JSES - 2026-03-25 - Journal Article
Diagnostic Performance of a Gravity Varus Stress CT Protocol in Detecting Instability in Isolated Coronoid Fractures.
Badre A, Abdullah H Awad M, Chan R, Lapner M, Goetz T
Topics
Key Takeaway
Gravity varus stress CT reduced the false-negative rate for detecting instability in isolated coronoid fractures from 82% (static CT) to 11% (p<0.001).
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Summary
This two-center retrospective cohort compared gravity varus stress CT versus routine static CT for detecting instability in isolated coronoid fractures, using clinical exam or fluoroscopic EUA as the reference standard. Stress CT achieved a PPV of 96% and FNR of 11%, versus a PPV of 100% and FNR of 82% for static CT. The FNR difference was statistically significant (p<0.001), demonstrating that static CT misses instability in the majority of cases.
Key Limitation
Non-randomized group allocation means patients selected for stress CT may have had higher clinical suspicion for instability, potentially inflating the apparent superiority of the stress protocol.
Original Abstract
BACKGROUND
Instability associated with isolated coronoid fractures can be subtle and frequently missed on routine imaging. A stress-based CT protocol may improve detection of occult instability in isolated coronoid fractures. The purpose of this study was to evaluate the diagnostic performance of a gravity varus stress CT protocol in detecting instability in isolated coronoid fractures and compare it with routine static CT.
METHODS
A retrospective cohort study of patients with isolated coronoid fractures who underwent either gravity varus stress CT or routine static CT between 2019-2025 was performed at two academic centers. Instability was assessed via clinical examination or fluoroscopic examination under anesthesia (EUA). CT findings were correlated with the reference clinical examination or EUA to calculate positive predictive value (PPV) and false-negative rate (FNR). Fisher's exact test was used for between-group comparisons.
RESULTS
Eighty-four patients were included (41 stress CT, 43 static CT). Gravity varus stress CT demonstrated instability in 26/41 patients, with clinical or intraoperative instability confirmed in 28/41, yielding a PPV of 96% and FNR of 11%. Static CT demonstrated instability in 5/43 patients, while clinical or intraoperative assessment confirmed instability in 28/43, yielding a PPV of 100% and FNR of 82%. There was no difference in PPV (p = 1.00), but gravity varus stress CT had a significantly lower FNR than static CT (p < 0.001).
CONCLUSION
Routine static CT substantially underestimates instability in isolated coronoid fractures. Gravity varus stress CT provides a more accurate assessment, with markedly lower false-negative rates and excellent positive predictive value. Stress CT should be considered in the evaluation of isolated coronoid fractures without obvious history/imaging evidence of dislocation.