Abstract:
An ergonomic grip for an instrument or tool handle is provide which reduces upper extremity musculoskeletal disorder (MSDs) by increasing the grip cross-sectional area, reducing the grip force necessary to manipulate the instrument and increasing the grip comfort using an elastomeric gripping surface. Vibrations from the instrument or tool are reduced or eliminated to further reduce MSDs.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an apparatus for reducing musculoskeletal disorders, and, in particular, to a gripping system for small diameter tool handles which relates repetitive motion injuries. 
     Musculoskeletal Disorders (MSDs) are injuries and illnesses that affect muscles, nerves, tendons, ligaments and joints. Individuals suffering from MSDs may experience loss of strength for gripping, reduced range of motion, loss of muscle function and the inability to do everyday tasks. Some of the common MSDs affecting the hands and wrists include carpal tunnel syndrome (CTS), tendinitis, lateral epicondylitis, synovitis and de Quervain&#39;s tenosynovitis. CTS is the most common compression neuropathy of the upper extremity and is predominantly occupationally related when the work environment requires repetitive hand-intensive tasks such as in the dental hygiene profession, for example. CTS has been diagnosed in more than 10% of dental hygienists with up to 65% reporting pain in the hand and wrist. CTS is a nerve entrapment disorder that affects the median nerve as it passes through the region of the wrist known as the carpal tunnel. Symptoms of CTS include paresthesias, incoordination of the involved fingers, the relatively rapid onset of hand fatigue, and in severe cases, true hand weakness. Although symptom onset is generally insidious, it can be acute and precipitated by vigorous or prolonged hand use. Similarly, 9.2% of dentists have been diagnosed by a physician as having some type of repetitive motion disorder. 
     According to the Occupational Safety and Health Administration (OSHA), in 1996 U.S. workers experienced more than 647,000 lost work days due to work-related MSDs (WMSDs). WMSDs now account for 34 percent of all lost work day injuries and illnesses costing business $15 to $20 billion in workers&#39; compensation costs annually. 
     WMSDs occur where there is a mismatch between physical requirements of a job and the physical capacity of the worker. Prolonged exposure to ergonomic risk factors such as force, repetition, static postures, awkward postures and vibration particularly in combination or at high levels is likely to cause or contribute to an MSD. 
     Dental hygiene procedures, for example, frequently require dental hygienists to maintain pinch grasps on small diameter instruments and use repetitive motions with applied force for scaling and root planing. This leads to stress of the thumb joint, wrist and forearm tendons. 
     It is, therefore, the primary object of the present invention to provide an apparatus that decreases work-related musculoskeletal disorders of the upper extremities. 
     Another important object of the present invention is to provide an apparatus that decreases fatigue of nerves, muscles, tendons and joints of the upper extremities. 
     Still another important object of the present invention is to provide an apparatus as aforesaid, which decreases transfer of vibrations from ultrasonic equipment to the upper extremities. 
     Yet another important object of the present invention is to provide an apparatus as aforesaid, which encourages better posture. 
     A further important object of the present invention is to provide an apparatus as aforesaid that can be integrated into and used with existing equipment, instruments and tools. 
     Still another important object of the present invention is to provide an apparatus as aforesaid, which increases patient comfort during a dental hygiene procedure. 
     Yet another important object of the present invention is to provide an apparatus as aforesaid, which allows a dental hygienist the option of using a palm grasp instead of a pinch grasp. 
     Another important object of the present invention is to provide an apparatus as aforesaid, which increase the grip size of a tool or instrument to a natural grip size without compromising an operator&#39;s or technician&#39;s ability to maintain control of the tool or instrument while using fine motor skills. 
     Still a further object of the present invention is to provide an apparatus as aforesaid, which may be used in a plurality of cross-sectional sizes to vary the technician&#39;s grip size to reduce musculoskeletal disorders due to repetitive hand-intensive tasks. 
     These and other objects of the invention are achieved by a removeable replaceable handle grip for small diameter tools, instruments and equipment that consist of one or more compressible materials such as closed cell rubber with an outer diameter in the range of approximately 0.5 inch to 2.5 inches. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an illustration of a right hand holding a dental mirror using a modified pen or pinch grasp. 
     FIG. 2 is an illustration of the mirror in the dental hygienist&#39;s left hand retracting the patient&#39;s buccal muscosa and a probe in the dental hygienist&#39;s right hand probing a maxillary right posterior tooth. 
