Device and system for fixating bone fragments during healing - Patents.com

Abstract

To provide a sternotomy closure technique with a cerclage mechanism which is capable of maintaining proper bony compression (within a desired range) across the sternum cut, in spite of a range of external forces and significant lateral distraction due to these external forces.SOLUTION: The sternum fragments are aligned in apposition disposed around a longitudinal seam and secured with a resilient element. The resilient element is tensioned to a desired tension to compress the sternum to a desired compression range. The resilient element is then elongated and contracted while accepting multiple cycles of physiological distracting forces across the sternum while maintaining contact pressure across the longitudinal seam within a desired range for a length of time sufficient for bony healing. The resilient element is preferably a polymer cable comprising an elongated elastic polymeric core coaxially surrounded by a sheath woven from ultra-high molecular weight polyethylene strands.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] Related Applications

[0001] This application claims the benefit of Provisional Patent Application No. 62 / 448,309, filed January 19, 2017, to C. Pratt et al. [Background technology]

[0002] Many surgeries involving the heart and other thoracic structures require complete access to the interior chest area. Typically, this access is obtained by dividing the sternum along its entire length using an osteotomy, which splits the sternum from its upper pole to its lower pole using a saw. This osteotomy of the sternum is commonly called a median sternotomy. Approximately 700,000 sternal osteotomies (i.e., sternotomies) are performed annually in the United States.

[0003]

[0003] Upon completion of open-heart surgery (or other surgery requiring access to the thoracic cavity, e.g., lung transplant), the sternum must be sutured. Typically, this involves joining the two divided halves of the sternum together using a fastening technique. The goal is to properly appose the two bone segments so that they can heal and resume the normal function of the sternum in the musculoskeletal system. The desired result is complete osseointegration, restoring the sternum to as close as possible to its preoperative state. To achieve this goal, the sutures must be sufficiently robust to allow complete bone formation and healing to occur across the sternotomy.

[0004]

[0004] Most sternotomy procedures are performed using stainless steel or other metal alloy wires with instruments such as wire clamps and wire cutters. Braided metal cables can be used alone or in combination with bone fixation devices such as plates and screws.

[0005]

[0005] Traditional methods often fail to achieve high-quality bony union. Reliable bone healing requires good stability of the bone fragments and close approximation of the fragments with minimal gap widening. Poor stability and excessive gap widening can lead to nonunion, fibrous union, or partial union. Poor stability and bone healing after median sternotomy are associated with very high treatment costs and high patient morbidity and mortality, and are responsible for numerous potential complications ranging from long-term patient discomfort to acute dehiscence and deep sternal wound infection (mediastinitis).

[0006] Many factors adversely affect the success of sternal sutures. These factors include failure to accurately quantify and apply a controlled clamping force (load) across the divided bone, failure to maintain bony apposition in the correct position, allowing too much (or too little) movement, and failure to transfer load across the osteotomy during healing. Additional factors include the tendency of the wire or metal cable to cut through the bone and soft tissue due to movement and / or force, loss of fixation due to fatigue of the metal wire or cable, or failure of the metal wire or cable itself due to fatigue. Furthermore, the patient's wound healing or general health can be affected by metal ions released from metallic wires, cables, plates, and screws.

[0007]

[0007] For optimal healing, three factors must be present: bone apposition, restriction of motion, and transmission of forces across the plane of the osteotomy. In all cases, an adequate blood supply must be present for healing to occur.

