Biomechanics of calcaneal fractures: a model for the motor vehicle.

Changes in legislation, availability of passive or active restraint systems, or both, together with increased public awareness for safety and the need for use of restraint, have shifted the spectrum of trauma in motor vehicle crashes from the head and torso to other regions. Lower extremity trauma in motor vehicle crashes continues to be a significant problem. The objective of this study was to investigate the biomechanics of the human foot and ankle complex under impact loading and replicate calcaneal fractures routinely seen in motor vehicle crashes. Twenty-two unembalmed cadaver lower extremity specimens were subjected to dynamic loads using a minisled pendulum device. Input and output forces and results of pathologic analysis were obtained using load cell data, radiographs obtained before and after testing, and gross dissection. The intraarticular fracture patterns produced were similar to those seen clinically and described in the literature. Maximum forces ranged from 3.6 to 11.4 kN for the fracture, and 0.5 to 7.3 kN for the nonfracture groups. Logistic regression analysis revealed a 50% probability of calcaneal fracture at 5.5 kN and a 25% probability at 4.0 kN. These studies will lead to an understanding of the tolerance of the lower extremity in sustaining calcaneal fractures under impact. Implications of the work are in the design of crash test dummies, data acquisition, and modifications in motor vehicle design and safety.

Migration of a K-wire from the distal radius to the heart.

K-wires and Steinmann pins are used to provide internal fixation for fractures or osteotomies. In some instances, removal of the implant is planned and the implant is left long to facilitate its removal. In other instances, implant removal is not planned and the implant is cut off at the level of the bone. Migration of these implants to solid organs or body cavities has been reported. Extravascular migration may occur along tissue planes assisted by muscle motion. Large vessel penetration can occur and has been reported with subsequent migration of the implant to the heart. This case report documents the loosening of a K-wire used in the distal radius to supplement the fixation of a complex intra-articular fracture, migration of the implant along tissue planes, penetration into a peripheral vein, and continued migration of the implant to the heart. There are multiple reports documenting wandering bullets, venous catheter tips, and invasive monitoring devices in the extremities. This is only the second case report that the authors are aware of that confirms migration of an implant from the distal extremity to the heart.