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Isolated carpal bone dislocations are uncommon injuries, however all the carpal bones have been reported to dislocate in an isolated fashion when a localized, direct, or indirect force is concentrated over a single bone of the wrist [1, 2]. The most common dislocation of carpal bone is that of the lunate which was examined in detail in the chapter on perilunate injuries. Less common is the dislocation of pairs of adjacent carpal bones which will be discussed in brief later on.

1 Scaphoid

Since the first description by Higgs in 1930 [3], only 32 [4] or 34 [5] cases of isolated scaphoid dislocation have been reported in the literature. The male to female ratio is approximately 7:1 [6, 7].

1.1 Evaluation

Wrist pain, swelling, and limitation of wrist motion are the usual complaints. A bony prominence is usually evident along the radial, palmar, or rarely dorsal aspect to the radius [6, 8]. Usually there are no signs of neurovascular involvement [6], but dislocations with palmar-ulnar direction could produce median nerve injury [9].

The percentage of cases with delayed diagnosis ranges between 48 and 50 % [6, 7]. Most of the delay in recognition is due to lack of awareness of this rare occurrence.

Simple radiographs are usually sufficient to make the diagnosis and are greatly facilitated by identifying the Gilula’s arcs. A CT scan may be helpful when in doubt, while arthroscopy may be used as both a diagnostic and a therapeutic modality if imaging modalities are nondiagnostic [10–12].

1.2 Classification

Dislocation of the scaphoid bone may occur after an apparently successful reduction of a major carpal dislocation or it may occur as a primary condition [13]. Richards et al. in 1993 [14] categorized scaphoid dislocations as simple (isolated to the scaphoid) or complex (a combination of scaphoid dislocation with axial carpal dislocation). Others, characterized these injuries as Type I (isolated anterolateral dislocation of the proximal pole); and Type II (scaphoid dislocation associated with an axial derangement of the capitate-hamate joint) [1, 2, 15, 16].

Leung et al. [7] have proposed a classification scheme for isolated dislocations of the scaphoid:

  1. 1.

    Primary versus secondary: The primary type results directly from the injury. The secondary type represents a residual dislocated scaphoid after closed [5, 17] or self-reduced perilunate dislocation.

  2. 2.

    Simple versus complex: The simple type only involves the scapholunate and radioscaphoid articulation, whereas disruptions of the distal carpal row including the capitate and hamate and middle/ring metacarpal articulations are classified as a complex type [11, 14, 18, 19].

  3. 3.

    Partial versus total: Partial dislocations retain some soft tissue attachments (usually distal), while complete dislocations have lost all soft tissue attachments.

  4. 4.

    Direction of dislocation: In partial dislocations, the proximal pole can be dislocated volarly (in ulnar, radial, or neutral direction), dorsally or purely radially.

A case of total dislocation in volar direction was reported by McNamara and Corley in 1992 [20], while one case of total dorsal dislocation of the scaphoid was reported by Amaravati et al. in 2009 [21].

Horton et al. [10] described a case of complex or type II dislocation and after reviewing the literature they found only 11 similar cases. Variants of a complex type of injury could be the combination of scaphoid dislocation with dislocation of the hamate [22] or with fracture of the hamate [23].

Lee et al. [5], after reviewing the literature, found 34 cases of isolated scaphoid dislocation. There were 26 palmar (14 in palmar-radial, 9 in neutral, 1 in proximal, and 2 in palmar-ulnar direction), 5 radial, and 3 dorsal dislocations.

Other carpal injuries that might be associated with scaphoid dislocation can be easily overlooked such as chip fractures of other carpal bones [21, 24–26].

1.3 Mechanism

The majority of cases result from traffic accidents especially motorcycle injuries, while the usual mechanism of injury is the application of an indirect force resulting in a dorsiflexion and ulnar deviation [8, 24, 27] or a twisting injury to the wrist [7]. Scarcer injury mechanisms reported are blast injuries [28], entrapment of the wrist [6] or following a penetrating injury with a sharp object [29]. In addition, the position of the wrist during injury, may be related to the direction of dislocation of the proximal pole of the scaphoid [7].

