The development and application of ambulatory monitor for measuring weight-bearing during fracture healing

Abstract

The aim of this study was to measure the weight-bearing during healing in a series of patients with tibial fractures, and to examine how this changed with time post-fracture. Weight-bearing indicates the force through the leg as a percentage of the total body weight. An ambulatory monitoring system was developed, comprising of the monitor and analysis software for a PC. The ambulatory monitor measures the force via pressure transducers attached to the load bearing areas on the underside of the foot to obtain the weight-bearing through the fractured leg. The software was developed in the C programming language by using a PC host executing a cross-compiler, the program then being down-loaded via the serial line to the monitor hardware for execution and testing. Once a basic monitor was operational, the clinical trials commenced, these being conducted at fracture clinic sessions at Middlesbrough General Hospital. Further development work occurred throughout the patient trials which led to increases in the accuracy and consistency of the results obtained. Results were obtained from 37 patients with tibial fractures, and these all demonstrated that there was a non-linear increase in weight-bearing with time post-fracture. An increase in step duration relative to the step duration of the normal leg also occurred, indicating a gradual change in the gait pattern adopted, tending towards a normal gait pattern with time. A similar pattern was found with the stride length, this indicating a gradual change towards a more normal gait pattern with time. An increase in velocity of gait was also observed over the healing period, suggesting greater confidence in walking as healing progressed. Such results lead to the hypothesis that a feedback mechanism operates which controls the weight-bearing applied to the fracture depending on the stiffness of the fracture. The clinical relevance of this work is to aid the clinician in fracture healing assessment enabling the prescription of more applicable treatment methods