Introduction: Gait initiation is a sequence of stereotypical postural shifts culminating in a forward step. Muscular and gravitational forces interact leading to appropriate dynamic conditions that allow progression. This requires a complicated system of neural and muscular control. Derangement of ground reaction forces during gait initiation may be a more specific indicator of neuromuscular disease than steady state gait. Little work has been done on gait initiation in children and there is no published data on gait initiation with cerebral palsy. The aim of this study was to examine the ground reaction forces and centre of pressure in normal children during gait initiation, to compare these to similar values in hemiplegic children and to try to identify differences between the two which may be diagnostic for hemiplegia. Patients and methods: Five normal and five hemiplegic children were studied. Kinematic and dynamic data were collected using a CodaTM motion analysis system and KestlerTM force plate. All subjects stood with one foot on and one foot off the force plate and walked off upon hearing an audible cue. Tests were repeated measuring right and left, normal and hemiplegic legs as both stance and swing legs. Ground reaction forces in the X,Y and Z axes, centre of pressure and kinematic data were collected and studied. Results: 1) Normal children. In the vertical direction for the stance leg there is an initial fall in GRF, followed by a bimodal peak in GRF. In the fore-aft direction the GRF is initially directed backwards and subsequently has a bimodal forward force. Medio-laterally the stance GRF tending to adduct falls initially and subsequently rises with a bimodal peak. The forces in the swing leg reciprocate these forces. 2) Hemiplegic children. The overall pattern seen when the normal leg is the stance leg are similar to those in normal children with certain specific variations in force development and magnitude. When the hemiplegic leg is the stance leg the overall patterns are again similar but considerably less smooth with characteristic changes indicative of neuro-muscular disturbance. The initial “adjusting” forces tend to be larger indicating the greater force required for control. Discussion: The pattern and relative magnitude of forces measured for normal children are identical to those previously reported for adults. This validates our study design and indicates that central programming for gait initiation develops early in life. It is therefore an early developmental skill and may be used as a diagnostic test in childhood. Significant variations are seen in cerebral palsy. Knowledge of these specific changes may allow earlier and more accurate diagnosis of cerebral palsy in children under investigation for movement disorders. Normal GRF patterns during gait initiations may provide early reassurance for parents of children suspected of having cerebral palsy

Force profiles across the foot yield information on abnormal kinematics and may be used to indicate pathological changes in the lower limb. However, current technology is limited to tethered systems using wired sensors. This paper outlines a wireless prototype that allows force profile measurement and through an in-shoe monitoring device utilizing custom high-accuracy sensors. Direct measurement of the ground reaction force using a force plate is common practice for use in kinematic studies and is used as an input for mathematical models to predict forces across joints of interest during various activities. Force plates are reasonably accurate but are bulky and only allow one net force measurement at a single location and are not portable. Thus natural patient motion may be modified, intentionally or unintentionally, in order for heelstrike to occur on the force plate. In addition to force magnitude, it is useful to record force location to correlate with kinematics; abnormal kinematics will cause weight-bearing forces to shift across the foot. Current in-shoe pressure measurement devices on the market are plagued by errors up to 30% and require a cumbersome cable out of the shoe to read sensor data. By eliminating all wires, our device enables in-shoe monitoring in a research or clinical environment. The device uses microelectromechanical system (MEMS) capacitive pressure sensors fabricated in a flexible array that attaches to a shoe insole or orthotic. The sensors are concentrated at the heel and forefoot in the prototype design and they exhibit a highly linear response to loading, eliminating the need for constant recalibration. Electronics embedded in the shoe read the entire array of 256 sensors at a rate of 60 Hz. The data is transmitted via Bluetooth at 2.4 GHz to the receiving computer for visualization and analysis. The paper assesses current technology in in-shoe sensing, outlines the device design, and reports initial stages of testing. The prototype developed in this study shows promise for wireless monitoring of ground reaction forces for biomechanics analysis without restricting activity or impeding natural motion

Aims

This study aimed to analyze kinematics and kinetics of the tibiofemoral joint in healthy subjects with valgus, neutral, and varus limb alignment throughout multiple gait activities using dynamic videofluoroscopy.

Fifth metatarsal fractures in sport are known to be associated with acceleration and cross cutting movements when running. It is also established that playing surface has an impact on the ground reaction forces through the foot, increasing the strain through the fifth metatarsal. But what impact does boot design have on these forces? Current thought is that boots that utilise a blade stud design resist sideways slipping of the planted foot more than boots with a rounded stud. This study aims to compare ground reaction forces through the fifth metatarsal in 2 two different designs of rugby boot to assess what impact stud design might have. The forces across the foot were measured using Tekscan in-shoe pressure plates in 24 rugby players. Each player was asked to complete an agility course to measure acceleration, cutting and cross-cutting in the two different designs of rugby boot, reproducing true playing conditions. The boots used were the Canterbury Phoenix Club 8 Stud boot and the Canterbury Speed Club Blade boot. The trial was conducted on an 4G artificial pitch at the Cardiff Arms Park rugby ground. Ethical approval was obtained from Bath University and a research grant was provided by British Orthopaedic Foot and Ankle Society. The blade boot had significantly higher contact pressures than the stud boot on the fifth metatarsal in the combined movements (17.909 ± 10.442 N/cm2 Blade Vs 16.888 ± 9.992 N/cm2 Boot; P < .0125; n= 864 steps in each boot group). The blade boot also produced higher pressure during cross-cutting (32.331 ± 13.568 N/cm2 Vs 27.651 ± 15.194 N/cm2 p < 0.007). Pressures were also higher in both acceleration and cutting, although not significantly so. These results will guide clinicians advising athletes in shoe design, especially those predisposed to or rehabilitating from a fifth metatarsal fracture

Abstract. OBJECTIVES. Application of deep learning approaches to marker trajectories and ground reaction forces (mocap data), is often hampered by small datasets. Enlarging dataset size is possible using some simple numerical approaches, although these may not be suited to preserving the physiological relevance of mocap data. We propose augmenting mocap data using a deep learning architecture called “generative adversarial networks” (GANs). We demonstrate appropriate use of GANs can capture variations of walking patterns due to subject- and task-specific conditions (mass, leg length, age, gender and walking speed), which significantly affect walking kinematics and kinetics, resulting in augmented datasets amenable to deep learning analysis approaches. METHODS. A publicly available (. https://www.nature.com/articles/s41597-019-0124-4. ) gait dataset (733 trials, 21 women and 25 men, 37.2 ± 13.0 years, 1.74 ± 0.09 m, 72.0 ± 11.4 kg, walking speeds ranging from 0.18 m/s to 2.04 m/s) was used as the experimental dataset. The GAN comprised three neural networks: an encoder, a decoder, and a discriminator. The encoder compressed experimental data into a fixed-length vector, while the decoder transformed the encoder's output vector and a condition vector (containing information about the subject and trial) into mocap data. The discriminator distinguished between the encoded experimental data from randomly sampled vectors of the same size. By training these networks jointly using the experimental dataset, the generator (decoder) could generate synthetic data respecting specified conditions from randomly sampled vectors. Synthetic mocap data and lower limb joint angles were generated and compared to the experimental data, by identifying the statistically significant differences across the gait cycle for a randomly selected subset of the experimental data from 5 female subjects (73 trials, aged 26–40, weighing 57–74 kg, with leg lengths between 868–931 mm, and walking speeds ranging from 0.81–1.68 m/s). By conducting these comparisons for this subset, we aimed to assess the synthetic data generated using multiple conditions. RESULTS. We visually inspected the synthetic trials to ensure that they appeared realistic. The statistical comparison revealed that, on average, only 2.5% of the gait cycle showed significantly differences in the joint angles of the two data groups. Additionally, the synthetic ground reaction forces deviated from the experimental data distribution for an average of 2.9% of the gait cycle. CONCLUSIONS. We introduced a novel approach for generating synthetic mocap data of human walking based on the conditions that influence walking patterns. The synthetic data closely followed the trends observed in the experimental data, also in the literature, suggesting that our approach can augment mocap datasets considering multiple conditions, an approach unfeasible in previous work. Creation of large, augmented datasets allows the application of other deep learning approaches, with the potential to generate realistic mocap data from limited and non-lab-based data. Our method could also enhance data sharing since synthetic data does not raise ethical concerns. You can generate and download virtual gait data using our GAN approach from . https://thisgaitdoesnotexist.streamlit.app/. . Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. Gait laboratory measurement of whole-body kinematics and ground reaction forces during a wide range of activities is frequently performed in joint replacement patient diagnosis, monitoring, and rehabilitation programs. These data are commonly processed in musculoskeletal modeling platforms such as OpenSim and Anybody to estimate muscle and joint reaction forces during activity. However, the processing required to obtain musculoskeletal estimates can be time consuming, requires significant expertise, and thus seriously limits the patient populations studied. Accordingly, the purpose of this study was to evaluate the potential of deep learning methods for estimating muscle and joint reaction forces over time given kinematic data, height, weight, and ground reaction forces for total knee replacement (TKR) patients performing activities of daily living (ADLs). Methods. 70 TKR patients were fitted with 32 reflective markers used to define anatomical landmarks for 3D motion capture. Patients were instructed to perform a range of tasks including gait, step-down and sit-to-stand. Gait was performed at a self-selected pace, step down from an 8” step height, and sit-to-stand using a chair height of 17”. Tasks were performed over a force platform while force data was collected at 2000 Hz and a 14 camera motion capture system collected at 100 Hz. The resulting data was processed in OpenSim to estimate joint reaction and muscle forces in the hip and knee using static optimization. The full set of data consisted of 135 instances from 70 patients with 63 sit-to-stands, 15 right-sided step downs, 14 left-sided step downs, and 43 gait sequences. Two classes of neural networks (NNs), a recurrent neural network (RNN) and temporal convolutional neural network (TCN), were trained to predict activity classification from joint angle, ground reaction force, and anthropometrics. The NNs were trained to predict muscle and joint reaction forces over time from the same input metrics. The 135 instances were split into 100 instances for training, 15 for validation, and 20 for testing. Results. The RNN and TCN yielded classification accuracies of 90% and 100% on the test set. Correlation coefficients between ground truth and predictions from the test set ranged from 0.81–0.95 for the RNN, depending on the activity. Predictions from both NNs were qualitatively assessed. Both NNs were able to effectively learn relationships between the input and output variables. Discussion. The objective of the study was to develop and evaluate deep learning methods for predicting patient mechanics from standard gait lab data. The resulting models classified activities with excellent performance, and showed promise for predicting exact values for loading metrics for a range of different activities. These results indicate potential for real-time prediction of musculoskeletal metrics with application in patient diagnostics and rehabilitation. For any figures or tables, please contact authors directly

Background. Previous in vivo fluoroscopic studies have documented that subjects having a PS TKA experience a more posterior condylar contact position at full extension, a high incidence of reverse axial rotation and mid flexion instability. More recently, a PS TKA was designed with a Gradually Reducing Radius (Gradius) curved condylar geometry to offer patients greater mid flexion stability while reducing the incidence of reverse axial rotation and maintaining posterior condylar rollback. Therefore, the objective of this study was to assess the in vivo kinematics for subjects implanted with a Gradius curved condylar geometry to determine if these subjects experience an advantage over previously designed TKA. Methods. In vivo kinematics for 30 clinically successful patients all having a Gradius designed PS fixed bearing TKA with a symmetric tibia were assessed using mobile fluoroscopy. All of the subjects were scored to be clinically successful. In vivo kinematics were determined using a 3D-2D registration during three weight-bearing activities: deep-knee-bend (DKB), gait, and ramp down (RD). Flexion measurements were recorded using a digital goniometer while ground reaction forces were collected using a force plate as well. The subjects then assessed for range of motion, condyle translation and axial rotation and ground reaction forces. Results. During a DKB, subjects implanted a Gradius designed, PS fixed bearing TKA design exhibited an average of 3.35 mm of posterior femoral rollback of the lateral condyle and 2.73 mm of the medial condyle with an average axial rotation of 4.90° in the first 90° of flexion. The average max flexion was 111.4°. From full extension to maximum flexion, the average axial rotation was 4.73°, while the subjects experienced 5.34 and 1.97 mm on the lateral and medial condyle rollback, respectively. During mid flexion from 30 to 60 degrees of flexion, the subjects experienced 1.34° of axial rotation, −1.13 and −0.11 mm of lateral and medial condyle motion. Conclusions. Subjects in this study did experience good weight-bearing flexion and magnitudes of axial rotation and posterior femoral rollback similar to previous PS TKA designs. During mid flexion, subjects in this study did experience less mid flexion paradoxical sliding than other PS TKA, leading to greater mid flexion stability for the patients

Reports of improved functional outcome of Metal on Metal Hip Resurfacing Arthroplasty (mHRA) to Total Hip Replacement needs to be balanced with concerns of metal ion release. By removing cobalt-chrome, cHRA reduces these risks. To the author's knowledge, there is no data available on functional outcomes of cHRA, therefore the aim of the study was to compare the function between cHRA patients and mHRA patients. 24 patients received a unilateral cHRA (H1, Embody) and was compared to 24 age and gender matched patients with a unilateral mHRA (BHR, Smith and Nephew). All patients completed the Oxford Hip Score (OHS)[T2] and underwent gait analysis on an instrumented treadmill before and at a mean of 74wks (+/− 10) for mHRA and 53wks (+/− 2) for cHRA post op. Walking trials started at 4km/h and increased in 0.5km/h increments until a top walking speed (TWS) was achieved. Vertical ground reaction forces (GRF) were recorded along with the symmetry index (SI). Spatiotemporal measures of gait were also recorded. Vertical GRF were captured for the entire normalised stance phase using statistical parametric mapping (SPM; CI = 95%). The gain in OHS was similar: H1 (25-46), BHR(27-47). TWS increased by 19% with H1 (6.02 – 8.0km/hr), and 20% with BHR (6.02 – 7.37km/hr). SPM of the entire gait cycle illustrated the restoration of symmetry in both groups with no difference in GRF across the stance phase between groups at 5km/hr pre-op and post-op. At faster speeds (6.5km/hr), H1 patients had a mid-support GRF slightly closer to normal compared to BHR. Both groups increased step length similar from pre to post op (H1:0.76 – 0.85cm, BHR:0.77-0.86cm). In this study, subjective and objective functional outcome measures suggest that short term functional outcomes of ceramic resurfacing is not inferior to metal resurfacing

It is known that the gait dynamics of elderly substantially differs from that of young people. However, it has not been well studied how this age-related gait dynamics affects the knee biomechanics, e.g., cartilage mechanical response. In this study, we investigated how aging affects knee biomechanics in a female population using subject-specific computational models. Two female subjects (ages of 23 and 69) with no musculoskeletal disorders were recruited. Korea National Institute for Bioethics Policy Review Board approved the study. Participants walked at a self-selected speed (SWS), 110% of SWS, and 120% of SWS on 10 m flat ground. Three-dimensional marker trajectories and ground reaction forces (Motion Analysis, USA), and lower limbs’ muscle activities were measured (EMG, Noraxon USA). Knee cartilage and menisci geometries were obtained from subjects’ magnetic resonance images (3T, GE Health Care). An EMG-assisted musculoskeletal finite element modeling workflow was used to estimate knee cartilage tissue mechanics in walking trials. Knee cartilage and menisci were modeled using a transversely isotropic poroviscoelastic material model. Walking speed in SWS, 110%, and 120% of SWS were 1.38 m/s, 1.51 m/s, and 1.65 m/s for the young, and 1.21 m/s, 1.34 m/s and 1.46 m/s for the elderly, respectively. The maximum tensile stress in the elderly tibial cartilage was ~25%, ~33%, and ~32% lower than the young at SWS, 110%, and 120% of SWS, respectively. These preliminary results suggest that the cartilage in the elderly may not have enough stimulation even at 20% increases in walking speed, which may be one reason for tissue degeneration. To enhance these findings, further study with more subjects and different genders will investigate how age-related gait dynamics affects knee biomechanics. Acknowledgments: Australian NHMRC Ideas Grant (APP2001734), KITECH (JE220006)

