![The Kugel Ball is a 60,000 lb stone ball resting on a concave cup. However, with a thin layer of water below it, it can be easily pushed and rotated.[1]](https://s3-us-west-2.amazonaws.com/secure.notion-static.com/9826f8da-f8cc-43fa-8f76-d35f841ae834/W1siZiIsInVwbG9hZHMvcGxhY2VfaW1hZ2VzLzU2NDM0MzJiYmQzNjYxMmE1OV82MjQwNzQ0ODU4XzFlNjZjNzQwMTdfei5qcGciXSxbInAiLCJjb252ZXJ0IiwiIl0sWyJwIiwiY29udmVydCIsIi1xdWFsaXR5IDgxIC1hdXRvLW9yaWVudCJdLFsicCIsInRodW1iIiwiNjAweD4i.jpg)
<aside> ❓ Our team was tasked to design a hip implant that incorporates new forms and materials to reduce or reverse the effect of aseptic loosening. To achieve this, the implant should generate as little wear debris as possible. In addition, the implant should contain biocompatible materials to promote osseointegration. Lastly, modifications of surgical fixation should also be considered.
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<aside> 💡 Adhering to these guidelines, we went through multiple ideas and materials selections until we arrived at the final design of the Kugel Hip. The Kugel Hip was inspired by the Kugel Ball as it replaces the femoral head with a perfectly spherical ball ballast enclosed by two cups. Materials such as TNTZ, porous tantalum, graphene and vitamin E highly crosslinked polyethylene are applied to various components of the implant to reduce the generation of wear debris and promote osseointegration. We have also improved the surgical fixation process to reduce the risk of infection and extend implant life.
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The Kugel Ball is a 60,000 lb stone ball resting on a concave cup. However, with a thin layer of water below it, it can be easily pushed and rotated.[1]
Wider femoral stem to compensate for decreased bone mass.
Free-floating ball inside the femoral head acts as ballast to better simulate non-prosthetic motion.
Screws for surgical fixation doubled for increased stability
Ring added to lower hemisphere to prevent joint dislocation
| Implant Component | Materials | Justification |
|---|---|---|
| Femoral Stem Core, Lower Cup, Ball Ballast | Ti-29Nb-13Ta-4.6Zr (TNTZ) | |
| 65 GPa elastic modulus | ||
| 1192 MPa UTS | ||
| Lower wear than typical Ti-6Al-4V Alloy | ||
| High corrosion resistance | TNTZ has an elastic modulus that is close to the human bone, which reduces stress shielding. | |
| High ultimate tensile strengths that can withstand higher body weight. Maintains the structural integrity of the bone. | ||
| TNTZ will not degrade under inflammatory conditions. | ||
| Outer Femoral Stem | Porous Tantalum | |
| Repeating dodecahedral pore shape mimics bone | ||
| 20 GPa elastic modulus | ||
| Forms self-passivating Ta2O5 layer | The porous surface allows for good osseointegration. | |
| Low elastic modulus reduces stress shielding, preventing further bone loss. | ||
| High corrosion resistance. PHA coatings can be applied to avoid bacterial adhesion. | ||
| Inner Cup Lining | PSPMK Brushes Grafted with PNIPAAmm Microgel | |
| Ionically charged, hydrophilic | ||
| Low coefficient of friction | The PSPMK reduces the wear between the ball ballast and the cups. | |
| PSPMK is load-responsive, coefficient of friction adjusted based on applied stress. | ||
| PSPMK also has antibacterial effects. | ||
| Acetabular Cup | Graphene and Vitamin E Highly Crosslinked Polyethylene | |
| Vitamin E prevents oxidation of polyethylene | ||
| Good wear and improved mechanical and fatigue properties | Atomic properties of graphene oxide reduce wear rate by 83% | |
| Vitamin E reduces the need for future revision surgery. It is important in protecting cells from oxidative stress, regulating immune function, maintaining endothelial cell integrity, and balancing normal coagulation. | ||
<aside> 1️⃣ The first surgery will remove the old tissue and weakened bone and apply antibiotics. Once the hip is cured of infection, a second surgery is performed to insert the new implant
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<aside> 2️⃣ Revision implant stem is longer and wider to replace lost bone. Novel collagen is added to replace the lost cartilage. This will prevent infection and reduce pain.
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<aside> 3️⃣ The number of screws on the acetabular cup is doubled to provide stability and longevity while spreading the load. The screws will not go through the original screw holes for stability.
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<aside> 4️⃣ In addition to the implant’s porous surface, stem cell is injected to the scar. The treatment is expected to stimulate bone regeneration.
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Reducing the risk of another hip revision surgery requires: Daily physical activity Substantial diet changes