     FIG. 3 is a side elevational view of a dental curet illustrating the basic parts of a dental hand instrument. 
     FIG. 4 is a side elevational view of the instrument shown in FIG. 2 with an ergonomic handle of the present invention mounted thereon. 
     FIG. 5 is a side elevational view of a dental mirror with a first alternatinve embodiment of the ergonomic handle of FIG. 4 mounted thereon. 
     FIG. 6 is a cross-sectional view taken substantially along line  6 — 6  of FIG.  5 . 
     FIG. 7 is a side elevational view of a double-ended Gracey curet. 
     FIG. 8 is a side elevational view of the instrument shown in FIG. 7 with a second embodiment of the ergonomic handle of the present invention mounted thereon. 
     FIG. 9 is an end view of the ergonomic handle of FIG.  8 . 
     FIG. 10 is an end view of the ergonomic handle of FIG.  8 . 
     FIG. 11 is a cross-sectional view taken substantially along line  11 — 11  of FIG.  9 . 
     FIG. 12 is dual-layer embodiment of FIG.  11 . 
     FIG. 13 is tri-layer embodiment of FIG.  11 . 
    
    
     DETAILED DESCRIPTION 
     Referring more particularly to the drawings in FIGS. 1-2 the modified pen grip and use of a dental mirror  20  and a curet  22  are illustrated. A modified pen or pinch grip generally indicated by reference number  26  places stress on a technician&#39;s index finger and joints  28 , middle finger and joints  30  and thumb and joints  32 . Because of the relatively small diameter of instruments  20  and  22 , and the muscle and tendon force required to retract the patient&#39;s buccal mucosa  34  with the dental mirror  20 , a tremendous amount of pressure is transferred to the basal or carpometacarpal joint  36  of the thumb  32 . 
     The thumb  32  is considered to be the most important single digit in the hand. One pound of pinch force between the thumb  32  and index finger  28  will produce six to nine pounds of pressure at the basal joint  36  of the thumb  32 . Disruptions in the joint  36  surface or the support ligaments can lead to subluxation (slipping of the joint) as well as pain and swelling. 
     Because of the nature of clinical work places, dental hygienists are at risk of acquiring musculoskeletal disorders (MSD) resulting from the long-term effects of repetitive motion, exposure to vibration, and mechanical stress. These types of MSDs are generally referred to as cumulative trauma disorders (CTDs). MSDs affecting the upper extremities may be caused by grasping small diameter instruments for extended periods of time, having pain or compromised posture during patient care, and frequent exposure to handpiece or ultrasonic scaler vibration. Other factors that contribute to CTDs include the work load on small muscles, tendons and ligaments of the fingers, thumb and hand, and the flexion and extension positions of the wrist during repetitive scaling and polishing. 
     Generally all dental instruments and as shown in FIG. 3, dental curet  22  includes a handle  38 , a shank  40 , and a working end  42 . Instrument handles  38  are generally thin with a circular cross-section. Handles  38  may have slight modifications in shape and surface texture. The shank  40  of an instrument  22  is thinner than handle  38  and joins the working end  42  of instrument  22  to handle  38 . The length and shape of shank  40  varies depending on the type and purpose of the instrument. The design of working end  42  indicates the use of the instrument  22  and determines its classification. 
     Referring to FIGS. 4-6, ergonomic handle  44  includes an elongated body member  46 , a rounded or blunt end  48 , a tapered end portion  50  and an aperture  52  which is sized to accept and secure instrument handle  38 . Ergonomic handle  44  preferably has a cylindrical cross-sectional configuration. Typically the outer diameter of ergonomic handle  44  is approximately 0.5 inch to 1.5 inches with an inner diameter an aperture  52  of 0.125 inch to 1.0 inch depending on the diameter of the instrument handle  38 . The larger grip size allows the technician to use a natural grip with decreased pressure while using their fine motor skills to maintain control of the instrument  22 . Additionally, the technician may use a palm grip for retraction for example. 
     Tapered end portion  50  extends over a portion of shank  40  and provides better tactile control of instrument  22  by the technician. Tapered end portion  50  also provides increased comfort for the patient when undergoing procedures in which the shank  40  of instrument  22  comes into contact with the patient&#39;s mouth such as retracting the patient&#39;s buccal mucosa  34  with dental mirror  20  (see FIG.  2 ), due to the larger outer diameter of taper  50  and the softer material used for ergonomic handle  44 . 
