Practice Easily Missed?

Perilunate dislocation

BMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e7026 (Published 06 November 2012) Cite this as: BMJ 2012;345:e7026
  1. Annakan V Navaratnam, foundation year 2 doctor,
  2. Simon Ball, hand surgery fellow,
  3. Claire Emerson, emergency medicine consultant,
  4. Rupert Eckersley, consultant hand surgeon
  1. 1Chelsea and Westminster Hospital, London SW10 9NH, UK
  1. Correspondence to: A V Navaratnam annakan.navaratnam04{at}imperial.ac.uk
  • Accepted 8 October 2012

A 30 year old, right hand dominant mechanic presented to the emergency department with a swollen, painful right wrist after he fell on to an outstretched right hand from a motorcycle travelling at high speed. Radiographs were interpreted as normal and the patient was discharged with a diagnosis of a wrist sprain. The next morning he presented again to the same emergency department with a new symptom: numbness of the right thumb and index, middle, and ring fingers. The radiographs were reviewed and a perilunate dislocation with median nerve compression was diagnosed. That afternoon the patient had median nerve decompression and open reduction and stabilisation of the perilunate dislocation with ligament repair.

What are perilunate and lunate dislocations?

Perilunate dislocations usually result from high energy hyperextension injuries to the wrist. In perilunate dislocations, the capitate and other carpal bones are displaced dorsal to the lunate, which remains located in the lunate fossa of the distal radius (fig 1). Lunate dislocation is the final stage in the continuum of perilunate dislocation and refers to the volar displacement of lunate from the lunate fossa of the distal radius.1

Figure1

Fig 1 Left: Anteroposterior diagram of the right wrist and median nerve. Right: Cross section of the right wrist showing the relation of the carpal bones and median nerve. In the wrist the median nerve passes through the carpal tunnel along with nine flexor tendons. The carpal tunnel is situated volar to the lunate and scaphoid. Owing to its close proximity to the median nerve, displacement of the lunate in a perilunate dislocation can exert pressure on the median nerve that may result in nerve injury

How common is perilunate dislocation?

  • Perilunate dislocation is a rare presentation

  • Associated with scaphoid fractures in 61% of cases1

Why is perilunate dislocation missed?

A case series on the management of neglected perilunate dislocation described 10 cases managed in a single centre that were missed on initial presentation.2 Additionally, several recent cases of misdiagnosis of perilunate dislocation have been reported,3 4 5 highlighting the fact that this diagnosis is still being missed. Owing to the rarity of perilunate dislocation, the radiological signs are often not recognised by primary care doctors, including emergency physicians. The symptoms are usually attributed to a wrist sprain6 or associated fractures3 4 that in isolation do not require emergency surgery.

Why does this matter?

Emergency reduction of the perilunate dislocation is needed to reduce the pressure on the median nerve to try and prevent progression of nerve damage (fig 1). In addition, it is helpful to reduce the joint to relieve the tension on the vascular supply to the displaced carpal bones and thus reduce the risk of avascular necrosis.2 Although the long term outcome of perilunate dislocations can be poor, misdiagnosis and delayed treatment result in a substantially worse prognosis, with an increased propensity for the development of post-traumatic arthritis.4 If the initial diagnosis is missed and the patient presents late, a major salvage procedure—for example, proximal row carpectomy7 or wrist arthrodesis—may be the only surgical option.

How is it diagnosed?

Clinical

The patient’s history will often be of a high energy trauma such as a motor vehicle accident, a fall from a height, or an industrial related accident.8However, consider this diagnosis also in patients presenting with wrist pain after any fall on to an outstretched hand. The mechanism of injury is usually forced wrist hyperextension with some degree of ulnar deviation.9 Examination will show a variable amount of swelling, diffuse tenderness, deformity, and limited wrist movement. The usual bony landmarks will be lost owing to the swelling and the dislocation itself. Additionally, the patient may have altered or loss of sensation in the median nerve distribution. This finding should raise a strong suspicion of a serious wrist injury.

Investigations

For patients presenting with a swollen painful wrist and bony tenderness after an injury, arrange posteroanterior and lateral plain wrist radiography and, if clinically indicated, other special views such as a scaphoid series. Perilunate dislocation is diagnosed radiographically on the basis of the posteroanterior and lateral plain wrist radiographs, which should be taken with the x ray beam at 90° to the wrist in both views. Inadequate views in either plane are unacceptable as they may lead to a missed diagnosis or a false positive diagnosis. On a normal lateral radiograph the radius, lunate, and capitate should be approximately collinear (fig 2). However, in a perilunate dislocation, the capitate along with the rest of the carpus will appear displaced dorsally to the line of the radius, and the lunate will be angulated and flexed in the volar direction. This is called the “spilled teacup” sign, owing to the appearance of the lunate tipping volarly (fig 3). If the lunate is fully dislocated, the lunate will be completely displaced from the lunate fossa of the distal radius.

