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NEXUS C-spine

Apply the Hoffman 2000 NEXUS C-spine rule and return whether the five low-risk criteria all hold (imaging not indicated by this rule).

LIVE $0.005 USDC GET /api/calc/nexus

Markdown: /docs/nexus.md · Canonical: https://magentlab.com/docs/nexus

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

Title

Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma

Authors

Hoffman JR, Mower WR, Wolfson AB, Todd KH, Zucker MI; National Emergency X-Radiography Utilization Study Group

Source

N Engl J Med. 2000;343(2):94-99

DOI

10.1056/NEJM200007133430203

Worked example

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

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/nexus?midline_cervical_tenderness=false&focal_neuro_deficit=false&normal_alertness=true&intoxication=false&distracting_injury=false

Full URL: https://api.magentlab.com/api/calc/nexus?midline_cervical_tenderness=false&focal_neuro_deficit=false&normal_alertness=true&intoxication=false&distracting_injury=false

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/nexus?midline_cervical_tenderness=false&focal_neuro_deficit=false&normal_alertness=true&intoxication=false&distracting_injury=false"

Parameters

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.

POST /api/calc/nexus Max 25 unit_amount * n 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 (fixture)

{
  "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"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "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

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "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
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

Related tools

• Ottawa ankle rule — 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. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /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.