Sit-To-Stand Biomechanics Before and After Total Hip Arthroplasty

Lower limb joint loading in patients with unilateral hip osteoarthritis during bipedal stance and the effect of total hip replacement

Osteoarthritis of the hip is a common condition that affects older adults. Total hip replacement is the end-stage treatment to relief pain and improve joint function. Little is known about the mechanical load distribution during the activity of bipedal stance, which is an important daily activity for older adults who need to rest more frequently. This study investigated the distribution of the hip and knee joint moments during bipedal stance in patients with unilateral hip osteoarthritis and how the distribution changed 1 year after total hip replacement. Kinematic and kinetic data from bipedal stance were recorded. External hip and knee adduction moments were calculated and load distribution over both limbs was calculated using the symmetry angle. Preoperatively, the non-affected limb carried 10% more body weight than the affected limb when standing on two legs. Moreover, the mean external hip and knee adduction moments of the non-affected limb were increased compared to the affected limb. At follow-up no significant differences were observed between the patients' limbs. Preoperative and postoperative changes in hip adduction moment were mainly explained by the combination of the vertical ground reaction force and the hip adduction angle. Stance width also explained changes in the hip and knee adduction moments of the affected leg. Furthermore, as with walking, bipedal standing also showed an asymmetric mechanical load distribution in patients with unilateral hip osteoarthritis. Overall, the findings suggest the need for preventive therapy concepts that focus not only on walking but also on optimizing stance towards a balanced load distribution of both legs.

Evaluation of Sit-to-Stand Movement in Older Adults with Locomotive Syndrome Using the Nintendo Wii Balance Board

Standing up from a chair is a mechanically demanding daily motion, and its biomechanics represent motor performance. In older adults with locomotive syndrome (LS), sit-to-stand (STS) movement with adequate postural control is essential to prevent falls. This study evaluated the characteristics of dynamic balance during STS movement on older adults with LS. A total of 116 participants aged ≥65 years were divided into Non-LS, LS stage 1, and LS stage 2 groups using the LS risk test. The participants were instructed to stand on the Nintendo Wii Balance Board as quickly as possible, and the STS movement was quantified using the vertical ground reaction force (VGRF) and center of pressure (CoP). The STS score, which represented dynamic balance, was significantly different among the groups (p < 0.001). The rate of VGRF development was significantly lower in the LS stages 1 and 2 than in the Non-LS group (p < 0.001). On the other hand, the total distance of the CoP path did not differ among the groups (p = 0.211). These findings indicated a reduction of postural control in older adults with LS. The STS score emphasized the importance of balance training to prevent falls in older adults with LS.

Model-Based Acetabular Cup Orientation Optimization Based On Minimizing the Risk of Edge-Loading and Implant Impingement Following Total Hip Arthroplasty

In this paper, a computationally-efficient model-based method for determining patient-specific optimal acetabular cup alignment for total hip arthroplasty (THA) is presented. The proposed algorithm minimizes the risk of implant impingement and edge-loading, which are reported as the major causes of hip dislocation following THA. First, by using motion capture data recorded from the patient performing different daily activities, the hip contact force and the relative orientation of the femur and pelvis are calculated by a musculoskeletal model. Then, by defining two quantitative indices i.e., angular impingement distance and angular edge-loading distance, the risk of impingement and edge-loading are assessed for a wide range of cup alignments. And finally, three optimization criteria are introduced to estimate the optimal cup alignment with a tradeoff between the risk of impingement and edge-loading. The results show that patient-specific characteristics such as pelvic tilt could significantly change the optimal cup alignment, especially the value of cup anteversion. Therefore, in some cases, the well-known Lewinnek safe zone may not be optimal, or even safe. Unlike other dynamic model-based methods, in this work, the need for force plate measurements is eliminated by estimating the ground reaction forces and moments, which makes this method more practical and cost-efficient. Furthermore, the low computational complexity due to analytical formulas makes this method suitable for both preoperative and intra-operative planning.

