The study compared thigh-shank and shank-foot coordination during gait before and after total knee arthroplasty (TKA) with controls (CTRL).

Twenty-seven patients (male=15/female=12; age=63.2±6.9 years) were evaluated one month prior to and twelve months after surgery, and compared to 27 controls (male=14/female=13; age=62.2±4.3). The participants were outfitted with a full-body marker set. Gait speed (normalized by leg length) was calculated. The time series of the thigh, shank, and foot orientation in relation to the laboratory coordinate system were extracted. The coordination between the thigh-shank and shank-foot in the sagittal plane were calculated using a vector coding technique. The coupling angles were categorized into four coordination patterns. The stance phase was divided into thirds: early, mid, and late stance. The frequency of each pattern and gait speed were compared using a one-way ANOVA with a post-hoc Bonferroni correction.

Walking speed and shank-foot coordination showed no differences between the groups. The thigh-shank showed differences. The pre-TKA group showed a more in-phase pattern compared to the CTRL group during early-stance. During mid-stance, the pre- and post-TKA presented a more in-phase pattern compared to the CTRL group. Regarding shank-foot coordination, the groups presented an in-phase and shank pattern, with more shank phase during mid-stance and more in-phase during late-stance.

The pre-TKA group showed greater differences than the post-TKA compared to the controls. The more in-phase pattern in the pre- and post-TKA groups could relate to a reduced capacity for the thigh that leads the movement. During mid-stance in normal gait, the knee is extending, where the thigh and shank movements are in opposite directions. The in-phase results in the TKA groups indicate knee stiffness during the stance phase, which may relate to a muscular deficit or a gait strategy to reduce joint stress.

This study examined pre-operative measures to predict post-operative biomechanical outcomes in total knee arthroplasty (TKA) patients.

Twenty-eight patients (female=12/male=16, age=63.6±6.9, BMI=29.9±7.4 kg/m2) with knee osteoarthritis scheduled to undergo TKA were included. All surgeries were performed by the same surgeon (GD) with a subvastus approach. Patients visited the gait lab within one-month prior to surgery and 12 months following surgery. At the gait lab, patients completed the knee injury and osteoarthritis outcome score (KOOS), a timed up and go (TUG), maximum knee flexion and extension strength evaluation, and a walking task. Variables of interest included the five KOOS sub-scores, TUG time, maximum knee flexion and extension strength normalized to body weight, walking speed, and peak knee biomechanics variables (flexion angle, abduction moment, power absorption). A Pearson's correlation was used to identify significantly correlated variables which were then inputted into a multiple regression.

No assumption violations for the multiple regression existed for any variables. Pre-operative knee flexion and extension strength, TUG time, and age were used in the multiple regression. The multiple regression model statistically significantly predicted peak knee abduction moment, post-operative walking speed, and post-operative knee flexion strength. All four variables added statistically significantly to the prediction p<.05.

Pre-operative KOOS values did not correlate with any biomechanical indicators of post-operative success. Age, pre-operative knee flexion and extension strength, and TUG times predicted peak knee abduction moment, which is associated with medial knee joint loading. These findings stress the importance of pre-surgery condition, as stronger individuals achieved better post-operative biomechanical outcomes. Additionally, younger patients had better outcomes, suggesting that surgeons should not delay surgery in younger patients. This delay in surgery may prevent patients from achieving optimal outcomes. Future studies should utilize a hierarchical multiple regression to identify which variables are most predictive.

Aims

Spinopelvic characteristics influence the hip’s biomechanical behaviour. However, to date there is little knowledge defining what ‘normal’ spinopelvic characteristics are. This study aims to determine how static spinopelvic characteristics change with age and ethnicity among asymptomatic, healthy individuals.

One in five patients remain unsatisfied due to ongoing pain and impaired mobility following total knee arthroplasty (TKA). It is important if surgeons can pre-operatively identify which patients may be at risk for poor outcomes after TKA. The purpose of this study was to determine if there is an association between pre-operative measures and post-operative outcomes in patients who underwent TKA.

