A 20-year-old man presents to the emergency department (ED) directly from the scene of a fall from a bicycle, where he lost balance and landed on his outstretched hand. He complains of pain both in the palm of his hand and in the wrist. Sound familiar? We see 2.6 million hand and wrist injuries annually in the United States and when we miss an occult or subtle injury it can be very morbid for our patients and not uncommonly leads to litigation.^1,2 For every patient who presents to the ED with a fall on outstretched hand injury (FOOSH), we need to consider not only the common distal radius fracture clearly seen on X-ray, but also five sometimes occult injuries:

• Occult distal radius fracture
• Hook-of-hamate fracture
• Distal radial-ulnar joint injury (DRUJ)
• Scapholunate injury
• Occult scaphoid fracture

I outline some of the general principles of assessing the patient after a FOOSH injury and highlight the key clinical features.

Common Things Being Common

Let’s start with the most common of these subtle injuries. The most common wrist or hand injury occult to X-ray is not the scaphoid—it’s the distal radius.³ Tenderness over the distal radial metaphysis after wrist injury is strongly suggestive of a distal radius fracture despite normal plain radiographs and fluoroscopic images.⁴ Hence, these patients should be placed in a radial wrist splint with orthopedic follow up rather than be labeled as a “wrist sprain” and sent home without a splint or appropriate follow up. Remember that age-related prevalence, when constructing an orthopedic differential diagnosis, is critical. Children and older adults have weaker long bones than young adults and are more likely to sustain a distal radius fracture after a FOOSH than a carpal bone injury.

DRUJ Injury

Often associated with distal radius fractures, but underappreciated, are DRUJ injuries. This should be considered especially when the distal radius fracture occurs with a concomitant ulnar styloid fracture.⁵ The DRUJ injury has been coined “the forgotten joint of the wrist” as missed DRUJ injuries are common.⁶ A missed DRUJ injury may lead to chronic wrist supination deficit and pain, which can be prevented with surgery in some cases, so early diagnosis in the ED is important. There is a spectrum of DRUJ injuries from minor sprain to subluxation to dislocation. The mechanism of injury may be a sudden supination or pronation force or a FOOSH. Patients may report a clicking sensation with forearm supination or pronation. On physical exam it is imperative to screen for an associated DRUJ injury in all patients with wrist injuries, especially those with distal radius and ulnar styloid fractures. We sometimes tend to palpate the distal radius, suspect a distal radius fracture, and stop there. The three most useful physical exam findings of DRUJ instability are point tenderness to palpation over the divot between the distal radius and ulnar styloid, limited range of motion with supination and pronation and the ballottement test.⁶ This test involves grasping the ulnar styloid while stabilizing the distal radius to assess for increased movement compared to the contralateral wrist, an often overlooked physical exam maneuver that should be considered in all wrist-injured patients. DRUJ injuries are often occult to X-rays, but it is imperative to scrutinize the lateral wrist X-ray for a widening of greater than 2 mm of the DRUJ or a loss of overlap of the distal radius and ulna on the lateral film suggesting a subluxation or dislocation of the DRUJ. While most patients with distal radius fractures can be managed in the ED with a below-elbow splint with the forearm in a neutral position, patients with associated DRUJ injuries should be placed in an above-elbow splint with their forearm in supination to prevent pronation of the wrist.

Hamate Fracture

The next of the five major wrist or hand injuries to consider in patients after a FOOSH is the hook-of-hamate fracture. Traditional teaching of the mechanism of the hook-of-hamate fracture is a direct blow from an elongated implement gripped in the hand such as a ski pole, golf club, or baseball bat. It is under-recognized that hook-of-hamate fractures can result from a FOOSH and occur concomitantly with a scaphoid fracture.⁷ Knowing the surface anatomy of the carpal bones is essential. The hook of the hamate lies 2 cm distal and 1 cm radial to the pisiform and can be felt on deep palpation; it should be palpated routinely in patients after a FOOSH. Picking these injuries up in the ED is important because if missed and not immobilized, non-union may ensue and the patient may require surgical intervention.⁸ If the hamate is tender on physical exam, it is important to order an additional X-ray view with the standard hand X-ray views: the hook of the hamate or carpal tunnel view is more sensitive than the standard wrist X-ray views for hook-of-hamate fractures. An important pitfall is assuming no fracture if a hook-of-hamate fracture is suspected clinically and the standard wrist views as well as the hook-of-hamate or carpal tunnel view are negative. The sensitivity of the hook-of-hamate view is only 40 percent for fracture.9 Similar to scaphoid fracture occult to X-ray, if clinically suspected, immobilize and arrange orthopedic follow-up regardless of the X-ray findings.

