WO2019104392A1

WO2019104392A1 - Modular tissue implants

Info

Publication number: WO2019104392A1
Application number: PCT/AU2018/051283
Authority: WO
Inventors: Dietmar Hutmacher; Nathan CARLOS; Sebastian Eggert
Original assignee: Queensland University Of Technology
Priority date: 2017-11-30
Filing date: 2018-11-30
Publication date: 2019-06-06

Abstract

The disclosure is directed a system for constructing a tissue scaffold. The tissue scaffold comprises at least a first set of modular components, where each component of the first set has substantially the same shape. The components of the first set are configured to allow interconnection. The disclosure is also directed to a method of forming a scaffold implant using the system.

Description

Modular Tissue Implants

Technical field

This disclosure relates generally to modular tissue implants and a method of constructing a tissue implant using modular components.

Background

The advent of affordable and reliable additive manufacturing techniques such as 3-D printing and centring has lent itself to the field of surgical applications. It is known to use 3-D printing techniques to provide custom-made prostheses and implants. However, the provision of these custom-made components is costly and time-consuming. In a medical context any such delays can have a significantly deleterious effect upon the health and well-being of the patient. Furthermore, the cost associated with these prevents such techniques from being available more readily.

European patent application 1449 500 A2 discloses a bone implant comprised of modular components. However, this disclosure uses modules which correspond in shape to predefined portions of a predetermined bone. Each of the modules are significantly different size and shape and generally correlate to different bones.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

Summary

The disclosure provides a system for constructing a tissue scaffold comprising at least a first set of modular components, each component of the first set having substantially the same shape, wherein the components of the first set are configured to allow interconnection to form the tissue scaffold.

It is to be realised that the term‘scaffold’ as used herein may include a scaffold intended to be used to promote tissue growth, or a scaffold used to impart structural support, for example, in a prosthesis.

Having a modular system for forming a tissue scaffold which can be used as patient-specific implant may help to break down a resulting scaffold into smaller component parts that is easier to handle, for example during surgery. Patient-specific scaffolds are introduced as the means to obtain a customized implant fit. Patient-specific scaffolds may help to provide greater implant accuracy with the added benefit of shorter rehabilitation and overall reduction in patient treatment costs. A modular but still patient-specific tissue scaffold may shorten surgery times with smaller incision and better alignment which may allow faster postoperative rehabilitation and less blood loss. The patient-specific modular scaffold may be produced through the use of additive manufacture techniques including 3D printing, and may give modular implants added value because it almost has no limitations in the realisation of complex bone defect reconstructions. This may enable the formation of trabecular surfaces that can ensure better secondary fixation of the tissue scaffold. All other advantages of patient-specific implants compared to standard implants arise from the design and the construction of an individual implant and the level of product personalisation.

The system may further comprise a second set of modular components, each component of the second set having substantially the same shape. A shape of the components of the second set may be different from the shape of the components of the first set. The first and/or second set may comprise two or more components. In an embodiment, a single first component and interconnectable with a single second component.

Each component may comprise a plurality network of interconnected voids arranged to enable passage of a fluid or a mechanical element through or across the component. The components may comprise a plurality of interconnected structs which are configured to form the network of interstitial voids. The struts may define a pattern comprising a repetition of a unit cell.

Each component may comprise a plurality of struts defining interstitial voids, and the struts may define a pattern comprising a repetition of a unit cell.

The unit cell may be of a shape comprising any one of: gyroid, double gyroid, diamond, neovious, Schwarz D, Schwarz P, icosahedron.

The system may further comprise a second set of modular components, each component of the second set having substantially the same shape, wherein the components of the first set have a different shape, configuration or structure to the second set. The system may further comprise a second set of modular components, each component of the second set having substantially the same shape. The components of the first set may differ from components of the second set according to one or more of: thickness of the struts; cross-dimensional shape of the struts; shape of the interstitial voids; size of the interstitial voids; or shape of the unit cell.

The system may further comprise at least one custom component. The custom component may be manufactured by an additive technique. The custom component may be of a shape, configuration or structure different to the first or second components. The custom component may be a unique component that is structurally different to the modular components. The custom component may be interconnectable with the modular components.

The system may further comprise at least one port component. The port component may comprise a port arranged for introduction of fluid. The port component may be configured to interconnect with the components of the first set of modular components. The fluid may be introduced into interstitial voids of the components. The fluid may be introduced into an internal volume defined by one of more of the components for example an annual space. The fluid may comprise biological material, such as marrow, bone fragments, growth factors and the like.

The modular components of the first set may comprise one or more ducts arranged passing through each component. The ducts may be so that ducts of interconnected components are in fluid communication with one another.

At least two components of the first set of modular components may comprise one or more ducts. Each of the at least two components may have ducts that define describing the same path through the respective components.

At least two components of the first set of modular components may comprise one or more ducts describing different paths through the respective components.

One or more of the components may comprise a plurality (e.g. one or more) of struts arranged in a pattern, wherein the pattern is defined by a repeated unit cell.

The unit cell may comprise a repeatable portion of a periodic shape. The shape may be the repeatable portion of any one of: gyroid, double gyroid, diamond, neovious, Schwarz D, Schwarz P, icosahedron.