[0008] To stabilize the reassembled (split) sternum, forces must be applied to the bony segments to hold them together during normal activities that occur during the healing process. This is particularly difficult because the sternum experiences fluctuating and often transient forces transmitted through the ribs or other tissues during activities such as breathing, coughing, moving, lying down, sitting up, and other activities of daily living. For example, sneezing has been shown to generate lateral distraction forces of up to 814 Newtons on the sternum. Summary of the Invention [Problem to be solved by the invention]

[0009] A polymer cable sternotomy technique has been proposed that can achieve many of the above-mentioned objectives. This technique is successfully implemented with the fastening system described herein that is capable of maintaining adequate bone compression (within a desired range) across the sternotomy despite a range of external forces and the significant lateral distraction that these forces cause. [Means for solving the problem]

[0010] This method fixates a split sternum during healing. The sternal fragments are aligned in apposition, positioned around the longitudinal joint and secured with elastic elements. The elastic elements are tensioned to a desired tension to compress the sternal halves to a desired compression range. The elastic elements then expand and contract, allowing multiple cycles of physiological distraction forces across the sternum while maintaining contact pressure across the longitudinal joint within the desired range for a length of time sufficient for bone healing. The elastic elements are preferably polymeric cables including an elongated elastic polymer core coaxially surrounded by a sheath woven with ultra-high molecular weight polyethylene strands.

[0011]

[0011] These and other features, aspects, and advantages of the present invention will become better understood with reference to the following drawings, description, and claims. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a graph showing elongation over time for an anatomical sternotomy model secured by 1) the present invention, 2) a steel cable, and 3) a steel wire. [Figure 2]

[0013] Photograph showing four stainless steel sternal cables attached to a sternotomy model using a parasternal / transsternal "figure-of-eight" wrapping technique. [Figure 3]

[0014] 10 is a graph showing force as a function of time during application of a cyclic, time-varying lateral distraction force to a sternotomy model for a super cable, a metal cable, and a metal wire loop. [Figure 4]

[0015] 10 is a graph showing residual force as a function of position along the sternotomy model for two super-cable configurations, a wire cable, and a wire loop. [Figure 5]

[0016] One possible embodiment of a device that can be employed when practicing the techniques described herein is shown with a divided sternum. DETAILED DESCRIPTION OF THE INVENTION

[0013]

[0017] Rather than steel or other metallic wires or cables, the present sternotomy suturing technique preferably uses a polymeric engineered cable available from Kinamed, Inc., Camarillo, California, and sold under the name "SuperCable." The cable is constructed of an elongated elastic polymer core, suitably nylon, coaxially surrounded by a sheath woven with ultra-high molecular weight polyethylene strands. Further information and description of this "SuperCable" can be found in Matt No. 6,589,246 to Chen, incorporated herein by reference. The cables are highly flexible and resilient, with high fatigue and tensile strength. Such cables can undergo repeated extension / contraction cycles during the healing phase while maintaining the ability to provide compressive loads across the osteotomy surface.

[0014]

[0018] Figure 1 shows the cyclic behavior of stretch versus time for an anatomical sternotomy model secured by cables in accordance with the present invention. The lower curve represents the "supercable" assembly (supercable-secured sternotomy model) for testing with only four supercables (each doubled as a circumferential loop). For comparison, similar curves are shown for a steel monofilament wire (seven loops, curved at the top) and a braided steel cable (four loops, curved in the middle). In both cases, the two halves of the sternum were forced into lateral distraction for five cycles using a Chatillon LRX material testing system with a cyclic force varying from zero to just over 1000 newtons. All of the sternum halves in the test can be seen to exhibit distraction in response to the application of force. However, the steel cable and steel wire models are unable to return to their original position and exhibit greater sternal displacement for a constant force after several cycles compared to the supercable construction. This phenomenon is believed to result from a combination of effects, including irreversible metal cable stretching (or metal wire unwinding) and cutting into the bone model. Both are believed to contribute to the sagging of the steel wire and steel cable models. In contrast, the Super Cable configuration repeatedly returns to its original position, even after multiple cycles of stretching and sagging. In this test, the steel wire (#5 steel wire manufactured by Ethicon) and steel cable (Pioneer Surgical Technology, now Fusion Innovations) failed to keep the sternum model intact, while the Super Cable kept the sternum model intact. After the load cycle, both the steel cable and steel wire completely failed to fixate the sternum after the load cycle.

