# NEXUS C-spine NEXUS C-spine Status: LIVE Price: $0.005 USDC `GET /api/calc/nexus` HTML: https://magentlab.com/docs/nexus Markdown: https://magentlab.com/docs/nexus.md Not a medical device. Not a diagnosis, dose, or listing recommendation. ## What it computes Apply the Hoffman 2000 NEXUS C-spine rule and return whether the five low-risk criteria all hold (imaging not indicated by this rule). ## When to use When an agent has caller-assigned findings after blunt trauma and needs the published NEXUS C-spine imaging rule, not the Canadian C-spine rule. ## When not to use - Not a diagnosis. magent does not examine the cervical spine. - This tool is the Hoffman 2000 NEXUS C-spine rule only. It is not the Canadian C-spine rule and not NEXUS chest or NEXUS head CT. - Blunt-trauma adults as published. magent does not take age; the caller assigns the five findings. - Does not replace imaging when any criterion fails. ## Formula ``` NEXUS low-risk iff no posterior midline cervical-spine tenderness and no focal neurologic deficit and normal alertness and no intoxication and no painful distracting injury ``` ## Citation [Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma](https://doi.org/10.1056/NEJM200007133430203) Hoffman JR, Mower WR, Wolfson AB, Todd KH, Zucker MI; National Emergency X-Radiography Utilization Study Group N Engl J Med. 2000;343(2):94-99 DOI: [10.1056/NEJM200007133430203](https://doi.org/10.1056/NEJM200007133430203) ## Worked example ### All five low-risk criteria hold Given: `distracting_injury=false, focal_neuro_deficit=false, intoxication=false, midline_cervical_tenderness=false, normal_alertness=true` 1. No midline tenderness, no focal deficit, normal alertness, no intoxication, no distracting injury 2. NEXUS low-risk; imaging is not indicated by this rule ### Midline tenderness alone fails the rule Given: `distracting_injury=false, focal_neuro_deficit=false, intoxication=false, midline_cervical_tenderness=true, normal_alertness=true` 1. Posterior midline cervical-spine tenderness is present 2. The low-risk criterion fails; imaging is indicated by this rule ## Also searched as - NEXUS C-spine - NEXUS criteria - Hoffman NEXUS - cervical spine imaging rule - NEXUS low-risk criteria - National Emergency X-Radiography Utilization Study - C-spine clearance rule - NEXUS five criteria ## Parameters - `midline_cervical_tenderness` (boolean, required): Posterior midline cervical-spine tenderness. true means tenderness is present and the low-risk criterion fails. true or false as assigned by the caller. - `focal_neuro_deficit` (boolean, required): Focal neurologic deficit. true means a deficit is present and the low-risk criterion fails. true or false as assigned by the caller. - `normal_alertness` (boolean, required): Normal alertness. true means alertness is normal and the low-risk criterion holds; false is altered alertness and the criterion fails. - `intoxication` (boolean, required): Intoxication. true means intoxicated and the low-risk criterion fails. true or false as assigned by the caller. - `distracting_injury` (boolean, required): Painful, distracting injury. true means a distracting injury is present and the low-risk criterion fails. true or false as assigned by the caller. ## Bulk (POST) POST the same path with a JSON items array. Price is n times the GET unit. Invalid items return HTTP 400 before settlement. Method: `POST /api/calc/nexus` Max items: 25 Price: unit_amount * n (unit 5000 atomic) Status: PREVIEW - 1 to 25 items. Each item uses the same keys as the GET query parameters. - The first invalid item fails the whole request (index in the 400 JSON). You are not charged. - HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row. - Catalog misses (empty matches, found=false) stay paid 200s inside that slot. - x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items. Example request: ```json { "items": [ { "distracting_injury": "false", "focal_neuro_deficit": "false", "intoxication": "false", "midline_cervical_tenderness": "false", "normal_alertness": "true" }, { "distracting_injury": "false", "focal_neuro_deficit": "false", "intoxication": "false", "midline_cervical_tenderness": "false", "normal_alertness": "true" } ] } ``` Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/nexus Example 200: ```json { "count": 2, "path": "/api/calc/nexus", "items": [ { "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.", "citation": { "authors": "Hoffman JR, Mower WR, Wolfson AB, Todd KH, Zucker MI; National Emergency X-Radiography Utilization Study Group", "doi": "10.1056/NEJM200007133430203", "id": "hoffman-2000", "source": "N Engl J Med. 2000;343(2):94-99", "title": "Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma" }, "formula": "nexus", "formula_expression": "NEXUS low-risk iff no posterior midline cervical-spine tenderness and no focal neurologic deficit and normal alertness and no intoxication and no painful distracting injury", "criteria": [ { "factor": "no_midline_cervical_tenderness", "met": true }, { "factor": "no_focal_neuro_deficit", "met": true }, { "factor": "normal_alertness", "met": true }, { "factor": "no_intoxication", "met": true }, { "factor": "no_distracting_injury", "met": true } ], "xray_indicated": false, "nexus_low_risk": true }, { "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.", "citation": { "authors": "Hoffman JR, Mower WR, Wolfson AB, Todd KH, Zucker MI; National Emergency X-Radiography Utilization Study