How do I avoid a two-stage procedure in Revision ACL reconstruction surgery?

Topic / Overview

Background / Problems

• Patient & Athletic Burden of Two-Stage Procedures:
  • Requires a mandatory 3 to 6 months delay between stage one (bone grafting) and stage two (revision reconstruction).
  • Prolonged absence often causes professional athletes to lose an entire season, which can be career-ending.
  • Associated with increased cumulative surgical morbidity and higher overall financial cost.
  • Speaker’s Opinion: A two-stage procedure is often a reflex decision by surgeons rather than an objective evaluation of whether single-stage surgery is feasible.
• Failure Analysis in Primary Reconstruction:
  • Critical to determine why the primary graft failed to avoid duplicating structural or technical errors.
  • Factors contributing to failure include:
    • High posterior tibial slope (can be offset by adding a lateral extra-articular tenodesis).
    • Suboptimal tunnel placement.
    • Inadequate primary fixation or graft choice.
• Previous Hardware & Hardware In Situ:
  • Retained fixation devices must be evaluated on preoperative CT:
    • Hardware well outside the revision field can be left alone/bypassed.
    • Absorbable interference screws can be drilled through, but doing so scatters debris within the joint, which has been implicated in subsequent tunnel widening.

Classification or Concept: Structural Scenarios in Revision ACL

1. Scenario 1: Non-Conflicting Tunnels (Far-out Tunnels)
   • Previous tunnels are nowhere near the anatomic target.
   • Can be treated essentially like a primary reconstruction by establishing completely new tunnels.
2. Scenario 2: Anatomic, Undilated Tunnels
   • Prior surgeon positioned tunnels correctly and no significant widening occurred.
   • Prior tunnels can be reused directly after meticulous preparation.
3. Scenario 3: Markedly Widened Tunnels (Tunnels $\le$ 17–20 mm)
   • Substantial osteolysis/cavitation.
   • Requires void-filling techniques: large metal interference screws, multi-strand hamstrings, rectangular bone blocks (“square peg in a round hole”), or acute bone dowel grafting.
4. Scenario 4: Malpositioned Tunnels (Overlapping / Near Miss)
   • Excessively anterior tibial tunnel: Causes anterior roof/notch impingement during extension; graft eventually fails.
   • Excessively posterior tibial tunnel ($>10$ mm posterior): Causes a vertically oriented graft; can drill a completely new anatomic tunnel anterior to it without structural collision.
   • Excessively posterior tibial tunnel ($<10$ mm posterior): Highly problematic “near miss” causing critical tunnel collision and wall blowout if reamed conventionally.

Indications / Patient Selection

• Absolute Indication for Two-Stage Revision:
  • Massive cavitary/uncontained bone defects in the tibia where secure graft fixation and containment cannot be achieved acutely.
  • Speaker’s Series: Only 3 out of 204 patients (1.5%) between 2009 and 2017 required a two-stage procedure.
• Indications for Single-Stage Revision (Speaker’s Algorithm):
  • Tunnels dilated up to 17 mm (managed with multi-strand hamstrings combined with large interference screws).
  • Tunnels dilated up to 20 mm (managed using large rectangular bone blocks from BTB or quadriceps tendon).
  • Professional or high-level competitive athletes requiring accelerated return to sport and career preservation.
  • Presence of multiple previous drill tracks amenable to acute allograft bone dowel impaction.

Technique / Principles

1. General Principles

• Autograft Superiority: Strong preference for autograft over allograft due to markedly lower re-rupture rates (citing MARS group data demonstrating an approximate three-fold increase in failure rate with allograft).
• Mandatory Adjunct Tenodesis: An extra-articular tenodesis (e.g., modified MacIntosh tenodesis fixed with a staple) is added in every revision case to minimize rotational stress on the revision construct.
• Minimum Graft Diameter: In Western populations, a soft tissue (hamstring) graft diameter of at least 8 mm is required; larger grafts must be balanced against the risk of creating excessively large bone tunnels that could collide with existing defects.
• Notchplasty: Regularly required when very large grafts are utilized to prevent secondary roof or lateral notch impingement.