Lunate Ligamentous Injury

Another overlooked injury is the lunate ligamentous injury including the scapholunate injury. Age-related prevalence of wrist or hand injuries is again important here. Children with open growth plates are more likely to sustain fractures involving growth plates or diaphyseal-metaphyseal junction of the distal radius, while those older than years are more prone to classic long-bone fractures. For people between 15 and 60 years old, carpal bone and inter-carpal ligament injuries occur more often. Hence, carpal bone injuries occur predominantly in young adults as a result of a high-energy mechanism. Lunate ligamentous injuries lie on a morbidity spectrum ranging from scapholunate sprains to dissociation and dislocation. Again, knowledge of surface anatomy is essential for accurate physical exam testing: the divot distal to Lister’s tubercle and a few millimeters ulnar is the scapholunate space. This space can also be identified by palpating 2 cm ulnar to the snuffbox. If a patient has point tenderness here, assume a scapholunate injury until proven otherwise.

There are several X-ray findings to consider: the radius-capitate-lunate alignment, which if absent may indicate a scapholunate injury. Knowing the normal shapes of the scaphoid and lunate is important to help identify X-ray abnormalities that may suggest a scapholunate injury. The scaphoid on the anterior-posterior (AP) view is normally the shape of a boat. The lunate on lateral view appears like a half-moon while on the AP view it appears roughly square-shaped. A change in any of these shapes may signify a scapholunate injury. The signet ring sign of the scaphoid is a rounded appearance of the cortex of the scaphoid tubercle on the AP view of the wrist, suggesting a subluxation. The pizza sign or piece of sign is the triangular appearance of the lunate on the AP view, suggesting a lunate dislocation. A widening of the scapholunate space of 3 to 5 mm on the AP view is suggestive of a scapholunate dissociation. This has been termed the Terry Thomas Sign and the David Letterman Sign: The gap between these celebrities’ dental incisors appears wide like a widened scapholunate space on the AP view.¹⁰ A clenched fist view may be necessary to diagnose a significant scapholunate ligament sprain.¹¹ To pick up a subtle scapholunate dissociation and distinguish it from baseline physiologic widening of the scapholunate space, consider bilateral X-rays of the wrist, as some people have baseline physiologic widening.

SLAC Injury

One of the reasons that it is important for us to pick up scapholunate injuries in the ED is that some patients may progress to scapholunate advanced collapse (SLAC), a consequence of untreated scapholunate dissociation or complete rupture of the ligament. In SLAC the capitate collapses toward the radius, resulting in chronic arthritis and pain.

Occult Scaphoid Fracture

The occult scaphoid fracture is the most common occult carpal-bone fracture.¹² Like lunate ligamentous injuries, understanding age-related prevalence is important for scaphoid fractures, which occur more commonly in young adults. Anatomical snuffbox tenderness, scaphoid tubercle tenderness on the palmar aspect of the wrist, and pain on axial compression of the thumb should always be carried out on physical exam in young adults after a FOOSH. Sensitivity for each of these tests has been reported to be 100 percent, with a specificity of 74 percent when all are positive.¹³ Axial compression of the thumb has been shown to have the weakest diagnostic performance of the three tests, likely because many older individuals have arthritis in the first carpometacarpal joint, leading to a false-positive test.¹⁴ Two nuances in performing these physical exam tests are key: snuffbox tenderness should be performed with the patient’s wrist in ulnar deviation to bring the proximal scaphoid into the snuffbox, and palmar scaphoid tenderness should be elicited at the base of the thenar eminence with the wrist in neutral or radial deviation to bring out the scaphoid. Two additional tests for scaphoid fracture include pain on resisted supination of the wrist, which has been shown to have a 100 percent sensitivity, and the clamp sign, where the patient uses a pincer grasp around their scaphoid with their thumb in the snuffbox and index finger of the palmar scaphoid tubercle when asked where their point of maximal pain is.¹⁵ This test has a high positive likelihood ratio for scaphoid fracture.¹⁶

While guidelines recommend CT imaging for suspected scaphoid fractures occult to X-ray within three to five days, CT may miss significant scapholunate ligament injuries and may falsely reassure clinicians who may neglect to splint and arrange follow-up for these patients.^12,17 Another imaging strategy option is to obtain a scaphoid cone view X-ray, immobilize the patient’s wrist in a removable splint or radial-gutter plaster splint, and arrange follow-up in 10 to 14 days for re-examination and repeat X-ray if necessary.

