The concept of complete footprint restoration with guidelines for single- and double-bundle ACL reconstruction.

PURPOSE: This article introduces guidelines for single- (SB) and double-bundle (DB) ACL reconstruction based on the concept of complete footprint restoration. The goal is to reconstruct a maximum of anterior cruciate ligament (ACL) insertion site area to regain a maximum of ACL function. The concept is based on the hypothesis that the restored biomechanical envelope of the knee is a function of reconstructed ACL insertion site area.
METHODS: Individual combinations of graft diameters and drill angles were calculated and matched for all individual insertion site lengths between 8 and 21 mm to maximize the percentage of anatomical footprint restoration. An "insertion site table" was developed to propose individual guidelines during ACL surgery for SB and DB ACL reconstruction based on the intraoperative measurement of the tibial insertion site length.
RESULTS: Our calculations support the use of SB in "small footprints" up to 13 mm, which may restore more than 95% of the native insertion site length. "Intermediate footprints" between 14 and 15 mm may be restored by both a SB or DB ACL reconstruction. For "larger footprints" of 16 mm or more, DB has the potential to replicate 97% or more of the insertion site length which cannot be achieved by a SB ACL reconstruction.
CONCLUSIONS: The concept of complete footprint restoration aims to reconstruct a maximum of ACL insertion site area to restore a maximum of functional envelope of the knee. Depending on the individual situation, different surgical approaches (SB/DB), graft diameters and drill angles may apply. An "insertion site table" was designed to give guidelines for SB and DB reconstruction during surgery. According to the new concept, DB ACL reconstruction is only considered as a surgical tool for large footprints and is not indicated for smaller ones.