A pressure algometer apparatus (20,50). The pressure algometer apparatus (20) provides an all mechanical pressure algometer including a balloon-like bladder member (22) for positioning at an end of a user's finger. An air tight interior (44) of the balloon-like member (22) is interconnected by tubing (42) to a pressure gauge (40). The algometer apparatus (50) includes a handheld pressure transducer (52) electrically interconnected (53) to an amplifier meter arrangement (54).

BACKGROUND OF THE INVENTION 
The present invention relates to a pressure algometer apparatus, and more 
particularly, to a pressure algometer apparatus for diagnosis of muscle 
pain or tenderness when subjected to pressure. 
Myofascial pain and dysfunction is the most common disorder causing chronic 
head and neck pain. Traditionally, diagnosis and assessment of the 
severity of this disorder depends on the tenderness of myofascial tissue 
at specific locations, often referred to as trigger points, to manual 
palpation. Manual palpation is accomplished by using one's fingers to 
apply varying pressure against the trigger points and to observe patient 
response. However, this technique is often unreliable, due in part to the 
inability to accurately measure the variation in pressure applied at the 
trigger point. The present invention solves this and other problems 
associated with this diagnostic technique. 
U.S. Pat. No. 4,337,780 issued to Metrick shows that pressure sensing 
devices have been used to test muscle strength. The Metrick patent teaches 
the use of an air tight bag of any suitable configuration depending on the 
muscle whose strength is to be tested, which is interconnected by tubing 
to a pressure responsive device so as to form an air tight compartment. 
The pressure responsive device consists of any suitable device 
commercially available to measure air pressure, such as a 
sphygmonanometer. In use, the air tight bag is typically attached to the 
palm side surface of the distal end of the tester's index finger by an 
elastic band or the like and/or is attached to the back of the tester's 
hand. 
The Metrick invention is used to test muscle strength and not muscle pain 
threshold or tenderness. Muscle strength testing devices have long been 
used. In muscle strength testing, the force applied to the overall muscle 
is measured. The configuration and consistency of the device used to apply 
the force is not critical. Therefore, in addition to other differences, 
there is no teaching or suggestion in Metrick of a pressure sensitive 
device having a specific configuration and consistency for testing muscle 
trigger points. 
As indicated in a brochure entitled, "Pain and Soft Tissue Pathology 
Instruments", Pain Diagnostics and Thermography of Great Neck, N.Y. 
appears to be marketing what are referred to as pain and soft tissue 
pathology instruments. These instruments apparently utilize a structural 
column arrangement, possibly a spring biased plunger arrangement, which 
interconnects a probe end of the instrument to a pressure gauge. In use, 
the user places the probe end against the tissue to be tested and applies 
pressure by grasping the gauge housing and forcing the gauge housing 
toward the probe end, whereupon the pressure is indicated at the pressure 
gauge. The instrument does not include a pressure probe adapted for 
positioning at the end of a user's finger and, as a result, does not offer 
the small size and flexibility of a user's finger in getting at hard to 
reach places, such as the underside of one's jaw. The pressure gauge is 
also rigidly attached to the pressure probe which further reduces the 
flexibility of the instrument. 
The present invention solves many of the problems associated with existing 
algometer devices. 
SUMMARY OF THE INVENTION 
The present invention relates to a pressure algometer apparatus. The 
algometer apparatus includes pressure sensitive probe means for use in 
applying pressure to localized sites and for sensing the pressure applied 
to the localized sites. The pressure sensitive probe means includes hollow 
elastic housing means including surface means proximate a first end for 
receiving a distal end of a user's finger, the housing means including 
proximate a second end body tissue engaging surface means. Pressure 
responsive means is present for indicating pressure variations sensed by 
the pressure sensitive probe means. Interconnection means interconnects an 
interior of the elastic housing means to the pressure responsive means for 
providing air communication between the interior of the elastic housing 
means and the pressure responsive means. 