Interconnection between components of the first and/or second set may be provided by an interconnection means. The interconnection means in some embodiments comprises a male portion that is engageable with a female portion.

The interconnection means may comprise one or more of: a tongue and groove arrangement, a snap-fit arrangement, hook and loop arrangement. The

interconnection may be an interference fit. Adjacent components may be irreversibly connected together in the interconnected state. Interconnection may also be provided by fixation to an auxiliary structure such as a fixation nail.

The components of the first set may each comprise a void so that, when the components interconnect, corresponding voids at least partially align.

The first set of components may further comprise a plurality of covers. Each cover may be shaped to engage with the void of a respective component of the first set to thereby create an enclosed void within the respective component.

The enclosed void may be suitable for housing one or more of: a pin or a conduit.

A component may comprise an auxiliary structure, such as a fixation or a plate. The plate may comprise one or more voids used to attach to a bone.

The components may comprise biodegradable material. The biodegradable material may be a medical-grade polymer. The biodegradable polymer may be polycaprolactone (PCL). The components may be formed by electrospinning printing and/or fused deposition modelling and/or additive manufacturing processes such as 3D printing.

A further embodiment extends to a method of forming a scaffold for tissue growth comprising:

providing a first set of modular components, each component of the first set having substantially the same shape, wherein the components of the first set are configured to allow interconnection; and

interconnecting two or more components from said first set.

The method may further comprise obtaining an image of a defect, designing a scaffold with reference to the image and constructing the scaffold by interconnecting two or more components from the first set of modular components.

The step of designing the scaffold may occur remotely from the step of obtaining the image of the defect.

The method may further comprise: designing at least one custom component having a shape different from components of the first set, manufacturing the custom component utilising an additive manufacturing technique and interconnecting the custom component to a component of the first set.

The step of designing the custom component may occur remotely from the step of manufacturing the custom component. The step of providing the first set of modular components may comprise providing the system as set forth above. A further embodiment extends to a method of forming a scaffold for tissue growth comprising:

providing system for constructing a tissue scaffold as herein described; and

interconnecting two or more components from the first set of the system.

The modular components of the first set may comprise one or more ducts arranged so that ducts of interconnected components are in fluid communication with one another and wherein at least two components of the first set of modular components comprise one or more ducts describing different paths through the respective components, the method further comprising the steps of:

designing a duct system for the scaffold; and

interconnecting modular components comprising one or more ducts with reference to the designed duct system.

The modular components may be loaded with a patient-specific biological material prior to implantation and/or interconnection of the modular components. The patient-specific biological material may be removed from healthy tissue from the patient. The patient-specific biological material may be removed from the patient using a Reamer-Irrigator-Aspirator (RIA) device, for example when obtaining bone marrow and small bone particles for bone regeneration. The modular components may be implanted into a patient prior to interconnecting two or more components from the first and/or second set of the system.

The intended use of the disclosed system is to allow joint prostheses where it is necessary to replace more than one bone. The tissue scaffold may be a bone scaffold i.e. a scaffold for regeneration of bone. The scaffolds may be surface modified to promote cell and/or tissue growth. For example, for a bone scaffold, a portion of the scaffold may be surface coated with calcium phosphate.

Brief description of figures

Embodiments will now be described by way of example only with reference to the accompanying non-limiting Figures.

Figure 1 is a schematic diagram of a system according to an embodiment in use; Figure 2 is a schematic diagram of various components for use with the system of Figure 1 ;

Figure 3 illustrates components with ports;

Figure 4 illustrates the components of Figure 3 in use;

Figure 5 illustrates structural details of components according to embodiments of the invention;

Figures 6 and 7 illustrate components according to embodiments of the invention in use with plates and pins;

Figure 8 illustrates an arrangement of a component according to an embodiment of the invention;

Figures 9A to 9C are schematic illustration of a plate installed with an embodiment of the invention;

Figures 10A to 10C illustrate a port inserted in an embodiment of the invention;

Figures 11A to 11C illustrate an embodiment of the invention;

Figures 12A to 12C illustrate an embodiment of the invention;

Figure 13 is a schematic illustration of an embodiment of the invention inserted on a bone; and

Figures 14 to 19 illustrate components for use with embodiments of the invention.

Figure 20 shows (a) a top, (b) front (anterior), (c) back (posterior), and (d) cross-sectional view of an embodiment of a medical-grade polycaprolactone-CaP scaffold having injection ports.

Figure 21 shows representative x-ray images after 12 month of a (a) defect reconstructed with a mPCL-CaP scaffold and allogenic MPCs (delayed injection), and (b) a defect reconstructed with the application of autologous bone grafts (ABG).

Figure 22 shows biomechanical analyses (torsional moment) after 12 months. Box plots demonstrate median values ± 1st and 3rd quartile of torsional stiffness in all experimental groups. Error bars represent maximum and minimum values.

Asterisks indicate statistical significance (p<0.05).

Figure 23 shows biomechanical analyses (torsional stiffness) after 12 months. Box plots demonstrate median values ± 1st and 3rd quartile of torsional stiffness in all experimental groups. Error bars represent maximum and minimum values.

Asterisks indicate statistical significance (p<0.05). Figure 24 shows the results of microCT scanning after 12 months. Box plot demonstrate median amounts of newly formed bone ± 1st and 3rd quartile within the 3 cm defects 12 months after surgery. Error bars represent maximum and minimum values.