Altered mechanical loading is a widely suggested, but poorly understood potential cause of cartilage degeneration in osteoarthritis. In rodents, osteoarthritis is induced following destabilization of the medial meniscus (DMM). This study estimates knee kinematics and contact forces in rats with DMM to gain better insight into the specific mechanisms underlying disease development in this widely-used model. Unilateral knee surgery was performed in adult male Sprague-Dawley rats (n=5 with DMM, n=5 with sham surgery). Radio-opaque beads were implanted on their femur and tibia. 8 weeks following knee surgery, rat gait was recorded using the 3D²YMOX setup (Sanctorum et al. 2019, simultaneous acquisition of biplanar XRay videos and ground reaction forces). 10 trials (1 per rat) were calibrated and processed in XMALab (Knörlein et al. 2016). Hindlimb bony landmarks were labeled on the XRay videos using transfer learning (Deeplabcut, Mathis et al. 2019; Laurence-Chasen et al. 2020). A generic OpenSim musculoskeletal model of the rat hindlimb (Johnson et al. 2008) was adapted to include a 3-degree-of-freedom knee. Inverse kinematics, inverse dynamics, static optimization of muscle forces, and joint reaction analysis were performed. In rats with DMM, knee adduction was lower compared to sham surgery. Ground reaction forces were less variable with DMM, resulting in less variability in joint external moments. The mediolateral ground reaction force was lower, resulting in lower hip adduction moment, thus less force was produced by the rectus femoris. Rats with DMM tended to break rather than propel, resulting in lower hip flexion moment, thus less force was produced by the semimembranosus. These results are consistent with lower knee contact forces in the anteroposterior and axial directions. These preliminary data indicate no overloading of the knee joint in rats with DMM, compared with sham surgery. We are currently expanding our workflow to finite element analysis, to examine mechanical cues in the cartilage of these rats (Fig1G)

Ontogeny of long bone cross-sectional geometry has lasting effects on adult bone structure. Growth and development of bone is influenced by biological and mechanical factors but the importance of these factors is poorly understood. A study of prenatal, neonatal and infant development in a bone with simple loading patterns, may improve our understanding. Five vertebral columns aged between 6 months prenatal to 2.5 years postnatal, were analysed to quantify the changes in trabecular architecture before and after birth. Several measures were collected including trabecular: thickness, bone volume fraction, connectivity density, number, structure model index and anisotropy. The findings show that in the first year after birth there is a substantial loss of bone volume via decreasing trabecular thickness and number, which tends to increase after 1.2 years. This sequential pattern of development may be a functional response to the initial requirement for calcium mineral homeostasis before birth, followed by the need for trabecular architecture to adapt to mechanical loading after birth. Calcium is essential for growing neonates and therefore osteoclastic resorbtion is up regulated by increasing parathyroid hormone levels. This may account for the loss of bone between 0–1 year. At one year infants begin to walk bipedally, thus weight bearing and ground reaction forces increase. The stable bone volume and increase in organisation of trabecular architecture after one year may reflect increasing weight bearing and ground reaction forces. These findings suggest that nutritional requirements after birth may have a stronger influence on vertebral trabeculae architecture than learning to walk

Purpose: Gait analysis has become an innovative approach to assess the biomechanical adaptations due to an ACL injury. However, interpreting the large amount of data collected often requires an expert. Therefore, there is a need to develop an automatic method capable to distinguish kinetic pattern of an ACL deficient patients from an asymptomatic population. Method: 26 ACL deficient patients and 30 asymptomatic participants took part in a treadmill gait analysis. 3D ground reaction forces (vertical, medio-lateral and anterior-posterior) were collected using the ADAL 3D treadmill. Features were extracted from the 3D ground reaction forces as a function of time and then classified by the nearest neighbour rule using a wavelet decomposition method. The classification method was tested on our data base of 56 participants. Results: The proposed classification method obtained an accuracy of 90%. The classification accuracy per class was higher for the ACL deficient group allowing classifying correctly 25 out of 26 ACL deficient patient. 25 out of the 30 asymptomatic participants were properly classified. Conclusion: This study shows that an automatic objective computer method could be used in a clinical setting to help diagnose an anterior cruciate ligament injury during a gait analysis evaluation. Future studies should apply this method on a larger database including data from patients with other musculoskeletal pathologies to help diagnose other injuries

In this cross-over study, we evaluated two types of knee brace commonly used in the conservative treatment of osteoarthritis of the medial compartment. Twelve patients confirmed radiologically as having unilateral osteoarthritis of the medial compartment (Larsen grade 2 to grade 4) were studied. Treatment with a simple hinged brace was compared with that using a valgus corrective brace. Knee kinematics, ground reaction forces, pain and function were assessed during walking and the Hospital for Special Surgery scores were also determined. Significant improvements in pain, function, and loading and propulsive forces were seen with the valgus brace. Treatment with a simple brace showed only significant improvements in loading forces. Our findings suggest that although both braces improved confidence and function during gait, the valgus brace showed greater benefit

Abstract. Objectives. This abstract provides an update on the Open Ankle Models being developed at the University of Bath. The goal of this project is to create three fully open-source finite element (FE) ankle models, including bones, ligaments, and cartilages, appropriate musculoskeletal loading and boundary conditions, and heterogeneous material property distribution for a standardised representation of ankle biomechanics and pre-clinical ankle joint analysis. Methods. A computed tomography (CT) scan data (pixel size of 0.815 mm, and slice thickness of 1 mm) was used to develop the 3D geometry of the bones (tibia, talus, calcaneus, fibula, and navicular). Each bone was given the properties of a heterogeneous elastic material based on the CT greyscale. The density values for each bone element were calculated using a linear empirical relation, ρ= 0.0405 + (0.000918) HU and then power law equations were utilised to get the Young's Modulus value for each bone element [1]. At the bone junction, a thickness of cartilage ranging from 0.5–1 mm, and was modelled as a linear material (E=10 MPa, ν=0.4 [2]). All ligament insertions and positions were represented by four parallel spring elements, and the ligament stiffness and material attributes were applied in accordance with the published literature [2]. The ankle model was subjected to static loading (balance standing position). Four noded tetrahedral elements were used for the discretization of bones and cartilages. All degrees of freedom were restricted at the proximal ends of the tibia and fibula. The ground reaction forces were applied at the underneath of the calcaneus bone. The interaction between the cartilages and bones was modelled using an augmented contact algorithm with a sliding elastic contact between each cartilage. A tied elastic contact was used between the cartilages and the bone. FEbio 2.1.0 (University of Utah, USA) was used to construct the open-source ankle model. Results. When the double-legged stance phase loading condition was taken into consideration, stress at the antero-medial tibial wall (ranged from 1 to 7 MPa) was found to be similar to the prior work [2], indicating bulk of the load transfer was through this region. The maximum principal strain was predicted at the different regions on bones around the ankle joint. The proximal surface of the talus, and tibial distal surface were shown to have the highest maximum principal strains followed by antero-medial walls of the tibia bone, at the proximal location. Conclusions. The present open 3D FE model of the ankle will assist researchers in better understanding ankle biomechanics, precisely predicting load transfer, and examining the ankle to address unmet clinical needs for this joint. The results of the current investigation are realistic in terms of load transfer and stress-strain distribution across the ankle joint and well comparable to those reported in the literature [2]. However, sensitivity and ankle instability simulations will be performed in future work to investigate the model's reliability and robustness. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Background. High functional aspirations and an active ageing population equate to a growing number of patients awaiting hip arthroplasty demanding superior biomechanical function. The purpose of this study was to compare the biomechanics of top walking speed between two commonly used hip arthroplasty procedures to determine if a performance advantage existed. Methods. A retrospective comparative study was performed using sixty-seven subjects, twenty-two subjects in both hip resurfacing and total hip arthroplasty groups along with twenty-three healthy controls. All arthroplasty subjects were recruited based on high psychometric scoring and had been performed through a posterior approach, and had been discharged from follow-up. On an instrumented treadmill each subject was measured by a researcher blinded to which procedure that patient had undergone. After a six minute acclimatization period, the speed was increased incrementally until top walking performance had been attained. At all increments, ground reaction forces and temporospatial measurements were collected. Results. The two arthroplasty groups were well matched demographically, with no significant differences with regards to age, sex, height, BMI and pre-operative radiological severity. Treadmill temporospatial analysis demonstrated significant differences between the two groups. The hip resurfacing group were able to walk statistically faster (p=0.023) with an increased step length(p=0.041). The top walking speed mean of 2.06m/sec by the resurfacing almost matched the healthy controls. Assessing ground reaction forces and symmetry also demonstrated hip resurfacing was superior (Graph 1). [Graph 1: Mean Gait Biomechanics at Top Speed]. Conclusion. This study is the first to focus on high end performance following hip arthroplasty, encouraging patients to achieve as high a speed as they comfortably could. The total hip arthroplasty group walked nine percent faster than the previously published top speed of 1.73m/sec, however the resurfacings still walked ten percent faster, matching the normal controls for speed and step length

Aims. Bi-unicondylar arthroplasty (Bi-UKA) is a bone and anterior cruciate ligament (ACL)-preserving alternative to total knee arthroplasty (TKA) when the patellofemoral joint is preserved. The aim of this study is to investigate the clinical outcomes and biomechanics of Bi-UKA. Methods. Bi-UKA subjects (n = 22) were measured on an instrumented treadmill, using standard gait metrics, at top walking speeds. Age-, sex-, and BMI-matched healthy (n = 24) and primary TKA (n = 22) subjects formed control groups. TKA subjects with preoperative patellofemoral or tricompartmental arthritis or ACL dysfunction were excluded. The Oxford Knee Score (OKS) and EuroQol five-dimension questionnaire (EQ-5D) were compared. Bi-UKA, then TKA, were performed on eight fresh frozen cadaveric knees, to investigate knee extensor efficiency under controlled laboratory conditions, using a repeated measures study design. Results. Bi-UKA walked 20% faster than TKA (Bi-UKA mean top walking speed 6.7 km/h (SD 0.9),TKA 5.6 km/h (SD 0.7), p < 0.001), exhibiting nearer-normal vertical ground reaction forces in maximum weight acceptance and mid-stance, with longer step and stride lengths compared to TKA (p < 0.048). Bi-UKA subjects reported higher OKS (p = 0.004) and EQ-5D (p < 0.001). In vitro, Bi-UKA generated the same extensor moment as native knees at low flexion angles, while reduced extensor moment was measured following TKA (p < 0.003). Conversely, at higher flexion angles, the extensor moment of TKA was normal. Over the full range, the extensor mechanism was more efficient following Bi-UKA than TKA (p < 0.028). Conclusion. Bi-UKA had more normal gait characteristics and improved patient-reported outcomes, compared to matched TKA subjects. This can, in part, be explained by differences in extensor efficiency. Cite this article: Bone Joint Res 2021;10(11):723–733

Individuals with multi-compartment knee osteoarthritis (KOA) frequently experience challenges in activities of daily living (ADL) such as stair ambulation. The Levitation “Tri-Compartment Offloader” (TCO) knee brace was designed to reduce pain in individuals with multicompartment KOA. This brace uses novel spring technology to reduce tibiofemoral and patellofemoral forces via reduced quadriceps forces. Information on brace utility during stair ambulation is limited. This study evaluated the effect of the TCO during stair descent in patients with multicompartment KOA by assessing knee flexion moments (KFM), quadriceps activity and pain. Nine participants (6 male, age 61.4±8.1 yrs; BMI 30.4±4.0 kg/m2) were tested following informed consent. Participants had medial tibiofemoral and patellofemoral OA (Kellgren-Lawrence grades two to four) diagnosed by an orthopaedic surgeon. Joint kinetics and muscle activity were evaluated during stair descent to compare three bracing conditions: 1) without brace (OFF); 2) brace in low power (LOW); and 3) brace in high power (HIGH). The brace spring engages from 60° to 120° and 15° to 120° knee flexion in LOW and HIGH, respectively. Individual brace size and fit were adjusted by a trained researcher. Participants performed three trials of step-over-step stair descent for each bracing condition. Three-dimensional kinematics were acquired using an 8-camera motion capture system. Forty-one spherical reflective markers were attached to the skin (on each leg and pelvis segment) and 8 markers on the brace. Ground reaction forces and surface EMG from the vastus medialis (VM) and vastus lateralis (VL) were collected for the braced leg. Participants rated knee pain intensity performing the task following each bracing condition on a 10cm Visual Analog Scale ranging from “no pain” (0) to “worst imaginable pain” (100). Resultant brace and knee flexion angles and KFM were analysed during stair contact for the braced leg. The brace moment was determined using brace torque-angle curves and was subtracted from the calculated KFM. Resultant moments were normalized to bodyweight and height. Peak KFMs were calculated for the loading response (Peak1) and push-off (Peak2) phases of support. EMG signals were normalized and analysed during stair contact using wavelet analysis. Signal intensities were summed across wavelets and time to determine muscle power. Results were averaged across all 3 trials for each participant. Paired T-tests were used to determine differences between bracing conditions with a Bonferroni adjustment for multiple comparisons (α=0.025). Peak KFM was significantly lower compared to OFF with the brace worn in HIGH during the push-off phase (p Table 1: Average peak knee flexion moments, quadriceps muscle power and knee pain during stair descent in 3 brace conditions (n=9). Quadriceps activity, knee flexion moments and pain were significantly reduced with TCO brace wear during stair descent in KOA patients. These findings suggest that the TCO assists the quadriceps to reduce KFM and knee pain during stair descent. This is the first biomechanical evidence to support use of the TCO to reduce pain during an ADL that produces especially high knee forces and flexion moments. For any figures or tables, please contact the authors directly

Objective: To establish a relationship between the scoliotic curve and the centre of gravity during level walking in patients diagnosed with adolescent idiopathic scoliosis. Background data: There is no established aetiology for adolescent idiopathic scoliosis and the reasons for the progression of the curve are still unknown. But there is an agreement regarding multifactorial nature of the aetiology among many authors. One of the interesting factors suggested is asymmetry in the ground reaction forces during walking and their relation to the deformity, indicated by gait analysis studies. Studies have also indicated that the cause and progression of the deformity in idiopathic scoliosis may be due to kinematic differences in the spine, pelvis and lower limb. If a relation could be established between the scoliotic curve and the centre of gravity, it is possible to draw some conclusions regarding the aetiology. There is no method or study till date which looked at the relation of scoliotic curve with the centre of gravity. Materials and Methods: Patients who were diagnosed with adolescent idiopathic scoliosis were selected. Informed consent was taken for gait analysis. 16 Markers were placed over the lower limb and force plate, using modified Helen Hays set. 5 markers were placed over the surface landmarks of selected spinous processes (C7, T6, T12, L3 and S2). Ground reaction forces and motion data were analysed, using APAS gait system and the lines of vectors were developed and correlated with the marker over the second sacral spinous process. Results: With the help of this method we were able to establish a relationship between the scoliotic curve and centre of gravity line. These in turn were expressed in terms of changes in the moment in relation to the midline of the coronal plane. The results indicated that the changes were proportional to the severity of the scoliotic curve. Conclusion: We present a new method of establishing the relation of scoliotic curve with the ground reaction force and the centre of gravity. Initial results obtained from this method indicate the asymmetries in the deviation of the centre of gravity line in relation to the curve, during walking. Ongoing studies based on this method, will help to understand the pathogenesis and aetiology of scoliosis on a biomechanical basis which can help in developing new treatment modalities and efficient management of these patients

Summary Statement. Using a weight-bearing force control task, age-related changes in muscle action were observed in osteoarthritic subjects, however, greater activation of rectus femoris and medial hamstring muscles in the OA group compared to control indicates greater cocontraction and varied stabilisation strategies. Introduction. Osteoarthritis (OA) is the most debilitating condition among older adults. OA is thought to be mechanically driven by altering the stabilising integrity of the joint. The main contributor to knee joint stability is that of muscular contraction. In cases where the history of a traumatic knee joint injury is not a causal factor, a change in muscle function, resulting in reduced strength and force control in believed to induce OA development and progression. Since age is also a determining factor of OA, the purpose of this study was to investigate the muscle activation patterns of young healthy adults (YC), older healthy adults (OC), and adults with OA during a standing isometric force control task. Patients & Methods. A force matching protocol was used to evaluate muscle activation patterns of 41 YC (23.1±1.9 years of age) 18 OC (59.7±5.14 years), and 19 OA (63.5±8.1 years). Subjects stood with their leg of interest fixed to a force platform and modulated ground reaction forces while exposing equal body weight to each leg. Surface electromyography (EMG) of 8 muscles that cross the knee joint, kinetics and kinematics were recorded while subjects generated 30% of their maximal force in 12 different directions, corresponding to various combinations of medial-lateral-anterior-posterior ground reaction forces. Processed EMG was normalised to previously recorded maximum voluntary isometric contraction (MVIC) and ensemble averaged into group means for each loading direction. Muscle activation patterns were displayed in EMG polar plots and were quantified with symmetry analyses, mean activation levels (X. EMG. ), directions (Φ), and specificity indices (SI). Group differences were tested with independent T-tests at the p<0.05 level. Results. Muscle activation patterns were similar between groups (i.e. symmetry and Φ). However, X. EMG. of 7 muscles was significantly greater in both the OA and OC groups compared to YC. OA group also demonstrated significantly greater X. EMG. in the rectus femoris and tensor fascia lata as well as lower SI in semitendinosus hamstrings compared to OC. Discussion/Conclusion. Our results indicate that regardless of loading direction, both OC and OA groups have greater levels of muscle co-contraction than YC. This is suggested to be an adaptive response to age-related changes in muscle strength and force control. Since individuals with OA have reduced muscle strength and force control compared to age-matched controls, our results suggest that the OA group's greater, less specific activation of knee joint muscles relative to the OC is this “stiffening” response adapted by the OA group, however, to an extent that may expose the joint to detrimental loading conditions, contributing to the progression of OA. Further investigation regarding age-related neuromuscular changes and their influence on joint loading conditions and development of OA is warranted

