Tibiofemoral Contact Measures During Standing in Toe-In and Toe-Out Postures.

Knee osteoarthritis is thought to result, in part, from excessive and unbalanced joint loading. Toe-in and toe-out gait modifications produce alterations in external knee joint moments, and some improvements in pain over the short- and long-term. The aim of this study was to probe mechanisms of altered joint loading through the assessment of tibiofemoral contact in standing with toe-in and toe-out positions using an open magnetic resonance scanner. In this study, 15 young, healthy participants underwent standing magnetic resonance imaging of one of their knees in 3 foot positions. Images were analyzed to determine contact in the tibiofemoral joint, with primary outcomes including centroid of contact and contact area for each compartment and overall. The centroid of contact shifted laterally in the lateral compartment with both toe-in and toe-out postures, compared with the neutral position (P < .01), while contact area in the medial and lateral compartments showed no statistical differences. Findings from this study indicate that changes in the loading anatomy are present in the tibiofemoral joint with toe-in and toe-out and that a small amount of lateralization of contact, especially in the lateral compartment, does occur with these altered lower limb orientations.

Comparison of rates of opioid withdrawal symptoms and reversal of opioid toxicity in patients treated with two naloxone dosing regimens: a retrospective cohort study.

INTRODUCTION: When managing opioid overdose (OD) patients, the optimal naloxone regimen should rapidly reverse respiratory depression while avoiding opioid withdrawal. Published naloxone administration guidelines have not been empirically validated and most were developed before fentanyl OD was common. In this study, rates of opioid withdrawal symptoms (OW) and reversal of opioid toxicity in patients treated with two naloxone dosing regimens were evaluated. METHODS: In this retrospective matched cohort study, health records of patients who experienced an opioid OD treated in two urban emergency departments (ED) during an ongoing fentanyl OD epidemic were reviewed. Definitions for OW and opioid reversal were developed a priori. Low dose naloxone (LDN; ≤0.15 mg) and high dose naloxone (HDN; >0.15 mg) patients were matched in a 1:4 ratio based upon initial respiratory rate (RR). The proportion of patients who developed OW and who met reversal criteria were compared between those treated initially with LDN or HDN. Odds ratios (OR) for OW and opioid reversal were obtained via logistic regression stratified by matched sets and adjusted for age, sex, pre-naloxone GCS, and presence of non-opioid drugs or alcohol. RESULTS: Eighty LDN patients were matched with 299 HDN patients. After adjustment, HDN patients were more likely than LDN patients to have OW after initial dose (OR = 8.43; 95%CI: 1.96, 36.3; p = 0.004) and after any dose (OR = 2.56; 95%CI: 1.17, 5.60; p = 0.019). HDN patients were more likely to meet reversal criteria after initial dose (OR = 2.73; 95%CI: 1.19, 6.26; p = 0.018) and after any dose (OR = 6.07; 95%CI: 1.81, 20.3; p = 0.003). CONCLUSIONS: HDN patients were more likely to have OW but also more likely to meet reversal criteria versus LDN patients.

The Effects of a Heel Wedge on Hip, Pelvis and Trunk Biomechanics During Squatting in Resistance Trained Individuals.

Barbell back squats are a popular exercise for developing lower extremity strength and power. However, this exercise has potential injury risks, particularly to the lumbar spine, pelvis, and hip joint. Previous literature suggests heel wedges as a means of favorably adjusting trunk and pelvis kinematics with the intention of reducing such injury risks. Yet no direct biomechanical research exists to support these recommendations. Therefore, the purpose of this study was to examine the effects of heel wedges compared with barefoot on minimally loaded barbell back squats. Fourteen trained male participants performed a barbell back squat in bare feet or with their feet raised bilaterally with a 2.5-cm wooden block while 3-dimensional kinematics, kinetics, and electromyograms were collected. The heel wedge condition elicited significantly less forward trunk flexion angles at peak knee flexion, and peak external hip joint moments (p ≤ 0.05) compared with barefoot conditions. However, no significant differences were observed between conditions for trunk and pelvis angle differences at peak knee flexion (p > 0.05). Lastly, no peak or root mean square differences in muscle activity were elicited between conditions (p > 0.05). Our results lend support for the suggestions provided in literature aimed at using heel wedges as a means of reducing excessive forward trunk flexion. However, the maintenance of a neutral spine, another important safety factor, is not affected by the use of heel wedges. Therefore, heel wedges may be a viable modification for reduction of excessive forward trunk flexion but not for reduction in relative trunk-pelvis flexion during barbell back squats.

