group includes the scaphoid, capitate, and those lunates supplied by a single palmar nutrient artery (approximately 20%).
Group 2 includes the carpals that have at least two surfaces with perforating vessels but no intraosseous anastomoses between the separate areas. Group 2 includes the hamate and the trapezoid. The body and the hook of the hamate have separate blood supplies without anastomoses.
Group 3 comprises the carpal bones that have several areas of vessel penetration as well as numerous intraosseous anastomoses between the separate perforators. Group 3 includes the trapezium, pisiform, triquetrum, and 80% of lunates.
From the internal pattern of vascularization, it is possible to make conclusions about the risk of posttraumatic osteonecrosis or nonunion. Those carpal bones with limited blood supply (group 1) are most vulnerable to posttraumatic osteonecrosis. Groups 2 and 3 have a much lower risk for osteonecrosis. The anatomical findings directly correlate with the incidence of osteonecrosis. Numerous publications report cases of posttraumatic osteonecrosis of the scaphoid, lunate, and capitate (all group 1) and the hook of hamate (group 2), whereas nutrition disorders of the remaining carpals are rare. ,
Trauma mechanism
For correct diagnosis, the injury mechanism has to be understood. Apart from a solitary carpal fracture, injuries can occur as part of a larger injury pattern (e.g., greater arc lesions, axial instabilities, carpometacarpal-fracture dislocations). The most common injury mechanisms are either a direct blow to the particular carpal bone, a hyperextension/hyperflexion/axial trauma injury, or a compression injury.
Direct blow: If the force is high enough, a direct trauma to a particular carpal bone can lead to a fracture. Those are mostly high-speed traumas such as traffic accidents and sport injuries. Because of their protected position within the wrist, the central carpals are rarely affected by direct trauma.
Hyperextension trauma: A fall on the outstretched hand is the cause of the majority of carpal fractures. Forced hyperextension of the wrist leads to an impingement of the carpal bones with the dorsal radius lip or the radial or ulnar styloid. Depending on additional radial or ulnar deviation combined with forearm rotation, different fracture patterns can occur.
The most severe injury pattern of a fall on an outstretched hand is a perilunate fracture dislocation or so-called greater arc lesion. The force is transmitted around the lunate, resulting in fractures of the adjacent carpals (scaphoid, capitate, triquetrum). In contrast to the above-mentioned shearing fractures, a greater arc lesion usually results in transverse or sagittal fractures of the body of the involved carpals. ,
Hyperflexion trauma: Analogous to a fall on the outstretched hand is a hyperflexion injury (e.g., motorcycle accident). This can lead to shearing fractures of the palmar parts of the proximal row. Other injuries resulting from hyperflexion trauma are scaphoid waist fractures where the radioscapholunate ligament acts as a pivot point and bony avulsions of the lunotriquetral (LT) ligaments. Both injuries are discussed in different chapters.
Axial trauma: Another mechanism of trauma is an axial injury to one of the digital rays with direct load transmission via the strong CMC-ligament-complex to the carpus. The distal row is usually affected. , , , , , These fractures generally occur in the sagittal or coronal plane. The proximal row is rarely affected.
Compression injury: Another rare but severe trauma mechanism is a forced anterior-posterior compression of the hand resulting in axial instability. The carpus and metacarpus are divided in the sagittal plane adjacent to the capitate. Several subtypes of axial instabilities are described. Besides ligament ruptures and bony avulsions, this can result in carpal body fracture in the sagittal plane. Adjacent carpals of the proximal and distal row are affected. Those injuries are highly unstable and require a rigid fixation. The same injury mechanism can result in avulsion fractures at the attachments of the flexor retinaculum from the ridge of the trapezium or hook of hamate.
Bony avulsions of the very strong intrinsic ligament (e.g., scapholunate interosseus ligament and the lunotriquetral ligament) are covered under “carpal instabilities.”
Clinical presentation and diagnosis
Symptoms and signs
Symptoms are mostly unspecific and include local swelling, hematoma, and localized tenderness. Sometimes specific clinical tests can hint of a fracture. Once a carpal fracture is clinically suspected, radiological diagnosis can be demanding. The first imaging used should always be a conventional radiography in two orthogonal planes.
Plain radiographs
A standardized posterior-anterior (PA) x-ray includes the distal part of the forearm and the proximal part of the metacarpals. It is taken with the shoulder 90 degrees abducted with the elbow flexed 90 degrees and the forearm in neutral rotation. A good reference for the correct rotation is the ulnar styloid, which should be seen on the medial border of the ulnar head. The joint spaces should be visible. Once the quality of the x-ray is approved, one should check for a smooth contour of the arcs of Gilula at the midcarpal joint and a double-M-shaped line at the carpometacarpal joint. Any disruptions of these lines should raise suspicion for underlying joint disorders.
Correct interpretation of a lateral view of the wrist can be challenging. As with the PA view, one should verify the quality of the image before looking for pathologies. Again, the distal forearm as well as the proximal half of the metacarpals should be included. The radius and ulna should be projected over each other and parallel to the third metacarpal. In a true lateral view, the palmar border of the pisiform should be projected in between the palmar borders of the capitate head and the distal pole of the scaphoid. ,
Because of summation effects, the individual carpal bones are often not clearly visible in lateral view; a good way to acquire additional information, especially about the marginal bones, is to view additional images in 45 degrees of internal or external rotation. A carpal tunnel view can help diagnose fractures of the hook of hamate or the ridge of the trapezium. Sometimes diagnosis by conventional radiography is impossible or incomplete. CT may be necessary, especially for further understanding of a certain fracture morphology and to determine whether conservative or surgical management is indicated.
Planning for operative/conservative management
Treatment options vary from conservative treatment to closed or open reduction with internal fixation to primary arthroplasty. Most commonly, Kirschner (K) wires and mini-screws are used for osteosynthesis. To minimize joint damage, headless compression screws are preferred whenever the fracture site includes a cartilage surface. Plates are used only in special cases. In general, a non-displaced or minimally displaced fracture is treated with splinting or casting. Surgery is reserved for a largely displaced fracture which may have longterm consequences.
For choosing the treatment, multiple factors should be taken into account, such as patient’s age, demands, existing osteoarthritis, blood supply to the injured bones, and accompanying ligament injuries.
Treatment methods and different approaches
Lunate fractures
Due to the lunate’s sheltered, central position, it is often referred to as the cornerstone of the wrist and is rarely fractured. Fresh lunate fractures account for 0.5% to 6.5% of all carpal fractures. More often, a lunate fracture results from avascular necrosis. Since the treatment options between those two conditions differ substantially, Kienbock’s disease has to be ruled out through additional imaging (CT and MRI with contrast medium). In the literature, several cases of bipartite lunates are reported so an anatomical variation may be ruled out.
Diagnosis and classification.
Clinical presentation of a lunate fracture is often nonspecific. There can be local swelling and hematoma with tenderness dorsally or volarly over the lunate. After conventional radiology, a CT scan should be obtained to clearly understand the fracture.
Lunate fractures were classified by Teisen et al into five different types: fractures of the volar pole, chip fractures, fractures of the dorsal pole, sagittal fractures, and transverse fractures. These fractures have different underlying injury mechanisms. Volar and dorsal pole fractures are often the result of a bony avulsion of the radiolunate, the dorsal scapholunate, or the radiocarpal ligaments. A chip fracture occurs during a fall on the hyperextended/flexed wrist where the radius lip acts as a chisel. Sagittal fractures are thought to be the result of a fall on the clenched fist with an axial load transmission through the capitate onto the lunate. Those fractures are sometimes accompanied by an additional depression of the lunate’s distal joint surface due to the piston effect of the capitate.
A fall on the outstretched hand in combination with ulnar deviation can result in a transverse (sagittal plane) fracture of the lunate. Often, lunate fractures are accompanied by fractures of the adjacent carpals and/or the distal radius. , , Although perilunate injuries were originally thought to spare the lunate, recent observations suggest that lunate fractures are part of a perilunate injury pattern, namely the translunate arc concept. Therefore one should actively search for signs of radiocarpal or midcarpal instability. ,
Treatment options and aftercare.
Undisplaced fractures without signs of carpal instability can be treated conservatively with 4 to 6 weeks of cast immobilization and regular radiographic controls. Displaced fractures should be openly reduced and fixed with K-wires, mini-screws, or cannulated compression screws. The approach to the wrist is determined by the fracture location. Fractures of the volar pole as well as volar chip fractures are best addressed by an extended carpal tunnel approach.
Fractures of the dorsal pole and transverse body fractures are reached via a dorsal approach through the third and fourth extensor compartment and a ligament-sparing capsulotomy.
In individual cases, small chip fractures can be treated arthroscopically. In the case of an accompanying carpal instability, bony reattachment of the injured ligaments as well as additional K-wire fixation of the adjacent carpal joints may be necessary.