The relations among tissue quality, socket discomfort, gait characteristics, and socket pressures are not well established for the unilateral below-knee amputee population. These relations were evaluated for six amputees at seventeen regions of interest on the residual limb. Pressure sensors were placed directly on the residual limb. Peak dynamic socket pressures were not directly related to peak joint moments. However, increases in ground reaction forces (GRFs) related to increases in socket pressures. The relations among tissue quality, socket discomfort, gait characteristics, and socket pressures are not well established for the unilateral below-knee amputee population. The purpose of this study was to evaluate these relations for six amputees. A thorough understanding of pressure distribution between the residual limb and prosthetic socket is critical to socket design and limb health. The subjects ranged in age from thirty to seventy-two years of age. The inclusion criteria were male, unilateral transtibial amputation, ability to ambulate independently, non-diabetic, no debilitating health conditions, non-recent amputee. Tissue sensation and socket discomfort were evaluated at seventeen regions of interest on the residual limb. Tissue sensation was assessed using Semmes-Weinstein monofilaments to test light touch/deep pressure sensation, tuning fork to test vibration sensation, and pinprick to test pain sensation. Socket discomfort was assessed using 10 cm Visual Analogue Scale. Gait characteristics were recorded during walking using a Motion Analysis System. Socket pressure measurements were made using F-socket pressure sensors in conjunction with I-Scan software program. Pressure sensors were placed directly on residual limb. Gait characteristics and socket pressures were compared across three different testing days. The site-specific tissue sensitivity scores did not correlate with the socket discomfort scores. In addition, site-specific discomfort scores did not correlate with peak socket pressures recorded at subject’s normal walking speed. Significant day-to-day pressure differences were found at four of the seventeen areas of interest. Peak dynamic socket pressures were not directly related to peak joint moments. Two subjects demonstrated direct relations between ground reaction forces (GRFs) and socket pressure on the different test days. Funding: NSERC, Workers’ Compensation Board (Alberta), University of Calgary

Aims. The purpose of this study was to analyse the biomechanics of walking, through the ground reaction forces (GRF) measured, after first metatarsal osteotomy or metatarsophalangeal joint (MTP) arthrodesis. Patients and Methods. A total of 19 patients underwent a Scarf osteotomy (50.3 years, standard deviation (. sd. ) 12.3) and 18 underwent an arthrodesis (56.2 years,. sd. 6.5). Clinical and radiographical data as well as the American Orthopaedic Foot and Ankle Society (AOFAS) scores were determined. GRF were measured using an instrumented treadmill. A two-way model of analysis of variance (ANOVA) was used to determine the effects of surgery on biomechanical parameters of walking, particularly propulsion. Results. Epidemiological, radiographical and clinical data were comparable in the two groups and better restoration of propulsive function was found after osteotomy as shown by ANOVA (two way: surgery × foot) with a surgery effect on vertical forces (p < 0.01) and a foot effect on anteroposterior impulse (p = 0.01). Conclusion. Patients who underwent Scarf osteotomy had a gait pattern similar to that of their non-operated foot, whereas those who underwent arthrodesis of the first (metatarsophalangeal) MTP joint did not totally recover the propulsive forces of the forefoot. Take home message: The main findings of this study were that after surgical correction for hallux valgus, patients who underwent scarf osteotomy had a gait pattern similar to that of their non-operated foot in terms of forefoot propulsive forces (Fz3, Iy2), whereas those who underwent arthrodesis of the first MTP joint had not. Cite this article: Bone Joint J 2016;98-B:641–6

Introduction and Objective. Medial Knee Osteoarthritis (MKO) is associated with abnormal knee varism, this resulting in altered locomotion and abnormal loading at tibio-femoral condylar contacts. To prevent end-stage MKO, medial compartment decompression is selectively considered and, when required, executed via High Tibial Osteotomy (HTO). This is expected to restore normal knee alignment, load distribution and locomotion. In biomechanics, HTO efficacy may be investigated by a thorough analysis of the ground reaction forces (GRF), whose orientation with respect to patient-specific knee morphology should reflect knee misalignment. Although multi-instrumental assessments are feasible, a customized combination of medical imaging and gait analysis (GA), including GRF data, rarely is considered. The aim of this study was to report an original methodology merging Computed-Tomography (CT) with GA and GFR data in order to depict a realistic patient-specific representation of the knee loading status during motion before and after HTO. Materials and Methods. 25 MKO-affected patients were selected for HTO. All patients received pre-operative clinical scoring, and radiological/instrumental assessments; so far, these were also executed post-operatively at 6-month follow-up on 7 of these patients. State-of-the-art GA was performed during walking and more demanding motor tasks, like squatting, stair-climbing/descending, and chair-rising/sitting. An 8-camera motion capture system, combined with wireless electromyography, and force platforms for GRF tracking, was used together with an own established protocol. This marker-set was enlarged with 4 additional skin-based non-collinear markers, attached around the tibial-plateau rim. While still wearing these markers, all analyzed patients received full lower-limb X-ray in standing posture a CT scan of the knee in weight-bearing Subsequently, relevant DICOMs were segmented to reconstruct the morphological models of the proximal tibia and the additional reference markers, for a robust anatomical reference frame to be defined on the tibia. These marker trajectories during motion were then registered to the corresponding from CT-based 3D reconstruction. Relevant registration matrices then were used to report GRF data on the reconstructed tibial model. Intersection paths of GRF vectors with respect to the tibial-plateau plane were calculated, together with their centroids. Results. Pre-operative clinical and radiological scoring confirmed MKO and associated abnormal varism. The morphological characterization of GRF was successfully achieved pre- and post- HTO on patient-specific tibial plateau. Pre-operative GFR patterns and peaks, including those related to knee joint moments, were observed medially on the knee, as expected. In post-HTO, these resulted lateralized and much closer to the tibial plateau spine, as desired. In detail, when post- is compared to pre-op, the difference of the centroids were, on average, 54.6±18.1 mm (min÷max: 36.7÷72.8 mm) more lateral during walking and 52.5±28.5 mm (24.7÷87.6 mm) during stair climbing. When reported in % of the tibial plateau width, these values became 69.2±20.1 (46.1÷81.4) and 78.1±30.1 (43.4÷98.0), respectively. Post-op also clinical scores and GA revealed a considerable overall improvement, especially in functional performances. Conclusions. The reported novel approach allows a combination of motion data, including GFR, and tibial-plateau morphology. Relevant pre- and post-operative routine application offer a quantification of the effect of the original deformity and executed joint realignment, and an assistance for surgical planning in case of HTO as well as ideally in other orthopedic treatments

Osteochondroplasty procedure for cam deformity provides excellent outcomes on alleviating pain, improving quality of life and clinical function in femoroacetabular impingement syndrome (FAIS) patients. Although medium-term outcomes on gait biomechanics have been reported, it is unclear how it would translate to better hip muscle forces and joint loading in high range of motion tasks. The purpose of this study was to compare the muscle forces and hip joint contact forces (HCF) during a squat task in individuals before and after cam-FAIS surgical correction. Ten cam-FAIS patients prior and 2-years after osteochondroplasty, and 10 BMI- age- and sex-matched healthy control participants (CTRL) underwent 3D motion and ground reaction forces capture while performing a deep squatting task. Muscle and HCF were estimated using musculoskeletal modeling and comparisons were done using statistical parametric mapping (SPM). Postoperatives squatted down with a higher anterior pelvic tilt and higher hip flexion compared with the preoperatives. Preoperative semimembranosus generated lower forces than the two other groups on the squat ascending, with no differences detected between post-ops and CTRLs. Preoperatives also showed reduced forces for the distal, ischial and medial portions of the adductor magnus relative to the CTRLs, which although reduced, still presented differences postoperatively. Preoperative anterior and medial contact forces were significantly lower than the CTRL group during both phases of the squat. Postoperative vertical and medial forces were also lower compared to the CTRLs. However, with higher vertical forces during the ascent phase of the squat compared to the preoperative, the postoperative group, significantly increased its HCF magnitude. A higher anterior pelvic tilt was associated with an innate restoration of the pelvis position, once the cam deformity no longer existed. The increased force of the semimembranosus muscle while ascending the squat generated higher vertical HCF, which also influenced the increased HCF total magnitude. For any tables or figures, please contact the authors directly

The optimal correction of the weight bearing line during High Tibial Osteotomy has not been determined. We used finite element modelling to simulate the effect that increasing opening wedge HTO has on the distribution of stress and pressure through the knee joint during normal gait. Subject-specific models were developed by combining geometry from 7T MRI scans and applied joint loads from ground reaction forces measured during level walking. Baseline stresses and pressures on the articulating proximal tibial cartilage and menisci were calculated. Progressive osteotomies were then simulated to shift the weight-bearing line from the native alignment towards/into the lateral compartment (between 40 – 80% of medial-lateral tibial width). Changes in calculated stresses and pressures were recorded. Both stress and pressure decreased in the medial compartment and increased in the lateral compartment as increasingly valgus osteotomies were simulated. The models demonstrated a consistent “safe zone” for weight bearing line position at 50%-65% medial-lateral tibial width, outside of which compartment stresses and pressures substantial increased. This study suggests a safe correction zone within which a medial opening wedge HTO can be performed correcting the WBL to 55% medio-lateral width of the tibia

Identifying knee osteoarthritis (OA) patient phenotypes is relevant to assessing treatment efficacy, yet biomechanical variability has not been applied to phenotyping. This study aimed to identify demographic and gait related groups (clusters) among total knee arthroplasty (TKA) candidates, and examine inter-cluster differences in gait feature improvement post-TKA. Knee OA patients scheduled for TKA underwent three-dimensional gait analysis one-week pre and one-year post-TKA, capturing lower-limb external ground reaction forces and kinematics using a force platform and optoelectronic motion capture. Principal component analysis was applied to frontal and sagittal knee angle and moment waveforms (n=135 pre-TKA, n=106 post-TKA), resulting in a new uncorrelated dataset of subject PCscores and PC vectors, describing major modes of variability throughout one gait cycle (0–100%). Demographics (age, gender, body mass index (BMI), gait speed), and gait angle and moment PCscores were standardized and assessed for outliers. One patient exceeding Tukey's outer (3IQR) fence was removed. Two-dimensional multidimensional scaling followed by k-medoids clustering was applied to scaled demographics and pre-TKA PCscores [134×15]. Number of clusters (k=2:10) were assessed by silhouette coefficients, s, and stability by Adjusted Rand Indices (ARI) of 100 data subsets. Clusters were validated by examining inter-cluster differences at baseline, and inter-cluster gait changes (PostPCscore–PrePCscore, n=105) by k-way ANOVA and Tukey's honestly significant difference (HSD) criterion. Four (k=4) TKA candidate groups yielded optimum clustering metrics (s = 0.4, ARI=0.75). Cluster 1 was all-males (male:female=19:0) who walked with faster gait speeds (1>2,3), larger flexion angle magnitudes and stance-phase angle range (PC1 & PC4 1>2,3,4), and more flexion (PC2 1>2,3,4) and adduction moment (PC2 & PC3 1>2,3) range patterns. Cluster 1 had the most dynamic kinematics and kinetic loading/unloading range amongst the clusters, representing a higher-functioning (less “stiff”) male subset. Cluster 2 captured older (2>1,3) males (31:1) with slower gait speeds (2 4), and lower flexion angle magnitude (PC1 3 2,3) and less stiff kinematic and kinetic patterns relative to Clusters 2 and 3, representing a higher-functioning female subset. Radiographic severity did not differ between clusters (Kellgren-Lawrence Grade, p=0.9, n=102), and after removing demographics and re-clustering, gender differences remained (p < 0 .04). Pre-TKA, higher-functioning clusters (1&4) had more dynamic loading/un-loading kinetic patterns. Post-TKA, high-functioning clusters experienced less gait improvement (flexion angle PC2, 1,4 < 3, p≥0.004, flexion moment PC2, 4 < 2,3), with some sagittal range patterns decreasing postoperatively. TKA candidates can be characterized by four clusters, differing by demographics and biomechanical severity features. Post-TKA, functional gains were cluster-specific, stiff-gait clusters experienced more improvement, while higher-functioning clusters experienced less gain and showed some decline. Results suggest the presence of cohorts who may not benefit functionally from TKA. Cluster profiling may support triaging and developing targeted OA treatment strategies, meeting individual function needs

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

Previous studies (. Chen et al., 2003. ; . Kaufmann et al., 2001. ) have shown that persons with osteoarthritis (OA) walk more slowly with lower cadence, have lower peak ground reaction forces and load their injured limb at a lower rate than healthy age matched subjects. However, another study (. Mündermann et al., 2005. ) found that patients with severe bilateral OA loaded their knee joint at a higher rate. They also found these patients had higher knee adduction moments and lower hip adduction moments. It has been reported (. McGibbon and Krebs 2002. ) that when subjects with knee OA are required to walk at the same speed as healthy subjects they generate more power at the hip joint to help overcome reduced knee power and aid in the advancement of the leg prior to the swing phase of the gait cycle. . Myles et al. (2002). reported that patients with knee OA have reduced knee range of motion during walking. This paper presents detailed kinematic and kinetic data collected on a large group of patients with advanced knee osteoarthritis to show the differences in the gait of these patients just prior to surgery compared with age-matched control group. This study was approved by the Sun Health Institutional Review Board. Subjects volunteered to participate in the study and signed informed consent prior to testing. Subjects were excluded if the had significant diseases of the other joints of the lower extremity or a diagnosed disorder with gait disturbance. Motion data was captured using a ten-camera motion capture system (Motion Analysis Corp., Santa Rosa, CA). Three-dimensional force data was recorded using four floor embedded force platforms (AMTI Inc., Watertown, MA). Patients were asked to walk at a self selected speed along a 6.5 meter walkway. A minimum of five good foot strikes for each limb were recorded. Data were collected using EVaRT 5 software (Motion Analysis Corp., Santa Rosa, CA) and analyzed using OrthoTrak 6.2.8 (Motion Analysis Corp., Santa Rosa, CA) and MatLab software (The Mathworks Inc., Natick, MA). Statistical analysis was performed using SPSS 14.0 software (SPSS Inc., Chicago, Il) (α = 0.05). Eighty-six patients (71 ± 7 years) along with sixty-four control subjects (65± 10 years) volunteered to participate in the study. All measured temporal and spatial parameters showed significant differences between the OA patients and the control group. The OA patients were found to walk at a significantly lower velocity (p< .01) and cadence (p< .01) using a wider step width (p< .01) than the control subjects. Patients had their injured knee significantly more flexed at foot strike (p< .01) but flexed the knee significantly less during swing (p< .01) when compared to the control group. Patients had significantly higher knee flexion angles as well as hip flexion and abduction angles during stance. Knee varus angles were significantly higher for the OA patients during stance (p< .01) but not during swing when compared to the control group. Significant increases in pelvic tilt and pelvic obliquity were measured during the stance phase. Hip abduction angles during stance were significantly lower for the OA group. Patients generated significantly lower vertical ground reaction forces during stance (p< .01) while sagittal plane kinetic analysis showed significantly lower external knee flexion moments (p< .01) and knee power generation (p< .01) during this phase of the gait cycle. Analysis of frontal plane angles showed OA patients had a significantly higher maximum knee varus angle during stance as well as generating a higher external knee varus moment (p=.03) during this phase of the gait cycle. Changes in gait measured in this study support and enhance findings from previous studies. OA patients appeared to walk with a more crouched posture with higher knee and hip flexion angles through mid stance. This along with lower velocity and cadence and a larger step width would indicate a desire for more stability while walking. Patients also flexed their knees more at foot strike in an attempt to absorb the forces generated during weight acceptance. While knee flexion angles measured for the OA group were similar to the control subjects during the initial period of stance, the OA patients did not extend their knees as much during mid stance indicating a desire to reduce the angular rotation of the knee while in single support. Changes measured in frontal plane angles of the hip and pelvis may be an attempt to compensate for the different angles generated by the knee during stance. The differences in hip and knee angles measured during stance for patients and controls allowed patients to have reduced peak external knee flexion moments during initial stance but a higher knee flexion moment at mid stance. The reduction in knee angular change during stance and the reduced cadence meant power absorption during early and late stance and generation during mid stance was much lower for the OA patients than the control group. All the changes noted appear to be designed to limit the movement of the knee joint while loaded and reduce the peak loads in an effort to reduce pain at the affected joint while at the same time increase stability during gait. These data show the differences that exist between the gait patterns of patients with advanced osteoarthritis and healthy age-matched persons and highlight the changes that are necessary following knee replacement surgery and rehabilitation to return the gait of these patients to normal

