Subsidence and fusion performance of a 3D-printed porous interbody cage with stress-optimized body lattice and microporous endplates - a comprehensive mechanical and biological analysis.

BACKGROUND CONTEXT: Cage subsidence remains a serious complication after spinal fusion surgery. Novel porous designs in the cage body or endplate offer attractive options to improve subsidence and osseointegration performance. PURPOSE: To elucidate the relative contribution of a porous design in each of the two major domains (body and endplates) to cage stiffness and subsidence performance, using standardized mechanical testing methods, and to analyze the fusion progression via an established ovine interbody fusion model to support the mechanical testing findings. STUDY DESIGN/SETTING: A comparative preclinical study using standardized mechanical testing and established animal model. METHODS: To isolate the subsidence performance contributed by each porous cage design feature, namely the stress-optimized body lattice (vs. a solid body) and microporous endplates (vs. smooth endplates), four groups of cages (two-by-two combination of these two features) were tested in: (1) static axial compression of the cage (per ASTM F2077) and (2) static subsidence (per ASTM F2267). To evaluate the progression of fusion, titanium cages were created with a microporous endplate and internal lattice architecture analogous to commercial implants used in subsidence testing and implanted in an endplate-sparing, ovine intervertebral body fusion model. RESULTS: The cage stiffness was reduced by 16.7% by the porous body lattice, and by 16.6% by the microporous endplates. The porous titanium cage with both porous features showed the lowest stiffness with a value of 40.4±0.3 kN/mm (Mean±SEM) and a block stiffness of 1976.8±27.4 N/mm for subsidence. The body lattice showed no significant impact on the block stiffness (1.4% reduction), while the microporous endplates decreased the block stiffness significantly by 24.9% (p<.0001). All segments implanted with porous titanium cages were deemed rigidly fused by manual palpation, except one at 12 weeks, consistent with robotic ROM testing and radiographic and histologic observations. A reduction in ROM was noted from 12 to 26 weeks (4.1±1.6° to 2.2±1.4° in lateral bending, p<.05; 2.1±0.6° to 1.5±0.3° in axial rotation, p<.05); and 3.3±1.6° to 1.9±1.2° in flexion extension, p=.07). Bone in the available void improved with time in the central aperture (54±35% to 83±13%, p<.05) and porous cage structure (19±26% to 37±21%, p=.15). CONCLUSIONS: Body lattice and microporous endplates features can effectively reduce the cage stiffness, therefore reducing the risk of stress shielding and promoting early fusion. While body lattice showed no impact on block stiffness and the microporous endplates reduced the block stiffness, a titanium cage with microporous endplates and internal lattice supported bone ingrowth and segmental mechanical stability as early as 12 weeks in ovine interbody fusion. CLINICAL SIGNIFICANCE: Porous titanium cage architecture can offer an attractive solution to increase the available space for bone ingrowth and bridging to support successful spinal fusion while mitigating risks of increased subsidence.

Global commercial passenger airlines and travel health information regarding infection control and the prevention of infectious disease: What's in a website?

BACKGROUND: Air travel has never been easier, cheaper or faster, with large volumes of people travelling around the world. These factors increase the risk of the spread of infectious diseases by air travel. Little is known, however, about the extent to which airlines provide information to passengers on infection control and measures to prevent the spread of infectious diseases. This study examined the websites of the global commercial passenger airlines to see if they contained information about infection control and prevention of infectious diseases and appraised the clinical usefulness of that information. METHOD: A cross-sectional text-based analysis of the 73 airline websites from the six global commercial passenger airline conglomerates was performed to identify information about infection control and prevention of infectious between July and August 2019. RESULTS: Of the 73 airline websites, less than half (n = 35, 28.6%) contained information deemed useful for passengers. While there was a range of general health advice within the websites, there was limited information about infection control and preventing infectious diseases. A minority of websites contained information about vaccination status prior to travel, and to a lesser extent handwashing and hand hygiene, with very few including disease-specific advice or preventive measures. CONCLUSIONS: Airline websites are an underutilised source of information for infection control and the prevention of infectious diseases. Providing passengers with information on basic infection control and prevention measures may support the global efforts against the spread of infectious diseases.