For type I injuries, a violent hyperpronation injury has been implicated with the wrist in dorsiflexion and ulnar deviation while grasping a fixed object, causing SL dissociation followed by the enucleation of the proximal pole of the scaphoid [1, 4, 15]. For type II injuries a high-energy axial compressive load along the 3rd and 4th metacarpals, creating enough shear stress to the capitate-hamate joint to disrupt its strong ligament attachments has been implicated [1]. Others have proposed that with hyperdorsiflexion, the proximal pole of the scaphoid slides down the volar slope of the radius and is ejected volarly. If the energy of injury is not dissipated, the capitate abuts the radial dorsal rim and the shearing force between the capitate and hamate is transmitted distally between the middle and ring metacarpals [16, 30].

Leung et al. [7] considered scaphoid dislocation as an extreme form of scapholunate dissociation representing one end of a spectrum of scapholunate injuries. Both are the result of a similar mechanism of injury and the only clinical difference between dorsal partial dislocation of the scaphoid and chronic scapholunate dissociation with DISI, is that the contact between the proximal pole of the scaphoid and the radius is lost in the former.

1.4 Pathoanatomy

The severity of the dislocation depends on the number of ligaments that have been disrupted. In partial palmar dislocation of the scaphoid, the SLI, RSL, and the RSC ligaments are disrupted while in total dislocation, all ligaments attached to the scaphoid are disrupted [7]. Szabo et al. [12], based on arthroscopic and surgical findings of 3 patients, postulated that the sequence of ligamentous failure in scaphoid dislocations begins in the radiopalmar aspect of the proximal pole of the scaphoid with the RSC and SLI ligaments failing first, followed by the LRL and ultimately by the ST ligament (Fig. 11.1a–n).

Fig. 11.1
figure 1figure 1

Male, 54-years old, car accident. A case of primary, simple, partial volar-radial scaphoid dislocation was recognized (a, b, c). The wrist was radially and volarly displaced. An accidental, unrelated cyst in the lunate was obvious (arrows) (a); and a concomitant fracture of the ulnovolar radial rim was indicated (arrows) (b); the volar approach revealed the dislocation of the proximal pole of the scaphoid in radiovolar direction and the ruptured volar RSC and LRL ligaments (asterisk) (RS radial styloid, Sc scaphoid) (d); arrows indicate the fractured ulnovolar fragment (e); dorsal approach revealed the attenuated dorsal intercarpal ligament which was detached from the dorsal scaphoid (asterisk), while the wrist was volarly displaced (R radius) (f); the dorsal approach also indicated the rupture of the SL ligament (line with arrows on each end) and the evacuated cyst of the lunate (arrow) (S scaphoid, L lunate, R radius) (g); a wire-loop was used to fixate the ulnovolar fragment (h); bone anchors were used for the reattachment of the SL ligament and the volar RC ligaments to the radius; the scaphoid was stabilized with K-wires to the lunate and capitate; cancellous bone grafts were placed to the lunate cyst. Postoperative X-rays (i, j). Two years later, the patient was pain free with good ROM, while the radiologic appearance was satisfactory (k, l); 7 years postoperatively, stenosis of the scaphocapitate joint was obvious, while the patient was complaining for weather-change symptoms (m, n)

Full size image

In complex or type II dislocations the ligamentous injuries are more extensive, including mainly the intercarpal capitohamate, the SLI, DRC, DIC, RSC, and LRL ligaments [10].

1.5 Treatment

Treatment ranges from closed reduction and casting, to percutaneous fixation after closed or open reduction and to open reduction and ligament reconstruction with internal fixation. Closed reduction is usually accomplished in most cases when treated acutely, by traction and direct manual pressure of the scaphoid with the wrist being ulnarly deviated. However, unsuccessful attempts for closed reduction have been reported, necessitating open reduction [4, 6, 7, 12, 26, 31]. In cases of incomplete reduction, ligamentous material (usually the SLI ligament) invaginated into the SL interval is blocking the reduction [12].

