Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/45—For evaluating or diagnosing the musculoskeletal system or teeth
  • A61B5/4504—Bones
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
  • A61B17/60—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like for external osteosynthesis, e.g. distractors, contractors
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
  • A61B17/60—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like for external osteosynthesis, e.g. distractors, contractors
  • A61B17/62—Ring frames, i.e. devices extending around the bones to be positioned
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
  • A61B17/60—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like for external osteosynthesis, e.g. distractors, contractors
  • A61B17/64—Devices extending alongside the bones to be positioned
  • A61B17/6441—Bilateral fixators, i.e. with both ends of pins or wires clamped
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
  • A61B17/60—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like for external osteosynthesis, e.g. distractors, contractors
  • A61B17/66—Alignment, compression or distraction mechanisms
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
  • A61B90/06—Measuring instruments not otherwise provided for
  • A61B2090/064—Measuring instruments not otherwise provided for for measuring force, pressure or mechanical tension
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
  • A61B90/39—Markers, e.g. radio-opaque or breast lesions markers
  • A61B2090/3937—Visible markers
  • A61B2090/3945—Active visible markers, e.g. light emitting diodes

Definitions

• a fixation device serves to fixate the ends of the bone in relation to each other as well as to carry the load or part of the load which a patient may have to place on the bone during the healing process.
• fixator when extending the length of a bone. This is done by performing an osteotomy, i.e. by performing a substantially transversal cut in the bone, by preferably gradually pulling the ends of the bone apart at a predetermined and limited distance and by fixating the ends of the bone adjacently to each other.
• the space between the ends of the bone will gradually be filled with new bone material, after which the ends of the bone may be pulled apart once again in order to increase the length of the bone even further.
• the external fixating device the fixator, which may be unilateral, semicircular or circular, may be removed.
• stiffness and strength of a bone will refer to the same physical parameter of a bone, e.g. the resistance to deformation once a force or load is placed on the bone.
• the load, force or strain placed on the fractured bone will be difficult to determine on the basis of the load placed on the limb, and the deformation of the bone and the limb will depend on the assembly as a whole.
• a load on a limb in an axial direction may of course result in an axial deformation of the fracture bone, but it may also result in an angular deformation, e.g. a twisting motion, and a bending deformation.
• a further prior art fixation device is described in WO 98/00062.
• This fixation device has two ring-shaped members attached to a fractured bone by pins on each side of the fracture.
• the two ring-shaped members are connected to each other by connecting studs in order to support the bone.
• One of the ring members comprises a first and a second element which may be rotated in relation to each other.
• the first element carries the connecting studs while the second element is connected to the pins.
• the two elements may be rotated in relation to each other when a force is exerted on the bone, i.e. the healing fracture, via one of the elements whereby the two bone parts will be subject to a torque attempting to twist the two bone parts in relation to each other.
• the extent of the movement, e.g. the angle, and the exerted force corresponding to the torque, may be measured in order to obtain values reflecting the strength of the bone.
• the true state of the healing process and the true strength of the bone, e.g. the healing bone fracture may not be dete ⁇ nined by this method.
• a still further object of the invention is to provide an apparatus for determining the strength or stiffness of a bone, and in particular a healing bone, whereby the strength or stiffness of the bone may be determined with improved accuracy, whereby an improved method of determining the time for removal of a holding device, and in particular an external holding device, may be provided.
• fixation device for a healing bone, whereby the fixation device will facilitate improved determination of the strength or stiffness of the bone, e.g. the healing bone.
• the invention relates to a method of measuring the strength of a bone, in particular a bone healing after a fracture or an osteotomy which has been performed in order to extend, reduce or alter the angle of the bone, whereby external fastening means are attached onto the bone in at least two locations, whereby said external fastening means are provided with means for detection and/or measurement of relative displacement between said at least two external fastening means, whereby the bone is subject to strain, and whereby corresponding measurements and/or detections are made of the relative displacement by contactless measurement of and/or detection means.
