Aim 1: Provide Immediate Support

Basic Design Fix joint using scaffold

Fill in the bone cavity completely. Match shape using CT scan Exact shape discussed

later Need extra support

around the edges Metal Socket and contact

with bones.

Aim 1: Provide Immediate Support

Extra support comes from BMP in scaffold Most dense around the critical area Fastest bone growth in critical area

Aim 1: limitations and failures Forces on joint not always in

one direction For sake of discussion, think

2D first. Force acting on center of the

scaffold in the direction of the femoral neck is risky

May not always be safe for immediate walking for the patient

Aim 1: Alternative approach Redistribute BMP gradient

Extra “pillar” in the affected region. Supports the weight applied through the ball joint

better.

Aim 2: provide improved bone growth Design

BMP must cover all area by matching the patient’s bone shape Use CT scan Rapid prototype the scaffold.

BMP must avoid reconstructing bone too quickly Osteoblasts and Osteoclasts

Rapid Prototyping Cannot just “print” the scaffold Using casting method

Aim 2: provide improved bone growth As mentioned before…

BMP gradient Most dense area used for immediate support Least dense area used for slower but complete

bone growth in inner region Go slow to reduce risk!

Aim 2: Limitations and Failures Limitation in using BMP BMP may not be suitable for all patients

Case: patients with extra large amount of bone loss

Proportionally, these patients will lose more osteoblasts

Alternate approach Attempt reducing amount of BMP used.

No change in gradient Reduce overall usage of scaffold

Aim 2: Limitations and Failures 2 Limitation in application

The scaffold match patient’s bone by shape, but how to match it physically?

There are some case where you cannot physically insert the scaffold

Aim 2: Alternate Approach 2

“Simplify” the shape of the cavity using cement

Would require trimming of scaffold Double CT scan may be necessary

Aim 2: Limitations and Failures 3 Limitation in application Can fail to insert it into patient if correct

rotation is not recorded

Aim 2: Alternate Approach Limitation in application

Not so bad.

Would need another device to correctly store the rotation in z-axis for the scaffold

Or make an “indicator” on the scaffold during rapid prototyping process.

Aim 3: Reduce Overall Number of Surgeries 1. Successful bone growth would reduce risk

of returning to the hospital 2. Removing need to remove any of the

component of scaffold reduce risk and need of returning to the hospital Achieved this by making the scaffold using

biodegradable material

Aim 3: Reduce Overall Number of Surgeries Recall

Rate of bone growth = Rate which scaffold bio-degrades

Scaffold completely gone without causing excessive volume of BMP + scaffold in the joint for the patient

Limitations and Failures Scaffold itself is not in gradient At one point in time or space, amount of scaffold

remaining may too little to hold BMP

Aim 3: Alternative Approach Lower rate of bone growth

Reduce overall density of BMP in scaffold It is safer if the scaffold remains a little bit

longer than necessary