Long-term Gait Deviations in ACL-Reconstructed Females
Long-term Gait Deviations in ACL-Reconstructed Females
Purpose: Little is known of the potential long-term gait alterations that occur after an anterior cruciate ligament (ACL) reconstruction. In particular, variables, such as impact loading, which have been previously associated with joint deterioration, have not been studied in walking and running after an ACL reconstruction. The purpose of this study was to define the alterations in impact forces, loading rates, and the accompanying sagittal plane kinematic and kinetic mechanics at the time of impact between the ACL-reconstructed group and a healthy control group.
Methods: Forty females (20 with ACL reconstruction and 20 controls) participated in the study. An instrumented gait analysis was performed on all subjects. Between-group and between-limb comparisons were made for the initial vertical impact force, loading rate, and sagittal plane knee and hip angles as well as moments.
Results: During walking and running, the ACL cohort had significantly greater initial vertical impact force (P = 0.002 and P = 0.001, respectively) and loading rates (P = 0.03 and P = 0.0111, respectively), as well as a smaller knee extensor moment and hip angle during walking (P = 0.000 and P = 0.01, respectively). There was a trend toward a smaller knee moment and hip angle during running (P = 0.08 and P = 0.06, respectively) as well as a larger hip extensor moment during walking (P = 0.06) in the ACL group. No differences were found for hip extensor moment during running and for knee angles between groups during walking or running. Lastly, no between-limb differences were found for any variable.
Conclusions: Gait deviations such as elevated impact loading and loading rates do not resolve long term after an individual has resumed previous activity levels and these may contribute to the greater risk of early joint degeneration in this population.
An estimated 250,000 anterior cruciate ligament (ACL) tears occur annually. This injury also disproportionately affects females participating in sports involving jumping and pivoting, who are at a four to six times greater risk of suffering an ACL tear. The postsurgical management of these patients is associated with a long and extensive period of rehabilitation. Although good clinical results are reported, there are well-documented deficits in quadriceps strength and functional performance during tasks, such as jumping, which persist even after rehabilitation has completed. Comparatively, however, little is still known of the long-term alterations in gait. For instance, early after surgical reconstruction, reductions in the knee extensor moment during early stance in walking and jogging have been reported. Such a gait pattern has been speculated to lead to greater initial impact forces and loading rates in the post-ACL-reconstructed patient. These forces are thought to be one of the contributing factors to the deterioration of the tibiofemoral joint after an ACL reconstruction. In fact, elevated impact forces and loading rates have been previously associated with cartilage degeneration, subchondral bone stiffening, and have been observed in individuals with established tibiofemoral osteoarthritis (OA). Evidence of long-term increases in the initial impact forces in the post-ACL-reconstructed patient has to date been limited to one small study. Although jump landing kinematics and muscular control during jump tasks have been studied extensively, very little is known about impact forces and the associated kinematics and kinetics of walking after ACL injury. This is surprising because these are the earliest and most common activities that ACL-injured patients return to after surgery. Given that an average adult takes between 5000 and 7000 steps per day, even slight adaptations in these variables could have a significant cumulative effect on an already vulnerable knee.
Healthy cohorts demonstrate a more extended knee angle, and a smaller knee extension moment in early stance during loading response is associated with greater vertical impact peak loading. This is concerning because reduced knee extensor moments are common in individuals who have undergone ACL reconstruction. Further investigation into these findings, particularly with emphasis on the sagittal plane mechanics at the hip and knee during early stance could provide important insights into the control of initial impact loading during gait after an ACL reconstruction. Identification of the potential modifiable kinematic and kinetic alterations that occur at initial impact could provide a focus for developing new treatments to teach patients to reduce impact loading during gait after an ACL reconstruction.
The identification of potential long-term gait adaptations after an ACL reconstruction requires the assessment of both walking and running. For instance, the differing muscular demands and gait mechanics between walking and running may make it easier to maintain compensations during walking but not running. Such a finding could suggest that long-term adaptations are task dependent. Conversely, if compensations are found in both walking and running then this could suggest a global reorganization of neuromuscular control of gait that is not task dependent. Lastly, although differences in loading rates have been reported in other tasks such as drop vertical jumps, there have been no comparisons of the differences in initial impact loading and associated sagittal plane adaptations in walking and running after an ACL reconstruction.
Therefore, the purpose of this study was twofold. The first was to compare the initial impact forces and vertical loading rates, between those who have had an ACL reconstruction to uninjured individuals. The second purpose was to identify the alterations in the sagittal plane hip and knee angles as well as moments that occur during initial impact loading. We hypothesized that, during walking and running, the operative limb would have a greater impact peak force and loading rate compared to their nonoperative limb and a healthy control group. We also hypothesized that there would be smaller hip flexion and knee flexion angles, a smaller knee extensor moment, and a larger hip extensor moment at the time of initial impact peak in the involved limb when compared to their nonoperative limb and a healthy control group.
