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1 All authors: Department of Radiology, Duke University Medical Center, Erwin Rd., Rm. 1504, Durham, NC 27710.
Received May 15, 2001;
accepted after revision June 25, 2001.
Presented at the annual meeting of the American Roentgen Ray Society,
Seattle, April-May 2001.
Abstract
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MATERIALS AND METHODS. Our modified protocol consists of coronal thin-section T1-weighted and fast spin-echo T2-weighted MR images with fat saturation. A review of the literature was performed to assess the accuracy of clinical examination, radiography, and other modalities in the evaluation of scaphoid fractures of the wrist. Charges for this procedure are compared with charges for traditional follow-up.
RESULTS. Three of four patients with positive results at clinical examination and negative findings on initial radiographs will be needlessly immobilized and monitored. The charges to the patient at our institution for screening MR imaging of the wrist are $770. The total charges to the patient with the traditional protocol, which would not be necessary with screening MR imaging, are $677 or more if a diagnosis is not made at this time. Bone scanning or routine MR imaging is often eventually used.
CONCLUSION. Cost analysis at our institution suggests the two protocols are nearly equivalent from a financial standpoint. The loss of productivity for patients who are unnecessarily in casts or splints may be substantial. Screening MR imaging of the wrist in this setting is becoming accepted at our institution in a manner similar to screening MR imaging of the hip.
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Modified MR imaging of the wrist is offered at our institution at the time of initial presentation to screen for radiographically occult scaphoid fractures. MR imaging is performed on a 1.5-T magnet (General Electric Medical Systems, Milwaukee, WI) with a dedicated wrist coil. This shortened study consists of 3-mm (0.3-mm gap) coronal T1-weighted spin-echo (TR range/TE range, 500-800/20-30; 2 excitations) and T2-weighted fast spin-echo (TR/TE range, 4000/80-120; 2 excitations) images with fat saturation and a matrix of 256 x 192. Fracture is identified as a linear area of low signal intensity on T1- and T2-weighted images (Fig. 1A,1B). Similar sequences have proven accurate for detecting fracture in both the hip and the wrist [1,2,3,4].
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We compared charges for the clinical protocol when using screening MR imaging with traditional charges for follow-up, which include charges for the initial orthopedic consultation in the emergency department, casting in the emergency department, a follow-up orthopedic appointment in 7-10 days, repeated wrist radiography, and, often, office fluoroscopy. Actual case scenarios are presented to emphasize particular points. Cases were drawn from our MR imaging database for the 6-year period 1995-2000. During that time, 334 wrist studies were performed; seventeen (5%) were performed to rule out scaphoid fracture. Eight (47%) of these 17 were performed in the most recent year, 2000, which indicates increasing use of MR imaging in this scenario.
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Our review of the recent literature to evaluate the negative predictive value of negative initial radiographs in the setting of strong clinical suspicion, found a range of 50-87%, with a weighted average of 74% (Table 2). These figures imply that three of every four patients with negative findings on initial radiographs will likely undergo needless immobilization.
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The charge (professional and technical) to the patient at our institution for screening MR imaging of the wrist is $770. The reduction from a charge of $1256 for standard wrist MR imaging is achieved primarily through reduction of the technical component. The clinical protocol for treatment of suspected scaphoid fracture is summarized in a flowchart (Fig. 2). The potential added charges to the patient who follows a traditional protocol that are negated by the application of screening MR imaging of the wrist in the emergency or acute care setting are summarized in Tables 3 and 4.
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The following actual case scenarios are offered. Charges that may have been avoided by initial screening MR imaging are in parentheses or brackets.
Case Scenario 1
Day 1.—The patient was a 23-year-old woman who flipped and
fell backward onto her outstretched arm and presented with elbow and wrist
pain (Fig.
3A,3B,3C).
Radiographs at the urgent care center showed a nondisplaced fracture of the
radial neck. No wrist fracture was identified, but snuffbox tenderness was
present. The patient's wrist was splinted ($154), and she was referred to an
orthopedist.
