Mechanisms for the functional differentiation of the propulsive and braking roles of the forelimbs and hindlimbs during quadrupedal walking in primates and felines.

During quadrupedal walking in most animals, the forelimbs play a net braking role, whereas the hindlimbs are net propulsive. However, the mechanism by which this differentiation occurs remains unclear. Here, we test two models to explain this pattern using primates and felines: (1) the horizontal strut effect (in which limbs are modeled as independent struts), and (2) the linked strut model (in which limbs are modeled as linked struts with a center of mass in between). Video recordings were used to determine point of contact, timing of mid-stance, and limb protraction/retraction duration. Single-limb forces were used to calculate contact time, impulses and the proportion of the stride at which the braking-to-propulsive transition (BP) occurred for each limb. We found no association between the occurrence of the BP and mid-stance, little influence of protraction and retraction duration on the braking-propulsive function of a limb, and a causative relationship between vertical force distribution between limbs and the patterns of horizontal forces. These findings reject the horizontal strut effect, and provide some support for the linked strut model, although predictions were not perfectly matched. We suggest that the position of the center of mass relative to limb contact points is a very important, but not the only, factor driving functional differentiation of the braking and propulsive roles of the limbs in quadrupeds. It was also found that primates have greater differences in horizontal impulse between their limbs compared with felines, a pattern that may reflect a fundamental arboreal adaptation in primates.

Effects of Neuromuscular Training on the Rear-foot Angle Kinematics in Elite Women Field Hockey Players with Chronic Ankle Instability.

The aims of this study were to investigate the ankle position, the changes and persistence of ankle kinematics after neuromuscular training in athletes with chronic ankle instability (CAI). A total of 21 national women's field hockey players participated (CAI = 12, control = 9). Ankle position at heel strike (HS), midstance (MS), and toe touch (TT) in the frontal plane during walking, running and landing were measured using 3D motion analysis. A 6-week neuromuscular training program was undertaken by the CAI group. Measurements of kinematic data for both groups were measured at baseline and the changes in kinematic data for CAI group were measured at 6 and 24 weeks. The kinematic data at HS during walking and running demonstrated that the magnitude of the eversion in the CAI group (-5.00° and -4.21°) was less than in the control group (-13.45°and -9.62°). The kinematic data at MS also exhibited less ankle eversion in the CAI group (-9.36° and -8.18°) than in the control group (-18.52° and -15.88°). Ankle positions at TT during landing were comparable between groups. Following the 6-week training, the CAI participants demonstrated a less everted ankle at HS during walking and running (-1.77° and -1.76°) compared to the previous positions. They also showed less ankle eversion at MS (-5.14° and -4.19°). Ankle orientation at TT changed significantly to an inverted ankle position (from -0.26° to 4.11°). The ankle kinematics were restored back to the previous positions at 24 weeks except for landing. It appeared that athletes with unstable ankle had a relatively inverted ankle position, and that 6-week neuromuscular training had an immediate effect on changing ankle orientation toward a less everted direction. The changed ankle kinematics seemed to persist during landing but not during walking and running.

End-stage ankle arthritis alters dynamic stability during gait as measured by margin of stability between limbs and compared to healthy controls.

OBJECTIVE: This study aimed to assess dynamic stability in individuals with end-stage ankle arthritis compared to healthy controls by evaluating the margin of stability (MoS) during gait. DESIGN: A cohort of 50 participants with end-stage ankle arthritis (AA) and 50 matched healthy controls (HC) were analyzed from an IRB approved database. Kinematic data were collected using an eight-camera motion analysis system, and MoS was calculated based on the extrapolated center of mass (XCoM) and the base of support (BoS). Statistical analysis was performed using a linear mixed effects model with gait speed as a covariate. RESULTS: The analysis revealed a significant interaction between the group (AA vs. HC) and limb (arthritic vs. non-arthritic) at heel-strike and midstance. The non-arthritic limb demonstrated a significantly smaller AP MoS during heel-strike compared to the arthritic limb and either of the limbs of the HC group (p < 0.001). The arthritic limb demonstrated a significantly greater ML MoS during midstance compared to the non-arthritic limb and either of the limbs of the HC group (p < 0.001). AA group had significant slower gait speed (p < 0.001), smaller step length (p = 0.015) and smaller locomotor rehabilitation index (p < 0.001) than HC. CONCLUSION: Individuals with end-stage ankle arthritis exhibit altered dynamic stability during gait, with a significantly smaller AP MoS on the non-arthritic limb at heel-strike and greater ML MoS on the arthritic limb at midstance compared to healthy controls. Our results suggest that individuals with ankle arthritis are less stable when navigating single limb support of the arthritic limb. Further research should further examine the associations with fall risk in patients with ankle arthritis and evaluate the effectiveness of therapeutic interventions targeting these factors.

Do lateral ankle ligaments contribute to syndesmotic stability: a finite element analysis study.

