Summary
Medial hamstrings tendons contribution for knee valgus stabilization is predominant for knee flexion close to extension (between 0° and 30°) and their stabilising effect on knee valgus is even more important when the medial side is severely affected (MCL and POL damage).
Abstract
Introduction
Multi ligament knee injury including medial side damage are common. When performing surgical reconstruction, use of the medial hamstrings as graft remains controversial in this context. Our hypothesis was that the medial hamstrings (HS) play a role in stabilizing the valgus knee, especially in the presence of a severe medial sided injury. Our objective was to determine their role in stabilizing the valgus knee for different levels of medial side injury.
Method
A biomechanical study on 10 cadaveric knees was performed. Valgus laxity (force moment of 10N.m-1) was examined at different degrees of flexion (0°, 30° and 60°) using an opto-electronic motion analysis system. The measurements were repeated for different injury levels: intact knee, superficial medial collateral ligament (sMCL) injury, deep medial collateral ligament (dMCL) injury, and Posterior Oblique Ligament (POL) injury. For each injury level, 4 loading conditions (+ loaded, - unloaded) of the semitendinosus (ST) and gracilis (Gra) tendons were tested using a test stand: ST+/Gra+, ST+/Gra-, ST-/Gra+, ST-/Gra-.
Results
Unloading the ST and Gra increased valgus laxity on an intact knee at 0° (p<0.05). For a medial side injured knee (isolated sMCL, combined sMCL/dMCL and combined MCL/POL damage) unloading of ST and Gra increased valgus laxity at 0° and 30°. Absolute value of laxity increased with the severity of medial side ligament injury. Isolated ST unloading increased valgus laxity for an intact knee and a MCL (both sMCL and dMCL) injured knee at 0° (p<0,05). Isolated unloading of the Gra had no effect on valgus knee stability.
Conclusion
The medial HS tendons contribute to the stabilization of the knee in valgus, and this is even more important when the medial side is severely affected (POL damage). This stabilizing effect is greater in the early range of knee flexion (between 0° and 30°) in which POL is the main valgus stabilizer of the knee. Medial HS should be preserved in case of medial side knee injuries including MCL and POL damage.