FEMORAL MALTORSION INFLUENCES BOTH PATELLOFEMORAL AND TIBIOFEMORAL CONTACT PRESSURES. A BIOMECHANICAL EVALUATION

To investigate the effect of femoral maltorsion on both the patellofemoral and the tibiofemoral contact pressures. Experimental biomechanical study on 10 embalmed human cadaveric knees (mean age 40.2 years ± 9.5). Krackow sutures were placed in the vastus medialis, vastus lateralis, rectus femoris, vastus intermedius and hamstrings. A custom-made test apparatus capable of independently loading the quadriceps and hamstring muscle groups and providing ground reaction forces during a simulated squat maneuver and under direct axial compression loading was used. A ground reaction force of 1000 N was applied to the distal tibia and scaled loads of 218N and 80N were applied to the quadriceps and hamstrings respectively at 0°, 30°, 60° and 90° of flexion. Pressure measurements were performed by intra-articularly placed sensors (77.3 x 77.3 mm, SFM6000CXR2 Sensor) and using Snowforce 3 interpretation software. After testing of the native knee, supracondylar femoral osteotomy was performed. Pressure measurements were again made in each knee compartment, at each of the degrees of rotation evaluated. Medial aspect of the patella showed an increase of contact pressure with external femoral rotation from 10º to 30º compared to 0º. The strongest effect was measured at 30º of knee flexion (p=0.005) with 30º of external rotation (p=0.004) with a value of 2.140 ± 0.1832 Mpa. With internal femoral rotation there is an increment of contact pressure in the lateral aspect of the patella, with the strongest effect at 30º of flexion (p=0.0059) with 30° of internal rotation (p=0.0002) with a value of 1.352± 0.08166 Mpa. The medial tibiofemoral contact pressure showed an increment from 10° to 30° of external rotation compared to the native state. The highest pressure was shown at 90° of knee flexion (p=0.0006) and 30° of external rotation (p=0.004) with a value of 1.636 ± 0.01878 Mpa. The lateral tibiofemoral contact pressure increased compared to the control group more with internal than with external rotation. The highest pressure was shown at 90° of flexion (p<0.0001) and 30° of internal rotation (p<0.0001) with a value of 1.432 ± 0.004051 Mpa. Femoral malrotation influences patellofemoral and tibiofemoral contact pressure. Femoral external rotation may result in worse knee biomechanics than internal rotation. III.