Surgery – Diagnostic testing – Measuring anatomical characteristic or force applied to or...
Patent
1996-07-23
1999-02-23
Apley, Richard J.
Surgery
Diagnostic testing
Measuring anatomical characteristic or force applied to or...
600595, 606 54, A61B 5103
Patent
active
058738436
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/ GB95 /00313 filed Feb. 15, 1995.
The present invention relates to medical apparatus, and more particularly to a device and method for use in assessing the state of union in a bone fracture.
External fixators have been widely used in surgery especially for treating traumatic lesions of large bones, where, after fracture reduction, the burden on the fractured bones is instead carried by a fixator during the healing period. The general method involves boring pins into the healthy bone tissue on either side of the fracture and applying a rigid support frame spanning the fracture to the protruding ends of the pins. When healing of the bone tissue is judged to be complete the external fixator can be removed.
Being outside the body means that the fixator frame lies at a distance from the bone and the resulting lever arm can lead to considerable loads on the fixator frame and/or on the bone. On the other hand external fixation has the advantage that the main components of the device are external to the body and therefore accessible. Strain gauge transducers can be incorporated into external fixators for monitoring loads and deformations over the fracture, and such biomechanical monitoring enables an assessment of fracture healing to be made, to supplement radiology and manual examination in determining the timing of the removal of the fixator. If the supporting external fixator is removed prematurely, late angulation and refracture are common important complications.
A number of methods of measuring the state of fracture healing have been developed. For example, in Clinical Biomechanics, 1992, No. 7, pages 75-79, `Fracture stiffness measurement in the assessment and management of tibial fractures`, the authors J B Richardson et al describe the results of fracture bending stiffness tests on a group of patients with tibial fractures treated with external fixators. The fracture healing measure proposed in that paper is a value of fracture bending stiffness in the sagittal plane of 15 Nmdeg.sup.-1 at which removal of the external fixator and functional loading of the fracture can be prescribed. The article also indicates that such a technique of fracture healing monitoring shows no significant increase in stiffness until about eight weeks after fixation.
In Engineering in Medicine, Vol. 16, No. 4, October 1987, London (GB), pages 229-232, `The measurement of stiffness of fractures treated with external fixation`, J L Cunningham et al, further test equipment and procedures are described for measuring the mechanical stiffness of such fractures. The external fixator described in this publication is fitted with a transducer able to measure loads (eg. torsion, bending) in a number of different directions, and some of the results indicated that increased stiffness may be observed as early as five or six weeks after fixation.
A substantial problem in healing of fractures, especially tibial fractures, is delayed osseous union. Treatment of this problem, by techniques such as bone grafting, should be performed as early as possible. However, conventional techniques using clinical and radiographic examination are slow to detect this problem. Biomechanical monitoring methods involving fracture stiffness, such as those referred to above, provide measures to determine when union is effectively complete and treatment can finish, but do not give an indication as to whether or not the process of healing is properly underway, particularly at the earliest stages of healing.
The aim of the present invention is to improve the above situation and to provide a device and method for use in assessing the state of union in bone fractures, particularly for early detection of delayed osseous union.
In a first aspect, the invention provides a device for use in assessing the state of union in a bone fracture in a limb, the device comprising: elements extendable through respective portions of the fractured bone; during a specific load test; and load measure and the total limb load me
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J.B. Richardson et al, "Fracture stiffness measurement in the assessment and management of tibial fractures", Clinical Biomechanics, 1992, No. 7, pp. 75-79.
Engineering in Medicine, vol. 16, No. 4, Oct. 1987, London (GB)pp. 229-232,J.L.Cunningham et al. "The Measurement of Stiffness of Fractures treated with Section Test Equipment and Procedures" See pp. 230-231.
Peruchon, E., et al., Evaluation and control of growth activity of epiphyseal plate, Medical & Biological Engineering & Computing, vol. 18, No. 4 (Jul. 1980), pp. 396-400.
Apley Richard J.
BTG International Limited
Hwang Victor K.
LandOfFree
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