The Recovery of Weight-Bearing Symmetry After Total Hip Arthroplasty Is Activity-Dependent

This study aimed to characterize ipsilateral loading and return to weight-bearing symmetry (WBS) in patients undergoing total hip arthroplasty (THA) during activities of daily living (ADLs) using instrumented insoles. A prospective study in 25 THA patients was performed, which included controlled pre- and postoperative follow-ups in a single rehabilitation center of an orthopedic department. Ipsilateral loading and WBS of ADLs were measured with insoles in THA patients and in a healthy control group of 25 participants. Measurements in the THA group were performed at 4 different visits: a week pre-THA, within a week post-THA, 3–6 weeks post-THA, and 6–12 weeks post-THA, whereas the healthy control group was measured once. ADLs included standing comfortably, standing evenly, walking, and sit-to-stand-to-sit (StS) transitions. All ADLs were analyzed using discrete methods, and walking included a time-scale analysis to provide temporal insights in the ipsilateral loading and WBS waveforms. THA patients only improved beyond their pre-surgery levels while standing comfortably (ipsilateral loading and WBS, p < 0.05) and during StS transitions (WBS, p < 0.05). Nevertheless, patients improved upon their ipsilateral loading and WBS deficits observed within a week post-surgery across all investigated ADLs. Ipsilateral loading and WBS of THA patients were comparable to healthy participants at 6–12 weeks post-THA, except for ipsilateral loading during walking (p < 0.05) at the initial and terminal double-leg support period of the stance phase. Taken together, insole measurements allow for the quantification of ipsilateral loading and WBS deficits during ADLs, identifying differences between pre- and postoperative periods, and differentiating THA patients from healthy participants. However, post-THA measurements that lack pre-surgery assessments may not be sensitive to identifying patient-specific improvements in ipsilateral loading and WBS. Moreover, StS transitions and earlier follow-up time points should be considered an important clinical metric of biomechanical recovery after THA.

Which functional tasks present the largest deficits for patients with total hip arthroplasty before and six months after surgery? A study of the timed up-and-go test phases

Six to eight months after total hip arthroplasty, patients only attain 80% of the functional level of control groups. Understanding which functional tasks are most affected could help reduce this deficit by guiding rehabilitation towards them. The timed up-and-go test bundles multiple tasks together in one test and is a good indicator of a patient's overall level of function. Previously, biomechanical analysis of its phases was used to identify specific functional deficits in pathological populations. To the best of our knowledge, this analysis has never been performed in patients who have undergone total hip arthroplasty. Seventy-one total hip arthroplasty patients performed an instrumented timed up-and-go test in a gait laboratory before and six months after surgery; fifty-two controls performed it only once. Biomechanical features were selected to analyse the test's four phases (sit-to-stand, walking, turning, turn-to-sit) and mean differences between groups were evaluated for each phase. On average, six months after surgery, patients' overall test time rose to 80% of the mean of the control group. The walking phase was revealed as the main deficiency before and after surgery (-41 ± 47% and -22 ± 32% slower, respectively). High standard deviations indicated that variability between patients was high. On average, patients showed improved results in every phase of the timed up-and-go test six months after surgery, but residual deficits in function differed between those phases. This simple test could be appropriate for quantifying patient-specific deficits in function and hence guiding and monitoring post-operative rehabilitation in clinical settings.

Individuals with gluteal tendon repair display similar hip biomechanics to those of a healthy cohort during a sit-to-stand task

BACKGROUND

Gluteal-tendon repair (GTR) is reported to be effective for relieving pain and improving clinical function in patients with gluteal-tendon tears. The sit-to-stand (STS) task is an important activity of daily living and is often used to assess functional capacity in clinical populations. Understanding if and how STS performance is altered in individuals with gluteal tendon repair may be an effective marker of GTR outcomes as well as a possible therapeutic target for post-operative rehabilitation.

RESEARCH QUESTION

Do biomechanical parameters during STS differ between age- and sex-matched participants with and without gluteal-tendon repair?

