Interbody Fusion Devices: Comparing PEEK, Titanium, and Surface-Enhanced Cage Technologies

Úvod

Interbody fusion represents one of the most common and important procedures in spine surgery, with hundreds of thousands performed annually worldwide. The fundamental goal of these procedures is to achieve solid arthrodesis between adjacent vertebral bodies while maintaining or restoring appropriate disc height, sagittal balance, and foraminal patency. Central to this process is the interbody fusion device or “cage,” which serves as both a structural spacer and a scaffold for bony ingrowth and fusion.

The evolution of interbody fusion devices has been remarkable, progressing from simple bone grafts to sophisticated engineered implants manufactured from advanced biomaterials with specialized surface technologies. This progression has been driven by the pursuit of optimal clinical outcomes, including high fusion rates, minimal subsidence, and long-term construct stability. Among the most significant developments has been the diversification of biomaterials used in these devices, with polyetheretherketone (PEEK), titanium, and various surface-enhanced technologies emerging as the predominant options in contemporary practice.

This comprehensive review examines the material properties, design considerations, clinical performance, and emerging trends in interbody fusion device technology, with particular focus on comparing PEEK, titanium, and surface-enhanced cage designs across various clinical applications.

Historical Evolution of Interbody Fusion Devices

Early Approaches to Interbody Fusion

The concept of interbody fusion has evolved significantly since its inception:

1. Bone Graft Era (1940s-1970s):
2. Autologous iliac crest bone graft as the original interbody spacer
3. Cloward’s technique for anterior cervical discectomy and fusion
4. Limitations included graft collapse, extrusion, and donor site morbidity

5. Structural allografts introduced as alternatives to autograft

6. First-Generation Devices (1980s-early 1990s):

7. Introduction of threaded fusion cages (Bagby and Kuslich cage)
8. Primarily manufactured from titanium and stainless steel
9. Cylindrical designs requiring significant endplate preparation

10. Limited options for size and lordotic angle

11. Second-Generation Devices (mid-1990s-2000s):

12. Development of rectangular and trapezoidal cage designs
13. Introduction of PEEK as an alternative material
14. Improved anatomical fit and endplate interface

15. Enhanced radiographic assessment capabilities

16. Contemporary Era (2010s-Present):

17. Proliferation of material options and hybrid designs
18. Advanced manufacturing techniques including 3D printing
19. Technologie modifikace povrchu
20. Patient-specific and anatomically optimized implants

This evolution reflects the ongoing pursuit of the ideal interbody fusion device that combines optimal mechanical properties, biological performance, and ease of use.

Surgical Approach Evolution

The development of interbody fusion devices has paralleled the evolution of surgical approaches:

1. Anterior Approaches:
2. Anterior cervical discectomy and fusion (ACDF)
3. Anterior lumbar interbody fusion (ALIF)
4. Device designs optimized for direct anterior access

5. Larger footprint implants possible due to approach

6. Posterior Approaches:

7. Posterior lumbar interbody fusion (PLIF)
8. Transforaminal lumbar interbody fusion (TLIF)
9. Constrained insertion corridors influencing device design

10. Evolution toward minimally invasive variations

11. Lateral Approaches:

12. Direct lateral interbody fusion (DLIF/XLIF)
13. Oblique lateral interbody fusion (OLIF)
14. Specialized cage designs for lateral insertion

15. Emphasis on large footprint and indirect decompression

16. Hybrid and Emerging Approaches:

17. Anterior to psoas (ATP) approach
18. Endoscopic-assisted techniques
19. Robot-assisted placement
20. Navigation-integrated approaches

Each surgical approach presents unique constraints and opportunities that have influenced the design and material selection of interbody devices.

Material Properties and Biomechanical Considerations

PEEK (Polyetheretherketone)

PEEK emerged in the late 1990s as an alternative to metallic interbody devices and has become one of the most widely used materials:

1. Mechanické vlastnosti:
2. Elastic modulus (3-4 GPa) similar to cortical bone
3. Reduced stress shielding compared to metals
4. High strength-to-weight ratio
5. Resistance to fatigue failure

6. Maintenance of properties in vivo

7. Imaging Characteristics:

8. Radiolucent nature allowing unobstructed radiographic fusion assessment
9. Minimal artifact on CT and MRI
10. Typically includes radiopaque markers for visualization