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Day 6.—At orthopedic follow-up ($135), the patient had swelling and point tenderness in the snuffbox region. The orthopedic report stated:
Given the snuff box tenderness, the patient was placed in a short arm thumb spica bandage [$159] for possible scaphoid fracture. I will have the patient return to the clinic in one week. At that point, we will remove the thumb spica and reexamine her wrist. If she's continuing to have scaphoid tenderness, repeat x-ray will be obtained to determine whether or not there is any fracture line evident within the scaphoid. If there's no fracture line evident and she's continuing to have tenderness, then we will obtain either a bone scan or MR imaging to fully evaluate for nondisplaced scaphoid fracture.
Day 13.—The patient's cast was removed. She continued to have tenderness in the snuffbox region. Radiographs ($130) of the wrist showed a mild degree of irregularity on the radial aspect of the scaphoid bone but no obvious fracture line. The patient's wrist was placed in a thumb spica cast. MR imaging was ordered.
Day 24.—Complete wrist MR imaging ($1256) showed increased T2 and decreased T1 signals throughout the scaphoid bone, which are compatible with edema. A focal area of linear decreased signal intensity on T1- and T2-weighted images extended through the proximal pole of the scaphoid bone, which is compatible with a nondisplaced fracture.
Day 27.—The patient returned to the clinic ($72) for the MR imaging results, which showed a scaphoid fracture. The cast was not changed because it was in good condition.
Day 41.—The cast was removed. The patient continued to have some tenderness and swelling around the scaphoid bone on the dorsal aspect of a wrist. Radiographic findings were again negative. The patient's wrist was re-placed in a short arm thumb spica splint.
Summary.—This scenario shows a situation in which 24 days were required to arrive at the diagnosis of scaphoid fracture. Although the wrist was treated appropriately in the face of snuffbox tenderness, additional charges of $578 were incurred before definitive diagnosis was made at MR imaging. The additional expense of full MR imaging of the wrist ($486) versus a screening protocol was incurred. As late as day 41, follow-up radiographs showed negative results.
Case Scenario 2
Day 1.—The patient was a 16-year-old boy who fell onto his
outstretched hand, incurring a dorsiflexion injury to the right wrist (Fig.
4A,4B,4C).
He was seen at a family medical clinic, where radiographs were obtained that
raised the question of a possible scaphoid fracture. The patient's hand was
splinted ($154), and he was referred to an orthopedist.
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Day 2.—At orthopedic consultation ($135), the patient had mild tenderness over the region of the scaphoid bone, but only with firm pressure. Under office fluoroscopy ($150), a fracture was not seen. The clinical impression questioned a nondisplaced scaphoid fracture versus a sprain of the right wrist.
Since the wrist was minimally symptomatic, it was suggested to try a little immobilization with a short arm thumb spica cast [$159] and return in ten to 14 days for the re-x-ray. If the radiographs are completely normal and he has no tenderness would then discontinue the cast. If the radiographs are still suspicious but not confirmatory, would recommend CT scan.
Day 10.—The orthopedic report stated:
I was...notified of the patient's dissatisfaction with his current splint. He was sent to hand therapy to have a different type of splint made....[H]is MR imaging was scheduled for the 25th and the patient did not want to wait that long because of his inability to write in his current splint. MR imaging is moved up to the 20th. I suggested they put the cast back on as a splint until he can have the study and if the study is negative, then he does not need anything.
Day 13.—MR imaging of the wrist showed a nondisplaced fracture through the scaphoid waist.
Day 16.—The orthopedic report stated:
...In light of the MR images revealing a scaphoid fracture, the patient was brought back to the clinic today for examination, fluoroscopy and casting. On the office fluoroscopy [$150], the scaphoid is definitely fractured.
Summary.—This scenario shows that the orthopedic surgeon's initial direction was to perform radiographic follow-up and splinting only, then to perform CT if still unsure. The orthopedic surgeon was possibly swayed by initial negative findings on office fluoroscopy. MR imaging was recommended as a more sensitive study, and a full study was scheduled. Possibly because of inexperience with MR imaging, the clinician performed one further office fluoroscopy that confirmed the fractured scaphoid on day 16. Screening MR imaging ($770) would have prevented $589 in office charges plus an additional $486 from the cost of full wrist MR imaging that was performed.