This study included 28 patients (female = 12 / male = 16, age = 63.6 ± 6.9, BMI = 29.9 ± 7.4 kg/m2) with knee osteoarthritis who were scheduled to undergo TKA. All surgeries were performed by the same surgeon (GD), and a subvastus approach was performed for all patients. Patients visited the gait lab within one-month of surgery and 12 months following surgery. At the gait lab, patients completed the knee injury and osteoarthritis outcome score (KOOS), a timed up and go (TUG), and walking task. Variables of interest included the five KOOS sub-scores (symptoms, pain, activities of daily living, sport & recreation, and quality of life), completion time for the TUG, walking speed, and peak knee biomechanics variables (flexion angle, abduction moment, power absorption). A Pearson's product-moment correlation was run to assess the relationship between pre-operative measures and post-operative outcomes in the TKA patients.

Preliminary analyses showed the relationship to be linear with all variables normally distributed, as assessed by Shapiro-Wilk's test (p > .05), and there were no outliers. There were no statistically significant correlations between any of the pre-operative KOOS sub-scores and any of the post-operative biomechanical outcomes. Pre-operative TUG time had a statistically significant, moderate positive correlation with post-operative peak knee abduction moments [r(14) = .597, p < .001] and peak knee power absorption [r(14) = .498, p = .007], with pre-operative TUG time explaining 36% of the variability in peak knee abduction moment and 25% of the variability in peak knee power absorption. Pre-operative walking speed had a statistically significant, moderate negative correlation with post-operative peak knee abduction moments [r(14) = -.558, p = .002] and peak knee power absorption [r(14) = -.548, p = .003], with pre-operative walking speed explaining 31% of the variability in peak knee abduction moment and 30% of the variability in peak knee power absorption.

Patient reported outcome measures (PROMs), such as the KOOS, do indicate the TKA is generally successful at relieving pain and show an overall improvement. However, their pre-operative values do not correlate with any biomechanical indicators of post-operative success, such as peak knee abduction moment and knee power. Shorter pre-operative TUG times and faster pre-operative walking speeds were correlated with improved post-operative biomechanical outcomes. These are simple tasks surgeons can implement into their clinics to evaluate their patients. Future research should expand these findings to a larger sample size and to determine if other factors, such as surgical approach or implant design, improves patient outcomes.

Introduction and Objective

Gait variability is the amplitude of the fluctuations in the time series with respect to the mean of kinematic (e.g., joint angles) or kinetic (e.g., joint moments) measurements. Although gait variability increases with normal ageing or pathological mechanisms, such as knee osteoarthritis (OA). The purpose was to determine if a patient who underwent a total knee arthroplasty (TKA) can reduce gait variability.

The literature indicates that femoroacetabular impingement (FAI) patients do not return to the level of controls (CTRL) following surgery. The purpose of this study was to compare hip biomechanics during stair climbing tasks in FAI patients before and two years after undergoing corrective surgery against healthy controls (CTRL).

A total of 27 participants were included in this study. All participants underwent CT imaging at the local hospital, followed by three-dimensional motion analysis done at the human motion biomechanics laboratory at the local university. Participants who presented a cam deformity >50.5° in the oblique-axial or >60° in the radial planes, respectively, and who had a positive impingement test were placed in the FAI group (n=11, age=34.1±7.4 years, BMI=25.4±2.7 kg/m2). The remaining participants had no cam deformity and negative impingement test and were placed in the CTRL group (n=16, age=33.2±6.4 years, BMI=26.3±3.2 kg/m2). The CTRL group completed the biomechanics protocol once, whereas the FAI group completed the protocol twice, once prior to undergoing corrective surgery for the cam FAI, and the second time at approximately two years following surgery.

At the human motion biomechanics laboratory, participants were outfitted with 45 retroreflective markers placed according to the UOMAM marker set. Participants completed five trials of stairs task on a three step instrumented stair case to measure ground reaction forces while 10 Vicon MX-13 cameras recorded the marker trajectories. Data was processed using Nexus software and divided into stair ascent and stair descent tasks. The trials were imported into custom written MatLab software to extract peak pelvis and hip kinematics and hip kinetic variables. Non-parametric Kruskal-Wallis tests were used to determine significant (p < 0.05) differences between the groups.