11. Enhanced postoperative imaging for adjacent structures

12. Manufacturing Considerations:

13. Injection molding capabilities for complex geometries
14. Consistent material properties across production lots
15. Ability to incorporate features such as teeth, ridges, and channels

16. Recent advances in 3D printing of PEEK

17. Omezení:

18. Bioinert surface with limited cell adhesion
19. Hydrophobic properties potentially limiting osseointegration
20. Potential for fibrous encapsulation rather than direct bone apposition
21. Limited capacity for surface texturing in conventional manufacturing

PEEK’s combination of mechanical properties and imaging characteristics has made it a popular choice, particularly in scenarios where radiographic assessment of fusion is prioritized.

Titanium and Titanium Alloys

Titanium has a long history in orthopedic and spine implants, with specific advantages for interbody applications:

1. Mechanické vlastnosti:
2. Higher elastic modulus (110 GPa) compared to bone
3. Excellent strength and fatigue resistance
4. Potential for stress shielding due to stiffness mismatch

5. Superior resistance to plastic deformation under load

6. Biological Properties:

7. Excellent biocompatibility with minimal foreign body reaction
8. Osseointegration capabilities through direct bone apposition
9. Hydrophilic surface promoting cell attachment

10. Potential for enhanced fusion rates compared to PEEK

11. Imaging Characteristics:

12. Radiopaque nature allowing direct implant visualization
13. Artifact on CT and MRI potentially obscuring fusion assessment
14. Beam hardening effects on CT

15. Improved modern alloys and designs with reduced artifact

16. Manufacturing Considerations:

17. Traditional machining and milling
18. Advanced manufacturing including electron beam melting (EBM)
19. Selective laser melting (SLM) for complex architectures
20. Ability to create controlled porosity and surface textures

Titanium’s biological advantages, particularly its osseointegration properties, have maintained its relevance despite the emergence of alternative materials.

Surface-Enhanced Technologies

Surface enhancement represents a significant advancement aimed at combining the advantages of different materials:

1. Titanium-Coated PEEK:
2. PEEK core maintaining favorable modulus and imaging characteristics
3. Titanium surface layer (typically 100-400μm) for enhanced osseointegration
4. Various application methods including plasma spray, vapor deposition, and electron beam

5. Potential for coating delamination as a concern

6. Porous Titanium Structures:

7. Engineered porosity mimicking trabecular bone architecture
8. Pore sizes optimized for bone ingrowth (typically 300-700μm)
9. Reduced effective modulus compared to solid titanium

10. Enhanced surface area for bone contact

11. Surface Roughening Techniques:

12. Subtractive manufacturing to create micro-textures
13. Grit blasting and chemical etching
14. Laser modification of surfaces

15. Hierarchical surface structures combining macro, micro, and nano features

16. Bioactive Surface Treatments:

17. Hydroxyapatite coatings
18. Calcium phosphate applications
19. Bioglass incorporation
20. Growth factor and peptide functionalization

These surface-enhanced technologies aim to address the limitations of traditional PEEK and titanium implants by optimizing both mechanical and biological performance.

Biomechanical Testing and Standards

Standardized testing provides comparative data on interbody device performance:

1. Static Mechanical Testing:
2. Compression testing (ASTM F2077)
3. Subsidence testing (ASTM F2267)
4. Expulsion resistance
5. Torsional stability

6. Footprint and endplate contact area assessment

7. Dynamic Testing:

8. Fatigue testing under physiological loads
9. Cyclic loading to simulate in vivo conditions
10. Wear debris generation assessment

11. Long-term stability evaluation

12. Interface Mechanics:

13. Friction coefficient with vertebral endplates
14. Initial stability measurements
15. Resistance to migration

16. Impact of surface textures and treatments

17. Finite Element Analysis:

18. Computational modeling of stress distribution
19. Prediction of subsidence risk
20. Optimization of design parameters
21. Patient-specific simulations

These standardized assessments provide valuable comparative data but must be interpreted in the context of clinical performance and patient-specific factors.

