Diagnosis of suspected scaphoid fracture can be difficult, with up to 25% of patients having no evidence of scaphoid fracture on plain radiograph.
Undiagnosed scaphoid fractures can lead to complications, suggesting a need for a more reliable early method of diagnosis when the patient presents in the emergency room with a suspected fracture.
A recent study in The Journal of Bone and Joint Surgery (British Volume) set out to determine whether early MRI is superior to bone scintigraphy for suspected scaphoid fractures.
The study was comprised of 100 consecutive patients seen in the emergency department (ED) over a 70-month period with suspected scaphoid fracture and no evidence of fracture on plain radiographs.
All patients had a physical examination and MRI of the hand and wrist within 24 hours after initial presentation to the ED. Bone scintigraphy of the hand and wrist was performed 3 to 5 days after injury. Patients were also examined at fixed intervals during 6-month follow-up.
If MRI and scintigraphy both showed a scaphoid fracture, that was taken as a final diagnosis of fracture.
If they disagreed, follow-up radiographs and examination were used to decide whether a scaphoid fracture was present.
If both were negative and clinical signs were negative at 2 weeks, the final diagnosis was no scaphoid fracture.
If symptoms persisted, the final diagnosis was considered to be scaphoid fracture.
Results of the Study:
There were 20 scaphoid fractures and 32 other fractures. Bone scintigraphy showed 28 scaphoid fractures and 40 other fractures. There were 8 false-positive studies, but no false-negative studies with respect to the scaphoid.
MRI showed 16 scaphoid fractures and 24 other fractures. All 16 scaphoid fractures were true positive, but there were 4 false-negative studies, 2 of which resulted in changes on the follow-up radiograph and 2 that did not. Soft tissue injury was seen in 3 patients on MRI.
Because the “cost” of a false-positive study is less than that of a false-negative study for patient outcomes, the authors concluded in this study that bone scintigraphy remains the investigation of choice in the diagnosis of clinically suspected scaphoid fractures where plain radiographs are normal, in that its sensitivity was 100% and superior to that of early MRI.
I enjoyed this paper in that it approached a clinical study with a well-planned experimental protocol, which resulted in an unanticipated outcome.
The authors did show that when comparing early MRI with 3-day to 5-day delayed scintigraphy for scaphoid fractures, there were false-negative studies for scaphoid fracture with MRI, and none with scintigraphy. They therefore favor scintigraphy.
However, it seems to me that the authors do not have sufficient information to fully make this claim at this time.
While it is true that bone scintigraphy at 3 to 5 days post-trauma results in fewer false-negative studies for scaphoid fracture than does early MRI performed on the day of presentation, we must still compare 3-day to 5-day delayed scintigraphy with 3-day to 5-day delayed MRI to determine which test is optimal for suspected scaphoid fractures.
It is still conceivable that delayed MRI will be superior to delayed scintigraphy (with reduced radiation). A general limitation of this paper is that it does not include representative images to support its conclusions.
Author: Lionel S. Zuckier, MD
Beeres FJP, Rhemrev SJ, et al. Early Magnetic Resonance Imaging Compared With Bone Scintigraphy in Suspected Scaphoid Fractures. J Bone Joint Surg Br; 2008; 90 (September): 1205-1209