The Biomechanical Demands on the Hip During Progressive Stepping Tasks.

Hatfield, GL, Charlton, JM, Cochrane, CK, Hammond, CA, Napier, C, Takacs, J, Krowchuk, NM, and Hunt, MA. The biomechanical demands on the hip during progressive stepping tasks. J Strength Cond Res 31(12): 3444-3453, 2017-Functional hip strengthening exercises are important components of lower extremity (LE) rehabilitation and include single-leg squats (SLS), step-downs (SD), and step-ups (SU). The biomechanical demand of these tasks is unclear. This repeated-measures study determined hip biomechanical demands in a healthy population. Twenty individuals (10 men, 26.6 ± 5.1 years, 22.1 ± 2.3 kg·m) participated. Three-dimensional motion, ground reaction force data, and surface electromyograms (EMG) were recorded during 4 randomly ordered tasks. Outcomes included frontal and sagittal plane hip moment impulses and muscle activity for each task. Repeated measures analysis of variance models (alpha = 0.05) determined between-task differences. Step-down and SLS were most biomechanically demanding, with significantly higher hip flexion and adduction moment impulses, and gluteus medius (GM) and quadriceps activity compared with half step-down (HSD) and SU. No significant difference was found between SD and SLS, indicating minimal difference in demand between the 2 tasks, likely due to kinematic similarities in performance; there were no significant differences in knee or hip sagittal plane angle excursion, or peak pelvic obliquity angle between the 2 tasks. Step-up was least demanding, with the lowest hip flexion and adduction moment impulses and GM, quadriceps, and hamstrings activity. Step-up was least demanding on the hip and would be a good starting task for hip strengthening protocols. Step-down and SLS were most demanding, requiring higher hip moments and muscle activity. These results provide evidence, which may be used in planning of progressive rehabilitation programs for patients with LE pathologies.

A Pre-Operative Exercise Intervention Can Be Safely Delivered to People with Femoroacetabular Impingement and Improve Clinical and Biomechanical Outcomes.

Purpose: This study aimed to investigate the effects of a pre-hip arthroscopy exercise intervention on hip strength, pain, and function in individuals with femoroacetabular impingement (FAI). Methods: A total of 20 individuals with FAI completed a 10-week, partially supervised exercise programme; this included three phases of increasing resistance and functionality, consisting of four to six exercises per phase. Hip strength in all six directions; hip pain; function, as measured by the Hip disability and Osteoarthritis Outcome Score (HOOS); and objective physical function, as measured by the Timed Stair Climb test, were determined before and after the intervention. Results: Maximum isometric hip strength significantly increased in abduction (p=0.008), adduction (p=0.021), and internal rotation (p=0.006) at follow-up. Increases in flexion, extension, and external rotation strength did not reach statistical significance. Self-reported HOOS pain (p<0.01) and activities of daily living sub-scale scores (p<0.01) significantly improved at follow-up. Timed Stair Climb times (p<0.001) also significantly decreased at follow-up. Conclusion: A 10-week exercise programme can be safely completed by adults with FAI before surgery, and statistically significant changes in strength, function, and self-reported clinical outcomes can be achieved.

