BIOLOX®* delta Ceramic Femoral Head
The new alumina matrix composite BIOLOX delta meets the increased demands in hip replacement. While this high performance ceramic offers the same advantages as third generation alumina ceramic, i.e. excellent biocompatibility, low wear, high hardness, outstanding chemical and hydrothermal stability, its wear and mechanical properties are even superior to those of alumina ceramic.
The BIOLOX delta Ceramic Femoral Head is made from a new alumina matrix composite developed by CeramTec AG. This material is a high-performance ceramic that meets the increased demands regarding durability of the implants in young, active and/or heavy patients.
Benefits
- Improved mechanical properties compared to alumina heads
- Additional neck length for diameter > 32mm
- Additional diameters providing more ROM and stability
- Same benefits as BIOLOX forte remain for BIOLOX delta, i.e. appropriate for patients who are sensitive to specific metal elements
Sizing
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Caution: Must only be used in combination with new, undamaged 12/14 stem tapers!
Science behind BIOLOX delta Material
BIOLOX delta is an aluminum oxide matrix composite ceramic consisting of approx. 75% alumina (Al2O3), 24% zirconia (ZrO2) and other trace elements. The pink color is due to the chromium oxide (Cr2O3) that improves the hardness of the composite material.
Alumina provides the material’s hardness and wear resistance, while zirconia, together with other additives, provides improved mechanical properties. These properties are achieved, among other things, as a result of the high strength, the high density of the material and the very small grain size of the alumina matrix.
The result is a high-performance ceramic that offers the same advantages as BIOLOX forte: excellent biocompatibility, low wear, high hardness, good mechanical performance, outstanding chemical and hydrothermal stability.
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Microstructure of BIOLOX delta (Courtesy of CeramTec AG).
The Microstructure
The first toughening mechanism used in BIOLOX delta material results from the introduction of small, homogeneously distributed yttria-stabilized tetragonal zirconia particles (Y-TZP) in a stable alumina matrix. The spatial separation of these zirconia particles reduces the likelihood of structural transformation and prevents the initiation or propagation of cracks.
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The principle of transformation toughening by small zirconia particles, which are dispersed in the alumina matrix. 1. Alumina grain; 2. Zirconia grain. |
The second toughening mechanism is achieved by the addition of strontium oxide, which forms platelet-like crystals. These platelets dissipate energy by deflecting cracks, thereby increasing material strength and toughness.
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The principle of reinforcement by platelet-like crystals in an alumina matrix. 1. Alumina grain; 2. Zirconia grain; 3. Platelet-like crystal.. |
Improved Mechanical Properties
The excellent flexural strength and reduced grain size of BIOLOX delta material explain its value as an alternative bearing material against polyethylene.
Mechanical Properties and Benefits of Third Generation Alumina and Alumina Matrix Composite Ceramic
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Low Wear with Large Ceramic Heads
The advantages of ceramic materials in wear couples become even more evident with large diameter heads. In the past, large ceramic or metal head sizes in combination with conventional polyethylene resulted in higher wear.
Recent hip joint simulator studies have shown that even with the use of 36 mm ceramic head diameters against ceramic or highly cross-linked polyethylene, the wear rates remain very low. (1, 2) Thus, when using ceramics, the surgeon no longer has to compromise between wear rate and head size, and can choose the best option for the patient.
More Stability and Range of Motion
A large diameter articulation offers increased stability due to the increased displacement distance (X < Y) and a greater technical range of motion (a <b) compared to a conventional 28 mm articulation. These obvious clinical benefits, in combination with low-wear alternative bearings (ceramic on highly cross-linked polyethylene), result in improved functionality and durability.
Clinical studies have reported that there is a statistically significant decrease in impingement, subluxation and dislocations with 36 mm ceramic-on-ceramic coupling (0.88%) when compared to 28 mm femoral heads (4.64%) in THR.(3)
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Note: Wear couples with ceramics or with metal are prohibited in the U.S.
Handling of Alumina and BIOLOX delta Standard Heads
The alumina ceramic femoral head and BIOLOX delta ceramic femoral head may only be used with Zimmer stems, and in combination with highly cross-linked or conventional Zimmer polyethylene.
Use of Trial Heads
- Determine the neck length
- Check tissue balance
- Check range of motion
Check Implant Prior to Use
- Are the mating surfaces completely intact? It is absolutely essential that the taper of the femoral stem fit perfectly with the taper of the head.
- Is the correct ceramic femoral head selected? (With regard to diameter, taper size, neck length, material, manufacturer, etc.)
Careful Setting
- Remove any blood or debris from the stem taper.
- Prior to impacting of the femoral head onto a femoral stem, examine the inside of the femoral head to ensure that no foreign particles are present.
- Implant parts must be thoroughly cleaned and dried before they are used.
- Set the head with a rotary motion until it is immovable.
- To seat the ceramic femoral head, use a femoral head driver with a plastic face and a light hammer.
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*BIOLOX is a trademark of CeramTec AG.
References
(1) Clark IC, et al: Severe simulation test for run-in wear of all-alumina compared to alumina composite THR. In D’Antonio JA, Dietrich M (eds), Bioceramics and Alternative Bearings in Joint Arthroplasty, Darmstadt, Steinkopff, 2005, 11–20
(2) Fisher J, et al: Wear of highly crosslinked polyethylene against cobalt chrome and ceramic femoral heads. In Benazzo F, Falez F, Dietrich M (eds), Bioceramics and Alternative Bearings in Joint Arthroplasty. Darmstadt, Steinkopff, 2006, 185–188
(3) Zagra L, et al: THA ceramic-ceramic coupling: The evaluation of the dislocation rate with bigger heads. In Lazennec JY, Dietrich M (eds): Bioceramics in Joint Arthroplasty, Darmstadt, Steinkopff, 2004, 163–168