• a measurement is made which will provide a more accurate assessment of the strength and/or stiffness of a bone as the measuring arrangements will not have any influence on the result of the measurements, e.g. the measuring arrangements will not contribute to the stiffness of the structure, i.e. the bone or bones subject to the measurements.
• the contactless measuring arrangement will allow increased flexibility when setting up the arrangement and also allow measurements to be performed in more than one dimension.
• the external fastening means may be part of external fixing means for supporting the bone.
• a flexible and convenient way of obtaining measurements is achieved which are necessary for evaluating the healing state of a bone as fastening means already attached onto the patient may be used when performing the method.
• the invention also concerns a method, as stated in claim 6, which relates to the measurement of the strength of a bone, in particular a bone healing after a fracture or after an osteotomy, whereby external fastening means are attached onto the bone in at least two locations, whereby said external fastening means are provided with means for detection and/or measurement of relative displacement between said at least two external fastening means, whereby the bone is subjected to strain, and whereby corresponding measurements and/or detections are made of the relative dis- placement in at least two dimensions of the strain on the bone.
• the bone may be subjected to strain by the patient and the strain may be measured, detected and/or visualized.
• deformations may be induced in a convenient manner and the cause of the deformations be documented.
• the corresponding measurements and/or detections of the relative displacement and the strain on the bone may be correlated and/or recorded, whereby a comparison of the deformations and the causes may be made, whereby an assessment of the strength of the bone may be conveniently performed.
• the invention relates to an apparatus, as claimed in claim 11, for measurement of the strength of a bone, in particular a bone having a healing osteotomy or a healing bone fracture, said apparatus comprising external fastening means for connection to the bone in at least two locations, said external fastening means being pro- vided with means for detection and/or measurement of relative displacement by contactless measurement and/or detection means between said at least two external fastening means.
• an apparatus whereby a measurement is made which will pro- vide a more accurate assessment of the strength and/or stiffness of a bone as the measuring arrangements will not have any influence on the result of the measurements, e.g. the measuring arrangements will not contribute to the stiffness of the structure, i.e. the bone or bones subject to the measurements.
• the contactless measuring arrangement will allow increased flexibility when setting up the arrange- ment and allow measurements to be performed in more than one dimension by the apparatus.
• the apparatus is provided with means for measurement and/or detection of induced strain on the bone.
• the cause of the defor- mations may be readily documented and utilized in connection with the assessment of the bone strength.
• the apparatus may be provided with means for correlating said measurements and/or detections of relative displacement and strain, whereby a com- parison of the deformations and the causes may be made by the apparatus, whereby an assessment of the strength of the bone may be conveniently performed on the basis hereof.
• the means for contactless measurement and/or detection of relative displacement between said at least two external fastening means may facilitate measurement and/or detection of a relative longitudinal displacement, a relative rotational displacement and/or a relative angular displacement.
• measure- ments may be made of any deformations induced by any given force or load placed on the bone.
• the apparatus is provided with means for supporting one or both ends of a limb, for positioning one end of a limb and/or for transferring force to/from the limb to/from measuring means.
• the patient may exert the load or force necessary to induce the deformations of the bone or bones.
• the weight of a limb alone may constitute a load or the patient may place more or less bodyweight on the limb.
• the patient may exert force on the bone in any other direction than the vertical direction, e.g. horizontal direction, attempting to twist the bone etc., whereby more varied deformations may be induced.
• the apparatus may comprise means for indicating, visualizing and/or recording the measured and/or detected strain.
• the cause of the deformations may be documented by the apparatus, whereby an assessment of the strength of the bone may be performed by a skilled user.
• the apparatus may preferably comprise means for indicating, visualizing and/or recording the measured and/or detected relative displacement, whereby the result of the measurements may be used for immediate or subsequent assessments.
• the invention further relates to an apparatus, as claimed in claim 19, for measurement of the strength of a bone, in particular a bone having a healing osteotomy or a healing bone fracture, said apparatus comprising external fastening means for con- nection to the bone in at least two locations, said external fastening means being provided with means for detection and/or measurement of relative displacement in at least two dimensions between said at least two external fastening means, and said apparatus being provided with means for measurement and/or detection of an in- Jerusalem strain on the bone.
