Summary Statment

The dual-mobility cup seems to bring more stability without changing the gait pattern.

INTRODUCTION

Mobile-bearing knee prostheses have been designed in order to provide less constrained knee kinematics compared to fixed-bearing prosthesis. Currently, there is no evidence to confirm the superiority of either of the two implants with regard to walking performances. It has been shown that subjective outcome scores correlate poorly with real walking performance and it has been recommended to obtain an additional assessment of walking ability with objective gait analysis.

Purpose of the study: Reconstruction of the anterior cruciate ligament (ACL) controls laxity but does not enable restoration of strictly normal 3D kinematics. The purpose of this study was to compare the kinematics of the pathological knee with that of the healthy knee after ACL plasty. This study applied a new ambulatory system using miniature captors.

Material and method: Five patients with an isolated injury of the ACL participated in this study. The patients were assessed after injury (T1), at five months (T2), and at 14 months (T3) after surgery. The assessment included laxity (KT-1000), the IKDC score and the Lysholm score. The 3D angles of the knees were measured when walking 30 m on flat ground using a system composed of to small inertia units (3D accelerometer and 3D gyroscope) and a portable recorder. Functional settings were optimised and validating to ensure easy precise measurement of the 3D angles. Symmetry of the two knees was quantified using a symmetry index (SI) (difference in amplitude normalised in relation to mean amplitude) and the correlation coefficient CC.

Results: Clinical indicators improved during the follow-up (IKDC T1: 3C, 2C; T2: 5B; T3: 2A, 3B; subjective IKD: 53–95; Lysholm 67–96). Mean laxity improved from 8.6m to 2.5 mm. The gait analysis showed increased symmetry in terms of amplitude for flexion-extension (SI: −17% at T1, −1% at T2, 1% at T3), and an increase in symmetry in terms of the rotation signature (CC: 0.16 at T1, 0.99 at T2, 0.99 at T3). There was no trend to varus-valgus.

Discussion: This study demonstrates the clinical application of the new ambulatory system for measuring 3D angles of the knee joint. Joint symmetry increased after ACL plasty but still showed some perturbation at 14 months. The results observed here are in agreement with the literature. Other patients and other types of gait are being analysed.

Conclusion: This portable system allows gait analysis outside the laboratory, before and after ACL injury. It is very useful for follow-up after surgery.

Introduction: A new ultra congruent, postero-stabilized total knee arthroplasty (TKA) with a mobile bearing, the FIRST knee prosthesis (Free Insert in Rotation Stabilized in Translation, Symbios SA), was designed and expected to significantly reduce polyethylene wear, to improve the range of motion and the overall stability of the knee while ensuring a physiological ligament balance. Gait analysis has proven to give really objective outcome parameters after lower limb surgery. The goal of our study was to compare the subjective and really objective results of this new TKA with two other widespread models of TKA.

Methods: A clinical prospective monocentric cohort study of 100 consecutive patients (47–88 yrs) undergoing a FIRST TKA for primary osteoarthritis is currently being done. Pre- and post-operative follow-ups (6 weeks, 4 months and 1 year) were done with well-recognized subjective evaluations (EQ-5D and WOMAC scores) and semi-objective questionnaires (KSS score and radiography evaluation) as well as with a really objective evaluation using gait parameters from 6 walking trials, performed at different speeds (slow, normal and fast) with an ambulatory gait analysis system (Physilog^®, BioAGM CH). The outcomes of the first 32 new TKA after one year of follow-up were compared to the results after 1 year of a randomized controlled clinical trial comparing 29 NexGen^® postero-stabilized TKA (Zimmer Inc) with a fixed bearing and 26 NexGen^® TKA with a mobile bearing using the same methods.

Results: Subjective and semi-objective results were similar for the three types of TKA. As for the really objective parameters, the gait cycle time of the FIRST TKA was statistically significantly shorter at normal speed of walk, as well as double-support periods, as compared to both standard models. The extension (in terms of range of motion when walking) of the operated knee was significantly improved for all three types of walk in favour of the FIRST TKAs compared to both NexGen TKAs. The normal walking speed was significantly higher with faster swing speed and stride lengths for the new TKA. Significantly better coordination scores were observed at normal walking speed for the FIRST TKA as compared to the fixed-bearing TKAs.

Conclusion: The FIRST TKAs showed statistically significantly better objective outcomes in terms of gait after one year of follow-up with similar subjective and semi-objective results in comparison with widespread TKA designs. These encouraging short-terms results will have to be confirmed at a 5 years follow-up of the FIRST TKAs.

In many fields, such as orthopedics and rehabilitation, measurement of segment orientation or three-dimensional (3D) joint rotation is highly required. However, even if laboratory systems (e.g., optical-based tracker) are enough accurate for human movement measurement, they have some limitations (e.g., cost, complexity, capture volume) that exclude their uses in routine practice.

