Ryan T. Lewinson

The effects of wedged footwear on lower limb frontal plane biomechanics during running.

Objective:Patellofemoral pain syndrome (PFPS), the most common running injury, has been associated with increased internal knee abduction angular impulses (KAAI). Wedged footwear can reduce these impulses during walking, but their effects during running are not well understood. The purpose of this study was to identify the effects of wedged footwear on KAAIs and describe the mechanism by which wedged footwear alters KAAIs during running. Design:Controlled laboratory study. Setting:Motion analysis laboratory. Participants:Nine healthy male subjects. Interventions:Participants ran at a speed of 4 m/s with 7 different footwear conditions (3-, 6-, and 9-mm lateral wedges; 3-, 6-, and 9-mm medial wedges; neutral). Main Outcome Measures:Knee abduction angular impulses and 8 predictor variables were measured and compared by 1-way repeated measures analysis of variance (&agr; = 0.05) with Bonferroni-adjusted 2-tailed paired t tests for post hoc analysis (&agr; = 0.002). Correlation (&agr; = 0.05) was used to determine the relationship between the mediolateral center of pressure to ankle joint center (COP-AJC) lever arm length and KAAIs. Results:Laterally wedged conditions produced significantly lower KAAIs (P = 0.001) than medial wedge conditions. Peak knee abduction moments decreased (P = 0.001), whereas ankle inversion moments (P = 0.041) and the COP-AJC lever arms increased (P < 0.001) as wedges progressed from medial to lateral. KAAIs were negatively correlated with COP-AJC lever arm length (r = −0.50, P < 0.001). Conclusions:KAAIs are reduced with laterally wedged footwear because of lateral shifts in the center of pressure beneath the foot, which then increases ankle inversion moments and decreases peak knee abduction moments. Laterally wedged footwear may therefore offer greater relief to runners with PFPS than medially wedged footwear by reducing KAAIs.

Shoe traction and surface compliance affect performance of soccer-related movements

Purpose: To determine how shoe-surface interaction, specifically traction and compliance, affects performance and biomechanics of soccer-related movements. Methods: Third generation artificial turf was installed in the laboratory to allow for kinetic and kinematic data collection both on the turf and on a laboratory surface (Pulastic sports surface). Twelve male athletes performed five 5 m sprint accelerations and five 180° sprint turns in three different shoe-surface conditions (indoor soccer shoe on the laboratory surface, indoor soccer shoe on the turf surface, soccer cleat on turf surface). Comparisons between the indoor shoe across surfaces indicated compliance effects and comparisons between the cleat and indoor shoe on turf indicated traction effects. Results: Performance increased for the sprint acceleration in the indoor shoe on the turf compared to the laboratory (1.04 s vs. 1.08 s); however, no further increase in acceleration performance occurred with the soccer cleat. For the turn movement, no change in performance occurred comparing the indoor shoe across surfaces however an increase in turn performance was seen when using the soccer cleat on turf compared to the indoor shoe (2.67 s vs. 2.56 s). The cleat had both increased utilised translational and rotational traction compared to the indoor shoe on turf for the turn movement. The cleat also resulted in increased ankle eversion moments as well as increased knee abduction and external rotation moments compared to the indoor shoe on the turf surface for the turn movement. Conclusion: Both compliance and traction shoe-surface characteristics affect performance; however, the effects of the different characteristics are different depending on the movement type.

Control conditions for footwear insole and orthotic research

Footwear insoles/orthotics alter variables associated with musculoskeletal injury; however, their clinical effectiveness is inconclusive. One explanation for this is the possibility that control conditions may actually produce biomechanical changes that induce clinical responses. The purpose of this study was to compare insole/orthotic control conditions to identify if variables at the ground, ankle and knee that are associated with injury are altered relative to what participants would normally experience in their own shoes. Gait analysis was performed on 15 participants during walking and running while wearing (1) their own shoes, (2) #1 with a 3mm flat insole, (3) a standardized shoe, and (4) #3 with a 3mm flat insole, where external knee adduction moments, external knee adduction angular impulses, internal ankle inversion moments, and vertical ground reaction force loading rates were determined. Conditions 2-4 were expressed as percent changes relative to condition 1, and tests of proportions assessed if there were a significant number of individuals experiencing a biomechanically relevant change for each variable. Repeated-measures ANOVAs were used to identify group differences between conditions. The majority of movement-footwear-variable combinations contained a proportion of individuals experiencing biomechanically relevant changes compared to condition 1 that was significantly greater than the expected proportion of 20%. No systematic differences were found between conditions. This suggests that conditions 2-4 may alter biomechanics relative to baseline for many participants, but not in a consistent way across participants. It is recommended that participants own footwear be used as control conditions in future trials where biomechanics are primary variables of interest.