• an apparatus is provided by means of which a more accurate assessment of the strength and/or stiffness of a bone may be performed as the measuring arrangements of the apparatus will facilitate measurements in more than one dimension and thus provide improved measurements of the induced deformations than those of prior art apparatuses.
• the apparatus may be provided with means for correlating said measurements and/or detections of relative displacement and strain, whereby a comparison of the deformations and the causes may be provided by the apparatus, whereby an assessment of the strength of the bone may be conveniently performed by a skilled person, e.g. a physician.
• the means for detection and/or measurement of relative displacement in at least two dimensions between said at least two external fastening means may facilitate measurement and/or detection of a relative longitudinal displacement, a relative rotational displacement and/or a relative angular displacement.
• measurements may be made of any deformations induced by any given force or load placed on the bone.
• the means for detection and/or measurement of relative displacement in at least two dimensions may be configured as mechanical measuring means, e.g. slide gauges or other similar means connected to the two external fastening means in such a manner that measurements may be made in two or more dimensions.
• the external fastening means may be part of external fixing means for supporting the bone.
• an apparatus according to this embodiment may be utilized in a flexible and convenient way to obtain the measurements neces- sary for assessing the healing state of a bone as fastening means already attached onto the patient may be used in connection with or as part of the apparatus.
• the apparatus may be provided with means for supporting one or both ends of a limb, for positioning one end of a limb and/or for transferring force to/from the limb to/from measuring means.
• the patient may exert the load or force necessary to induce the deformations of the bone or bones.
• the weight of a limb may constitute a load alone or the patient may place more or less bodyweight on the limb.
• the patient may exert a force on the bone in any other direction than the vertical direction, e.g. horizontal direction, attempting to twist the bone etc., whereby more varied deformations may be induced.
• the apparatus may comprise means for indicating, visualizing and/or recording the measured and/or detected relative displacement, whereby the result of the measurements may be used for immediate or subsequent assessments.
• the invention also pertains to an external fixation device, as stated in claim 26, which relates to an external fixator for supporting a bone, e.g. a bone in a limb of an animal or a human being, said fixator comprising means for fastening onto the bone in at least two locations and connecting means for providing a preferably adjustable connection between said fastening means, wherein said connection means are replaceable and wherein measurement and/or detection means for detection and/or measurement of relative displacement between said at least two external fas- tening means are attachable to said at least two external fastening means.
• a fixator for supporting a bone or bones is provided which may also serve as fastening means when performing measurements of the flexibility of the bone.
• the measurements and hence the assessment of the healing state of the bone may be performed in a expedient manner when a fixator according to the invention is util- ized.
• said measurement and/or detection means for detection and/or measurement of relative displacement between said at least two external fastening means are contactless.
• a measurement may be made which will provide a more accurate assessment of the strength and/or stiffness of a bone, as the measuring arrangements will not have any influence on the result of the measurements, e.g. the measuring arrangements will not contribute to the stiffness of the structure, i.e. the bone or bones subject to the measurements.
• the contactless measuring arrangement will allow increased flexibility when setting up the arrange- ment and also allow measurements to be performed in more than one dimension.
• said measurement and/or detection means for detection and/or measurement of relative displacement between said at least two external fastening means may be configured for detection and/or measurement of relative displacement in at least two dimensions.
• the means for detection and/or measurement of relative displacement in at least two dimensions may be configured as mechanical measuring means, e.g. slide gauges or other similar means connected to the two external fastening means in such a manner that measurements may be made in two or more dimensions.
• Other measuring means than purely mechanical ones may be used as well.
• said at least two external fastening means may each comprise or be connected to a structural member which surrounds the body part containing the bone at least partly, said preferably adjustable connection between said fastening means being connected to said structural members.
• the fastening means may constitute a firm connection for attachment of the measurement and/or detection means.
• connection means comprises one, two, three, four or more connecting rods which may preferably be adjustably placed between said at least two fastening means.
• a versatile fixator is achieved which may be used in a wide number of applications.