2. Specific Technical Solutions by Structural Scenario

A. Reusing Anatomic, Undilated Tunnels

• Meticulous debridement of all fibrous/soft-tissue scar lining.
• Decortication of the tunnel walls using a curette or a microfracture awl/pick to generate a bleeding cancellous bone bed to promote graft integration.

B. Eccentric Reaming & “Square Peg in a Round Hole”

• For tunnels with minor positional errors or widening, shift the tunnel axis by intentionally reaming eccentrically.
• Utilize a rectangular bone block from a bone-patellar tendon-bone (BTB) or quadriceps tendon autograft: the square bone block wedges tightly within the round reamed tunnel to gain multi-point cortical press-fit.
• Large metal interference screws are placed to physically push and bias the graft eccentrically against the desired anatomic wall of the tunnel.

C. The Excessively Anterior Tibial Tunnel

• Ream directed posteriorly from within the tunnel to enlarge it toward the anatomic footprint.
• The revision graft is positioned against the intact posterior margin of the new tunnel.
• A large-diameter metal screw is placed in the anterior void, acting as a structural filler and displacing the graft posteriorly away from the intercondylar roof.

D. The Excessively Posterior Tibial Tunnel

• Defect $>10$ mm posterior to target: Straightforward drill-hole separation; establish a completely new anatomic tunnel anteriorly. Keep the new graft diameter modest to avoid bridge breakdown between tunnels.
• Defect $<10$ mm posterior to target: High risk of failure.
  • Reaming anteriorly and attempting to seat the graft anteriorly fails because knee flexion pulls the graft backward into the old defect.
  • Placing an excessively long screw anteriorly leads to graft abrasion against the screw tip and subsequent rupture.
  • Management: Requires either acute bone grafting / dowel reconstruction or a true two-stage procedure.

E. Acute Allograft Bone Dowel Technique (Single-Stage Salvage)

• For multiple or complex prior drill tracks in the tibia:
  1. Impact cancellous/cortical allograft bone dowels into the unwanted tunnel spaces (e.g., anterior tracks) to achieve an interference press-fit.
  2. Temporarily transfix the bone dowels using smooth K-wires driven into the joint/cortex to maintain absolute stability during drilling.
  3. Under guidewire control, gently drill the definitive new revision tunnel through/adjacent to the stabilized dowel bed.
  4. Pull the definitive graft into position.
  5. Secure the graft using an anteriorly placed screw that compresses the graft against the anatomic posterior tunnel margin, surrounded by stable bone graft.

F. Femoral-Side Bailouts & Dual Fixation

• Femoral Salvage: When femoral tunnel integrity is compromised, consider the over-the-top position.
• Tibial Double Fixation: Primary aperture fixation with an interference screw, supplemented with graft traction sutures tied over a bicortical post screw or suture anchor.
• Femoral Double Fixation: Interference screw to establish graft position/aperture fit, combined with a suspensory cortical button (Endobutton) for soft-tissue grafts, or graft sutures tied around the lateral MacIntosh tenodesis staple for patellar/quadriceps tendon bone blocks.

Results / Survivorship / Evidence Cited by the Speaker

1. External Evidence Cited

• MARS Cohort Data: Allografts in revision ACL reconstructions carry an approximately three-fold (nearly 3x) higher failure rate compared to autografts.

2. Speaker’s Personal Clinical Series

• Study Population: 94 revision ACL cases across 93 consecutive patients over a 7-year period (private practice cohort).
  • Elite Athletes: 48% (nearly half).
  • Surgeon Origin: Speaker was the primary surgeon in only 26% (just over one-quarter); 74% were referrals.
  • Complexity: 20% (1 in 5) were undergoing their second or subsequent (tertiary/quaternary) revision.
  • Concurrent Pathology: 90% exhibited concomitant meniscal and chondral damage at the time of revision.
• Follow-up: 100% follow-up achieved; minimum of 2 years, with a mean follow-up of 4.3 years.
• Failure Rate: 4.3% (4 out of 93 patients suffered a recurrent graft re-rupture), occurring at a mean of 1.6 years post-revision.
• Functional Scores & Outcomes:
  • Tegner and KOOS functional scores were high and comparable to published international benchmark revision series.
  • A professional rugby league player with three previous ACL failures returned to competitive sport at 9 months following acute bone dowel single-stage revision.