Detailed description of embodiments

Figure 1 illustrates a bone 8 in which a defect region 10 has been identified. It is to be realised that embodiments of the invention are not limited to the manner in which a particular defect may be identified. Furthermore, it is to be realised that embodiments of the invention would apply outside of bone tissue. The terms scaffold, implant, scaffold implant and the like are used interchangeably throughout the disclosure.

Figure 1 illustrates a first scaffold 102 and a second scaffold 104, both covering the defect region 10. As illustrated, different components (here generically labelled 106) may be selected to make up the scaffold covering the defect region 10. The defect region 10 generally is diseased and unhealthy tissue that requires removal, for example cancerous and/or tumorous tissue. In an embodiment the defective tissue is removed and is replaced with a plurality of components 106. Generally, the defect region includes a portion of healthy tissue so that there are clear margins surrounding the scaffold 10.

Figure 2 illustrates different components which may be selected to make up a scaffold such as those illustrated in Figure 1. Figure 2 illustrates components 12, 20, 22, 24, 26 and 28. As illustrated with reference to component 12, each component is shaped to allow interconnection between components. So, component 12 is formed with tongues 14 and corresponding grooves 16, if a plurality of components each having the same shape and size as component 12 are provided, they are capable of being interconnected to thereby build up a scaffold. In some embodiments, component 12 has a boss (e.g. a projection) that is configured to fit into a respective recess in an adjacent component. For example, in some embodiments, feature 14 is a boss and feature 16 is a cylindrical recess.

Furthermore, components having different shapes may also be

interconnected if required. Therefore, the component 20 has a tongue 34 and a groove 36. The tongue 34 may interconnected with the grooves 16 of component 12 and, similarly, the groove 36 of component 20 may engage with the tongues 14 of component 12. As illustrated in Figure 2, the remaining components 22, 24, 26 and 28 are shaped with corresponding tongues and grooves. Components 12 and 22 differ by a variation in height, components 22 and 24 differ by a variation in diameter, and components 26 and 28 differ by the interlocking means, where component 28 uses a sliding/locking connecting means in the (bottom) end face rather than a recess. In each of 12, 20, 22, 24, 26 and 28, the tongues 14 fit with the groove 16 with one another.

In alternate embodiments, the components interconnect by means of wedges, pins, barbs, a snap-fit arrangement, hook and loop arrangement, interference fit and/or corrugated surfaces. Once interconnected, the components may not be disconnected from one another i.e. adjacent components are irreversibly connected to one another.

Component 28 further comprises a bracket 29 which is used as a terminal fixation point for an attachment to the proximal or distal bone.

As indicated in Figure 2, the components may vary in height, diameter or their method of interconnection. Importantly however, a user may be provided with a plurality of each kind of component so that any particular kind of component may be reused as desired. As illustrated, different kinds of components differ in their shape. In certain embodiments, a set of components may comprise components having the same shape but varying in size. For example, cylindrical components having a diameter of 15 mm but with varying lengths may be used in some embodiments. Some of the embodiments depicted in the Figures omit the interconnecting means for clarity only and the absence of interconnecting means in the Figures does not limit the disclosure to these structures.

Embodiments may have an advantage over scaffolds which are purely custom-made since use of a set of components, each component having a substantially similar shape, will be significantly cheaper than custom-making the entire scaffold. Although some scaffolds will require a custom-made component, being able to mix-and-match with module components means the size of the required custom component is smaller compared with an entire custom scaffold, thus reducing costs and manufacturing time. The modular components may also allow a patient-specific implant to be formed from“off-the-shelf” components.

Figure 3A illustrates a component 30 into which a port 32 has been connected. The port further comprises a membrane 34 through which fluid may be introduced by syringe 36. It is to be realised that syringe 36 is provided merely by way of example and, in further embodiments, the manner in which fluid is introduced into the port 32 may be varied.

Figure 3B illustrates a further component 40 with a conduit 42 inserted therein. The conduit 42 includes a Luer lock 44 to selectively allow the introduction of fluid, for example, by use of a syringe 36. In use the port 32, Luer lock 44 or other appropriate inlet they be used to deliver pharmaceutical or biological material/agents such as cells, growth factors, antibiotic etc. The port is used to inject biological material into the scaffold, including cellular material such as marrow and stem cells, tissue fragments such as fragments of bone, growth factors and the like. The port may be used at the end of implantation to inject biological material into the scaffold, or at a later time post-implantation, such as a few weeks after implantation.

Implantation of a scaffold often induces an immune inflammation response which is not always conducive for proper tissue growth when trying to repair defective tissue, so being able to inject biological material into the scaffold after a certain time after implantation (e.g. once the immune response has subsided) through the port may help to improve tissue growth.

Figure 4 illustrates an implant 50 with the components 30 and 40 incorporated therein. The modular nature of the components 30 and 40 allow them to be mix-and- matched as required. In the embodiment of Figure 4, component 30 is spaced apart from component 40 with another component, such as any one of components 12, 20, 22, 24 and 26. Component 28 may be placed distally to component 40 so that component 28 engages with bone via bracket 29.

As illustrated in Figures 3A and 3B, components of embodiments constructed as a mesh having webbing 52 constructed around interstitial voids 54. In the embodiment illustrated in Figures 3A and 3B, the structure of the component is such that the interstitial voids have a cube shape.

