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Scaphoid AVN

An elderly lady with wrist pain and no history of significant trauma.



Scaphoid AVN Scaphoid AVN

Figure 1. T1 weighted image (A) demonstrates hypointense scaphoid (arrow). Proton density with fat saturation image (B) demonstrates heterogeneous scaphoid, which distal pole is relatively hyperintense. Slight widening of the scapholunate space and a small cortical step off (arrow) in the proximal cortex of the scaphoid are present.

Discussion.

Avascular necrosis of the scaphoid usually occurs after scaphoid fracture with reported frequency of 13% to 50% (1). The proximal pole of the scaphoid is commonly affected due to retrograde nature of blood flow through the scaphoid. Scaphoid fractures are usually seen in young healthy patients who present with history of fall.

Spontaneous osteonecrosis of scaphoid, sometimes referred to as Preiser disease, has been described in the literature (2, 3, 4). Questions remain whether "spontaneous" osteonecrosis is truly spontaneous, or whether this osteochondrosis is a result of repetitive trauma. For example, a case of jack hammer operator who developed AVN of the distal pole (3) has been reported. Patient's symptoms improved after he changed his occupation. It is also plausible that some patients who develop "spontaneous" osteonecrosis of scaphoid have history of trauma that they cannot recall.

Treatment options for avascular necrosis of scaphoid include bone grafting and scaphoid excision with intercarpal fusion. Residual vascularity and viability of the proximal pole are important factors in decision making for procedures that attempt to salvage the scaphoid.



In general, it is widely agreed that MRI is the most sensitive imaging test for detection of scaphoid AVN. Is intravenous contrast needed for the evaluation of scaphoid in the setting of suspected AVN? Sensitivity and specificity of MRI for presence or absence of osteonecrosis vary among different studies and have been evaluated in the context of administration and non administration of intravenous contrast (5, 6). Earlier studies (6) suggested that contrast may be necessary. The latest reports question that assumption (5, 7). One study (7) recently evaluated dynamic contrast enhanced MRI, an advanced procedure similar to breast MRI that generates enhancement curves in the area of interest. Presence or absence of scaphoid enhancement correlated poorly with viability and non-viability of scaphoid (7) in that study. Non contrast MRI of the wrist has been reported as an acceptable method of imaging of the scaphoid for the evaluation of AVN (5).

Summary.

MRI is a sensitive tool for detection of avascular necrosis of the scaphoid. Given potential side effects and the expense of administration of contrast material, non-contrast MRI of the wrist is an acceptable approach for the evaluation of suspected scaphoid AVN.

References.

1. Steinmann SP, Adams JE. Scaphoid fractures and nonunions: diagnosis and treatment. J Orthop Sci. 2006 Jul;11(4):424-31.

2. Allen PR. Idiopathic avascular necrosis of the scaphoid. A report of two cases. J Bone Joint Surg Br. 1983 May;65(3):333-5.

3. Garg B, Gupta H, Kotwal PP. Review. Nontraumatic osteonecrosis of the distal pole of the scaphoid. Indian J Orthop. 2011 Mar;45(2):185-7.

4. Lauder AJ, Trumble TE. Idiopathic avascular necrosis of the scaphoid: Preiser's disease. Hand Clin. 2006 Nov;22(4):475-84.

5. Fox MG, Gaskin CM, Chhabra AB, Anderson MW. Assessment of scaphoid viability with MRI: a reassessment of findings on unenhanced MR images. AJR Am J Roentgenol. 2010 Oct;195(4):W281-6.

6. Cerezal L, Abascal F, Canga A, Garcia-Valtuille R, Bustamante M, del Pinal F. Usefulness of gadolinium-enhanced MR imaging in the evaluation of the vascularity of scaphoid nonunions. AJR 2000; 174:141-149.

7. Donati OF, Zanetti M, Nagy L, Bode B, Schweizer A, Pfirrmann CW. Is dynamic gadolinium enhancement needed in MR imaging for the preoperative assessment of scaphoidal viability in patients with scaphoid nonunion? Radiology. 2011 Sep;260(3):808-16.