Group", "doi": "10.1056/NEJM200007133430203", "id": "hoffman-2000", "source": "N Engl J Med. 2000;343(2):94-99", "title": "Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma" }, "formula": "nexus", "formula_expression": "NEXUS low-risk iff no posterior midline cervical-spine tenderness and no focal neurologic deficit and normal alertness and no intoxication and no painful distracting injury", "criteria": [ { "factor": "no_midline_cervical_tenderness", "met": true }, { "factor": "no_focal_neuro_deficit", "met": true }, { "factor": "normal_alertness", "met": true }, { "factor": "no_intoxication", "met": true }, { "factor": "no_distracting_injury", "met": true } ], "xray_indicated": false, "nexus_low_risk": true } ] } ``` ## Response fields - `formula` (string): nexus - `formula_expression` (string): Hoffman 2000 five low-risk criteria - `nexus_low_risk` (boolean): true only when all five low-risk criteria hold. Imaging is not indicated by this rule when true. Not a diagnosis. - `xray_indicated` (boolean): true when nexus_low_risk is false. Not a diagnosis of cervical-spine injury. - `criteria` (array): Per-factor rows with factor and met; met is true when that NEXUS low-risk item holds - `citation` (object): Hoffman 2000 N Engl J Med citation - `disclaimer` (string): Not-a-device notice ## Example JSON Frozen fixture. Not a live lookup. ```json { "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.", "citation": { "authors": "Hoffman JR, Mower WR, Wolfson AB, Todd KH, Zucker MI; National Emergency X-Radiography Utilization Study Group", "doi": "10.1056/NEJM200007133430203", "id": "hoffman-2000", "source": "N Engl J Med. 2000;343(2):94-99", "title": "Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma" }, "formula": "nexus", "formula_expression": "NEXUS low-risk iff no posterior midline cervical-spine tenderness and no focal neurologic deficit and normal alertness and no intoxication and no painful distracting injury", "criteria": [ { "factor": "no_midline_cervical_tenderness", "met": true }, { "factor": "no_focal_neuro_deficit", "met": true }, { "factor": "normal_alertness", "met": true }, { "factor": "no_intoxication", "met": true }, { "factor": "no_distracting_injury", "met": true } ], "xray_indicated": false, "nexus_low_risk": true } ``` ## Errors - HTTP 400 `invalid_flag`: boolean clinical flags must be true or false Returned before settlement; you are not charged. - HTTP 400 `invalid_items`: POST body must be a JSON object with only an items array Returned before settlement; you are not charged. - HTTP 400 `invalid_item_count`: items must be an array of 1 to 25 objects Returned before settlement; you are not charged. - HTTP 400 `invalid_item`: each items entry must be a JSON object Returned before settlement; you are not charged. Shared HTTP 402 and 503: https://magentlab.com/docs/payments ## Related tools - [Ottawa ankle rule](https://magentlab.com/docs/ottawa-ankle) — Apply the Stiell 1992 Ottawa ankle rule and return whether an ankle x-ray series is indicated from caller-assigned malleolar pain, malleolar bone tenderness, and inability to bear weight. ## Payment Required query parameters must be present and valid. Invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. - GET the tool with Accept: application/json (do not send Accept: text/html unless you want the human paywall). - HTTP 402 means you have not paid. Decode the base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote. - Sign EIP-3009 (scheme exact, assetTransferMethod eip3009) with validBefore = now + accepts[0].maxTimeoutSeconds (600 seconds). That window starts when you sign and must cover wallet confirmation plus CDP verify and settle. Magent retries transient facilitator 429/5xx before answering. Do not send upto or batch-settlement payloads; magent does not offer those schemes. - Retry the same URL with PAYMENT-SIGNATURE (base64 JSON echoing accepted, payload, and extensions when present). - Success is HTTP 200 JSON plus PAYMENT-RESPONSE. Settlement happens before the tool runs. HTTP 503 settlement_uncertain or settle_failed: retry the same PAYMENT-SIGNATURE. Mint a new nonce only after a new HTTP 402. - offered `exact` on eip155:8453: Fixed-price USDC on Base. The buyer authorizes the advertised amount (EIP-3009). magent settles before the tool runs (paymentFlow upfront). extra.assetTransferMethod=eip3009 extra.paymentFlow=upfront. - not offered `upto`: Not offered. Usage-based: buyer authorizes a ceiling, seller settles the actual amount after work. Reserved for a future metered tool. Not for current calculators or code search. - not offered `batch-settlement`: Not offered. Payment-channel vouchers claimed later in batches. Not the same as POST {items} bulk (that is still exact). Same-path POST {items} is still scheme exact: one EIP-3009 authorization for n times the GET unit. That is not x402 batch-settlement (payment channels / vouchers). Shared HTTP 402 and 503 table: https://magentlab.com/docs/payments Stdio MCP (one process per host): https://magentlab.com/docs/mcp ## Guarantees - Invalid query parameters return HTTP 400 before settlement. You are not charged. - Settlement finishes before the tool executes (paymentFlow upfront). Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE. - HTTP 402 is unpaid only. Do not sign a second authorization because of a 503. - Execution is timeout-bounded and concurrency-capped. - Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.