| dc.description.abstract | Altered gait patterns may persist for months or even years in patients after anterior cruciate ligament reconstruction (ACLR). The persistence of these deficits during walking or running activities is of serious concern, as they could potentially increase the risk of knee degenerative changes in the long term. Analyzing altered gait patterns in this population are commonly performed in a specialized laboratory using motion capture and force plate systems. Although those measurement systems are considered the gold standard to identify alterations in joint biomechanics, they are expensive, require extensive training, and large laboratory space. More research studies have been conducted in recent years to develop an inexpensive and practical assessment tool that can quantitively analyze patients’ gait in clinical settings. In those previous studies, inertial sensors (i.e., accelerometers and gyroscopes) have been used to obtain information about lower trunk accelerations and shank angular velocity (SAV) during gait. For instance, past studies reported that patients with ACLR walked with altered trunk accelerations at 6 months post-surgery, when compared to healthy subjects. In addition, recent studies found that these patients presented with between-limb asymmetries in the sagittal plane SAV during walking at 3 months post-surgery, with lower peak SAV at the surgical limb compared to the non-surgical limb. However, it is unknown whether patients with ACLR would present with altered trunk accelerations and SAV asymmetry at faster gait speeds such as walking fast and running. In addition, the associations between these gait variables and patients’ functional and psychological measures have not been investigated. Therefore, the overall goals of this dissertation project were to use inertial sensors to longitudinally quantify trunk accelerations and SAV asymmetry during gait at different speeds and to determine whether these variables are associated with functional and psychological measures in patients with ACLR. In Chapter 2, the goal of the study was to compare changes in the acceleration patterns of the lower trunk during gait in ACLR patients over time and between ACLR patients and uninjured healthy subjects using accelerometry. Movement smoothness, calculated as normalized jerk (NJ) of trunk accelerations, during walking and walking fast was assessed at 2, 4, and 6 months after ACLR, whereas running smoothness was assessed at 4 and 6 months after ACLR. A total of 17 individuals with ACLR and 20 healthy uninjured controls participated in this study. Movement smoothness of participants was assessed during walking, walking fast, and running along a 12-meter straight walkway. A lower NJ value is indicative of a smoother gait pattern. The results showed that movement smoothness of the ACLR group during walking and walking fast improved (lower NJ) significantly across time, except for walking fast in the vertical direction. Running smoothness of the ACLR group did not improve from 4 to 6 months and was significantly less smooth than that of the healthy group. These findings suggest that the effect of the knee injury and the subsequent surgery may disrupt lower limb mechanics, which results in altered trunk accelerations during gait. Future studies with a longer follow-up period ( 6 months) should examine when running smoothness would normalize with that of healthy subjects. In Chapter 3, the goal was to investigate whether patients with ACLR would show significant and meaningful between-limb SAV asymmetries at different gait speeds at 4 and 6 months post-surgery. A total of 15 patients with ACLR participated in the study. Peak SAV was assessed in the sagittal plane during loading response of walking, walking fast, and running. From 16 healthy subjects, the smallest meaningful between-limb difference for SAV was estimated for each gait speed. The results showed that the surgical limb had significantly smaller peak SAV during loading response of all gait speeds at 4 and 6 months post-ACLR, when compared to the non-surgical limb. In addition, between-limb differences in SAV was higher than the smallest meaningful difference at both testing times. These findings indicate that individuals after ACLR presented with significant and meaningful SAV asymmetries during walking, walking fast, and running, especially at the time when some patients may return to sports activity at 6 months after surgery. These asymmetries may be indicative of altered shank kinematics during gait. Chapters 4 and 5 investigated the associations between gait measures and measures of patients’ functional and psychological status at 6 months after ACLR. Functional evaluation was conducted by testing patients’ performance on return-to-sport criteria, which include two self-reported questionnaires, isometric quadriceps strength, and 4 single-leg hop tests. Patient-reported fear of re-injury was assessed using the Tampa Scale for Kinesiophobia-11. The results showed that better walking smoothness was moderately correlated with better quadriceps strength and single-leg hop for distance test. In addition, better running smoothness was found to be moderately associated with a higher level of fear of movement/re-injury. No associations were found between movement smoothness during walking fast and running with any of the functional measures. On the other hand, greater between-limb asymmetries in SAV for all gait speeds were moderately to strongly correlated with greater between-limb asymmetries in the quadriceps strength and 4 hop tests. Moreover, running with greater SAV asymmetry was moderately correlated with a higher level of fear of movement/reinjury. Therefore, these findings, particularly the ones from SAV, may provide clinical information regarding functional and psychological status following ACLR. The results of these studies open future research opportunities to investigate the accuracy of gait smoothness and SAV when they are used to identify important biomechanical deficits such as knee flexion angles and knee extensor moments in patients with ACLR. Furthermore, whether patients who present with altered gait smoothness and/or SAV asymmetry are at risk of knee degenerative changes or ACL re-injury should also be investigated in future studies. | |