[0015]

[0019] Steel wires and cables are believed to be unable to maintain reliable compression across a split sternum due to at least two factors. First, they have high stiffness and cannot accommodate a wide range of extension without losing initial bone contact length. Most of the elasticity of the complete model assembly is believed to reside in the bone model, not the wires or cables. Metal cables and wires can unravel slightly, thereby irreversibly lengthening. Second, such cables tend to bite or cut into the bone, further creating the potential for loosening of the fasteners. This further tends to create irreversible loosening across the osteotomy plane. Both metal wires and cables are known to completely cut the sternum, not only failing to secure a median sternotomy but also significantly complicating subsequent reconstruction by bisecting the split sternum.

[0016]

[0020] Additional testing was conducted to support the idea that a more resilient polymer cable, such as the "Super Cable," better maintains pressure between the sternum halves, thereby maintaining stability.

[0017]

[0021] Anatomical synthetic sternum model (20 lb / ft 3 Form, Model No.: 1025-2, Sawbones®, Vashon, WA, USA) were used in the study [Trumble, DR, McGregor, WE & Magovern, JA (2002). Validation of a Bone Analog Model for Studies of Sternal Closure. The Annals of Thoracic Surgery, 74(3):739-745]. The sternal models were potted, divided along their midline, and then divided into the following sections: It was fixed in place.

[0018] 1. Four super cables (Kinamed®) in a parasternal wrapping technique in the first, second, fourth, and fifth intercostal spaces, each tensioned at approximately 36.3 kg (approximately 801 bs).

[0019] 2. Seven No. 5 stainless steel surgical wires (A&E or Ethicon®), five of which were used in a parasternal wrapping technique in the first through fifth intercostal spaces, one placed laterally within the manubrium, and one placed laterally within the xiphoid process, were tensioned according to the manufacturer's instructions, and excess twisted wire was cut off, with the cut ends facing down toward the sternal surface.

[0020] 3. As shown in Figure 2, four stainless steel sternal cables (Pioneer®) were used in a parasternal / transsternal "figure-of-eight" wrapping technique and tensioned according to the manufacturer's recommended procedure.

[0021]

[0022] Prior to testing, all force sensors (SingleTact, model number: CS15-450N, Pressure Profile Systems, Los Angeles, CA, USA) were calibrated by running a standard cycle of 10 cycles from 0 N to 400 N on a materials testing system (Chatillon, model number: LRX). These calibration values ​​were used to calibrate the raw data obtained by the force sensors during structural testing.

[0022]

[0023] A single active force sensor was consistently placed adjacent to the third intercostal space within the sternotomy plane on all test samples, with sufficient offset to avoid interference from the placement of metallic wires or cables. Four other non-active sensors of the same type were equally spaced along the sternotomy plane to ensure uniform loading.

[0023]

[0024] A sneeze can generate a lateral distraction force of 814 Newtons on the sternum [Adams, J. et al. (2014). Comparison of Force Exerted on the Sternum During a Sneeze Versus During Low-, Moderate-, and High-Intensity Bench Press Resistance Exercise With and Without the Valsalva [Maneuver in Healthy Volunteers. The American Journal of Cardiology, 113(6):1045-1048] Using a materials testing system (Chatillon, model number: LRX), the sternal halves were laterally distracted with 10 cycles of cyclic forces ranging from 0 to 800 Newtons using a materials testing system (Chatillon, model number: LRX). The test was captured on video while measuring and recording forces across the sternal fragments throughout the application of cyclic loading and after cyclic loading was completed (i.e., in the unloaded state).

[0024]

[0025] The results are shown in Figure 3. The graph shows the force (measured by the pressure sensor) as a function of time during the application of a cyclic, time-varying lateral distraction force. Results are shown for the super cable, metal cable, and metal wire loop.

[0025]

[0026] Table 1 summarizes the residual force, percent force retained, and magnitude of recovered force for all three cable systems.

