3D Segmentation of Intervertebral Discs: From Concept to the Fabrication of Patient-Specific Scaffolds

Figures & data

Figure 1. Representation of the envisioned patient-specific intervertebral disc tissue engineering strategy with the highlighted role of the present study in the center.

The data obtained from medical imaging of the patient's intervertebral disc (IVD) are segmented and processed into a 3D model to be used in 3D printing the selected biomaterial(s) of a patient-specific IVD implant. Different types of biomaterials can be used for reproducing the annulus fibrosus and nucleus pulposus. The autologous cells are isolated from the patient, proliferated in vitro and introduced into patient-specific scaffold in the presence of growth factors and mechanical stimulus. The tissue engineered patient-specific construct cultured in vitro can be then implanted into the patient.

AF: Annulus fibrosus; IVD: Intervertebral disc; NP: Nucleus pulposus.

Figure 2. MRI images of the patient.

Images taken from the (A) axial, (B) sagittal and (C) coronal planes. The L1–L2 intervertebral disc was indicated by the white rectangle (scale bars: 4 cm).

Figure 3. The segmentation process.

Left: L1–L2 intervertebral disc of the patient. Right: the 3D model of the intervertebral disc after completing the segmentation (scale bars: 2 cm).

Figure 4. The final smoothed 3D model of the L1–L2 intervertebral disc of the patient.

The numbers correspond to millimeter.

Figure 5. Patient-specific 3D intervertebral disc model, its layers, and the layer-wise alternating strand directions.

(A) The wireframe 3D model of the intervertebral disc (IVD) of the patient; (B) the layers of the 3D IVD model after slicing of the 3D model into layers with colors changing from red to blue indicating the top and the bottom layer, respectively; the illustration of the alternating layers in the three architectures: architectures A–C with (C) 0°/90°, (D) 0°/60°/120° and (E) 0°/45°/90°/135° strand structures, respectively.

Figure 6. Photographs of the 3D printed intervertebral disc scaffolds with three different internal architectures.

(A) Architecture A (0°/90° strand structure). (B) Architecture B (0°/60°/120° strand structure). (C) Architecture C (0°/45°/90°/135° strand structure) (scale bars: 1 cm).

Figure 7. The μ-CT images of the 3D printed samples with the three different internal architectures.

(Top row: A–D) A (0°/90° strand structure), (middle row: E–H), B (0°/60°/120° strand structure) and (bottom row: I–L) C (0°/45°/90°/135° strand structure): the x-ray images (A, E and I), the 2D reconstructed microcomputed tomography images (B, F and J), the 3D reconstructed images showing the structures from side (C, G and K) and top (D, H and L) (scale bars: 1 mm).

Figure 8. The pore size distribution of the samples with the three distinct internal architectures.

(A) (0°/90° strand structure), (B) (0°/60°/120° strand structure) and (C) (0°/45°/90°/135° strand structure).

Table 1. The structural and morphometric properties of the scaffolds with the three distinct internal architectures of A (0°/90° strand structure), B (0°/60°/120° strand structure) and C (0°/45°/90°/135° strand structure).

Internal architecture	A	B	C
Porosity (%) M(SE)	45.8 (0.9)	45.8(1.3)	44.1 (1.0)
Mean pore size (μm) M(SE)	600.8 (3.8)	555.3 (9.0)	435.7 (2.2)
Interconnectivity (%) M(SE)	99.2 (0.1)	99.0 (0.1)	99.1 (0.1)

M: Mean; SE: Standard error.