The mangled extremity scores

Several limb salvage scoring systems have been devised to aid clinicians in the decision of when to attempt limb salvage or perform early amputation.

Ideally, a trauma limb-salvage index would be:

  • 100% sensitive (all amputated limbs with trauma limb-salvage scores at or above the threshold)

  • 100% specific (all salvaged limbs with scores below the threshold),

  • Perfect accuracy. A high specificity is important to ensure that only a small number of salvageable limbs are incorrectly assigned a score above the decision threshold. Sensitivity is also important, however, to guard against inappropriate delays in amputation when the limb is ultimately not salvageable.

Bosse et al in a prospective study of 556 limbs found  that all the above lower-extremity injury-severity scoring systems have limited usefulness and cannot be used as the sole criterion by which amputation decisions are made. Overall, the lower-extremity injury-severity scores lack sensitivity, although in some cases they were very specific. This might suggest that, while the indices are incapable of identifying patients who will eventually require an amputation, they might be useful as a screening test to support the entry of an extremity into the limb-salvage pathway.

The high specificity of the scores confirms that low scores could be used to predict limb-salvage potential. The converse, however, was not true. The low sensitivity of the indices failed to support the validity of the scores as predictors of amputation.

Scores at or above the amputation threshold should be used cautiously by a surgeon who must decide the fate of a lower extremity with a high-energy injury.

The MESS, NISSSA, and HFS-97 all heavily weigh the results of initial neurological examination, with the assumption that an acute sensory impairment correlates with diminished limb-salvage capacity and that the initial examination demonstrates the final deficit. However, ischemia, contusion, stretch, or compression can cause transient neurological injury. With use of the LSI, the neurological deficit is scored on the basis of anatomical nerve findings.

 

Predictive Salvage Index (PSI) - HOWE 1987

 

Combined orthopaedic and vascular injuries.

Intent to help prevent the attempted salvage of a doomed or useless limb.

Retrospective, 21 limbs, studied to determine which variables influenced salvage or loss.

A limb-salvage score was developed that weighted:

  • Level of the vascular injury

  • Degree of osseous injury

  • Degree of muscle injury

  • Warm ischemia time

Howe et al. reported a sensitivity of 78% and a specificity of 100%.

Bosse found the sensitivity and specificity of the PSI for the patients with an ischemic limb injury were 56% and 79% when immediate amputations were included in the analysis and 40% and 79% when immediate amputations were excluded. The performance was not improved when only open tibial fractures were considered.

 

Mangled Extremity Severity Score (MESS) Johansen 1990

 

Combined vascular and orthopaedic injuries.

Used to select lower-extremity injuries that warrant primary amputation.

Vascular injury was never clearly defined in the MESS scoring system, and the MESS score allows for evaluation of patients with normal perfusion. For this reason, the MESS has been widely referenced as the trauma limb-salvage index for lower-extremity trauma.

Four characteristics related to injury:

  • Injury severity (energy transfer)

  • Ischemia

  • Shock

  • Age.

Retrospective, study of 25 patients. The index was then validated in that same patient group and prospectively in an additional 26 limbs.

Johansen et al. concluded that a MESS score of 7 or more was 100% predictive of amputation.

Bosse et al in their prospective study found a sensitivity of the MESS was 46%, this increased to 72% if only the ischemic limbs were considered. No advantage was noted in the application of the MESS to any of the nonischemic-limb subgroups. The sensitivity decreased to 27% when the immediate amputations were excluded from the analysis. The sensitivity of the MESS in the cohort of the severely open tibial fractures was 45% overall but was only 22% when the immediate amputations were excluded. The area under the curve for the limbs with a type-IIIC tibial fracture indicated a poor discriminative ability of the index, regardless of whether the immediate amputations were included or excluded (0.62 and 0.68, respectively).

  • Generally, the MESS was highly specific, suggesting that it might be useful in predicting the limbs that should not undergo amputation. The low sensitivity, however, suggests that a large proportion of limbs eventually requiring amputation would be at risk for a delay in the procedure, and this delay might in turn be associated with complications.

Nerve Injury, Ischemia, Soft-Tissue Injury, Skeletal Injury, Shock, and Age of Patient Score (NISSSA) - McNamara 1994

 

The NISSSA added a nerve-injury component, giving the highest weight to the loss of plantar sensation, and divided tissue injury into soft and skeletal variables.

Retrospectively 26  limbs were scored with the MESS and NISSSA.

