# NEXUS C-Spine Rule Calculator

> NEXUS C-Spine Rule Calculator is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Evaluates the five NEXUS low-risk criteria to determine whether cervical-spine imaging is indicated after blunt trauma in adults

## Facts

- Endpoint: GET https://api.magentlab.com/api/calc/nexus
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/nexus-c-spine-rule-calculator-a5c101ae
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_xShTGqRISMpGse795wQjb

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability nexus-c-spine-rule-calculator-a5c101ae
```

Example prompt: My blunt trauma patient has no posterior midline cervical tenderness, no focal neuro deficit, is alert and not intoxicated, but does have a distracting painful leg fracture — do they need a c-spine x-ray per the NEXUS rule?

## When to prefer this

Use this endpoint when you need to apply the validated Hoffman 2000 NEXUS criteria specifically for cervical spine imaging decisions in adult blunt trauma patients. Prefer this over the Canadian C-Spine Rule when the patient population matches the original NEXUS publication (e.g. any alertness level, any age adult). Do not use for chest imaging decisions, penetrating trauma, or pediatric patients.

## Known failure modes

- Missing any of the five required boolean query parameters returns a validation error
- Incorrect boolean types (e.g. strings instead of true/false) will cause schema rejection
- Result is rule-based only — does not account for Canadian C-Spine Rule or NEXUS chest criteria
- Not valid for pediatric patients or non-blunt trauma mechanisms

## How this service works

NEXUS C-spine rule (Hoffman 2000). The patient is NEXUS low-risk, and imaging is not indicated by this rule, only when all five hold: no posterior midline cervical-spine tenderness, no focal neurologic deficit, normal alertness, no intoxication, and no painful distracting injury. Any failed criterion means x-ray is indicated. Not a diagnosis, not the Canadian C-spine rule, and not NEXUS chest. Blunt-trauma adults as published. magent does not examine the patient.

## Output

A structured determination of whether the patient meets NEXUS low-risk criteria — specifically whether all five criteria hold (making imaging not indicated) or whether any criterion fails (making imaging indicated), along with the pass/fail status of each individual criterion.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "headers": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    },
    "queryParams": {
     "type": "object",
     "required": [
      "midline_cervical_tenderness",
      "focal_neuro_deficit",
      "normal_alertness",
      "intoxication",
      "distracting_injury"
     ],
     "properties": {
      "intoxication": {
       "type": "boolean",
       "description": "Intoxication. true means intoxicated and the low-risk criterion fails. true or false as assigned by the caller."
      },
      "normal_alertness": {
       "type": "boolean",
       "description": "Normal alertness. true means alertness is normal and the low-risk criterion holds; false is altered alertness and the criterion fails."
      },
      "distracting_injury": {
       "type": "boolean",
       "description": "Painful, distracting injury. true means a distracting injury is present and the low-risk criterion fails. true or false as assigned by the caller."
      },
      "focal_neuro_deficit": {
       "type": "boolean",
       "description": "Focal neurologic deficit. true means a deficit is present and the low-risk criterion fails. true or false as assigned by the caller."
      },
      "midline_cervical_tenderness": {
       "type": "boolean",
       "description": "Posterior midline cervical-spine tenderness. true means tenderness is present and the low-risk criterion fails. true or false as assigned by the caller."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "path": "/api/calc/nexus",
  "count": 2,
  "items": [
   {
    "formula": "nexus",
    "citation": {
     "id": "hoffman-2000",
     "doi": "10.1056/NEJM200007133430203",
     "title": "Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma",
     "source": "N Engl J Med. 2000;343(2):94-99",
     "authors": "Hoffman JR, Mower WR, Wolfson AB, Todd KH, Zucker MI; National Emergency X-Radiography Utilization Study Group"
    },
    "criteria": [
     {
      "met": true,
      "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"
     }
    ],
    "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.",
    "nexus_low_risk": true,
    "xray_indicated": false,
    "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"
   },
   {
    "formula": "nexus",
    "citation": {
     "id": "hoffman-2000",
     "doi": "10.1056/NEJM200007133430203",
     "title": "Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma",
     "source": "N Engl J Med. 2000;343(2):94-99",
     "authors": "Hoffman JR, Mower WR, Wolfson AB, Todd KH, Zucker MI; National Emergency X-Radiography Utilization Study Group"
    },
    "criteria": [
     {
      "met": true,
      "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"
     }
    ],
    "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.",
    "nexus_low_risk": true,
    "xray_indicated": false,
    "formula_expression": "NEXUS
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/nexus-c-spine-rule-calculator-a5c101ae/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.magentlab.com](https://www.zero.xyz/host/api.magentlab.com/llms.txt)