It is be realised that the construction of components will influence the composition of the components. Furthermore, the ability of the components to withstand particular forces will depend on the manner in which the webbing and the interstitial voids are arranged. Figures 5(A) to 5(L) illustrate 12 different exemplary topologies of struts (e.g. 200) and voids (e.g. 202). The term“struts” is to be interpreted broadly to include the material used to form the scaffold that and that defines the voids. The interconnecting means is such that adjacent components can interlock with one another regardless of the type of topology used in the

components.

It is to be realised that the topology may be selected according to the desired function and, in an embodiment, the topology is designed using finite element analysis to meet a particular load. The dimension(s) of each scaffold modular component in some embodiments is determined by finite element analysis. The dimension(s) of each scaffold modular component may also be determined by the surgical procedure. However, regardless of the dimension and topology of each component, each component is still able to interconnect with one another, for example using the tongues and grooves as described in Figure 2.

A scaffold according to an embodiment may be used together with known surgical devices such as plates and pins. Figure 6 illustrates a scaffold 120 which is attached to a bone 122. As illustrated, plates 62 and 64 are attached to the scaffold 120 in a known manner, such as with surgical screws. Similarly, pins 72 and 74 are also attached to the bone 122, passing through the scaffold 120. In an alternate embodiment, the pins attach to a plate. In an embodiment, the plates are integrally formed with one or more components. For example, one or more components may be formed around the outer surface of a fixation nail. It is to be realised that the porosity and topology of the struts and corresponding interstitial voids of the plates can be varied according to requirements. For example, a scaffold for ossification generally requires a different topology and mechanical properties compared to a scaffold intended to promote cartilage growth.

In an alternate embodiment a component is provided with an integrated plate. Alternatively, the plate may be provided as a component. The plates may therefore comprise the same, or a different, topology of unit cells. The plate may be provided with one or more voids through which a fixation such as screws is applied. The size and location of the voids of the plate may be varied according to the desired use.

Figure 7 is an alternative view illustrating the use of a scaffold 130 together with plates on a broken clavicle.

Figure 8A illustrates a bone 150 with a defect 152. The defect may be malignant or otherwise unhealthy tissue that has been excised from the patient. Figure 8B illustrates a scaffold 140 according to an embodiment used to treat the defect 152. The scaffold 140 comprises a plurality of first components 80 and second components 84. Each of the first components 80 are generally cylindrical in shape and have a void which includes central portion 86 of a circular cross-section and a contiguous truncated wedge-shaped portion 82 that opens onto the outer periphery of the respective component 80.

In this embodiment, a fixation nail 88 is located within the central portion 86 of the void. The second component 84 (which acts as a cover) is shaped as a truncated wedge so that, when inserted into the wedge-shaped void portion 82 of the component 80, the central portion 86 remains. This allows the location, and subsequent protection, of the pin 88 as well as a vessel 90 within the scaffold 140. The fixation nail 88 is used to connect the two sections of bone together. The fixation nail 88 initially act as the load-bearing portion of the reconstructed tissue. Once the defective area 152 is reconstructed, the fixation nail 88 can be removed. Blood vessels 83 are used to vascularize the growing tissue. Having the modular components 80 and 84 allows the blood vessel 83 to remain intact during

implantation of the scaffold components. In some embodiments, the components 80 and 84 are loaded with a biological material prior to implantation. Biological material is to be interpreted broadly and can include tissue harvested from the patient, such as bone marrow, cells, extra cellular matrix, growth factors, and so on.

Although a wedge-shaped arrangement for the void and cover has been illustrated, it is to be realised that further embodiments may utilise alternate void and cover shapes, provided that the cover engages with a component to leave a void.

By providing adjacent components with voids formed therein located so that the voids of adjacent components align, it is possible to create a pathway so that a conduit may be laid through the scaffold. Furthermore, such voids can form ducts which create perfusion pathways through the scaffold. It is possible to then design such perfusion pathways according to physiological requirements. This can allow increased vascularisation and metabolite exchange to promote favourable conditions for tissue growth.

Figures 9A, 9B and 9C are schematic illustrations of a plate 160 which connect component 164 to bone 162. Although the manner of fixation is not illustrated here, it is to be realised that any known manner such as pins or screws may be used to fix the plate 160 to the bone 162 and/or to the component 164. Additionally, through additive manufacturing, component 160 can be manufactured in conjunction with component 164 as a single unit. As illustrated in Figure 9C, a second plate 166 is provided on the obverse side of the bone 162 to provide a more secure attachment than a single plate would.

Figures 10A, 10B and 10C are schematic illustrations of a port 170 attached to a component 172. The component 172 is interconnected with component 176 which is, in turn, attached to the bone 180. The port 170 is provided with a Luer lock 174.

Figures 11 A, 11 B and 11C illustrate how different components may be attached to one another to provide an implant. Figure 11A illustrates a scaffold implant 200 formed by attaching component 202 to component 204 and attaching component 206 to component 204. In this embodiment, the implant 200 further comprises two cover components 208 and 210. As illustrated, each of the components 202, 204 and 206 are formed with an H-shaped profile. The cover components 208 and 210 engage with the voids formed by the respective H-shaped profiles of adjacent components. The H-shaped profile of the components means that recesses 212 and 214 are provided at the proximal and distal ends of the scaffold implant 200.

