Grip it Good

For my BME design capstone project, my team is working on designing a novel way to detect the grip force of patients in occupational therapy. We decided to select common, every-day objects and embed them with force sensors. This would increase the functionality and association of the measured grip force to the task being performed.

Problem

Current methods of measuring impaired grip strength and coordination do not correlate with the ability to perform functional tasks. For example, the grip force measured with a hand-held dynamometer is not representative of one’s ability to perform functional daily tasks. Other existing methods to measure grip force including pressure sensors, goniometers, sensor gloves, electromyography,and 3-dimensional imaging technology also lack correlation with functionality.

Assessment Requirements

Testing by Geometry

It may be of interest to measure the range of joint angles that patients are capable of achieving over their course of treatment. Increased range of motion may be a significant indicator of treatment efficacy.

Testing by Force

We have previously described loss of grip force as a potential consequence of morbidities that patients may encounter. Whether this reduction in strength is due to neurological impairment, nerve injury, muscle injury, tendon injury, carpal tunnel syndrome, or arthritis, we hypothesize that ability to measure grip force will be an essential for assessing efficacy of patient rehabilitation.

Testing by Competency

Since the ultimate goal of treatment is to help patients increase functional independence, another possible method of interest would be to create a set of functional tests requiring a representative dexterity and force needed to perform usual daily activities. Measuring patients’ ability to perform functional tasks may be a more sensitive indicator than generic tests which only measure grip strength and not manner in which the force is utilized.

Criteria

  1. Location: Device is usable at homes and in clinics/hospitals.
  2. Efficacy: Device measurements of grip force correlate to patient’s ability to perform functional tasks.
  3. Value: Device life span must be competitive to similar medical devices. Implementation of the device should be as minimally complicated as possible. Addition of diagnostic capabilities should be modular.
  4. Comparative pricing: The cost should be comparable to that of similar technologies, this includes both the cost of the device itself and all other relevant costs for treatment.
  5. Ease of use (for the patient): Under supervision of the physician/therapist, solution should allow patients of all backgrounds and ages to complete the diagnostic exercise.
  6. Perception to patients: Solution should enable patients to perceive the gripping task as they would perceive the functional gripping task in real life.
  7. Safety/complications: Diagnostic methodology should be safe and non-invasive at all points for the patient.
  8. Procedure Time: If procedure time for solution exceeds that of current devices, the additional time should be as insignificant as possible.
  9. Sensation: Tactile effects should interfere as little as possible with user grip force or familiarity with the gripped object.
  10. Integration into current practices: Solution should be usable while presenting minimal disruption to current procedure/protocol used by researchers and clinicians.

Stakeholders

Primary Benefits

Primary Costs

Assessment of Net Impact

Patients

The device will help physicians improve the treatment

May increase cost of treatment. Could require a more in-depth assessment

Positive: Improved efficacy of the treatment

Researchers

New, more precise methods to perform various tests. Can help to improve existing and create new rehabilitation methods

Need to determine the applicability / translation to rehabilitation methods. May have to adapt existing measures to accommodate different results

Positive: Will allow researchers to develop better rehabilitation methods that correspond to functional recovery

Occupational Therapists

Better assessments of patient health. Can better assign rehabilitation treatments to patients

Need to learn how to use new implements. Will have to include it in their current practice

Positive: Improved efficacy of the treatment

Funding Sources

Improves quality of care for patients

Need to pay for new assessment devices

Negative: Assessments will be more expensive. New devices will have to be purchased in order to perform these assessments

Institutions / Facilities

Expansion of more effective treatments to patients who could benefit from it

Increased costs for new devices. Need to train therapists on how to use devices

Positive: More accurate results will allow for better treatments that can improve the reputation of the hospital.

Manufacturers

Increased demand for devices

Will need to create more complicated devices as compared to existing dynamometers / pinch gauges

Negative: The more complicated nature of the device will increase the costs of the device and manufacturing

Brainstorming

  • Rehabilitation Bop-it
  • The Grip Ring
  • The NATE

Concept

Form Factor and Appearance

The Suitcase consists of several objects, representative of objects encountered in daily life, each designed to test a specific type of grip, including cylindrical, spherical, hook, pinch, and lumbrical grips. Each object is to be made from a uniform material, such as metal or plastic, with embedded force sensors exposed on its surface. The sensors will cover the intended surface area which patients will grip. In this manner, an evaluator using this tool may obtain the gripping force of the patient as well as the distribution of force.

This is the example of the "can" object:

Intended Use for Patients

The shapes of the object will be reflective of the five different types of grip that evaluators may want to evaluate. We intend to create shapes that mimic the shape and feel of everyday objects. For example, the grip force measurement object for a cylindrical grip may have a similar shape, form factor, and color of a soda can, with force sensors around its outer surface. During testing, the patient will be asked to perform certain motions utilizing one of the objects, to test for his/her ability to perform similar tasks involving the same kind of grip force. In a test, the soda can-shaped object would be placed on a table while the patient, sitting in a chair in front of the object, would be asked to grasp it, retrieve it, and deliver it to himself as if he were to drink soda from a can.

Data Acquisition

While the test object is being handled by the patient, the embedded sensors will continuously register the force that is being applied. This data will be sent to a computer either via a cable or wirelessly, and then recorded and analyzed. During analysis, the data collected from all sensors on the surface of the test object can be used to create a two dimensional heat map of forces being applied to the surface of the object, both at specific times during the task or integrated over the entire time period. This data can then be compared to one that is pre-recorded by a healthy individual and be used to determine the efficacy of the patients rehabilitation.