After surgical fixation, 4 to 6 weeks of cast immobilization is necessary. In cases with an underlying carpal instability, immobilization should be extended to 8 weeks to allow adequate healing of the ligaments. In all cases of K-wire fixation, hardware removal should be performed before discontinuation of casting.
Triquetrum fractures
The triquetrum articulates with the lunate, hamate, and pisiform as well as the triangular fibrocartilage complex. The dorsal surface has a large cartilage-free area where several intrinsic and extrinsic ligaments insert. The radiocarpal and the ulnotriquetral ligament reach the proximal border of the dorsal triquetrum as extrinsic ligaments. On the distal half of the dorsal surface is the attachment of the triquetroscaphoid ligament, which is also known as the dorsal intercarpal ligament. Together, the dorsal structures form the so-called dorsal V. ,
Via the insertion of these ligaments, numerous blood vessels enter the bone with several intraosseous anastomoses, resulting in a generous blood supply. No cases of avascular necrosis of this bone after trauma have been described. ,
Diagnosis and classification.
Clinical presentation of triquetral fractures is nonspecific. There is local swelling and tenderness over the fracture site, and this can be accompanied by hematoma. On the lateral view of a conventional radiograph, most dorsal fractures can be diagnosed. Another helpful image for fracture diagnosis through conventional radiography is a 45-degree oblique view, which displays triquetral body fractures. Nevertheless, for further evaluation and treatment considerations, a CT scan is usually indicated.
There are three fracture types: dorsal chip fractures, body fractures, and volar avulsion fractures with several subtypes. , , On the basis of the ligamentous insertions, Garcia-Elias defined four quadrants on the dorsal triquetrum and classified the dorsal chip fractures into six subtypes. There is controversy about the exact trauma mechanism leading to those fractures. Some authors suggest a classic avulsion fracture of the dorsal V-band that is a result from a fall onto the hyperflexed, ulnar deviated hand. In contrast to this mechanism, most injuries occur as a result of a fall on the outstretched hand ( Figs. 14.1 and 14.2 ). So another more reasonable theory is a chisel action of either the dorsal proximal hamate and/or the ulnar styloid during hyperextension and ulnar deviation of the wrist. Radiographic studies define the so-called ulnar styloid process index, which means that a long ulnar styloid with positive or neutral ulnar variance is associated with an increased risk for an impaction injury. ,
A large MRI study revealed a high correlation between dorsal chip fractures and injuries to the dorsal carpal ligaments. This suggests a more complex trauma mechanism with a combination of avulsion and impaction.
The triquetral body fractures can be divided into sagittal, transverse, and comminuted ones. These injuries are often the result of high-energy traumas with a compression mechanism and are combined with other fractures or dislocations. They can be part of a perilunate/reverse-perilunate injury or axial instability pattern. So once a triquetral body fracture is diagnosed, other fractures, ligamentous injuries, and dislocations have to be ruled out.
Another subtype of the triquetral body fracture is the distal-ulnar osteochondral fracture with dislocation or instability at the piso-triquetral joint. Those injuries are a result of a direct blow to the pisiform with a shear force to the adjacent triquetral joint surface. , ,
The third triquetral fracture type is a volar avulsion fracture of the radiotriquetral, ulnotriquetral, or lunotriquetral ligaments ( Fig. 14.3 ).
Treatment options and aftercare.
Dorsal chip fractures ( Fig. 14.1 ) or isolated body fractures without any signs of carpal instability can be treated conservatively with 3 to 4 weeks of cast immobilization. Usually, there is tenderness over the fracture site for 6 to 8 weeks after trauma. Dorsal chip fragments with separation of more than 2 mm usually heal incompletely and lead to ossicle formation without impairment. ,
Large avulsion fractures and displaced body fractures with signs of carpal instability need to be stabilized by K-wires , and/or headless compression screws. , Arthroscopically assisted reduction has been described. Most fractures can be addressed directly via a dorsal approach between the fifth and the sixth extensor compartments. Palmarly located fractures are best addressed via an extended carpal tunnel approach ( Fig. 14.3 ). Rare cases of nonunion after triquetral body fractures are described and have been successfully managed by fragment excision. Distal-ulnar fragments with concomitant pisotriquetral instability are best treated with primary or delayed excision of the pisiform with fragment excision. ,
After open reduction and internal fixation, 4 to 6 weeks of cast immobilization is necessary. In those cases with an underlying carpal instability, immobilization should be extended to 8 weeks to allow adequate healing of the ligaments. In all cases of K-wire fixation, hardware removal should be performed before discontinuation of casting.
