An Atypical Dorsal Perilunate Dislocation with No Scapho-Lunate Ligament Injury in Bilateral Complex Wrist Injury – a Case Report

Introduction

Perilunate dislocation and wrist fracture-dislocation are rare and occur most frequently in young patients who sustain high-energy trauma [1], including motor vehicle accidents, falls from a height or contact sporting activities [2]. They are severe injuries involving approximately 7% of all injuries of the carpus [3] that are often missed on initial evaluation in up to 25% of cases [1,2] owing to inexperience personnel interpreting the standard radiographs or because the patient may have multiple injuries, which may lead to inadequate imaging of the upper extremity.

Rarely these injuries occur bilaterally and simultaneously in the same patient [4,5].

We report a case of an atypical dorsal perilunate dislocation with no scapholunate (SL) ligament injury with an associated contralateral radiocarpal fracture-dislocation.

Description of the case

A 17-year-old right-handed male was referred to the Emergency room of our Hospital 12 hours after a high-energy trauma to both wrists after a fall from a height with facial disfigurement and a bilateral swelling of the wrists with complete joints dislocation. On the right side the multiple plain X-rays and computed tomography (CT) showed an atypical dorsal dislocation of the carpus with a dislocated radial styloid process fracture (Figure 1a–c). On the left side the X-rays and computed tomography showed an ulnar translation of the carpus associated to a dorsal perilunate dislocation with no SL ligament diastasis (Figure 1d– g). On the right side through a radial approach an open reduction and internal fixation with a 2.4 mm cannulated screw (Synthes Ltd, Zuchwil, Switzerland) and a single K-wire was undertaken (Figure 2a,b) and a repair of the volar radiocarpal ligaments with 2/0 polypropylene sutures (Prolene^®, Ethicon, Sommerville, NJ, USA) through a volar approach was performed (Figure 3a,b). On the left side the normal anatomy of the first carpal row through a volar approach was restored and the volar capsular ligaments were repaired (Figure 4a,b). While an assistant held the lunate and scaphoid in the reduced position relative to the radius, a 1.25 mm oblique pin from the radial metaphysis was temporarily inserted across the radiolunate (RL) joint. The lunotriquetral (LT) ligament and dorsal intercarpal (DIC) ligament were repaired by the use of bone anchors (Minilok Quick Ancor Plus [2-0] Suture; DePuy Mitek, Oberdorf, Switzerland) through a dorsal approach and through a radial approach the radioscaphocapitate (RSC) and scaphotrapeziotrapezoid (STT) ligament were reconstructed with 2/0 polypropylene sutures (Prolene^®, Ethicon, Sommerville, NJ, USA) and a temporary fixation of the radioscaphoid (RS) and lunotriquetral (LT) joints were performed with 1.25 mm K-wires (Figure 5a,b).

The two wrists were immobilized in a short arm thumb spica for 6 weeks on the right side and for 8 weeks on the left side. Then K-wires were removed and progressive and daily occupational therapy sessions were started till restoration of maximum active (AROM) and passive (PROM) range of motion. At 12-month follow-up (Figure 6a,b) in spite of an ulnar translation of the carpus at standard radiographs on the left side with no signs of secondary dislocation or ostheoarthritis, the patient is pain-free. He shows an excellent AROM on the right side of 60° of palmar flexion, 70° of dorsiflexion, full supination and pronation while on the left side of 40° of palmar flexion, 40° of dorsiflexion, full supination and pronation (Figure 7a,b). The grip strength measured with the Jamar dynamometer (J.A. Preston, Jackson, Michigan, USA) on the right hand is 50 kg while on the left side is 45.8 kg (normal range scores in a male of comparable age are 40–68 kg) [6]. In spite of the reduction of wrist PROM and AROM the patient reports a complete recovery of activities of daily living and sports.

The patient was informed that data from the case would be submitted for publication, and gave his consent.

Discussion

Radiocarpal fracture-dislocation is a rare injury, often associated with postoperative pain, stiffness, instability and post-traumatic arthritis [7]. Perilunate injuries, in particular, are the results of high-energy trauma to the wrist, and are frequently associated with other fractures and ligamentous injuries. Most dorsal perilunate dislocation are the result of an extreme extension of the wrist, associated with midcarpal supination and ulnar translation, often secondary to severe trauma as fall from a height or motorcycle accident [1].

The high energy force can disrupt extrinsic and intrinsic ligaments (scapholunate, lunotriquetral, radioscaphocapitate), bones (radial styloid, scaphoid, capitate, lunate) or combination of bones and ligaments [3].