[0026] [Table 1]

[0027] Additional testing further demonstrated important differences in how the supercable construct performed compared to metal wire and metallic constructs. The above testing was repeated with two key modifications. First, an additional fixation model was added, including two supercables in a parasternal wrapping technique at the second and fourth intercostal spaces and two supercables in a lateral parasternal / transsternal "figure-of-eight" wrapping technique at the first and fifth intercostal spaces within the manubrium and xiphoid process (similar to the upper and lower cables in Figure 2). Each cable was tensioned to a compressive force of 36.3 kg (80 lbs) across the divided sternum. Second, two more active force sensors were placed within the sternal model, adjacent to the upper and lower edges of the model, and one each within the manubrium and xiphoid process. All other setup and calibration details remained consistent. Figure 4 illustrates the results. The graph shows the residual force (measured by the pressure sensors) as a function of position along the sternotomy model. Results are shown for both Super Cable configurations, the metallic Pioneer Cable, and the metallic wire loop. Both Super Cable configurations resulted in higher residual forces than either the metallic cable or the wire loop at all three sensor locations representing the entire length of the sternotomy model.

[0027]

[0028] A higher residual force between the sternal halves is a measure of stability after a cyclic loading situation (such as sneezing or coughing) and can predict continued approximation of the sternal halves to promote bone healing. A higher percent force retention is a measure of whether the residual force after cyclic loading continues to persist as additional cycles are applied throughout the healing process. A greater force recovery is a measure of how much force is absorbed by the sternal suture structures rather than being transmitted between the sternal halves (leading to dissection of the bone). This force absorption logically minimizes potential dissection of the wires / cables because it also minimizes the stress applied to the sternal halves.

[0028]

[0029] The favorable combination of these parameters enhances fixation stability and ensures close approximation of the sternal halves throughout the healing process, resulting in improved healing, less patient pain, and fewer potential complications. This study demonstrates that the Super Cable configuration performs well in all three parameters, indicating that the use of Super Cable is advantageous for achieving improved sternal fusion compared to metallic wires or cables. Further studies will be conducted to determine the effectiveness of the Super Cable in longitudinal shear, transverse shear, and sternal fusion. would be expected to show similar results for tests assessing the combined effect of all biomechanical forces experienced by the sternum.

[0029]

[0030] In summary, the test results indicate at least three important differences in how the Super Cable configuration performs compared to the metal wire and metal cable configurations. These differences are: (1) the residual force between the sternal halves after cyclic loading, (2) the retention of compressive force between the sternal halves, and (3) the magnitude of the recovered force. The calculated values ​​for these parameters are summarized in Table 1.

[0030]

[0031] Thus, in a first aspect, the present invention is a method for fixating a divided sternum during healing, comprising aligning apposition-positioned sternal fragments around a longitudinal joint, securing the fragments by encasing them in a polymeric cable comprising an elongated elastic polymer core coaxially surrounded by a sheath woven with ultra-high molecular weight polyethylene strands, and tensioning the strands to a desired tension to compress the sternum within a desired compression range to tolerate multiple cycles of physiological distraction forces across the sternum while maintaining contact pressure across the longitudinal joint within a desired range to minimize potential dissection for a length of time sufficient for bone healing. The length of time required varies widely depending on variables such as surgical technique and patient compliance, but bone healing typically takes 6 to 12 weeks.

[0031]

[0032] The elastic properties of the "Super Cable" are believed to be advantageous in absorbing shock and equalizing the load transmitted to the sternum, thus reducing the tendency of the cable to cut the bone.

[0032]

[0033] One possible embodiment of a device that can be employed when practicing the techniques described herein with a sternum is shown in FIG. 5 , along with a sternum. This configuration is suitably used to perform a "pressure calibration method." Excellent results have been obtained using this surgical technique to calibrate the relationship between pressure across the joint (between the sternum fragments) and tension on the suture cable. In this technique, a polymer "super cable" is used as the tensioning tool. The tensioning tool is preferably a Super Cable Cerclage Tensioning Instrument with a 60° angle, commercially available from Kinamed, Inc., catalog number 35-800-7000. The tensioning tool allows a compressive force of 360 to 530 Newtons (80 to 120 lbs) to be applied across the sternal incision surface by the cable. Modifications and variations of the tensioning tool can be included without departing from the invention.