The Canadian MD/PhD training program needs reinstated support.

The Canadian Institutes of Health Research (CIHR) recently terminated its MD/PhD training program without clear alternative funding in place. This misguided decision must urgently be reversed, as it has the potential to diminish a unique pool of graduates at the forefront of translational research.

Calculation of external knee adduction moments: A comparison of an inverse dynamics approach and a simplified lever-arm approach

BACKGROUND The external knee adduction moment (EKAM) is often studied in knee osteoarthritis research. This study compared EKAMs between two methods of calculation: a method that only requires ground reaction force and knee position data (i.e. lever-arm), and an inverse dynamics link-segment method. METHODS Sixteen participants walked while wearing a control shoe with and without a six millimeter lateral wedge insole. Peak EKAMs between the lever-arm and inverse dynamics methods were compared for the control condition, and the %change in moment induced by the lateral wedge was compared between methods. RESULTS When comparing EKAMs between methods, no correlation was found (r=0.24, p=0.36); peak EKAMs with the lever-arm method (26.0Nm) were significantly lower than EKAMs with the inverse dynamics method (40.2Nm, pb0.001); and Bland-Altman plots showed poor agreement between methods. When assessing the %change in moment with a lateral wedge, a moderate correlation was found (r=0.55, p=0.03) between methods; Bland-Altman plots showed moderate agreement between methods; and the lever-arm method (-6.4%) was not significantly different from the inverse dynamics method (-11.4%, p=0.09); however, the two methods produced opposite results 31% of the time. CONCLUSION The lever-arm method cannot estimate peak EKAMs, and can only approximate the %change in moment induced by a lateral wedge; however, the error rate was 31%. Therefore, the lever-arm method is not recommended for use in its current form. CLINICAL RELEVANCE This study may help guide the development of a fast and simple method for determining EKAMs for individuals with knee osteoarthritis.

Wedged Insoles and Gait in Patients with Knee Osteoarthritis: A Biomechanical Review

The study of gait biomechanics in individuals with knee osteoarthritis has become widespread, especially in regards to the knee adduction moment—a variable commonly believed to be associated with knee osteoarthritis progression. Unfortunately, this variable is often studied clinically without considering how it is derived, or what it means in a mechanical context. The use of footwear for knee osteoarthritis management has received much attention as well. However, in many cases, footwear is studied without regard for the mechanical effects they actually induce on the patient. Therefore, this review aims to summarize the current state of knowledge in regards to knee osteoarthritis gait and footwear biomechanics, by taking a step back to review the foundations of these two research areas. First, an overview of the calculation of the knee adduction moment is provided, along with mechanical considerations. Then, this is used to discuss current evidence for wedged insoles and highlight knowledge gaps. The intent was to place this mechanical information in a clinically-oriented framework for approachability by scientists, engineers and clinicians alike. Based on this discussion, areas for future investigation are proposed.

The relationship between maximal hip abductor strength and resultant loading at the knee during walking.

The peak external knee adduction moment (KAM) is implicated in progression of knee osteoarthritis (OA). Recently, hip abductor weakness has also been found in patients with knee OA; however, it remains unknown as to how or if this weakness is a consequence of OA, or a predisposing factor. If it is the latter, a direct relationship between hip strength and KAM magnitude would be expected. The purpose of this study was to evaluate the relationship between hip abductor strength and KAM magnitude during walking. In fourteen adults, maximal isometric hip abductor strength was measured, and the KAM was quantified during gait. Additionally, internal hip abductor moments, vertical and medial ground-reaction-forces (GRFs), and GRF to knee joint center lever-arms were quantified during gait. The relationship between hip strength and GRFs, lever-arms and KAM were assessed using correlation. Internal hip abductor moments were compared to maximum hip strength by paired samples t-test. Correlations between hip strength and the vertical GRF (r = −0.05, p = 0.87), medial GRF (r = −0.24, p = 0.41), lever arm (r = −0.01, p = 0.97), and KAM (r = −0.24, p = 0.41) were not statistically significant. Peak internal hip abductor moments during gait (1.1 ± 0.2 Nm/kg) were significantly lower than maximal hip abductor strength (1.8 ± 0.3 Nm/kg, p < 0.001). It is concluded that hip abductor strength is not related to KAM magnitude. It seems more likely that hip abductor weakness is a consequence of OA rather than a predisposing factor.

