Reconstruction of spongy bone
using coral

In humans: A biological material must have the following characteristics:

• It must be bioresorbable (gradual complete disappearance)

It can be seen in this image that the coral implanted in the greater trochanter has disappeared just over a year later.

Note the complete disappearance of the natural coral in two years

• It must be biocompatible: there must be no difference - once resorbed - between the bone and the bomaterial.

You can see that it is impossible to distinguish the implanted zone from the non-implanted bone
in the spongy bone of this patient's femur after disappearance of the biomaterial.

• It must be quantifiable: it must increase BMD significantly

In this case, there is a steep increase in BMD.

Verification on an anatomical specimen must show the presence of biomaterial if it is only partly resorbed. This is shown here on a CT scan of an anatomical specimen. Note the layout in the form of trabeculae forming an arch, which is characteristic of normal bone, shown here in an implanted hip.

Right hip not implanted: note the size of the bony void, the complete disappearance of bone trabeculae.
The remaining bone trabeculae are the site of microfractures (arrows on left slide)
which have been described by Maurice Michel Forest.

Implanted left hip : note the partial persistence of the coral (on left slide).
The bone reconstruction with redevelopment of good arched trabecular
characteristic of the anatomy of the upper end of the femur.

The biomaterial must behave like a normal bone, i.e. reduce regularly with time in the same proportions as the physiological reduction. BMD measurements in the following table confirm this reduction with longitudinal monitoring for more than 6 years. The BMD and date in months (m) or years (y) is given for each post-operative examination.

Patient Age Date of graft Post-Op 1 Post-Op 2 Post-Op 3 Post-Op 4 Post-Op 5 Post-Op 6
C.J. 66 3/07/92 0,559 10 m 0,541 2 y - - - - - - - -
T.S. 76 28/01/92 0,648 2 m 0,641 3 m - - - - - - - -
M.M. 79 2/10/92 0,566 4 m 0,852 7 m 0,549 20 m 0,416 40 m - - - -
M.O. 80 24/07/92 0,853 6 m 0,852 1 y 0,742 2 y 0,667 4 y 0,645 5 y 0,636 6 y
V.L. 83 2/10/92 0,408 3 m 0,494 1 y 0,498 2 y - - - - - -
O.G. 84 4/12/92 0,597 3 m 0,589 6 m 0,596 1 y 0,588 18 m - - - -
V.B. 87 27/11/92 0,868 3 m 0,803 2 y - - - - - - - -
G.A. 94 27/10/92 0,806 3 m 0,773 6 m 0,691 1 y 0,668 14 m 0,622 22 m 0,541 54 m

Histology of natural coral in a bone medium

This patient died at the age of 101 and had suffered a fracture of the femoral neck at the age of 95.

She no longer left her room and was bedridden because of an inoperable brain tumour. Examination of both hips 6 years after death revealed the transformation of the coral in the fractured hip which had received a graft.
Bone densitometry performed on post-mortem samples from both femurs showed the increase in bone mineral density on the implanted side. The bone mineral density of the left hip reflects the bone's pre-existing bone mineral density plus that of the bone neoformed from coral and that of the remaining coral, whereas the bone mineral density of the right hip reflects the remaining bone.

On the right hand side, the section of femur shows almost complete disappearance of the bone lamellae, replaced by fat. There is no architectural organisation remaining.

Microscopic examination revealed the same phenomenon, i.e. the extreme rarity of bone lamellae – here a bone lamella is coloured red-brown. It has lost all connection with the adjacent bone lamellae. It is surrounded by adipose cells. The more advanced the osteoporotic disease, the fewer bone lamellae there are.

On the left-hand side, examination of bone cross-section with the naked eye shows, firstly, an empty space in the middle corresponding to surgical material surrounded by several spheres, some of which are clearly visible and in contact with the material, with others more or less destroyed, in contact with the adjacent bone.

Cross-section parallel with the main axis of the femoral neck

1 -
Surgical material (empty space)
2 - Coral spheres in contact with the material
3 - Coral spheres in contact with spongy bone

Section perpendicular to the axis of the femoral neck

The natural coral spheres have remained intact because, in contact with the metal which has no vascularisation, they have been surrounded by tissue with no vessels – a sort of tissue packing.

On the other hand, the coral in contact with the bone and vessels attached to it, has been colonised by bone cells which have resorbed the biomaterial.

Work performed by the Biomatech Laboratory

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