[0033]

[0034] According to a pressure calibration method, the present invention provides a method for fixating a divided sternum (10) during healing, comprising arranging juxtaposed sternal fragments around a longitudinal joint, inserting at least one thin pressure sensor (12) at the longitudinal joint between the sternal fragments, fixating the fragments by wrapping them with a polymer cable (14) comprising an elongated elastic polymer core coaxially surrounded by a sheath woven with ultra-high molecular weight polyethylene strands, using a pressure monitor (16) to monitor the pressure sensed by the pressure sensor (16) while applying a variable tension to the polymer cable with a tensioning tool (18), detecting a relationship between the variable tension and the pressure sensed by the pressure sensor, removing the pressure sensor, and tensioning the polymer cable to a desired tension based on the detected relationship between the variable tension and the pressure to create a desired pressure at the joint between the sternal fragments, and maintaining the pressure during healing.

[0034]

[0035] In a more generalized manner, the pressure calibration method may be performed using a sufficiently elastic cable or other elastic element, including a spring or the like. The use of "super cables" (polymer cables comprising an elongated elastic polymer core coaxially surrounded by a sheath woven with ultra-high molecular weight polyethylene strands) is believed to be highly advantageous and to provide an independent new source of supply.

[0035]

[0036] Pressure sensors are available that are thin and accurate enough to determine applied pressure. For example, a 450 N (100 lb) thin film capacitive force sensor can measure They are commercially available from Profiles Systems Inc. under catalog number CS15-450N. They are sub-branded as SingleTact sensors, and additional information can be found at https: / / www.singletact.com / micro-force-sensor / calibrated-sensors / 15mm-450-newton / . The sensors are supplied calibrated with open-source software for data capture. Other thin sensors can also be used. In a preferred embodiment, multiple sensors are used, or sensors capable of measuring a pressure profile that varies along an axis, such as the axis of the sternotomy (seam), or along a significant portion of that axis, generally from the superior pole of the bone (manubrium) to the inferior pole (xiphoid process).

[0036]

[0037] In a preferred embodiment, the pressure calibration method described above is carried out in conjunction with the first aspect described above.

[0037]

[0038] The pressure modulation method is advantageous because the relationship between tension (within the fastener) and pressure (across the bone joint) depends on several variables, including the patient's specific anatomical proportions, age, sex, and weight; the bone configuration and health of the tissues within the sternum; and the specific number and wrapping method selected by the surgeon. The inventors believe that pressure across the osteotomy is a more reliable indicator of optimal fixation compared to tension within the cable, which is often the only force metric reported for metallic suture systems. Based on empirical data, a pressure range of 0.7 to 4.9 MPa (when applied to cortical bone) is considered appropriate, with the ideal pressure depending on some or all of the variables mentioned above.

[0038]

[0039] The pressure calibration method may also be used as a means to obtain empirical data that can be used to provide tension guidance during sternal closure surgery without the need for pressure sensors. For example, empirical tests using pressure sensors can be performed to determine the appropriate load to apply to patients of different ages, weights, genders, bone qualities, etc. Alternatively, preoperative CT scan slices made perpendicular to the osteotomy surface can be used to quantify the amount of bone present at the sternal level, with CT "slices" taken for each patient. Because the amount of bone present correlates with the load applied by the patient at the slice location, the desired load to ensure reliable stability across the osteotomy surface can be estimated. Alternatively, DEXA (dual-energy X-ray absorptiometry) scans can be used, as they are routinely utilized to assess bone density and therefore bone strength. This data can then be used to determine the appropriate tension or compression force to apply (without the need for corresponding pressure sensor information) when performing sternal closure as described herein.

