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Injury Vol. 28, No.1, pp. 1-8, 1997 Copyright © 1997 Elsevier Science Ltd. All rights reserved

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The diagnostic management of suspected scaphoid fracture

M. M. C. Tiel-van BuuP, W. Roolker1, A. H. Broekhuizen2 and E. J. R. Van Beek3

IDepartment of Nuclear Medicine, 2Department of General Surgery!fraumatology and 3Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands

The role of radiography and bone scintigraphy in the diagnostic management of patients with clinically suspected scaphoid frac­ture after carpal injury is reviewed. Evidence is provided that bone scintigraphy is indicated in patients with negative initial scaphoid radiographs. A normal bone scan excludes scaphoid . fracture, and a positive bone scan sufficiently confirms the presence of clinically relevant scaphoid fracture. Furthermore, this review assesses the possibility of non-invasive additional radio­graphs, for the diagnosis or exclusion of scaphoid fracture as a means of avoiding bone scintigraphy in patients with negative first-day X-series. © 1997 Elsevier Science Ltd.

Injury, Vol. 28, No.1, 1-8, 1997

Introduction Recently, there has been an increasing interest in the diagnostic and therapeutic problems surrounding suspected scaphoid fracture. This has also been a focus of attention in this joumaP. It is well known that fractures of the scaphoid bone are not always identified by radiographic examination due to the unique shape and position of the scaphoid in the carpus. The anatomy, as well as the function, of the carpal bones has intrigued scientists since the sixteenth century (Figure 1)2. There was controversy over the use of radiography in the diagnosis of scaphoid fracture in the first half of this century:>-5. Soon after Destot described scaphoid fractures in 1905, scaphoid radiography became more refined with the introduction of ulnar deviation in the posteroanterior views\ oblique views6-S, a second set of radiographs after 2 weeks9

, focusing on soft tissue changesll

l-12

, oblique views with the tube angulated 400 distalli\ digital skeletal imaging and magnifica­tion 1~.15 and transverse and longitudinal 'carpal box' radiographsl6

• Additional diagnostic procedures

included bone scintigraphi7-21, three-phase bone scintigraphy22.2.1, complex motion tomography2\ flexion-extension tomography25, wrist arthrog­raphy26, computed tomography27-29, three-dimen­sional CT3(1--33 and magnetic resonance imaging34

•35.

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Figure 1. The carpus illustrated by Vesalius in 1543.

2 Injury: International Journal of the Care of the Injured Vol. 28, No. I, 1997

Figure 2. A 3D-year-old woman clinically suspected for scaphoid fracture after a fall onto her outstretched hand. A-D, X-rays negative on first day: A, posteroanterior (PA) with the hand in neutral position; B, oblique with the hand 10° in supination and maximal ulnar deviation; C, lateral view with the distal arm 15° elevated; D, PA-view with the tube 40° tilted distally. E, F, 'Carpal-box' radiographs on the first day positive: E, longitudinal view; F, transverse view. G, H, Bone scintigraphy, static phase positive: G, anterior; H, lateral.

Tiel-van Buul et al.: Diagnostic management of suspected scaphoid fracture 3

G

Figure 2. continued.

4 Injury: International Journal of the Care of the Injured Vol. 28, No.1, 1997

The involvement of so many imaging techniques in the diagnosis of scaphoid fracture indicates its complexity.

Several factors are responsible for the continued search to improve the diagnostic methods. The wrist is subject to a high level of use and abuse, both in the activities of daily life and in sports. The scaphoid occupies a unique position in the carpus that bridges the proximal and distal rows, and adds to wrist stability and mobility, but is vulnerable to fracture and dislocation. Thus, a healthy scaphoid is of paramount importance for the adequate function of the hand and wrist.