The diagnosis is based on clinical examination and standard radiographs. CT scan must be performed if there is any doubt, in order to avoid a delay in diag- nosis, with a precise planning of the procedure, avoiding intraoperative discovery of a fracture or carpal misalignment, defining the type of fracture and revealing any associated ligamentous injuries [8].

Because of their rarity and difficulties of interpretation on standard radiographs by less experienced radiologists or surgeons, up to 25% [1] of perilunate dislocation are often overlooked or misdiagnosed on first assessment.

Treatment options for perilunate instability patterns include closed reduction and cast immobilization, closed reduction and percutaneous pinning and open reduction. As the awareness of the anatomy and biomechanics of these injury patterns has evolved, apart from bone fixation, surgeons have tended toward treatment approaches that attempt to restore the normal anatomy and repair the injured extrinsic and intrinsic carpal ligaments, through open techniques [1,3].

The anatomic relationship between radius, the first carpal row and the capitate has to be restored in association with soft tissue repair on the volar and dorsal side of the wrist to prevent ulnar translation and secondary osteoarthritis.

On the right side, we performed an anatomical reduction of radial styloid and repair of the volar radiocarpal joint capsule. Unlike previous reports [2] we confirm that volar radiocarpal ligaments repair (mainly the radioscaphocapitate ligament) should be recommended to prevent carpal misalignment [3].

On the left side we faced an atypical dorsal perilunate dislocation with no scapholunate ligament tear. According to Mayfield [9] most carpal dislocations around the lunate are due to a violent extension, ulnar deviation and supination injury to the wrist initiating at the level of the body of the scaphoid (producing a trans-scaphoid fracture) or through the scapholunate joint, with the palmar scapholunate ligament failing first, with a tear beginning from palmar to dorsal of the proximal membrane and the thicker dorsal scapholunate ligament (stage 1). After disruption of the scapholunate joint, if wrist hyperextension continues, the distal row (mainly the capitate) translates dorsally and dislocates relative to the lunate (stage 2). As the capitate displaces dorsally, the triquetrum–capitate ligaments pull the triquetrum out of its normal position, resulting in a progressive tear of the lunotriquetral interosseous ligament and lunotriquetral ligaments (stage 3). When all perilunate ligaments are torn, the dorsally displaced capitate may exert a palmar translation force to the dorsum of the lunate, resulting in a palmar lunate extrusion into the carpal tunnel (stage 4).

In order to explain why some patients have an isolated lunotriquetral dissociation without scapholunate damage, some authors hypothesised the existence of a reverse or ulnar-sided perilunate pattern of destabilization [10]. According to their studies, if the extended wrist hits the ground on the hypothenar eminence, a violent twisting of the distal carpal row into hyperextension, carpal pronation and radial deviation may follow. Therefore, a particular pattern of ligament disruption, starting at the lunotriquetral joint (stage 1), followed by complete dorsal dislocation of the capitate (stage 2) and disruption of the scapholunate joint (stage 3) may appear. Probably, our patient started such a reverse pattern of destabilization but, for unknown reasons, the traumatizing energy was not spent damaging the scapholunate joint but twisting and disrupting the ligaments between the scaphoid and the distal carpal row, i.e palmarly the radioscaphocapitate, the deeper scaphocapitate, radioscaphoid and dorsolateral scaphotrapezial and dorsally the dorsal intercarpal ligament. Like in a previous report [11] due to the lack of a complete scapholunate dissociation, the case cannot be categorized as a pure reverse perilunate dislocation but as a combined atypical reverse perilunate and axial–ulnar pattern of wrist disruption.

Conclusion

Despite the rarity of the condition, the general principles of management of wrist dislocations are always to be applied. The alternative of combining a palmar and dorsal approach not only for the lunate reduction but also for an anatomic ligament reconstruction on “both” sides is mandatory. In our patient this led to excellent functional results, in spite of mild ulnar translation with no major complications.

Role of authors: All authors have been actively involved in the planning, preparation, analysis and interpretation of the findings, enactment and processing of the article with the same contribution.

Conflict of interest: None.

Disclosure: This research required no approval by the local Institutional Review Board of the authors’ affiliated institutions where the clinical and radiological evaluations were performed but the patient gave his consent to publication of pictures and diagnostic studies for scientific purpose. We declare that this study has received no financial support. All procedures performed in this study involving human participants were in accordance with the Helsinki declaration and its later amendments or comparable ethical standards.

Stefano Lucchina, MD

Locarno Hand Center, Via Ramogna 16

6600 Locarno, Switzerland

e-mail: info@drlucchina.com

Submitted: 30. 09. 2020

Accepted: 23. 12. 2020