Aim. Anatomical reduction and Stable fixation of Lisfranc injuries is considered the gold standard. There is controversy about how it is best achieved. Some surgeons would advocate routine open anatomical reduction, which as a concept was popular in 1980s but the same anatomical reduction and fixation can be achieved percutaneously. We describe our method of close reduction and percutaneous fixation and present our results. Materials and methods. 22 patients with a minimum follow up of 12 months were included. We achieved satisfactory anatomical reduction percutaneously in all patients and internal fixation was performed using cannulated screws for medial and middle columns. Functional outcome was evaluated using Foot and Ankle Disability Index (FADI) and components of this score were analysed individually to assess which domain was most affected. Vertical ground reaction forces were measured using a force plate in a walking platform. Results. The average age at operation was 48 years (17–67). Mean follow up was 20 months (13–60). The average Foot & Ankle Disability Index at final follow up was 79 (66–94). No loss of reduction or metal breakage was noted. Walking on uneven surface, going down stairs, heavy work and pain first thing in the morning were the domains of functional Index that showed poor recovery. None of the patients had pain at rest. Only three patients found it extremely hard to return to recreational activities. None of the patients had problems related to wound. Gait analysis showed a prolonged push-off (p=0.22) and significantly prolonged pre-swing phase (p=0.015) of the affected limb. Conclusions. Percutaneous reduction and fixation technique for Lisfranc injuries provides predicatable good functional outcome and gait pattern similar to open tecchinques with a potentially decreased risk of wound problems

Purpose. Pilon fracture is a severe injury which has a great impact on the patients' lives, but in what extend is not clear yet in the literature. The purpose of this study was to investigate the gait alternations after treatment of patients who had pilon fractures. Materials & Methods. We have evaluated the gait pattern of patients who were treated with circular Ilizarov frame following pilon fractures in our department. The gait was tested by using a force plate in a walking platform. Ground Reaction Forces (GRF) and timing of gait phases data were collected during level walking at self-selected speeds. The patients performed two walking tasks for each limb and the collected data were averaged for each limb. Demographic, clinical, radiological, trauma outcome (COST) and quality of life questionnaire (SF-12) data were also collected. Results. We have analysed the gait through the GRF of twelve patients (aged 44.9 ±12.4 years), who had undergone treatment with circular Ilizarov frame following pilon fractures (67% were male). The tests were performed at an average of 10.5 months after the initial treatment. SF-12 Mental scores have returned to normal (mean 56.4 ±11.6) but physical scores remained impaired (mean 41.8 ±8.4). COST questionnaire scores reached average levels (47.1 ±15) in all dimensions (Symptoms: 51.4 ±16, Function: 44 ±14 and Mental Status: 56.6 ±16). During the push-off phase all the plantar flexor muscles are activated and the ankle plantar flexes to achieve the push off. It seems that this motion, is not achieved adequately with the affected limb and the patients are using their normal limb earlier (pre-swing is the start of the double support of the gait) in order to progress in their gait circle. Conclusions. Ten months following treatment with circular ilizarov frame for pilon fracture the patients still have impaired gait pattern. The differences can be explained by the lack of plantar flexion of the ankle which results to poorer push-off of the affected limb

Background:. Little is known about the forces carried by the Taylor Spatial Frame (TSF) hexapod fixator. Our aim was to measure the TSF resultant force and how this changed during the consolidation phase. Method:. Five patients undergoing correction of tibial deformities were recruited. Measurements were taken at 2, 4, 8 and 12 weeks post-correction during various activities. Instrumented struts incorporating strain gauges measuring axial force were temporarily used each time. Strut forces and lengths were used to determine frame kinetics. The resultant axial fixator forces and moments were calculated relative to sitting. Ground reaction forces (GRF) were measured using the treadmill force plates. Results & Discussion:. Due to the subjects' varying confidence in weight bearing the forces varied both inter- and intra-activity and over post-corrective time. Variation in individual strut forces produced a resultant force and bending moment across the fixation. As the healing bone assumed more load over time there was a reduction in the force and bending excursions across the frame as a percentage of GRF, achieving a minimum by 8 weeks. Conclusion:. Instrumented TSFs are a useful means of assessing the forces acting during healing. Monitoring of these forces can determine optimal removal

Introduction. There is limited evidence assessing the effect of the Ankle Foot Orthosis (AFO) on gait improvements in diplegic cerebral palsy. In particular, the effect of the AFO on vertical forces during gait has not been reported. Appropriate vertical ground reaction forces are crucial in enabling children with CP to walk efficiently. This study investigated the effect of AFO application on the vertical forces in gait, particularly the second vertical peak in force (FZ2) in late stance. The force data was compared with the barefoot walk. Patients and Methods. A retrospective analysis of nineteen children (8M,11F) who met inclusion criteria of a diagnosis of spastic diplegic CP, ability to walk independently barefoot and also using bilateral rigid AFOs were included. Gait data were acquired using the Vicon-Nexus ® motion-capture. Resulting ground reaction force data were recorded. Appropriate statistical methods assessed significance between barefoot and AFO data. Results. 68.4% of subjects experienced increase in FZ2 magnitude in left leg and 63.2% experienced objective increase in right leg after AFO application. Mean increased in FZ2 was 5.33N in left leg and 8.53 N in right leg. Results indicate significant improvement in amplitude of FZ2 generation with AFO application, significantly increased gait efficiency, and a significantly normalized pattern of vertical force produced during gait. Discussion. The AFO is effective in enabling children with diplegic CP to achieve efficient gait patterns. Our study is the first to our knowledge that focuses on the effect of AFO on specifically vertical ground reaction force produced in gait

Purpose. Tibia plateau fractures are severe knee injuries which have a great impact on the patients' lives, but in what extend is not clear yet in the literature. The purpose of this study was to investigate the gait alternations after treatment of patients who had severe tibia plateau fractures which were treated with circular ilizarov frame. Materials & Methods. We have evaluated the gait pattern of patients who were treated with circular Ilizarov frame after severe tibia plateau fractures (Schatzker IV-VI) in our department. The gait was tested by using a force plate in a walking platform. Ground Reaction Forces (GRF) data were collected during level walking at self-selected speeds. The patients performed two walking tasks for each limb and the collected data were averaged for each limb. Demographic, clinical, radiological and quality of life questionnaire (SF-12) data were also collected. Results. We have analysed the gait through the GRF of fifteen patients (aged 50.8 ±17.3 years), who had undergone treatment with circular Ilizarov frame following severe tibia plateau fractures (Schatzker IV-VI). Nine were male and six were female. The tests were performed at an average of 13.2 months after the initial treatment. SF-12 Mental scores have returned to normal (mean 54.6 ±12.3) but physical scores remained impaired (mean 40.6 ±10.8). A one-way repeated measures ANOVA was conducted to compare the GRFs and gait timing data of the affected limb with the normal one. Single limb support interval was significantly reduced to the affected limb (p=0.001) and terminal stance phase was prolonged for the normal limb (p=0.035). During this phase of the gait circle the knee is on its maximum flexion and the quadriceps contracts to bring the femur above the tibia. It seems that these patients during the gait circle reduce the flexion of their affected knee to make their single stance shorter. To the normal limb the patients manage to reduce more the GRFs during the mid-stance phase (F2 force), this difference do not reach significance, but illuminates the tendency of reduced knee flexion in that phase. The rest of the GRF and gait timing data did not had significant differences. Conclusions. One year after severe tibia plateau fracture treated with circular ilizarov frame the patients manage to return to almost normal gait pattern. Reduce single limb stance and terminal stance phase to the affected knee can be explained by the tendency of not flexing their deficient knee as much during that gait phase

Estimates of knee joint loadings were calculated for 12 normal subjects from kinematic and kinetic measures obtained during both level and downhill walking. The maximum tibiofemoral compressive force reached an average load of 3.9 times body-weight (BW) for level walking and 8 times BW for downhill walking, in each instance during the early stance phase. Muscle forces contributed 80% of the maximum bone-on-bone force during downhill walking and 70% during level walking whereas the ground reaction forces contributed only 20% and 30% respectively. Most total knee designs provide a tibiofemoral contact area of 100 to 300 mm. 2. The yield point of these polyethylene inlays will therefore be exceeded with each step during downhill walking. Future evaluation of total knee designs should be based on a tibiofemoral joint load of 3.5 times BW at 20° knee flexion, 8 times BW at 40° and 6 times BW at 60°

Valgus unloader knee braces are a conservative treatment option for medial compartment knee osteoarthritis (OA). These braces are designed to reduce painful, and potentially injurious compressive loading on the damaged medial side of the joint through application of a frontal-plane abduction moment. While some patients experience improvements in pain, function, and joint loading, others see little to no benefit from bracing [1]. Previous biomechanical studies investigating the mechanical effectiveness of bracing have been limited in either their musculoskeletal detail [2] or incorporation of altered external joint moments and forces [3]. The first objective was to model the relative contributions of gait dynamics, muscle forces, and the external brace abduction moment to reducing medial compartment knee loads. The second objective was to determine what factors predict the effectiveness of the valgus unloading brace. Seventeen people with knee OA (8 Female age 54.4 +/− 4.2, BMI 30.00 +/− 4.0 kg/m. 2. , Kellgren-Lawrence range of 1–4 with med. = 3) and 20 healthy age-matched controls participated in this study which was approved by the institutional ethics review board. Subjects walked across a 20m walkway with and without a Donjoy OA Assist knee brace while marker trajectories, ground reaction forces, and lower limb electromyography were recorded. The external moment applied by the brace was estimated by multiplying the brace deformation by is pre-determined brace-stiffness. For each subject, a representative stride was selected for each brace condition. A generic musculokeletal model with two legs, a torso, and 96 muscles was modified to include subject-specific frontal plane alignment and medial and lateral contact locations [4]. Muscle forces, and tibiofemoral contact forces were estimated using static optimization [4]. We defined brace effectiveness as the difference in the peak medial contact force between the braced and the unbraced conditions. A stepwise regression analysis was performed to predict brace effectiveness based on: X-ray frontal plane alignment, medial joint space, KL grade, mass, WOMAC scores, unbraced walking speed, trunk, hip and knee joint angles and moments. The OA Assist brace reduced medial joint loading by approximately 0.1 to 0.2 BW or roughly 10%, during stance. This decrease was primarily due to the external brace abduction moment, and not changes in gait dynamics, or muscle forces. The brace effectiveness could be predicted (R. 2. =0.77) by the KL grade, and the magnitude of the hip adduction moment in early stance (unbraced). The brace was more effective for those that had larger hip adduction moments and for those with more severe OA. The valgus knee brace was found to reduce the medial joint contact force by approximately 10% as estimated using a musculoskeletal model. Bracing resulted in a greater reduction in joint contact force for those who had more severe OA while still maintaining a hip adduction moment similar to that of healthy controls

Introduction. Alignment of the acetabular cup and femoral components directly affects hip joint loading and potential for impingement and dislocation following total hip arthroplasty (THA) [1]. Changes to the lines of action and moment generating capabilities of the muscles as a result of component position may influence overall patient function. The objectives of this study were to assess the effect of component placement on hip joint contact forces (JCFs) and muscle forces during a high demand step down task and to identify important alignment parameters using a probabilistic approach. Methods. Three patients following THA (2 M: 28.3±2.8 BMI; 1 F: 25.7 BMI) performed lower extremity maximum isometric strength tests and a step down task as part of a larger IRB-approved study. Patient-specific musculoskeletal models were created by scaling a model with detailed hip musculature [2] to patient segment dimensions and mass. For each model, muscle maximum isometric strengths were optimized to minimize differences between model-predicted and measured preoperative maximum isometric joint torques at the hip and knee. Baseline simulations used patient-specific models with corresponding measured kinematics and ground reaction forces to predict hip JCFs and muscle forces using static optimization. To assess the combined effects of stem and cup position and orientation, a 1000 trial Monte Carlo simulation was performed with input variability in each degree of freedom based on the ±1 SD range in component placement relative to native geometry reported by Tsai et al. [3] (Figure 1). Maximum confidence bounds (1–99%) were predicted for the hip JCF magnitude and muscle forces for three prime muscles involved in the task (gluteus medius, gluteus minimus and psoas). HJC confidence bounds were compared to Orthoload measurements from telemetric implants from 6 patients performing the step down task. Sensitivity of hip JCF and muscle force outputs was quantified by Pearson Product-Moment correlation between the input parameter and the value of each output averaged across four points in the cycle. Results. Variation in the placement of the stem and cup produced an average maximum confidence bound (1–99%) in hip JCF of 277.7±91.1N and forces of 259.4±58.3N in the gluteus medius for all three patients (Figure 2). Sensitivity to cup and stem placement varied among the three patients; however, in general, hip JCFs were more sensitive to the position of the stem than the cup (Figure 3). Hip JCF was most sensitive to stem anteversion (0.64±0.10) and the superior/inferior stem position (0.42±0.19). Discussion. Variation in stem anteversion and medial/lateral cup position contributed the largest amount of variability in hip JCF and muscle forces during a step down task. The probabilistic analysis characterized bounds for output parameters, considering interactions between alignment parameters. Alignments that avoid increases in JCF and muscle loading during high demand tasks may lead to earlier recovery of function, by reducing muscle fatigue and the need to develop compensatory movement patterns. Acknowledgements. This research was supported in part by DePuy-Synthes

Intro. Across much of medicine, activity levels predict life expectancy, with low levels of activity being associated with increased mortality, and higher levels of activity being associated with longer healthier lives. Resurfacing is a technically demanding procedure that has suffered significant fallout from the failure of a couple of poorly performing designs. However strong evidence associates resurfacing with improved life expectancy in both the short and longer term following surgery. We wondered if there was any relationship between the function of hips following surgery and the extent of that surgery. Could a longer stem inside the femur be the reason for a slightly reduced step length? We proposed the nul hypothesis that there was no clinically relevant difference between stem length and gait. Method. After informed consent each subject was allowed a 5 minute acclimatisation period at 4km/hr on the instrumented treadmill (Kistler Gaitway, Amherst, NY). Their gait performance on an increasing incline at 5, 10 and 15%. At all 0.5km incremental intervals of speed, the vertical component of the ground reaction forces, center of pressure and temporal measurements were collected for both limbs with a sampling frequency of 100Hz over 10sec. They were also asked to log onto our JointPRO website and report their function using Oxford, EQ5D, and Imperial scores. Owing to current restrictions in indications, the patient groups selected were not comparable. However, from our database of over 800 patients who have been through the gait lab. 82 subjects were tested from 2 diagnostic groups (29 conventional THR, 27 hip resurfacing) and compared with a slightly younger group of 26 healthy controls. Patients were excluded if less than 12 months postop, or with any other documented joint disease or medical comorbidities which might affect gait performance. Body weight scaling was also applied to the outputted mechanical data to correct for mass differences. All variables for each subject group were compared to each other using an analysis of variance (ANOVA) with Tukey post hoc test with significance set at α=0.05. Results. The experimental groups were reasonably matched for sex, height and BMI, although the controls were rather younger, and the hip replacements rather older (young hip resurfacings were excluded for lack of good controls). Any differences did not reach significance. Oxford hip scores and EQ5D were almost identical for the two experimental groups. The THR group walked 10% slower than control (1.8 (±0.2)m/sec vs 2.0 (±0.1)m/sec). while the HRA group walked 5% faster (2.1(±0.2)m/sec). The difference between THR and control was significant (p<0.05). (See Figure 1). Discussion. This data records a 15% difference in top walking speed between THR and HRA, far exceeding the 5% threshold of clinical relevance. We therefore consider this improved functional outcome to be clinically relevant, and report with increasing confidence that hip resurfacings is an effective intervention in the treatment of hip disease with clinically relevant superiority over THR, even in a group with an average age of 60

