K. Boivin

New Accelerometric Method to Discriminate Between Asymptomatic Subjects and Patients With Medial Knee Osteoarthritis During 3-D Gait

This study presents a new method to estimate 3-D linear accelerations at tibial and femoral functional coordinate systems. The method combines the use of 3-D accelerometers, 3-D gyroscopes and reflective markers rigidly fixed on an exoskeleton and, a functional postural calibration method. Marker positions were tracked by a six-camera optoelectronic system (VICON 460, Oxford Metrics). The purpose of this study was to determine if this method could discriminate between medial osteoarthritic and asymptomatic knees during gait. Nine patients with osteoarthritic knees and nine asymptomatic control subjects were included in this study. Eighteen parameters representing maximal, minimal, and range of acceleration values were extracted during the loading and preswing to mid-swing phase periods, and were compared in both groups. Results show good discriminative capacity of the new method. Eight parameters were significantly different between both groups. The proposed method has the potential to be used in comprehending and monitoring gait strategy in patients with osteoarthritic knee.

Automatic Classification of Asymptomatic and Osteoarthritis Knee Gait Patterns Using Kinematic Data Features and the Nearest Neighbor Classifier

The aim of this work is to develop an automatic computer method to distinguish between asymptomatic (AS) and osteoarthritis (OA) knee gait patterns using 3-D ground reaction force (GRF) measurements. GRF features are first extracted from the force vector variations as a function of time and then classified by the nearest neighbor rule. We investigated two different features: the coefficients of a polynomial expansion and the coefficients of a wavelet decomposition. We also analyzed the impact of each GRF component (vertical, anteroposterior, and medial lateral) on classification. The best discrimination rate (91%) was achieved with the wavelet decomposition using the anteroposterior and the medial lateral components. These results demonstrate the validity of the representation and the classifier for automatic classification of AS and OA knee gait patterns. They also highlight the relevance of the anteroposterior and medial lateral force components in gait pattern classification.

Exploring the Limits of Peripheral Vision for the Control of Movement

Abstract The role played by peripheral visual information in the control of aiming movements is not fully understood, as is indicated by the conflicting results reported in the literature. In the present study, the authors tested and confirmed the hypothesis that the source of the conflict lies in the portion of the visual peripheral field that has been under scrutiny in the different studies. Participants (N = 60) moved a computer mouse from a fixed starting position to 1 of 3 targets under varied vision conditions. The portion of the peripheral visual field that best ensured directional accuracy of a sweeping movement was found to be located between 20° and 10° of visual angle, whereas the area found to favor directional accuracy of an aiming movement comprised 30° through 10° of visual angle.

Test-Retest Reliability and Minimal Clinical Change Determination for 3-Dimensional Tibial and Femoral Accelerations During Treadmill Walking in Knee Osteoarthritis Patients

OBJECTIVE To determine the test-retest reliability and the minimal clinical change determination for accelerometric parameters, estimated by a new accelerometric-based method that estimates 3-dimensional (3D) linear accelerations of the tibia and femur during comfortable and fast walking speeds. DESIGN Test-retest study. SETTING Gait laboratory in a research center. PARTICIPANTS Patients (N=25; 6 men, 19 women) with symptomatic knee osteoarthritis (OA). INTERVENTIONS Not applicable. MAIN OUTCOMES MEASURES Subjects attended 2 walking sessions in which accelerometers were rigidly fixed by means of an exoskeleton to the femoral and tibial segments. In both sessions, 3D accelerations were collected for 25 seconds for each of the walking speeds. Mean accelerometric pattern was calculated using 15 gait cycles. From each mean pattern, maximal, minimal, and range values were extracted from the loading phase period. The root mean square (RMS) value was also calculated for every pattern. Relative and absolute reliability were determined using intraclass correlation (ICC) and standard error (SE) of measurement, respectively. Minimal detectable change was calculated for each parameter as the least significant difference. RESULTS Tibial and femoral accelerations showed reliable values across sessions 1 and 2 with ICCs greater than or equal to .75 for 96% and 88% of the parameters at comfortable and fast speeds, respectively. The SE of measurement ranged from .01 to .05g for the RMS value and from .05 to .35g for maximal, minimum, and range point parameters. CONCLUSIONS The proposed method is the first to have determined the reliability and the minimal detectable change for tibial and femoral acceleration parameters in knee OA patients during a treadmill walking evaluation. The minimal detectable change determined in this study will be used to determine improvement or deterioration of knee OA patients after rehabilitation.

The responsiveness of three-dimensional knee accelerations used as an estimation of knee instability and loading transmission during gait in osteoarthritis patient's follow-up

OBJECTIVE Knee instability and joint loading transmission are two important biomechanical factors in subjects with knee osteoarthritis (OA). However, the relationship between these factors in a rehabilitation treatment remains unclear. The purpose of this study is to determine the responsiveness of a new three-dimensional (3D) acceleration method used as an estimation of knee instability and joint loading transmission during gait in OA subjects after a rehabilitation treatment. METHOD Twenty-four subjects with medial knee OA were included in this study. They had clinical and gait evaluations before and after 12 weeks of treatment. 3D linear knee accelerations, quadriceps and hamstring isometric strength and Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) pain were quantified, and compared between both evaluations. Nine asymptomatic subjects participated in this study for gait comparison. RESULTS A significant reduction of the anterior posterior (AP) knee acceleration peak (P=0.02) had been detected after the treatment. No difference for both distal and lateral knee accelerations peak was found. A significant increase in quadriceps (P<0.001) and hamstring (P=0.006) strength was seen after treatment. The WOMAC of pain had shown significant reduction after the treatment (P<0.001). CONCLUSION The present study demonstrates that the estimation of knee acceleration parameters is sensitive to changes in knee OA gait after a rehabilitation treatment. This study also indicates that a treatment of 3 months which combines therapeutic and exercises program could have benefits on knee OA by increasing AP knee stability and stabilize joint loading transmission during gait.