Whether the lateral ankle ligaments contribute to syndesmotic stability is still controversial and has been the subject of frequent research recently. In our study, we tried to elucidate this situation using the finite element analysis method. Intact model and thirteen different injury models were created to simulate injuries of the lateral ankle ligaments (ATFL, CFL, PTFL), injuries of the syndesmotic ligaments (AITFL, IOL, PITFL) and their combined injuries. The models were compared in terms of LFT, PFT and EFR. It was observed that 0.537 mm LFT, 0.626 mm PFT and 1.25° EFR occurred in the intact model (M#1), 0.539 mm LFT, 0.761 mm PFT and 2.31° EFR occurred in the isolated ATFL injury (M#2), 0.547 mm LFT, 0.791 mm PFT and 2.50° EFR occurred in the isolated AITFL injury (M#8). The LFT, PFT and EFR amounts were higher in the both M#2 and M#8 compared to the M#1. LFT, PFT and EFR amounts in M#2 and M#8 were found to be extremely close. In terms of LFT and PFT, when we compare models with (LFT: 0.650 mm, PFT: 1.104) and without (LFT: 0.457 mm, PFT: 1.150) IOL injury, it is seen that the amount of LFT increases and the amount of PFT decreases with IOL injury. We also observed that injuries to the CFL, PTFL and PITFL did not cause significant changes in fibular translations and PFT and EFR values show an almost linear correlation. Our results suggest that ATFL injury plays a crucial role in syndesmotic stability.

Hip Joint Abnormalities During Midstance in Osteoarthritic Patients.

Osteoarthritis is one of the most debilitating diseases in Europe affecting the lower limb joints, especially the hip and knee, having a bad influence on gait in the long run as well. Rehabilitation physicians use gait in order for the whole body to be seen in ensemble, and through midstance as moment of gait to also take predilection to falls into consideration. Goniometry is the quantifiable measure of a rehabilitation treatment by measuring the range of motion of each treated joint and studied during time. The patients that volunteered to be part of this study have been divided into four groups, depending on the level of osteoarthritis present at the lower limb joints: hip, knee, both hip and knee osteoarthritis or control group with no osteoarthritis, have been asked to walk for a few times and the video recordings were uploaded into the Angles App where we measured the lower limb joint angles during midstance. Patients with knee osteoarthritis present a more extended hip on both dominant and non-dominant sides compared to the ones with hip osteoarthritis, hip and knee osteoarthritis or control group. The results can be explained through the body's kinematic chains that link the knee and hip, hip and pelvis during the midstance phase in the sagittal plane. A physician can use a video goniometry app in order for him to thoroughly evaluate an osteoarthritic patient as well as follow him or her during the entire course of treatment.

A progressive-individualized midstance gait perturbation protocol for reactive balance assessment in stroke survivors.

Restoration of balance control is a primary focus of rehabilitation after a stroke. The study developed a gait perturbation, treadmill-based, balance assessment protocol and demonstrated that it can be used to quantify improvements in reactive balance responses among individuals post-stroke. The protocol consists of a sequence of fifteen 90-second treadmill walking trials, with a single perturbation applied during the middle third of each trial. Gait was perturbed by rapid acceleration-deceleration of the treadmill belt at mid-stance of the unaffected leg during a randomly selected gait cycle. The initial perturbation magnitude was based on the participant's maximum walking speed and increased or decreased in each trial, based on success or failure of recovery, as determined from an instrumented harness. The protocol was used before and after a 10-week period of therapy in twenty-four stroke survivors. Outcomes included maximum recoverable perturbation (MRP), self-selected gait speed, levels progressed through the algorithm, and falls versus recoveries.Participants were able to take recovery steps in response to the perturbation. Twelve participants completed the full assessment protocol before and after the therapeutic intervention. After the intervention, they had fewer falls and more recoveries (p < 0.001), progressed through more algorithm levels (p = 0.043), had a higher MRP (p = 0.005), and had higher gait speeds. The protocol was found to be feasible in stroke survivors with moderate gait deficits. The data supports the conclusion that this protocol can be used in clinical research to quantify improvements in balance during walking.

Midstance hamstring length is a better indicator for hamstring lengthening procedures than initial contact length.

BACKGROUND: Children with static encephalopathy often walk with excessive knee and hip flexion throughout the gait cycle. This crouch gait pattern can be debilitating. These children may undergo hamstring-lengthening procedures to correct this crouch gait. Some improve, while others remain in crouch gait or go into knee hyperextension postoperatively, which can ultimately be debilitating. RESEARCH QUESTION: Hamstring muscle-tendon length models are frequently used as indicators when making recommendations for or against hamstring lengthening procedures. According to the literature, most clinicians use the length of the hamstring complex at the initial contact phase of the gait cycle as the primary deciding factor. We hypothesize that the length of this muscle-tendon complex at the midstance phase of the gait cycle is a more stringent criteria for lengthening procedures. METHODS: A simplified hamstring length model was applied retrospectively to the pre and postoperative three dimensional gait analysis kinematics of 152 subjects to assess preoperative surgical indications and postoperative outcomes. RESULTS: Of the limbs with short hamstrings at initial contact preoperatively, 15% went into knee hyperextension following hamstring lengthening procedures. Cases of hyperextension were even higher (19%) if the hamstrings were also normal to long at midstance. If the hamstrings were short at midstance, only 6 % went into hyperextension. Increasing the criteria to short hamstrings at initial contact and midstance reduced the number of limbs with hyperextension to 0%. SIGNIFICANCE: It appears that the length of the hamstrings at midstance is an additional predictor of the risk of post-op knee hyperextension from hamstring lengthening procedures, than utilizing the length at initial contact alone. Even though short hamstrings at midstance may be an additional predictor of positive outcomes, it also results in a more conservative approach to surgery by excluding almost half of the patients with short hamstrings at initial contact only, but who may benefit from surgery.