Objectif : examiner les effets d'un programme d'intervention préopératoire sur la force, la douleur et la fonction des hanches chez les personnes souffrant d'un conflit fémoro-acétabulaire (CFA). Méthodologie : vingt personnes atteintes d'un CFA ont participé à un programme d'exercice de 10 semaines partiellement supervisé, composé de trois phases de quatre à six exercices de résistance et de fonctionnalité croissantes. La force des hanches dans les six directions, la douleur et la fonction ont été mesurées à l'aide du Hip Disability and Osteoarthritis Outcome Score (score du pronostic d'incapacité et d'arthrose de la hanche) (HOOS) et la fonction physique objective a été mesurée par le test de l'escalier, avant et après l'intervention. Résultats : au suivi, une augmentation statistiquement significative de la force isométrique maximale a été observée pour l'abduction (p=0,008), l'adduction (p=0,021) et la rotation interne (p=0,006). En revanche, l'augmentation de la flexion, de l'extension et de la force de rotation externe n'était pas significative. Les scores des sous-échelles du HOOS pour la douleur autodéclarée (p<0,01) et les activités quotidiennes (p<0,01) ont aussi augmenté de façon significative. Quant aux temps au test de l'escalier (p<0,001) ils ont diminué de façon significative. Conclusion : l'étude démontre qu'un programme d'exercice de 10 semaines peut être suivi de façon sécuritaire par des adultes atteints d'un CFA avant la chirurgie et qu'il peut permettre d'améliorer de façon significative la force, la fonction et les résultats cliniques autodéclarés.

Knee and ankle biomechanics with lateral wedges with and without a custom arch support in those with medial knee osteoarthritis and flat feet.

UNLABELLED: This study compared immediate changes in knee and ankle/subtalar biomechanics with lateral wedge orthotics with and without custom arch support in people with knee osteoarthritis and flat feet. Twenty-six participants with radiographic evidence of medial knee osteoarthritis (22 females; age 64.0 years [SD 8.0 years], BMI 27.2 kg/m(2) [4.2]) and flat feet (median foot posture index = + 5) underwent three-dimensional gait analysis for three conditions: Control (no orthotic), lateral wedge, and lateral wedge plus arch support. Condition order was randomized. Outcomes included frontal plane knee and ankle/subtalar biomechanics, and comfort. Compared to the control, lateral wedge and lateral wedge with arch support reduced the knee adduction moment impulse by 8% and 6%, respectively (p < 0.05). However, the lateral wedge resulted in a more everted foot position (4.3 degrees) than lateral wedge plus arch support (3.2 degrees) (p < 0.05). In contrast, lateral wedge plus arch support reduced foot frontal plane excursion compared to other conditions (p < 0.05). Participants self-reported significantly more immediate comfort with lateral wedge plus arch support compared to the control, whereas there was no difference in self-reported comfort between lateral wedge and control. No immediate changes in knee pain were observed in any condition. CLINICAL SIGNIFICANCE: Rather than prescribing lateral wedges to all patients with knee osteoarthritis, those who have medial knee osteoarthritis and flat feet may prefer to use the combined orthotic to reduce loads across the knee, and to minimize the risk of foot and ankle symptoms as a consequence of orthotic treatment. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1597-1605, 2016.

Motor Planning for Loading During Gait in Subacute Stroke.