Figure 11C illustrates a pin 220 supported by the components 202, 204 and 206. In addition to the interconnection means, the pin 220 can help to interlock adjacent components e.g. 202 to 204 and 204 to 206.

Figures 12A, 12B and 12C illustrate how different components may be attached to one another to provide another type of implant. Figure 12A illustrates an implant 250 formed by interconnecting component 252 to component 254 and interconnecting component 256 to component 254.

Figure 12C illustrates how a pin 260 may be accommodated within the implant 250. The pin 206 may be a fixation nail.

It should be noted that the structures of the components and resulting scaffold shown in Figures 11 and 12 are exemplary only and the disclosure is not limited to such structures.

Figure 13 illustrates a scaffold implant 300 according to an embodiment of the invention as shown in the blown-up portion. The implant 300 comprises components 302, 304 and 306 interconnected to one another. Figures 14 to 19 illustrate corresponding components 310, 320, 330, 340, 350 and 360 which may be utilised to construct scaffold implants according to embodiments. Each of the components illustrated in the respective Figures would constitute the basic unit of a set of components. So, for example, component 310 illustrated in Figure 14 may comprise a first set and, in a relatively simple form of an embodiment, a user may select two or more of components 310 to construct an implant. However, where the structural and functional requirements of the implant are more complex, a user may select components from different sets to construct the implant.

As illustrated in Figure 14, component 310 comprises struts 312 which meet at vertices to define a number of pyramids. The space between the struts 312 remains as an interstitial void. The dimensions of the interstitial void are determined by the required mechanical properties of the scaffold implant and the type of tissue to be regenerated. In the embodiment of Figure 14, the component is thereby made up of relatively large number of adjacent pyramids.

In general, components comprise repeated unit cells (such as the pyramid of component 310 of Figure 14). As illustrated in Figures 15 to 19, the thickness of the struts may be varied, as may be the manner in which the struts are arranged relative to one another, to define different unit-cell building blocks for the component.

In a further embodiment, not illustrated, the unit cells are shaped as the repeating portion of a periodic solid. For example, the shape of the unit cells may be the repeatable portion of any one of gyroid, double gyroid, diamond, neovious, Schwarz D, Schwarz P, icosahedron. In further embodiments, a combination of different shapes may be used.

Each of the components illustrated in Figures 14 to 19 is formed with a central void. When adjacent components are attached, the central voids will align, thereby forming a channel for perfusion.

The various embodiments of the scaffold implants described herein are exemplary only and the disclosure is not limited to these embodiments. Unless context makes it otherwise clear, features from the different embodiments of the scaffold components are interchangeable with one another.

Examples

Examples will now be used to describe non-limiting embodiments of the disclosure.

Example 1 - modular component having an injection port for bone

regeneration 1. Material and Method

1.7. Scaffold fabrication and preparation

Bioresorbable cylindrical scaffolds of medical grade poly-caprolactone

(mPCL), (outer diameter: 16 mm, height: 30 mm, inner diameter: 8 mm) were used in this study. The scaffolds are produced by fused deposition modelling (FDM). The scaffolds have a porosity of 70% and a 0/90° lay down pattern (Figures 20(a)-(d)). This architectural layout was particularly suitable for load bearing tissue engineering applications since the fully interconnected network of scaffold fibres can withstand early physiological and mechanical stress in a manner similar to cancellous bone. Moreover, the architectural pattern allowed the retainment of coagulating blood during the early phase of healing, and bone ingrowth at later stages. Prior to surgery, all scaffolds were surface treated for six hours with 1 M NaOH and washed five times with PBS to render the scaffold more hydrophillic. Scaffold sterilization was achieved by incubation in 70% ethanol for 5 min and UV irradiation for 30 min.

To enhance osteoinduction, mPCL scaffolds were coated with a layer of calcium phosphate (CaP). The coating process consisted of three steps: surface activation with alkaline treatment (sodium hydroxide (NaOH)); treatment with simulated Body Fluid 10x (SBF10x) to deposit the CaP; and post-treatment with NaOH. For 1 L of solution, reagents were dissolved in ddH20 in the following order: 58.430g NaCI, 0.373g KOI, 3.675g CaCI₂.2H₂0 and 1.016g MgCI₂.6H₂0. The next reagent (1.420g of Na₂HP0₄) was dissolved separately in 20 ml_ of ddH₂0 and added drop by drop into the main solution while maintaining the pH level at 4 by adding hydrochloric acid (HCI) 32% in order to avoid precipitation of calcium cations and phosphate anions. The tubes were first cleaned by immersion in 70% ethanol solution under vacuum for 15 min for the purpose of removing entrapped air bubbles, then the structures were immersed into pre-heated (37 °C) NaOH 2M and a 5 min vacuum treatment was performed at room temperature. For the rest of the activation steps, the scaffolds were placed at 37 °C for 30 min to accelerate the etching process. The scaffolds were then rinsed with ddH₂0 until the pH level dropped to approximately 7. Meanwhile, NaHC03 was added to the SBF10x solution until a pH of 6 was reached. This activated SBF solution was filtered (0.2 pm filter) and another 5 min vacuum treatment at room temperature was performed to ensure that the solution fully penetrated the tubes. The samples were thereafter placed at 37 °C for another 30 min. The solution was replaced with freshly activated and filtered SBF and placed again at 37 °C for 30 min. The tubes were rinsed in ddh O and then immersed in pre-heated NaOH 0.5 M for 30 min at 37 °C. Finally, the tubes were rinsed with ddhteO and the pH level was adjusted to approximately 7 and then dried overnight in a dessicator.

