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InFocus: Scapholunate and Lunate Dislocations: Missed Injuries with Significant Morbidity

Roberts, James R. MD

doi: 10.1097/01.EEM.0000415457.18381.e3

Dr. Robertsis the chairman of emergency medicine and the director of the division of toxicology at Mercy Catholic Medical Center, and a professor of emergency medicine and toxicology at the Drexel University College of Medicine, both in Philadelphia.

Some things just don't look right on a plain film

Some things just don't look right on a plain film



Tibial plateau fractures are a challenge, occult hip fractures even more so, but hand injuries are downright villainous, designed to befuddle the best clinician or unwary student. Non-fracture injuries to the carpal bones, namely the scaphoid (AKA navicular) and lunate, can have nasty complications if mishandled. One simply cannot rely on luck or be indifferent to clandestine pathology.

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Emergency Medicine, 1st Ed.

Ch. 84: Hand and Wrist Injuries

Adams JG, Barton ED, Collings JL, et al

Philadelphia: Saunders; 2008

This book chapter and Rosen's Emergency Medicine (7th Ed., Mosby; 2009) briefly discuss scaphoid and lunate pathology relevant to the ED. I could find no erudite emergency medicine literature, and this chapter has only one reference: J Hand Surg 1980;5:226. The injuries are properly described, but their consequences and clandestine nature are not adequately emphasized. This is surprising because failure to recognize them results in significant morbidity. Carpal dislocation injuries usually require timely orthopedic consultation, ideally in the ED, for expeditious reduction and stabilization or to ensure proper and timely follow-up. Under most circumstances it seems reasonable that specialist follow-up within 24–72 hours is an acceptable alternative to immediate ED consultation. Arthroscopically guided reduction and pinning or open reduction with ligament repair is now recommended for optimal managing these acute injuries.

Scapholunate dislocation is probably the most common significant injury of the carpal bones. It can occur with minimal force to an outstretched hand. Lunate and perilunate dislocations resulting from the same mechanism are less common and require more force. When you know what to look for, these injuries can be diagnosed on a plain film, but the findings can be quite subtle. MRI is occasionally required by a hand specialist to sort out the specific pathology. Treating carpal bone injuries is complex, and involves closed and opened techniques, including wires and pins. The orthopedic literature discusses the pros and cons of each, and there appears to be a wide variety of opinions concerning optimal treatment.

Scapholunate disruption produces the classic radiographic finding termed the “Terry Thomas sign.” Mr. Thomas was a British comedian who had a noticeable gap between his front teeth. This dental peccadillo resembles the widened space (greater than 2 mm) between the scaphoid and lunate bones when they become forcefully dislocated. Usually obvious on a PA radiograph, views taken with a clenched fist and with ulnar deviation accentuate widening of the scapholunate joint.

Lunate pathology is problematic for clinician and patient. The lunate itself can be dislocated, or the other carpal bones can be dislocated around the lunate (perilunate dislocation). Always identify the position of the lunate bone in addition to looking at the scaphoid and lunate space. Herzberg et al noted that as many as 25 percent of patients with the more complicated perilunate dislocation did not have the diagnosis made on initial evaluation. (J Hand Surg 1993;18A:768.) One of four such injuries will go undiagnosed on the initial ED visit. While a scapholunate dislocation is circumscribed pathology, lunate and perilunate dislocations are more complex, encompassing a variety of presentations and permutations. Similar to scapholunate disruption, once you appreciate the radiographic transposition of a dislocated lunate bone on the lateral x-ray, you'll focus on that pathology in a nanosecond.

All disruptions of normal carpal anatomy, however, present a similar quandary to the clinician. Learn how to spot abnormal looking and abnormal positioning of all carpal bones.

COMMENT: The Herzberg article describes 16 cases of lunate pathology undiagnosed for up to an amazing 22 years after injury. Exactly why this occurred is obscure, but likely they were missed by a clinician and seemed to get better, the patient never went to a doctor, or the pain and swelling gradually resolved and no one was the wiser until a hand surgeon entered the scene. Thirty percent of perilunate dislocations treated within one week of injury had post-traumatic arthritis; some had avascular necrosis. This article says standard of care is about one week for hand surgeons to diagnose these injuries and start definitive treatment. Much of the morbidity was related to the type and degree of injury, but delay of therapy was thought problematic. Postoperative arthritis from carpal bone injuries can be as high as 60 percent, however, even under the best of circumstances.

The space between the front teeth of British actor Terry Thomas resembles the space between the scaphoid and lunate bones (more than 2 mm) in a scapholunate dislocation, aptly termed the Terry Thomas sign

The space between the front teeth of British actor Terry Thomas resembles the space between the scaphoid and lunate bones (more than 2 mm) in a scapholunate dislocation, aptly termed the Terry Thomas sign

Scaphoid and lunate malpositioning present with pain after a fall on an outstretched hand. It is usually accompanied by significant soft tissue swelling, throbbing pain, and, of course, no fracture on x-ray. Correct diagnosis not only hinges on a firm understanding of anatomy and radiology nuances, but also an appreciation that a grossly swollen and painful hand or wrist is often not a simple contusion or sprain. Importantly, if carpal bone anatomy is not your forte, simply x-ray the other side for comparison; they should look the same. Scaphoid and lunate space integrity and positioning of the lunate and companion carpal bones are on the checklist of specific radiographic entities to peruse following hand or wrist trauma. The radiographic findings are characteristic if you know what to look for, but if you only search for a fracture, your diagnostic acumen will be inadequate.