Case Scenario 3
Day 1.—The patient was a 14-year-old boy who fell on his
right face and ulnar wrist (Fig.
5A,5B,5C).
On presentation to the emergency department, he was found to have fractures of
his right facial bones and the ulnar styloid of his right wrist. His right
wrist was then placed in a splint ($154), and an orthopedic consultation was
ordered.
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Day 10.—After orthopedic evaluation, the right wrist splint was removed. The right wrist had tenderness over the ulnar styloid, and the distal radial ulnar joint showed trepidation with stress. Radiographs of the right wrist ($85) again showed a nondisplaced fracture of the ulnar styloid. The clinician's impression was right wrist sprain with associated ulnar styloid fracture, possible disruption of the distal radioulnar joint, and possible disruption of the triangular fibrocartilage complex. The orthopedic report stated:
The patient should continue to wear the brace for protection.... I have suggested that we obtain MR imaging of the right wrist to further clarify his pathology. He will return after the study for final diagnosis and disposition.
Day 12.—The orthopedic report stated:
Complete MR imaging ($1298) of the right wrist and hand is reviewed.... He is noted to have a nondisplaced scaphoid body fracture. The triangular fibrocartilage has a small nondisplaced tear. His ulnar styloid fracture is visible.
Day 17.—The orthopedic report stated:
The patient's right wrist is somewhat improved in terms of local tenderness. He's placed into a short arm thumb spica cast. He will follow-up in this office in four weeks for removal of his cast and then x-ray of hand and wrist out of cast.
Summary.—This scenario shows the inability of even the orthopedic surgeon to initially suspect the presence of scaphoid fracture in the setting of a generalized wrist injury (ulnar styloid fracture and possible distal radioulnar disruption). MR imaging clearly showed not only the ulnar styloid fracture but also the radiographically occult scaphoid fracture and triangular fibrocartilage injury. Distal radioulnar joint disruption was discounted on the basis of MR imaging. The patient's wrist was not fully encased in a cast until day 17.
Case Scenario 4
The patient was a 20-year-old man who presented with mild snuffbox
tenderness after a fall on outstretched hands during basketball practice (Fig.
6A,6B).
Initial radiographic findings were negative. The patient's wrist was splinted.
MR imaging of the wrist was performed later that day, revealing a normal
scaphoid. The patient returned to normal activity without negative
consequences.
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Summary.—This scenario shows the usefulness of immediate MR imaging in avoiding inconvenience to the patient and decreasing hindrances to productivity.
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As our review of the literature indicated, positive findings at clinical examination and subsequent negative wrist series may lead to unnecessary outpatient follow-up appointments, unnecessary immobilization, and additional exposure to radiation. This additional radiation exposure includes office fluoroscopy, which is often used by the consulted orthopedic surgeon when follow-up radiographs have negative results, adding to patient expense and radiation dosage. To our knowledge, no substantial work in the literature addresses the sensitivity and specificity of fluoroscopy in the setting of negative radiographic findings.
Frequently, further negative imaging results occur at the first follow-up appointment in the continued setting of a positive physical examination. Tiel-van Buul et al. [10,11,12,13] found 25% of scintigraphically confirmed scaphoid fractures followed up for at least 1 year could not be confirmed by radiography. A second follow-up appointment may incur charges (up to $547) nearing those of the initial appointment by virtue of similar repeated diagnostic procedures and recasting.
Bone scanning, which is more sensitive and more specific, has been advocated by many as an alternative to immobilization and follow-up [10,11,12,13,14]. The cost at our institution ($639) would approach that of unnecessary clinical imaging and therapeutic follow-up (Tables 3 and 4). In practice, however, this examination is frequently ordered as a more complex study (e.g., with flow studies) with increased charges. Additionally, we can find no case of nuclear bone scanning being used on an emergent basis, thus again resulting in casting of the patient's wrist for at least some time.