     Ergonomic handle  44  may also include one or more formed grooves  54  in elongated member  46  to enhance gripping by allowing the technician to place his or her fingers in grooves  54 . 
     Referring to FIGS. 7-10, double-ended Gracey curet  56  includes an elongated handle  58  separating spaced-apart shanks  60  and  62  and working ends  64  and  66 . Because of the difficulty of sliding an ergonomic handle over either working end or shank, an alternate embodiment of ergonomic handle  68  may be used. Ergonomic handle  68  includes an elongated member  70  which is generally cylindrically shaped, a generally axially aligned aperture  72  extending along the longitudinal axis of elongated member  70  and a channel  74  extending generally radially from the outer surface of member  70  to aperture  72 . Channel  74  may be separated to allow insertion of handle  58  into aperture  72 . Aperture  72  may have a contact adhesive along its circumferential surface to securely hold handle  58  in place. 
     A cross-sectional view of ergonomic handle  68  along line  11 — 11  of FIG. 9 is shown in FIG. 11 with alternate embodiments shown in FIGS. 12 and 13. In the preferred embodiment, ergonomic handle  68  is formed from a single closed cell rubber or silicone material  76 . One such material is a neoprene closed cell rubber with a density of approximately 8-12 pounds/cubic foot, a compression deflection of 2-5 pounds/square inch, and a shore hardness value of approximately 25-45. Other rubbers such as polyethylene, ethylene propylene terpolymer (EPT), ethylene vinyl acetate (EVA) and nitvile (NBR) may be used. These rubbers are available from Rubatex Corporation, stock number R-421-N (neoprene). Generally the outer layer  76  is readily deformable. 
     In general, ergonomic handle  68  may be made from a material with a density in the range from 2 to 30 p.c.f, a compression deflection in the range from approximately 2 to 20 p.s.i. and a shore hardness value in the range of 20-80. Generally, the softer the material, the more comfortable the grip and the better the material absorbs vibrations. However, a material that is too soft does not provide the technician with sufficient tactile sensitivity to effectively use some instruments. 
     Referring to FIG. 12, a dual laminate ergonomic handle  68  is illustrated using a generally softer material  78  surrounding aperture  72 , which is secured to a relatively harder material  80  using a contact adhesive bond. Material  78  may consist of a rubber such as ETP with a density from 2-5 pcf (Rubatex stock number R-4911-T). Material  80  may consist of a firmer rubber neoprene with a density of 15-30 pcf (Rubatex stock number G-207-N). Using a dual laminate system high frequency vibrations from instruments such as ultrasonic cleaners may be significantly reduced by material  78  while material  80  provides the operator with a comfortable yet firm grip. Alternatively, ergonomic handle  68  may be formed in a flat sheet that may be wrapped around handle  58  to form elongated member  70 , and may be releaseably secured with a contact adhesive or with one or more bands. 
     Referring to FIG. 13, a tri-laminate ergonomic handle  68  is illustrated using a top later  78  of soft rubber such as EPT with a density of approximately 3 pcf, a middle layer  82  of a relatively firm rubber such as a neoprene with a density of 22-35, a compression deflection of 17-24 p.s.i. and a shore hardness of 70-85, and a third layer  84  of an intermediate firmness rubber such as nitrile with a density of 9-18 p.c.c. and a shore hardness of 40-60. A three layer system may be used to suppress a wide range of vibration frequencies. It should be understood that a plurality of layers may be used to tailor ergonomic handle  68  to a specific need. 
     In a dental office application, ergonomic handle  44  and  68  (FIGS. 4 and 8) may be made of a high-temperature silicone rubber or rubber laminate which is autoclaveable. A closed cell rubber with a finished surface may also be used to prevent biocontaminants from becoming trapped in the rubber cells. However, due to the intolerance of most rubbers such as neoprene to high temperatures used in autoclaves, ergonomic handles  44  and  68  may be disposable. 
     Although the present invention has been disclosed with reference to periodontal instruments, and periodontal procedures, it is understood that the ergonomic handle of the present invention may be adapted to any shaped tool or instrument handle. 
     It is to be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims and equivalents thereof.