FDA: O.N. Diagnostics shipped a new spine-fracture AI model without re-clearance

O.N. Diagnostics of Berkeley, California makes VirtuOst and VirtuOst VFA, software that analyzes CT spine images to visualize and measure vertebral deformities, classify fractures, and identify patients at high risk of osteoporosis-related fractures. The VFA version was cleared under K171435 with those indications. During a March 12–17, 2026 inspection, FDA found the current product no longer matched that clearance.

The firm's Software Version Control Log and '3.0.0 Release Notes' dated June 11, 2024 showed a new machine-learning algorithm had been introduced for vertebral landmarking. FDA's letter argued that 'a new model trained on different data, with different architecture, or optimized for a different objective may perform differently across patient populations, imaging equipment types, or clinical settings', and that the feature 'fundamentally changes how the device performs, fails, and affects patients'.

Inadequate validation, FDA wrote, could leave the device unable to perform as expected, risking missed or delayed fracture diagnosis and incorrect patient management. Shipping the change required a new premarket notification under 510(k); none was submitted, making VirtuOst VFA 3.0.0 adulterated and misbranded. FDA's warning letter of September 1, 2026 (CMS 730301) to CEO Shui Wong orders a comprehensive response and warns that failure could bring seizure and injunction without further notice.

VirtuOst VFA 3.0.0 deemed adulterated (no approved PMA/IDE) and misbranded; a warning letter demanding action, with seizure and injunction threatened.

The release notes themselves gave FDA the evidence: a version control log dated the model change.

FDA's reasoning is distributional: a model trained differently may fail differently across patient populations and scanners.

The harms are clinical: missed or inadequate diagnosis, delayed results, and mismanaged osteoporosis care.

The change shipped without validation evidence or a new premarket notification.

In regulated software, a model swap is a device change: retrain on new data with a new architecture and you have a new product in the regulator's eyes.

FDA directed responses to CDRH enforcement staff and noted the violations may be symptomatic of serious problems in the firm's manufacturing and quality management systems, telling the firm to investigate root causes. No fine has been imposed; the letter is the enforcement step so far.