The present invention also relates to an embodiment of the pressure 
algometer apparatus which includes transducer means for providing an 
electrical output signal indicative of the pressure sensed. This pressure 
responsive means is electrically interconnected to the pressure sensitive 
probe means for receiving the electrical output signal from the pressure 
sensitive probe means. The pressure responsive means includes readout 
means for indicating the pressure sensed by the pressure sensitive means. 
Means is further provided for electrical interconnection of the pressure 
algometer apparatus to a source of electrical energy. 
The present invention further relates to a method for diagnosing muscle 
tissue pain and dysfunction. The method includes the steps of manually 
palpating muscle tissue trigger points using pressure sensitive means 
inserted over a user's finger and forming an air tight seal therewith, the 
pressure sensitive means being interconnected to, and in air communication 
with, pressure responsive means for indicating variations in pressure. The 
method includes a second step of observing the pressure indicated at the 
pressure responsive means and observing the patient's response to such 
pressure. 
In the preferred method, the patient will be asked to indicate when they 
first start feeling pain as opposed to pressure. The user will then 
gradually increase the amount of pressure applied until the patient 
indicates they feel pain as opposed to only pressure. The user will 
typically observe the patient for any outward signs of pain; e.g., flinch, 
expression, etc. 
In the first embodiment, the present invention provides an all mechanical 
pressure algometer apparatus which is easy to use and yet relatively 
accurate. In addition, the invention provides a pressure algometer 
apparatus which is relatively inexpensive. The pressure algometer 
apparatus will, therefore, be an efficient screening device for use in 
this field. This embodiment also has many other advantages. First, the 
shape and firmness of the pressure sensitive probe means of the pressure 
algometer is such that it effectively serves as an extension on one's 
finger. The relatively small size and flexibility of a user's finger also 
make the invention particularly useful for getting at hard to reach places 
such as the underside of one's jaw. Moreover, the pressure sensitive probe 
portion of the pressure algometer is deformable as to conform to the 
surface of the tissue being tested. The soft, deformable nature of the 
probe portion also reduces the likelihood that the probe portion itself 
will induce additional pain. Finally, the probe portion of the mechanical 
algometer is preferably covered by and retained at the distal end of the 
user's finger by a throw away retainer member such as a finger cot. This 
makes use of the pressure algometer of the present invention extremely 
sanitary. However, the numbers obtained through the mechanical algometer 
are expressed in pounds per square inch (PSI). Since these numbers are 
relative due to the variable geometry of the individual finger, absolute 
calibration is difficult. 
The second embodiment of the invention can be absolutely calibrated because 
it employs a tissue engaging surface of constant geometry and relies on an 
electronic transducer, as opposed to air or gas pressure. This version of 
the invention may be somewhat more expensive and due to its increased 
accuracy, will probably be used mostly in a clinic setting. In the 
embodiments of this invention wherein a portable battery supply is 
provided, the device will be readily portable. 
These and various other advantages and features of novelty which 
characterize the present invention are pointed out with particularity in 
the claims annexed hereto and forming a part hereof. However, for a better 
understanding of the invention, its advantages and objects attained by its 
use, reference should be had to the drawings, which form a further part 
hereof, and to the accompanying descriptive matter, in which there is 
illustrated and described a preferred embodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
Illustrated in FIGS. 1 through 3, is a first embodiment of an algometer 
apparatus, generally referred to by the reference numeral 20, in 
accordance with the principles of the present invention. In the embodiment 
shown, the algometer apparatus 20 includes a resilient deformable, 
one-piece, integrally molded, plastic bladder member which functions as a 
pressure sensitive probe member 22. The pressure sensitive probe member is 
deformable but maintains its shape when not under pressure. The probe 
member has a first end surface providing a muscle tissue engaging surface 
24 similar to a distal end of a user's finger and a second end surface 
providing a finger engaging surface 26 being configured and contoured for 
receiving a distal end surface 28 of a user's finger. In the embodiment 
shown, the surface 26 has a generally concave shape inversely similar to 
the distal end surface 28 of a user's finger for receiving the user's 
finger such that the user's finger uniformly abuts the surface 26 when 
pressure is applied. The balloon-like probe member 22 is configured to 
closely approximate and standardize the surface area, shape and firmness 
of a distal end portion of an index finger. The probe member 22 is 
interconnected to a 0 to 3 pound per square inch (PSI) low pressure 
diaphragm gauge by a length of vinyl tubing 42. As illustrated, the tubing 
42 is interconnected to an interior area (cavity) 44 of the probe member 
22 by a metal section of tubing 46. 
