Th P Branch (USA)
Background : Surgery is performed on an injured knee to correct biomechanical changes and reduce clinical symptoms. During assessment, it should be determined whether an injured/repaired knee can enter an unstable position (lateral tibial plateau not physically underneath the femoral condyle). It is important to understand biomechanical changes that allow for an unstable position to occur and how those changes reflect damage to anatomical structures. This connection between instability and biomechanical changes can help provide better treatment. Factors which affect assessment of knee instability include: 1) Knee Morphology; 2) Combined Laxity; 3) Extra-articular Damage.
Stability Assessment Factors
Knee Morphology
A positive pivot shift after ACL reconstruction is considered a failure. Predicting which patients will have a positive pivot shift after reconstruction using measures available prior to surgery could influence surgical decision-making. We showed that combined measures of bone morphology from pre-surgery radiographs can predict the presence of a pivot shift after surgery. Individual measures alone could not.
Combined Laxity
The pivot shift test shows better correlation to patient satisfaction after ACL reconstruction than anterior laxity differences. Combined laxity better predicts patient satisfaction. We showed better prediction of unsatisfied patients when Total leg rotation and KT manual maximum were combined into a single factor.
Extra-articular damage
We studied effects of lateral extra-articular repair (LAR) during ACL reconstruction by comparing patients with and without LAR. LAR reduced internal rotation of the tibia when compared to intraarticular repair alone. Increased internal rotation is a key factor in knee instability and patient satisfaction.
Clinical Significance : Improved assessment of knee stability would aid in the treatment/surgical decision-making process.