Objective

To determine the optimal tibial tunnel placement for ACL reconstruction by quantify anatomy of tibial footprint and apply for the clinical use.
Study design and methods: A cross-sectional study was performed at Ramathibodi hospital between 2011 and 2013. Knee MRI which contained normal ACL was assessed for the ACL footprint size in sagittal and coronal view, and calculated ACL tibial footprint area. The measurement was done by two physicians, and repeated a month after to evaluate inter-observer and intra-observer reliability. Data analysis and level of agreement was analyzed by STATA 12.0 Program. Tibial footprint area data was analyzed for clinical application by formulate the determination of the optimal tibial tunnel placement angle (Both a and ß angle).

Results

The knee MRI of 100 patients with intact ACL were recruited . The average age was 36 + 7 years. Forty-five percent were male and 49 % were right side. The average ACL footprint sagittal and coronal diameters were12.92 and 13.81 mm respectively. ACL to PCL distance was 13.71 mm. Inter-observer reliability were 1.02 mm for sagittal diameter, 2.64 mm for coronal diameter, and -3.21 mm for ACL to PCL. Intra-observer reliability were -0.26 mm for sagittal diameter,-0.09 mm for coronal diameter, and 0.42 mm for ACL to PCL. The average ACL tibial footprint area was 141.95 sq.mm.

Conclusion

ACL footprint area average 141.95 sq.mm. According to the average quadruple hamstring graft 8mm. diameter, the optimal tibial tunnel placement should be 50° in a angle and 40° in ß angle
Keywords: ACL , Reconstruction , Anatomy , MRI ,Tibial tunnel , Footprint