No single best technique: trade-offs in femoral interference screw fixation for bone-patellar tendon-bone anterior cruciate ligament reconstruction.

This review presents how surgeons should choose femoral interference screw in anterior cruciate ligament (ACL) reconstruction - insertion direction (inside-out vs outside-in), tunnel shape (round vs rectangular), screw position (anterior vs posterior), and screw material (metal, bioabsorbable, PEEK, magnesium) - to balance fixation strength, anatomic fidelity, and revision feasibility. Inside-out maximizes aperture compression and preserves the lateral femoral cortex but requires deep flexion and precise trajectory (risk of iatrogenic cartilage contact/posterior wall breach). Outside-in improves visualization and guide control yet needs a large lateral cortical socket and can push the bone plug intra-articularly as the screw advances from cortex to joint. Rectangular tunnels better match the native footprint, improving rotational control and interface congruity, while round tunnels simplify preparation but allow plug rotation and may use bone less efficiently at the aperture. Posterior screw placement (particularly with the inside-out technique) enhances cancellous-to-cancellous compression but risks posterior cortical breach injury; anterior placement protects fibers and favors footprint fidelity but may reduce cancellous compression. Metal offers high stiffness and no tapping but creates MRI artifact and requires removal if present at revision. Bioabsorbable materials avoid artifact/removal yet are weaker and may fracture in sclerotic tunnels. PEEK (metal-like without artifact) and magnesium (osteoconductive/resorbable) are promising but lack long-term data. No single method is universally optimal. Decisions should be individualized to visualization needs, cortical/bone-stock preservation, expected revision strategy, and patient factors (age, activity, bone quality).