Design Considerations and Innovations

Anatomical Considerations

Interbody device design must account for regional anatomical variations:

1. Cervical Region:
2. Smaller footprint requirements (12-15mm width, 14-18mm depth)
3. Lower height profiles (5-10mm)
4. Lordotic angles typically 0-7°
5. Considerations for uncinate processes

6. Cortical-cancellous bone distribution

7. Thoracic Region:

8. Transitional anatomy between cervical and lumbar
9. Kyphotic alignment considerations
10. Limited access corridors influencing design

11. Smaller endplate dimensions compared to lumbar

12. Lumbar Region:

13. Larger footprint possibilities (22-30mm width, 27-36mm depth)
14. Greater height options (8-16mm)
15. Lordotic angles up to 15-20°
16. Variations in endplate strength across regions

17. Considerations for indirect decompression

18. Lumbosacral Junction:

19. Unique angulation requirements
20. Asymmetric designs for L5-S1
21. Enhanced fixation features for high-stress region
22. Accommodation of sacral slope

Device design must balance these anatomical considerations with the constraints imposed by specific surgical approaches.

Structural Design Features

Beyond material selection, several structural design features influence device performance:

1. Footprint Geometry:
2. Rectangular vs. kidney-shaped vs. anatomical designs
3. Maximization of endplate coverage
4. Balance between stability and endplate preservation

5. Approach-specific constraints on insertion profile

6. Endplate Interface:

7. Teeth, ridges, and serrations for initial stability
8. Domed vs. flat surfaces for endplate matching
9. Directional features to resist expulsion

10. Surface roughness optimization

11. Internal Architecture:

12. Open vs. closed designs
13. Graft chambers and windows
14. Structural supports and weight-bearing columns

15. Porosity and void fraction considerations

16. Expandable Designs:

17. In-situ height expansion mechanisms
18. Lordotic correction capabilities
19. Continuous vs. incremental expansion
20. Trade-offs between adjustability and mechanical integrity

These design features significantly impact the mechanical performance, surgical handling, and biological environment for fusion.

Fixation Strategies

Various fixation strategies have been developed to enhance initial stability:

1. Integrated Fixation:
2. Self-securing features such as blades or spikes
3. Deployable anchoring mechanisms
4. Integral screws through the device

5. Zero-profile designs for anterior cervical applications

6. Supplemental Fixation:

7. Anterior plates for ACDF and ALIF
8. Posterior pedicle screw constructs
9. Lateral plates for lateral approaches

10. Integrated plate-cage designs

11. Surface Treatments for Enhanced Friction:

12. Plasma-sprayed surfaces
13. 3D-printed textures
14. Micro-etched features

15. Biomimetic surfaces

16. Novel Fixation Concepts:

17. Bidirectional expansion
18. Conformable interfaces
19. Shape memory materials
20. In-situ polymerization

The selection of appropriate fixation strategy depends on the specific clinical scenario, bone quality, and overall construct design.

Advanced Manufacturing Techniques

Novel manufacturing methods have expanded design possibilities:

1. Additive Manufacturing (3D Printing):
2. Selective laser melting of titanium
3. Electron beam melting
4. Laser sintering of PEEK

5. Direct metal laser sintering

6. Benefits of Additive Manufacturing:

7. Complex geometries not possible with traditional methods
8. Controlled porosity and trabeculae-like structures
9. Functional gradients within a single implant

10. Patient-specific customization potential

11. Hybrid Manufacturing:

12. Combination of additive and subtractive techniques
13. Integration of different materials
14. Optimized surface characteristics

15. Reduced post-processing requirements

16. Quality Control Considerations:

17. Consistency across production lots
18. Validation of mechanical properties
19. Cleaning and sterilization challenges
20. Regulatory pathways for novel manufacturing methods

These advanced manufacturing techniques have enabled a new generation of interbody devices with unprecedented combinations of mechanical and biological properties.

Clinical Performance and Outcomes

Fusion Rates and Assessment

The primary goal of interbody fusion is solid arthrodesis:

1. Radiographic Assessment Methods:
2. Plain radiographs (sentinel sign, bridging bone)
3. Computed tomography with multiplanar reconstruction
4. Dynamic flexion-extension studies

5. Advanced techniques including DEXA and PET-CT

6. Material-Specific Considerations:

7. Challenges in assessing fusion through titanium implants
8. Enhanced visualization with PEEK devices
9. Hybrid devices requiring specialized assessment protocols

10. Standardization challenges across studies

11. Reported Fusion Rates:

12. PEEK: 85-95% in cervical applications, 70-90% in lumbar applications
13. Titanium: 90-97% in cervical applications, 75-95% in lumbar applications
14. Surface-enhanced devices: Emerging data suggesting potential improvements

15. Significant variability based on surgical technique, patient factors, and assessment methods

16. Time to Fusion:

17. Potential advantages of titanium and surface-enhanced devices
18. Earlier bridging bone formation reported with osteoconductive surfaces
19. Clinical relevance of fusion timing remains debated
20. Balance between early stability and long-term outcomes

While fusion rates are a critical outcome measure, methodological variations in assessment make direct comparisons between studies challenging.

