For clinical movement analysis, optical marker-based motion capture is the gold standard.

With the advancement of AI-driven computer vision, markerless motion capture (MMC) has emerged. Validity against the marker-based standard has only been examined for lightly-dressed subjects as required for marker placement. This pilot study investigates how different clothing affects the measurement of typical gait metrics.

Gait tests at self-selected speed (4 km/h) were performed on a treadmill (Motek Grail), captured by 9 cameras (Qualisys Miqus, 720p, f=100Hz) and analyzed by a leading MMC application (Theia, Canada). A healthy subject (female, h=164cm, m=54kg) donned clothes between trials starting from lightly dressed (LD: bicycle tight, short-sleeved shirt), adding a short skirt (SS: hip occlusion) or a midi-skirt (MS: partial knee occlusion) or street wear (SW: jeans covering ankle, long-sleeved blouse), the lattern combined with a short jacket (SWJ) or a long coat (SWC). Gait parameters (mean±SD, t=10s) calculated (left leg, mid-stance) were ankle pronation (AP-M), knee flexion (KF-M), pelvic obliquity (PO-M) and trunk lateral lean (TL-M) representing clinically common metrics, different joints and anatomic planes. Four repetitions of the base style (LD) were compared to states of increased garment coverage using the t-test (Bonferroni correction).

For most gait metrics, differences between the light dress (LD) and various clothing styles were absent (p>0.0175), small (< 2SD) or below the minimal clinically important differences (MCID). For instance, KF-M was for LD=10.5°±1.7 versus MD=12.0°±0.5 (p=0.07) despite partial knee cover. AP-M measured for LD=5.2°±0.6 versus SW=4.1°±0.7 (p<0.01) despite ankle cover-up. The difference for KF-M between LD=10.5°±1.7 versus SWL=6.0°±0.9, SW and SWJ (7.6°±1.5, p<0.01) indicates more intra-subject gait variability than clothing effect.

This study suggests that typical clothings styles only have a small clinically possibly negligible effect on common gait parameters measured with MMC. Thus, patients may not need to change clothes or be instructed to wear specific garments. In addition to avoiding marker placement, this further increases speed, ease and economy of clinical gait analysis with MMC facilitating high volume or routine application.

Introduction and Objective

An important subset of patients is dissatisfied after total joint arthroplasty (TJA) due to residual functional impairment. This study investigated the assessment of objectively measured step-up performance following TJA, to identify patients with poor functional improvement after surgery, and to predict residual functional impairment during early postoperative rehabilitation. Secondary, longitudinal changes of block step-up (BS) transfers were compared with functional changes of subjective patient reported outcome measures (PROMs) following TJA.

Hip resurfacing arthroplasty (HRA) became a popular procedure in the early 90s because of the improved wear characteristic, preserving nature of the procedure and the optimal stability and range of motion. Concerns raised since 2004 when metal ions were seen in blood and urine of patients with a MoM implant. Design of the prosthesis, acetabular component malpositioning, contact-patch-to-rim distance (CPR) and a reduced joint size all seem to play a role in elevated metal ion concentrations. Little is known about the influence of physical activity (PA) on metal ion concentrations. Implant wear is thought to be a function of use and thus of patient activity levels. Wear of polyethylene acetabular bearings was positively correlated with patient's activity in previous studies. It is hypothesized that daily habitual physical activity of patients with a unilateral resurfacing prosthesis, measured by an activity monitor, is associated with habitual physical activity.

A prospective, explorative study was conducted. Only patients with a unilateral hip resurfacing prosthesis and a follow-up of 10 ± 1 years were included. Metal ion concentrations were determined using ICP-MS. Habitual physical activity of subjects was measured in daily living using an acceleration-based activity monitor. Outcome consisted of quantitative and qualitative activity parameters.