Introduction. Financial and human cost effectiveness is an increasing evident outcome measure of surgical innovation. Considering the human element, the aim is to restore the individual to their “normal” state by sparing anatomy without compromising implant performance. Gait lab studies have shown differences between different implants at top walking speed, but none to our knowledge have analysed differing total hip replacement patients through the entire range of gait speed and incline to show differences. The purpose of this gait study was to 1) determine if a new short stem femoral implant would return patients back to normal 2) compare its performance to established hip resurfacing and long stem total hip replacement (THR) implants. Method. 110 subjects were tested on an instrumented treadmill (Kistler Gaitway), 4 groups (short-stem THR, long-stem THR, hip resurfacing and healthy controls) of 28, 29, 27, and 26 respectively. The new short femoral stem patients (Furlong Evolution, JRI) were taken from the ongoing Evolution Hip trial that have been tested on the treadmill minimum 12months postop. The long stem total hip replacements and hip resurfacing groups were identified from our 800+ patient treadmill database, and only included with tests minimum 12 months postop and had no other joint disease or medical comorbidities which would affect gait performance. All subjects were tested through their entire range of gait speeds and incline after having a 5 minute habituation period. Speed were increased 0.5kmh until maximum walking speed achieved and inclines at 4kmh for 5,10,15%. At all incremental intervals of speed 10seconds ere collected, including vertical ground reaction forces (normalized to body mass), center of pressure and temporal measurements were for both limbs (fs=100Hz). Symmetry Index(SI) were calculated on a range of features comparing leg with implanted hip to the contralateral normal hip. Group means for each feature for each subject group were compared using an analysis of variance (ANOVA) with Tukey post-hoc test with significance set at α=0.05. Results. The four groups were reasonably matched for demographics and the implant groups for subjective outcome measures (Oxford Score & EQ5D). Hip resurfacing group had a clear top walking speed advantage, but when assessing SI on all speeds and incline, no groups were significantly different (Figure 1-3). Push-off and step length was statistically less favorable for the short/long stemmed THR group (p=0.005–0.05) depending on speed/incline comparing only implanted side. Discussion. The primary aim of this study was to determine if implant design affected gait symmetry and performance. Interestingly, irrespective of implant design, symmetry with regards to weight acceptance, impulse, push-off and step length was returned to normal when comparing to healthy controls. However individual implant performance on the flat and incline, showed inferior (p<0.05) push-off force and step length in the short stem and long stem THR groups when compared to controls. Age and gender may have played a part for the short stem group. It appears that the early gait outcomes for the short stem device are promising. Assessment at the 3-year mark should be conclusive

Financial and human cost effectiveness is an increasing evident outcome measure of surgical innovation. Considering the human element, the aim is to restore the individual to their “normal” state by sparing anatomy without compromising implant performance. Gait lab studies have shown differences between different implants at top walking speed, but none to our knowledge have analysed differing total hip replacement patients through the entire range of gait speed and incline to show differences. The purpose of this gait study was to 1) determine if a new short stem femoral implant would return patients back to normal 2) compare its performance to established hip resurfacing and long stem total hip replacement (THR) implants. 110 subjects were tested on an instrumented treadmill (Kistler Gaitway, Amherst, NY), 4 groups (short-stem THR, long-stem THR, hip resurfacing and healthy controls) of 28, 29, 27, and 26 respectively. The new short femoral stem patients (Furlong Evolution, JRI) were taken from the ongoing Evolution Hip trial that have been tested on the treadmill with minimum 12months postop. The long stem total hip replacements and hip resurfacing groups were identified from out 800 patient gait database. They were only chosen if they were 12 months postop and had no other joint disease or medical comorbidities which would affect gait performance. All subjects were tested through their entire range of gait speeds and incline after having a 5 minute habituation period. Speed intervals were at 0.5kms increments until maximum walking speed achieved and inclines at 4kms for 5, 10, 15%. At all incremental intervals of speed, the vertical component of the ground reaction forces, center of pressure and temporal measurements were collected for both limbs with a sampling frequency of 100Hz. Body weight scaling was applied to correct for mass differences and a symmetry index to compare the implanted hip to the contralateral normal hip. All variables for each subject group were compared to each other using an analysis of variance (ANOVA) with Tukey post hoc test with significance set at α=0.05. The four experimental groups were reasonably matched for demographics and the implant groups for PROMs. Hip resurfacing had a clear top walking speed advantage, but when assessing the symmetry index on all speeds and incline, all groups were not significantly different. Push-off and step length was statistically less favourable for the short/long THR group (p=0.005–0.05) depending on speed/incline. The primary aim of this study was determine if implant design affected gait symmetry and performance. Interestingly, irrespective of implant design, symmetry with regards to weight acceptance, impulse, push-off and step length was returned to normal when comparing to healthy controls. However individual implant performance on the flat and incline, showed inferior (p<0.05) push-off force and step length in the short stem and long stem THR groups when compared to controls. Age and gender may have played a part for the short stem group. It appears that the early gait outcomes for the short stem device are promising. Assessment at the 3 year mark should be conclusive

Introduction:. Direct anterior approach (DAA) total hip arthroplasty (THA) has been reported to be a muscle sparing approach. The purpose of this study was to compare gait patterns over time between patients undergoing THA via DAA and posterior approach (PA). Methods:. 22 patients with unilateral primary hip osteoarthritis were prospectively enrolled and gait analysis was performed prior to, at 6 months and 1 year following THA via DAA and PA. All PA THA's were performed by a single surgeon from January 2008 to February 2009; all DAA THA's were performed by the same surgeon at the same institution from January 2010 to May 2011 with similar design of uncemented acetabular, femoral components and bearing surfaces. Reflective markers were placed on the lower extremity and motion data collected using six infrared cameras (Qtrac, Qualysis). Ground reaction forces were recorded with a multicomponent force plate (Kistler). A repeated-measures ANOVA was used to compare changes in gait parameters over time. Harris Hip Score was used to quantify pain and function. Results:. There were 11 patients in both groups with similar age, sex and BMI distribution. Postoperatively, both groups demonstrated improvement in flexion/extension range of motion (ROM) (p = 0.006), peak flexion (p = 0.05) and extension moments (p = 0.004) with no differences between groups. Internal/external ROM improved significantly and was higher in DAA group as compared to PA group (p = 0.05). Gait velocity and single-leg stance time improved significantly in PA group (p = 0.001), but they were similar between groups postoperatively. Pain and function scores were also similar. Conclusions:. THA performed via DAA and PA offer similar improvement in gait parameters at 6 months and 1 year follow-up with the exception of internal/external ROM. This might be indicative of altered hip mechanics related to release and repair of external rotators during PA THA

The purpose of this study was to investigate the energy cost of walking after total ankle arthroplasty (TAA), and to investigate if possible differences could be attributed to changes in external mechanical work required for the step-to-step transition. Eleven patients, 6 months to 4 years after successful unilateral TAA, and 11 healthy controls walked on a treadmill at a self-selected speed (SWS) and a fixed walking speed (FWS, 1.25 m/s). Ground reaction forces and oxygen uptake were measured. External mechanical work was analyzed using the double inverted pendulum model. At SWS, velocity in the TAA group was reduced (v=1.29 vs 1.42 m/s, p=0.05) but metabolic energy cost was not different (E=2.50 vs 2.24 J/kg/m, p=0.32). At FWS, metabolic energy cost in the TAA patients was significantly higher (E=2.58 vs 1.96 J/kg/m, p=0.003). The difference in metabolic energy cost at FWS coincided with an increased negative work in the leading leg and reduced positive work in the trailing leg with TAA during double support. Although this indicates that the mechanical work for the step-to-step transition increases, the total external mechanical work over a complete stride was not different between the TAA and the control group. TAA patients walk at a higher metabolic energy cost. This cannot be explained by differences in external mechanical work. Other factors, such as changes in muscle function, should be taken into account

Introduction: The foot is a very complex structure acting as the platform for all gait patterns. At present, little is known about the exact biomechanics of the foot due to the difficulties in modeling all of the components of the foot accurately. This has made it virtually impossible to develop a complete understanding of the aetiology of many diseases of the foot including hallux rigidus. We hypothesize that sagittal plane incongruency of the rotation of the 1. st. Metatarsophalangeal Joint (MTPJ), or an increase in the tension of the intrinsic plantar flexors is responsible for the development of hallux rigidus. Materials & Methods: Ground reaction forces and kinematic data from gait analysis together with anthropometric data from MRI scans of a 24 y.o. female were used to create a Mimics model of the articulation of a normal 1st MTPJ during a gait cycle. The centre of rotation was calculated by triangulating the articular surfaces. Finite element analysis was performed on the model and on similar models with the hypothesized;. joint incongruency,. an increased tension in the Flexor Hallicus Brevis and. an increased tension in the plantar fascia. Results: The results demonstrated a significant increase in the peak stresses, contact areas and stress distributions between the incongruent models compared to the congruent models. Discussion: To the best of our knowledge this is the most accurate FE model of the 1st MTPJ calculated. Hallux Rigidus is a very common forefoot disorder, with multiple etiologies and treatments advocated. This model demonstrates that an increased tension in the plantar flexors results in a reduced ROM with increased contact stresses on the joint surface. Conclusion: While it is known Hallux Rigidus has a multi-factorial etiology, the authors feel the above study demonstrates an important inherent etiology

Introduction and Objective: Although the causation and progression of adolescent idiopathic scoliosis (AIS) remains unclear, a recent review has highlighted a series of possible aetiological factors. Additionally, research investigations have indicated that the kinematic differences in various body segments may be a major contributing factor. The value of gait analysis systems employed to measure dynamic back movements in furthering understanding of spinal deformity has also been demonstrated by various studies. Research employing gait measurements have indicated asymmetries in the ground reaction forces and have suggested relationship between these asymmetries, neurological dysfunction and spinal deformity. This investigation, which formed part of a wider comprehensive study, was aimed at identifying asymmetries in lower limb kinematics and pelvic and back movements during level walking in scoliotic subjects that could be related to the spinal deformity. Design and Methodology: The research employed a movement analysis system and a strain gauge force platform to estimate time domain kinetic parameters and other kinematic parameters in the lower extremities, pelvis and back. 16 patients with varying degrees of deformity, scheduled for surgery within a week took part in the study. Results and conclusions: The findings have demonstrated the presence of asymmetries in kinetic parameters in the scoliotic subject and have also served to highlight the value of using kinetic and kinematic parameters in developing the understanding of the pathogenesis and aetiology of scoliosis. In addition, the results have also indicated that the variables identified in the study can be applied to initial screening and surgical evaluation of spinal deformities such as scoliosis. Further studies are being undertaken to validate these findings

Introduction. Femoral component design is a key part of hip arthroplasty performance. We have previously reported that a hip resurfacing offered functional improved performance over a long stem. However resurfacing is not popular for many reasons, so there is a growing trend towards shorter femoral stems, which have the added benefit of ease of introduction through less invasive incisions. Concern is also developing about the impact of longer stems on lifetime risk of periprosthetic fracture, which should be reduced by the use of a shorter stem. For these reasons, we wanted to know whether a shorter stem offered any functional improvement over a conventional long stem. We surmised that longer stems in hip implants might stiffen the femoral shaft, altering the mechanical properties. Materials and Methods. From our database of over 800 patients who have been tested in the lab, we identified 95 patients with a hip replacement performed on only one side, with no other lower limb co-morbidities, and a control group:. 19 with long stem implant, age 66 ± 14 (LONG). 40 with short stem implant, age 69 ± 9 (SHORT). 26 with resurfacing, age 60 ± 8 (RESURF). 43 healthy control with no history of arthroplasty, age 59 ± 10 (CONTROL). All groups were matched for BMI and gender. Participants were asked to walk on an instrumented treadmill. Initially a 5 minute warm up at 4 km/h, then tests at increasing speed in 0.5 km/h increments. Maximum walking speed was determined by the patients themselves, or when subjects moved from walking to running. Ground reaction forces (GRF) were measured in 20 second intervals at each speed. Features were calculated based on the mean GRF for each trial, and on symmetry measures such as first peak force (heel strike), second peak force (toe-off), the rate at which the foot was loaded and unloaded, and step length. Results. When measured by top walking speed, stemmed implants of either type appear slower than those which do not include the femoral shaft (resurfacing). The latter group walking speed was equal to the control group (Figure 1). When looking at the whole gait cycle at any one speed, no major differences appear in the first or second peak forces (Figure 2 – 5km/h, implanted side compared). When checked for asymmetry, resurfacing patients did not demonstrate any asymmetry between legs, while either stemmed groups demonstrated slight differences between legs in terms of force related features (Figure 3). Discussion. We sought to show if stem length has an impact on top walking speed and asymmetry of gait. This small study contributes to that debate. We could not demonstrate any functional superiority of the short over the long stem, but the short femoral stem seems to transmit load just as well as the longer stem, allowing good load transfer at toe-off, and comparable walking speed. The results stress the advantages of non stemmed implants as published before. Our study adds to the discussion as to whether long stems are still needed in primary arthroplasty

Summary. This study describes the use of a quasi-static, 6DOF knee loading simulator using cadaveric specimens. Muscle force profiles yield repeatable results. Intra-articular pressure and contact area are dependent on loading condition and ACL integrity. Introduction. Abnormal contact mechanics of the tibiofemoral joint is believed to influence the development and progression of joint derangements. As such, understanding the factors that regulate joint stability may provide insight into the underlying injury mechanisms. Muscle action is believed to be the most important factor since it is the only dynamic regulator of joint stability. Furthermore, abnormal muscle control has been experimentally linked to the development of OA [Herzog, 2007] and in vivo ACL strain [Fleming, 2001]. However, the individual contributions to knee joint contact mechanics remain unclear. Thus, the purpose of this study was to examine the effects of individual muscle contributions on the tibiofemoral contact mechanics using an in-vitro experimental protocol. Methodology. Contact mechanics of 6 fresh frozen cadaver knee specimens were evaluated using the UofO Oxford knee loading device. Various combinations of quadriceps-hamstring co-contraction ratios were applied to the knee while it was “suspended” between the hip and foot components of the device. Loads of six muscle groups were computed using a hill-type musculoskeletal model [Buchanan, 2004]. Simulated ground reaction forces were also applied to the knee to represent force profiles of weight acceptance during gait as it has been shown to produce peak knee joint force in the gait cycle [Shelburne et al., 2006]. For respective medial and lateral joint compartments, the mean contact area (MC-CA and LC-CA), mean contact pressure (MC-CP and LC-CP), peak pressure (MC-PP and LC-PP), and centre of force displacement (MC-COFD and LC-COFD) were determined using a 4011 piezoelectric sensor form Tekscan (Tekscan Inc. Boston, MA). Additionally, the ACL was resected and measurements were repeated. Pearson correlations (r) examined the reliability of measurements as well as the effect an ACL transection on articular loads. Results. Positive correlations were computed for the following: COFD with intact ACL (r=0.99), COFD with resected ACL (r=0.82), MC-COFD pre vs. post ACL- resection (0.91). Furthermore, preliminary results indicated a positive correlation between MC-CA and ACL integrity (r=0.97). Discussion. The repeatability of the measured dependant variables validates the use of the knee-loading device. Interestingly, contact mechanics are more variable post ACL resection for a given muscle loading condition, indicating a decrease in knee joint stability. Also, the COFD is dependent on the different ratios of muscle loads applied to the knee, which demonstrates the importance of muscle action to the modulation of contact forces

Summary Statement. Objectifying postoperative recovery of patients with comminuted tibial plateau fractures treated with a unilateral plate trough the use of a gait analysis system. Introduction. Gait analysis has been a proved method for assessing postoperative results in patients with different orthopedic afflictions of the lower limb such as hallux valgus, ankle instabilities, knee osteoarthritis and arthroplasties but it has rarely been used for postoperative assessment of proximal tibial fractures. The more traditional means of quantifying postoperative articular step-off and limb axis deviations such as conventional X Rays and CT scanning and the clinician and patient completed scores that subjectively assess the outcome are complemented by the analysis of gait patterns set to objectify the most important patient related factor - the gait. As controversy exists in literature regarding the optimal treatment for severe tibial plateau fractures we proposed a gait study to evaluate locked angle unilateral plate osteosynthesis. Patient & Method: A computerised motion analysis system and a sensor platform were used to gather gait data from 15 patients with unilateral tibial plateau fractures graded Shatzker V and VI treated with a angular stable locked lateral plate osteosynthesis. Gait analysis was performed postoperatively based on patient availability and as soon as ambulation was possible and permitted without auxiliary support (crutches) at 4 (mean of 4,6), 6 (mean of 6,2) and 12 (mean of 11,7) months respectively, at a naturally comfortable walking. All patients were evaluated using classic anteroposterior and lateral knee radiography and were asked to fill the KOOS score questionnaire at the time of the gait analysis session. Results. The spatial-temporal and angular parameters revealed the expected postoperative decrease in ROM in both flexion and extension of the knee. Step and stance time objectively decreased between measuring session with an increase in single support of 3,7% mean value. A constant increase in walking speed was noted from a mean of 42 cm/sec (cadence of 31 st/min) at 4 months to a speed of 90 cm/sec (mean of 49 st/min cadence). We also determined a asymmetrical and wider walking base, increased area of support during single leg standing, decreased stance and increased swing phases for the injured knee compared to contralateral. Discussion. All patients in the study were subjectively satisfied with the results of the treatment, however we were able to detect quantifiable differences of gait parameters such between the injured and the contralateral knee such as step, stance and swing time and in knee flexion and adduction, combined with a modified, wider walking base. Ground reaction forces were strongly related to score improvement and thus directly reflected the healing at the fracture site