All emergency physicians, as well as our PA, NP, fast track, and walk-in clinic colleagues, should be aware of these two unusual but rather devastating hand injuries. Hand and wrist trauma is omnipresent in the ED. Fortunately, scapholunate and lunate/perilunate dislocations are uncommon, but if you have not come across them, you need to work more shifts. Both have been missed or unappreciated for decades, and most clinicians will likely have one in their M&M file. Both injuries have the potential to produce long-term pain and disability, even when recognized and treated early by the world's best hand surgeon. But when diagnosis is delayed, you will be accused of contributing to the entire poor outcome, even though your part was minimal. When an injury is missed, it's difficult for a patient to reconcile that his initial trauma was the quintessential true felon, not the neophyte doctor who gave him a hasty evaluation in the ED. Mere mortals, however, cannot always hone in on this diagnosis on the first encounter.

The scapholunate dislocation is a classic case where the clinician thinks something must be wrong because of impressive pain and swelling, but just can't seem to pinpoint a fracture on the x-ray. This is not a fracture, but it can be heinous injury. The key is knowing that the space between the two carpal bones on the standard PA radiograph is normally more than 2 mm. Likewise, when closely examined, a misplaced lunate just looks weird.

These injuries may be appreciated only when the patient returns asking for more Percocet or is concerned about persistent swelling. The diagnosis may be baffling, but the pearl is that even though no fracture is present on your second look at the x-ray, further investigation is warranted. These injuries should not escape the radiologist's overread. When a patient returns with continuing symptoms, don't only look at the original film; always check the final reading in case you are out of the QA loop.

The old medical school axiom, “no one ever sprains a wrist,” is likely an overstatement and wrist sprains certainly do occur. One must approach a painful sprain of the wrist with skepticism because scapholunate and lunate dislocations will flummox the neophyte more often than not. The key to suspecting and tracking down the correct diagnosis is knowing that prodigious swelling of the dorsum of the hand is a surface manifestation of underlying badness. If you don't see a fracture on the x-ray, ask a colleague or a radiologist to lay another set of eyes on the film. Be generous with comparison films and CT/MRI if symptoms persist. Once you understand the anatomy, these injuries will be etched in your mind forever. These two entities should be the first things to rule out in the patient who has too much pain and swelling of the wrist to justify a simple sprain diagnosis.

This patient fell on an outstretched hand, and five days later still had significant swelling and pain, left

This patient fell on an outstretched hand, and five days later still had significant swelling and pain, left

Lunate dislocation results in a characteristic triangular appearance of the lunate on the PA view due to volar rotation of the lunate

Lunate dislocation results in a characteristic triangular appearance of the lunate on the PA view due to volar rotation of the lunate

A painful wrist should be given requisite respect on a return visit. A few days' delay will not affect the final outcome, but finding the pathology a month later is problematic. These injuries are classic examples of why it's best to splint all painful wrists, schedule a definite follow-up visit within 48–72 hours, and not rely only on the “return if worse or not better” platitude. One may appreciate specific proximal carpal bone tenderness on examination, but these injuries often cause the patient to jump when you merely touch his skin, and identifying the exact focus of injury is not easy. The best tactic may be a repeat examination after things have quieted down.

The more subtle perilunate dislocation in the PA view is abnormal, and shows overlap of the distal and proximal carpal rows

The more subtle perilunate dislocation in the PA view is abnormal, and shows overlap of the distal and proximal carpal rows

I see no reason to eschew a hand splint for a few days on almost any hand or wrist injury. Make sure you splint it properly, and don't compound soft tissue swelling by applying a subpar splint. Common mistakes are wrapping with overly tight ACE bandages and splinting in flexion rather than a neutral or slightly extended posture. Splinting the wrist in flexion, coupled with the hand held down to the side, almost guarantees edema of the dorsum of the hand on follow-up. Like facial sutures, your splint is your signature in the ED, and a good splint makes you look like a pro and a bad one establishes you as a bungler. You may not be able to diagnose these subtle injuries in every case, but you can certainly apply a state-of-the-art splint that impresses a colleague in follow-up.

You should never look for what you suspect when viewing any x-ray on the first go-round. If you think a patient has a hip fracture, look for that pathology last, first scanning for pubic ramus fractures, acetabular fractures, or other pathology at the edges of the film. It's like not being fooled by a large plural effusion that grabs your attention at first glance at a chest x-ray while you miss subtle air under the diaphragm or a widened mediastinum that would be easily seen if you didn't stop your radiographic sleuthing.

Once a scapholunate dislocation is appreciated, your task is to provide expeditious follow-up with a colleague who can fine-tune the healing process. Finding a hand surgeon willing to take an uninsured and unreliable patient is easier said than done in today's environment. Of course, things usually work out if the patient is tuned into the system, has the chutzpah to forge on after the first medical system roadblock, or has the wherewithal and perspicacity to understand and even be a bit pushy. The office secretary who is trained to ask for insurance or money in the first few minutes of the conversation will thwart many timid patients. Ever try getting a hand surgery or dermatology appointment for a family member? Good luck.

Don't expect all pain and swelling in the hand to be due to a fracture, and don't be satisfied with the diagnosis of a sprained or bruised hand or wrist unless symptoms are minor and fleeting. Learn to appreciate the subtle findings of dislocations or abnormal soft tissue spaces. Splint all painful injuries, and advise a routine follow-up of seriously injured hands and wrists. Don't allow three weeks to pass while doling out more opioids and assuring a patient that it will work itself out. Emergency physicians cannot be expected always to diagnose a lunate or scapholunate disruption on the first encounter, but morbidity will be minimized with proper splinting and follow-up. Of course, once this injury occurs, it's rather naïve to think that normal hand function and painless range of motion are a given.

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