In total, 16 patients were included. 12 males (75%) and 4 females (25%) with a median age at surgery of 55.5 ± 9.7 years [43.0 – 67.9] and median follow-up of 9.9 ± 1.0 years [9.1 – 10.9]. The median cobalt and chromium ion concentrations were 25 ± 13 and 38 ± 28 nmol/L. A significant relationship, when adjusting for age at surgery, BMI, cup size and cup inclination, between sit-stand transfers (p = .034) and high intensity peaks (p = .001) with cobalt ion concentrations were found (linear regression analysis).

This study showed that a high number of sit-stand transfers and a high number of high intensity peaks is significantly correlated with high metal ion concentrations, but results should be interpreted with care. For patients it seems save to engage in activities with low intensity peaks like walking or cycling without triggering critical wear or metal ions being able to achieve important general health benefits and quality of life, although the quality (high intensity peaks) of physical activity and behaviour of patients (sit-stand-transfers) seem to influence metal ion concentrations.

An increase in metal ion levels is seen after implantation of all MoM hip prosthesis due to release from the surface directly, more so during articulation and corrosion of the bearing surfaces. The bearing surfaces in MoM prosthesis consist of cobalt, chromium and molybdenum. Several case-reports of cobalt toxicity due to a MoM prosthesis have been published in the last decade. Cobalt intoxication may lead to a variety of symptoms: neuro-ocular toxicity (tinnitus, vertigo, deafness, blindness, convulsions, headaches and peripheral neuropathy), cardiotoxicity and thyroid toxicity. Nausea, anorexia and unexplained weight loss have been described. Systemic effects from metal ions even with well functioning implants or with ion concentrations lower than those associated with known adverse effects may exist and warrant investigation. The aim of this study is to investigate self-reported systemic complaints in association with cobalt ion concentrations in patients with any type of MoM hip prosthesis. A cohort study was conducted. Patients with both unilateral and bilateral, resurfacing and large head metal on metal total hip arthroplasties were included for the current study. Blood metal ion concentrations (cobalt and chromium) were measured by inductively coupled plasma mass spectrometry (ICP-MS). Based on the known cobalt toxicity symptoms of case-reports and toxicology reports a new non-validated questionnaire was developed. questions were subdivided in general questions/symptoms, vestibular symptoms, neurological symptoms, emotional health and cardio- and thyroid toxicity symptoms. Independent samples T test, Fishers Exact Test and Pearsons (R) correlation were used. Analysis was performed on two groups; a low cobalt ion concentration group and a high cobalt ion concentration group A total of 62 patients, 36 (58%) men and 26 (42%) women, were included with a mean age at surgery of 60.8 ± 9.3 years (41.6 – 78.1) and a mean follow up of 6.3 ± 1.4years (3.7 – 9.6). In these patients a total of 71 prosthesis were implanted: 53 unilateral and 9 bilateral. Of these, 44 were resurfacing and 27 large head metal on metal (LHMoM) total hip arthroplasties. Mean cobalt and chromium ion concentrations were 104 ± 141 nmol/L (9 – 833) and 95 ± 130nmol/L (6 – 592), respectively. Based on the different thresholds (120 – 170 or 220 nmol/L) the low cobalt ion concentration group consisted of 44 (71%), 51 (82%) or 55 (89%) subjects respectively. No differences were found in general characteristics, independently of the threshold. The composite score of vestibular symptoms (vision, hearing, tinnitus, dizziness) was significantly higher (p < .050) in all high cobalt ion concentrations groups, independent of the threshold value This study aimed to detect a trend in self-reported systemic complaints in patients with metal-on-metal hip arthroplasty due to raised cobalt ion concentrations. Vestibular symptoms were more common in high cobalt ion concentration groups independent of the three threshold levels tested. The upper limit of acceptable cobalt ion concentrations remains uncertain. With regards to proactively inquired, self-reported symptoms the threshold where effects may be present could be lower than values currently applied in clinical follow-up. It is unknown what exposure to elevated metal ion concentrations for a longer period of time causes with aging subjects. Further research with a larger cohort and a more standardized questionnaire is necessary to detect previously undiscovered or under-reported effects.

