Myth-Busting the Zone-of-Injury Concept: A Prospective Study on the Vascular Response to High-Energy Lower Extremity Trauma.

[BACKGROUND] Although the zone-of-injury concept is widely accepted, no histologic studies of vessel wall changes causing the phenomenon have been reported. In this prospective study, the vascular response to high-energy lower extremity trauma was investigated to evaluate the validity of the zone-of-injury concept.

[METHODS] The histologic appearance of arterial and venous walls in the zone of injury was studied in 19 patients (median age, 46 years; interquartile range, 29.5 to 62.5 years) who underwent osteosynthesis and free flap reconstruction after high-energy lower extremity open fracture. Vascular samples were harvested from the injured extremity, and control samples were harvested from the free flap donor site. Histologic and morphometric characteristics of the vessels were analyzed microscopically and using digital pathology QuPath software.

[RESULTS] Vascular samples were harvested on postinjury days 1 through 11. Intimal thickness was more than 3 times greater in arteries harvested from the zone of injury than in control samples ( P < 0.01), and the intima/media ratio was 2-fold that in control samples ( P = 0.01). Arterial intimal fibrosis was more evident in vessels harvested from the zone of injury ( P < 0.01), but medial fibrosis and medial thickness did not differ significantly between groups. Venous intimal thickening ( P < 0.01) and the intima/media ratio ( P = 0.02) were greater in samples from the zone of injury. Fibrosis-related changes did not differ between groups ( P = 0.45).

[CONCLUSIONS] These findings support the validity of the zone-of-injury concept by providing a novel histologic basis for this phenomenon. Intimal thickening and arterial intimal fibrosis are prominent histologic features of vessels affected by major lower extremity trauma.