Clinical calculator
MESS Calculator
Mangled Extremity Severity Score
The Mangled Extremity Severity Score adds four components — skeletal and soft tissue injury, limb ischaemia (doubled if ischaemia exceeds six hours), shock and age — and a total of 7 or more was 100% predictive of amputation in the original series, a threshold that later prospective work found does not hold well enough to decide an individual case.
What the MESS score means
MESS scores run from 1 to 14, where a lower score is better. The bands below are conventional reporting categories, not diagnostic cut-offs.
- Below the historical amputation threshold1–6
In the 1990 derivation series every limb scoring below 7 was salvaged. Prospective validation has not reproduced that, and a score below 7 does not predict a good functional result — it only means the score is not arguing for amputation.
- At or above the historical amputation threshold7–14
A score of 7 or more was 100% predictive of amputation in the derivation series. Later prospective work found the threshold has poor sensitivity and should not be used on its own to decide on amputation in an individual patient.
Published criteria and reliability
The published cut-offs that define this instrument, and the measured agreement between observers using it. Each is reported with the population it was derived in.
| Type | Value | Subscale | Population | Follow-up | Source |
|---|---|---|---|---|---|
| Criterion | Total of 7 or more — 100% predictive of amputation in the derivation series | — | Retrospective and small prospective series of lower-limb trauma, Harborview Medical Center | — | Johansen K 1990 |
| Criterion | The ischaemia component is doubled where ischaemia has lasted more than six hours | — | Limb trauma with vascular compromise | — | Johansen K 1990 |
| Criterion | In prospective multicentre validation the MESS and the other limb-injury severity scores had low sensitivity for amputation and should not be the sole basis for the decision | — | Prospective cohort of severe lower-extremity injuries (LEAP study) | — | Bosse MJ 2001 |
| Criterion | Two-year functional outcomes were broadly equivalent after amputation and after reconstruction | — | Prospective cohort of severe lower-extremity injuries followed for two years (LEAP study) | — | Bosse MJ 2002 |
Criterion is a published cut-off, definition or performance figure belonging to a classification or decision rule — it is not a change score and should not be read as one.
How the score is calculated
Stated in full so the calculation can be independently checked, and reproduced by hand if needed.
Four components are added. Skeletal and soft tissue injury scores 1 for low energy, 2 for medium energy, 3 for high energy and 4 for very high energy with gross contamination or avulsion. Limb ischaemia scores 1 for a reduced pulse with normal perfusion, 2 for a pulseless limb with paraesthesia and diminished capillary refill, and 3 for a cool, paralysed, insensate limb — and these points are DOUBLED if the limb has been ischaemic for more than six hours, which is the only multiplied term in the score. Shock scores 0 if the systolic blood pressure has always been above 90 mmHg, 1 for transient hypotension and 2 for persistent hypotension. Age scores 0 under 30 years, 1 from 30 to 50 and 2 over 50. In the original retrospective series a total of 7 or more was 100% sensitive and specific for eventual amputation. That figure came from a small derivation cohort; subsequent prospective multicentre validation found the score had poor sensitivity for amputation, and that limbs scoring above the threshold were frequently salvaged. The score is therefore best used to describe injury severity and to structure a discussion, not to make the decision.
Missing data
All entries are required. Unanswered components contribute nothing, so an incomplete total is always an underestimate — and because the threshold points towards amputation, an underestimate is the safer direction to err but still not a usable number.
Instrument profile
- Developer
- Kaj Johansen, Matthew Daines, Thomas Howey, David Helfet and Sigvard T. Hansen Jr.
- Institution
- Harborview Medical Center, University of Washington, Seattle, United States
- First published
- 1990
- Items
- 5
- Response format
- Four scored components plus the ischaemia-duration modifier
- Score range
- 1 to 14
- Direction
- Lower score = better
- Completion time
- About 2 minutes
- Age range
- Adults
- Regions
- General Health
- Conditions
- Mangled extremity, Open tibial fracture, Limb-threatening vascular injury, Crush injury of the limb, Traumatic amputation
- Procedures
- Limb salvage, Amputation, Vascular repair of the lower limb, External fixation for open fracture
- Validity
- High specificity in the derivation series has not survived prospective testing. The strongest finding from the LEAP study is that the limb-injury severity scores, including this one, did not discriminate well enough to guide an individual amputation decision, and that plantar sensation — long treated as decisive — was itself a poor predictor of eventual outcome.
- Reliability
- Agreement is reasonable, since three of the four components are objective. The energy grading is the subjective one, and it carries up to 4 of the 14 points.
When to use the MESS
Well suited to
- Describing the severity of a mangled limb in a structured, comparable way in the trauma note and in research.
- Structuring the conversation with colleagues and with the patient about what makes this limb high risk — energy, perfusion, physiology and age.
- Retrospective case series and audit, where a standard severity measure is needed.
Limitations and poor fits
- Deciding to amputate. Prospective evidence does not support using the threshold to make that decision in an individual patient, and the consequence of being wrong is irreversible.
- Upper-limb injury, where the score was not derived and where the functional trade-offs are entirely different.
- Children, in whom the age component is meaningless and healing potential is not represented.
- As a substitute for serial reassessment. Perfusion, contamination and the patient’s physiology all change over the first hours, and so does the right answer.
MESS compared with other instruments
Instruments measuring a related construct, with the practical difference between them.
| Instrument | Items | Range | What it adds |
|---|---|---|---|
| Gustilo-Anderson | 4 | 1–5 | The Gustilo-Anderson classification grades open fractures from type I to type IIIC by wound size, degree of soft tissue damage, contamination and vascular injury, and it is the system that drives antibiotic choice, debridement planning and the decision on soft tissue coverage. |
| AO/OTA | 3 | 1–3 | The AO/OTA classification gives every fracture an alphanumeric code in which the first digit is the bone, the second the segment and the letter the fracture type — extra-articular, partial articular or complete articular in an end segment, and simple, wedge or multifragmentary in a shaft — so that 32-A is a simple femoral shaft fracture and 43-C a complete articular pilon fracture. |
| ASA | 2 | 1–6 | The ASA Physical Status Classification grades a patient’s pre-operative systemic health from I, a normal healthy patient, to VI, a declared brain-dead organ donor, with an E modifier added for emergency procedures. |
| CCI | 17 | 0–37 | The Charlson Comorbidity Index is a weighted checklist of 16 comorbid conditions that produces a comorbidity score of 0 to 33, to which up to 4 points are added for age, and which estimates 10-year survival at roughly 98% for a total of 0, 90% for 2, 53% for 4 and 21% for 5. |
Copyright and permitted use
Published openly because it is the question every clinician and researcher asks before using an instrument, and almost nobody answers it.
A published scoring system. No licence is required.
References
- Johansen K, Daines M, Howey T, Helfet D, Hansen ST Jr. Objective criteria accurately predict amputation following lower extremity trauma. Journal of Trauma. 1990.
- Bosse MJ, MacKenzie EJ, Kellam JF, et al.. A prospective evaluation of the clinical utility of the lower-extremity injury-severity scores. Journal of Bone and Joint Surgery (American Volume). 2001.
- Bosse MJ, MacKenzie EJ, Kellam JF, et al.. An analysis of outcomes of reconstruction or amputation after leg-threatening injuries. New England Journal of Medicine. 2002.
Editorial status
This page has not yet been signed off by a named clinical reviewer. The scoring logic is stated in full above so it can be independently verified, and every threshold is traceable to its source. See our editorial methodology.