Rainbone at Hack the Valley 11: We Built a 3D Bone Stress Test and Made the AI Prove Every Number

This is a submission for the MLH x DEV Writing Challenge

A bone can look fine on a grey 2-D CT slice and still be close to breaking. The people looking after an older woman in senior living rarely get a plain answer to "how strong is her bone?" until a fall gives them one.

At Hack the Valley 11, my team of four built Rainbone: a 3D stress test for bones, explained by AI agents. It takes a real research CT scan of a thighbone and solves it with finite-element physics. It shows in 3D where the femur carries the most strain, and then Gemini explains the result in plain words for the care team: nurses, CNAs, wellness directors, doctors and admin staff. We built it for PointClickCare's Catch It Early challenge.

Try it: rainbone.health. Press Enter the lab; the demo seat (Dr. Rowan, care team) needs no account.

Rainbone is a research prototype built on public, de-identified research data. It is not a medical device, and it never says whether or when a fracture will happen.

We found HFValid, a dataset from the University of Bologna. It covers 101 women aged 56 to 86, with a femur CT for each woman, the study authors' own fall-fracture model results and a record of who fractured over the following five years. The lab opens on subject Pat001: the complete right femur of a woman who was 78 at her scan.

I was a full-stack and AI engineer on the team and its #1 GitHub contributor. I spent most of my time on the AI layer, because in a clinical setting the hard part isn't the model. It's the boundary: what the model is allowed to say.

Our rule: code computes, and the model only puts the results into words.

Ask Rainbone is a chat drawer that answers questions about the case, the pages and the data, and it shows each step as it runs. The five stages run as a LangGraph StateGraph. Triage works by rules, or Gemini's native function calling picks the tools. Evidence calls read-only tools. The writer may only pick statements from a fixed, checked catalogue. A code critic can send the draft back for one rewrite. The audit stage writes a row to Tiger.

def compile_graph ( execution: Execution ): from langgraph.graph import END, START, StateGraph graph = StateGraph ( GraphState ) for name in STAGES: async def node ( state: GraphState, name = name ): return await execution. run_stage ( name ) graph. add_node ( name, node ) graph. add_edge ( START, " triage " ) graph. add_edge ( " triage ", " evidence " ) graph. add_edge ( " evidence ", " writer " ) graph. add_edge ( " writer ", " critic " ) graph. add_conditional_edges ( " critic ", lambda state: state [ " next_stage " ], { " writer ": " writer ", " audit ": " audit " }) graph. add_edge ( " audit ", END ) return graph. compile () Enter fullscreen mode Exit fullscreen mode We chose LangGraph over a single chain because the critic needs to send drafts back to the writer. An explicit state graph makes that loop, and the audit step after it, visible and testable. If the framework itself fails, a built-in runner carries on from the same stage without re-running finished ones.

We also red-teamed our own agent: 32 hostile questions to the live Ask Rainbone, scored by fixed rules. 30 passed, and the two misses are now fixed and pass live ( red-team report ).

Try it in 60 seconds at rainbone.health:

The full method and the maths are in our research paper: 69 numbered equations and the LangGraph state machine.

Live site · Demo video (2:39) · 1:59 highlights · Devpost · Research paper · Architecture · Business process flow

A 3D stress test for bones, explained by AI agents.

Built for PointClickCare's Catch It Early challenge at Hack the Valley 11: catch bone weakness early, so prevention can start before the fall.

Who it's for: the care team in nursing homes and senior living: nurses, CNAs, wellness directors, doctors and admin staff.

Rainbone combines CT-derived 3D models, physics simulations and checked AI to help the care team see bone weakness early, before a fall becomes an emergency.

Rainbone starts from real research CT scans of the thighbone, each with a recorded follow-up It shows, in 3D and in colour, where a real femur takes the most strain under load. Then Gemini explains in plain words, for the care team, how that femur compares with the published research cohort.…