Fractures of the scaphoid represent 2-7 per cent of all fractures and account for 51-9b per cent of fractures of the carpal bones23,36,37. Scaphoid fracture typically occurs in patients between 15 and 40 years of age following a fall onto an outstretched hand. In 3 per cent of cases, scaphoid fracture is caused by flexion injury38,39. Tenderness in the anatomical snuffbox on physical examination is the clinical hallmark of scaphoid fracture, But fractures of the radial styloid, trapezium, and metacarpals I and II, as well as many sprains, also have the same features40

,41,

Ligamentous attachment to both the proximal and distal carpal rows through the scapholunate and

Figure 3. A 46-year-old man clinically suspected for scaphoid fracture: A, oblique with the hand 10° in supination and maximal ulnar deviation negative; B, static bone scan anterior view positive; C, computed tomography, transversal slice positive,

Tiel-van Buul et al.: Diagnostic management of suspected scaphoid fracture 5

scaphotrapezial ligaments and the sling of the radio­scaphocapitate ligament traversing its relatively narrow waist subject this area to extremely high stress during forced dorsiflexion. For this reason, scaphoid fractures occur at the waist in 63-68 per cent of cases40

, 16-28 per cent involve the proximal pole, and the remainder involve the distal pole42. Most fractures of the scaphoid are transversely oriented to the scaphoid and undisplaced. Asso­ciated injuries include fractures of the capitate, radial styloid process, triquetrum, and perilunate dislocation.

In The Netherlands (15 million inhabitants), approximately 24000 patients per year present to an AccidentlEmergency department after carpal injury36,43. This implies that general practitioners and clinicians regularly see such patients in their practice. However, many surgeons will not have the impres­sion that the frequency is that high. The root of this problem can be the low sensitivity and the low relia­bility of the traditional scaphoid X-ray series44,4S. Up to the present, many patients with carpal injury are sent home without a diagnosis or will be (tempo­rarily) immobilized without a radiographically proven fracture.

Complications While many scaphoid fractures heal uneventfully46, a number of patients will present with some complica­tion. The most common problems include avascular necrosis, non-union, malunion, carpal instability, and carpal osteoarthritis.

Avascular necrosis occurs in 3-40 per cent of all scaphoid fractures37,42. The risk of avascular necrosis is related to fracture location, displacement, and instability<7. The scaphoid's vascular anatomy protects the distal pole from this complication, whereas fractures of the middle third of the bone are at higher risk, resulting in avascular necrosis of the proximal fragment.

Non-union is defined as the absence of evidence of healing at 4 to 6 months after injury. Although there are asymptomatic patients with non-union of the scaphoid, it is an important cause of wrist disability following injury. A frequency of up to 88 per cent has been reported in initially unrecognized fractures48, whereas non-union of the scaphoid occurs in 5-12 per cent of promptly and adequately treated fractures38,49,SO. Displacement of scaphoid fractures results in more frequent non-union and prolonged time to bony union48,sl. The unstable scaphoid fracture, i.e. the fracture which becomes displaced during immobilization, has a much higher incidence of non-union indicative of some degree of carpal instability38.

Carpal instability is defined as a disruption of the normal alignment between the carpal bones or between the carpal bones and the radiuss2. Post­traumatic carpal instability mainly concerns the proximal row, which acts as an intercalated segment in the three-link joint system formed by the radius, proximal carpal row and distal carpal row with the

metacarpals. Carpal instability is inherently present in a scaphoid fracture with displacement. Fracture displacement results from disruption of palmar and dorsal scaphoid ligaments with subsequent loss of scaphoid stability. This in turn means the loss of the stabilizing strut between the proximal and distal carpal rows. The most common type of carpal instability manifests itself as a dorsal intercalary segment instability (DISI) pattern, with palmar flexion of the scaphoid and dorsiflexion of the lunates2. The incidence of carpal instability after wrist injury has been described in 5-22 per cent of cases and this may play a key role in the development of non-unionS3,S4. Degenerative arthritis was demon­strated to be a direct consequence of the displaced scaphoid fracture that gives rise to non-union or mal unionS 1

• The degree and severity of arthritic changes are progressive, often appearing as early as 5 years after fracture<2. The initial changes that may be seen involve the scaphoid, with marginal scler('~is at the fracture site and cystic or resorptive changes confined to the scaphoid alone. Degenerative arthritis with joint-space narrowing of the radioscaphoid joint and pointing of the radial styloid follows. Ultimately, pancarpal arthritis occurs. An incidence of radio­carpal arthrosis after primary healing of scaphoid fractures of 5.2 per cent was reported, and occurs secondary to malunion49.