Abstract and Introduction
Abstract
Purpose: Little is known of the potential long-term gait alterations that occur after an anterior cruciate ligament (ACL) reconstruction. In particular, variables, such as impact loading, which have been previously associated with joint deterioration, have not been studied in walking and running after an ACL reconstruction. The purpose of this study was to define the alterations in impact forces, loading rates, and the accompanying sagittal plane kinematic and kinetic mechanics at the time of impact between the ACL-reconstructed group and a healthy control group.
Methods: Forty females (20 with ACL reconstruction and 20 controls) participated in the study. An instrumented gait analysis was performed on all subjects. Between-group and between-limb comparisons were made for the initial vertical impact force, loading rate, and sagittal plane knee and hip angles as well as moments.
Results: During walking and running, the ACL cohort had significantly greater initial vertical impact force (P = 0.002 and P = 0.001, respectively) and loading rates (P = 0.03 and P = 0.0111, respectively), as well as a smaller knee extensor moment and hip angle during walking (P = 0.000 and P = 0.01, respectively). There was a trend toward a smaller knee moment and hip angle during running (P = 0.08 and P = 0.06, respectively) as well as a larger hip extensor moment during walking (P = 0.06) in the ACL group. No differences were found for hip extensor moment during running and for knee angles between groups during walking or running. Lastly, no between-limb differences were found for any variable.
Conclusions: Gait deviations such as elevated impact loading and loading rates do not resolve long term after an individual has resumed previous activity levels and these may contribute to the greater risk of early joint degeneration in this population.
Introduction
An estimated 250,000 anterior cruciate ligament (ACL) tears occur annually. This injury also disproportionately affects females participating in sports involving jumping and pivoting, who are at a four to six times greater risk of suffering an ACL tear. The postsurgical management of these patients is associated with a long and extensive period of rehabilitation. Although good clinical results are reported, there are well-documented deficits in quadriceps strength and functional performance during tasks, such as jumping, which persist even after rehabilitation has completed. Comparatively, however, little is still known of the long-term alterations in gait. For instance, early after surgical reconstruction, reductions in the knee extensor moment during early stance in walking and jogging have been reported. Such a gait pattern has been speculated to lead to greater initial impact forces and loading rates in the post-ACL-reconstructed patient. These forces are thought to be one of the contributing factors to the deterioration of the tibiofemoral joint after an ACL reconstruction. In fact, elevated impact forces and loading rates have been previously associated with cartilage degeneration, subchondral bone stiffening, and have been observed in individuals with established tibiofemoral osteoarthritis (OA). Evidence of long-term increases in the initial impact forces in the post-ACL-reconstructed patient has to date been limited to one small study. Although jump landing kinematics and muscular control during jump tasks have been studied extensively, very little is known about impact forces and the associated kinematics and kinetics of walking after ACL injury. This is surprising because these are the earliest and most common activities that ACL-injured patients return to after surgery. Given that an average adult takes between 5000 and 7000 steps per day, even slight adaptations in these variables could have a significant cumulative effect on an already vulnerable knee.
Healthy cohorts demonstrate a more extended knee angle, and a smaller knee extension moment in early stance during loading response is associated with greater vertical impact peak loading. This is concerning because reduced knee extensor moments are common in individuals who have undergone ACL reconstruction. Further investigation into these findings, particularly with emphasis on the sagittal plane mechanics at the hip and knee during early stance could provide important insights into the control of initial impact loading during gait after an ACL reconstruction. Identification of the potential modifiable kinematic and kinetic alterations that occur at initial impact could provide a focus for developing new treatments to teach patients to reduce impact loading during gait after an ACL reconstruction.
The identification of potential long-term gait adaptations after an ACL reconstruction requires the assessment of both walking and running. For instance, the differing muscular demands and gait mechanics between walking and running may make it easier to maintain compensations during walking but not running. Such a finding could suggest that long-term adaptations are task dependent. Conversely, if compensations are found in both walking and running then this could suggest a global reorganization of neuromuscular control of gait that is not task dependent. Lastly, although differences in loading rates have been reported in other tasks such as drop vertical jumps, there have been no comparisons of the differences in initial impact loading and associated sagittal plane adaptations in walking and running after an ACL reconstruction.
Therefore, the purpose of this study was twofold. The first was to compare the initial impact forces and vertical loading rates, between those who have had an ACL reconstruction to uninjured individuals. The second purpose was to identify the alterations in the sagittal plane hip and knee angles as well as moments that occur during initial impact loading. We hypothesized that, during walking and running, the operative limb would have a greater impact peak force and loading rate compared to their nonoperative limb and a healthy control group. We also hypothesized that there would be smaller hip flexion and knee flexion angles, a smaller knee extensor moment, and a larger hip extensor moment at the time of initial impact peak in the involved limb when compared to their nonoperative limb and a healthy control group.
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