[0039]

[0040] In the present invention, the polymer cable can be suitably tensioned and spliced ​​by known methods, such as a cable lock as described in U.S. Patent No. 7,207,090. This cable fixation device is currently preferred because it provides secure fixation of the polymer cable at a maintainable desired tension and because the components are suitably manufactured from materials that minimally interfere with imaging techniques such as magnetic resonance imaging, x-ray, and computed tomography.

[0040]

[0041] According to yet another aspect of the present invention, the polymer cable fastening is applied as multiple cables, i.e., at least upper, lower, and central fastenings. Each cable is preferably applied in a loop or "figure-eight" configuration, either in a parasternal or transsternal configuration. Each section is then tensioned, potentially in a preferred sequence, preferably with different tensions to achieve or approximate the desired pressure profile across the cut sternum. In a first variation, different tensions can be achieved by simply pulling the multiple cables differently using a tensioning tool. In another variation, at least one of the three (or more) polymer cables may be designed to provide different tension / stretch characteristics. For example, at least one polymer suture cable securing the sternum may be designed to have different strength, stiffness, and / or size than the others by a combination of varying the core diameter, varying the sheath weave angle, and / or varying the total cable size.

[0041]

[0042] While various numbers of fastening cables can be used, preferred embodiments use fewer than six distinct fastening cables, which is fewer than the typical configurations used with conventional metallic wires. The lower number permitted using Super Cables is effective in facilitating convenient and time-efficient suturing without increasing the risk of cutting the cables into the bone, and polymeric cables are believed to be less prone to cutting into the abrasive, elastic bone surface compared to metallic wires or cables.

[0042]

[0043] In addition to its method aspects, the present invention includes an apparatus aspect. Considered as an apparatus, the present invention includes a thin pressure transducer 12 insertable between at least two cut sternum 10 fragments, at least one fastening cable 14 comprising a polymer cable including an elongated, resilient polymer core coaxially surrounded by a sheath woven with ultra-high molecular weight polyethylene strands, the at least one cable securing the sternum fragments in apposition to promote bone healing, a pressure monitoring system 16 coupled to the pressure transducer and configured to display the pressure sensed by the transducer, a device such as a fastener 20 for securing the fastening cable in position around the sternum fragments, and a tensioning tool 18 operable to apply a variable tension to the at least one fastening cable in response to user manipulation or programming, such that a user can manipulate the tensioning tool while monitoring the pressure displayed by the pressure monitoring system to determine the relationship between the variable tension and the resulting pressure between the sternum fragments, thereby determining the desired tension to be applied to the at least one fastening cable for securing to achieve the desired resulting pressure.

[0043]

[0044] As with the method aspect, the device preferably includes multiple polymer-focused cables, with at least three (top, bottom, and center) being preferred. The device for securing the cables may suitably be as described in U.S. Pat. No. 7,207,090. Other possible fixation devices include, for example, disposable tensioners or plastic fasteners so that the entire structure is radiolucent. The fixation devices are suitably those described in U.S. Pat. No. 9,107,720 or U.S. Pat. No. 8,469,967, or available from Kinamed, Inc. as described above, or variations or modifications of such devices. Further improvements and modifications are contemplated within the scope of the present invention. For example, in some embodiments, the tensioning tool may be mechanically or electrically coupled to a pressure monitoring system (22) to assist in automating the calibration of tension-related pressure. In this context, "calibration" should be understood to mean the act of establishing a relationship between the applied cable tension and the resulting pressure between the cut surfaces of the osteotomy. For this purpose, a tension sensor (an electronic variable resistor responsive to cable tension or tool torque) may be used. A pressure monitoring system (transmitter / receiver) may be provided and coupled to a pressure monitoring system or other data processing system. The pressure monitoring system may include tension monitoring (by analog or digital data processing) and / or data processing capabilities to facilitate calibration and display of pressure versus cable tension. The pressure monitoring system may include mechanically or automatically adjusting tension once the desired pressure is programmed by the user. Such variations are also within the scope of the present invention and may have independent basis of novelty.