Figure2

Fig 2 Lateral plain radiograph of a normal wrist (volar aspect). The radius (blue), lunate (red), and capitate (yellow) are approximately collinear

Figure3

Fig 3 Lateral plain radiograph of a wrist with a perilunate dislocation (volar aspect). The lunate (red) is angulated volarly: the spilled teacup sign. The capitate (yellow) is displaced dorsally in relation to the lunate

On a normal posteroanterior radiograph, the carpal bones would be uniformly spaced and organised into two rows with smooth borders that can be represented by three hypothetical lines named Gilula’s lines (fig 4).10 Uneven spacing or overlapping of the carpal bones and disruption of Gilula’s lines suggests a ligamentous injury that may be associated with a perilunate dislocation (fig 5). Additionally, the lunate may appear triangular on posteroanterior films owing to its angulation and displacement.

Figure4

Fig 4 Posteroanterior plain radiograph of a normal left wrist. The carpal bones are organised into two rows. The three coloured lines illustrate Gilula’s lines, which represent the smooth borders of these carpal rows. The blue line outlines the proximal margin, and the red line outlines the distal margin of the proximal carpal row (scaphoid, lunate, triquetrum, pisiform). The yellow line outlines the proximal margin of the capitate and hamate. R=radius, U=ulnar, S=scaphoid, L=lunate, Tri=triquetrum, C=capitate, H=hamate

Figure5

Fig 5 Posteroanterior plain radiograph of a left wrist with a perilunate dislocation. The carpal bones are unevenly spaced and the carpal rows are overlapping. Obvious disruption of Gilula’s lines is visible, which suggests a ligamentous injury. The red line is dotted where it no longer represents the distal margin of the proximal carpal row: the scapholunate gap and the overlap of the triquetrum and lunate

Perilunate dislocations are often associated with fractures of the scaphoid and radial styloid and less commonly with the capitate, triquetrum, and ulna styloid. Wrist radiographs with evidence of these fractures should be scrutinised carefully. The attending doctor should be careful not to always attribute the cause of the patient’s symptoms to these fractures and thereby potentially overlook a perilunate dislocation.

How is perilunate dislocation managed?

Immediate management of a perilunate dislocation entails closed reduction under regional block or general anaesthesia. If closed reduction is successful, a hand surgeon can perform definitive surgery in the next one to two days. However, if the dislocation is irreducible by using the closed method, the patient will need emergency surgery by a hand surgeon.

Definitive management of these injuries (including cases of successful closed reduction) is open repair, stabilisation of the torn ligaments, and fixation of displaced or unstable fractures. This can be an extensive operation that may require both dorsal and volar approaches. Postoperatively, the wrist is then immobilised in a below-elbow cast or splint for about eight weeks, followed by gentle mobilisation with the guidance of a hand therapist.

Key points

  • Remain vigilant about the possibility of perilunate dislocation in patients who sustain high energy hyperextension wrist injuries with or without carpal bone fractures

  • Delay in diagnosis can result in injury to the median nerve in the acute setting and post-traumatic arthritis

  • Confirm the diagnosis with posteroanterior and lateral plain wrist radiography, which would show the “spilled teacup” sign (lunate angulated volarly) and disruption of the smooth borders of the carpal rows (Gilula’s lines)

  • Immediate management involves closed reduction, followed by early surgical repair (stabilisation and fixation)

Notes

Cite this as: BMJ 2012;345:e7026

Footnotes

  • This is one of a series of occasional articles highlighting conditions that may be more common than many doctors realise or may be missed at first presentation. The series advisers are Anthony Harnden, university lecturer in general practice, Department of Primary Health Care, University of Oxford, and Richard Lehman, general practitioner, Banbury. To suggest a topic for this series, please email us at easilymissed{at}bmj.com

  • Contributors: AVN and SB were involved in the planning of the article. All authors were involved in drafting and revising the article as well as ensuring its final approval. AVN is the guarantor.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

  • Patient consent not required (patient anonymised, dead, or hypothetical).

References