The relevance of physical activity (PA) for general health and the value of assessing PA in the free-living environment especially for assessing orthopaedic conditions and outcome are discussed. Available methods for assessing PA such as self-reports, trackers, phone apps and clinical grade monitors are introduced. An overview of devices such as accelerometers for research quality assessments is given and aspects for choosing them such as wear location, usability or study population are reviewed. Basic principles to derive mobility parameters from the PA related sensor signals are presented. The symposium explains mobility parameters, their types, definitions, validity, analysis and those with particular relevance to assess orthopaedic conditions. The application of activity monitors is orthopaedic patient studies is demonstrated in various examples such as knee and hop osteoarthritis and total joint arthroplasty, in frail elderly subjects at fall risk or patients with shoulder pathologies.

Lower limb fractures are commonly treated with cast immobilization, and as a main consequence of strict immobilization this typically leads to loss in muscle mass, decrease of bone density and decline in functional abilities. Body-worn sensors are increasingly used to assess outcome in clinical trials by providing objective mobility parameters in a real-world environment. The aim of this study is to investigate the usability aspects and potential changes in mobility parameters in partial-immobilization patients in real-world conditions. Six healthy young males (age 22.2 ± 1.2 years; weight 76.5 ± 6.7 kg, height 185.8 ± 6.1 cm. Mean ± standard deviation) wore a leg cylinder cast with walker boot to immobilize their dominant leg for two consecutive weeks. Subjects were asked to continuously wear a tri-axial accelerometer on the waist (actibelt) during waking hours for 6 weeks including 2 weeks before, during and after cast immobilisation. The total amount of days of continuous recording was 339 days with a total wearing time of 120 days. Software packages which allow to detect steps and to estimate real-world walking speed were used to analyse the accelerometry data. It was suspected that knee immobilization would affect strongly the wave form of the signal with an impact on the accuracy of the speed algorithm, whereas the step detection should be more robust. This effect was confirmed in a preliminary study performed to quantify the accuracy under immobilization conditions. On the other hand, step numbers are known to be sensitive to fluctuations in wearing time which was not uniform throughout the entire study. We concluded that in this setting step frequency is the most reliable parameter. Step frequency showed a systematic decrease in the values during the immobilization period which recovered to pre-immobilisation values after cast removal. This confirms the usability of accelerometry and sensitivity of its mobility parameters for clinical outcome assessment.

Restoring native hip anatomy and biomechanics is important to create a well-functioning total hip arthroplasty (THA). Hip offset and leg length are regarded as the most important biomechanical characteristics. This study investigated their association with clinical outcomes including patient reported outcome measures (PROMs) and functional tests. This prospective cohort study was conducted in 77 patients undergoing primary THA (age=65±11 years). Hip offset and leg length were measured on anteroposterior radiographs of the hip pre- and postoperatively. Participants completed the Western Ontario & McMaster Universities Osteoarthritis Index (WOMAC) and performed functional tests (i.e. gait, single leg stance, sit-to-stand, block step-up) preoperatively, and 3 and 12 months postoperatively. A wearable motion sensor was used to derive biomechanical parameters. Associations between radiographic and functional outcomes were investigated with the Spearman's rho correlation coefficient. Subgroup comparisons were conducted for patients with more than 15% decreased or increased femoral offset after THA. Differences in postoperative offset and leg length had little impact on clinical outcomes. Femoral offset subgroups demonstrated no significantly different WOMAC function scores. In functional tests, patients with >15% decreased femoral offset after THA demonstrated more sagittal plane motion during block step-up (14.43° versus 10.66°; p=0.04) while patients with >15% increased femoral after THA demonstrated more asymmetry of frontal plane motion during block step-up (34.05% versus 14.18%; p=0.03). To create a well-functioning THA, there seems to be a reasonable safe zone regarding the reconstruction of offset and leg length.

