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Zero Prior

The evidence,
unsponsored.

Independent evidence grades for orthopedic implant design. Every study scored on a transparent rubric. No manufacturer funding. No assumptions.

What an honest grade looks like
MODERATE · 79 Registry · n=5,494 · 15yr
Norwegian Arthroplasty Register: RSA Survivorship by Brand & Design
Massive sample, long follow-up, publicly funded — but measures revision only. No PROMs. No functional outcomes. Strong methodology, limited endpoint. That's a Moderate.
MODERATE · 74 RCT · n=50 · 12mo
SSC Repair in RSA: Double-Blinded, MCID-Applied, Registered
The best-designed RCT in the RSA implant literature. Double-blinded, registered, results interpreted against MCID. But n=50, 12 months, and three authors have device manufacturer ties.
LOW · 54 RCT · n=100 · 2yr
135° vs 155° NSA: The Most Important Question, Poorly Answered
Funded by Arthrex. Multiple authors hold IP royalties on study devices. 32% lost to follow-up. An RCT asking the right question — scored Low because of how it was executed and who paid for it.
Why this matters

Early scoring suggests that the most-debated design questions in reverse shoulder arthroplasty — lateralization strategy, neck-shaft angle, onlay vs inlay — may lack the High-quality evidence most people assume exists. Surgeons make implant decisions, and hospitals spend millions, based on evidence that may not warrant the confidence placed in it. Zero Prior makes that visible.

How We Grade

Each study is evaluated on its own terms — how much confidence can be placed in its findings based on how it was conducted and what it was designed to find. Five dimensions, scored on a 100-point scale.

D1: Design Authority
What can this study design establish? RCTs carry more causal authority than registries, which carry more than case series.
D2: Statistical Precision
Is the sample large enough to trust the estimate? More patients = narrower confidence intervals = more reliable conclusions.
D3: Outcome Completeness
Was follow-up adequate and were patients accounted for? Duration relative to the hypothesis, plus loss-to-follow-up.
D4: Methodological Execution
Was the study executed rigorously — assessed on its own terms? Each study type gets a design-specific rubric measuring what actually matters for that design.
D5: Independence
Is this free from commercial bias? Funding source, author conflicts of interest, and whether the conclusion matches the data. The dimension nobody else scores.

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No spam. Just a launch notification and occasional evidence updates.

KC

Built by a former USAF physical therapist and independent orthopedic device specialist who spent years on both sides of the evidence problem — watching surgeons make implant decisions with cherry-picked data, and watching reps present it without context.

Zero Prior is operated by Vetra Health Strategies LLC. No manufacturer funding. No editorial influence. Full conflict of interest disclosure published. The name comes from Bayesian statistics: a zero prior means starting with no assumptions.