3D SEE® Trabecular Hip Implant System: The Design Concept in Two Questions

With the trend toward younger patients undergoing total hip arthroplasty (THA), the number of THA revisions continues to rise. Clinical literature reveals a significant increase in hip arthroplasty revision rates among younger, more active patients. However, the 15-year prosthetic survival rate remains at around 60%.

Younger patients undergoing total hip arthroplasty (THA) have higher expectations and demands for postoperative quality of life. The challenge in clinical research is improving hip prosthetics' overall survival rate while effectively restoring hip joint function.

Currently, concerns about hip prosthetics mainly revolve around the following aspects:

1. Why is the prosthetic survival rate relatively low?

2. What can we do in the prosthetic design phase?

Let's take a look at the solutions offered by the JUST Medical 3D SEE® Trabecular Hip Prosthesis System.

The 2016 data from multiple national registries showed that aseptic loosening is the primary reason for postoperative revisions.

Currently, research into aseptic loosening is extensive and can be broadly categorized into mechanical and biological mechanisms, both at the foundational and clinical levels.

Mechanical mechanisms play an initiating role in the occurrence of aseptic loosening and primarily involve two aspects:

1. Micro-Motion:

Excessive micro-motion at the implant-bone interface can affect the formation of a tight bond between the bone and the implant. When the micro-motion at the implant-bone interface exceeds 150μm, it inhibits bone formation, leading to the formation of fibrous tissue. Micro-motion can also directly result in bone resorption, increasing the risk of aseptic loosening.

The JUST Medical 3D SEE Trabecular acetabular cup and the 3D SEE trabecular stem-sleeve assembly both utilize 3D printing electron beam melting technology, creating a single integrated structure. The trabecular layers of the cup and sleeve have multiple pores, resulting in a high friction coefficient of 1.08, which minimizes micro-motion.

Furthermore, both the 3D SEE Trabecular acetabular cup and the 3D SEE trabecular stem-sleeve assembly feature a three-dimensional porous structure with a high porosity rate ranging from 75% to 80% and pore diameters between 600-800μm. This design ensures excellent bone ingrowth, guaranteeing the implant's long-term stability after placement.

The 3D SEE trabecular stem-sleeve assembly for the femoral component features a tapered design in both the head-neck junction and the sleeve-stem junction, minimizing micro-movement.

2. Stress Shielding

The Digas study found that stress shielding contributes to the loss of bone density around press-fit acetabular cups without bone cement, leading to implant loosening. Additionally, some clinical studies indicate that the proximal femur is a high-risk area for stress shielding.

The 3D SEE trabecular acetabular cup and trabecular sleeve, with a porosity rate of 75%-80%, have an elastic modulus similar to cancellous bone, minimizing stress shielding.

The 3D SEE trabecular modular femoral stem is designed to ensure proximal medullary filling through various combinations of trabecular sleeves, promoting stress distribution to the proximal end and reducing stress shielding. Additionally, the distal coronal plane of the stem features a "tuning fork" design to lower rigidity and minimize stress shielding.

The biological mechanisms play a significant role in the later stages of aseptic loosening of artificial joints. This involves various levels of impact, including particles, cells, molecules, and more. Primarily, the polyethylene particles generated from prosthesis wear induce macrophages, ultimately leading to bone resorption.

JUST Medical utilizes internationally recognized low-friction interface prostheses in clinical practice: ceramic heads paired with highly cross-linked liners. This combination ensures safety while minimizing wear.

The design of the 3D SEE Trabecular Hip Prosthesis System, taking into account both mechanical and biological mechanisms, minimizes the occurrence of aseptic loosening, ensuring the long-term survival of the prosthesis and helping doctors provide patients with a healthy life!