Case reports have described successful treatment with closed reduction and immobilization in a cast as definitive treatment, in cases of partial dislocation of the scaphoid detected early [18, 23, 24, 26, 27, 32, 33]. A scaphoid plaster is usually applied for 4–6 weeks. Closed reduction, percutaneous K-wires fixation, and cast application have also been reported, although these methods were not always successful [34]. However, many publications have advocated an open reduction, ligament repair, and internal fixation through a dorsal [1, 12, 26, 34–37] or volar approach [4, 6–9, 19, 20, 38]. In contrast to treatment for simple scaphoid dislocation, which is frequently treated with closed reduction, in cases with complex dislocations, reduction of the scaphoid alone is insufficient to stabilize the carpus with associated axial carpal disruption. Open reduction is necessary to fix the unstable radial half of the carpus to the stable ulnar half [11].

Most reported cases, have achieved good to excellent results [15]. The patients have returned to their prior activities with only moderate limitations, while there is a nearly universal loss of range of wrist motion [10].

The most significant risk factors in poor prognosis are delayed diagnosis and treatment, particularly if more than 2–3 weeks, although successfully treated delayed cases have recently been described [35]. Excision of scaphoid [37], proximal row carpectomy [13, 21], or partial wrist fusion [9] have been applied in cases of late diagnosis. The longer the delay, the worse the prognosis will be. Potential complications following an isolated scaphoid dislocation are residual carpal instability [19, 20, 31], stiffness and posttraumatic arthrosis.

Although transient radiological features of early avascular necrosis have occurred, in none of the cases reported has there been any evidence of permanent avascular necrosis [1, 7, 10, 24]. In partial dislocations, vascularity of the scaphoid is partly maintained by intact distal soft tissue attachments, while in cases of complete dislocation it is proposed that there are intact intraosseous channels inside the intact scaphoid bone that allow rapid revascularization from the surrounding soft tissues [ 7]. However, Szabo et al. [12] reported that one out of three of their patients showed avascular necrosis with fragmentation of the proximal pole of the scaphoid after 20 months follow-up.

2 Triquetrum

Dislocation of the triquetrum has rarely been described in the context of perilunar injuries [39, 40]. These cases probably constitute a variant of reverse perilunar instability, where the force is applied to the hypothenar area and the disruption propagates around the triquetrum disrupting the ligaments from its distal (triquetrohamate), proximal (ulnotriquetral) and radial (lunotriquetral) articulation.

Both dorsal [40–43] and volar dislocations [44, 45] of the triquetrum have been documented. With so few cases, the exact mechanism of injury remains obscure. Usually, a major fall, a motor vehicle accident, or a crush injury has been implicated. During the frequently mentioned mechanism, with a fall on the outstretched hand and the wrist in dorsiflexion and ulnar deviation, the triquetrum is thought to become covered by the lower end of the ulna, avoiding dorsal displacement and favoring volar dislocation [42]. In addition, with forced wrist hyperextension, the proximal pole of the hamate rides dorsally on the triquetrum, exerting a palmar force leading to a palmar dislocation of the triquetrum [45]. However, the higher frequency of dorsal dislocations makes more likely the mechanism of injury to be the direct impact to the hypothenar area. Dorsal dislocation may also be produced by wrist hyperflexion and pronation [43], secondary to a perilunar dislocation or a variant of an ulnar axial loading injury [40].

In many of the reported cases the diagnosis was delayed [41, 44, 45]. On examination, swelling will be noted about the ulnar aspect of the wrist and if the dislocation is dorsal, it may be possible to palpate the displaced triquetrum. The volar displacement is associated with transient median nerve compression [15, 44, 45]. Usually, PA lateral and oblique views are adequate for radiographic evaluation, with the lateral view providing information on the direction of the dislocation.

