Patent GB-1074501-A (GB)
Title: Apparatus for diagnosing bone joint disorders
IPC: A61B7/00
Filed: 1964-06-19
Abstract: 1,074,501. Stethoscopic apparatus. R. E. BRACKIN. June 19, 1964, No. 25589/64. Heading H4J. Apparatus for diagnosing the pathologic state of bone joints comprises an acoustical to electrical energy transducer, a mounting for the transducer for securing the transducer adjacent the bone joint to be diagnosed, a second transducer carried by a mounting intended for connection to a joint and a recording device connected to both transducers. In use the recording device makes two simultaneous visual or aural records of the signals from the transducers, the signals corresponding to the noises emitted by the joints during flexure thereof so that a comparative record of the signals can be obtained. One transducer may be applied to a normal joint, and the other to a joint to be diagnosed. Alternatively the two transducers may be applied to opposite sides of a diseased joint. In a transducer complex 20 (Fig. 1) two microphones (e.g. 51 or 53) convert the sound produced by two bone joints into electrical energy which is transmitted to analysis apparatus 21. This comprises a twin channel amplifier 22 and associated filters 23 which filter out signals below 60 c/s. and possibly above 1000 c/s. Preferably all signals pass through the amplifier 22, but if the amplifier is part of a tape recorder the filters 23 precede the amplifier 22. A twin beam galvanometer 25 receives two input signal simultaneously, each of which swings a light beam on a photo-sensitive paper tape which, when developed, presents traces indicative of the frequency and intensity of the signals received. A graphic analyser 26 may be provided to prepare, for example, a graph of a cartilage click, frequency being plotted against amplitude (Fig. 9, not shown). Transducers.-Each microphone may include a flexible rubber tube (56); Fig. 3 (not shown), in which is secured a hypodermic type needle (55) having a bevelled, end. (60) which, in use, is embedded in subutaneous tissue with the bevelled face directed towards the area under study. The microphone (57) receives sounds from a localized small area of the joint. A double microphone, Fig. 4 (not shown), includes two microphones (65, 66) held on opposite knees by a resilient brace (67) which tends to compress the microphones against the knees. Each transducer may comprise ,three microphones (75, 76, 77) embedded in sponge rubber (78) and each microphone of which has leads (79) for connecting to a selector, switch (80). The microphones (75, 76, 77) are spaced apart to be. adjacent the anterior horn, middle and posterior horn of a knee cartilage. A strap (85) having holes (86) is at one side and a strap, (87) having a stud (88) is at the other side. By selection of the hole (86) into which the stud (88) is positioned the pressure of the microphone against the knee joint may be adjusted. Different pressures attenuate different frequencies. Alternately both straps (85), (87) are apertured and are linked by a stud (88) mounted on a splate. Alternatively the microphone pressure may be varied by varying the tension of a spring (90), Fig. 12 (not shown), by a knurled head (95). The microphones are of crystal or magnetic type.