Evaluation of Mangled Extremity Severity Score (MESS) as a Predictor of Lower Limb Amputation in Children with Trauma

It was with great interest that we read the article by Behdad et al on the use of the mangled extremity severity score (MESS) in children.[1] We take issue with the recommendations of that article and wish to highlight them here.

The authors describe their experience with 200 Grade 3B and 3C fractures over the course of 1 year. All primary amputations were excluded from analysis—meaning that all the amputations they present represented failures of attempted reconstruction. At a rate of 7.5% for amputations over 1 year, the level of reconstructive failure is extraordinarily high. It also precludes any examination of the utility of the MESS score in predicting the need for primary amputation when those children undergoing this procedure are not evaluated. No comment is made as to the use or efficacy of microvascular free tissue transfer in their institution.

The authors make the bold recommendation that in children, the threshold for primary amputation should be lowered to 6.5 from the adult score of 7. First, this is inappropriate for the MESS as it is scored in integers. On an individual basis, one can have a score of 6 or 7; lowering the amputation threshold by 0.5 will make no difference in decision making.[2] Second, the assertion that children benefit less from reconstruction is incorrect.

The point in the discussion that functional results can be unsatisfactory in children is not referenced, and has little basis in fact. While any procedure can have complications, injured children are more likely to have better results than their adult counterparts. Children have better results from nerve repair,[3] higher rates of fracture union, and lower rates of wound infection,[4] particularly with the advent of microsurgical salvage with free tissue transfer for soft tissue defects. They learn to make better use of injured limbs due to improved cortical plasticity.[5]

Having chosen the optimal MESS threshold after generation of receiver operating characteristic (ROC) curves, the authors quote a sensitivity of (1–0.467) or 53%. That is to say that only 53% of potentially salvageable limbs will have a trauma score of below the threshold. Using this figure as an absolute indication for amputation will result in an unacceptably high rate of unnecessary amputations.

In our study spanning 10 years of experience with severe lower extremity injuries in a level 1 trauma center,[6] we had a primary amputation rate of 8% and a secondary amputation rate of 0%. We analyzed the use of the MESS as well as the limb salvage index, predictive salvage index, nerve injury, ischemia, soft tissue injury, skeletal injury, shock and age system (NISSSA), and the Hanover Fracture Scale-98. Owing to poor positive predictive values, we could not recommend the use of any of these scores to guide decision making in children's limb injuries. In this regard, we were in agreement with the Lower Extremity Assessment Project conclusions regarding the use of these systems in adults.[7]

In short, the clinical outcomes presented in the article by Behdad et al are poorer than we would accept. The conclusions they draw and the recommendations they make seem inappropriate even when based on their own data. We believe using the MESS as an indication for amputation at any threshold in the pediatric population, let alone the lower threshold suggested by the authors, is inadvisable and potentially harmful.

• References

• 1 Behdad S, Rafiei MH, Taheri H , et al. Evaluation of mangled extremity severity score (MESS) as a predictor of lower limb amputation in children with trauma. Eur J Pediatr Surg 2012; 22 (6) 465-469
• 2 Johansen K, Daines M, Howey T, Helfet D, Hansen Jr ST. Objective criteria accurately predict amputation following lower extremity trauma. J Trauma 1990; 30 (5) 568-572 , discussion 572–573
• 3 Frykman GK. Peripheral nerve injuries in children. Orthop Clin North Am 1976; 7 (3) 701-716
• 4 Cullen MC, Roy DR, Crawford AH, Assenmacher J, Levy MS, Wen D. Open fracture of the tibia in children. J Bone Joint Surg Am 1996; 78 (7) 1039-1047
• 5 Pascual-Leone A, Freitas C, Oberman L , et al. Characterizing brain cortical plasticity and network dynamics across the age-span in health and disease with TMS-EEG and TMS-fMRI. Brain Topogr 2011; 24 (3–4) 302-315
• 6 Stewart DA, Coombs CJ, Graham HK. Application of lower extremity injury severity scores in children. J Child Orthop 2012; 6 (5) 427-431
• 7 Bosse MJ, MacKenzie EJ, Kellam JF , et al. A prospective evaluation of the clinical utility of the lower-extremity injury-severity scores. J Bone Joint Surg Am 2001; 83-A (1) 3-14