• the measurement and/or detection means for detection and/or measurement of relative displacement between said at least two external fastening means are attachable to said structural members forming part of or being connected to said at least two external fastening means.
• the fastening means may con- veniently be fastened onto appropriate places, e.g. the front of the bone, the side etc., and provide a firm connection.
• the measurement and/or detection means for detection and/or measurement of relative displacement may comprise electrical, magnetic or electro- magnetic measurement and/or detection means.
• the fixator may be flexibly used in connection with a number of different measuring arrangements selected according to actual use, actual measurement, and/or processing arrangements and/or other preferences.
• the measurement and/or detection means for detection and/or measurement of relative displacement may comprise optical measurement and/or detection means, for example in the form of digital video cameras or light emitting devices such as for example LEDs.
• optical measurement and/or detection means for example in the form of digital video cameras or light emitting devices such as for example LEDs.
• the measurement and/or detection means for detection and/or measurement of relative displacement may comprise one or more measurement and/or detection means.
• the measurement and/or detection means for detection and/or measurement of relative displacement in at least two dimensions comprise two or more measurement and/or detection means placed at a circumferential distance, e.g. in relation to an axis of the bone, whereby the accuracy of the measurements may be enhanced and hence also the accuracy of the assessment of the strength of the bone and consequently the healing state of the bone.
• fig. 1 illustrates a bone separated in two parts and deformations of this bone schematically
• fig. 2 shows a fixation device attached onto the lower leg of a human being
• fig. 3 illustrates the fixation device shown in fig. 3 with deformation measuring means attached
• fig. 4 shows an alternative deformation measuring arrangement
• fig. 5 shows a block diagram illustrating the signal processing according to a further embodiment of the invention.
• Fig. 1 illustrates a bone 10, for example a bone of a human being.
• This bone 10 has been separated in two parts 10a and 10b, for example a proximal part 10a and a distal part 10b.
• the separation may be due to a fracture or to an osteotomy operation.
• Dur- ing healing the bone will flex at the place of separation when exposed to stress.
• the flexing may be illustrated by the two bone part vectors 11a and 1 lb, extending from an origin 12a and 12b, respectively.
• the direction of these vectors represents axes of the bone parts 10a and 10b, e.g. local bone axes and not necessarily an axis of the bone 10.
• the bone parts 10a and 10b will move longitudinally when exposed to stress.
• the bone parts will move towards each other when subjected to an at least partly longitudinal force, whereby the healing part of the bone will be compressed. This will be indicated by a reduction of the distance 13 between the origins 12a and 12b of the bone part vectors 1 la and 1 lb, respectively.
• a relative rotational movement of the two bone parts 10a and 10b which is illustrated by a vector 14a and a vector 14b, extending from the origins 11a and l ib, respectively.
• These vectors 14a and 14b may extend at right angles from the bone part vectors 11a and 11 b, respectively, and/or they may extend in one and the same direction, preferably in a direction perpendicular to one or both of the bone part vectors 11 a and l ib.
• these vectors extend in a reference direction, illustrated by the punctuated lines 15a and 15b, respectively.
• angles 16a and 16b between the vector 14a and the refer- ence direction 15a and between the vector 14b and the reference direction 15b respectively serve to indicate the rotational movement of the bone parts 10a and 10b and hence also the relative rotational displacement of the bone parts.
• This holder may be used to support a fractured bone while healing or, as illustrated, for a leg 20 on which an osteotomy is performed in order to extend, reduce or alter the angle of the bone, and to support the bones during the healing process.
• the external fixator may be unilateral, e.g. support by only one axial supporting bar or rod, semicircular, e.g. support of half a circle surrounding the bone, or circular, e.g. support is essentially circumferentially.
• the fixator comprises a number of ring-shaped structural members 21, 22, 26 and 27.
• the upper ring-shaped member is attached onto one or both bones, the tibia 29 and the fibula 28, of the lower leg by bone pins, bone screws, bone rods or as shown by bone wires 23 connected to the ring-shaped member 21 by connectors 24 and 25.
