Surgery – Truss – Pad
Patent
1995-12-20
1997-12-09
Hindenburg, Max
Surgery
Truss
Pad
128782, A61B 500
Patent
active
056949464
DESCRIPTION:
BRIEF SUMMARY
The present invention relates generally to measurements of physiological pressures in vivo, and in particular to an apparatus and a method for monitoring rapid dynamic changes in physiological pressures.
It further relates to methods of diagnosing certain painful mechanical disorders of a motion segment in the spine.
BACKGROUND TO THE INVENTION AND PRIOR ART
The spinal column is built up of vertebrae and intervertebral cartilage disks, located between each vertebra. The function of the disks is to accomodate the pressure exerted by the body and acting on the spinal column, and to provide mobility and flexibility to the spine.
A motion segment of the spine is defined as an intervertebral disk and/or the vertebrae belonging to the same plane of motion.
Disabling lower-back pain without pathoanatomical changes, believed to be caused by damaged disks, presents great problems to orthopedic and neurosurgeons, both in terms of localising the site of pain and remedying the problem by surgery.
The surgical remedy consists of so called fusion, which comprises removing a disk at the segment where the pain is believed to occur, and replacing it with bone. This fusion operation leads to the segment in question becoming stiff, but the patient is relieved of the pain.
A specific problem with this type of pain is that no abnormal changes are visible during X-ray investigations. Therefore, the method of localising the damaged segment causing the pain has, to date, comprised local anasthesia in the disk, at the suspected segment. If the patient under such local anasthesia becomes pain-free when performing acts that otherwise would be painful, this is taken as one indication that the correct segment has been localised.
In view of the fact that this method is based on the subjective statements made by the patient, and the subjective judgement of the physician carrying out the investigation, a relatively high percentage of errors in the diagnosis occurs, which could mean that a non-damaged disk is removed. In addition, this method of diagnosing is very tedious, and up to a week of hospitalisation may be required, naturally at a very high cost.
Therefore there exists a need for a quick and reliable, objective method of localising the damaged motion segment in patients exhibiting disabling lower-back pain without pathoanatomical changes.
It is now proposed that the pressure in the cartilage disks may be of significance in providing basic information about causes of this kind of pain, and also for diagnosing purposes.
However, the pressure in the disks is a parameter which is difficult to record because of the high pressures prevailing inside the disks. Such pressure can amount to from 0 to 1000 kPa. Furthermore, the constituent medium inside the disks is a gel-like fluid. Such consistency makes conventional liquid column techniques for measuring pressures very difficult to use. In addition, the requirement on the pressure sensor is that it has a very small outer diameter, in order that it be possible to insert it into the disk without patient trauma.
U.S. Pat. No. 4,393,878 discloses a pressure monitoring method and apparatus for use in the human body. The apparatus includes a pressure sensor of the diaphragm type. The apparatus is based on providing a substantially constant flow of gas to and from the sensor interior. Changes in pressure within the body causes the diaphragm to alternately close and open an exhaust tube which results in an increase or decrease in the pressure within the sensor interior until an equilibrium pressure is reached. The sensor is adapted for use in body cavities such as the cranium. It appears to be a bulky construction and is not suitable for use for the purposes of the present invention.
U.S. Pat. No. 4,517,842 discloses a fluid pressure transducer of the nullbalance type in which a fluid whose pressure is being sensed acts against one face of a diaphragm and a balancing control fluid acts against the opposite face. The transducers according to this patent are particularly well adapted for measur
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Olsson et al., "Mobility in the Lumbosacral Spine After Fusion Studied with the Aid of Roentgen Stereophotogrammetry", Clinical Orthopaedic and Rel. Resc., pp. 181-190, (1977).
Berg Svante
Hoek Bertil
Tenerz Lars
Hindenburg Max
Radi Medical Systems AB
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