[0044]

[0045] The embodiments of the present invention described herein are illustrative, and various modifications, variations, and rearrangements may be readily envisioned to achieve substantially equivalent results, all of which are intended to be encompassed within the spirit and scope of the present invention as defined in the appended claims. (Item 1) 1. A method for fixing a divided sternum during a healing period, comprising: arranging the sternum fragments in a juxtaposed arrangement about the longitudinal seam; fastening the sternum fragments together with an elastic element; tensioning the elastic element to a desired tension to compress the sternum fragments together to a desired compression range; and stretching the elastic element under multiple cycles of physiological distraction forces across the sternum while maintaining contact pressure across the longitudinal joint within a desired range for a length of time sufficient for bone healing. (Item 2) 2. The method of claim 1, wherein the step of securing the sternal fragments together with an elastic element comprises wrapping the sternal fragments together, the elastic element being a polymer cable including an elongated elastic polymer core coaxially surrounded by a sheath woven with ultra-high molecular weight polyethylene strands. (Item 3) 1. A method for fixing a divided sternum during a healing period, comprising: arranging the sternum fragments so that they are arranged side-by-side about the longitudinal seam; fastening the sternum fragments together with an elastic element; inserting at least one pressure sensor into the longitudinal joint between the sternum fragments; applying a variable tension to the elastic element using a tensioning tool while monitoring the pressure sensed by the pressure sensor; detecting a relationship between the variable tension and the pressure sensed by the pressure sensor; removing the pressure sensor; and tensioning the elastic element with a desired tension based on the detected relationship between variable tension and pressure to create a desired pressure at the longitudinal seam between the sternum fragments. (Item 4) 4. The method of claim 3, further comprising the step of securing the cable around the sternum fragments. (Item 5) Item 3. The method according to item 3, wherein the at least one pressure sensor includes at least two pressure sensors, and the at least two pressure sensors are positioned between the sternum fragments at different positions along the longitudinal seam; The method, wherein the step of monitoring the pressure comprises independently monitoring the at least two pressure sensors to determine the pressure sensed by each pressure sensor. (Item 6) 4. The method according to item 3, wherein the desired pressure range is 0.7 megapascals or more and 4.9 megapascals or less. (Item 7) 4. The method of claim 3, wherein the step of detecting a relationship between the variable tension and the pressure sensed by the pressure sensor includes processing tension and pressure data from the pressure sensor with an electronic data processor to determine a relationship function relating applied tension to resulting pressure. (Item 8) 4. The method of claim 3, further comprising automatically controlling with an electronic data processor the step of tensioning the elastic element with a desired tension based on the detected relationship between variable tension and pressure to create a desired pressure at the longitudinal joint between the sternum fragments. (Item 9) 4. The method of claim 3, wherein the elastic member is a polymer cable including an elongated elastic polymer core coaxially surrounded by a sheath woven with ultra-high molecular weight polyethylene strands. (Item 10) 1. A device for fixing a surgically cut sternum during healing, comprising: a pressure transducer insertable between at least two pieces of the sternum cut into pieces; elastic members that can be juxtaposed and secure the sternal fragments in place to promote bone healing; a pressure monitoring system coupled to the pressure transducer and configured to measure the pressure sensed by the transducer; and a tensioning tool capable of applying a variable tension to the elastic member in response to user operation or a programmed digital computer, whereby the user can operate the tensioning tool while monitoring the pressure measured by the pressure monitoring system to determine a relationship between the variable tension and the pressure generated between the sternum and determine a desired tension to be applied to the elastic member to secure it to generate a desired pressure. (Item 11) Item 11. The device according to item 10, wherein the pressure transducer comprises at least two pressure transducers positionable at different points between the sternum fragments; each of the at least two pressure transducers independently coupled to the pressure monitoring system; The apparatus, wherein the pressure monitoring system is configured to independently monitor each of the at least two pressure transducers. (Item 12) 11. The device according to claim 10, further comprising a digital computer programmed to automatically control tension in response to the relationship between the variable tension and the pressure created between the sternal fragments. (Item 13) Item 13. The device of item 12, wherein the tension is automatically controlled to vary the tension applied to secure the at least one fastening cable. (Item 14) Item 14. The device according to item 13, wherein the tension is automatically controlled to obtain a desired pressure in the range of 0.7 megapascals to 4.9 megapascals. (Item 15) Item 11. The device according to item 10, wherein the elastic member comprises at least one polymer cable comprising an elongated elastic polymer core coaxially surrounded by a sheath woven with ultra-high molecular weight polyethylene strands, the at least one polymer cable being capable of juxtaposing and securing the sternal fragments in an appropriate position to promote bone healing. (Item 16) 1. A device for fixing a divided sternum during treatment, comprising: an elastic member arranged to secure the sternal fragments in juxtaposition in an appropriate position to promote bone healing; The elastic member is capable of sufficient elastic extension to undergo multiple cycles of physiological distraction forces across the sternum while maintaining contact pressure across the longitudinal joint within a desired range for a length of time sufficient for bone healing. (Item 17) 17. The device of claim 16, wherein the cable is configured to maintain a contact pressure within a desired range of 0.7 to 4.9 megapascals for a length of time sufficient for healing of the bone. (Item 18) Item 17. The device of item 16, wherein the elastic member is at least one cerclage cable comprising an elongated elastic polymer core coaxially surrounded by a sheath woven with ultra-high molecular weight polyethylene strands, the at least one cable configured to secure the sternal fragments in juxtaposition in an appropriate position to promote bone healing.

