Restoration of the tibial ACL footprint area and geometry using the Modified Insertion Site Table.

PURPOSE: This article is based on the concept of complete footprint restoration. It introduces a "Modified Insertion Site Table" for individual size-matched single- (SB) and double-bundle (DB) ACL reconstruction, which gives surgical guidelines for graft diameters and drill angles according to the restored tibial insertion site area and geometry.
METHODS: Potential graft diameters and drill angles were matched for all individual tibial insertion site lengths between 8 and 21 mm. A "Modified Insertion Site Table" was calculated to achieve a maximum of area restoration of the tibial ACL footprint for each of these insertion site lengths. The geometry of the restored footprint was considered.
RESULTS: A wide ACL footprint up to a 16-mm-long insertion site might be best restored with a SB-, a narrow one with a DB-ACL reconstruction. In a 17-mm-long insertion site, SB- and DB-ACL reconstructions restore a similar amount of footprint area, so geometry considerations of the footprint may decide which surgical technique may be favourized. SB can restore a maximum length of 13.1 mm and DB up to 21 mm. The width of the restored area depends on the drill bit diameter(s) and is larger for SB in most cases. In larger footprints, DB can replicate up to 63% more area and 37% more length than SB-ACL reconstruction.
CONCLUSIONS: Anatomical footprint restoration requires assessment of the length, width, and the orientation of the tibial ACL insertion site. Both SB- and DB-ACL reconstruction may achieve a wide range of area and geometric restoration of the individual ACL footprint. While SB-ACL reconstruction may be best used for wide insertion sites with up to 16 mm in length, DB-ACL reconstruction has the potential to restore narrow and larger footprints up to 21 mm in length. The "Modified Insertion Site Table" resumes the concept for orientation during surgery