No significant differences occurred during the stair descent task between any of the groups. During the stair ascent task, the CTRL group had significantly greater peak hip flexion angle (Pre-Op=58±7.1°, Post-Op=58.1±6.6°, CTRL=64.1±5.1°) and sagittal hip range of motion (ROM) (Pre-Op=56.7±6.7°, Post-Op=56.3±5.5°, CTRL=61.7±4.2°) than both the pre- and post-operative groups. Pre-operatively, the FAI group had significantly less peak hip adduction angle (Pre-Op=2±4.5°, Post-Op=3.4±4.4°, CTRL=5.5±3.7°) and hip frontal ROM (Pre-Op=9.9±3.4°, Post-Op=11.9±5.4°, CTRL=13.4±2.5°) compared to the CTRL group. No significant differences occurred in the kinetic variables.

Our findings are in line with the Rylander and colleagues (2013) who also found that hip sagittal ROM did not improve following corrective surgery. Their study included a mix of cam and pincer-type FAI, and had a mean follow-up of approximately one year. Our cohort included only cam FAI and they had a mean follow-up of approximately two years, indicating with the extra year, the patients still did not show sagittal hip kinematics improvement. In the frontal plane, there was no significant difference between the post-op and the CTRL, indicating that the postoperative FAI reached the level of the CTRLs. This is in line with recent work that indicates a more medialized hip contact force vector following surgery, suggesting better hip stabilization.

Many patients who undergo a total knee arthroplasty (TKA) wish to return to a more active lifestyle. The implant must be able to restore adequate muscle strength and function. However, this may not be a reality for some patients as quadriceps and hamstrings muscle activity may remain impaired following surgery.

The purpose of this study was to compare muscle activity between patients implanted with a medial pivot (MP) or posterior stabilized (PS) implant and controls (CTRL) during ramp walking tasks.

Fifteen patients were assigned to either a MP (n=9) or PS (n=6) TKA operated by the same surgeon. Nine months following surgery, the 15 patients along with nine CTRL patients completed motion and EMG analysis during level, ramp ascent & descent walking tasks.

Wireless EMG electrodes were placed on six muscles: vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), semimembranosus (SM) muscles, gastrocnemius medial head (GM), and gastrocnemius lateral head (GL). Participants completed three trials of each condition.

EMG data were processed for an entire gait cycle of the operated limb in the TKA groups, and for the dominant limb in the CTRL group. The maximum muscle activity achieved with each muscle during the level trial was used to normalize the ramp trials. The onset and offset of each muscle was determined using the approximated generalized likelihood ratio.

Peak muscle activity (PeakLE), total muscle activity (iEMG), and muscle onsets/offsets were determined for each muscle for the ramp ascent and descent trials. Non-parametric Kruskal Wallace tests were used to test for statistical significance between groups with α=0.05.

During the ramp up task, both MP and PS groups had significantly greater PeakLE and iEMG for the hamstring muscles compared to the CTRL, whereas the PS group had significantly greater PeakLE compared with the MP group for the SM muscle.

During the ramp down task, both MP and PS groups had significantly greater PeakLE and iEMG for the SM and GL muscles compared to the CTRL. The PS group also had significantly greater iEMG for the BF and VM muscles compared to the CTRL. The MP group had a significantly earlier offset for the SM muscle compared to the CTRL.

Stability in a cruciate removing TKA is partially controlled by the prosthetic design. During the ramp up task, the TKA groups compensated the tibial anterior translation by activating their hamstrings more and for a longer duration. The MP group required less hamstrings activation than the PS group.

During the ramp down task, TKA patients stiffened their knee in order to stabilize the joint. The quadriceps, hamstrings and GL muscle were activated more and for a longer duration than the CTRL group to protect the tibial posterior translation. The PS group required greater BF and VM iEMG than the MP group.

Even if surgery reduced pain, differences in muscle activity exist between TKA patients and healthy controls. The prosthetic design provides some stability to the knee, and the MP implant required less muscle activation than the PS implant to stabilize the knee joint.

