Projections show that there is a growing elderly population and therefore it is expected that there will be an increasing number of falls that lead to hospitalization in the coming years. Consequently, it is extremely important that research be conducted to identify appropriate solutions associated with mobility issues (Stevens *et al*., 2009). With this in mind, many different walking aid devices have been developed and are frequently used to prevent falls. Some examples are wheelchairs, walkers, and canes. Although these devices do work to assist mobility, they come with many issues for the people who use them. Whenever possible, it is always better to use a walker or cane over a wheelchair, because wheelchairs can produce many health issues from the decreased usage of leg muscles to the dangers of sitting down onto and getting up from a movable chair. Conversely, canes should only be used by people who have only a slight lack of mobility, because the support provided by a cane is minimal (Stevens *et al*., 2009).

Walkers therefore tend to be the most popular and best option for people struggling with mobility, and the history of walking frames (Zimmer frames) has been well documented (Mulley, 1996). However, initial studies emphasized frame design with respect to gait and balance (Wilkin, 1996), but they also come with many negative side effects. One of the most significant problems associated with using a walker is the development of gait deformities that arise from the adjustments the person makes to their walking motion to accommodate the walker architecture and operation (Tamura *et al*., 2001). These gait maladjustments then become the root of many back issues that develop in the elderly. Primarily, this is because current walker designs encourage the user to lean forward onto the supports of the device, which results in an increased curvature of the spine; and ironically, it can then increase the chance of a fall because it relocates the user's center of gravity with respect to the base. Studies that are even more recent have focused on the effect that different walking aides have on the gait and mobility of the user, but did not address any effects associated with back pain or muscle strain. 

The work presented in this study used a finite element analysis to examine the strains experienced by the lower back when different walking frame designs are used. The initial work studied loads on the lower back when a standard walking frame is used, with and without wheels attached to the front two stanchions. These results were then compared to the loads experienced by the back when a new proposed frame design was used, where the new frame had a structure that allowed the user to have their body weight be transmitted to the frame via an under arm and hand support.

The frame portion of the model used actual dimensions and frame materials in the case of existing frames, while the dimensions and materials of the proposed frame where those that would let four different body heights use the device. In addition, each design included options that did and did not have front wheels. The body portion of the model consisted of a basic skeleton and the lower back muscles and tendons most commonly associated with back pain. Two skeletal dimensions were used along with two different body masses for each set of dimensions. This was done to cover a range of body morphologies from large males and one extreme to small females at the other. The muscles considered in where the extensor (erector spinae), flexor, and oblique muscles and their associated tendons.

The results showed that the new frame design reduced the strain experienced by the lower back muscles and the spinal column. However, to maintain stability the new frame design had to have a larger footprint therefore making it less easy to navigate in tight spaces.


Zimmer Frame Use and Back Strain Analysis Using a Finite Element Model

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

IMECE2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.