Introduction
Isolated Posterior Cruciate Ligament (PCL) lesions are always tricky condition to be managed for the surgeon. In fact, even though good results have been reported with nonoperative treatment the persistent posterior tibial subluxation drives to altered cartilage load and so to osteoarthritic changes.
Moreover, the standard diagnostic methods merging clinical evaluation and stress x-ray only explore the knee in static condition with the risk to overlook the possible effects of increased knee laxity, occurring in everyday active life conditions.
Hence, the purpose of this study was to investigate the in-vivo biomechanics of isolated PCL-injured patients in active everyday life condition using wearable inertial sensors.
We hypothesized that global kinematical difference would exist between non-injured and injured leg and that increased laxity of the PCL-injured knee would have led to increased tibio-femoral accelerations.
Methods
8 patients, 6 males and 2 females were included in this study. Patients performed a gait over a 20m linear path (10m back and forth) at their self-selected speed. No difference in speed was detected among the patients. The biomechanical analysis was conducted through a set of 8 wearable inertial sensors (MTW Awinda, Xsens) placed bilaterally on feet, shins, and thigh, one on the pelvis and one on the trunk. The waveform kinematics (joint angles in the three planes) of hip, knee, and ankle joints and kinetics (linear acceleration in the three planes) of femur, tibia, and foot segments were normalized over the gait cycle and compared between injured and non-injured leg. The Student’s t-test in Statistical Parametric Mapping (SPM1D) was used to compare the waveforms data.
Results
Greater knee internal rotation and hip external rotation at initial contact, and hip abduction, hip external rotation and ankle eversion during swing were noted for the injured-leg kinematics (p=0.035). Greater anterior-posterior and medial-lateral peak negative accelerations were also noted for the injured-leg at both tibia and femur levels (p=0.021) at the initial contact.
Conclusion
The most important finding of the present study was that significant biomechanical side-to-side differences existed between the injured and non-injured leg during different stages of gait demonstrating a whole limb compensation strategy. Moreover, during the impact phase of the task increased tibiofemoral acceleration have been detected in the PCL-injured knee.
The clinical relevance of this study is that eventual knee and lower limb alterations can be effectively detected through non-invasive wearable inertial sensors supporting the need for dynamic analysis in daily clinical practice for such tricky injuries.