Pisiform fractures
Pisiform fractures are rare, and 50% occur in combination with other carpal fractures. The pisiform lies within the fibers or superficial to the terminal tendon of the flexor carpi ulnaris (FCU) muscle. As a sesamoid, it increases the lever arm of the FCU by moving the tendon away from the center of rotation of the wrist.
The bone is pea-shaped with a slightly concave articular surface on its the dorsal side where it articulates with the triquetrum. On its palmar side, the pisiform has attachments for the pisohamate, pisometacarpal, and pisotriquetral ligaments as well as the flexor and the extensor retinacula. It also serves as the origin of the abductor digiti minimi. Together, those structures make up the pisiform ligament complex, an important stabilizer to the ulnar column of the wrist.
The pisiform forms the ulnar border of the Guyon canal and lies in close proximity to the ulnar neurovascular bundle. , It has a rich vascular blood supply with three nutrient vessels entering the bone from proximally and distally. These vessels originate directly from the ulnar artery. The pisiform is the last carpal bone to ossify. This happens usually by the age of 12. Before this, there are multiple ossification centers that can masquerade fractures. Failed ossification can result in the development of an accessory ossicle, which is called the pisiform secundarium.
Diagnosis and classification.
Patients present with acute pain and swelling over the ulnar volar border of the wrist. There is point tenderness over the pisiform. Resisted ulnar deviation and flexion can be painful. Because of its proximity to the ulnar neurovascular bundle, nerve compression from fragments or hematoma is possible. Also, thrombosis or injury to the ulnar artery can be excluded either by the Allen test or Doppler sonography. ,
Besides standard plain x-rays, a clenched fist view in ulnar deviation, (semi-) supinated view in slight extension (Garraud’s view), or the reverse oblique view can be helpful. If there is any doubt about the correct diagnosis, cross-sectional imaging should be obtained.
Pisiform fractures can be either transverse or comminuted. Transverse fractures usually occur at the distal pole. They are classified as ligament avulsion type fractures at the attachments of the pisohamate and pisometacarpal ligaments. Those serve as an extension of the FCU tendon. The trauma mechanism is usually resisted, forced hyperextension of the wrist from a fall on the outstretched hand. Comminuted fractures ( Fig. 14.4 ) arise from a direct blow to the bone. Reported examples for this are the impact by a baseball or the recoil of a firearm. There are several case reports of fatigue fractures as a result of repetitive injuries (e.g., volleyball), which are thought to disrupt the vascular supply and cause microfractures.
Treatment options.
There are reports of successful conservative treatment of nondisplaced fractures.
Complications of malunion or nonunion can be ulnar nerve irritation, ulnar artery thrombosis, reduced grip strength, reduction of wrist motion, and pisotriquetral joint osteoarthritis. , ,
Surgical treatment consists mostly of fragment or complete pisiform excision ( Fig. 14.4 ). Occasional case reports suggest an open reduction and internal fixation with wires or screws. Since several studies showed no major impairment after pisiform excision, this is widely recommended for displaced, comminuted fractures. , In cases of ulnar nerve palsy, early surgical exploration with pisiform excision and ulnar nerve decompression have proven to be sufficient.
Pisiform excision is performed via a palmar approach on the radial edge of the flexor carpi ulnaris tendon to adequately expose and protect the ulnar neurovascular bundle. Because of the risk of damage to the dorsal cutaneous branch of the ulnar nerve and the ulnar neurovascular bundle, an ulnar approach cannot be recommended. The FCU tendon is split longitudinally, and the pisiform is excised. After excision, the tendon is closed with a running suture.
Aftercare.
Nondisplaced fractures can be treated with 4 to 6 weeks immobilization in a forearm cast. After fragment excision or total pisiform excision, usually immobilization for 2 weeks is adequate.
