Review Question - QID 211545

A patient with pain, limited function, and no radiographic evidence of healing 6 months after scaphoid fracture fixation may have a scaphoid non-union. To confirm the diagnosis, a CT scan along the scaphoid axis is the next best step in care.

A scaphoid fracture non-union is defined as a failure to achieve union 6 months after cast immobilization or operative fixation. The longer a non-union persists, the higher the likelihood that secondary issues may develop, including arthritis or carpal instability. Union rates following primary scaphoid fracture fixation are >90%. Though there is some conflicting data, generally operative fixation of scaphoid fractures yields similar union rates to non-operative management but with faster return to work and shorter time to union. A CT is considered the gold standard in the diagnosis of a scaphoid fracture non-union following fixation.

Yin et al. performed a systematic review and meta-analysis of the diagnosis of suspected scaphoid fractures using bone scintigraphy, MRI, and CT. They found that bone scintigraphy and MRI demonstrated equally high sensitivity and high diagnostic value for excluding scaphoid fractures, however MRI was more specific. They concluded that both CT and MRI had >90% sensitivity and specificity in the diagnosis of a suspected scaphoid fracture.

The same authors (Yin et al.) later performed a cost analysis on diagnostic strategies for suspected scaphoid fractures. They showed that the average cost per scaphoid fracture with immediate CT was $2,553 and MRI was $7,483. The authors concluded that immediate advanced imaging (CT or MRI) was the most cost-effective strategy for diagnosing suspected scaphoid fractures compared to delayed radiograph-based strategies.

Lutsky and Matzon reviewed the best course of action when a persistent fracture line is noted after scaphoid fixation. The authors highlighted that interpretation of healing on 12-week post-operative radiographs demonstrated poor interobserver reliability and reproducibility, but that interobserver agreement was substantially improved with the addition of a CT scan. The authors held that a lack of bridging trabeculae on CT scan at 6 months after screw fixation for a scaphoid fracture was diagnostic for non-union.

Figures A and B are the AP and lateral radiographs of a scaphoid fracture fixed with a headless compression screw. A fracture line is still evident.

Incorrect answers:
Answer 2: Persistent pain with wrist extension and axial load at 6 months post-operatively is concerning for non-union, which should be ruled out prior to further occupational therapy.
Answer 3: A non-contrast MRI is useful in the initial diagnosis of a suspected scaphoid fracture, but an MRI with contrast would not best demonstrate non-union.
Answer 4: Pulsed electromagnetic field application following scaphoid fracture fixation and subsequent non-union has demonstrated some evidence supporting its utility, however the diagnosis of non-union must made first.
Answer 5: CT is superior to radiographs in the assessment of scaphoid fracture non-unions following fixation.