Treatment has included triquetrum excision [44, 45], open reduction and internal fixation [40, 41, 43], and closed reduction without fixation [42], all with reasonably good clinical results, although in two cases signs of instability (VISI [43] and ulnar translation [45]) were found. In any case, excision of the triquetrum must be avoided, since significant stabilizing ligaments are attached to the bone, which in addition, has an important proprioceptive role. Although closed reduction and percutaneous pinning could be attempted, we believe that open reduction is required. The approach is dictated by the direction of dislocation, although combined palmar and dorsal approaches may be necessary, followed by K-wire fixation of the reduced triquetrum with ligament repair. There have been no reported cases of avascular necrosis following treatment for a triquetral dislocation [28].

3 Pisiform

Pisiform dislocation is an extremely rare injury and has been reported in isolation [46, 47], in combination with distal radial fractures [48, 49] or with hamate dislocation [50–52]. The possible relationship between pisiform subluxation and distal radius fractures has also been mentioned [53]. In children, two cases of pisiform dislocation associated with a distal radius fracture have been reported [48, 54]. Displacement of the pisiform has been reported distally, ulnarly, and proximally [15, 36, 55].

Since the pisiform has a flat articular surface articulating with the triquetrum, it relies mainly on its many soft tissue attachments for stability. These include: the attachment of flexor carpi ulnaris tendon, abductor digiti minimi, extensor retinaculum, transverse carpal ligament, pisometacarpal and pisohamate ligaments, and the joint capsule to the triquetrum (Fig. 11.2). Mechanical testing has showed the soft tissues around the pisotriquetral joint to be strongest proximally and distally and weakest medially [56]. The ulnar nerve and the volar branch of the ulnar artery are located in the immediate vicinity to the pisiform with the nerve being medial to the artery and closer to the pisiform.

Fig. 11.2
figure 2

The soft tissues stabilizing the pisiform to the flat articular surface of the triquetrum (asterisks pisohamate and pisometacarpal ligaments, FCU flexor carpi ulnaris)

Full size image

Two possible mechanisms have been postulated [15, 28, 46, 54]. One is a direct blow to the ulnar aspect of the wrist and the other is strong eccentric contraction on the flexor carpi ulnaris with the wrist in extension. Fall from height, traffic accidents, and lifting heavy objects have been implicated. Pulling of the FCU, as well as forced wrist hyperextension can disrupt the thin capsule of the pisotriquetral joint, and the FCU tendon’s distal continuation or the pisohamate and pisometacarpal ligaments. If these ligaments are damaged, the function of the FCU becomes impaired, with the pisiform retracting proximally [57].

The diagnosis should be based on the injury mechanism and the presentation of pain, swelling, and tenderness over the ulnar border of the wrist, while a painful restriction of all wrist movements is a usual finding. Frequently a characteristic depression is found at the base of the hypothenar eminence, where the pisiform bone should lie [46, 55]. Ulnar neuropathy may also be caused by pisotriquetral joint instability [55, 56].

Posteroanterior, lateral, and oblique radiographs are usually adequate for diagnosis. X-ray features of the pisotriquetral joint including parallelism, width of the joint space and symmetry have been suggested to be diagnostically relevant [53]. Oblique view is taken with the ulnar side of the wrist placed against the plate, with the forearm in about 15o of supination. Comparison films with the contralateral wrist may be needed.

Treatment includes immobilization after a closed reduction [48, 55, 58], open reduction with internal fixation, closed reduction and pinning [59], and resection of the pisiform either initially [46, 57, 60–63] or secondarily in cases of persistent pain or recurrent dislocation [47].

The manipulation for closed reduction usually requires maximum wrist flexion with direct pressure to relocate the bone [28, 58]. The reduction can be aided by placing the forearm in pronation [55]. There are some differences in opinion regarding the position of the wrist immobilization. The following variants have been proposed: a below elbow cast with the wrist in 30–40o of dorsiflexion and slight radial deviation for 3–4 weeks [58], a radially deviated short arm cast for a minimum of 3 weeks [46], a dorsal splint holding the wrist flexed and the forearm pronated for 3 weeks [55] or a long arm plaster splint in 25o of dorsiflexion for 3 weeks [59].