Aim: Evaluation of clinical, electromyographic and gait analysis results after constrained revision total knee arthroplasty. Material and Methods: 14 patients (mean age 67 years, 54-78) were evaluated 28.5 months (range, 6.5 to 61.4 months) after revision arthroplasty using constrained total knee endoprostheses (Genesis, Blauth). Clinical evaluation was carried out using HSS, Knee Society, Tegner Activity, and Patellar scores. A three-dimensional, quantitative gait analysis and simultaneous epicutaneous electromyographic recordings of 7 muscles surrounding the knee were carried out on all patients. 11 healthy volunteers (mean age 69 years, 60-75) served as control group. Results: Patients achieved 68 points in HSS, 125 in Knee Society, 1.3 in Tegner, and 19.1 in Patellar scores. Compared to the controls, all patients showed minor functional results. Electromyographic amplitudes of 5 muscles of the operated leg were significantly decreased compared to the contralateral side as well as the control group. Besides maximum knee extension all gait analysis parameters differed significantly between patients and controls. On the other hand, operated and uninvolved patients’ legs differed only in maximum knee extension in gait analysis. Significant correlations between clinical scores and ground reaction forces as well as electromyo-graphic levels of the gastroc muscle were noticed. Conclusion: Functional deficits may not be explained by revision arthroplasty alone, but already exist preoperatively. The gastroc muscle seems to play and especially important role, as its functional deviations are highly correlated with clinical scores. The shown results stress the demand for extensive pre- and postoperative rehabilitation to avoid or at least reduce functional deficits after revision total knee arthroplasty

Aim: To ascertain the accuracy of partial weight bearing. Method: 6 healthy volunteers with a below knee plaster cast, 10 patients with uncemented hip replacements and 12 patients with lower limb fractures were trained to partial weight bear. They were asked to place the affected leg on a bathroom scale and to press on it till the prescribed limit. This process was repeated till the subject formed a mental image of the amount of load they must put through the limb. The ability to partial weight bear was tested in a gait lab by making them walk on a walkway incorporating a Bertec force platform. Exact magnitude of weight bearing was calculated from the vertical ground reaction forces produced. Results: 4 out of 6 volunteers exerted mean weight of 20.3 kg above and the remaining 2 exerted 5.6 kg below that prescribed. Of the 22 patients, 19 exerted mean weight of 24.3 kg above and 3 patients exerted mean weight of 7.5 kg below that prescribed. As per Spearmanñs rank correlation test, the relationship between the prescribed weight bearing and the actual weight bearing was non-signiþcant (p=0.399) i.e., there is little relationship between the prescribed and actual weight bearing. Conclusions: Neither patients nor healthy volunteers could partial weight bear to the extent required. They were either above or below the prescribed level of partial weight bearing. Current method of teaching partial weight bearing is inaccurate and has poor reproducibility. Such methods use static loading situations whereas walking is a dynamic activity. An inexpensive, easy to use, dynamic device is required to train patients to partial weight bear

Introduction. Although Total Knee Arthroplasty (TKA) has been shown to correct abnormal frontal plane knee biomechanics, little is known about this effect beyond 6 months. The purpose of this study was to compare sequentially the knee adduction moment during level-walking before and after TKA in varus knees. We hypothesized that adduction moment would diminish after TKA proportionate to the tibio-femoral realignment in degrees. Methods. Fifteen patients (17 TKA's) with varus knees were prospectively enrolled and gait analysis performed prior to, 6 months and 1 year following TKA. Reflective markers were placed on the lower extremity and motion data collected using six infrared cameras (Qtrac, Qualysis). Ground reaction forces were recorded with a multicomponent force plate (Kistler). A repeated-measures ANOVA was used to compare changes in the peak adduction moment and peak dynamic varus angle over time. Results. TKA corrected static knee alignment from 2.2 (2.5) degrees varus to 3.5 (2.7) degrees valgus (P < 0.001). Peak dynamic varus angle during gait was reduced from 9.7 (6.5) degrees to 3.6 (5.8) degrees at 6 months and 5.2 (7.6) degrees at 1 year (Main Effect of Time; P=0.005). Peak adduction moment was significantly reduced to 85% of pre-op level at 6 months (P=0.037) but subsequently increased to 94% of pre-op level at 1 year (P = 0.539). Post-op improvement in static alignment did not correlate with the change in adduction moment at any follow-up period (P = 0.671). A significant correlation was found between the increase in dynamic varus angle and the subsequent increase in adduction moment from the six-month to the one-year follow-up (P = 0.008). Conclusion. TKA improves knee adduction moment at 6 months but this effect is lost with time (1 year). Despite restoration of static knee alignment and soft tissue balance, loading conditions at medial compartment remain high, predisposing to medial polyethylene wear, a finding reported by retrieval studies

For a proper rehabilitation of the knee following knee arthroplasty, a comprehensive understanding of bony and soft tissue structures and their effects on biomechanics of the individual patient is essential. Musculoskeletal models have the potential, however, to predict dynamic interactions of the knee joint and provide knowledge to the understanding of knee biomechanics. Our goal was to develop a generic musculoskeletal knee model which is adaptable to subject-specific situations and to use in-vivo kinematic measurements obtained under full-weight bearing condition in a previous Upright-MRI study of our group for a proper validation of the simulation results. The simulation model has been developed and adapted to subject-specific cases in the multi-body simulation software AnyBody. For the implementation of the knee model a reference model from the AnyBody Repository was adapted for the present issue. The standard hinge joint was replaced with a new complex knee joint with 6DoF. The 3D bone geometries were obtained from an optimized MRI scan and then post-processed in the mesh processing software MeshLab. A homogenous dilation of 3 mm was generated for each bone and used as articulating surfaces. The anatomical locations of viscoelastic ligaments and muscle attachments were determined based on literature data. Ligament parameters, such as elongation and slack length, were adjusted in a calibration study in two leg stance as reference position. For the subject-specific adaptation a general scaling law, taking segment length, mass and fat into account, was used for a global scaling. The scaling law was further modified to allow a detailed adaption of the knee region, e.g. align the subject-specific knee morphology (including ligament and muscle attachments) in the reference model. The boundary conditions were solely described by analytical methods since body motion (apart from the knee region) or force data were not recorded in the Upright-MRI study. Ground reaction forces have been predicted and a single leg deep knee bend was simulated by kinematic constraints, such as that the centre of mass is positioned above the ankle joint. The contact forces in the knee joint were computed using the force dependent kinematic algorithm. Finally, the simulation model was adapted to three subjects, a single leg deep knee bend was simulated, subject-specific kinematics were recorded and then compared to their corresponding in-vivo kinematic measurements data. We were able to simulate the whole group of subjects over the complete range of motion. The tibiofemoral kinematics of three subjects could be simulated showing the overall trend correctly, whereas absolute values partially differ. In conclusion, the presented simulation model is highly adaptable to an individual situation and seems to be suitable to approximate subject-specific knee kinematics without consideration of cartilage and menisci. The model enables sensitivity analyses regarding changes in patient specific knee kinematics following e.g. surgical interventions on bone or soft tissue as well as related to the design and placement of partial or total knee joint replacement. However, model optimisation, a higher case number, sensitivity analyses of selected parameters and a semi-automation of the workflow are parts of our ongoing work

Purpose: Adults with knee osteoarthritis (OA) show biomechanical changes in gait which may be linked to the quadriceps weakness often associated with knee OA. The purpose of this study was to mimic the effect of quadriceps weakness by inducing fatigue to determine if this produced gait characteristics similar to those present in knee OA. Method: Sixteen healthy, sedentary female subjects between the ages of 19 and 35 years participated. Subjects were randomly assigned to perform a quadriceps-fatiguing protocol using a CybexTM isokinetic dynamometer (n=9) or a resting control group (n=7). Gait was evaluated before and after the rest or the fatiguing protocol. Infrared and virtual markers were used to record the locations of 16 anatomical landmarks. Marker position was recorded using an Optotrak motion capture system. An AMTI force plate collected ground reaction forces. Joint kinematics and kinetics were calculated using standard techniques. Maximum, minimum and time to peak were calculated for knee flexion angle, and the flexion, adduction and rotation moments during stance. A 2-factor (group, pre-post) mixed model ANOVA was used to test main effects and interactions (alpha = 0.05). Post hoc Bonferroni testing (alphaadj=0.0125) was used to determine pair wise differences. Results: The two groups were statistically similar at baseline (p> 0.05) in terms of their age, mass, height, strength, and self-selected walking velocity. The fatigue protocol resulted in a 49 ± 12% decrease in peak knee extensor torque. The statistical results showed that knee flexion and external rotation moments decreased, the time to peak knee flexion angle increased, and the minimum knee adduction moment increased from pre-test to post-test in the fatigued group (p< 0.05). Conclusion: Induced quadriceps fatigue alters kinematic and kinetic gait parameters. The changes are consistent with the gait characteristics observed in patients with knee OA and imply a change in joint motion and loading. These results provide preliminary evidence of a direct link between quadriceps weakness and the mechanical environment of the knee joint. This may be useful in developing more specific management programs for knee OA

Telemetric knee implants have provided invaluable insight into the forces occurring in the knee during various activities. However, due to the high amount of cost involved only a few of them have been developed. Mathematical modeling of the knee provides an alternative that can be easily applied to study high number of patients. However, in order to ensure accuracy these models need to be validated with in vivo force data. Previously, mathematical models have been developed and validated to study only specific activities. Therefore, the objective of this study was compare the knee force predictions from the same model with that obtained using telemetry for multiple activities. Kinematics of a telemetric patient was collected using fluoroscopy and 2D to 3D image registration for gait, deep knee bend (DKB), chair rise, step up and step down activities. Along with telemetric forces obtained from the implant, synchronized ground reaction forces (GRF) were also collected from a force plate. The relevant kinematics and the GRF were input into an inverse dynamic model of the human leg starting from the foot and ending at the pelvis (Figure 1). All major ligaments and muscles affecting the knee joint were included in the model. The pelvis and the foot were incorporated into the system so as to provide realistic boundary conditions at the hip and the ankle and also to provide reference geometry for the attachment sites of relevant muscles. The muscle redundancy problem was solved using the pseudo-inverse technique which has been shown to automatically optimize muscle forces based on the Crowninshield-Brand cost function. The same model, without any additional changes, was applied for all activities and the predicted knee force results were compared with the data obtained from telemetry. Comparison of the model predictions for the tibiofemoral contact forces with the telemetric implant data revealed a high degree of correlation both in the nature of variation of forces and the magnitudes of the forces obtained. Interestingly, the model predicted forces with a high level of accuracy for activities in which the flexion of the knee do not vary monotonically (increases and decreases or vice-versa) with the activity cycle (gait, step up and step down). During these activities, the difference between the model predictions with the telemetric data was less than 5% (Figure 2). For activities where flexion varies monotonically (either increases or decreases) with activity (DKB and chair rise) the difference between the forces was less than 10% (Figure 3). The results from this study show that inverse dynamic computational models of the knee can be robust enough to predict forces occurring at the knee with a high amount of accuracy for multiple activities. While this study was conducted only on one patient with a telemetric implant, the required inputs to the model are generic enough so that it is applicable for any TKA patient with the mobility to conduct the desired activity. This allows kinetic data to be provided for the improvement of implant design and surgical techniques accessibly and relatively inexpensively

The standard treatment of arthrosis of the ankle joint is arthrodesis while new prosthesis leed to good clinical results. Currently there is much controversial discussion, and knowledge of the fundamentals of biomechanics is becoming ever more important. Ten macroscopically and roentgenographically normal foot specimens were tested comparing tibio-talar arthodesis vs. nativ situation on a kinematic gait simulator. The stance- phase of normal walking gait was simulated from heel-contact to toe-off. Ground reaction forces were simulated by a tilting angle- and force-controlled translation stage upon which a pressure measuring platform was mounted. Force was applied to the tendons of the foot flexor and extensor muscle groups by cables attached to an additional set of six force-controlled hydraulic cylinders. Tibial rotation was produced by an electrical servo motor. The change after arthrodesis was a varying degree of relocation of average force and maximum pressure from the lateral onto the medial column of the foot; the increase force on talonavicular joint and decrease on calcaneocuboid joint is statistically significant. The average force increased from native 66.7N to 80.8N upon arthrodesis in the talonavicular joint and decreased in the calcaneocuboid joint from 71.9N to 58.5N. Peak pressure increased from 3728kPa to 4552kPa in talonavicular joint and decreased in calcaneocuboid joint from 3809kPa to 3627kPa. After arthrodesis, we measured inconsistent changes in Chopart joint. On some feet, the changes in stress were slight, but on majority, relocation of force and peak pressure was significant. The result was a change in the function of Chopart joint with increased extension load on talonavicular joint at time of highest joint load during push-off. These in vitro observations explain the clinical observations that have followed ankle arthrodesis. For one, there are reports on tibiotalar arthrodesis patients who are largely mobile and free of complaints, which correlates with the observation that not all preparations indicate a clear relocation of force and intraarticular peak pressure onto the talonavicular joint. In these cases, the ability of strong muscular plantar flexion could explain a good functional result. In contrast, and in addition to subtalar joint degeneration, arthroses in the talonavicular joint have been frequently observed following tibiotalar arthrodeses. The relocation of both force and intraarticular peak pressure onto the medial column of the foot in the majority of preparations explain the degeneration on the extensor side of the joint with osteophyte formation impressively

Aim: Surgical treatment for idiopathic clubfeet aims to realign the foot and allow plantigrade weight bearing with adequate joint motion. In spite of satisfying clinical and radiological results for both the physician and the parents shortly after the operation, deterioration may occur years after the surgery. The aim of this study was to evaluate gait characteristics of children with surgically treated unilateral clubfoot and had good clinical outcome. Methods: Twelve children (mean age 5.9±2.3 years (4–9)) with surgically treated unilateral clubfoot before age one and twelve age matched healthy children were included in the study. Foot length, calf circumference, ankle range of motion and radiographic measurements were recorded. Quantitative gait data was collected with the Vicon 370 (Oxford Metrics, Oxford, UK). Two force plates (Bertec, Colombus, Ohio, USA) were used for kinetic analysis. All time-distance (walking velocity, cadence, step time, step length, double support time), kinematic (joint rotation angles of pelvis, hip, knee and ankle in sagittal, coronal and transverse planes) and kinetic (ground reaction forces, moments and powers of hip, knee and ankle) data were processed using Vicon Clinical Manager software package. Results: Foot length of the operated side was shorter than the unaffected side but the difference was not significant (p> 0.05). Calf circumference and ankle range of motion were significantly less than the unaffected side (p< 0.05). Quantitative gait data revealed that children with clubfoot had slower walking velocity (0.75±0.25 versus 1.02±0.18 m/sec, p=0.001), shorter stride length (0.72±0.23 versus 0.91±0.05 meters, p=0.001) and less ankle plantar flexor moment (0.73±0.22 versus 0.88±0.11 m/sec, p=0.007) than healthy children. Unaffected side showed increased pelvic excursions and medio-lateral ground reaction forces as well as decreased ankle and hip motion in sagittal plane. Conclusion: We detect various deviations in gait parameters even in so called well treated patients according to radiological and clinical criteria. Alterations in the unaffected foot may be the result of the subclinical involvement of the unaffected foot by disease as well as the compensatory mechanisms. These gait deviations may lead long-term morbidity later in adulthood

