Quantitative characterization of human performance during hip reduction

Abstract

Hip dislocations are rare events. As a consequence, medical residents have little opportunity to gain experience through repeated practice. In fact, little is known about the forces and displacements that experienced physicians employ during the procedure. This study seeks to quantify the strategic maneuvering and substantial force required to reposition the femoral head into the pelvis during a hip reduction, toward a long-term goal of building a high fidelity training simulator. In particular, the work herein describes the design, construction and evaluation of a custom-built, force and motion measurement system (FMMS). As a physician attempts to relocate the hip, the FMMS measures force about the patient's waist using a seatbelt and inline load cell (4448 N range) and displacement of the dislocated leg with four magnetic displacement sensors (each 6 DOF). Iterations of the system have been tested on cadavers and able-bodied participants, with the current system deployed for collection on hip reduction patients. The results preliminarily indicate that forces at the hip range from 56.8 to 110.8 N, the forces at the leg range from 254.5 to 496.6 N, and that maximum angular movements from the pelvis to the thigh, from the thigh to the knee, and from the knee to the ankle are 80.1, 31.5 and 20.7 degrees, respectively.