Hierarchical analysis and classification of asymptomatic and knee osteoarthritis gait patterns using a wavelet representation of kinetic data and the nearest neighbor classifier

The purpose of this study is twofold: (1) to develop a classification method to distinguish between asymptomatic (AS) and knee osteoarthritis (OA) gait patterns using ground reaction force (GRF) measurements, and (2) to investigate OA severity within OA gait patterns. Features were first extracted from the GRF vectors to be used for classification. We investigated a two-level hierarchical classification and analysis method using the nearest neighbor rule. At the first level, the GRF data were classified into two classes: AS and OA. At the second level, the GRF data of OA patients were classified according to the pathology severity. The OA patients were grouped into two OA severity categories according to the Kellgren and Lawrence (KL) scale: KL 1 and KL 2 for one category, and KL 3 and KL 4 for the other. Experiments were conducted using data of 42 cases, 16 AS and 26 pathological. The method discriminated between AS and OA subjects with an accuracy of 38 of 42 cases, and assessed the severity correctly with an accuracy of 20 of 26 cases. These results demonstrated the validity of both, the feature and the classifier, for automatic classification of AS and knee OA gait patterns and for analysis of OA severity.

Knee Frontal Plane Dynamic Alignment in Knee Osteoarthritis Patients: Impact of a 12-week Physical Therapy Program and Relationship with Functional Scores

tendonosis or a partial tear of a gluteus medius and/or minimus tendon. The patients were then contacted and asked to complete questionnaires to assess their pain, function, and satisfaction with treatment. Main Outcome Measures: Improvement in pain, patient satisfaction and function following PRP injection. These were measured by follow-up questionnaires that included the Visual Numerical Scale, Functional Rating Index, and North American Spine Society patient satisfaction index. Results or Clinical Course: 10 patients met criteria (9 female, 1 male). Average age was 64.7 years. Mean duration of pain prior to injection was 46 months (range 8 to 120 mo). Mean follow up was 10.2 months (range 6 to 26 mo). The average pain score (as measured by VAS) was 8.10 (SD 1.7) pre-injection and 3.8 (SD 2.7) post-injection (p 1⁄4 .002). Overall patient satisfaction was 80% (as measured by NASS). Two patients reported no improvement. Of the 8 patients who reported improvement, their mean Functional Rating Index (FRI) score was 62.4 (out of 100) before their PRP injection and 21.3 six months post-injection (p 1⁄4 .001). The average pain score (VAS) among these 8 patients was 8.7 (SD 1.1) pre-injection and 2.7 (SD 2.1) post-injection. Conclusions: The results from this small retrospective case series suggest that PRP may be an efficacious conservative treatment option for patients with symptomatic gluteus medius tears, degeneration, and tendinosis. More robust prospective studies are needed to better evaluate this treatment.

151 EFFECTS OF PHYSIOTHERAPY TREATMENT ON KNEE OA GAIT DATA USING CLUSTER ANALYSIS

dictors of single limb standing balance in individuals with medial compartment knee OA. Methods: Fifty seven consecutive patients with radiographicallyconfirmed medial compartment knee OA underwent strength and balance testing of their diseased limb (most painful in cases of bilateral disease) during a single testing session. Lower limb alignment and radiographic disease severity (Kellgren and Lawrence (KL) grade dichotomized as mild (grade 2) or mod/severe (grades 3 and 4)) were also measured and participants completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) prior to testing. Maximal isometric torque of the hip and knee extensors as well as the hip abductors and adductors were measured with an isokinetic dynamometer (knee) or hand-held dynamometer (hip) and normalised to body mass (Nm/kg). For standing balance testing, participants were required to stand as still as possible on the affected limb for 10 seconds while centre of pressure (COP) data were collected from a force platform. An initial logistic regression was performed to identify differences between those who were able to perform three trials of balance from those who were unable. Multiple linear regression was also performed to identify anatomical and disease-specific predictors of total COP path length in those able to complete the three trials. Results: Thirty four participants (60%) were able to complete all standing balance trials, while twenty three were unable. Logistic regression indicated that only age and WOMAC pain were significant predictors of group classification (able/unable) with those participants able to complete the trials more likely to be younger (p = 0.04) and report less knee pain (p = 0.04). When examining standing balance data (n=34), our multiple regression model (Table 1) was able to explain 65.4% of the variance in COP path length with disease severity (p < 0.001), alignment (p = 0.03), and pain (p = 0.03) significantly contributing to the model. In particular, better standing balance (ie. smaller COP length values) was associated with more severe disease, less varus malalignment, and less pain.

THE RELATIONSHIP OF FRONTAL PLANE KNEE KINEMATICS WITH KNEE ALIGNMENT AND ADDUCTION MOMENT

It has been recognised that a knee varus alignment measured from static radiographs and a high knee adduction moment during gait are two important risk factors in the progression of medial knee osteoarthritis (OA) [Sharma, 2006]. We previously identified new frontal plane kinematic parameters enable to discriminate patients with severe knee OA from those with mild OA as well as asymptomatic subjects [Boivin, 2007]. The objective here is to determine the relationship of these knee kinematic parameters with a functional varus/valgus alignment and the knee adduction moment.