In use, the probe member 22 is preferably retained at the distal end 
portion 28 of the user's finger 30 by a flexible tubular piece of material 
32, such as a finger cot or the like, open at one end 34 for insertion of 
the user's finger 30 and closed at the other end 36. 
As illustrated by the arrows 48, when the distal end portion 28 of the 
user's finger 30 is forced against the end surface 26 of the probe member 
22, air, as generally illustrated by the arrows 48, is forced into the 
tubing 46 as the probe member 22 deforms and the interior area 44 
decreases. The pressure responsive, low pressure diaphragm gauge 40 then 
provides a readout of the pressure variations created in the interior area 
44 of the probe member 22. The probe member 22 is preferably configured 
such that the user's finger 30 does not hit the end surface 24 when 
pressure within normal operating ranges is applied. 
In the preferred embodiment, the probe member 22 is made by dipping an 
aluminum mold in Iasco Vinyl Dispersion Number 60 Plastisol. After curing, 
the mold is removed by cutting the bladder member 22, and then resealing 
with cyclohexanone solvent. 
In use, a user positions the probe member 22 at the distal end surface 28 
of the index finger 30 and then inserts the index finger 30 into the 
tubular material 32 so as to facilitate retention of the probe member 22 
proximate the distal end surface 28 of the index finger 30. A user then 
manually palpates muscle tissue trigger points using the probe member 22 
which functions as a pressure sensitive device. The user typically will 
proceed by applying sufficient pressure against a muscle trigger point by 
forcing the index finger 30 against the end surface 26 of the probe member 
22 such that the patient can sense the pressure but normally will not 
sense any pain. The user then gradually increases the amount of pressure 
applied until the patient reports feeling even the slightest pain. The 
user then observes the pressure readout indicated at the low pressure 
diaphragm gauge which serves as a pressure responsive device. This is then 
recorded as the pain threshold. If no pain threshold is illicited from the 
patient, the top end of the pressure gauge scale reading, roughly 1.0 
pounds per inch, is recorded. After a predetermined interval; e.g., 5 
seconds, the process might be repeated at the same trigger point. This 
process is repeated at other trigger points as desired. The same patient 
might then be so evaluated by a second user after a predetermined time; 
e.g., 5 minutes, so as to provide comparison results. It will be 
appreciated that the specific pressure utilized will vary. 
Typically, the readout obtained is expressed in PSI and is relative, since 
the variable geometry of the user's finger makes absolute calibration 
difficult. As previously discussed, however, the present invention is 
particularly useful for getting at hard to reach places and is relatively 
inexpensive and entirely mechanical, so as to serve as a good screening 
device for field use as well as in the hospital facility. It will be 
appreciated that the present invention has numerous applications other 
than diagnosis of muscle pain or tenderness; e.g., diagnosis of joint 
capsulization, tissue compliance, sports medicine applications, etc. 