• the connectors 24 and 25 allow the bone wire to be fastened onto the ring-shaped member 23 with sufficient tensile strength to assure a rigid connection between the ring- shaped member 21 and the bone or bones 29 and 28.
• the ring-shaped member 22 is similarly connected to one or both of the bones 28 and 29 by wires 23 and connectors 24 and 25.
• the lower ring-shaped members 26 and 27 are fastened onto the lower part of one or both of the bones 29 and 28 in the same fashion.
• the upper ring-shaped members 21 and 22 are located above the healing sites 29a and 28a of the tibia 29 and the fibula 28, respectively, and the lower ring-shaped members are located below the healing sites 29a and 28a.
• Connecting means 30 in the form of connecting rods are placed between the ring-shaped members in order to support the bones, i.e. the leg.
• the connecting rods are threaded, at least at the ends, whereby they can be connected to the ring-shaped members by nuts.
• Longer con- necting rods 30a are located between the ring-shaped members 22 and 27 and shorter connecting rods 30b are located between the ring-shaped members 21 and 22 and the ring-shaped members 26 and 27.
• the distance between the ring-shaped members can be adjusted.
• the distance between the ring-shaped members 21 and 22 and the ring-shaped members 26 and 27, respectively, can be adjusted in dependency of the actual placing of the corresponding bone wires 23.
• the distance between ring-shaped members 22 and 27 can be adjusted by the connecting rods 30a in order to fixate the bone parts appropriately in relation to each other.
• the fixator can be adjusted to achieve the natural relations between the bone parts, after which the relationship is maintained until the fracture site has healed sufficiently.
• the stage of the healing process e.g. the stiffness or strength of the healing fracture site, can be determined as shown in fig. 3.
• This figure corresponds to fig. 2.
• the connecting rods 30a of the fixating device have been loosened (in the early stages of the healing process) or removed, leaving the leg and the bones 29 and 28 unsupported or partially unsupported.
• a number of light emitting devices such as for example light emitting diodes (LEDs) 31 has been placed on one of the upper ring- shaped members 22. These LEDs are each mounted at one end of a fixture 32, which has attachment means 33 at the other end by which it is connected to the ring-shaped member 22, for example by through-holes in the ring-shaped member.
• LEDs light emitting diodes
• a bracket has been mounted on one of the lower ring-shaped members 27.
• the bracket comprises a number of rods 35 which are attached by clamping means 37 to the ring-shaped member 27 at the lower ends, for example by bolt and nut.
• a ring-shaped support has been mounted, and a number of mini-cameras 34 have been placed on the support 35 and/or the rods 35.
• the cameras which may be digital video cameras such as USB-cameras. are placed in such a manner that they are located in the proximity of the light emitting devices
• an axial deformation will be determined by a vertical change of the position of the image of the light-emitting device 31 on the corresponding camera 34.
• a rotational flexing will be determined by a horizontal change of the position of the image of the light-emitting device 31 on the corresponding camera 34, and as more than one LED/camera arrangement is used, in the example four, a bend, e.g. an angular flexing of the bone, will be detected by a difference in the changes of the posi- tions of the image of the light-emitting device 31 on the corresponding camera 34. It is evident that more than two camera/LED-arrangements of this particular configuration placed at different locations may be necessary to achieve this.
• Figure 3 shows that four camera/LED-arrangements may be used and evenly distributed on the circular ring-shaped support 36, e.g. with an angle interval of 90°.
• Other configurations obvious to a skilled person may be used as well, and additional camera/LED-arrangements may be used, e.g. two, three, four, five etc.
• the LED-arrangements 32, 33, 34 and the camera arrange- ments 34, 35, 36, 37 may be configured as units which may be attached onto the corresponding ring-shaped members 22 and 27 as units whereby the placing of the measuring arrangements may be performed in an easy and fast manner.
• the patient may be able to exert a twisting torque on the leg, e.g. by attempting to turn his foot.
• the force in e.g. horizontal direction exerted by the foot may then be measured or detected by the measuring means related to the bracket.
• the patient may exert bending force on the leg by attempting to push the foot forward, backwards or sideways, whereby the force may be measured or detected by the measuring arrangements in a similar manner.
