Soyal Rao Batchu
BACKGROUND Of all the tests done to assess the anterior stability of knee joint i.e. anterior cruciate ligament (ACL) intactness, the pivot shift is a dynamic but passive test of knee stability, carried out by the examiner without any activity of the patient. It shows asynchrony between rolling movement and gliding movement of the knee joint. The patient lies in supine. The movement is a combination of axial load and valgus force, applied by the examiner, during a knee flexion from an extended position. When the test is positive, it indicates an injury of the anterior cruciate ligament.1,2 We wanted to study the tibio-femoral translation when the knee is in neutral position and when it is flexed to 30°. METHODS This study was conducted in the Department of Orthopaedics in A.C.S.R. Govt. Medical College from January 2017 to June 2019. In 20 patients with anterior cruciate ligament injury who volunteered for the examination, measurements were taken in anterior tibio-femoral translation with knee in neutral position and when it is flexed to 30o . Of 20 patients 16 patients are male and 4 patients are female. Patients were in the age group of 17-36 years with average age of 27 years. All 20 patients had instability of knee joint on clinical examination in the form of positive anterior drawer and Lachman tests. Every patient was checked by pivot shift test under anaesthesia. All the 20 patients included in the study had positive pivot shift test under anaesthesia. Bony landmarks in the form of lateral epicondyle of femur marked as point A, Gerdy’s tubercle on proximal tibia as point B and fibula head as point C were localized. These bony landmarks were transfixed using K-wires. The distance between these points was measured. The distance between points A and B is measured as AB, between points B and C is measured as BC and the distance between points A and C is measured as AC. All these lengths AB, BC & AC were calculated at knee in full extension and at 30o flexion (In case of positive pivot shift test for all most all patients the angle at which the subluxated proximal tibia gets reduced is 30o which was confirmed by goniometer). RESULTS The data of measurements were collected and tabulated. The results are correlated using Spearman’s Rank correlation coefficient of the variables. The coefficient for AC is calculated which is 0.7554 in 0° and 30° flexion and for AB it is 0.4387 in 0° and 30° flexion. Hence the correlation of AC in 0° & 30° is strong and the correlation of AB in 0° & 30° is moderate to low. CONCLUSIONS Pivot shift test despite of being a subjective test we have concluded that there is a moderate to strong correlation between relative movements of distal femur (represented by lateral femoral epicondyle) & proximal tibia (represented by Gerdy’s tubercle & fibular head).
