CHRONO THR

Cementless THR – Total Hip Replacement

CHRONO, a revolutionary press-fit hip prosthesis, has been engineered to overcome the limitations of existing prosthetic solutions and elevate clinical performance to new heights.

This state-of-the-art prosthetic system, derived from cutting-edge human-inspired technology, aims to streamline the implantation procedure, thereby reducing surgical complexity and optimizing intervention times.

Unlike in humans, where hip prostheses are typically reserved for older individuals, in dogs, this procedure is often performed on young patients afflicted with severe and otherwise untreatable hip dysplasia. As the number of hip implants in young and highly active patients continues to rise, it becomes increasingly critical to proactively prevent and minimize biomechanical complications such as joint instability and post-operative dislocation. Additionally, the prosthesis must exhibit exceptional durability, ensuring minimal mechanical wear over an extended lifespan.

CHRONO sets a new standard in hip prosthetics, offering a comprehensive solution that addresses the unique challenges faced by both surgeons and patients alike.

Indeed, CHRONO has been studied and designed with specific objectives in mind, aimed at delivering outstanding performance and durability:

  • Primary stability and rapid osteointegration are achieved through the presence of trabecular structures on both the acetabular cup and the femoral stem, ensuring a secure fit and promoting efficient bone integration.

  • Longevity is a key focus, achieved through the utilization of ultra-high-molecular-weight polyethylene (UHMWPE) with reduced wear properties. This UHMWPE is further enhanced with the addition of Vitamin E, a natural stabilizer and antioxidant, effectively preventing periprosthetic osteolysis.

  • Superior joint mobility and enhanced resistance to dislocation are facilitated by a dual mobility system, enabling a wide range of articulation angles up to 65°. This innovative design provides improved functionality and stability for the patient.

  • Easy revision options are incorporated into the design, allowing for the straightforward replacement of the polyethylene component (insert-head) when necessary.

The CHRONO system consists of four engineered components:

  • Femoral stem.

  • Acetabular cup.

  • Dual mobility articulating insert.

  • Femoral head.

 Stem and Cup with Trabecular Integration Interface

The trabecular structure is designed to ensure maximum primary stability and achieve the fastest and most effective osteointegration to date.

The trabecular structure of the CHRONO prosthetic system closely mimics that of bone tissue, exhibiting a porosity and compressive modulus of elasticity comparable to cancellous bone.

Through additive manufacturing techniques, components are produced layer by layer using a 3D CAD file, allowing for the creation of a continuous and fully integrated porous material. It is important to note that this is not a mere coating but a continuous structure forming the prosthetic components of the CHRONO hip prosthetic system.

The presence of the trabecular structure enhances primary stability and optimizes forces at the interface with both cancellous and cortical bone, thereby improving biological fixation and load distribution to the surrounding bone tissue. The high level of primary stability provided by the trabecular structure eliminates the need for screws or similar fixation systems to maintain the stability of the prosthesis in the short and long term.

Double Mobility & Anti-dislocation System

The concept of double mobility involves the utilization of an acetabular cup in which a mobile insert articulates, and in turn, the femoral head articulates within the insert.

The double mobility cup, initially introduced in human medicine to mitigate the risk of dislocation, operates on the principle of employing a larger diameter femoral head to enhance implant stability.

The primary objective of the dual articulation system is to provide maximum joint range of motion by utilizing larger head sizes, thereby reducing the risk of dislocation while concurrently minimizing wear associated with larger heads.

Moreover, the double mobility system allows for increased flexibility in angulation during installation, ensuring optimal functionality and stability with a broader range of motion compared to traditional systems.

The dual mobility acetabular component enhances hip articulation (ROM). The system operates through the design of two distinct articulations. In the first articulation, the femoral head is "captured" but remains mobile within the polyethylene (PE) insert, serving as a mechanical bearing.

The overall range of motion of the Chrono double mobility system is determined by the movement of the femoral head articulating within the mobile polyethylene insert, further complemented by the motion of the insert itself, which begins to articulate with the metal cup only when the femoral stem neck engages with the insert, causing it to rotate within the surface of the TiN-coated cup.

Chrono Femoral Stem

The Chrono femoral stem is manufactured entirely using additive manufacturing technology, specifically selective laser melting of titanium Ti6Al4V powder (ISO 5832/3, ASTM F1472, ASTM B348). It is characterized by its quadrangular cross-sectional shape, which provides torsional strength, ensuring primary implant stability and facilitating osteointegration. The tapered and chamfered diaphyseal region promotes secure insertion into the medullary canal and optimal stem alignment. The absence of sharp edges eliminates the risk of stress concentration on the distal cortices.

Moreover, the presence of trabecular structure in the metaphyseal region of the stem prevents subsidence phenomena.

Finite Element Analysis (FEA) conducted on the Chrono femoral stem demonstrates that in the most highly stressed area (femoral neck), the forces acting on the load-bearing section are significantly below the material's yield strength.

The Chrono stem is available in various sizes to accommodate the femoral anatomy of the target patient population.

Chrono Acetabular Cup

The Chrono acetabular cup is manufactured entirely using additive manufacturing technology, specifically selective laser melting of titanium Ti6Al4V powder (ISO 5832/3, ASTM F1472, ASTM B348). At the equatorial level, it is characterized by the presence of trabecular structure, which allows for achieving primary stability and secondary biological fixation through bone regrowth.

The cup exhibits a hemispherical geometry with polar flattening, resulting in an equatorial distribution of forces acting on the cup (with slight oversizing), enhancing implant stabilization and leveraging the surface characteristics that interact with the host tissue.

The polar flattening enables the insertion of the cup, allowing it to advance until it reaches contact with the host tissue at the equatorial level, ensuring primary stability.

The inner surface of the cup is smooth, ensuring seamless sliding of the dedicated polyethylene insert. The cup is coated with a thin ceramic layer of titanium nitride (TiN) obtained through the physical vapor deposition (PVD) technique, ensuring enhanced surface hardness and improved wear resistance.

The Chrono cup is available in various sizes to accommodate the femoral anatomy of the target patient population.

Chrono Insert

The insert is composed of ultra-high molecular weight polyethylene (UHMWPE) (ISO 5834/2) supplemented with Vitamin E.

α-tocopherol, or Vitamin E, serves as a natural stabilizer and antioxidant in UHMWPE polyethylene. It enhances the tribological properties, reducing polyethylene wear and preventing periprosthetic osteolysis. Periprosthetic osteolysis is considered a significant long-term complication affecting the longevity of prosthetic implants and is the primary cause of prosthetic component mobilization.

The press-fit head is securely locked into the insert using a specific anti-dislocation retention mechanism.

The Chrono insert is available in various sizes to accommodate the cup-head coupling.

Chrono Head

The Chrono system is completed with standard spherical heads made of medical-grade steel that comply with ISO 5832/9 regulations. The geometric features adhere to ISO 7206-2 standards. The head is securely attached to the stem using a cone-morse connection.

Extra-long heads are also available, providing increased neck extension capabilities. The CHRONO head is offered in various diameters and a range of neck lengths. The head range includes options with extra-long necks.