Risk of depression among patients with acne in the U.K.: a population‐based cohort study

DEAR EDITOR, Acne has been associated with adverse psychiatric symptoms. In dermatology outpatient clinics, approximately 25.2% of patients with acne experience some psychiatric morbidity. However, few studies have evaluated the clinically significant diagnostic category of major depressive disorder (MDD) among people with acne. Here, we investigated whether patients with acne are at an increased risk of developing MDD compared to the general population, using one of the largest electronic medical records databases in the world. A retrospective cohort study was conducted using data from The Health Improvement Network (THIN) (1986–2012), a large primary care database in the U.K. that also includes data from specialists. All individuals between 7 and 50 years of age with ≥ 1 Read codes (diagnostic codes linked to International Classification of Diseases codes) for acne were identified. A general population cohort without acne was also identified. The study was approved by the Conjoint Health Research Ethics Board at the University of Calgary (ID 24423) and from the Scientific Review Committee in the U.K. (ID 16THIN036), authorizing access to extract relevant data from THIN. A complete list of codes used to identify exposures, outcomes and covariates is available from the authors. All patients were followed from their start date for ≥ 2 years in THIN until the earliest of either their first MDD Read code (main outcome), transfer out of practice, death or end of data collection. Observations were censored at the end of follow-up in patients where MDD was not observed during the study period. To identify only incident cases, patients with an acne or MDD Read code prior to the start of follow-up were excluded. Baseline covariates at the start of follow-up included age (young ≤ 19; adult > 19 years), sex, obesity (BMI ≥ 30 kg m ), smoking status (never, former, current), alcohol use (yes or no), medical comorbidities using the Charlson Comorbidity Index (0 or ≥ 1 comorbidity) and socioeconomic status using the Townsend Deprivation Index (quintiles 1–5, with 1 least and 5 most deprivation).

Prediction of knee joint moment changes during walking in response to wedged insole interventions

Wedged insoles are prescribed for medial knee osteoarthritis to reduce the knee adduction moment; however, it is currently not possible to predict which patients will in fact experience reduced moments. The purpose of this study was to identify a simple method using two-dimensional data for predicting the expected change in knee adduction moments with wedged insoles. Knee adduction moments during walking were determined for healthy individuals (n = 15) and individuals with medial knee osteoarthritis (n = 19) while wearing their own shoe without an insole (control), with a 6-mm medial wedge and with a 6-mm lateral wedge. The percent changes relative to control were determined. Then, participants completed single-step trials with each footwear condition where only the changes in mediolateral positions of the knee joint center, shank center of mass, ankle joint center, and foot center of mass relative to control were determined. These variables were used as predictors in regression equations where the change in knee adduction moment during walking was the dependent variable. The change in mediolateral positions of the lower extremity during a single step significantly predicted the change in knee adduction moment during walking for the lateral wedge in both the healthy (R2 = 0.72, p = 0.008) and knee osteoarthritis (R2 = 0.52, p = 0.026) groups, and also for the medial wedge in both the healthy (R2 = 0.67, p = 0.016) and knee osteoarthritis (R2 = 0.54, p = 0.020) groups. The method of using mediolateral position data from a single-step movement to predict walking biomechanics was successful. These data are relatively simple to collect and analyze, offering the possibility for future incorporation into a wedge prediction system.

Reduced knee adduction moments for management of knee osteoarthritis:: A three month phase I/II randomized controlled trial

Wedged insoles are believed to be of clinical benefit to individuals with knee osteoarthritis by reducing the knee adduction moment (KAM) during gait. However, previous clinical trials have not specifically controlled for KAM reduction at baseline, thus it is unknown if reduced KAMs actually confer a clinical benefit. Forty-eight participants with medial knee osteoarthritis were randomly assigned to either a control group where no footwear intervention was given, or a wedged insole group where KAM reduction was confirmed at baseline. KAMs, Knee Injury and Osteoarthritis Outcome Score (KOOS) and Physical Activity Scale for the Elderly (PASE) scores were measured at baseline. KOOS and PASE surveys were re-administered at three months follow-up. The wedged insole group did not experience a statistically significant or clinically meaningful change in KOOS pain over three months (p=0.173). Furthermore, there was no association between change in KAM magnitude and change in KOOS pain over three months within the wedged insole group (R2=0.02, p=0.595). Improvement in KOOS pain for the wedged insole group was associated with worse baseline pain, and a change in PASE score over the three month study (R2=0.57, p=0.007). As an exploratory comparison, there was no significant difference in change in KOOS pain (p=0.49) between the insole and control group over three months. These results suggest that reduced KAMs do not appear to provide any clinical benefit compared to no intervention over a follow-up period of three months. ClinicalTrials.gov ID Number: NCT02067208.