MRI analysis of tibial position of the anterior cruciate ligament.

This study aimed to establish normal values for the position of the native anterior cruciate ligament (ACL) insertion on the tibia to assist in the evaluation of tunnel placement after primary ACL reconstruction or prior to revision surgery. One hundred consecutive MRI studies performed on patients with a mean age of 29 years (range 20-35) from a single MRI facility were reviewed. Patients with prior surgery, significant osteoarthritis, acute ACL injury, or evidence of ACL reconstruction were excluded. Using digital image software, measurements were taken of anterior-most and posterior-most portions of the ACL insertion on the tibia. Depth of the tibia was also measured from the anterior edge of the tibial plateau to the posterior edge at the origin of the posterior cruciate ligament. The anterior insertion of the native ACL was located at a mean of 14 ± 3 mm (28 ± 5%) from the anterior tibial articular margin; the posterior portion of the ACL was located at a mean of 31 ± 4 mm (63 ± 6%). The tibial insertion of the ACL is located between 28 and 63% of the total anterior-posterior depth of the tibia. The results from this study are clinically relevant as they provide the clinician with baseline data to describe the position of the tibial footprint of the native ACL on sagittal MR imaging. Further, this data can be used as a guide to evaluate tibial tunnel position prior to primary ACL reconstruction, revision ACL surgery, or in ACL-reconstructed patients who continue to experience pain, instability, or dysfunction postoperatively.