Next time you are chatting with a colleague or resident, ask them what they think the most common occult fracture of the wrist is. Chances are they’ll be surprised to learn that the answer is distal radius fracture.

Many thanks to Dr. Arun Sayal and Dr. Matt Distefano for their tag-teamed contributions to the EM Cases podcast which inspired this column.

Dr. Helman is an emergency physician at North York General Hospital in Toronto. He is an assistant professor at the University of Toronto, Division of Emergency Medicine, and the education innovation lead at the Schwartz/Reisman Emergency Medicine Institute. He is the founder and host of Emergency Medicine Cases podcast and website.

References

1. Ferguson R, Riley ND, Wijendra A, et al. Wrist pain: a systematic review of prevalence and risk factors, what is the role of occupation and activity? BMC Musculoskelet Disord. 2019;20(1):542.
2. Abraham MK, Scott S. The emergent evaluation and treatment of hand and wrist injuries. Emerg Med Clin North Am. 2010;28(4):789-809.
3. Dóczi J, Springer G, Renner A, et al. Occult distal radial fractures. J Hand Surg Br. 1995;20(5):614-7.
4. Glickel SZ, Hinojosa L, Eden CM, et al. Predictive power of distal radial metaphyseal tenderness for diagnosing occult fracture. J Hand Surg Am.2017;42(10):835.e1-835.e4.
5. Kazemian GH, Bakhshi H, Lilley M, et al. DRUJ instability after distal radius fracture: a comparison between cases with and without ulnar styloid fracture. Int J Surg. 2011;9(8):648-51.
6. Mirghasemi AR, Lee DJ, Rahimi N, et al. Distal radioulnar joint instability. Geriatr Orthop Surg Rehabil. 2015;6(3):225-9.
7. Mandegaran R, Gidwani S, Zavareh A. Concomitant hook of hamate fractures in patients with scaphoid fracture: more common than you might think. Skeletal Radiol. 2018;47(4):505-10.
8. Kim H, Kwon B, Kim J, et al. Isolated hook of hamate fracture in sports that require a strong grip comprehensive literature review. Medicine (Baltimore).2018;97(46):e13275.
9. Andresen R, Radmer S, Scheufler O, et al. Optimierung von konventionellen Röntgenaufnahmen zur Erkennung von Hamulus ossis hamati Frakturen [Optimization of conventional X-ray images for the detection of hook of hamate fractures]. [German] Rontgenpraxis. 2006;56(2):59-65.
10. Neill A. Anatomy for emergency medicine 018: EM Ireland website. Published June 11, 2012. Accessed February 16, 2024.
11. Dietrich TJ, Toms AP, Cerezal L, et al. Interdisciplinary consensus statements on imaging of scapholunate joint instability. Eur Radiol. 2021;31(12):9446-58.
12. Clementson M, Björkman A, Thomsen NOB. Acute scaphoid fractures: guidelines for diagnosis and treatment. EFORT Open Rev. 2020;5(2):96-103.
13. Parvizi J, Wayman J, Kelly P, et al. Combining the clinical signs improves diagnosis of scaphoid fractures. A prospective study with follow-up. J Hand Surg Br. 1998;23(3):324-7.
14. Duckworth AD, Buijze GA, Moran M, et al. Predictors of fracture following suspected injury to the scaphoid. J Bone Joint Surg Br. 2012;94(7):961-8.
15. Cohen A, Reijman M, Kraan GA, et al. Clinically suspected scaphoid fracture: treatment with supportive bandage or cast? ‘Study protocol of a multicenter randomized controlled trial’ (SUSPECT study). BMJ Open. 2020;10(9):e036998.
16. Carpenter CR, Pines JM, Schuur JD, et al. Adult scaphoid fracture. Acad Emerg Med. 2014;21(2):101-21.
17. Pappou IP, Basel J, Deal DN. Scapholunate ligament injuries: a review of current concepts. Hand (NY). 2013;8(2):146-56.