Trapezium fractures
Trapezium fractures occur mostly in combination with injuries to the adjacent carpals/metacarpals. Common additional fracture sites include the scaphoid, hamate, and the first metacarpal. , , Fifteen percent of all trapezium fractures are accompanied by a Bennett fracture. There are numerous case reports of fracture dislocations to the first carpometacarpal joint. ,
The trapezium has four surfaces that bear hyaline cartilage for articulation with the first and second metacarpal, the trapezoid, and the scaphoid. On the dorsal surface, there are two bony prominences, the dorsoulnar and dorsoradial tubercles. Analogous to this on the palmar surface is another protrusion, the trapezial ridge. This bony prominence serves as the attachment of the transverse carpal ligament, the abductor pollicis brevis muscle, the opponens pollicis muscle, and sometimes a tendon slip of the abductor pollicis longus muscle. In addition to this, the trapezium has ligament attachments for the stabilizing ligaments to the first carpometacarpal joint, namely the anterior oblique ligament, ulnar collateral ligament, posterior oblique ligament, and the dorsoradial ligament. The trapezium receives a generous blood supply via direct branches from the radial and the recurrent radial arteries. Nonunion and avascular necrosis are extremely rare.
Diagnosis and classification.
Clinical presentation of trapezium fractures is nonspecific. Symptoms include pain and tenderness over the base of the first metacarpal, the anatomical snuffbox, or the fracture itself along with reduced thumb motion. Marked opposition can be painful. In cases of a trapezial ridge fracture, resisted contraction of flexor pollicis longus can be painful as well.
Besides the standard radiographic views of the wrist, there are several special projections that help in the diagnosis of trapezial fractures. The Bett’s view is obtained with the hand in 20 to 30 degrees of pronation and the central beam about 15 degrees oblique from distal to proximal. This delivers a true lateral view of the first ray. Analogous to this is the Robert’s view where the fully pronated wrist with a 15 degree oblique central beam leads to a true anterior-posterior projection of the first ray. , Another helpful image, especially for fractures of the palmar, trapezial ridge is the carpal tunnel view. There are also reports of primary diagnosis of those fractures by use of ultrasound. In most cases, CT is necessary for correct assessment of the fracture.
Trapezium fractures can be divided into those of the body and those of the trapezial ridge. Fractures to the body were classified by Walker into five subtypes. Type 1 fractures are horizontal ones without involvement of the adjacent joints. Type 2a and 2b fractures are antero-lateral fractures in the sagittal plane with either involvement of the first carpometacarpal or scaphotrapezoideal joint. Type 3 fractures include the anteromedial trapezium. A type 4 fracture is a complete vertical fracture in the sagittal plane with involvement of the first carpometacarpal and scaphotrapezial joints. Type 5 injuries represent comminuted fractures. Combinations between vertical and comminuted fractures also occur. ,
Fractures of the trapezial body rarely occur via a direct blow to the bone itself. They are mostly high-energy traumas—for example, motorcycle accidents. , , , , Two different injury mechanisms are described.
The first trauma mechanism is an axial force through the first metacarpal in slight flexion onto the trapezium. This results in impact between the base of the first metacarpal and radial styloid leading to an avulsion of the anterior oblique ligament and a vertical fracture of the trapezium with or without concurrent additional fractures or fracture dislocation to the first CMC joint (CMC-1) joint. , , The second mechanism describes a commissural shearing by impact of an object to the first webspace (e.g., a motorcycle handlebar). The different fracture patterns are thought to vary with the impact angle. ,
The second fracture type are fractures to the palmar trapezial ridge. Those fractures represent extraarticular fractures. They were classified by Palmer into fractures of the base (type 1) and fractures of the tip (type 2).
The trauma mechanism is thought to be a fall on the outstretched hand, and the attachment of the transverse carpal ligament creates a traction force on the trapezial ridge. These injuries can occur in combination with fractures of the hook of hamate. ,
Treatment options.
For trapezial body fractures, complete excision has been recommended historically. This can still be considered for extreme comminuted fractures with underlying, severe osteoarthritis of the first carpometacarpal joint. In undisplaced fractures, conservative treatment with frequent radiographic controls is suitable. Immobilization in a cast including the CMC-1 and metacarpophalangeal (MP) joint of the thumb for 4 to 6 weeks is recommended.
Since inadequate treatment can result in chronic joint instability and arthritic changes, dislocation or a step-off of more than 2 mm represents an indication for surgery. ,
Treatment methods include open or closed reduction with K-wires or open reduction and osteosynthesis with headless compression screws or with screws and a plate , , ( Fig. 14.5 ). Because of the difficult intraoperative radiographic evaluation of reduction for severely displaced fractures, open approaches are more reliable. Arthroscopically assisted reduction has been described as well. For comminuted fractures, an additional indirect fixation via cross-pinning of the first and second metacarpals or application of an external fixator can be helpful. ,