Radiography Traditionally, radiographic examination of the carpus consisted of a posteroanterior (PA) view with the wrist in maximal ulnar deviation, one lateral and two oblique views (15 ° pronation and 15° supination). The X-ray series was repeated after 10-14 days and eventually after 6 weeks if the radiographs remained negative and the patient had persistent complaints. The sensitivity of the scaphoid X-ray series is disappointing: it decreased from 60 per cent in the first-day radiographs to 30 per cent in the follow-up radiographs4s. The reliability of the repeated radio­graphs was low: the kappa value (percentage agree­ment between observers beyond chance) for initial radiographs between experienced bone radiologists was 0.76, while it was 0.50 for follow-up radio­graphs22,4s. A diagnostic test is considered to be reliable if a kappa value of 0.60 is reachedss. This implies that first day radiographs in suspected scaphoid fracture are meaningful, while repeated radiographs do not lead to improved diagnostic management. In patients with persistent pain in the anatomical snuffbox and decreased function of the hand, additional diagnostic methods like arthroscopy may be necessary.

Because of the results described above, we changed the imaging protocol of the traditional scaphoid radiographs to the following: PA view with the hand in neutral position, oblique view with the hand in 10° supination and maximal ulnar deviation, a lateral view with the distal arm 15° elevated, and a PA view with the tube tilted 40° distally. Further­more, the additional value of 'carpal-box' radio-

6 Injury: International Journal of the Care of the Injured Vol. 28, No. I, 1997

graphs were investigated. With this device, transverse and longitudinal views showed elongated and magnified radiographs of the carpus. As a result of magnification and elongation of the carpal bones, the overlap of the various carpal bones is reduced, creating a better image of the individual bones. The results of a recent experimental and pilot study were promising16

• A subsequent statistical study of the interobserver variability between general surgeons, orthopaedic surgeons, hand surgeons, and radiolo­gists (staff and residents) show an improvement of reliability when' carpal-box' radiographs were used56

•

We expect that implementation of additional 'carpal­box' radiographs may lead to a higher sensitivity of the scaphoid X-ray series with an improvement in cost-effectiveness. Figure 2 shows the scaphoid X-ray series (A-D), longitudinal (E) and transverse 'carpal­box' radiographs (F), and anterior (G) and lateral (H) views of the bone scan of a 30-year-old woman with a clinically suspected scaphoid fracture and negative scaphoid X-rays, as (separately) judged by a radiolo­gist and a traumatologist. Bone scintigraphy was positive, and additional 'carpal-box' radiographs con­firmed a scaphoid fracture.

Bone scintigraphy In patients with negative initial radiographs, three­phase bone scintigraphy is indicated. Phase one and phase two are perfusion and diffusion images respec­tively, which are obtained immediately after injection of the radiopharmaceutical (99mTechnetium diphos­phonate). The third (static) phase, obtained 2 to 4 h pj., visualizes the osteoblast activity. This activity is significantly increased from 72 h after injury. The bone scan is suggestive of a recent fracture if the combination of hyperaemia and a delayed focally increased uptake (hot spot) in the concerned region is seen. Various studies showed that the sensitivity of bone scintigraphy was 100 per cent17

-19

,57. The positive predictive value was 93 per cent58 and the specificity was 98 per cenf45. The kappa value was high (0.81)22. In a recent prospective study in which 160 patients were included, using three-phase bone scintigraphy in the diagnostic management of scaphoid fracture, no non-union was encountered at long-term follow­Up23. In spite of the high diagnostic costs, bone scintigraphy is cost-effective because of the high sensitivity and specificity, and low incidence of pseudoarthrosis, leading to reduced therapeutic costs59

• Figure 3 shows (A) the PA radiograph, (B) the bone scan, and (C) computed tomography of a 46-year-old man with negative initial scaphoid radio­graphs and a positive bone scan. A scaphoid fracture was confirmed by computed tomography.