3D measurement of joint angles so far has only been possible using marker-based movement analysis, and therefore has not been applied in (larger scale) clinical practice (performance test) and even less so in the free field (activity monitoring). 3D joint angles could provide useful additional information in assessing the risk of anterior cruciate ligament injury using a vertical drop jump or in assessing knee range of motion after total knee arthroplasty. We developed a tool to measure dynamic 3D joint angles using 6 inertial sensors, attached to left and right shank, thigh and pelvis. The same sensors have been used for activity identification in a previous study. To validate the setup in a pilot study, we measured 3D knee and hip angles using the sensors and a Vicon movement lab simultaneously in 3 subjects. Subjects performed drop jumps, squats and ran on the spot. The mean error between Vicon and sensor measurement for the maximum joint angles was 3, 7 and 8 degrees for knee flexion, ad/abduction and rotation respectively, and 9, 7 and 10 degrees for hip flexion, ad/abduction and rotation respectively. No calibration movements were required. A major part of the inaccuracy was caused by soft tissue effects and can partly be resolved by improved sensor attachment. These pilot results show that it is feasible to measure 3D joint angles continuously using unobtrusive light-weight sensors. No movement lab is necessary and therefore the measurements can be done in a free field setting, e.g. at home or during training at a sport club. A more extensive validation study will be performed in the near future.

Introduction

Knee osteoarthritis (KOA) causes impairment through pain, stiffness and malalignment and knee joint replacement (KJR) may be necessary to alleviate such symptoms. There is disagreement whether patients with KJR increases their level of physical activity after surgery. The aim of this study is to investigate whether patients with KJR have a higher level of physical activity than patients with KOA, as measured by accelerometer-based method. Furthermore, to investigate whether patients achieve the same level of activity as healthy subjects five years post TJR.

Introduction

Following primary total knee arthroplasty (TKA), patients experience pain relief and report improved physical function and activity. However, there is paucity of evidence that patients are truly more active in daily life after TKA. The aims of this study were: 1) to prospectively measure physical activity with a wearable motion sensor before and after TKA; 2) to compare patient-reported levels of physical activity with objectively assessed levels of physical activity before and after TKA; 3) to investigate whether differences in physical activity after TKA are related to levels of physical function.

Introduction

Limited physical activity (PA) is one indication for orthopaedic intervention and restoration of PA a treatment goal. However, the objective assessment of PA is not routinely performed and in particular the effect of spinal pathology on PA is hardly known. It is the purpose of this study using wearable accelerometers to measure if, by how much and in what manner spinal stenosis affects PA compared to age-matched healthy controls.

Background

Shoulder pain limits range of motion (ROM) and reduces performing activities of daily living (ADL). Objective assessment of shoulder function could be of interest for diagnosing shoulder pathology or functional assessment of the shoulder after therapy.

The feasibility of 2 wearable inertial sensors for functional assessment to differentiate between healthy subjects and patients with unilateral shoulder pathology is investigated using parameters as asymmetry.

The significance of physical activity (PA) assessment is widely acknowledged as it can aid in the understanding of pathologies. PA of knee osteoarthritis (KOA) patients has been assessed with varying methods, as it is a disease that is known to impair physical function and activity during daily life. Differences between methods have been described for general outcomes (sport participation or sedentary time), yet failed to describe common activities such as stair locomotion or sit-to-stand (STS) transfers. This study therefore aimed to determine the comparability of various methods to assess daily-life activities in KOA patients.

Sixty-one clinically diagnosed KOA patients wore a tri-axial accelerometer (AX3, Axivity, UK) for one week during waking hours. Furthermore, they performed three physical function tests: a 40-m fast-paced walk test (WT), a timed up-and-go test (TUGT) and a 15 stair-climb test (SCT). Patients were also asked to fill out the Knee Osteoarthritis Outcome Score (KOOS), a KOA-specific questionnaire.

