The EndoLIF® Cages have been introduced to offer a minimally invasive as well as open (PLIF/ TLIF) alternative for fusion in the lumbar spine as an optimal treatment option for surgeons.
Material and design
EndoLIF® Cages consist of a titanium alloy (Ti6Al4V ELI) and are produced by EBM (Electron Beam Melting). An extraordinarily high surface roughness can be achieved, which is favorable for this application. All EndoLIF® Cages have a characteristic diamond cell structure to facilitate bone ingrowth. Furthermore, the implants are fillable with autologous bone or bone substitute. Due to the open design, it is also possible to monitor the fusion process ba X-ray or CT imaging.
SEM image of the characteristic EndoLIF® diamond cell structure
Titanium and titanium alloys are well known for their excellent biocompatibility and affinity to the surrounding bone. Recent studies document the excellent osseous integration of Ti6Al4V ELI alloy (ELI = Extra Low Interstitials) compared to other implant materials1.
Ti6Al4V ELI also provides improved mechanical properties in comparison to pure titanium and is ideally suited for the application as spinal cage2,3. The alloy used for the EndoLIF® Cages is of special purity. The incorporation of foreign atoms (iron and oxygen) is carefully monitored (according to ISO 5832-3) to increase the ductility (plastic deformation) and break strength. In addition, the cage design has been optimized and adapted to the anatomical conditions with extensive biomechanical tests and FEM analyses. All these advantageous properties make for an ideal cage implant for vertebral body fusion
Beginning fusion 3 months postoperatively
Excellent osseous integration 1 year postoperatively
FEM analysis of the EndoLIF® O-Cage under test load according to ASTM F2077. Clearly visible are the high stability and minimal deformation under shear compression load of 2.2 kN
Cross section of implant with bone cells in the microscopically visible interspaces2,3
Analysis of bone ingrowth on porous titanium cages in comparison to PEEK cages. Bone apposition on titanium cages increased over time and was significantly higher than for PEEK cages over the entire study duration1.
1Wu et al.: Porous Titanium-6 Aluminum-4 Vanadium Cage Has Better Osseointegration and Less Micromotion Than a Poly-Ether-Ether-Ketone Cage in Sheep Vertebral Fusion © 2013 Wiley Periodicals, Inc. and International Centerfor Artificial Organs and Transplantation; doi:10.1111/aor.12153
2A Palmquist et al.: Long-term biocompatibility and osseointegration of electron beam melted, free-form-fabricated solid and porous titanium alloy: Experimental studies in sheep; Journal of Biomaterials Applications 0(0) 1–14; ©The Author(s) 2011
3Christensen et al.: Qualification of Electron Beam Melted (EBM) Ti6Al4V-ELI for orthopaedic Implant Applications, © Medical Modeling LLC 2007
The endoscopic access is based on the proven TESSYS® access system, however application is also possible without having used the TESSYS® method before. This access offers the possibility of tissue conservation and dilation of the soft tissue between the muscle fibers with the use of special dilators. The dilators are then replaced with the working tube which fixates itself onto the vertebral body and into the surrounding muscle tissue through its unique design. Preparation of vertebral disc space and implantation of an EndoLIF® Cage is achieved with endoscopic assistance through the working tube, without the need to remove dorsal bone structures. Therefore, a fusion can be achieved without permanent structural damage to the bone or the multifidus muscle, which is vital for spinal stability1.