Minimizing Graft-Tunnel Mismatch in Allograft Anterior Cruciate Ligament Reconstruction Using Blumensaat's Line: A Cadaveric Study

Purpose: To evaluate the accuracy of Blumensaat's line (BL) in predicting the tendinous graft length and tibial tunnel length (TTL) in an independent-tunnel anterior cruciate ligament reconstruction (ACLR) using a bone-patellar tendon-bone (BTB) allograft. Methods: Eighteen ACLRs were performed on cadaveric specimens using an anteromedial portal technique. All knees had no previous surgeries or deformities. Lateral knee radiographs of each specimen were taken prior to the ACLR, and BL was measured. Length-specific allografts for the tendinous portion of the grafts were then ordered by adding 20 mm to the length of BL. The TTL was predicted by subtracting BL and femoral tunnel length (FTL) from the overall graft length. Graft-tunnel mismatch (GTM) was recorded for each specimen. Statistical analysis compared overall results with the gold standard (0 mm) of GTM. Results: The average lateral femoral condyle width measured in line with the femoral tunnel was 33 ± 3.43 mm. The average FTL was 25 ± 0.54 mm. The average intra-articular distance (IAD) between femoral and tibial tunnel apertures was 31 ± 3.65 mm. The average TTL was 35 ± 2.21 mm. The difference between the predicted TTL and the actual TTL was not statistically significant (P =.3). The mean GTM was −0.9 ± 3.15 mm. There was no statistically significant difference between the BL method and the gold standard (P =.45). The mean percent difference between BL and the IAD was 5.2%. Conclusions: The BL method can accurately predict the desired length for the tendinous portion of a BTB allograft as well as the TTL, thereby potentially minimizing GTM during arthroscopic BTB allograft ACLR. Patient-specific allografts can be ordered preoperatively based on BL. Clinical Relevance: This method provides the surgeon a way to avoid GTM preoperatively by ordering patient-specific grafts prior to performing an independent-tunnel BTB allograft ACLR.