Recently, our group proposed an original system fusing a low level magnetic tracker (Minuteman®, Polhemus, USA) and 3D gyroscopes (Physilog®, BioAGM, CH) to measure segments orientation. These complementary devices were selected with the aim to provide real time orientation in clinical environment and without restriction on the acquisition duration. The objective of the present study was to assess the performances of this new system in routine clinical applications.

For this evaluation, five healthy young men were enrolled and the orientation of their left thigh was considered. They were asked to perform two times a long scenario (14 min) which included various postures (standing, sitting and lying) and activities (e.g., walking and stairs climbing). These activities were realized both, in the vicinity and far from the magnetic source. Additionally, different metallic objects were inserted and moved in the capture volume to simulate assisted clinical applications. An optical motion capture system (VICON®, UK) was used as reference.

In the absence of magnetic distortion and independently of the activity, we obtained a RMS orientation error of 1.2°. Generally, during distortion periods we obtained a slow growing orientation error of about 0.1°/s whatever the activity.

In conclusion, the proposed system provided an accurate and real-time measurement of orientation in a large capture volume over a long duration. Furthermore the system performances were tested in an environment including representative distortions of routine clinical uses. In combination with a functional calibration, this system was very promising for routine measurements of 3D joint rotations.

Recently, many mathematical descriptors were proposed to quantify 3D motions of the foot and ankle complex. However, since the ranges of rotation in foot joints are rather small, the reliability of these kinematic assessments is questionable. Particularly, achievement of acceptable results for clinical decision makings demands to extract repeatable features. In this study, repeatability of kinematics assessment of multi-segment foot by means of different mathematical descriptors was investigated.

25 tiny markers were mounted on dominant anatomical landmarks of the foot and ankle complex. Six young healthy subjects were asked to walk over a forceplate surrounded by six infra-red cameras. Marker trajectories were captured during one stance phase and several trials per subject were recorded. Foot and ankle complex was considered as six rigid segments:

Shank,

3D angles between each pair of segments (i.e., 1~2, 2~3, 3~4, 3~5 and 4~6) were calculated based on three common mathematical descriptors:

helical angle,

Then, the coefficient of multiple correlations (CMC) was used to estimate the degree of similarity among joint angle patterns for intra-subject and inter-subjects trials.

It was observed that the three angle calculation methods had comparable repeatability for both intra-subject and inter-subjects kinematics. No significant difference among their repeatability was noticed. Most of angles showed good pattern repeatability intra-subject and acceptable pattern repeatability inter-subjects. In conclusion, all three calculation methods for foot joint angles can be reliably applied. Further studies enrolling patients with foot and ankle pathology are necessary to investigate the relevance of these measurements for clinical evaluations.

The FIRST knee prosthesis (Free Insert in Rotation Stabilized in Translation, Symbios SA) is a new ultra congruent, postero-stabilized total knee arthroplasty (TKA) with a mobile bearing expected to reduce significantly polyethylene wear, to improve the range of motion and the overall stability of the knee while ensuring a physiological ligament balance. We compared subjective and really objective results of this new TKA with two other widespread models of TKA.

A clinical prospective monocentric cohort study of 100 consecutive patients (47–88 yrs) undergoing a FIRST TKA for primary osteoarthritis is currently being done. Pre- and post-operative follow-ups (6 weeks, 4,5 months and 1 year) are done with well-recognized subjective evaluations (EQ-5D and WOMAC scores) and semi-objective questionnaires (KSS score and radiography evaluation) as well as with a really objective evaluation using gait parameters from 6 walking trials, performed at different speeds with an ambulatory in field gait analysis system (Physilog®, BioAGM CH). The outcomes after one year of follow-up of 32 FIRST TKA are compared to 29 NexGen® postero-stabilized TKA (Zimmer Inc) with a fixed bearing and to 26 NexGen® TKA with a mobile bearing using the same methods.

The gait cycle time of the FIRST TKA was statistically significantly shorter at normal speed of walk, as well as double-support periods, as compared to both standard models. The normal walking speed was significantly higher with faster swing speed and stride lengths for the new TKA. Significantly better coordination scores were observed at normal walking speed for the FIRST TKA as compared to the fixed-bearing TKAs.

The FIRST TKA showed statistically significantly better really objective outcomes in terms of gait after one year of follow-up and similar subjective and semi-objective evaluations compared to two widespread TKA designs.

Introduction: Ankle arthropathy is associated with a decreased motion of the ankle-hindfoot during ambulation. Ankle arthrodesis was shown to result in degeneration of the neighbour joints of the foot. Inversely, total ankle arthroplasty conceptually preserves the adjacent joints because of the residual mobility of the ankle but this has not been demonstrated yet in vivo. It has also been reported that degenerative ankle diseases, and even arthrodesis, do not result in alteration of the knee and hip joints. We present the preliminary results of a new approach of this problem based on ambulatory gait analysis.

