The bony landmarks showed the boots-like-shape of anterior cruciate ligament tibial footprint around the anterior horn of lateral meniscus, while the width of insertion was proportional to the individual size of tibia in young knees.
Central intercondylar ridge (CIR) is the new anatomical bony landmark bisecting the slope of medial intercondylar ridge (MIR) between the tibial insertion of anterior cruciate ligament (ACL) and anterior horn of lateral meniscus (AHLM), revealed by computed tomographic (CT) evaluation corresponding to histologic slices in the elderly cadaveric knees. The purpose was to clarify the shape and size of ACL tibial insertion in the young healthy knees using CT images.
The contralateral healthy knees in 34 ACL-reconstructed patients (18males, 16 females, mean age: 24.0 years) were scanned by CT. In the reconstructed coronal/sagittal and 3D images, bony landmarks (anterior: anterior ridge, posterior: blood vessel in tubercle fossa, medial: MIR, lateral: CIR, lateral edge of AHLM: bottom of the slope were plotted to evaluate shape and size using 3D image analysis system. The length in sagittal slice, and the width in 5 coronal slices from anterior to posterior of the attachment site were measured.
CIR was located almost in almost center on the slope of MIR from anterior to posterior in all of the knees, except for the anterior portion just behind the anterior edge.The bony landmarks showed the square shape of MIR slope and the boots-like-shape of the ACL tibial attachment site around the AHLM tibial insertion site. The mean sagittal length of ACL tibial insertion site was 14.5 mm (SD: 1.9, range: 11.2 to 18.1mm), while the mean widths from anterior to posterior were12.7mm(SD: 2.7, range 7.4 to 19.6mm), 8.1mm(SD: 1.9, range: 5.2 to 12mm), 7.9mm(SD: 2.0, range: 4.3 to 12mm), 7.5mm(SD: 1.5, range: 4.8 to 9.9mm), and 7.2mm(SD: 1.6, range: 4.2 to 11mm). The anterior-posterior and transverse diameters of the tibial plateau were highly correlated with width of ACL insertion site in anterior edge (RS= 0.61, 0.55, P<0.01), anterior fourth (RS= 0.70, 0.71, P<0.01), central portion (RS= 0.68, 0.73, P<0.01), and posterior forth ( RS= 0.63, 0.68, P<0.01), in spite of mild correlation with ACL sagittal length (RS= 0.38, 0.41, P<0.01). These tendencies showed no difference between male and female.
The insertion size for the female was significant smaller than that for the male.(P<0.01)
In all young healthy knees, the bony landmarks showed the boots-like-shape of ACL tibial footprint shared the slope of MIR with the AHLM, while the width of insertion was proportional to the individual size of tibia. To minimize iatrogenic damage to the AHLM insertion, this study may provide useful information for individual anatomical tibial tunnel creation.