While previous studies have highlighted possible aetiological factors for adolescent idiopathic scoliosis (AIS), research employing gait measurements have demonstrated asymmetries in the ground reaction forces, suggesting a relationship between these asymmetries, neurological dysfunction and spinal deformity. Furthermore, investigations have indicated that the kinematic differences in various body segments may be a major contributing factor. This investigation, which formed part of a wider comprehensive study, was aimed at identifying asymmetries in lower limb kinematics and pelvic and back movements during level walking in scoliotic subjects that could be related to the spinal deformity. Additionally, the study examined the time domain parameters of the various components of ground reaction force together with the centre of pressure (CoP) pattern, assessed during level walking, which could be related to the spinal deformity. Although previous studies indicate that force platforms provide good estimation of the static balance of individuals, there remains a paucity of information on dynamic balance during walking. In addition, while research has documented the use of CoP and net joint moments in gait assessment and have assessed centre of mass (CoM)–CoP distance relationships in clinical conditions, there is little information relating to the moments about CoM. Hence, one of the objectives of the present study was to assess and establish the asymmetry in the CoP pattern and moments about CoM during level walking and its relationship to spinal deformity. The investigation employed a six camera movement analysis system and a strain gauge force platform in order to estimate time domain kinetic parameters and other kinematic parameters in the lower extremities, pelvis and back. 16 patients with varying degrees of deformity, scheduled for surgery within a week took part in the study. The data for the right and left foot was collected from separate trials of normal walking. CoP was then estimated using the force and moment components from the force platform. Results indicate differences across the subjects depending on the laterality of the major curve. There is an evidence of a relationship between the medio-lateral direction CoP and the laterality of both the main and compensation curves. This is not evident in the anterior-posterior direction. Similar results were recorded for moments about CoM. Subjects with a higher left compensation curve had greater deviation to the left. Furthermore, the results show that the variables identified in this study can be applied to initial screening and surgical evaluation of spinal deformities such as scoliosis. Further studies are being undertaken to validate these findings

Mathematical modeling provides an efficient and easily reproducible method for the determination of joint forces under in vivo conditions. The need for these new modeling methodologies is needed in the lumbar spine, where an understanding of the loading environment is limited. Few studies using telemetry and pressure sensors have directly measured forces borne by the spine; however, only a very small number of subjects have been studied and experimental conditions were not ideal for giving total forces acting in the spine. As a result, alternative approaches for investigating the lumbar spine across different clinical pathologies are essential. Therefore, the objective of this study was to develop of an inverse dynamic mathematical model for theoretically deriving in-vivo contact forces as well as musculotendon forces in patients having healthy, symptomatic, pathological and post-operative conditions of the lumbar spine. Fluoroscopy and 3D-to-2D image registration were used to obtain kinematic data for patients performing flexion-extension of the lumbar spine. This data served as input into the multi-body, mathematical model. Other inputs included patient-specific bone geometries, recreated from CT, and ground reaction forces. Vertebral bones were represented as rigid bodies, while massless frames symbolized the lower body, torso and abdominal wall (Figure 1). In addition, ligaments were selected and modeled as linear spring elements, along with relevant muscle groups. The muscles were divided into individual fascicles and solved for using a pseudo-inverse algorithm which enabled for decoupling of the derived resultant torques defining the desired kinetic trajectory for the muscles. The largest average contact forces in the model for healthy, symptomatic, pathological, and post-operative lumbar spine conditions occurred at maximum flexion at L4L5 level and were predicted to be 2.47 BW, 2.33 BW, 3.08 BW, and 1.60 BW, respectively. The FE rotation associated with these theoretical force values was 43.0° in healthy, 40.5° in symptomatic, 44.4° in pathological, and 22.8° in post-operative patients. The smallest forces occurred as patients approached the upright, standing position, followed by slight increases in the contact force at full extension. The theoretically derived muscle forces exhibited similar contributory force profiles in the intact spine (healthy, symptomatic, and pathologic); however, surgically implanted spines experienced an increase in the contribution of the external oblique muscles accompanied with decreased slope gradients in the muscle force profiles (Figure 2). These altered force patterns may be associated with the decrease in the predicted contact forces in post-operative patients. In addition, the decreased slope gradients in surgically implanted patients corresponds with the observed difficulty of performing the prescribed motion, possibly due to improper muscle firing, thereby leading to slower motion cycles and less ranges-of-motion. On the contrary, patients having an intact spine performed the activity at a faster speed and to greater ranges-of-motion, which corresponds with the higher contact forces derived in the model. In conclusion, this research study presented the development of a mathematical modeling approach utilizing patient-specific data to generate theoretical in-vivo joint forces. This may serve to help progress the understanding for the kinetic characteristics of the native and surgically implanted lumbar spine

Purpose: Femoroacetabular impingement (FAI) is recognized as a pathomechanical process that leads to hip osteoarthritis (OA). Past research has been focused on treatments for FAI; however, few studies have been done to link FAI with the progression of OA. It is hypothesized that elevated mechanical stimuli could provoke bone remodeling in the subchondral bone and articulating surfaces due to cam FAI (aspherical head-neck deformity), which would accelerate the progression of OA. Using finite element analysis (FEA), the aim is to compare healthy hips to hips with cam FAI – investigating the mechanical stimuli effect of FAI towards OA. Method: Net joint reaction forces were obtained from joint kinematics, kinetics, and by inverse dynamics calculation for a dynamic squat motion of a control subject and a cam FAI patient (both males with comparable age, BMI, and femur lengths). CT scans were acquired from both subjects. Data slices were compiled using 3D-DOCTOR (Able Software Corp, MA) to form a 3D model with slice thickness calibrated at 1.25mm in the superior-inferior axis. ANSYS (ANSYS, PA) software was used for FEA. The femur models were given quadrilateral shell elements and modeled as linear elastic orthotropic materials. The ground reaction forces were applied to the femur models, simulating dynamic loads, using boundary conditions specific to hip loading. Von Mises stresses were determined to examine stress concentrations and adverse loading conditions. Strain energy distributions were determined to examine the effect of stimuli on the initiation and rate of bone remodeling. Results: At the maximum squat-depth, the FEA results demonstrated that the net forces acting on the FAI hip produced high mechanical stimuli regions around the head and neck. The highest stress concentration (590 MPa) was located at the anterosuperior head-neck junction, where cam FAI is most prominent. For the control hip, stresses were significantly lower (maximum of 151 MPa) and dissipated around the head. For both the FAI and the control hip, the maximum strain energy concentrations were seen at the superior portion of the head (4.725 kJ vs. 2.192 kJ for FAI vs. control hip respectively). Conclusion: The increase in mechanical stimuli can be due to the loading configurations as well as to the abnormal geometry of the cam deformity. Assuming that the strain energy density (SED) and its rate is linearly proportional to the rate of bone turnover, based on a recent semi-mechanistic bone remodeling theory, a higher rate of bone turnover is expected in the FAI than in a normal hip. Depending on the level and rate of SED, the rate of bone remodeling will vary in order to provide a new homeostatic configuration. The next-step analysis, examining the mechanical stimuli in the acetabulum and its cartilage, is currently in progress. This would provide useful information about the possible locations of OA initiation and establish a link between FAI with cartilage degeneration

Tibial fractures represent a heterogeneous group of fractures that are difficult to treat and vary widely in their time to union. Judging when it is safe to remove an external fixator or plaster cast requires clinical and radiological assessments both of which are subjective. Any errors in determining when a fracture has healed can lead to a prolonged treatment time or to refracture. Many methods have been employed to attempt to define clinical union in an objective manner including ultrasound, DEXA scanning, vibration analysis, and fracture stiffness measurements. Stiffness measurements are however time consuming to perform, of debatable clinical significance, and applicable only to fractures treated with external fixators. It has been previously observed. 1,. 2. that weight bearing increases with time post-fracture. It has also been suggested. 3. that the ability of a patient to weight bear on the fractured limb is controlled by a biofeedback mechanism of biological self-control of fracture site strain that will be related to the stiffness of the fracture. We hypothesised that weight-bearing will be closely related to fracture healing and could be used as an alternative measure of healing where other objective measures of healing are not available or are impracticable. A group of ten patients with tibial fractures treated by external fixation were studied. Using a Kistler force plate set into the floor, ground reaction forces for both lower limbs (fractured and non-fractured) were measured during normal walking at three weekly intervals. Concurrent fracture stiffness measurements were made using the Orthofix Orthometer. In 8 patients who made good recoveries, the fixator was removed between 15–20 weeks post injury when the fracture stiffness had reached a minimum of 15 Nm/deg. Weight-bearing through the injured leg was seen to approach 90% of that through the uninjured leg in the 3 weeks prior to fixator removal. Two patients with delayed union achieved weight bearing of less than 40% of normal between 15–20 weeks. They also demonstrated low values of fracture stiffness (< 5 Nm/deg.) and subsequently required operative intervention to achieve union. In this small study of 10 patients, weight bearing appears to correlate well with clinical union. It is quicker and easier to assess than stiffness and potentially has relevance to other fixation methods. We are continuing these measurements on conservatively treated, intra-medullary nailed, and externally fixed tibial fractures

Introduction: The regulation of balance during upright standing involves continuous muscular activity, associated with body sway. In single stance standing, the base of support is narrower compared to double stance, resulting in an increased body sway and emphasizing the role of individual muscles in regulating the sway motion. In this study, we investigated the effect of Tibialis Anterior (TA) fatigue on body sway during standing on one leg on ten able-bodied subjects. Methods: Foot ground reaction forces, goniometry of the ankle joint, and EMG of the TA were all measured simultaneously in two tests. Each test lasted 30 sec. During which the subjects were required to stand as still as possible with their dominant leg on a forceplate and the contralateral knee flexed upward at 90 deg approximately, and their hands resting on their waists. The tests were separated by a 4 min isotonic fatiguing effort of the TA, indicated by a significant decrease of the mean power frequency (MPF). Results: The EGM root mean square (RMS) started off at 45% MVC but, towards the end of the effort, significantly increased to 52% MVC, the latter determined in non-fatigue condition. Compared to the non-fatigue state, the following significant (p< 0.05) sway changes took place in the fatigue state: force RMS increased from 2.61 to 3.90 N and from 3.77 to 5.01 N in the mediolateral (ML) and vertical directions, respectively. The center of pressure (CoP). RMS in the ML direction increased from 0.57 to 0.68 cm. The EMG RMS in the TA increased from 4.15 to 5.58 and the MPF decreased from 107.6 to 96.7 Hz in the fatigued state. Discussion: An interesting finding was revealed by comparing the variations of the ankle angle to those of the center of pressure in the anterior-posterior direction taking place during standing. During the non-fatigue test the CoP moved gradually posteriorly, while the goniometer indicated an ankle change towards dorsiflexion. These obviously two opposing trends necessitate compensatory angular adjustments at the knee and/or hip joints. However, during the fatigue test, the posterior excursion of the CoP was accompanied by a consistent change in the ankle, towards plantar flexion. This seems to suggest that in the fatigue state the redundancy of the musculoskeletal system is reduced, increasing the degree of correction between ankle angle and CoP

INTRODUCTION. A recent PRCT failed to demonstrate superiority of HRA over THA at low speeds. Having seen HRA walk much faster, we wondered if faster walking speed might reveal larger differences. We therefore asked two simple questions:. Does fast or uphill walking have an effect on the observed difference in gait between limbs implanted with one HRA and one THA?. If there is a difference in gait between HRA and THA implanted legs, which is more normal?. METHODS. Participants All patients who had one HR and one THR on the contralateral side were identified from the surgical logs of two expert surgeons. Both surgeons used a posterior approach to the hip and repaired the external rotators on closure. All consenting patients were assessed using the Oxford Hip Score (OHS) to ensure they had good functioning hips. There were 3 females and 6 males in the study group, who had a mean age of 67 (55–76) vs the control group 64 (53–82, p = 0.52). The BMIs of the two groups did not differ significantly (28 v 25, p = 0.11). The mean average oxford score of included patients was 44 (36–48). Radiographs of all subjects were examined to ensure that implanted components were well fixed. The mean time from THA operation to gait assessment was 4 years (1–17 yrs) and that for HRA was 6 years (0.7–10 yrs, p = 0.31). Subjects in this study had a mean TWS of 6.8 km/hr (5–9.5), and a mean TWI of 19 degrees (10–25 degrees). RESULTS. Gait Assessment At Slow And Top Walking Speeds: Mean differences in maximum weight acceptance, maximum push off and impulse correlated strongly with increasing speeds (p < 0.005). At top walking speed however, mean ground reaction forces were greater in the resurfacing group for four out of five of the key GRFs measured. Statistical significance was reached in two out of these variables (p = 0.03). The mean maximum weight acceptance was 71N or 8% greater in the resurfacing group. Gait Assessment Walking On The Flat And Uphill: Once subjects reached their steepest achievable incline, there were more obvious differences between the implanted legs with maximum weight acceptance being significantly greater (p = 0.42) in the HRA implanted limb. When the gait cycles were plotted, the HRA implanted limbs most resembled the normal asymptomatic control group (Graph 1). DISCUSSION. The self determined top walking speeds of subjects were considerably higher than that of other studies testing arthroplasty subjects 6.8 km/hr (5.5–9.5 km/hr). There were strong correlations between the differences in weight acceptance, push- off and impulse as speed increased. Relationship between up hill walking and gait differences: The patient self determined TWI mean average was 19 degrees (10–25 degrees). Testing people at their TWI did reveal a significant difference in favour of the HRA hip (p = 0.02). Hip resurfacing seems to allow for greater levels of function using hill walking and speed walking on a treadmill as a surrogate. There appears to be a functional advantage of having a HRA over THA in patients wishing to return to levels of activity more rigorous than walking at slow speeds on the flat

Introduction: Studies have shown a strong relationship between knee osteoarthritis (OA) and the adduction moment at the knee during gait. Total knee arthroplasty (TKA) is known to improve range of motion and function in patients with severe OA. Examinations of tibial bearing wear suggest that although the static alignment of the joint is restored, the abnormal dynamic loading conditions may still remain. The aim of this study was to compare the pre-op and post-op knee biomechanics during gait in patients undergoing TKA. Methods: Gait analysis was performed on 15 patients with 17 TKA’s (8 women and 7 men, all with pre-op varus knee alignment) prior to, 6 months and 1 year following TKA. Reflective markers were placed on the lower extremity of each patient and motion data were collected at 60 Hz using six infrared cameras (Qtrac, Qualysis). Ground reaction forces were recorded at 960 Hz with a multicomponent force plate (Kistler). The frontal plane knee moment (adduction/abduction) was calculated for each trial using inverse dynamics. Based on the anterior/posterior ground reaction force, the stance phase of each trial was divided into a braking phase and a propulsive phase. The area under the knee adduction moment curve (knee adduction impulse) was calculated for each phase. A repeated-measures (Time x Phase) ANOVA was used to compare changes in the peak knee adduction moment and knee adduction impulse for each phase over time. P-values less than 0.05 were considered significant. Results: Mean knee alignment was 4.75 degrees varus pre-op and 4.25 degrees valgus post-op (P < 0.001). A significant time-by-phase interaction was found for peak adduction moment (P = 0.002) and a nearly significant time-by-phase interaction was found for adduction impulse (P = 0.056). In braking phase, six months after surgery, knee adduction impulse and peak moment decreased 26% and 15% respectively. At one year, however, both increased by 20% and 19% respectively to near pre-op levels. In propulsive phase, knee adduction impulse and moment decreased 34% and 25% respectively at 6 months but only increased by 4% and 11% respectively at one year follow-up. Knee Society and Function scores improved from 50.17 and 61.67 pre-op to 82.08 and 82.50 at 6 months and 88.83 and 85.83 at 1 year post-op (P < 0.001, respectively). Discussion: After TKA, in the breaking phase of gait, the initial improvement in knee adduction impulse and peak knee adduction moment noted at 6 months disappeared completely indicating no improvement in medial compartment loading conditions at 1 year post operatively. The improvement in these parameters during the propulsive phase remained persistent at 1 year although there was some tendency to revert back to pre-operative levels. This would suggest that restoration of anatomic axial alignment and soft tissue balance do not change the medial loading conditions following TKA