It has been stated [64] that excision of the pisiform decreases wrist flexion strength without functional deficit or loss of range of motion and that the soft tissue’s confluence over the pisiform allows for subperiosteal pisiform excision and repair of the tissues without disturbing the FCU insertion. Excision of the pisiform is consistently the most successful treatment for pain without functional deficit [47, 65, 66].

4 Trapezium

The trapezium may dislocate in isolation or together with the thumb metacarpal. Incomplete dislocation, in which the trapezium remains attached to the base of the first metacarpal should be categorized as a peritrapezium axial-radial dislocation [1]. True volar isolated dislocations of the trapezium are very rare and are thought to be caused by a direct blow to the dorsolateral aspect of the wrist or as a consequence of a hyperextension-supination injury to the radial-deviated wrist [1, 15]. Dorsal radial dislocations are described as the result of hyperflexion of the first metacarpal combined with an axial compression force [67, 68]. Crush injuries and motor vehicle accidents are the most commonly reported causes of these injuries.

Palmar and dorsal radial dislocations have been described [68–71]. However, Garcia-Elias [72] after reviewing the literature, found that only six cases have been reported of true isolated dislocations with complete enucleation of the bone and were all palmarly displaced.

Clinically, depending on the mechanism an open wound may be present at the thenar area [73–75]. With isolated dislocation, a palpable mass may be present at the base of the thumb. Pain, instability, and limited range of motion of the first CMC joint may be noted [28]. Palmar dislocation of the trapezium has been associated with avulsion of the recurrent motor branch of the median nerve [75]. Diagnosis is best confirmed by radiographs, while the posteroanterior axial oblique view is used to evaluate the trapezium with the surrounding bones [76].

In acute cases, open reduction and K-wire fixation are thought to be the treatment of choice [68, 69, 74, 75, 77] and whenever possible, repair of the periarticular ligamentous structures should be accomplished [28]. Closed reduction and percutaneous pinning could also be attempted or in cases of delayed diagnosis, excision of the trapezium has been applied [70, 78].

Since the trapezium receives its blood supply from nutrient arteries entering the bone from three surfaces and has consistent intraosseous anastomoses, the risk of avascular necrosis is negligible.

5 Trapezoid

The trapezoid has been described as the keystone of the proximal carpal arch with its palmar surface narrower than the dorsal, while it is attached to the surrounding bones by strong ligaments. It has been stated [36, 79] that Gay in 1869 was the first to describe a case of trapezoid dislocation and since that time there have been 25 [79] or 26 [36] reported cases in the literature, while a literature review by De Tullio [80] revealed only 24 published cases since 1962. Frequently, the dislocation of the trapezoid is associated with other fractures or dislocations of the hand or constitutes a part of the axial-radial dislocations of the wrist [81]. Both palmar [80, 82, 83] and dorsal [84–86] isolated dislocations of the trapezoid have been reported. Less than 10 of these dislocations were displaced volarly with one having caused an attritional rupture of flexor tendons in a case whose diagnosis was missed for 4 months [82] and another presented with acute carpal tunnel syndrome [79].

There is no clear explanation as to how a wedge-shaped bone which is wider dorsally, dislocates palmarly, but a direct blow to the dorsum of the wrist has been implicated [1]. The more common dorsal dislocations may be produced by direct trauma or indirectly from a blow to the second metacarpal with the wrist flexed [28].

In acute cases, pain, considerable swelling, and limited motion of the fingers are noticed, while vascular or neurological damage has not been reported. With dorsal dislocation an osseous prominence is palpated at the base of the index finger metacarpal, while a palmar dislocation will not have such an obvious presentation [28]. Diagnosis of trapezoid dislocation is confirmed by standard posteroanterior, lateral, and oblique radiographs looking for an empty space at the base of the second metacarpal. When necessary, tomograms or a CT scan may be necessary.

