No new approvals, withdrawals or safety communications affecting orthopaedic practice today.
A meta-analysis of 15 studies and 4,183 participants found lower serum vitamin D in people who sustained stress fractures than in controls, by a mean of 5.82 nmol/L. The association held in military personnel (-7.33) and in men (-9.14), and was not detected in athletes or in women.
The meta-regression is where it becomes interesting. Baseline vitamin D status explained more than half the heterogeneity between studies (R² 53.8%), and the association was present only where control participants were already vitamin D sufficient — there the difference was -13.53 nmol/L.
That is the opposite of the intuitive reading. In populations where controls are broadly deficient, low vitamin D does not distinguish those who fracture, because nearly everyone is low. The signal appears where deficiency is unusual — which is consistent with vitamin D mattering, and also with it acting as a marker of something else that differs in a mostly-sufficient population.
The study measures association, not the effect of supplementation. Supplementation trials for stress fracture prevention have been mixed, and nothing here changes that.
- No new approvals, recalls or safety communications for orthopaedics today
- Association absent in athletes and in women
- Present only where control populations were already vitamin D sufficient
- Baseline status explained over half the between-study heterogeneity
- Observational — this is not evidence that supplementation prevents fractures
The statistics, in plain English
A meta-regression R² of 53.8% means baseline vitamin D status accounts for over half the variation in results between studies — an unusually strong explanation for heterogeneity, and more informative than the pooled estimate it explains. When a moderator does that much work, the overall summary figure is close to meaningless and the subgroups are the finding.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for orthopaedics, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free