Patients and Methods: Motion analysis of the lower limbs was performed using a Physilog® (BioAGM, CH) system consisting of three-dimensional (3D) accelerometer and gyroscope, coupled to a magnetic system (Liberty©, Polhemus, USA). Both systems have been validated. Three groups of two patients were included into this pilot study and compared to healthy subjects (controls) during level walking: patients with ankle osteoarthritis (group 1), patients treated by ankle arthrodesis (group 2), patients treated by total ankle prosthesis (group 3).

Results: Motion patterns of all analyzed joints over more than 20 gait cycles in each subject were highly repeatable. Motion amplitude of the ankle-hindfoot in control patients was similar to recently reported results. Ankle arthrodesis limited the motion of the ankle-hindfoot in the sagittal and horizontal planes. The prosthetic ankle allowed a more physiologic movement in the sagittal plane only. Ankle arthritis and its treatments did not influence the range of motion of the knee and hip joint during stance phase, excepted for a slight decrease of the hip flexion in groups 1 and 2.

Conclusion: The reliability of the system was shown by the repeatability of the consecutive measurements. The results of this preliminary study were similar to those obtained through laboratory gait analysis. However, our system has the advantage to allow ambulatory analysis of 3D kinematics of the lower limbs outside of a gait laboratory and in real life conditions. To our knowledge this is a new concept in the analysis of ankle arthropathy and its treatments. Therefore, there is a potential to address specific questions like the difficult comparison of the benefits of ankle arthroplasty versus arthrodesis. The encouraging results of this pilot study offer the perspective to analyze the consequences of ankle arthropathy and its treatments on the biomechanics of the lower limbs ambulatory, in vivo and in daily life conditions.

Introduction. Quantification of daily upper-limb activity is a key determinant in evaluation of shoulder surgery. For a number of shoulder diseases, problem in performing daily activities have been expressed in terms of upper-limb usage and non-usage. Many instruments measure upper-limb movement but do not focus on the differentiations between the use of left or right shoulder. Several methods have been used to measure it using only accelerometers, pressure sensors or video-based analysis. However, there is no standard or widely used objective measure for upper-limb movement. We report here on an objective method to measure the movement of upper-limb and we examined the use of 3D accelerometers and 3D gyroscopes for that purpose.

Methods. We studied 8 subjects with unilateral pathological shoulder (8 rotator cuff disease: 53 years old ± 8) and compared them to 18 control subjects (10 right handed, 8 left handed: 32 years old ± 8, younger than the patient group to be almost sure they don_t have any unrecognized shoulder pathology). The Simple Shoulder Test (SST) and Disabilities of the Arm and Shoulder Score (DASH) questionnaires were completed by each subject.

Two modules with 3 miniature capacitive gyroscopes and 3 miniature accelerometers were fixed by a patch on the dorsal side of the distal humerus, and one module with 3 gyroscopes and 3 accelerometers were fixed on the thorax. The subject wore the system during one day (8 hours), at home or wherever he/she went. We used a technique based on the 3D acceleration and the 3D angular velocities from the modules attached on the humerus.

Results. As expected, we observed that for the stand and sit postures the right side is more used than the left side for a healthy right-handed person(idem on the left side for a healthy left-handed person). Subjects used their dominant upper-limb 18% more than the non-dominant upper-limb. The measurements on patients in daily life have shown that the patient has used more his non affected and non dominant side during daily activity if the dominant side = affected shoulder. If the dominant side ≠ affected shoulder, the difference can be showed only during walking period.

Discussion-Conclusion. The technique developed and used allowed the quantification of the difference between dominant and non dominant side, affected and unaffected upper-limb activity. These results were encouraging for future evaluation of patients with shoulder injuries, before and after surgery. The feasibility and patient acceptability of the method using body fixed sensors for ambulatory evaluation of upper limbs kinematics was shown.

Introduction: Coordination is a strategy chosen by the central nervous system to control the movements and maintain stability during gait. Coordinated multi-joint movements require a complex interaction between nervous outputs, biomechanical constraints, and pro-prioception. Quantitatively understanding and modeling gait coordination still remain a challenge. Surgeons lack a way to model and appreciate the coordination of patients before and after surgery of the lower limbs. Patients alter their gait patterns and their kinematic synergies when they walk faster or slower than normal speed to maintain their stability and minimize the energy cost of locomotion. The goal of this study was to provide a dynamical system approach to quantitatively describe human gait coordination and apply it to patients before and after total knee arthroplasty.

