Simultaneous palmar divergent dislocation of scaphoid and lunate concurrent with i psilateral humeroradial joint dislocation and humerus shaft fracture: report a rare case and add a new subtype

Background: Simultaneous palmar dislocation of scaphoid and lunate is a rare condition generally resulting from high-energy trauma and usually classified into two types. The literature has only reported nine patients with palmar divergent dislocation of scaphoid and lunate. Here we we present a case of accompanied ipsilateral humeroradial joint dislocation and open humeral shaft fracture caused by the same violence travelling from the wrist. Considering the emerging cases with their own characteristics, we suggest this severer injury be expanded into the third type of palmar dislocation of scaphoid and lunate. Case presentation: A 31-year-old male who fell from a three-storey building, with his right wrist directly hitting the ground, was admitted to the orthopaedic department of our hospital. Physical and radiographic examinations defined simultaneous palmar divergent dislocations of scaphoid and lunate concurrent with ipsilateral humeroradial joint dislocation and open humeral shaft fracture. After debridement and internal fixation for humerus and close reduction for humeroradial joint, the scaphoid and lunate were treated with open reduction and fixation by Kirschner’s wires, and the palmar scapholunate ligament and anterior capsule were repaired through volar approach. After a 3-year follow-up, his humeral fracture healed without recurrent dislocations, collapse or avascular necrosis of scapholunate. Favorable hand function regained . Conclusions: Palmar divergent dislocation of scaphoid and lunate caused by considerable violence is rare and appropriate to urgent open reduction and fixation with Kirschner’s wires and repair of the stronger palmar scapholunate ligament through single volar approach. When the residual violence continues to transmit to the upper extremity, ipsilateral dislocation or fracture may occur. We advise that this

Kirschner's wires and repair of the stronger palmar scapholunate ligament through single volar approach. When the residual violence continues to transmit to the upper extremity, ipsilateral dislocation or fracture may occur. We advise that this 3 complex injury be classified into a third subtype of simultaneous palmar dislocation of scaphoid and lunate to avoid misdiagnosis.
Additionally, Magnetic resonance imaging (MRI) found no evidence of avascular necrosis of the scapholunate and the normal scapholunate interosseous distance (Fig. 3C). The right wrist retained nearly all its original functions. Range of motion: palmar flexion of 37° (a 82% recovery according to that of the contralateral side, 45°), dorsiflexion of 80°(equivalent to that of the contralateral side), ulnar deviation of 32°(a 91% recovery according to that of the contralateral side, 35°), and radial deviation of 28° (a 88% recovery according to that of the contralateral side, 32°).
The grip strength of his injured hand (dominant) was comparable to his contralateral hand (Fig. 3D).

Discussion and conclusions
As the patient fell to the ground on his right wrist, his hand outstretched and interosseous ligaments broke, resulting in the divergent dislocation of the scaphoid and the lunate. Not only that, the residual force travelled from the wrist to the upper part, leading to homolateral humeroradial joint dislocation and humeral fracture. Prior to this case report, one case with ipsilateral radial head fracture [1] and trapezium fracture was also described [4]. This type of injuries could be absorbed into a third subtype of palmar dislocation of scaphoid and lunate, just as Maisonneuve fracture of high fibular in Lauger-hansen classification of ankle fracture-dislocation [10]. With this new classification system, injury severity can be more accurately evaluated and coexisting injures can not be misdiagnosed.
The optimal treatment of palmar dislocation of scaphoid and lunate remains unclear. In this case, we first fixed humeral shaft fracture and then reduced the dislocation, an effort that could prevent radial nerve from iatrogenic damage. Only one previous case had demonstrated postoperative avascular necrosis of lunate due to delayed diagnosis (33 days after injury) [3], and another treated with a proximal 6 row carpectomy (PRC) (Table 1) [6]. Although PRC may eliminate avascular necrosis and avoid additional surgery, postoperative range of motion and grip strength just reach 50 70% and 60 90% of that of the healthy-side, respectively [11]. Therefore, except for special patients needing PCR, we recommend surgical repair as the first choice, especially for young people and manual workers [7].
Anatomic reduction can protect the scapholunate from further avascular damage and accelerate spontaneous revascularization [1][2][3][4][6][7][8][9]. Closed reduction is technically difficult and cannot repair carpal interosseous ligaments. Moreover, repeated close reduction can damage the remaining soft tissue attachments of the scapholunate, which may contain important vessels needed to maintain blood supply to scaphoid and lunate [3,9]. Meanwhile, just a plaster cast is not enough to fix the scaphoid and lunate due to the ruptured interosseous ligaments and severe carpal instability [3,4,7,8]. As reported by Komura [7] and Idrissi [8], after closed reduction, palmar divergent dislocation of scaphoid and lunate still needed to be refixed because of its severe carpal instability. Furthermore, in our case, open reduction and fixation with Kirschner's wires also gained a favorable outcome.
Of previous reports, one case showed postoperative complication with flexion deformity of the scaphoid and a break in arc II of Gilula's line [7], one with avascular necrosis of the lunate [3], and another with scaphoid absorbed and cartilage height decreased and subchondral sclerosis and posttraumatic arthrosis [9]. These complications might be caused by additional dorsal incision and poor blood supply to scapholunate or no suturing in the stronger palmar scapholunate ligament [12]. In our case, with the palmar scapholunate ligament repaired through a single volar approach, the patient developed no avascular necrosis of carpal bones, indicating that the blood supply of scapholunate from surrounding soft tissue 7 was rich enough for revascularization of scapholunate. Open reduction and ligament repair through only one palmar incision have more advantages: less invasive, smoother operation and maintenance of blood supply from soft tissues. Repairing the torn ligaments with a suture anchor can make operation simplify and offer nonspace-consuming, dynamic, and permanent fixation, it has already been reported [7,13].
In conclusion, we first reported a rare case of simultaneous palmar dislocation of

Consent for publication
Written informed consent was obtained from the patient for publication of this Case report and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.      The wrist radiographs, MR image and function display at the final follow-up. A, B A normal ca