Application of a new positioning device for isometric replacement in anterior cruciate ligament repair and reconstruction.

The functional effects of displacing the cruciate ligament attachments were studied in ten adult cadaver knees. On a systematic variation of the femoral and tibial attachment sites according to a three-dimensional raster scheme, a quantitative analysis of the absolute length and of motion-dependent changes in ligament isometry was performed. All insertion points deviating from the original anatomic landmarks did not accomplish biomechanical requirements. A femoral displacement had an increased effect on disturbing isometry compared to a tibial malposition. Although recommended by several authors, the "over-the-top" position gave the most unsatisfactory results with a maximum isometry failure of 10 mm. In cruciate ligament replacement a positioning guide with isometry testing capacity should be mandatory to ensure correct placement of bone tunnels. For this purpose a new positioning device which allows for isometry measurements before a bone channel is drilled is introduced and applied in an experimental setup.