Patients were slightly overweight (average BMI: 27.3±4.8 kg/m2), 60 (±10) years old and predominantly female (53%). The amount of daily level walking bouts was only weakly correlated with the WT performance, representing patients” walking capacity, (ρ=−0.33, p=0.01). Similarly, level-walking bouts during daily life correlated weakly with self-perceived walking capacity addressed by the KOOS (ρ=−0.36, p=0.01). For stair locomotion, a slightly different trend was seen. A moderate correlation was found (ρ=0.65, p<0.001), between the amount of ascending bouts and the objective functional test performance (SCT). However, the subjective assessment of stair ascending limitations (via the KOOS) correlated only weakly with both the functional test performance and the measured level of activity (ρ=−0.30 and −0.35, resp.). Comparable results were found for descending motions. STS transfers during daily life correlated moderately at best with the time to complete the TUGT (ρ=−0.43, p<0.01) and only weakly with the self-perceived effort of STS transfers (ρ=−0.26, p=0.04).

Only weak correlations existed between subjective measures and objective parameters (for both functional tests and daily living activities), indicating that they assess different domains (e.g. self-perceived function vs. actual physical function). Furthermore, when comparing the two objective measures, correlation coefficients increased compared to the subjective methods, yet did not reach strong agreement. These findings suggest that addressing common activities of daily life either subjectively or objectively will result in different patient-related outcomes of a study. Assessment methods should therefore be chosen with caution and compared carefully with other studies.

Background

Complete and reliable outcome assessment is important for clinical quality control and research evidence. Online questionnaires offer the opportunity to perform follow-up at distance and desired frequency saving efforts and cost to patients and hospitals increasingly not reimbursed for this service. Patients in this unique study have been invited by mail (not at visit or by phone) and were asked to complete both methods (online, paper) instead of only one option. For the first time, response, completion and reliability of the HOOS, KOOS-PS and New-KSS, popular patient-reported outcomes (PROM's) in TJA were measured.

Background

The goal of total hip arthroplasty (THA) is to reduce pain, restore function but also activity levels for general health benefits or social participation. Thus evaluating THA patient activity can be important for diagnosis, indication, outcome assessment or biofeedback.

Background

In total knee arthroplasty (TKA), patient reported outcome on pain, function or satisfaction fails to differentiate treatment options. Activity, a consequence of pain-free, well functioning TKA and a satisfied patient, may be a discriminative surrogate metric, especially when objectively measured.

Background

To complement subjective patient-reported outcome measures, objective assessments are needed. Activity is an objective clinical outcome which can be measured with wearable activity monitors (AM). AM's have been validated and used in joint arthroplasty patients to count postures, walking or transfers. However, for demanding patients such as after sports injury, running is an important activity to quantify. A new AM algorithm to distinguish walking from running is trialed in this validation study.

Background

Metal-on-metal hip implants can produce adverse tissue reactions to wear debris. Increased metal ion concentrations in the blood are measured as a proxy to wear and the complications it can trigger. Many studies have examined various factors influencing the metal ion concentrations. This is the first study to investigate the effect of physical activity level, as objectively measured in daily life, on blood ion levels, expecting higher concentrations for higher patient activity.

Background

The second generation metal-on-metal (MoM) prosthesis of the hip became a worldwide success in the 90s. However, after the placement of a MoM prosthesis the cobalt ion concentrations raise significantly. This may lead to systemic complaints and even cobalt toxicity.

Background

Assessment of functional outcome after total hip arthroplasty (THA) often involves subjective patient-reported outcome measures (PROMs) whereas analysis of gait allows more objective assessment. The aims of the study were to compare longitudinal changes of WOMAC function score and ambulatory gait analysis after THA, between patients with low and high self-reported levels of physical function.