Prior to cell loading, the scaffolds were modified by making 3 large punch holes on the back side of the scaffold (diameter 4mm; Figure 20(c)) and 4 smaller holes on the front side (diameter 3mm; Figure 20(b)). The holes on the back were placed directly over the neuro-vascular bundle in the dorsal part of the bone defect, to allow the ingrowth of new blood vessels. The 4 holes in the front part were used for the delayed cell injection into the scaffold after 4 weeks and were placed next to the plate.

12 Animal study

Sixteen male sheep (40-50 kilogram, age 7-8 years) were used in this project (Table 1). The results of the experimental groups were compared to the autologous bone graft group (ABG). There were 8 animals in each group and all were euthanized after 12 months.

Table 1 : The research plan with details of the animal treatment groups. The time duration of this experiment was 12 months.

Group I Group II

mPCL-CaP + allogenic ABG

MPC (10x10⁷Cells)

T otal 8 8

1.3. Experimental Groups

- Group I

All scaffolds (mPCL-CaP) in this group were implanted into the defect site and the wound closed in layers. Delayed cell injection was performed four weeks after implantation of the scaffolds. Prior to injection, the allogenic ovine mesenchymal progenitor cells were obtained from Merino sheep that were not included in this study (allogenic cells). Bone marrow aspirates were obtained from the iliac crest under general anaesthesia. Total bone marrow cells (5-15 x 10⁶ cells/ml) were plated at a density of 10-20 x 10⁶ cells/cm² in complete medium consisting of low glucose DMEM supplemented with 10% FBS, 100 U/ml penicillin and 100 pg/ml

streptomycin. Cells were subsequently plated at a density of 10³ cells/cm². Two weeks before injection, the medium was changed to an osteogenic media (DMEM, 10% FBS, 100 U/ml penicillin and 100 pg/ml streptomycin, 10 pl/ml b- glycerophosphate, 1 pl/ml ascorbic acid and 1 pl/ml dexamethasone) to induce osteogenic differentiation.

- Group II

Autologous cancellous bone graft (ABG) was harvested from the left iliac crest. The surgical area was shaved and desinfected with 0.5% chlorhexidine red in 70% ethanol. A 5 cm incision was made following the iliac crest, the inserting musculature was carefully detached and the cortical bone of the lateral os ileum was fenestrated (2 x 2 cm) using a hammer and osteotome. Care was taken not to fracture the a/a ossis ilii. The resulting lid was carefully removed with a raspatory and the cancellous bone harvested utilizing a bone curette. Then, the lid was reinserted, the musculature was reattached with 2-0 Vicryl sutures (Ethicon), and the wound closed in layers. The closed wound was sprayed with Opsite (Smith and Nephew).

1.4. Cell delivery

Four weeks after implantation of the scaffolds, the allogenic MPCs were injected percutaneously into the scaffold. For this procedure, 10 x 10⁷ cells were detached from the cell culture flasks using a cell scraper so not to destroy the extracellular matrix. The resulting cell sheets were transferred to large petri dishes filled with standard media. The cell sheets were dissected using a sharp scalpel blade to get a smooth solution of the cells. Finally, the cell solution (4 ml) was equally transferred to four 5ml syringes under sterile conditions. Cell injection to the bone defects was performed under general anaesthesia and sterile conditions in the operating room.

The right hind limb was carefully shaved and thoroughly disinfected with 0.5% chlorhexidine solution red in 70 % ethanol. The animal torso and surroundings were covered with sterile sheets. The DCP plate was localized through the skin and another plate was placed from outside to identify the exact position of the plate holes. A sharp needle (14 gauge) was placed through the proximal hole of the scaffold. After that, three other needles were placed in the same way into the other holes.

The cell suspension (1 ml) from every prepared syringe was injected into the defect and the previously implanted scaffold starting at the proximal end of the defect. The wound was sprayed with Opsite (Smith and Nephew), covered with pads and bandaged (Vetrap, 3M). After recovery from anaesthesia, animals were allowed unrestricted weight bearing.

1.6. Radiography analysis

Throughout the study, x-rays were taken after 3, 6 and 12 months, to determine the time of bridging of the defect in the different experimental groups. Conventional x-ray analysis (3.2 mAs; 65kV) was performed in two standard planes (anterior-posterior and medial-lateral). At euthanasia, the gross morphology and mobility at host-graft junctions was clinically assessed and the findings carefully documented and photographed.

1.1. Biomechanical evaluation

To determine the integration of the scaffolds into the bone and the recovery of the biomechanical function of the affected tibias, biomechanical testing was performed.

1.8. Computed tomography (microCT)

After mechanical testing, both tibias were fixed in 10% neutral buffered formalin (NBF) and micro-CT scans of the defect and the control site were performed.