Compared with the MESS score, the NISSSA score was found to be more sensitive (81.8% compared with 63.6%) and more specific (92.3% compared with 69.2%). Both scores were reported to be highly accurate in predicting amputation.

Bosse prospective study was unable to confirm this. They found the NISSSA had a sensitivity of 33% when applied to all type-III tibial fractures and of 13% when immediate amputations were excluded. The performance did not improve when the type-IIIB and IIIC tibial fracture subgroups were analyzed separately.

 

Limb Salvage Index (LSI) -Russell 1991

 

Limb trauma associated with vascular injury.

Absolute indications for amputation included a score of 6 or more.

Retrospective analysis of 70 limbs. 26 had pulse deficits requiring revascularization.

Seven components related to injury:

  • Arterial

  • Nerve

  • Bone

  • Skin

  • Muscle

  • Deep venous injury

  • Warm ischemia time

A 100% correlation between the limb outcome and the threshold score was reported

Bosse prospective study did not confirm that finding, they found an over all sensitivity of 46 % and specificity of 97%.

When applied to ischaemic legs only the sensitivity increased to 83% with a specificity of 82%.

The LSI did, however, perform significantly better than the MESS and the PSI when the scoring systems were applied to all of the limbs in the study (p < 0.05), and it performed significantly better than did the MESS, PSI, NISSSA, and HFS-97 when only type-III tibial fractures were considered (p < 0.05). This difference might be related to the injury focus of the score, the anatomical evaluation of the nerve injury, and/or the weight assignment selected by Russell et al. for each component.

 

Hannover Fracture Scale (HFS) - 1993 original description

 

The recommended amputation thresholds have been refined by a continued reassessment strategy with use of multiple regression analysis and receiver operator characteristic curves.

Bosse et al prospective study were unable to confirm the Hanover groups findings Overall, the HFS-97 had a sensitivity of 37% (10% for type-IIIB fractures and 67% for type-IIIC fractures). The sensitivity decreased to 11% when the immediate amputations were excluded from the analysis. The HFS-97 did perform significantly better than the MESS and the NISSSA when only the type-IIIC fractures were considered (p < 0.05). The area under the receiver operating characteristic curves suggested that the HFS-97 is only moderately good at discriminating between limbs that will undergo amputation and those that will be salvaged. Their evaluation of the HFS-97 was limited, however, by the necessity of modifying the score to account for the clinical practice in the study institutions of not performing bacteriological studies of specimens from the initial wound.

Comparison studies

  MESS LSI PSI
Bonanni (n-58) 22%(sensitivity) 61%(sensitivity) 33% (sensitivity)
     
Durham (n-51) 79%(sensitivity) 83%(sensitivity) 96%(sensitivity)
83%(specificity) 83%(specificity) 50%(specificity)

Bosse  (n-556)

 (all limbs, subgroups analyzed in original paper)

0.46 (0.38-0.54) (sensitivity) 0.46 (0.38-0.54) (sensitivity) 0.46 (0.38-0.54) (sensitivity)
0.91 (0.88-0.94)(specificity) 0.97 (0.95-0.98) (specificity) 0.87 (0.83-0.90) (specificity)

 


Suedkamp NP, Barbey N, Veuskens A, Tempka A, Haas NP, Hoffmann R, Tscherne H. The incidence of osteitis in open fractures: an analysis of 948 open fractures (a review of the Hannover experience). J Orthop Trauma. 1993;7:473-82

Russell WL, Sailors DM, Whittle TB, Fisher DF Jr, Burns RP. Limb salvage versus traumatic amputation. A decision based on a seven-part predictive index. Ann Surg. 1991;213:473-81

McNamara MG, Heckman JD, Corley EG. Severe open fracture of the lower extremity: a retrospective evaluation of the Mangled Extremity Severity Score. J Orthop Trauma. 1994;8:81-7

Johansen K, Daines M, Howey T, Helfet D, Hansen ST Jr. Objective criteria accurately predict amputation following lower extremity trauma. J Trauma. 1990;30:568-73

Howe HR Jr, Poole GV, Hansen KJ, Clark T, Plonk GW, Koman LA, Pennell, TC. Salvage of lower extremities following combined orthopedic and vascular trauma. A predictive salvage index. Am Surg. 1987;53:205-8

Bosse MJ, MacKenzie EJ, Kellam JF, et al. A prospective evaluation of the clinical utility of lower extremity injury severity scores. J Bone Joint Surg Am. 2001; 83: 314


Last Updated 14/09/2004
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