What are the latest fixation techniques in Anterior Cruciate Ligament (ACL) reconstruction?

Latest Fixation Techniques in ACL Reconstruction

The current state-of-the-art in ACL reconstruction fixation involves three primary strategies—interference screw fixation, suspensory cortical fixation, and hybrid techniques—with no single method established as the gold standard, though each offers distinct biomechanical advantages that should guide selection based on specific clinical scenarios. 1, 2

Primary Fixation Categories

Interference Screw Fixation

• Interference screws provide compression fixation that decreases graft-tunnel motion, reduces tunnel widening, and minimizes graft creep compared to suspensory methods. 1, 2
• Available materials include metallic, PEEK (polyether ether ketone), and bioabsorbable screws, each with specific advantages. 1
• The primary risk is potential graft damage during screw insertion and possible graft slippage. 2
• This method is particularly advantageous when minimizing tunnel widening is a priority. 2

Suspensory Cortical Fixation

• Suspensory devices include suture-buttons (e.g., TightRope, EndoButton), anchors, staples, and screw/washer constructs that provide strong cortical fixation while allowing minimally invasive approaches. 1, 2
• These devices demonstrate adequate biomechanical strength comparable to interference fixation. 1, 2
• Critical limitation: adjustable-loop devices can experience clinically significant lengthening during cyclic loading, with some devices showing 42.45 mm of displacement after 4500 cycles. 3
• The adjustable TightRope RT reached clinical failure (3 mm lengthening) after only 1,349 cycles, while fixed-length devices like the EndoButton CL Ultra did not reach clinical failure during testing. 3
• Tying the free suture ends significantly reduces lengthening (from 42.45 mm to 13.36 mm in the TightRope), which is a crucial technical consideration. 3

Hybrid Fixation Strategies

• Combining compression and suspensory fixation provides biomechanical advantages over either method alone by securing the graft in two planes of motion. 2
• This approach addresses the individual limitations of each fixation type while maximizing stability. 2

Advanced Technical Considerations

All-Inside Techniques

• Second-generation all-inside ACL reconstruction using Flipcutter retrograde drills with adjustable cortical suspension devices (femoral and tibial TightRope systems) allows for minimally invasive reconstruction through only four 4-mm stab incisions. 4
• This technique permits graft tension adjustment even after initial fixation, addressing concerns about post-operative graft lengthening. 5, 4
• The graft-link technique can be modified for double-bundle reconstruction. 4

Graft Retensioning Capability

• Adjustable-loop fixation devices offer the unique ability to retension grafts intraoperatively, which is not possible with traditional fixed-length techniques. 5
• This addresses the critical issue of maintaining graft tension throughout the healing process. 5

Clinical Decision Algorithm

When selecting fixation method, prioritize based on:

1. For maximum stability and minimal tunnel widening: Use interference screw fixation (metallic, PEEK, or bioabsorbable). 1, 2

2. For minimally invasive approach with strong fixation: Use suspensory cortical fixation, but always tie free suture ends on adjustable-loop devices to prevent clinically significant lengthening. 3, 2

3. For optimal biomechanical security: Consider hybrid fixation combining both compression and suspensory methods. 2

4. For ability to adjust tension post-fixation: Use adjustable-loop suspensory devices with proper suture management. 5, 4

Critical Technical Pitfalls

• Adjustable-loop devices without tied suture ends will lengthen significantly during early rehabilitation, potentially causing graft failure. 3
• All ultimate loads of modern fixation devices exceed forces experienced during early rehabilitation, so the primary concern is cyclic loading and graft-tunnel motion rather than catastrophic failure. 3, 2
• Secure fixation is paramount regardless of implant choice to prevent graft displacement and facilitate early aggressive rehabilitation while allowing bone-tunnel integration. 1, 2

Supplemental Fixation Options

• When primary fixation adequacy is questioned, supplemental fixation using suture anchors, staples, or screw/washer devices provides additional security in a second plane of motion. 1, 2
• These adjunct methods offer biomechanical advantages over single-method fixation alone. 2