1.9. Histological analysis

After biomechanical testing and microCT analyses, tibial bone specimens were trimmed to 8 cm length and used for histological analysis. The detailed procedure for histological analysis was described in chapter III.

1.10. Statistical analysis

Statistical analyses for the biomechanical results and for the ct-scans

(microCT) were carried out using a two-tailed Mann-Whitney-U-test (SPSS 16.0, SPSS Inc.) and p-values are adjusted according to Bonferroni-Holm. Results were considered significant for p-values <0.05.

2. Results

2.1. Cell Isolation and Differentiation

Mesenchymal progenitor cells (allogenic MPC) were obtained from Merino sheep not included in this study via bone marrow aspiration from the iliac crest under general anaesthesia. Total bone marrow cells were plated at a density of 1-2 x 10⁷ cells/cm² in complete medium and cultured until they were confluent.

Two weeks before implantation, the medium was changed in all groups to an osteogenic media to induce osteogenic differentiation. Within a few days, the cells showed a clear response to the osteogenic induction media by a pronounced morphological. The cell morphology changed from an elongated shape to a compact cobblestone-like appearance. The potential of bone marrow derived MPCs to secrete a mineralised extracellular matrix was analysed by alizarin red staining. After 2 weeks of induction, all the cells had formed extensive amounts of alizarin red positive mineral deposits throughout the adherent layers.

2.2. Animal Surgery

In all animals, no postoperative infections or other complications were observed. The chosen 4.5 mm broad DCP was proven to be biomechanically sufficient to prevent implant failure. After 12 months, bone overgrowth was observed on nearly all plates. All animals were in good health and survived the experimental period, gaining weight in the months following surgery. In particular, the animals of the allogenic group showed no clinical signs of

implant rejection.

2.3. Radiographic analysis

Immediately after surgery and after 3, 6 and 12 months, conventional x-ray analyses in two standard planes (anterior-posterior and medial-lateral) were performed to assess bone formation. After surgery, the correct position of the scaffold, the plate and the screws were confirmed. After 3 months, bone formation was observed in the ABG group and the cell group starting from the dorsal part of the tibia where the defect is covered by the large muscle of the lower leg. The x-ray analysis after 6 months showed no loosening of the implants or movement of the scaffolds. Increasing bone formation was observed in the ABG group and the cell group. After 12 months, no implant loosening was observed in any animals.

Complete bridging of the defects in the ABG group and the cell group was observed in all animals (Figure 21(a) and Figure 21(b)).

2.4. Biomechanical testing

Biomechanical testing was performed on all specimens after 12 months. Biomechanical testing revealed a higher torsional stiffness (TS) and a higher torsional moment (TM) for the cell group compared to the scaffold only group. The results were not statistically significant. The ABG group showed the highest results for both, torsional moment and torsional stiffness, with significantly higher results compared to the scaffold only group and no significantly higher results compared to the cell group (Figure 22 and Figure 23).

2.5. Computed tomography (microCT)

MicroCT analysis confirmed the trend of the results from the conventional xray analysis regarding union rates and the amount of new bone formation. In the 3D reconstructions, the groups showed large amounts of new bone formation in the defect with a complete bridging of the defect. The mean values of newly formed bone in the MPC group was slightly higher compared to the ABG group without significant differences (p=0.284) (Figure 24).

Example 2

A defect located midshaft in a tibia was completely removed to form anterior and posterior tibia segments. The defect size was approximately 26 mm in diameter and 110 mm in length. The defect in the tibia was a result of a bone tumour.

Three modular scaffold components each having a length of about 50 mm,

OD about 22mm and an ID of about 13mm loaded with bone marrow in combination with osseous particles were removed from the patient during intermedullary canal reaming using a reamer-irrigator-aspirator. The three modular scaffold components were then slid onto a fixation nail (12 mm diameter) to be coaxially arranged thereto. Each of the modular scaffold components had protrusions at one end that were receivable in corresponding recesses on adjacent components. The fixation nail having the coaxially arranged components was used to fix the anterior and posterior segments of the tibia. The fixation nail was secured to respective medullary cavities of the anterior and posterior segments of the tibia.

Once the fixation nail was secured, adjacent components were then interlocked with one another by engaging the protrusion of one component with the recess of an adjacent component. The surgical site was then closed.

Postoperatively, the patient was made immediately weight-bearing as much as tolerated. Serial follow-up radiographs show interval consolidation of patient bone graft, and at 1-year postoperatively the patient is able to work and take part in normal daily life without an assistive device.

Example 3

The lower quarter of a femur shaft was removed to provide clear margins surrounding a defect. The lateral and medial epicondyles were retained. An anterior and a posterior modular scaffold component that occupies the space of the removed femur was loaded with bone marrow in combination with osseous particles were removed from the patient during intermedullary canal reaming using a reamer- irrigator-aspirator. The anterior and posterior components were implanted into the patient and were interlocked to one another. A fixation plate was then installed to stabilise the femur and the interlocked components were secured to the fixation plate using sutures that wrapped around the fixation plate and interlocked components. The surgical site was then closed.

