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Purpose: Free and soft tissue transfers are an important part of military and civilian extremity reconstruction after trauma. However, most outcomes research is based on relatively small series because devastating soft tissue loss in civilian trauma is uncommon. From the last decade of war in Iraq and Afghanistan a substantial amount of data regarding flap based limb salvage exists. The purpose of this study is to determine whether there are any predictors of flap and limb salvage failure to help guide extremity reconstruction decision making.
Methods: This is a multi-institution retrospective review of patients treated with tissue transfer for extremity trauma at R Adams Cowley Shock Trauma Center (STC) and Walter Reed National Military Medical Center (WRNMMC) between 2005 and 2012.
Results: From 2005 to 2012, 610 tissue transfers were performed for extremity trauma, 359 at WRNMMC and 251 at STC. Half of these flaps were free tissue transfers. Patients were mostly male (91%) aged 15 to 81 years (mean 31, SD 12) with an injury severity score of 1 to 57 (mean 18, SD 10). Mechanism of injury (MOI) included blast injuries (n=270), blunt injuries (n=261), and penetrating injuries (n=30). Vascular injury proximal to the flap recipient site was present in 115 cases, and 436 had concomitant injuries to other extremities. Flap failure occurred in 56 flaps (10%) and failed limb salvage resulting in amputation occurred after 79 flaps (14%). Across institutions, flap failure and amputation had a collinear association with MOI. Using univariate analysis, there were no independent predictors of flap failure. Using multivariate analysis, there were also no independent predictors of flap failure.

Variable	Relative Risk	p-value	95% Confidence Interval
Baseline	1.00
Sex (female)	1.67	0.201	0.762-3.65
Age	1.01	0.636	0.981-1.03
MOI
Penetrating	1.18	0.756	0.422-3.27
Blunt	0.705	0.307	0.360-1.38
Injury severity score	0.997	0.873	0.967-1.03
Vascular injury	0.961	0.902	0.967-1.03
Transfer type (free)	0.780	0.334	0.471-1.29
Multiple extremities injured	1.01	0.976	0.514-1.99
Extremity injured (upper)	0.526	0.114	0.237-1.17

However, proximal vascular injury, free flaps, and flap failure were predictors of amputation.

Variable	Relative Risk	p-value	95% Confidence Interval
Baseline	1.00
Sex (female)	0.647	0.278	0.294-1.32
Age	1.01	0.444	0.990-1.02
MOI
Penetrating	1.42	0.237	0.793-2.54
Blunt	0.620	0.056	0.379-1.01
Injury severity score	0.996	0.747	0.974-1.02
Vascular injury	2.63	0.000	1.73-3.98
Transfer type (free)	1.64	0.012	1.11-2.42
Multiple extremities injured	1.32	0.251	0.821-2.13
Extremity injured (upper)	1.98	0.004	1.24-3.15

Conclusions: This is one of the largest series of flap based extremity reconstruction for trauma in the literature. Outcomes between military and civilian institutions are similar and can be compared across patient populations. While there were no independent predictors of flap failure, the presence of proximal vascular injury, use of a free flap, and flap failure were predictors of amputation. However, these variables also portend a greater need for amputation before attempted reconstruction. The decision to attempt limb salvage in a patient with vascular injury, no other coverage options but free flap, or previous flap failure should be carefully considered because the likelihood of late amputation is significantly higher.