Treatment for dorsal dislocation of the trapezoid has included closed reduction [87, 88] or open reduction with a dorsal approach [84, 86] and pinning with K-wires.

Closed reduction of a palmar dislocation is ineffective because of the shape of the trapezoid [82, 83], thus open reduction is always necessary with combined [79] or with only dorsal approach [80, 83]. Few cases were treated with excision of the trapezoid [81, 82], which resulted in the proximal migration of the second MC and the development of degenerative changes to the midcarpal joint. A reasonable alternative in difficult cases is a primary limited fusion [82, 89]. The trapezoid has nutrient vessels that enter its palmar and dorsal surfaces, while there are no intraosseous anastomoses between the palmar and dorsal systems. Thus, the trapezoid is at risk in cases of dislocation and cases with findings of avascular necrosis have been reported [15, 82, 86].

6 Capitate

True isolated dislocation of the capitate is an extremely rare injury. It requires disruption of the interosseous ligaments to the adjacent trapezoid and hamate, disruption of the ligaments of the third CMC joint distally, and disruption of the radiocapitate and capitotriquetral ligaments proximally [28]. To our knowledge, only one such case has been reported by Cherucci et al. [90], who described a total volar dislocation of the capitate after a crush injury of the hand in a metal press. In the majority of the reported cases, the dislocated capitate is associated with other carpal injuries. Most commonly the capitate dislocates in a volar direction [90–94] and in one case only it dislocated in dorsal direction [95].

Lowrey et al. [93] reported a case of volar capitate dislocation associated with other multiple carpal injuries. Hirata et al. [91] described a case with dorsal dislocation of the third CMC joint, associated with volar rotational subluxation of the capitate from its distal (CMC), and proximal (LC) articulation. This case constitutes a combination of types IIa and IIId injuries, according to Garcia-Elias’s classification for CMC injuries. Walker and Pradhan [95] described a case with dorsal dislocation of the capitate and the third metacarpal. This case could be a type IIId injury according to previous classification for CMC injuries. Ruijters and Kortmann [94] reported a volar dislocation of the capitate associated with a fracture of the lunate in the coronal plane, constituting a case of volar perilunate injury. Lee et al. [92] described a case of volar dislocation of the capitate associated with dislocation of the ulnar side of the carpometacarpal joint.

Dislocation of the capitate usually resulted after a crush injury [90, 91] or a motorcycle accident [93, 95]. Clinical findings are dependent on the mechanism of injury while the diagnosis is sometimes difficult to establish using standard radiographs. In the case presented by Checcucci et al. [20], a definitive diagnosis was obtained only after a CT scan.

The majority of cases presented in the literature were treated with open reduction and fixation with K-wires, except for the case presented by Walker and Pradhan [95], which was reduced with closed manipulation under general anesthesia and immobilization in a below elbow cast for 8 weeks. Short-term results were generally good but early development of degenerative changes [93] or instability findings [91] have been reported.

7 Hamate

Isolated dislocation of the hamate bone is an extremely rare injury, with only eight cases reported in the literature since the first description by Buchanan in 1882 [96]. Most cases of hamate dislocation have been described as part of more complex injuries or in association with other carpal bones’ dislocation [22, 50, 97] or constituting cases of axial-ulnar derangements, with the hamate being displaced along with the 4th and 5th metacarpals [98] (Fig. 11.3a–i). Dislocation of the hamate requires disruption of the triquetrohamate ligament, pisohamate ligament, and capitohamate interosseous ligament as well as disruption of the 4th and 5th CMC joints.

