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PEARLS & PITFALLS – SURGICAL TECHNIQUE
Etiologic Classification
There are three clinical signs and symptoms that lead us to consider an ACL reconstruction as a failure: instability, stiffness, and pain. Trying to identify what failed in first place is important; we have summarized most of the causes that can make the knee to progress into one or several of the previously mentioned conditions.
Classically literature has shown that ACL graft failures are primarily caused by technical mistakes (estimated at around 70%), chronic or acute traumatisms, and biologic causes. A recent Multicenter ACL Revision Study (MARS) Group developed a multi-surgeon, multicenter prospective longitudinal study to allow multivariable analysis and determine predictors of clinical outcome in revision ACL. The MARS cohort (460 patients) showed that mode of failure, as deemed by the revising surgeon, was traumatic (32%), technical (24%), biologic (7%), infection (<1%) and more often a combination of some of the previous (37%). Also from the MARS cohort, femoral tunnel malposition was reported to be the most common technical failure finding (80%), followed by tibial tunnel malposition (37%). Table 3 summarize the most common technical failures regarding non-anatomical tunnel placement.
Table 2. Etiologic Classification of Failure of ACL Reconstruction
1. Instability
Abnormal mechanical loads
Acute traumatic event Chronic repetitive movement
Inappropiate accelerated rehab postop
Non-anatomical tunnel placement
Anterior femoral tunnel Posterior femoral tunnel Anterior or posterior tibial tunnel Vertical femoral tunnel
Medial or lateral tibial tunnel
Misdiagnosed associated injuries
Medial collateral ligament Posterolateral corner Posterior cruciate ligament
Failure of graft fixation
Failure of fixation method Failure of graft tension Failure of graft isometry
Failure of graft selection
Failure of graft incorporation
Failure of graft due to infection
Lower extremity malalignment
2. Stiffness
Primary
Secondary
Inappropiate rehabilitation postop Technical error
Surgery at acute phase of injury Infection
CRPS
Synovitis and hematoma
3. Pain
Patello-femoral pain
Donor site pain
Femoro-tibial osteoarthritis
Residual meniscal tears
Synovial disease
Neuroma
CRPS
Table 3. Common Mistakes in Femoral and Tibial Tunnel Placement
Tunnel
Position
Consequences on the graft
Femoral
Anterior
Excessive tension in flexion or stiffness in extension
Posterior
Excessive tension in extension or laxity in flexion
Central / Vertical
Rotational instability
Tibial
Anterior
Excessive tension in flexion or impingement against intercondylar notch in extension
Posterior
Excessive tension in extension or impingement against the posterior cruciate ligament
Medial
Impingement against the medial femoral condyle or against the posterior cruciate ligament
Lateral
Impingement against the lateral femoral condyle
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ISAKOS NEWSLETTER 2015: Volume I 13