Determination of Safe Corridors for External Fixation Pin Insertion in the Distal Long Bones: An Ex Vivo Anatomical...

External skeletal fixation (ESF) is a versatile method for fracture management in neonatal calves but confers a significant risk of iatrogenic injury to vital structures. The aim of this ex vivo study was to systematically define safe, hazardous, and unsafe corridors for transcortical pin placement in the distal long bones (radius-ulna, tibia, metacarpus, and metatarsus) of Simmental calves to provide precise anatomical guidance. Six fresh Simmental calf cadavers without orthopaedic problems were included in the study. The forearm and hindlimb were disarticulated from the shoulder and hip joints, respectively. The radius-ulna, tibia, and metacarpal and metatarsal bones were dissected transversely from five anatomical levels. Safe, hazardous, and unsafe corridors were determined in each section. No safe corridor was found in the proximal metaphysis and proximal diaphysis of the radius-ulna. Safe corridors were found on the medial side of the radius-ulna, from the mid-diaphysis to the distal metaphysis. The metacarpal and metatarsal bones showed lateral and medial safe corridors. The tibia provided a continuous medial safe corridor. In conclusion, precise topographic mapping is vital for safe ESF. While anatomically safe corridors are the primary choice for ESF, hazardous corridors are viable alternatives if meticulously utilized. By contrast, unsafe corridors must be strictly avoided to prevent severe iatrogenic trauma.