Cam-type femoroacetabular impingement (FAI) is a common cause for athletic hip injury and early hip osteoarthritis. Although corrective cam FAI surgery can improve patient reported outcome measures (PROMs), it is not clear how surgery affects muscle forces and hip joint loading. Surgery for FAI may redistribute muscle forces and contact forces at the hip joint during routine activities. The purpose of this study was to examine the muscle contributions and hip contact forces during gait in patients prior and after two years of undergoing surgery for cam FAI. Kinematics and kinetics were recorded in 11 patients with symptomatic cam FAI as they completed a gait task. Muscle and hip contact forces during the stance phase were estimated using musculoskeletal modelling and static optimization in OpenSim. All patients reported improvements in PROMs. Post-operatively, patients showed reduced forces in the long head of the biceps femoris at ipsilateral foot-strike and in the rectus femoris at the contralateral foot-strike. The reduced muscle forces decreased sagittal hip moment but did not change hip contact forces. This was the first study to evaluate hip muscle and contact forces in FAI patients post-operatively. Although hip contact forces are not altered following surgery, muscle forces are decreased even after two years. These findings can provide guidance in optimizing recovery protocols after FAI surgery to improve hip flexor and extensor muscle forces.

Introduction

Patients undergoing a total knee arthroplasty (TKA) are now living longer and partaking in more active lifestyles. They expect a high level of post-operative function and long term durability of their implant.

Using electromyography (EMG) analysis helps further explain biomechanical findings by giving insight as to what is occurring at the level of the muscles. Normal biomechanics are not restored post-TKA as patients have reduced knee flexion and weakened quadriceps muscles compared to their healthy peers.

Dual mobility (DM) bearing implants reduce the incidence of dislocation following total hip arthroplasty (THA) and as such they are used for the treatment of hip instability in both primary and revision cases. The aim of this study was to compare lower limb muscle activity of patients who underwent a total hip arthroplasty (THA) with a dual mobility (DM) or a common cup (CC) bearing compared to healthy controls (CON) during a sit to stand task.

A total of 21 patients (12 DM, 9 CC) and 12 CON were recruited from the local Hospital. The patients who volunteered for the study were randomly assigned to either a DM or a CC cementless THA after receiving informed consent. All surgeries were performed by the same surgeon using the direct anterior approach. Participants underwent electromyography (EMG) and motion analysis while completing a sit-to-stand task. Portable wireless surface EMG probes were placed on the vastus lateralis, rectus femoris, biceps femoris, semitendinosus (ST), gluteus medius and tensor fasciae latae muscles of the affected limb in the surgical groups and the dominant limb in the CON group. Motion capture was used to record lower limb kinematics and kinetics. Muscle strength was recorded using a hand-held dynamometer during maximal voluntary isometric contraction (MVIC) testing. Peak linear envelope (peakLE) and total muscle activity (iEMG) were extrapolated and normalized to the MVIC and time cycle for the sit to stand task. Using iEMG, quadriceps-hamstrings muscle co-activation index was calculated for the task. Nonparametric Kruskal Wallace ANOVA tests and Wilcoxon rank sum tests were used to identify where significant (p < 0.05) differences occurred.

The DM group had greater iEMG of the ST muscle compared to the CC (p=0.045) and the CON (p=0.015) groups. The CC group had lower iEMG for hamstring muscles compared to the DM (p=0.041) group. The DM group showed lower quadriceps-hamstrings co-activation index compared to the CON group and it approached significance (p=0.054). The CC group had greater anterior pelvis tilt compared to both DM (p=0.043) and the CON (p=0.047) groups. The DM also had larger knee varus angles and less knee internal rotation compared to both groups, however this never reached significance. No significant differences in muscle strength existed between the groups.

Higher ST muscle activity in the DM group is explained by the reduction in internal rotation at the knee joint as the ST muscle was more active to resist the varus forces during the sit-to-stand task. Reduced quadriceps activity in the CC group is explained by increased pelvic anterior tilt as this would shorten the moment arm and muscle length in the quadriceps, ultimately reducing quadriceps muscle activity. The reduced co-activation between quadriceps and hamstrings activity in the DM group compared to the CC and CON groups is related to better hip function and stability. Combining lower co-activation and larger range of motion for the DM group without impingement, this implant seems to offer better prevention against THA subluxation and less wear of the implant.

The purpose of this study was to compare lower limb joint mechanics in patients who underwent a total knee arthroplasty (TKA) with either a posterior stabilised (PS) or with a medial pivot (MP) implant to healthy controls (CTRL) during stair ascent and descent tasks.