Diagnostic protocol As a result of extensive investigations, our hospital routinely uses three-phase bone scintigraphy as the gold standard in suspected scaphoid fracture. The current diagnostic protocol is shown in Figure 4. All patients with suspected scaphoid fracture after carpal

Clinically suspected scaphoid fracture

after a fall on the outstreched hand

I X -series, 4 directions

(eventually additional "Carpal Box"-radiographs)

I I

Negative Positive

I I Temporary immobilization 12 weeks immobilization

I Clinical persirent suspicion

3-phase bone scintigraphy

I I Positive

I Functional treatment 12 weeks immobilization"

* Adjustment of therapy if another fracture in carpus/wrist is diagnosed

Figure 4. Diagnostic protocol in suspected scaphoid fracture.

injury undergo first-day scaphoid radiographs. If these are positive, the patient is immobilized for a period of 12 weeks; if these are negative, the patient is immobilized and three-phase bone scintigraphy is performed. If the bone scan is negative, the plaster cast is removed, whereas patients are treated if a hot spot is observed. Because of its low sensitivity (30 per cent) and high interobserver variability, repeated radiographs after 10-14 days and eventually after 6 weeks are not considered to be clinically meaningful. However, the costs of bone scintigraphy are high and a bone scan cannot be performed in every hospital. A simple and cheap alternative to reduce the number of bone scans seems to be the 'carpal-box'. The value of this device in the diagnostic management of scaphoid fractures still needs to be proved. Addi­tional 'carpal-box' radiographs, transverse and longi­tudinal views with the wrist in maximal ulnar deviation, are already implemented because of the simple logistics of using this device in an Emergency department, the simplified interpretation of the radiographs, and for research reasons. Repeated radiographs can still be used to follow-up fracture healing in patients with clinical suspicion of pseudarthrosis.

The diagnostic methods in suspected scaphoid fractures are an inexhaustible subject for discussion and research. The aims are to simplify diagnostic methods, reduce costs, and improve reliability and accuracy. The role of radiologists in interpreting radiographs is important. We found that reliability and accuracy improve if the radiographs are judged

Tiel-van Buul et al.: Diagnostic management of suspected scaphoid fracture 7

by an experienced radiologist. Finally, the recently described intrasound vibration method seems promising, with a sensitivity of 100 per cent and a specificity of 95 per cent found by Finkenberg et aI.60, but its reliability is unknown and further investiga­tion is required to validate it.

Therapeutic consequences In our study2:l patients with negative initial X-ray series were treated non-operatively based on the result of the bone scan: all patients with a positive scan were immobilized for 12 weeks. The long-term result was effective: no pseudoarthrosis was encoun­tered, despite the fact that the patient population studied was similar to a series reported in the litera­ture - 40 out of 56 radiologically proven scaphoid fractures (71 per cent) were located in the waist of the scaphoid, while in ten patients (18 per cent) the fracture was located in the proximal pole and in six (11 per cent) in the distal pole61

• This was not what we had expected on the basis of literature reports (5-12 per cent). Therefore, we advise 12 weeks immobilization in a scaphoid plaster in patients with radiodiagnostic or scintigraphically proven fracture of the scaphoid. This period seems too long for incomplete fractures or avulsion from the scaphoid tuberosity as mentioned in other studies62

,6:l. How­ever, in both studies, the incidence of non-union at long-term follow-up was not investigated. A prospective study is needed to investigate whether the period of immobilization may be safely reduced in certain groups of patients (for example, children) or certain types of fractures (radiologically proven distal fractures or, for instance, after 6 weeks radiologically and clinically consolidated).

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Paper accepted 19 July 1996.

Requests for reprints should be addressed to: M. M. -c. Tiel-van Buul, MD, PHD, Diagnostic Imaging Department, F2-238 Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.