INTRODUCTION
Anterior cruciate ligament reconstruction (ACLR) with bone-patella-tendon-bone (BTB)
autograft or allograft can be complicated by graft tunnel mismatch. We investigate the
lateral knee X-ray as a template to help calculate tibial tunnel length pre-operatively.
The similarity between Blumensaat’s line and the reconstructed anterior cruciate ligament
(ACL) length was a secondary outcome measure.
METHODS
20 consecutive ACLR were performed (13 male, 7 female); all were BTB autograft.
Average patient age was 27.8±11.8 years. All ACLR were performed anatomically
with independent drilling of the femoral and tibial tunnels. Lateral X-Rays were
obtained prior to ACLR. The length of Blumensaat’s line and the patellar
ligament were recorded. The overall graft length was calculated from the patellar
ligament length on lateral X-ray; subsequently, Blumensaat’s line was used to
calculate the tibial tunnel length. All pre-operative calculations; Blumensaat’s
line, patellar ligament, overall graft, and tibial tunnel lengths; were compared
to their respective intra-operative measurements. The amount of graft protrusion
or recession in the tibial tunnel was measured at the end of the case; effectively
the length of graft tunnel mismatch.
RESULTS
The average difference between the length of Blumensaat’s line and the reconstructed ACL was 1.4±1.2mm, pre-operative and intra-operative tibial tunnel was 4.5±4.5mm, and the average graft tunnel mismatch was 1.65mm. The mean percent difference between Blumensaat’s line and reconstructed ACL was 0.72% and pre-operative and intra-operative tibial tunnel length was 6.43%. The mean percent error for Blumensaat’s line and reconstructed ACL length, pre-operative and intra-operative patellar ligament and overall graft length, as well as graft tunnel mismatch is <10% (<10% is excellent, >30% is poor). Blumensaat’s line and the reconstructed ACL, pre-operative and intra-operative patellar ligament and overall graft length, and graft tunnel mismatch all had a correlation coefficient >0.8 (>0.8 is excellent, <0.2 is poor).
CONCLUSION
This method of pre-operatively templating an ACLR and calculating the tibial tunnel length is effective in minimizing the risk of graft tunnel mismatch when using BTB auto and allografts. Additionally, we demonstrated that Blumensaat’s line is essentially the same length as the reconstructed ACL.