gms | German Medical Science

Objectives: Recent studies revealed that knee kinematics following ramp lesions can be restored using an all inside meniscal ramp lesion repair. However, there is a lack of literature regarding the effects of ramp lesion repair on ACL in-situ forces and bony contact forces. Hence, the purpose of this study is to determine the effect of ramp lesion repair on knee kinematics, the ACL in-situ forces and bony contact forces using a 6-degree-of-freedom robotic testing system. It was hypothesized that ramp repair will restore knee kinematics, ACL in-situ forces and bony contact forces comparably to the forces of the intact knee.

Methods: 9 fresh-frozen human cadaveric knee specimens were tested using a 6-degree-of-freedom robotic testing system (FRS2010) to continuously flex the knee from 0° to 90° and apply continuous loading conditions:

1.

90 N of anterior force,

2.

5 Nm of external rotation torque,

3.

134 N anterior force + 200 N compression force,

4.

4 Nm external rotation torque + 200 N compression force.

Loading conditions were applied to the intact knee, a knee with an arthroscopically induced 25mm ramp lesion, and a knee, subsequent to an all inside ramp lesion repair. In order to obtain ACL-in-situ forces and bony contact forces, the recorded kinematics were replayed after transection of the ACL, complete soft tissue removal, and transection of the lateral tibial plateau. Repeated measure ANOVAs were performed to compare knee states at each flexion angle (p<0.05).

Results and conclusion: In response to all loading conditions, no differences with respect to kinematics, ACL in-situ forces, and bony contact forces between the intact state and the ramp lesion state were detected. However, compared to the intact state, ramp lesion repair significantly reduced anterior translation in flexion angles from full extension to 40° in response to 5 N anterior force. While a ramp lesion repair did not significantly decrease the ACL in-situ forces in response to combined 134 N anterior force and 200 N compression force, a significant decrease of the ACL in-situ forces was detected only for higher flexion angles when 4 Nm external rotation torque and 200 N compression force were applied. In response to combined 134 N anterior force and 200 N compression force, Ramp lesion repair led to a decreased bony contact forces in the medial knee compartment and an increase of bony contact forces in the lateral knee compartment, However, these differences were not statistically significant.

While no differences with respect to knee kinematics, ACL in-situ forces, and bony contact forces between the intact knee and a 25 mm ramp lesion were detected, care must be taken to avoid a potential overconstraint when repairing ramp lesions utilizing all inside devices in maximum knee extension. Beneficial effects of ramp lesion repair on ACL in-situ forces and bony contact forces are questionable.

From biomechanical time-zero perspective, it is debatable if ramp lesions need to be addressed surgically.