Subsidence and Biomechanical Stability

Subsidence into adjacent vertebral bodies remains a significant concern:

1. Incidence and Impact:
2. Reported rates of 5-30% depending on definition and follow-up
3. Clinical significance remains debated
4. Correlation with symptomatic outcomes not always clear

5. Potential impact on sagittal alignment and foraminal height

6. Material-Specific Considerations:

7. Theoretical advantage of PEEK’s modulus similar to bone
8. Mixed clinical evidence regarding material impact
9. Surface area and endplate preparation potentially more significant than material

10. Emerging data on porous titanium structures with modulus optimization

11. Design Factors Affecting Subsidence:

12. Footprint and endplate coverage
13. Edge design and stress concentration
14. Endplate preparation technique

15. Load distribution characteristics

16. Faktory pacienta:

17. Bone mineral density as a critical factor
18. Endplate quality and sclerosis
19. Smoking status
20. Metabolic factors affecting bone quality

The multifactorial nature of subsidence highlights the importance of considering both implant and patient factors in device selection.

Clinical Outcomes Comparison

Patient-reported outcomes provide the most clinically relevant assessment:

1. Pain and Functional Outcomes:
2. Visual Analog Scale (VAS) for pain
3. Oswestry Disability Index (ODI)
4. Neck Disability Index (NDI)

5. SF-36 and quality of life measures

6. Srovnávací studie:

7. Limited high-quality direct comparisons between materials
8. Most studies show similar clinical outcomes across materials
9. Potential advantages in specific subpopulations

10. Methodological challenges in isolating material effects

11. Reoperation Rates:

12. Similar across materials in most studies
13. Pseudarthrosis as a leading cause
14. Adjacent segment disease independent of material

15. Device-specific complications (migration, fracture)

16. Long-Term Outcomes:

17. Limited data beyond 5-10 years for newer materials and designs
18. Durability considerations
19. Adjacent segment effects
20. Late complications including implant failure

While material selection is important, surgical technique, patient selection, and overall construct design likely have greater impact on clinical outcomes.

Specific Clinical Applications

Different clinical scenarios may favor specific materials and designs:

1. Cervical Fusion:
2. All materials show high fusion rates (>90%)
3. PEEK advantages for imaging and assessment
4. Zero-profile and integrated fixation designs

5. Emerging data on surface-enhanced options

6. Anterior Lumbar Fusion:

7. Large footprint devices possible
8. Standalone vs. supplemental fixation considerations
9. Material selection potentially more impactful due to loading

10. Lordotic options for sagittal balance

11. Posterior and Transforaminal Lumbar Fusion:

12. Insertion corridor constraints on design
13. Titanium potentially advantageous for smaller footprints
14. Surface-enhanced options for challenging fusion environments

15. Expandable designs gaining popularity

16. Lateral Approaches:

17. Large surface area contact with stronger peripheral endplate
18. Indirect decompression considerations
19. Subsidence particularly relevant
20. Specialized designs for specific approaches

The optimal material and design choice varies based on the specific clinical scenario, highlighting the importance of a tailored approach to device selection.

Comparative Analysis of Materials

PEEK vs. Titanium: Direct Comparisons

Direct comparative studies between PEEK and titanium provide insights into relative performance:

1. Fusion Rates:
2. Meta-analyses suggest potential advantages for titanium
3. Seaman et al. (2017): Higher fusion rates with titanium in ACDF
4. Nemoto et al. (2014): Faster fusion with titanium in lumbar applications

5. Methodological limitations in many comparative studies

6. Subsidence Comparison:

7. Mixed results across studies
8. Rao et al. (2014): No significant difference in ACDF
9. Seaman et al. (2017): Higher subsidence with titanium in some studies

10. Design factors potentially more important than material alone

11. Klinické výsledky:

12. Generally similar patient-reported outcomes
13. Minimal clinically important differences rarely achieved between materials
14. Specific advantages in select patient populations

15. Longer-term data needed for definitive comparison

16. Complication Profiles:

17. Similar overall complication rates
18. Material-specific issues (e.g., imaging artifacts with titanium)
19. Reoperation rates comparable in most studies
20. Technique-related complications independent of material

The available evidence suggests that while material differences exist, their clinical impact may be modest compared to other factors such as surgical technique and patient selection.

