Sanofi ProjectConcept Ideation and Development Tuesday, April 3, 2012 Some Thoughts from Andrea
Common Causes of Limitations in the Use of the Hands: Age and Arthritis Loss of Strength and Dexterity in the Hands is Common, beginning at Age 50 – 59, and increasing in severity with more advanced age. With Age – Loss of strength in muscle tissue throughout body, including the hands. Prevalence of severe hand disability in the general population age 50 and older is 12%, with increased occurrence over the age of 70 and in the female gender. Arthritis – The leading cause of disability in the United States (Centers for Disease Control)
Age – Loss of Strength and Dexterity In Hand Weakness due to Age, the Lateral Pinch Grip weakens less than other pinch grips. Lateral Pinch Grip – Example: Grip Used when Grasping and Turning a Key. Design to accommodate the Lateral Pinch Grip by making a larger contact area for the fingers.
Osteoarthritis (OA) – caused by wear and tearleading to deterioration of cartilage in the jointsCommonly Affected by OA: Finger Joints Less Commonly •Distal Finger Joints Affected by OA: •Base of Thumb Middle Joints (Proximal Interphalangeal Joints) (35% of individuals with OA) Base of Fingers – (Matacarpophalangeal Joints) (15% of individuals with OA)
Osteoarthritis Friction (due to cartilage deterioration) results in: Pain Stiffness Swelling Reduced Range of Motion Pieces of Bone may break off and float within the joint and the joint lining (synovium) and cause further inflammation.
Rheumatoid Arthritis (RA) Unknown Cause - Autoimmune Disease Commonly Affects Wrist and Fingers Unlike OA, Finger Joints closest to the palm of the hand• Cartilage Deterioration (Metacarpophalangeal Joints) • Deformation of Joints are commonly affected. Phasic o Severity Up and Down Pain Inflammation Swelling Stiffness Reduced Range of Motion
Examples of Accommodations for OA & RA Distal Finger Joints are used in most Pinch and Precision Grips.o A small pinch or other precision grip will often cause pain in the distal finger joints with Osteoarthritis. Make grip larger or change type of grip. The Thumb is used in All Grip Types.o A too wide grip will often cause pain in an arthritic joint at the base of the thumb Maximum Grip Span for OA (Osteoarthritis) and RA (Rheumatoid Arthritis) of moderate severity is not more than 2.5 to 3 inches.
Accommodation Examples - Continued: Rheumatoid Arthritis – Joint Deformation o Joint Deformation affects the types of grips that can be made. Example of Accommodation: Instead of using a pinch grip, a person with deformed finger joints may have to instead use a lateral key pinch grip.
Lateral Key Pinch Gripie: Grip Used When Grasping and Turning a Key
Types of Hand Grasps There is no one standard classification of grasps. Names for specific grasps can vary. The following slides show examples of grasp classifications.
Napier (1956)Prehensile – Where an object is held by the hand Power Grasp – Where an object is held in the palm of the hand The forces of the thumb are opposed by the forces of the fingers Muscular force is often high in the power grasp Precision Grasp – Where an object is held between the opposing fingers and thumb Muscular force is usually more limited in the Precision grasp than in the Power GraspNon-Prehensile – No seizing – The hand or finger applies pressure to anobject
The following Three Slides10 hand grasps Classified by Karl Kroemer (1986) Coupling the Hand with the Handle
Prehensile Grasps Ayoub, MacKenaie, Deivanayagam, Smith, Kroemer, Napier, Ladsmeern Hand Grasp / Power Grasp Spherical Grasp – Spherical object in Hand ie: Door Knob, Baseball Cylindrical Grasp – Around circumference of a cylindrical object ie: Hammer Handle Disc Grasp – Used on a disc shaped object ie: Lid of Jar Hook Grasp – Handle is hooked by digits 2 – 5 ie: Carrying a Briefcase
Pinch Grasps (Smith, 1985) Pulp PinchPad of thumb opposes pad of another finger Pulp Pinch = Compression Example: Pulp Pinch 2 = Thumb Opposes Index finger For Small Contact Areas and High Precision Example: Threading a Needle
Tip Pinch – Tip of thumbopposes tip of another finger
Gripping Larger Contact Areas and Applying Greater Force Lateral Pinch (Key Pinch) – Thumb opposes the radial lateral aspect of the index finger in the clenched fist. Lateral Pinches Aid Rotation Chuck Pinch – similar to pulp and tip pinches except the thumb opposes both the index and middle finger simultaneously.
Pinch or Precision Grasps Tools that Require Precision Movements Surgical Instruments, Pens or Pencils Small Force Grip that Facilitates Precise Motions Fingers and Wrist Play a Prominent Role
Power Grasps Tools that Require More Muscular Force due to Use Weight Size Function Need Larger Surfaces for the Hand to Contact to Form More of a Power Grip
Ideas for a Better Grip Shape with Bulges and Indents for a better grip Avoid Cylindrical Grips Pinch Grips Provide Contact Surface Area that is as large as the entire surface of the pad of the thumb or fingertips to increase strength A Pinch Grip is Five Times More Stressful than a Power Grip (National Institute for Safety and Health) Power Grips Contact Surface Area large enough to allow contact with the entire palm of the hand
Better Grip Ideas continued: Eliminate Pressure Points - sharp edges and other surface features that will cause local tissue pressures. Padding can be added at Pressure Points of the palm and fingers Does the design work for left-handed people? Size and Shape Gripping Area to Allow Alternatives to the Standard Grip.
Texture or Non-Slip Materialcan be added to surfaces to minimize slippage.