• the force exerted by a patient attempting to turn or twist his foot may also be determined by using for example a electromotor, e.g. an electrodynamic motor, arranged axially beneath the support. When the patient attempts to turn his foot, this will have to be done against a torque exerted by the motor.
• the torque can be determined, as will be obvious to a skilled person, by knowledge of the motor characteristics and by dete ⁇ riining the motor current. Further, the maximum torque may be controlled by controlling the motor current, whereby it can be avoided that the patient may place an excessively large load on the bone, as the motor will just allow further turning when the maximum torque has been reached.
• FIG. 4 Another arrangement for measuring the relative flexing movements, e.g. the deformation of a bone, is illustrated in fig. 4.
• a camera 41 On one on these ring-shaped members 22 in the example, a camera 41 is placed and points towards the other ring- shaped member 27 in the example.
• a reference device 42 On this ring-shaped member 27, a reference device 42, which must be placed in such a manner that it will be in the vision field of the camera 41 in an unstrained situation of the bone, is placed in a similar manner.
• the reference device 42 comprises a number of indicator elements in the form of light emitting diodes (LEDs) 43 for positioning the reference device 42 in the right position in relation to the camera 41.
• LEDs 43 are placed in a particular pattern, e.g. in parallel rows and columns as illustrated, in order to facilitate the adjustment and positioning of the reference device 42 and/or the camera 41.
• the reference device 42 comprises a number of indicator elements in the form of light emitting diodes (LEDs) 44 for detecting the relative movements, i.e. deformations of the bone.
• LEDs 44 are placed opposite a mirror 45 which is placed at an angle of for example 45° in relation to the plane at which the LEDs 44 are positioned.
• deformations of the bone in one, two or three dimensions can be detected and measured.
• axial deformation can be detected as the distance between the LEDs 44 is known, whereby relative axial movements may be determined by processing the corresponding video images, e.g. the distances on the images.
• rotational movements can be detected and measured as the initial positions of the reference device 42 and the LEDs 44 are known in the unrestrained situation.
• Fig. 4 shows only one set of cameras with a reference device by which it will be possible to determine the deformations of a bone. More than one set of cameras and a reference device may be utilized whereby the accuracy of the determined or meas- ured deformations may be improved.
• the mirror 45 may be placed at other angles than the illustrated 45°, whereby corresponding alterations to the configuration may have to be performed, however.
• the signals 51a - 5 In from a number of sets of measuring arrangements comprising for example video cameras as measurement tools are led to a processing unit 52, wherein the signals are processed in order to determine actual deformations and/or values corresponding to such deformations.
• a processing unit 52 wherein the signals are processed in order to determine actual deformations and/or values corresponding to such deformations.
• the processing unit 52 may be connected to a indicating device 53, for example a scale, on which the patient and/or the physician may observe the magnitude of the resulting deformations. Further, the signals 57 from the processing unit 52 are led to a further processing unit 59 which will be described later.
• Signals 54a - 54m for example signals from a weight cell, a force measuring device, a torque measuring device etc.
• This unit may be connected to a force indicator 56, for example in the form of a scale, which allows the patient and/or the physician to observe the force and the load placed on the bone by the patient, for example.
• the force signal processing unit 55 may process the incoming signals to calculate the actual force which acts on the bone or bones and may indicate this force in normalized and/or standardized val- ues, e.g. the vertical force, horizontal force, force in a forward direction etc.
• the resulting signals 58 from the force signal processing unit 55 are led to the additional processing unit 59 which serves to co ⁇ elate the measured and/or detected deforma- tions with the load or force exerted on the bone or bones.
• the results 60 hereof may be indicated on a display (not shown), for example in graphical form or as tables, or/and they may be printed. Further, the results may be stored by means of a storing unit 61, whereby the results may be used in connection with testing of the healing state of bones on other patients, on different bones of the same patient, or in connection with subsequent testing of the same bone or bones of the same patient. Further, the test results may be used as e.g. statistical data in connection with improvements of methods for assessing the healing state of bones.

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