[The role of posterolateral structure and posterior cruciate ligament in external rotatory stability of the knee].
OBJECTIVE
To investigate the changes of external rotation stability of the knee after the breaking and reconstruction of the posterolateral structure (PLS) of knee joint.


METHODS
The femurs of 16 fresh cadaveric lower limbs were fixed to the base of rotating holders with the knee joints in full extension, or at an angle of 30 degrees , 60 degrees , or 90 degrees ; while the tibia was attached to a free rotary holder. The external rotation of the tibia was measured with a 5 kg x m x s(-2) tibial torque. The external rotation angle of the tibia was measured after the transectioning of the popliteus tendon (PT), popliteus muscle (PM), popliteofibular ligament (PFL), fibular collateral ligament (LCL), or popliteus tendon (PT). Autogenous hamstring tendon was used to reconstruct the PCL, and the Achilles tendon was used to reconstruct the PFL and PT, then the external rotation angle of the tibia was measured again.


RESULTS
The isolated sectioning of PCL did not increase the tibial external rotation angle. When the knee was flexed the external rotation angle was 14.1 degrees in the intact knee and was 14.57 degrees in the PCL transectioning group (q = 0.47, P > 0.05). After the PFL was sectioned, when the knee joint was flexed at 60 degrees the external rotation angle was 16.94 degrees (q = 2.84, P < 0.05). After the PT was sectioned (PCL + PFL + PT), when the knee joint was flexed at 60 degrees the external rotation angle was 28.1 degrees (q = 14.01, P < 0.05). After isolated PCL reconstruction the external rotation angle was still bigger than that of the normal knee: for example, when the knee joint was at the angle of 60 degrees the external rotation angle was 27.67 degrees (q = 0.425, P < 0.05). There was a significant decrease in external rotation compared with PT section (P < 0.05). After the combined PCL + PLS reconstruction when the knee joint was at the angle of 60 degrees the external rotation angle of the knee was 14.51 degrees (q = 0.412, P < 0.05), however, the range of change was less than 1 degree.


CONCLUSIONS
Isolated PCL section produces no change in external rotation. Complex injury of PCL and PSL can produce instability in external rotation. PT has the greatest important role to resist external rotation, then the greatest increase in external rotation can be found after PT is sectioned. Isolated PCL reconstruction can not completely restore the posterolateral stability of the knee. PCL reconstruction can partly restore the stability of the external tibial rotation. Only the combined PC + PLS reconstruction can reset the knee to physiological stability of external rotation.
Nie
Xi-zeng
XZ
Department of Joint Surgery, Third Hospital of Shijiazhang, Shijiazhuang 050011, China.
Sun
Ran
R
Chen
Bai-cheng
BC
Ma
Xiang-yi
XY
Wang
Xiao-feng
XF
D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology* / Q000601:surgery; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D016119:Posterior Cruciate Ligament / Q000293:injuries / Q000503:physiopathology* / Q000601:surgery