Methods: A new method of quantitative analysis of interjoint coordination during gait was designed, providing a general model to capture the whole dynamics and showing the kinematic synergies at various walking speeds. The proposed model imposed a relationship among lower limb joint angles (hips and knees) to parameterize the dynamics of locomotion of each individual. An integration of different analysis tools such as Harmonic analysis, Principal Component Analysis, and Artificial Neural Network helped overcome high-dimensionality, temporal dependence, and non-linear relationships of the gait patterns.

Ten patients were studied using an ambulatory gait device (Physilog®). Each participant was asked to perform two walking trials of 30m long at 3 different speeds and to complete an EQ-5D questionnaire, a WOMAC and Knee Society Score. Lower limbs rotations were measured by four miniature angular rate sensors mounted respectively, on each shank and thigh. The outcomes of the eight patients undergoing total knee arthroplasty, recorded pre-operatively and post-operatively at 6 weeks, 3 months, 6 months and 1 year were compared to 2 age-matched healthy subjects.

Results: The new method provided coordination scores at various walking speeds, ranged between 0 and 10. It determined the overall coordination of the lower limbs as well as the contribution of each joint to the total coordination. The difference between the pre-operative and post-operative coordination values were correlated with the improvements of the subjective outcome scores. Although the study group was small, the results showed a new way to objectively quantify gait coordination of patients undergoing total knee arthroplasty, using only portable body-fixed sensors.

Conclusion: A new method for objective gait coordination analysis has been developed with very encouraging results regarding the objective outcome of lower limb surgery.

Background: Mobile-bearing knee replacements have some theoretical advantages over fixed-bearing devices. However, very few randomized controlled clinical trials have been published to date, and studies showed little clinical and subjective advantages for the mobile-bearing using traditional systems of scoring. The choice of the ideal outcome measure to assess total joint replacement remains a complex issue. However, gait analysis provides objective and quantifying evidences of treatment evaluation. Significant methodological advances are currently made in gait analysis laboratories and ambulatory gait devices are now available. The goal of this study was to provide gait parameters as a new objective method to assess total knee arthroplasty outcome between patients with fixed- and mobile-bearing, using an ambulatory device with minimal sensor configuration.

This randomized controlled double-blind study included to date 14 patients: the gait signatures of four patients with mobile-bearing were compared to the gait signatures of nine patients with fixed-bearing pre-operatively and post-operatively at 6 weeks, 3 months and 6 months. Each participant was asked to perform two walking trials of 30m long at his/her preferred speed and to complete a EQ-5D questionnaire, a WOMAC and Knee Society Score (KSS). Lower limbs rotations were measured by four miniature angular rate sensors mounted respectively, on each shank and thigh.

A new method for a portable system for gait analysis has been developed with very encouraging results regarding the objective outcome of total knee arthroplasty using mobile- and fixed-bearings.

Background: Mobile-bearing knee replacements have some theoretical advantages over fixed-bearing devices. However, very few randomized controlled clinical trials have been published to date, and studies showed little clinical and subjective advantages for the mobile-bearing using traditional systems of scoring.

The choice of the ideal outcome measure to assess total joint replacement remains a complex issue. However, gait analysis provides objective and quantifying evidences of treatment evaluation. Significant methodological advances are currently made in gait analysis laboratories and ambulatory gait devices are now available.

The goal of this study was to provide gait parameters as a new objective method to assess total knee arthroplasty outcome between patients with fixed- and mobile-bearing, using an ambulatory device with minimal sensor configuration.

Methods: This randomized controlled double-blind study included to date 31 patients: the gait signatures of 12 patients with mobile-bearing were compared to the gait signatures of 19 patients with fixed-bearing pre-operatively and post-operatively at 6 weeks, 3 months and 6 months. Each participant was asked to perform two walking trials of 30m long at his/her preferred speed and to complete a EQ-5D questionnaire, a WOMAC and Knee Society Score (KSS). Lower limbs rotations were measured by four miniature angular rate sensors mounted respectively, on each shank and thigh.

Results: Better relative differences between pre-operative and post-operative 3 months and 6 months KSS (122% vs 34% at 3 months, 138% vs 36% at 6 months) and KSS function (154% vs 8% at 3 months, 183% vs 42% at 6 months) scores were observed for the fixed-bearing compared to the mobile-bearing. The same better improvements for fixed-bearing were also found with the range of knee angles (Affected side: 31% vs −5% at 3 months, 47% vs 5% at 6 months), (Unaffected side: 16% vs 5% at 3 months, 15% vs 6% at 6 months) and peak swing speeds of shank (Affected side: 18% vs −2% at 3 months, 30% vs 4% at 6 months), (Unaffected side: 8% vs −3% at 3 months, 7% vs 4% at 6 months).

Conclusions: A new method for a portable system for gait analysis has been developed with very encouraging results regarding the objective outcome of total knee arthroplasty using mobile- and fixed-bearings.