OBJECTIVES: To determine the characteristics of motor planning surrounding initial contact during gait through examination of thigh muscle timing, amplitude, and co-contraction of the paretic and nonparetic limbs in people poststroke, and to investigate whether muscle timing, amplitude, and clinical performance measures of balance and mobility differ based on the level of co-contraction. DESIGN: Observational study. SETTING: University-based research laboratory. PARTICIPANTS: Individuals (n=27) in the subacute phase after stroke and healthy controls (n=8) (N=35). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Timing (onset and offset) and normalized amplitude (percent electromyography maximum) of the biceps femoris (BF) and rectus femoris (RF) muscles were measured during terminal swing and early stance. A co-contraction index (CCI) was calculated for the BF and RF muscle activity. Individuals with CCI values equal to or below the mean of the healthy group were in the low CCI group, whereas those with values above the mean were in the high CCI group. Functional balance and mobility evaluation used the Community Balance and Mobility Scale (CB&M). RESULTS: For the paretic and nonparetic limbs, measures of timing, amplitude, and co-contraction were similar for both limbs. Compared with the healthy group, the high CCI group had lower CB&M scores, longer durations, and higher levels of RF and BF muscle activity, whereas the low CCI group had electromyographic measures statistically similar to healthy controls. CONCLUSIONS: The motor control of gait after subacute stroke is characterized by symmetry of timing and amplitude of muscle recruitment at the knee. High co-contraction levels surrounding the knee were associated with lower functional balance and mobility. These findings suggest a compensatory strategy of increased co-contraction in those with more impairment while maintaining symmetry of lower-limb biomechanics between limbs.

Gait modifications to change lower extremity gait biomechanics in runners: a systematic review.

BACKGROUND: Abnormal biomechanics have been cited as a potential risk factor for running-related injury. Many modifiable biomechanical risk factors have also been proposed in the literature as interventions via gait retraining. AIM: To determine which interventions have successfully modified biomechanical variables linked to running-related injury. STUDY DESIGN: Systematic literature review. METHODS: MEDLINE, EMBASE, CINAHL, SportDiscus and PSYCINFO were searched using key terms related to running biomechanics and gait retraining. Quality of included studies was assessed using the modified Downs and Black Quality Index and a best evidence synthesis was performed. RESULTS: 27 studies investigating the effect of biomechanical interventions on kinetic, kinematic and spatiotemporal variables were included in this review. Foot strike manipulation had the greatest effect on kinematic measures (conflicting evidence for proximal joint angles; strong evidence for distal joint angles), real-time feedback had the greatest effect on kinetic measures (ranging from conflicting to strong evidence), and combined training protocols had the greatest effect on spatiotemporal measures (limited to moderate evidence). CONCLUSIONS: Overall, this systematic review shows that many biomechanical parameters can be altered by running modification training programmes. These interventions result in short term small to large effects on kinetic, kinematic and spatiotemporal outcomes during running. In general, runners tend to employ a distal strategy of gait modification unless given specific cues. The most effective strategy for reducing high-risk factors for running-related injury-such as impact loading-was through real-time feedback of kinetics and/or kinematics.

Biomechanical mechanisms of toe-out gait performance in people with and without knee osteoarthritis.

BACKGROUND: Toe-out gait modification (increased toe-out angle) has been proposed to decrease medial knee joint loading and slow disease progression in patients with knee osteoarthritis. However, the manner in which toe-out gait modification is performed is unknown. The purposes of this study were to assess the biomechanical strategies of achieving a toe-out gait, and to compare these strategies between older individuals with knee osteoarthritis and young, healthy individuals. METHODS: Lower limb biomechanics were evaluated for ten patients with knee osteoarthritis and for ten young, healthy individuals during treadmill walking. Two trials, consisting of natural gait followed by a ten degree increase in toe-out angle were performed. Transverse plane rotations of the thigh, shank and foot segments were calculated and compared between walking conditions and groups. FINDINGS: External rotation changes with toe-out were significantly different between the thigh and shank, and thigh and foot (P<0.001), but not between the shank and foot (P=0.48). External rotation at each segment was not significantly different (P>0.05) between groups, with the exception of thigh rotation during natural gait (P=0.04). INTERPRETATION: Current findings suggest that increased toe-out gait is primarily achieved through rotation of the shank and foot, with less contribution from the thigh, and those individuals with knee osteoarthritis perform a toe-out gait biomechanically similar to young, healthy individuals. Gait modification programs should address individuals' limitations, such as joint stiffness, to ensure functional performance of toe-out gait modification.