Six PS (age: 67.2±1.5 years, BMI: 31.0±3.2 kg/m2) and 11 MP (age: 62.3±6.0 years, BMI: 29.7±3.9 kg/m2) TKA patients matched to 10 healthy CTRL participants (age: 65.6±5.5 years, BMI: 27.2±5.0 kg/m2) were included in the study. TKA patients went through 3D motion analysis after unilateral TKA with either a MP (11.7±3.4 months post-surgery) or PS (10.1±3.4 months post-surgery) implant performed using either a subvastus or medial parapatellar approach. Kinematic and kinetic data was collected using a 10-camera Vicon and two portable Kistler force plates placed on the first and second stair of a three-step staircase. Nonparametric Kruskal Wallace ANOVA tests were used and Wilcoxon rank sum tests were used to identify where significant (p < 0.05) differences occurred.

When comparing both stair tasks, stair ascent showed a larger number of significant differences in kinematic and kinetic variables than stair descent. Peak knee extension was significantly (p < 0.05) greater in both TKA groups compared to the CTRL during stair descent, whereas only the PS group had significantly (p = 0.02) greater knee extension angle than the CTRL during stair ascent. The PS group had a significantly (p = 0.01) lower peak knee extension moment than the CTRL group during both tasks and compared to the MP group during stairs ascent. During stair ascent, the MP group had significantly (p = 0.02) larger peak hip extension moments than both PS and CTRL group.

Greater knee extension angles in TKA groups at foot strike during stair tasks support the notion that TKA groups exhibit stiff knee during stance to reduce or avoid shear displacement on the operated knee. This could also result from many years of muscle adaptation waiting to receive a knee replacement. Reduced peak knee extension moment in the PS group during stairs tasks showed a quadriceps deficiency that could increase the risk of revision or of other joint replacement on the contralateral side or ipsilateral hip. MP group reproduced similar joint loading patterns as the CTRLs which may reduce their risk of revision. In conclusion, TKA patients continue to exhibit discrepancies from healthy knee mechanics during stair ascent and descent. Further research examining muscle function especially during stair ascent is warranted.

The purpose of this study was to compare lower limb muscle activity in patients who underwent a total knee arthroplasty (TKA) with a medial pivot (MP) implant to healthy controls (CTRL) during a stair ascent task.

Seven MP (age: 61.4±6.5 years, BMI: 30.0±4.7 kg/m2, 12.4±3.8 months post-surgery) patients who underwent a TKA performed using either a subvastus or medial parapatellar approach were age- and BMI-matched to seven healthy CTRL participants (age: 62.4±4.2 years, BMI: 26.3±2.7 kg/m2) for comparison in this study. Participants underwent electromyography (EMG) analysis while completing a three-step stairs ascent task. Portable wireless surface EMG probes were placed on the vastus lateralis (VL), rectus femoris (RF), vastus medialis (VM), biceps femoris (BF) and semimembranous (SM) muscles of both lower limbs. Peak linear envelope (peakLE) and total muscle activity (iEMG) were extrapolated and normalised to a maximal voluntary contraction. Nonparametric Kruskal Wallace ANOVA tests were used and Wilcoxon rank sum tests were used to identify where significant (p < 0.05) differences occurred.

The operated limb had significantly lower iEMG in the VAL, RF and BF muscles, and significantly lower peakLE in the SM muscle compared to the non-operated limb. The operated-limb of the MP group had significantly lower iEMG in the VAL and BF muscles, and significantly lower peakLE in the VAL, RF and SM muscles compared to the CTRL group. The non-operated limb in the MP group had significantly larger peakLE and iEMG in the RF muscle compared to the CTRL group.

Differences in muscle activity between the operated and non-operated limbs in TKA patients with a MP implant demonstrates a compensatory strategy to reduce loading on the operated limb by relying on the non-operated limb. This same strategy has been reported in other studies investigating other functional tasks. This reliance on the non-operated limb resulted by having greater peakLE and iEMG in the RF muscle compared to the healthy CTRLs. These differences between limbs could also result from many years of muscle adaptation waiting to receive a knee replacement. In conclusion, TKA patients exhibit discrepancies in muscle activity compared to healthy knees and differences between operated and non-operated limbs. Post-surgery rehabilitation should rely on unilateral strength exercises of the quadriceps and hamstrings muscles to reduce discrepancies to allow for a more balanced muscle activity between limbs.