What does the hardware used in a two‑level anterior cervical discectomy and fusion (ACDF) look like?

Hardware Components in Two-Level ACDF

A two-level ACDF construct consists of two interbody spacers (cages) placed at each disc level combined with an anterior cervical plate secured by screws into the vertebral bodies—not pedicle screws, which are never used in anterior cervical procedures. 1, 2

Standard Hardware Configuration

Interbody Spacers

• Titanium cages are the most established option with fusion rates of 98% at 12 months, superior to autograft alone (90%) 1
• PEEK (polyetheretherketone) cages represent a modern alternative that can be packed with bone graft material, achieving 100% fusion rates in two-level procedures 3
• Carbon fiber cages maintain better lordotic alignment and disc height but carry higher pseudarthrosis rates (62% vs 86% for traditional Cloward procedure) 1
• Each cage is placed within the disc space after complete discectomy at both operated levels 3, 4

Anterior Cervical Plate System

• The plate spans across both operated levels (e.g., C4-C6 for a C4-5 and C5-6 fusion), secured by screws that engage the vertebral body—never the pedicles 1, 2
• Static plates provide rigid fixation across multiple levels 1
• Dynamic plates allow controlled micromotion but are not clearly superior in clinical outcomes 1
• The plate extends anteriorly beyond the disc space, which increases dysphagia risk compared to zero-profile alternatives 5, 6

Alternative Zero-Profile Devices

Integrated Cage-Screw Constructs

• Zero-profile devices combine the interbody spacer with integrated fixation that does not extend beyond the intervertebral disc space 5, 6
• These devices use anchoring clips or screws that lock directly into the cage body, with fixation points placed in the upper and lower vertebrae at each level 3
• Biomechanical stability is equivalent to traditional plate constructs in flexion-extension, lateral bending, and axial rotation (no significant differences, p > 0.05) 5
• The zero-profile design reduces chronic dysphagia rates to 3.5% compared to higher rates with anterior plating 4

Bone Graft Material Within Cages

Graft Options for Two-Level Procedures

• Autograft from iliac crest shows superior fusion rates (83%) compared to allograft alone (37%) specifically in contiguous two-level procedures 2
• Allograft (cadaveric bone) achieves fusion rates of 87-97% for single-level procedures but performs less reliably in two-level constructs 2
• Local osteophytes combined with cancellous allograft packed within PEEK cages achieved 100% fusion at mean 4.5 months in two-level procedures 3
• Recombinant human BMP-2 (rhBMP-2) combined with allograft spacers achieved 100% fusion at 3 months, though complications included postoperative hematomas (23.2% complication rate overall) 1

Physical Appearance and Dimensions

Cage Characteristics

• Rectangular or cylindrical titanium cages with threaded or smooth surfaces for endplate engagement 1
• PEEK cages appear white/off-white with self-locking mechanisms and anchoring clips visible on the anterior surface 3
• Typical height restoration is 3.3mm per level, with cages sized to match the patient's native disc space 4

Plate Characteristics

• The anterior plate is a thin metal construct (typically titanium) spanning 2-3 vertebral bodies for two-level fusion 1
• Four to six screws total secure the plate: typically 2 screws in each end vertebra and 2 screws in the middle vertebra 1
• Screw trajectory is angled into the vertebral body, not perpendicular, to maximize purchase 1

Clinical Outcomes and Hardware Selection

Plating Benefits in Two-Level Disease

• Anterior cervical plating is specifically recommended over fusion alone to improve arm pain in two-level cervical disc degeneration (Class II evidence, strength C) 1
• Plating reduces pseudarthrosis risk and maintains lordosis (4.5° average improvement) but does not necessarily improve other clinical parameters 1, 4

Zero-Profile Device Advantages

• Equivalent fusion rates (93% of operated levels) compared to traditional plating with sustained pain improvement (VAS decreased from 5.1 to 3.1) 4
• Faster surgical time when treating adjacent-level disease, as prior hardware removal may be avoided 5
• Lower dysphagia rates due to minimal anterior profile 6, 4

Common Pitfalls to Avoid

• Never confuse pedicle screws with anterior cervical screws—pedicle screws are reserved for posterior approaches or lumbar spine, not anterior cervical procedures 2, 7
• Avoid redundant grafting strategies (simultaneous use of autograft, allograft, and cage) as single grafting strategies achieve comparable fusion rates without added morbidity 2
• Autograft harvest causes donor site complications in 22% of patients with persistent hip pain at 1 year, so reserve it for contiguous two-level procedures where it demonstrates clear superiority 2
• Hospital stay increases from 5.4 to 7.25 days when iliac crest harvest is performed, adding cost and recovery time 2