Illustrated in FIGS. 4-7 is a second embodiment of an algometer apparatus, 
generally referred to by the reference numeral 50, in accordance with the 
principles of the present invention. The algometer apparatus 50 shown 
comprises a hand held pressure transducer device 52, supporting bridge 
electronics 49 for receiving electrical input signals from the hand held 
pressure transducer device 52, and an amplifier/meter circuitry 
arrangement 54 electrically interconnected to the bridge electronics 49 by 
a suitable electrical interconnection 53. The supporting bridge 
electronics 49 and the amplifier/meter circuitry 54 are disposed in a 
housing 55. The transducer 52 includes a stainless steel bar 56 mounted in 
a housing 51. A Kistler/Morse semiconductor strain gauge sensor cartridge 
58 is mounted on the stainless steel bar 56 by suitable fasteners such as 
threaded screws 47 so as to sense any deflections of the bar 56. The 
supporting bridge electronics 49 located in housing 55 are electrically 
interconnected to the strain gauge sensor cartridge 58 by an electrical 
cord 57. The two resistors of the semiconductor strain gauge sensor 
cartridge 58 and the two resistors of the supporting bridge electronics 49 
cooperate to provide a bridge function. The electrical interconnection 53 
is slidably interconnected to a ten turn (10t) trim resistor so as to 
enable balancing of the bridge when in a neutral or unstressed state. When 
the bar 56 is displaced from its neutral state, the bridge function will 
become unbalanced and a corresponding signal value will be sent to the 
amplifier/meter circuitry 54 which in turn will output a corresponding 
signal to the meter 70, causing movement of the meter's pointer. As 
illustrated in FIG. 5, the steel bar 56 is mounted in the housing 51 so as 
to be secured against movement at a first end 56a and yet have a free end 
56b. Interconnected to the steel bar 56 proximate the free end 56b is a 
plastic, lightweight, cylindrical probe member 59 oriented at 90.degree. 
with respect to the housing 51. The probe member 59 is preferably 
lightweight such that the algometer readout is not affected by orientation 
of the housing 51. The probe member 59 has a contoured, curved end surface 
60 for engaging the localized area of the patient being tested. The user 
grasps the housing 51 and forces the end surface 60 of the probe member 59 
against the muscle trigger point being tested. As the user applies force, 
the probe member 59 displaces the free end 56b of the steel rod 56. The 
semi-conductor strain gauge sensor 58 then senses this displacement and a 
corresponding signal is transmitted via the electrical cord 57 to the 
bridge electronics 49 and then to the amplifier/meter circuitry 54 
ultimately resulting in a corresponding readout at the meter 70. A stop or 
movement limiter 62 might be provided for limiting movement of the steel 
rod member 56. The sensitivity of the semiconductor sensor cartridge 58 is 
such that it can detect extremely small deflections of the stainless bar 
56 many times under the elastic limits of the stainless steel bar. The 
amplifier meter arrangement 54 includes a one-milliamper meter 70 as a 
pressure indicator device which is driven by an operational amplifier 72. 
Both the pressure transducer arrangement 52 and its supporting bridge 
electronics 49, as well as the amplifier/meter arrangement 54 are battery 
powered, making for a readily portable, easy to use pressure measuring 
device. Illustrated in FIG. 7, a dual battery arrangement 74 is used to 
power the amplifier/meter arrangement while a separate battery arrangement 
76 is used for the energy supply of the semiconductor sensor cartridge 58 
and its supporting bridge electronics 49. In the preferred embodiment, the 
batteries are also located in the housing 55. The housing 55 is shown 
further including an on/off switch 80, a meter zero control 82, a meter 
span control 84, and the meter 70. 
A miniature load cell might be used for the tranducer so as to provide a 
more linear output. However, it is anticipated that such an approach would 
result in a much greater cost. It will be appreciated that numerous types 
of strain gauge devices might be utilized in keeping with the principles 
of the invention. 
This embodiment can be absolutely calibrated because the probe member 59 
muscle tissue engaging surface is of substantially constant geometry. 
Moreover, it is electronic and relies on a transducer to sense the 
pressure applied. This embodiment, although somewhat more expensive, is 
more accurate and will probably be used mostly in a clinical setting. 
It is to be understood, however, that even though numerous characteristics 
and advantages of the invention have been set forth in the foregoing 
description, together with details of the structure and function of the 
invention, the disclosure is illustrative only and changes may be made in 
detail, especially in matters of shape, size and arrangement of parts, 
within the principles of the invention, to the full extent indicated by 
the broad general meaning of the terms in which the appended claims are 
expressed.