Fig. 11.3
figure 3

Male, 62-years old, car accident. The wrist injury remained initially undiagnosed and was treated with a below elbow splint. Routine examination of the X-rays 10 days later revealed a dorsal dislocation of the hamate, associated with proximal migration of the 5th metacarpal (a, b); a CT scan indicated the dorsal dislocation of the main portion of the hamate (asterisk) with a fractured hamulus (arrow) (c); a painful osseous swelling of the dorsum of the wrist was apparent (arrow) (d); during exploration the main portion of the hamate was found beneath the subcutaneous tissue, devoid of any soft tissue attachments (e); postoperative X-rays (f, g); radiographic appearance 3 months later (h, i)

Full size image

Both volar [96, 99, 100] and dorsal [101, 102] dislocations of the hamate have been reported. The usual mechanism of injury is a direct impact by a sharp tool or indirect trauma by hyperextension [15, 28, 36].

On physical examination, there is painful palmar or dorsal swelling on the ulnar aspect of the wrist, with or without a palpable bony prominence. Nerve damage does not seem to be common, however, given that the ulnar neurovascular bundle is in close proximity, injury to this structure might be anticipated [28, 101].

Diagnosis is usually made by conventional X-ray examination. Posteroanterior (PA) and lateral neutral rotation views of the wrist are adequate for diagnosis. In the PA view, most noticeable is a gap distal to the triquetrum, while the lateral view reveals the direction of the dislocation. A CT scan is usually necessary to unveil the true extent of the damage e.g., fracture of the hook of the hamate [96]. Since 50 % of hamates lack an intraosseous anastomosis of its nutrient vessels, the risk of avascular necrosis is a possible complication, although it has not been reported so far.

Treatment alternatives include: closed reduction [99, 102], closed reduction and percutaneous fixation [98], open reduction with [96, 100] or without internal fixation [101] and excision [103, 104]. The small number of cases reported does not allow inferences about the best treatment. However, closed reduction (when feasible) with percutaneous pinning under image intensifier, open reduction with the approach depending on the direction of the dislocation, and pinning of the hamate to the metacarpals, the capitate and triquetrum, seem to be the indicated methods of treatment.

8 Pairs of Dislocated Wrist Bones

Carpal dislocation may occur in units of adjacent bones. These unusual patterns of dislocation are most likely the result of direct trauma [28]. When adjacent bones of the proximal carpal row are dislocated, they probably constitute variants of perilunate dislocations or reverse perilunate dislocations. On the contrary, when adjacent bones of the distal carpal row are dislocated, they possibly represent cases of axial dislocations. The most common pattern is combined dislocation of scaphoid and lunate. Other reported patterns of adjacent bone dislocations are: triquetrum and lunate [39], hamate and pisiform [50–52], capitate and hamate [97], trapezium and trapezoid [105], trapezoid and capitate [106]. A case of dislocation of non-adjacent carpal bones (scaphoid and hamate) has been reported by Sakada et al. [22]. Extremely rare are cases of three carpal bone dislocations, such as: trapezium, capitate and hamate [107] or lunate, triquetrum and hamate [108].

Scaphoid and lunate: Domeshek et al. [109] in a review of the literature found only 17 reported cases that involved simultaneous dislocation of the scaphoid and lunate. In 11 of these cases, the two carpal bones dislocated as a unit, while in 6 cases the dislocation was of divergent type. All reported cases had dislocated in a palmar direction, sometimes producing symptoms from the median nerve [110–112]. Most of the cases resulted from high-energy injuries (fall from height or motor vehicle accident) and the mechanism of injury is thought to be extreme dorsiflexion with ulnar deviation [109, 111, 113, 114]. A direct blow to the dorsum of the wrist has also been reported [115]. Various treatment methods have been applied: closed reduction and casting [116], closed reduction and percutaneous pinning [115], open reduction and cast immobilization, open reduction, ligamentous repair and percutaneous pinning [110, 111, 117]. Late wrist malalignment [116, 118–120] and avascular necrosis [112, 120] are the main concerns of these injuries. The recommended treatment is open reduction with combined approach, repair of the volar LT ligament and the SLI ligament (in divergent type of dislocation), and stabilization with K-wires of the scapholunate, scaphocapitate and lunotriquetral joints.