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Background Endoscopic ACL reconstruction is the high technically demand orthopaedic procedure. Careful surgical techniques are necessary to avoid intraoperative complications. The endoscopic femoral aimer must be inserted via the tibial tunnel. If we do not place the knee in the appropriate position, the aimer will point to the incorrect position.
Objective To identify the appropriate tibial tunnel angle (TTA) and knee flexion angle (KFA) and the relationship between these two angles.
Design Descriptive study
Setting Gross laboratory
Subjects Embalmed cadavers.
Materials & Methods 104 cadaveric knees of 54 cadavers were explored. A 2.0 mm. K-wire was drilled to the ACL tibial footprint with different TTA 40o,55o,70o while changing the KFA to 60o,75o,90o respectively. Lateral radiographic imaging was done for every pair of TTA and KFA to evaluate whether K-wires pointed to the femoral wire loops.
A K-wire was drilled to the ACL tibial footprint with TTA 40o, and the knee was flexed until the K- wire pointed to the femoral wire loop. Lateral radiographic imaging was done and the KFA was measured. These procedures were repeated again by changing TTA to 55o and 70o.
Results The most appropriate TTA and KFA was TTA 55o/ KFA 75o which made the K-wires pointed correctly 78.64%. The means of KFA when TTA 40o, 55oand 70o were 98.85o, 78.30oand 56.39o respectively. The relationship was presented in the following equation: KFA = 155.6-1.4 TTA, R2 = 0.80.
Conclusion The KFA at 55o TTA is not equal to KFA at TTA 40o or 70o. We, therefore, propose the reverse linear relationship between KFA and TTA which may guide the arthroscopist to place the knee in less flexion when using more TTA while aiming femoral tunnel and vice versa.