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SAB: Reconstruction of extensive cranial bone defects by using three dimensional textile scaffolds

Concept

fig.1: concept for the reconstruction of extensive cranial bone defects with 3dimensional textile scaffolds.

The implant concept is based on the BMBF-project „novel conception for tissue engineering of long bone defects based on biologised textile scaffolds“. This long-bone implant is allready approved in a big animal experiment on sheep in a long term study.

An implant for padding a cranial bone defect must exhibit a cylindric geometry with a diameter identical to the defect diameter and a height related to the thickness of the cranium. Also an initial structural integrity (prime stability) of the textile scaffold is required to avoid subsidence of the implant and subsequent cerebral damage („sinking skin flap syndrome“).

The challenge for embroidery technology and scaffold design in this project is comprised in the creation of 3dimensional volume bodies with tailored porosity and the postulated mechanical resilience of the textile implant.

Several options are given to generate 3dimensional structures by embroidery technology. Porosity and poredistribution of the volume body can be influenced by varying the procedural method. Objective of the IPF project part is, to characterize scaffold properties like porosity, poresize distribution and prime stability acording to the procedural method and divers textile parameters and, by collaborating with the project partners TU-Dresden and Fa. Catgut, finding out the optimum textile structure for the reconstruction of extensive cranial bone defects.  

Indication

Cranial bone defects originate from different sources. Open craniocerebral injury caused by accident are comparatively seldom. In the majority of cases a targeted removal of a circular piece of cranial bone with defined diameter is performed (cranio ectomy). Cranial aperture is required for intracranial surgery indicated by  ex. cerebral tumor or to regulate the intracranial pressure, that can increase immoderately after covered craniocerebral injury or ischemic cerebral infarct (apoplexia) by accumulation of hematoma or edema.

Principle

Scaffolddesign

One challenge is given by the creation of 3dimensional volume bodies. Embroidery technology enables the generation of tailored structures by entangling needle- and shuttle thread in a quasi- 2dimensional manner (control of x- and y- axis, z-axis comparatively small and not controllable) Collaborating with Fa. Möckel to procedural methods are investigated.

fig. 2: increasing yarn density in the interior space of the scaffold by processing repeated layers one upon the other.

Design with density gradient

Repeated layers, parted by a ply of PVA-fleece as spacer, can be processed one upon the other. In the interior layers the yarn portion accumulates by inserting the same amount of stitches with each layer. A gradual decrease of the yarn density appears in the volume of the scaffold (fig. 2).

fig. 3: uniform poresize distribution by piling up several individual layers.

Design wiht a uniform poresize distribution

To aquire a uniform poresize distribution, the layers are processed separately and clamped in a further procedural step. Therefore the layers are piled up to a stack and bonded by an embroidery layer with radiating stitch assembly (fig. 3)

Characterisation

The characterisation of the poresize distribution and volume ratio is performed by computer aided image analysis. Visualisation of the scaffold structure is achieved by the concept, scetched in figure 4.

fig. 4: characterisation of poresize and poresize distribution by computer aided image analysis. Scetch of the concept for visualizing the 3dimensional textile structure.
fig. 5.: cross sectional perspectives in different axes

A 3dimensional presentation of the textile volume body is possible (fig. 5)

 
SAB: "cranial bone"
SAB: "Schädelknochen"

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