The Arthrotic knee is frequently associated with several-pain and loosening of joint function often so important to need a total knee arthroplasty (TKA). Obviously, the aims of a TKA is to obtain no pain and restore a good joint function so to contribute to a good health and a better quality life. To realize ends like these it’s necessary a good selection of the patients first, an adequate preparation for the surgery, correct surgery technique and a specific post-operative rehabilitation until achieving the normal daily activities. In this way clinical biomechanical evaluations can contribute to quantify the achievement of the ends and they can get influence to modulate the “ways” used. Actually the dynamic evaluation more useful and reproducible in the gonartrhosis is the gait analysis. Patients were selected from a group of subjects suffering from advanced gonartrhosis. Exclusion criteria from the study were: bilateral advanced arthrosis; previous surgery at the lower limbs or other disease that could influence the gait pattern. With these criteria a group of 7 males and 2 females, mean age 67,7 years old, participated at the study (after a known consensus). All subjects had clinical evaluation. For the dynamic analysis The knee society evaluation system for arthroplasty was used. The knee stability was evaluated on the frontal and mediolateralaxis. For evaluating the pain entity we used the V.A.S. score at rest and during gait, before and after taking the analgesic drug. In addition standard X-ray of the knees were evaluated. Gait Analysis was performed at the biomechanical laboratory “Let people move” of Perugia (Italy). Subjects walked on a track of 12,5 m., a 3Dcinematic evaluation was performed using the APAS system (ARIEL Dynamics, USA) with 4 high speed video cameras. 15 auto reflexed markers were applied on both lower limbs. The ground reaction forces during the gait were recorded at 500 Hz with Bertec platform placed at the centre of there cording area. At the subjects was asked to make 10 valid trials (5 for right and 5 for left knee). During gait was evaluated the range of motion of ankle and foot too. The mean score obtained with the V.A.S. score for the pain during the first section was 3.3 (range 0–7). After taking the analgesic drug and 20 minutes of rest the range was 0–4 at the sequent trial. The results so obtained said that there’s no difference between the range of motion of the knee after taking the drug on the sagittal plane. In addition, no difference neither between the range of motion of the hip and the ankle, on the sagittal plane after the drug. The mean score obtained with the V.A.S. score for the pain during the first section was 3.3 (range 0–7). After taking the analgesic drug and 20 minutes of rest the range was 0–4 at the sequent trial. The results so obtained said that there’s no difference between the range of motion of the knee after taking the drug on the sagittal plane. In addition, no difference neither between the range of motion of the hip and the ankle, on the sagittal plane after the drug

Accurate in vivo knee joint contact forces are required for joint simulator protocols and finite element models during the development and testing of total knee replacements (Varadarajan et al., 2008.) More accurate knowledge of knee joint contact forces during high flexion activities may lead to safer high flexion implant designs, better understanding of wear mechanisms, and prevention of complications such as aseptic loosening (Komistek et al., 2005.) High flexion is essential for lifestyle and cultural activities in the developing world, as well as in Western cultures, including ground-level tasks and chores, prayer, leisure, and toileting (Hemmerich et al., 2006.) In vivo tibial loads have been reported while kneeling; but only while the subject was at rest in the kneeling position (Zhao et al., 2007), meaning that the loads were submaximal due to muscle relaxation and thigh-calf contact support. The objective of this study was to report the in vivo loads experienced during high flexion activities and to determine how closely the measured axial joint contact forces can be estimated using a simple, non-invasive model. It provides unique data to better interpret non-invasively determined joint-contact forces, as well as directly measured tiobiofemoral joint contact force data for two subjects. Two subjects with instrumented tibial implants performed kneeling and deep knee bend activities. Two sets of trials were carried out for each activity. During the first set, an electromagnetic tracking system and two force plates were used to record lower limb kinematics and ground reaction forces under the foot and under the knee when it was on the ground. In the second set, three-dimensional joint contact forces were directly measured in vivo via instrumented tibial implants (Heinlein et al., 2007.) The measured axial joint contact forces were compared to estimates from a non-invasive joint contact force model (Smith et al., 2008.). The maximum mean axial forces measured during the deep knee bend were 24.2 N/kg at 78.2° flexion (subject A) and 31.1 N/kg at 63.5° flexion (subject B) during the deep knee bend (Figure 1.) During the kneeling activity, the maximum mean axial force measured was 29.8 N/kg at 86.8° flexion (subject B.) While the general shapes of the model-estimated curves were similar to the directly measured curves, the axial joint contact force model underestimated the measured contact forces by 7.0 N/kg on average (Figure 2.) The most likely contributor to this underestimation is the lack of co-contraction in the model. The study protocol was limited in that data could not be simultaneously collected due to electromagnetic interference between the motion tracking system and the inductively powered instrumented tibial component. Because skin-mounted markers were used, kinematics may be affected by skin motion artefacts. Despite these limitations, this study presents valuable information that will advance the development of high flexion total knee replacements. The study provides in vivo measurements and non-invasive estimates of joint contact forces during high flexion activities that can be used for joint simulator protocols and finite element modeling

Introduction: Aseptic loosening at the bone-implant interface of THA acetabular components is a significant cause of implant failure. This loosening has been attributed either to wear particle-induced osteolysis or to the effects of joint fluid-pressure. It may be possible to prevent the loosening of implants by improving fixation between the bone and implant, or promoting the growth of a biological bony seal, in order to prevent the influx of wear particles or pressurized joint fluid. Additionally in revision implants it is important to promote osseointegration in situations where bone stock may be limited. The hypothesis of this study was spraying autologous BMSCs in fibrin glue onto the surface of HA-coated acetabular components would increase bone formation around the implant and improve bone-implant contact. Materials and Methods: Bone marrow was aspirated from the iliac crest of six goats, and BMSCs isolated and expanded in vitro. 10 x 10e6 BMSCs were suspended in reconstituted thrombin pre-operatively. A standard posterior approach was used. The acetabular shell was then coated with 2 ml of fibrin glue, with (n=6) or without 10 x 10e6 autologous BMSCs (n=6), and the acetabular component impacted into position. Antibiotic and analgesic prophylaxes were carried out. All animals were weight bearing within 48 hours post-operatively. Walking and ground reaction forces were assessed pre-operatively, as well as 6 and 12 weeks post-operatively. Results were expressed as a percentage of force transmitted through the right leg versus the left leg. After 12 weeks, the acetabulae were retrieved, and processed for histology. The percentage of new bone around the cups was measured within 5 radial zones, using image analysis. Bone-implant contact was also analysed between the new bone and implant surface. Mann Whitney U test was used to show statistical significance. Results: New bone formation in Zone 5 showed a significant increase in the BMSC group (71.97±10.91%), when compared to the controls (23.85±15.13%, p=0.028). The other zones did not show a significant difference. Overall new bone growth in the BMSC group was 30% greater than the control group (71.42±8.97% and 54.22±16.56%, respectively, p=0.58). Bone-implant contact was significantly improved in the BMSC group (20.03±4.64%), in contrast to the control group (13.71±8.32%, p=0.027). With regards to the force plate analysis, there was no significant difference in loading between groups at both 6 weeks (Controls-79.74±3.63%, BMSCs-59.39±9.33%, p=0.086) and 12 weeks (Controls-86.0%±2.85%, BMSCs-62.33±5.12%, p=0.055). Discussion and Conclusions: In this study, overall bone growth was greater when cups were treated with BMSCs. Bone-implant contact was significantly improved as well. This study has clinical applications, as using MSCs in fibrin glue promotes a bony seal in contact with the implant which may prevent the migration of particles, or joint fluid, decreasing the likelihood of aseptic loosening of THAs, and improving their longevity. Also, this technique may improve fixation in situations where bone stock is reduced

Aims

The standard of surgical treatment for lower limb neoplasms had been characterized by highly interventional techniques, leading to severe kinetic impairment of the patients and incidences of phantom pain. Rotationplasty had arisen as a potent limb salvage treatment option for young cancer patients with lower limb bone tumours, but its impact on the gait through comparative studies still remains unclear several years after the introduction of the procedure. The aim of this study is to assess the effect of rotationplasty on gait parameters measured by gait analysis compared to healthy individuals.

Aims

Conventional patient-reported surveys, used for patients undergoing total hip arthroplasty (THA), are limited by subjectivity and recall bias. Objective functional evaluation, such as gait analysis, to delineate a patient’s functional capacity and customize surgical interventions, may address these shortcomings. This systematic review endeavours to investigate the application of objective functional assessments in appraising individuals undergoing THA.

Aims

To fully quantify the effect of posterior tibial slope (PTS) angles on joint kinematics and contact mechanics of intact and anterior cruciate ligament-deficient (ACLD) knees during the gait cycle.

Aims

The aim of this study was to assess the functional gain achieved following hip resurfacing arthroplasty (HRA).

Total knee arthroplasty (TKA) is a common surgery to relieve knee pain and increase range of motion due to osteoarthritis (OA) in older patients. Minimally invasive, computer navigated techniques are gaining popularity for knee replacement surgery. These techniques may have potential to provide better functional outcomes over a shorter period of time. Little data exists comparing the early functional recovery of patients following total knee replacement surgery performed using various common approaches. This study compares the functional gait of patients two months after surgery performed using one of four common approaches to determine if differences exist in the immediate recovery. This knowledge will aid surgeons determine the best approach to use when performing surgery. This study was approved by the appropriate Institutional Review Board. Subjects volunteered to participate in the study and signed informed consent prior to testing. Subjects were excluded if the had significant diseases of the other joints of the lower extremity or a diagnosed disorder with gait disturbance. Patients were randomly assigned to receive unilateral primary TKA using standard parapatellar, mini-parapatellar, mini-midvastus, or mini-subvastus approaches. All patients received the same preoperative, perioperative, and postoperative critical pathways and standard orders. All incisions were five inches and all patients and examiners blinded to type of approach. Surgery was performed by one of two fellowship trained orthopedic surgeons. Patients visited the gait laboratory two months after receiving TKA. Motion data was captured using a ten-camera motion capture system (Motion Analysis Corp., Santa Rosa, CA). Three-dimensional force data was recorded using four floor embedded force platforms (AMTI Inc., Watertown, MA). Patients were asked to walk at a self selected speed along a 6.5 metre walkway. A minimum of five good foot strikes for each limb were recorded. Data were collected using EVaRT 5 software (Motion Analysis Corp., Santa Rosa, CA) and analyzed using OrthoTrak 6.2.8 (Motion Analysis Corp., Santa Rosa, CA) and MatLab software (The Mathworks Inc., Natick, MA). Statistical analysis was performed using SPSS 14.0 software (SPSS Inc., Chicago, Il) (α = 0.05). Fifty-two patients (72 ± 6 years) volunteered to participate in the study. The approaches used were: standard parapatellar – 12; mini-parapatellar – 12; mini-midvastus – 14; mini-subvastus – 14. Statistical analysis found no significant differences in any of the variables measured except minimum knee flexion angle during stance (p=.046). The variables measured included the maximum and minimum injured lower limb joint angles in all planes during both stance and swing phase of gait. Also measured were the maximum joint moments in all planes during stance and hip, knee, and ankle powers. Patients who received TKA using the mini-subvastus approach had greater knee extension through much of the single stance phase of the gait cycle which contributed to a lower (but not significant) peak knee flexion moment. These patients also had the highest ground reaction shear forces with higher ankle power absorption at foot strike and generation at push off. Mini-subvastus patients used a higher cadence to walk with a greater velocity then patients who received surgery using the other approaches. The results of this study show only minor differences in gait between patients who have received surgery using the different approaches. The limited numbers of patients in the study and the large variation in outcomes so soon after surgery mean that in most cases the differences that were measured do not reach significant level. This study shows that the surgical approach used to implant the device has no apparent effect on the ability of the person to ambulate following surgery, however further study with increased numbers of patients and observation over a longer period of time will allow a stronger conclusion. The knowledge gained from this and future studies will enable surgeons to make decisions on type of approach based on factors other than expectations of functional outcome

Objectives

The aim of this study was to investigate the biomechanical effect of the anterolateral ligament (ALL), anterior cruciate ligament (ACL), or both ALL and ACL on kinematics under dynamic loading conditions using dynamic simulation subject-specific knee models.

Aims

Vertebrates have adapted to life on Earth and its constant gravitational field, which exerts load on the body and influences the structure and function of tissues. While the effects of microgravity on muscle and bone homeostasis are well described, with sarcopenia and osteoporosis observed in astronauts returning from space, the effects of shorter exposures to increased gravitational fields are less well characterized. We aimed to test how hypergravity affects early cartilage and skeletal development in a zebrafish model.

Objectives

The aim of the current study was to analyse the effects of posterior cruciate ligament (PCL) deficiency on forces of the posterolateral corner structure and on tibiofemoral (TF) and patellofemoral (PF) contact force under dynamic-loading conditions.

Objectives

Osteoporosis is a metabolic disease resulting in progressive loss of bone mass as measured by bone mineral density (BMD). Physical exercise has a positive effect on increasing or maintaining BMD in postmenopausal women. The contribution of exercise to the regulation of osteogenesis in osteoblasts remains unclear. We therefore investigated the effect of exercise on osteoblasts in ovariectomized mice.

Aims

The outcome of total knee arthroplasty (TKA) is not always satisfactory. The purpose of this study was to identify satisfaction and biomechanical features characterising the gait of patients who had undergone TKA with either an anatomical single radius design or a medial pivot design. We hypothesised that the latter would provide superior function.

Aim

It has been suggested that the use of a pilot-hole may reduce the risk of fracture to the lateral cortex. Therefore the purpose of this study was to determine the effect of a pilot hole on the strains and occurrence of fractures at the lateral cortex during the opening of a high tibial osteotomy (HTO) and post-surgery loading.

This study investigates the use of porous biphasic ceramics as graft extenders in impaction grafting of the femur during revision hip surgery.

Impaction grafting of the femur was performed in four groups of sheep. Group one received pure allograft, group two 50% allograft and 50% BoneSave, group three 50% allograft and 50% BoneSave type 2 and group four 10% allograft and 90% BoneSave as the graft material. Function was assessed using an index of pre- and post-operative peak vertical ground reaction force ratios. Changes in bone mineral density were measured by dual energy X ray absorptiometry (DEXA) scanning. Loosening and subsidence were assessed radiographically and by histological examination of the explanted specimens.

There was no statistically significant difference between the four groups after 18 months of unrestricted functional loading for all outcome measures.

The Jaipur foot was developed for barefoot amputees by Professor P. K. Sethi. He used local artisans and readily available materials. The prosthesis was cheap and could be made in one hour. It enabled amputees to work in rural conditions, muddy and wet fields and to climb trees. It has been widely used in India, South East Asia and Africa, where local variations to the design have now been made.

It has been suggested that extracorporeal shockwave therapy is a safe and effective treatment for pain relief from recalcitrant plantar fasciopathy (PF). However, the changes in gait and associated biomechanical parameters have not been well characterised. We recruited 12 female patients with recalcitrant PF who had a mean age of 59 years (50 to 70) and mean body mass index of 25 kg/m² (22 to 30). The patients reported a mean duration of symptoms of 9.3 months (6 to 15). Shockwave therapy consisting of 1500 impulses (energy flux density 0.26 mJ/mm²) was applied for three sessions, each three weeks apart. A pain visual analogue scale (VAS) rating, plantar pressure assessment and motion analysis were carried out before and nine weeks after first shock wave therapy. It was demonstrated that patients increased their walking velocity and cadence as well indicating a decrease in pain after shockwave therapy. In the symptomatic foot, the peak contact pressure over the forefoot increased and the contact area over the digits decreased. The total foot impulse also decreased as did stance duration. The duration the centre of pressure remained in the hindfoot increased in the symptomatic foot after shockwave therapy. The differences in centre of pressure trajectory at baseline decreased at final follow-up. In conclusion, shockwave therapy not only decreased the pain VAS rating but also improved the gait parameters of the symptomatic foot in PF patients.

Cite this article: Bone Joint J 2013;95-B:1088–93.

A total of 25 children (37 legs and 51 segments) with coronal plane deformities around the knee were treated with the extraperiosteal application of a flexible two-hole plate and screws. The mean age was 11.6 years (5.5 to 14.9), the median angle of deformity treated was 8.3° and mean time for correction was 16.1 months (7 to 37.3). There was a mean rate of correction of 0.7° per month in the femur (0.3° to 1.5°), 0.5° per month in the tibia (0.1° to 0.9°) and 1.2° per month (0.1° to 2.2°) if femur and tibia were treated concurrently. Correction was faster if the child was under 10 years of age (p = 0.05). The patients were reviewed between six and 32 months after plate removal. One child had a rebound deformity but no permanent physeal tethers were encountered.

The guided growth technique, as performed using a flexible titanium plate, is simple and safe for treating periarticular deformities of the leg.

Hallux rigidus was first described in 1887. Many aetiological factors have been postulated, but none has been supported by scientific evidence. We have examined the static and dynamic imbalances in the first metatarsophalangeal joint which we postulated could be the cause of this condition. We performed a finite-element analysis study on a male subject and calculated a mathematical model of the joint when subjected to both normal and abnormal physiological loads.

The results gave statistically significant evidence for an increase in tension of the plantar fascia as the cause of abnormal stress on the articular cartilage rather than mismatch of the articular surfaces or subclinical muscle contractures. Our study indicated a clinical potential cause of hallux rigidus and challenged the many aetiological theories. It could influence the choice of surgical procedure for the treatment of early grades of hallux rigidus.