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M. VALOROSO, G. LA BARBERA, G. DEMEY, D. DEJOUR
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with ACL lesion have a statistically significant
increased posterior tibial slope (PTS) and a
narrow intercondylar notch compared to the
control group. They report that 80% of patients
present at least one of these two risk factors,
but both are present only in 24% of the cases.
TIBIAL SLOPE
A significant association between increased
PTS and anterior tibial translation is observed,
suggesting that increased tibial slope is a
predisposing risk factor to ACL ruptures [4].
Normal values for PTS range from 5° to 7º [7].
In a radiological analysis performed using
lateral monopodal stance tests, Dejour and
Bonnin [7] observe that every 10º increase in
the PTS is associated with 6mm increase of the
anterior tibial translation in normal and ACL
insufficient knees. The forces on the knee
during weight-bearing can be resolved into a
vertically directed compression component and
a horizontally directed shear component: the
latter varies with the PTS. An excessive slope
induces the anterior tibial translation tensioning
the ACL and predisposing the ligament to
fatigue and injury (fig. 2). As well as for first-
time ACL ruptures, tibial slope can be
considered an important risk factor leading to
ACL graft failure. In revision ACL surgery, the
Fig. 1:
Narrow intercondylar notch is a modifiable intrinsic factor affecting the correct ligament kinematic.
Narrow notches are frequently A- or wave shaped while wider notches are more rounded or reverse
U-shaped.
Fig. 2:
During weight
bearing, the forces on
the knee can be resolved
into a vertically directed
compression component
and a horizontally di
rected shear component:
the latter varies with the
PTS. An excessive PTS
induces the anterior
tibial translation (ATT),
tensioning the ACL and
predisposing the li
gament to fatigue and
injury.