Many recent studies suggest equal sensitivity and better (sometimes 100%) specificity for MR imaging in accurately detecting radiographically occult scaphoid fractures [3, 4, 15, 16]. On MR imaging, the fracture line will appear as a discrete focus of linear low T1 and T2 signals. Additionally, a diffuse low T1 signal and a high T2 signal are seen in the surrounding scaphoid bone, representing marrow edema. However, bone marrow edema alone does not represent fracture but rather contusion. The T1- and T2-weighted images are often complementary in cases with subtle findings. Diffuse bright edema on T2-weighted MR images (Fig. 3A,3B,3C) and low-signal-intensity edema on T1-weighted images (Fig. 5A,5B,5C) may obscure a subtle fracture line that is seen on the other sequence.
Fowler et al. [3] compared the sensitivity and specificity of MR imaging for detection of radiographically occult scaphoid fractures with that of bone scintigraphy. In 40 patients, bone scanning and MR imaging findings were in agreement. In three patients, a discrepancy existed between the imaging modalities; in all three cases, MR imaging was found to be more sensitive and more specific. Thorpe et al. [15] concluded that MR imaging showed better interobserver agreement for scaphoid injury and fewer false-positive results than bone scanning.
Cook et al. [16] studied 18 skeletally immature patients who had presented to the emergency department within 2 days of acute wrist trauma. Those authors reported normal findings on initial MR images to have a negative predictive value of 100%. Of 10 patients with a scaphoid abnormality on MR imaging, six had fractures and four had regional bone marrow edema. Initially, eight of 10 fractures were radiographically occult, although some eventually became evident on later studies. Those lesions with bone marrow edema did not progress to fractures.
Clearly, in the setting of continued clinical symptoms and negative radiographic findings, MR imaging not only can exclude scaphoid fractures if not present but also can elucidate other causes for pain. Bretlau et al. [17] found that MR imaging also revealed a fracture of the capitate bone in one patient, a fracture of the triquetrum in two patients, and a bone bruise of one or more of the carpal bones in eight patients. Lepisto et al. [18] found MR imaging showed a wide spectrum of additional lesions in the wrist that were not detected by routine radiographic analysis. These lesions included seven fragmented triangular fibrocartilages, four torn scapholunate ligaments, and one torn triquetral lunate ligament. Bone bruises of other carpal bones and seven other carpal fractures were also detected. Cook et al. [16] found seven patients with evidence of extensor tenosynovitis on MR imaging. Thorpe et al. [15] found frequent occurrences of ligamentous injury and carpal instability at MR imaging that were not evident on scintigraphy.
A further advantage of MR imaging is the ability to image through casting material. This need occurs frequently when imaging takes place after the patient's initial presentation. Imaging through casting material requires a larger coil than the wrist coil (usually a flex or knee coil), resulting in a diminished signal-to-noise ratio. Although not esthetically as pleasing, the images are diagnostic in our experience (Fig. 3A,3B,3C). Fast short tau inversion recovery images may be substituted for fast spin-echo images with fat saturation if necessary.
Cost and practicality naturally preclude the use of MR imaging as a first-line diagnostic study; however, the limited wrist protocol we have described that is now being used at our institution brings costs in line with the costs of bone scanning and the traditional first follow-up appointment (Tables 3 and 4). Additionally, this limited MR imaging can be performed in less than 30 min (including setup; 10 min of actual scanning time), which allows flexibility for same-day imaging in our institution. We have found increasing acceptance among the emergency department physicians, which is similar to our experience with MR imaging for occult hip fractures. We conclude that this limited wrist MR imaging protocol (in the setting of suspected scaphoid fracture and negative initial radiographic findings) is nearly as cost-effective as traditional follow-up and immobilization.
Assuming the current standard of care (watchful immobilization) is applied,
most patients with positive findings at clinical examination and negative
radiographic results (
75% by our review) will undergo needless casting
(and possibly recasting), which compromises both lifestyle and productivity.
Follow-up appointments additionally result in lost wage-earning hours (often a
full day) or increased day-care expenses.
When lost productivity and income to the patient are considered, screening MR imaging is favored at initial presentation. This practice has always been the case for the elite athlete, as in case scenario 4. The presence of multiple scanners and technologists make possible the rapid scheduling of this 30-min (or less) procedure. In the outpatient setting, performing MR imaging in the same day may be slightly more difficult. As two of our case scenarios showed, a savings of time and money is possible even if the MR imaging is performed before the first orthopedic appointment.
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