Shoulder Savers Design Team

THE SHOULDER SAVER

2001 Senior Design Project
University of Idaho

Project Motivation

    A large percentage of adults injure their rotator cuffs. Tears in the rotator cuffs are caused by the humerous head lifting and the supraspinatus rubbing against the acromion during shoulder rotation. The supraspinatus is the muscle that goes under the AC joint and over the top of the humerus head.

The two methods of treatment are as follows:

1. Surgery - very expensive and results in six weeks of being immobile and ten weeks of physical

therapy.

2. Physical therapy - effective and saves risks and cost of surgery.

For physical therapy treatment, there are two primary methods of exercise both with significant drawbacks:

1. Rubber bands - cheap but ineffective because the user is not taken through the proper range of motion.
2. Rehabilitation equipment - expensive (cost up to $100,000) and inconvenient because the user must travel to clinic to use it.

Problem Statement

A large percentage of adults injure their rotator cuffs. Tears in the rotator cuffs are caused by the humorous head lifting and the supraspinatus rubbing against the acromion during shoulder rotation. The supraspinatus is the muscle that goes under the AC joint and over the top of the humerus head. The two methods of treatment for rotator cuff injuries are surgery and physical therapy. Surgery is expensive and results in six weeks of being immobile and ten weeks of physical therapy. Physical therapy is an effective treatment for rotator cuff tears and saves risks and cost of surgery. Physical therapy is important for recovering from shoulder injuries.

For physical therapy treatment, there are two primary methods of exercise both with significant drawbacks: rubber bands and rehabilitation equipment. Rubber bands are cheap but ineffective because the user is not taken through the proper range of motion. Rehabilitation equipment is expensive (cost up to $100,000) and inconvenient because the user must travel to the clinic to use. A middle ground needs to be reached between cost, convenience, and effectiveness.

Goal statement 

The goal of the shoulder savers is to produce a piece of equipment that will safely and correctly exercise the rotator cuff muscle while being inexpensive and portable. 

The main goal of the product being developed is to take the user through the correct range of motion. The device must work for both the right and left shoulders and provide a wide range of resistance from 0-90N-m. The resistance range for the device should vary from 0-90N-m torque resistance in internal rotation and 0-50N-m torque resistance in external rotation. The device must exercise the shoulder through the correct range of motion from 80° internal rotation to 60° external rotation. The plane of motion of the shoulder must be perpendicular to the humorous. The device must place the user in the correct position with the humorous abducted 20° from the neutral position with the elbow at 90° . The adjustability of the device should reach the 5^th percentile female to the 95^th percentile male in arm length and arm height.

The total manufacturing cost of the device should be under $100. Usability is an important aspect of the device. The target audience of the device is people over the age 40. The total weight must be less than 10 lbs. Setup and takedown of the device must be completed with one arm in two steps. The device should be made of common materials to make it economically feasible to produce. Because this device may be marketed in the future, it should be aesthetically pleasing. Any moving parts should be covered. Because this device may be used around children, the amount of small parts should be minimized and all sharp edges must be rounded. The device should be made of non-hazardous materials since people will use it. At least 90% of the device should be of recyclable materials.

Project Specifications

Musts: