Apparatus for assessing joint mobility

• US 4,444,205 A
• Filed: 05/27/1981
• Issued: 04/24/1984
• Est. Priority Date: 05/31/1980
• Status: Expired due to Fees

• Current Assignee: University of Strathclyde
• Original Assignee: University of Strathclyde
• Inventors: Jackson, John
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): Sykes, Angela D.
• Application Number:
  US06/267,471
• Time in Patent Office: 1,063 Days
• Field of Search: 128/782, 128/781, 128/779, 128/774, 128/639, 128/644, 128/721, 73/379, 73/381, 73/769, 73/787, 73/855, 33/174 D, 338/2, 338/5, 338/47, 338/114
• US Class Current: 600/595
• CPC Class Codes: A61B 2562/0261 Strain gauges
• CPC Class Codes: A61B 5/1106 to assess neuromuscular blockade, e.g. to estimate depth of anaesthesia
• CPC Class Codes: A61B 5/1121 Determining geometric values, e.g. centre of rotation or angular range of movement
• CPC Class Codes: A61B 5/1125 Grasping motions of hands
• CPC Class Codes: A61B 5/4519 Muscles A61B5/389, A61B5/224 take precedence
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00

Abstract

Apparatus is provided which enable the assessment of mobility of human and/or animal joints to be carried out. A flexible transducer includes a conductive elastomer which, when stretched, provides a change in an electrical output signal. The transducer is located over the joint to be investigated and during movement of the joint electrical signals from the transducer output which are a function of joint mobility, are produced. The signals are digitized and stored in a memory and are compared with a bank of data from normal and pathological subjects stored in a continuously updated memory. When the comparison locates the `best fit` between the joint movement and the stored data, the type of joint movement is classified and the result is presented on a visual display unit. The movement signal can be conditioned so that the angular displacement of the joint, the rate of joint movement, acceleration of the joint can be estimated and classified. The force produced by the joint can also be calculated using the acceleration and an estimate of the mass moved. This system permits the progress of an individual to be monitored and to identify joint movement characteristics in particular patient populations.

The transducer, when combined in a composite unit with electrodes is also used to accurately assess the degree of neuromuscular activity during and after anaethesia.

Claims

1. Apparatus for obtaining a signal indicative of mobility of a skeletal joint, comprising an assembly formed by a pair of like members physically oriented in parallel and mutually separated by a non-electrically-conductive elastomer, each said member being made of a material which is both elastomeric and electrically conductive having an electrical resistance which varies with elastic extension and contraction of the member, positioning means on the assembly for positioning both members of the assembly simultaneously at a joint to be tested such that movement of the joint elastically extends and contracts both members of the assembly whereby the electrical resistance of each member is varied, a resistance-sensitive electrical network, conductor means connected to each said member and interconnecting each said member with said electrical network to provide a pair of electrical outputs from said network which vary, in use, with movement of the joint under test.

2. Apparatus as claimed in claim 1, wherein said material is composed of a homogeneous mixture of non-conductive elastomer and conductive particles dispersed therein, a plurality of conductive pathways between said conductor means being formed in each said member by mutual contact of adjacent conductive particles, the number of conductive pathways being varied with elastic extension and contraction of each member.

3. Apparatus as claimed in claim 1, wherein each said member is U-shaped having a pair of parallel limbs one end of each limb being free and the other end of each limb being mutually interconnected, each limb having a longitudinal extent said positioning means are adapted for positioning the assembly at a joint to be tested such that movement of the joint elastically extends and contracts the longitudinal extent of each limb of said U-shape, and said conductor means are connected to each member at the free ends of the limbs of said U-shape.

4. Apparatus for determining the mobility classification of a skeletal joint, comprising a member made of a material which is both elastomeric and electrically conductive having an electrical resistance which varies with elastic extension and contraction of the member,

positioning means on the member for positioning the member at a joint to be tested such that movement of the joint elastically extends and contracts the elastic member whereby the electrical resistance of the member is varied,

a resistance-sensitive electrical network,

conductor means connected to said member and interconnecting said member with said electrical network to provide an electrical output from said network which varies, in use, with movement of the joint under test,

an analogue-to-digital converter connected to said electrical network for digitising the electrical output thereof,

identifying means connected to the output of the converter for identifying from the digital data thereby provided at least one characteristic of the joint under test,

memory means pre-programmed with digital information representing at least said one characteristic of a plurality of known skeletal joints,

comparator means connected to said memory means and to said identifying means and arranged to compare at least said one characteristic of the joint under test with that of the known skeletal joints, and

output means connected to the comparison means for presenting a comparator result of identity as indicative of the mobility classification in respect of said one characteristic of the joint under test.

5. Apparatus as claimed in claim 4, wherein the digital information with which said memory means is pre-programmed is relative to predetermined amplitude and time scales, and said identifying means includes normalising means from which said at least one characteristic of the joint under test is identified on said predetermined amplitude and time scales.