This process is repeated with and without pressure for medial and lateral compartments identifying the same points as bony landmarks (FIG. 3).
For the ACL it can also be measured evaluating the difference in each of the two points of measurement is calculated between the two sets (with and without pressure) obtaining the anterior translation, in millimeters, for medial and lateral tibial plateaus: MPT - Medial plateau translation; LPT - Lateral plateau translation (FIG. 4).
Similar procedure is performed for healthy and injured knees.
Besides MPT and LPT, it was also calculated the difference between LPT and MPT (LPT-MPT) which reflects the increased translation of lateral tibia condyle associated to rotational instability.
The registered differences between injured and healthy knees for MPT, LPT and LPT-MPT can be used to assess the difference in behavior between stable and ACL-deficient knees (Dif. MPT, Dif. LPT and Dif. LPT-MPT) (FIG. 4).
It is also possible to use horizontal cuts in MRI to measure the angle between the line of the posterior cortex of the tibia and femur.
The influence of ACL in joint stability under torsional load is not yet fully understood16
. Several papers concerning clinical outcomes of double-bundle ACL reconstruction have been reported but “measuring” its influence in improving clinical results has proven to be a difficult task. A prospective comparable study of single- and bi-socket reconstruction by Hamada et al found no difference in clinical outcomes17
. Similar (or not significantly different) outcomes regarding stability were described by Muneta et al18
and Yasuda et al 19,20
. On a meta-analysis of randomized control trials no clinically significant differences were found on KT-1000 nor pivot-shift test4. However no reproducible method capable of quantifying rotational laxity was considered. We must recognize that proper measurement tools will guide our surgical practice. This has probably been the case of ACL reconstruction once the use of anterior translation measurements as primary means to assess the outcome of ACL surgery might have led to subsequent development of effective techniques of controlling anterior translation but not of rotational instability, particularly during high demand activities21-23