Complications / Limitations

• Subsequent Re-Operations: Nearly 25% of patients required secondary surgical procedures, predominantly minor interventions including:
  • Arthroscopic partial meniscectomy.
  • Hardware removal.
• Infection: One case of deep surgical site infection occurred; this involved the adjacent extra-articular osteotomy site (not the intra-articular graft construct), which resolved successfully with plate removal after the osteotomy had united.
• Conflict of Interest / Implant Bias: The speaker declared a financial conflict of interest as a board member and shareholder of Innovate Orthopaedics (a company manufacturing metal interference screws), explaining an inherent technical preference for metal screw implants.
• Notch Impingement: Bulky revision autografts require careful assessment to prevent impingement; failure to perform sufficient notchplasty risks recurrent loss of full extension and graft abrasion.

Comparison with Alternatives

Single-Stage vs. Two-Stage Revision ACL Reconstruction

Revision Graft Choice Comparison

Practical Clinical Implications

• Mandatory Preoperative Imaging: Always obtain a thin-slice CT scan to map previous tunnels in three dimensions and assess retained hardware before entering the operating room.
• Hardware Removal Decision Tree:
  • Outside the revision trajectory $\rightarrow$ Leave in place.
  • Directly obstructing the new tunnel trajectory $\rightarrow$ Remove.
  • Absorbable screws in trajectory $\rightarrow$ Avoid drilling through if possible to prevent particulate debris scattering and subsequent tunnel lysis.
• Graft Selection by Tunnel Width:
  • Tunnels up to 17 mm: Tripled or quadrupled hamstring autograft combined with large metal interference screws.
  • Tunnels up to 20 mm: Rectangular bone blocks (BTB or quadriceps tendon autograft) to produce a press-fit seal.
• Biomechanical Offloading: In the revision setting, address secondary stabilizers. Routinely incorporate a lateral extra-articular tenodesis to protect the revision construct, particularly in knees with an elevated posterior tibial slope.

Key Take-Home Points

1. Two-stage revision ACL is rarely necessary: In specialized hands with rigorous planning, greater than 98% of revision ACL cases can be successfully managed in a single stage.
2. Autograft remains the gold standard in revision surgery: Due to the nearly three-fold increase in allograft failures shown by the MARS data, allograft should be reserved only for instances with zero remaining autologous harvest options.
3. The tibia is the primary surgical challenge: Femoral complications can be bypassed utilizing the over-the-top position, whereas tibial malposition and widening require complex eccentric reaming, large metal void-filling screws, or acute bone dowels.
4. Routine adjuncts optimize survival: Combining double fixation (aperture screw + cortical post/staple) with routine lateral extra-articular tenodesis provides mechanical security for complex revision reconstructions.

Exam Pearls

• The $<10$ mm Posterior Tibial Tunnel Trap: An old tibial tunnel positioned less than 10 mm posterior to the correct target is the most dangerous “near miss.” Reaming anteriorly causes the graft to drop into the posterior cavity during flexion, while long anterior screws abrade the graft against their tip. Consider acute bone dowel grafting or a staged procedure.
• Square Peg in a Round Hole Concept: Rectangular bone blocks derived from patellar tendon or quadriceps tendon autografts wedge tightly across circular reamed tunnels up to 20 mm in diameter, establishing cortical press-fit across irregular defects.
• Absorbable Screw Hazard: Drilling directly through retained bioabsorbable screws distributes foreign-body debris into the tunnel interface, which is recognized as an etiology of aggressive post-revision osteolysis and tunnel widening.
• MARS Failure Multiplier: When defending graft selection in an exam or viva setting, quote the Multicenter ACL Revision Study (MARS) finding that allografts carry an approximate 3-fold higher re-rupture rate compared to autografts in revision ACL surgery.
• Z-Value / Clinical Benchmark: In a high-risk cohort with 90% concomitant articular damage and 48% elite athletes, a single-stage algorithm achieved a 4.3% failure rate at 4.3 years of follow-up, validating single-stage management when executed with strict technical rigor.