Surface-Enhanced Technologies: Emerging Evidence

Surface-enhanced devices aim to combine the advantages of different materials:

1. Titanium-Coated PEEK:
2. Theoretical “best of both worlds” approach
3. In vitro studies showing enhanced cell adhesion and proliferation
4. Animal studies demonstrating improved osseointegration

5. Early clinical data suggesting potential fusion advantages

6. Porous Titanium Structures:

7. Biomimetic designs showing promising results
8. McGilvray et al. (2018): Enhanced bone ingrowth in animal models
9. Emerging clinical data suggesting high fusion rates

10. Potential for reduced subsidence through modulus optimization

11. Surface Roughening of PEEK:

12. Chemical and physical modification techniques
13. Improved wettability and cell attachment in vitro
14. Limited clinical data available

15. Manufacturing consistency challenges

16. Bioactive Coatings:

17. Hydroxyapatite and calcium phosphate applications
18. Growth factor incorporation
19. Promising preclinical results
20. Limited long-term clinical data

While surface-enhanced technologies show promising early results, more robust clinical evidence is needed to definitively establish their advantages over traditional materials.

Úvahy o nákladové efektivitě

Economic factors increasingly influence material and device selection:

1. Direct Implant Costs:
2. Significant variation across materials and designs
3. PEEK generally more expensive than basic titanium
4. Surface-enhanced and 3D-printed devices at premium price points

5. Regional and market variations in pricing

6. Total Episode Costs:

7. Potential offset of higher implant costs through improved outcomes
8. Reduced reoperation rates potentially justifying premium devices
9. Length of stay and complication costs

10. Long-term economic impact of fusion success

11. Value-Based Assessments:

12. Quality-adjusted life year (QALY) analyses
13. Incremental cost-effectiveness ratios
14. Limited data specific to interbody material selection

15. Need for long-term economic models

16. Healthcare System Considerations:

17. Bundled payment implications
18. Risk-sharing arrangements
19. Global budget constraints
20. Variation in willingness-to-pay thresholds

The economic evaluation of different interbody fusion materials remains underdeveloped, with most analyses focusing on surgical approach rather than specific implant selection.

Decision-Making Framework

A systematic approach to material selection considers multiple factors:

1. Patient-Specific Factors:
2. Bone quality and fusion potential
3. Anatomical considerations
4. Previous surgeries and radiation

5. Metabolic factors affecting fusion

6. Surgical Approach Considerations:

7. Access corridor constraints
8. Endplate preparation capabilities
9. Supplemental fixation options

10. Surgeon experience and preference

11. Biomechanical Requirements:

12. Loading conditions at target level
13. Stability requirements
14. Deformity correction needs

15. Adjacent segment considerations

16. Imaging and Assessment Needs:

17. Postoperative imaging requirements
18. Need for fusion assessment
19. Adjacent pathology monitoring
20. Tumor surveillance in oncologic cases

This multifactorial approach to decision-making recognizes that no single material is optimal for all clinical scenarios.

Budoucí směry a nové technologie

Next-Generation Biomaterials

Novel materials continue to emerge for interbody applications:

1. Silicon Nitride:
2. Ceramic material with unique properties
3. Hydrophilic surface promoting osseointegration
4. Bakteriostatické vlastnosti
5. Favorable imaging characteristics

6. Early clinical data showing promising results

7. Composite Materials:

8. Carbon fiber-reinforced PEEK
9. Titanium-PEEK composites beyond surface coating
10. Gradient structures with varying properties

11. Biomimetic composites mimicking bone structure

12. Biodegradable Options:

13. Polylactic acid (PLA) and polyglycolic acid (PGA) derivatives
14. Magnesium-based alloys
15. Řízené profily degradace

16. Transition from mechanical support to biological fusion

17. Smart Materials:

18. Shape memory alloys and polymers
19. Stimulus-responsive materials
20. Self-adjusting implants
21. Materials with sensing capabilities

These emerging materials may address current limitations and expand the applications of interbody fusion technology.

