Stress radiography to measure posterior cruciate ligament insufficiency: a comparison of five different techniques

Stress radiography presents the golden standard to quantify posterior laxity in posterior cruciate ligament (PCL) insufficiency. Several different techniques are currently available, but comparative data are insufficient. Different stress radiographic techniques result in different values for posterior laxity. Comparative controlled clinical study was designed. Prior to PCL reconstruction 30 patients underwent a series of stress radiographs: Telos device, hamstring contraction, kneeling view, gravity view, and an axial view. Posterior displacement, side-to-side difference (SSD), condyle rotation, required time, and pain were measured. Posterior displacement was: Telos 12.7 +/- 3 mm (SSD 10.6 +/- 3.1 mm), hamstring contraction 11.2 +/- 3.2 mm (SSD 8.5 +/- 3.4 mm), kneeling 14.4 +/- 3.8 mm (SSD 10.2 +/- 3.5 mm), gravity view 10.5 +/- 2.8 mm (SSD 9.1 +/- 2.4 mm), and axial view 19.4 +/- 6.9 mm (SSD 8.5 +/- 4.1 mm). In comparison to Telos the hamstring contraction, gravity, and the axial view underestimated the SSD by approximately 2 mm. Telos and kneeling caused significantly more pain than all other techniques (P < 0.001). The axial view was fastest (115 s, P < 0.001) and Telos longest (305 s, P < 0.001), respectively. Telos indicated the lowest rotational error with a significant difference between kneeling and gravity (P < 0.003). In contrast to Telos as the golden standard, hamstring contraction, gravity, and axial view underestimated the SSD. Kneeling and Telos are comparable with respect to SSD and pain. Although kneeling indicates a greater rotational error than Telos, it seems to be a reliable alternative for quantifying posterior tibial displacement in a more simple and fast way.