A finite element simulation of the effect of graft stiffness and graft tensioning in ACL reconstruction.
BACKGROUND
The anterior cruciate is the most frequent knee ligament to be totally disrupted. Surgical reconstruction of the anterior cruciate ligament is a common practice to treat the disability or chronical instability of knees due to anterior cruciate ligament insufficiency. Some of the factors that influence the success or failure of the anterior cruciate ligament reconstruction are the integrity of secondary restraints, the preoperative laxity of the knee, the status of the articular and meniscal cartilages, the selection of the graft material, the surgical technique, the graft tension and the postoperative rehabilitation.


METHODS
In this paper we present and discuss the results obtained with a three-dimensional finite element model of the human knee joint corresponding to different aspects of human anterior cruciate ligament reconstruction. In particular, this model was used to investigate the effect of graft stiffness and graft tensioning on the knee joint biomechanics. The initial graft tension was set to 0, 20, 40 or 60 N with the knee at 0 degrees , 30 degrees and 60 degrees of flexion. Three different stiffnesses corresponding to those of patellar tendon, gracilis and quadrupled semitendinosus grafts were analyzed.


RESULTS
The resulting kinematics in each of these cases under an anterior load of 134 N was compared to that of the intact knee. The obtained results showed that, after reconstruction, the closest anterior tibial translation to that of the intact knee is obtained with a bone-patellar tendon-bone graft with a pretension of 60 N.


CONCLUSIONS
However, this initial tension produces an important additional stress in the graft during the knee movement. This may cause problems in revascularization and remodelling during the postoperative healing process. A lower pretension of about 40 N should therefore be recommended in the present conditions.
Peña
E
E
Group of Structural Mechanics and Material Modelling, Aragon Institute of Engineering Research (I3A), University of Zaragoza, María de Luna, 3. E-50018 Zaragoza, Spain. fany@unizar.es
Martínez
M A
MA
Calvo
B
B
Palanca
D
D
Doblaré
M
M
D000070598:Anterior Cruciate Ligament Injuries; D004548:Elasticity; D006801:Humans; D021621:Imaging, Three-Dimensional; D007718:Knee Injuries; D007719:Knee Joint / Q000502:physiology; D019651:Plastic Surgery Procedures; D012421:Rupture; D013314:Stress, Mechanical; D013710:Tendons / Q000637:transplantation*