Biologics Integration

The integration of biological factors with interbody devices represents a significant frontier:

1. Growth Factor Delivery:
2. Bone morphogenetic protein (BMP) carriers
3. Controlled release systems
4. Dose optimization to minimize complications

5. Alternative growth factors with improved safety profiles

6. Cell-Based Approaches:

7. Stem cell incorporation
8. Autologous concentration systems
9. Cell-seeded scaffolds

10. Imunomodulační přístupy

11. Gene Therapy Applications:

12. Local delivery of osteogenic genes
13. Viral and non-viral vectors
14. Inducible expression systems

15. Targeted enhancement of fusion biology

16. Bioactive Surface Functionalization:

17. Peptide modification for enhanced cell attachment
18. Enzyme-mimetic surfaces
19. Antibacterial functionalization
20. Smart surfaces responding to biological environment

The combination of advanced biomaterials with biological enhancement strategies may significantly improve fusion outcomes in challenging scenarios.

Patient-Specific Solutions

Personalized approaches to interbody fusion are gaining traction:

1. Custom Implant Design:
2. Patient-specific dimensions based on imaging
3. Optimized endplate matching
4. Correction of specific deformities

5. Accommodation of anatomical variations

6. Preoperative Planning Integration:

7. Virtual surgical planning
8. Patient-specific instrumentation
9. Optimization of implant position and size

10. Predictive modeling of outcomes

11. Intraoperative Customization:

12. 3D printing in hospital setting
13. Modular systems with intraoperative assembly
14. Real-time modification based on surgical findings

15. Adaptive implants responding to intraoperative assessment

16. Personalized Biological Optimization:

17. Genetic profiling for fusion potential
18. Metabolic assessment and modification
19. Patient-specific growth factor dosing
20. Individualized adjunctive therapies

These personalized approaches aim to address the significant variability in patient anatomy and biology that influences fusion outcomes.

Advanced Manufacturing Horizons

Manufacturing technology continues to evolve, enabling new possibilities:

1. Multi-Material 3D Printing:
2. Simultaneous deposition of different materials
3. Functional gradients within implants
4. Integration of sensors and electronics

5. Biologically active components

6. Nanoscale Manufacturing:

7. Control of surface features at nanometer scale
8. Biomimetic nanostructures
9. Enhanced cellular interactions

10. Novel material properties through nanostructuring

11. Bioprinting Applications:

12. Integration of cells within printed structures
13. Spatially controlled biological factor delivery
14. Hybrid living/non-living constructs

15. Personalized tissue engineering approaches

16. In-Hospital Manufacturing:

17. Point-of-care fabrication systems
18. Reduced inventory requirements
19. Immediate customization capabilities
20. Integration with intraoperative imaging

These manufacturing advances will likely enable increasingly sophisticated interbody devices that transcend the limitations of current materials and designs.

Závěr

The evolution of interbody fusion devices represents a remarkable convergence of materials science, biomechanical engineering, surgical technique, and biological understanding. From simple bone grafts to sophisticated engineered implants, these devices have transformed spine surgery and improved outcomes for countless patients with degenerative, traumatic, and deformity conditions.

The comparative analysis of PEEK, titanium, and surface-enhanced technologies reveals a nuanced landscape where each material offers distinct advantages and limitations. PEEK provides favorable modulus characteristics and superior imaging capabilities but may lack the osseointegration properties of titanium. Titanium offers excellent biocompatibility and bone apposition but presents challenges in radiographic assessment and potential stress shielding. Surface-enhanced technologies aim to combine these advantages but require further clinical validation.

The available evidence suggests that while material selection is important, it represents just one factor in a complex equation that includes surgical technique, patient characteristics, implant design, and biological environment. The optimal approach likely involves tailored selection based on specific clinical scenarios rather than universal application of any single material or technology.

Looking forward, the field continues to advance through innovations in biomaterials, manufacturing techniques, biological enhancement, and personalized approaches. These developments promise to further improve fusion rates, reduce complications, and enhance patient outcomes across the spectrum of spinal pathologies requiring interbody fusion.

As with all medical technologies, the ultimate measure of success remains the improvement in patient quality of life and function. The ongoing refinement of interbody fusion devices, informed by rigorous clinical evidence and technological innovation, will continue to advance this fundamental goal of spine surgery.