Surgery – Truss – Pad
Patent
1987-11-05
1990-04-03
Jaworski, Francis
Surgery
Truss
Pad
33512, A61B 510
Patent
active
049131630
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION(S)
This United States application stems from PCT International Application No. PCT/AU87/00087 filed Mar. 27, 1987.
TECHNICAL FIELD
The present invention relates to a device for measurement of the laxity of the anterior and/or posterior cruciate ligament of the knee of a patient and preferably also the capsular stability of the knee.
BACKGROUND ART
Damage to the anterior and/or posterior cruciate ligament and the capsule of the knee is common following trauma to the knee such as can be experienced skiing, playing football and in motor vehicle accidents to name but a few. Currently subjective interpretation of the unstable knee is made by the Orthopaedic surgeon attending the patient using a manual test such as the Lachman test. This estimation is made pre- and post-operatively and varies with the amount of force used by the surgeon in the examination. Estimating capsular laxity as opposed to cruciate ligament rupture, which has implications for the necessity of operation, is very difficult using this method.
A number of attempts have been made in the past to produce devices to objectively measure anterior and/or posterior cruciate ligament rupture. These attempts are summarized in U.S. patent specification No. 4,583,555 which itself discloses a device for this purpose. The present inventors have found that all of these prior art proposals suffer from the deficiency that they do not produce an indication of the amount of relative displacement between the femur and the tibia at a plurality of different applied forces. The present inventors provide a device which gives, in preferred embodiments, a plot of relative displacement between the femur and the tibia against an actively applied force i.e., a force applied by the patient rather than the surgeon conducting the examination.
DISCLOSURE OF THE INVENTION
The present invention consists in a device for the measurement of laxity of the knee of a patient, comprising a first support member adapted to support the thigh of a patient, a second support member adapted to support and hold the foot, ankle or lower leg of a user, the first and second support members being so placed that a leg of the patient will be bent at the knee when resting on the first and second support members, means to measure movement of the tibial tuberosity of the said leg of the patient, or of some other portion of the patient's anatomy that moves therewith, relative to the femur of the said leg of the patient, or some other portion of the patients anatomy that moves therewith, and means to measure the force applied by the patient in endeavouring to straighten the said leg such as by tensioning the quadriceps muscle.
In a preferred embodiment of the invention the movement of the tibial tuberosity is measured by the movement of a probe which contacts the tibial tuberosity and is mounted on support means which move with the femur. The most convenient way of measuring the position of the femur is in fact to measure the position of the patella which moves with the femur; other methods of detecting the relative spatial position of the femur could however be used. In a particularly preferred embodiment of the invention the support means comprises a frame pivotably connected to the device and having a bar, pad or like engagement member which rests on the patient's patella and which supports the tibial probe in contact with the tibial tuberosity. It will be realized however that the measurement of the relative movement of the tibia and of the patella could be achieved in a variety of other ways such as by using separate probes measuring independently the absolute movement of both the tibial tuberosity and the patella and integrating those measurements. In another embodiment of the invention the engagement member may rest on the tibia and the probe rest on the patella.
In a preferred embodiment of the invention the device also includes means to plot or otherwise indicate a correlation between the force applied and the relative movement between the tibia
REFERENCES:
patent: T100602 (1981-05-01), Roley et al.
patent: 4534364 (1985-08-01), Lamoreux
patent: 4549555 (1985-10-01), Fraser et al.
patent: 4583554 (1986-04-01), Mittelman et al.
patent: 4583555 (1986-04-01), Malcolm et al.
patent: 4799497 (1989-01-01), Riley
Markolf et al., J. of Bone and Joint Surgery, vol. 60-A, No. 5, Jul. 1978, pp. 664-674.
Ferkel, Richard D., et al., "Instrumented Clinical Knee Testing for Anterior-Posterior Stability: How, What, Why?", pp. 6-20.
Cross Mervin J.
Roger Gregory J.
Hanley John C.
Jaworski Francis
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