Claims

1. 1. A device for fixing two or more bone fragments during healing, comprising: a resilient element configured to secure the bone fragments in position to promote bone healing; a sensor insertable between the bone fragments to sense the contact pressure between the bone fragments caused by the elastic element; The device, wherein the elastic element is capable of elastic extension sufficient to allow multiple cycles of physiological distraction forces across the bone fragments while maintaining the contact pressure between the bone fragments within a desired range for a length of time sufficient for bone healing.

2. 10. The apparatus of claim 1, further comprising a pressure monitor in communication with the sensor for monitoring the contact pressure between the bone fragments caused by the elastic element.

3. 3. The apparatus of claim 2, wherein the pressure monitor is configured to display the contact pressure sensed by the sensor.

4. The device of claim 1 , wherein the elastic element comprises a cable.

5. 5. The device of claim 4, wherein the cable comprises an elongated elastic polymer core coaxially surrounded by a sheath.

6. 6. The device of claim 5, wherein the sheath comprises a sheath woven from ultra-high molecular weight polyethylene strands.

7. 10. The apparatus of claim 1, further comprising a tensioning tool operable to vary the tension on the elastic element.

8. 8. The apparatus of claim 7, wherein the tensioning tool is operable to adjust the tension on the resilient element in response to the contact pressure sensed by the sensor.

9. 1. A system for fixating two or more bone fragments during healing, comprising: a resilient element configured to secure the bone fragments in position to promote bone healing; a sensor inserted between the bone fragments to sense the contact pressure between the bone fragments caused by the elastic element; a pressure monitoring system coupled to the sensor and configured to monitor the contact pressure sensed by the sensor; a tensioning tool operable to apply tension to the elastic element to create the contact pressure between the bone fragments within a desired range for a length of time sufficient for bone healing.

10. The system of claim 9 , wherein the sensor measures contact pressure between the bone fragments.

11. 11. The system of claim 10, wherein the pressure monitoring system displays the contact pressure measured by the sensor.

12. 12. The system of claim 11, further comprising a computer in communication with the pressure monitoring system and programmed to correlate the contact pressure between the bone fragments to the tension on the elastic element.

13. The system of claim 9 , wherein the elastic element comprises a cable.

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