Postoperatively, the patient is made immediately weight-bearing as much as tolerated. Serial follow-up radiographs show interval consolidation of patient bone graft. Three months postoperative the patient was walking without crutches with full load being applied through the femur with knee movement of 120°. At six months postoperatively, the patient is able to work and take part in normal daily life without an assistive device. Example 4

A bone defect in a tibia due to a tumour was removed but an anterior margin of the defect was preserved. A titanium fixation nail having a diameter of 9 mm and a length of 360 mm was fixed in the medullary cavity to the tibia. Four modular scaffold components having an 9 mm ID, 24 mm OD and a length of 23 mm, 41 mm, 51 mm and 61mm were secured around the fixation nail. A side of the components were omitted so the wall of the components extends around approximately 270° to define a contiguous truncated wedge-shaped portion that opens onto the outer periphery of the respective component thus allowing each component to be clipped onto the fixation nail. The modular scaffold components used in this study were similar to that of component 80 described in Figure 8.

Prior to implantation, bone marrow in combination with osseous particles were removed from the patient during intermedullary canal reaming using a reamer- irrigator-aspirator, and the material obtained from the reamer-irrigator-aspirator was then pressed into each component.

Once the components were clipped onto the fixation nail, a suture was wrapped around each component and the anterior margin to secure each component to the fixation nail.

X-ray analysis showed that 6 months postoperatively new bone formed along the segmental defect inside the modular scaffolds components.

In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word“comprise” or variations such as“comprises” or“comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the device, system, kit, and method.

Claims

1. A system for constructing a tissue scaffold comprising at least a first set of modular components, each component of the first set having substantially the same shape, wherein the components of the first set are configured to allow interconnection to form the tissue scaffold.

2. The system according to claim 1 wherein each component comprises a network of interconnected voids arranged to enable passage of a fluid or a mechanical element through or across the component.

3. The system according to claim 2 wherein the components comprise a plurality of interconnected structs which are configured to form the network of interstitial voids, and wherein the struts define a pattern comprising a repetition of a unit cell.

4. The system according to claim 3 wherein the unit cell is of a shape comprising any one of: gyroid, double gyroid, diamond, neovious, Schwarz D, Schwarz P, icosahedron.

5. The system according to any one of the preceding claims further comprising a second set of modular components, each component of the second set having substantially the same shape, wherein the components of the first set have a different shape, configuration or structure to the second set.

6. The system according to any preceding claim further comprising at least one custom component, wherein the custom component is manufactured by an additive technique, the custom component being of a shape, configuration or structure different to the first or second components.

7. The system according to any preceding claim further comprising at least one port component, wherein the port component comprises a port arranged for introduction of fluid.

8. The system according to any preceding claim wherein the modular components of the first set comprise one or more ducts passing through each component, the ducts being arranged so that ducts of interconnected components are in fluid communication with one another.

9. The system according to claim 8 wherein at least two components of the first set of modular components comprise one or more ducts, where each of the at least two components have ducts that define the same path through the respective components.

10. The system according to claim 8 or 9 wherein at least two components of the first set of modular components comprise one or more ducts describing different paths through the respective components.

11. The system according to any preceding claim wherein the

interconnection between components of the first set comprises one or more of: a tongue and groove arrangement, a snap-fit arrangement, hook and loop

arrangement.

12. The system according to any preceding claim wherein the components of the first set each comprise a void so that, when the components interconnect, corresponding voids at least partially align.

13. The system according to claim 12 wherein the first set further comprises one or more covers, wherein each cover is shaped to engage with the void of a respective component of the first set to thereby create an enclosed void within the respective component.

14. The system according to claim 13 wherein the enclosed void is suitable for housing one or more of: a pin or a conduit.

15. The system according to any preceding claim wherein the components comprise biodegradable material.

16. A method of forming a scaffold for tissue growth comprising:

interconnecting two or more components from said first set.

17. The method according to claim 16 further comprising obtaining an image of a defect, designing a scaffold with reference to the image and constructing the scaffold by interconnecting two or more components from the first set of modular components.

18. The method according to claim 17 wherein the step of designing the scaffold occurs remotely from the step of obtaining the image of the defect.

19. The method according to any one of claims 16 to 18 further comprising: designing at least one custom component having a shape different from components of the first set, manufacturing the custom component utilising an additive

manufacturing technique and interconnecting the custom component to a component of the first set.

20. The method according to claim 19wherein the step of designing the custom component occurs remotely from the step of manufacturing the custom component.

21. The method of any one of claims 16 to 20, wherein the step of providing the first set of modular components comprises providing the system of any one of claims 1 to 15.

22. A method of forming a scaffold for tissue growth comprising:

providing system for constructing a tissue scaffold according to any of claims 1 to 15; and

interconnecting two or more components from the first set of the system.

23. The method according to claim 22 further wherein the modular components of the first set comprise one or more ducts arranged so that ducts of interconnected components are in fluid communication with one another and wherein at least two components of the first set of modular components comprise one or more ducts describing different paths through the respective components, the method further comprising the steps of:

designing a duct system for the scaffold; and

24. The method according to claim 22 or 23, wherein the modular components are loaded with a patient-specific biological material prior to

interconnection of the modular components.

25. The method according to claim 23, wherein the patient-specific biological material is loaded into the modular components prior to implantation into a patient.

26. The method of any one of claims 22 to 25, wherein the modular components are implanted into a patient prior to interconnecting two or more components from the first set of the system.

27. The method according to any one of claims 22 to 26, further comprising the method according to any one of claims 16 to 20.