METHODS

27 participants with a GTR and 29 healthy participants performed the STS task. Data were acquired using the three-dimensional motion capture system and forceplates. Outcomes of interest were task duration, rate of force development, trunk, pelvis, and hip joint angles, moments and powers. Differences were assessed using Generalised linear multivariate models and statistical parametric mapping.

RESULTS

GTR patients performed the STS movement significantly slower (1.4+/- 0.40 s) compared to controls (1.1+/ -0.2 s) with a significantly lower rate of force development (35.1+/- 5.7 N/kg/ms vs 30.3+/- 8.5 N/kg/ms). There were no group differences for hip, pelvis, or trunk angle over the movement cycle or for maximal or minimal values. Furthermore, there were no significant differences detected in hip joint kinetics. However, there appeared to be substantial between-subject variability indicating different patient-specific movements patterns.

SIGNIFICANCE

Individuals with a GTR performed the STS task about 20 % slower than healthy controls with a lower rate of force development. The individual variations indicate that participants likely employed different movement strategies to achieve STS. While the lack of differences between groups could suggest that GTR helps restore function and corrects the proposed underlying aetiology, it is possible that the STS task was not sufficiently challenging to discriminate between groups.

Individuals with Unilateral Mild-to-Moderate Hip Osteoarthritis Exhibit Lower Limb Kinematic Asymmetry during Walking But Not Sit-to-Stand

Asymmetry during gait is associated with the evolution of secondary osteoarthritis. Kinematic asymmetry has been reported in advanced stages of hip osteoarthritis but has not been evaluated in earlier stages of the disease or has it been directly compared with unilateral and bilateral hip osteoarthritis. Our objective was to evaluate within-group symmetry and compare between-group asymmetry for three-dimensional pelvis, hip, knee, and ankle kinematics during walking and sit-to-stand in individuals with unilateral mild-to-moderate hip OA, bilateral mild-to-moderate hip osteoarthritis, and healthy controls. Twelve individuals with unilateral mild-to-moderate hip OA, nine individuals with bilateral mild-to-moderate symptomatic and radiographic hip OA, and 21 age-comparable healthy controls underwent three-dimensional motion analysis during walking and sit-to-stand. Pelvis and lower limb joint angles were calculated using inverse kinematics and between-limb symmetry was assessed for each group. Any resulting asymmetries (most affected minus contralateral limb) were compared between groups. Participants with unilateral hip osteoarthritis exhibited significantly less hip extension (7.90°), knee flexion (4.72°), and anterior pelvic tilt (3.38°) on their affected limb compared with the contralateral limb during the stance phase of walking. Those with unilateral hip osteoarthritis were significantly more asymmetrical than controls for sagittal plane hip and pelvis angles. No significant asymmetries were detected within- or between-groups for sit-to-stand. Individuals with unilateral hip osteoarthritis exhibited lower limb asymmetries consistent with those reported in advanced stages of disease during walking, but not sit-to-stand. Consideration of the possible negative effects of gait asymmetry on the health of the affected and other compensating joints appears warranted in the management of hip OA.

Kinematic and Kinetic Changes after Total Hip Arthroplasty during Sit-To-Stand Transfers: Systematic Review

Background

Total hip arthroplasty (THA) is a common and effective surgical procedure that allows patients with hip osteoarthritis to restore functional ability and relieve pain. Sit-to-stand transfers are common demanding tasks during activities of daily living and are performed more than 50 times per day. The purpose of this systematic review is to obtain a comprehensive understanding of biomechanical changes during sit-to-stand transfers after THA.

Methods

Relevant articles were selected through MEDLINE, Scopus, Embase, and Web of Science. Articles were included if they met the following inclusion criteria: 1) participants underwent total hip arthroplasty without restriction on the arthroplasty design, 2) involved either kinematic or kinetic variables as the primary outcome measure, 3) evaluated sit-to-stand, and 4) were written in English.

Results

A total of 11 articles were included in the current systematic review. The THA group exhibited altered movement patterns as compared to healthy controls. Improvement in loading asymmetry was found up to 1 year after THA, but other kinetic changes indicate intensified contralateral limb loading. Limb differences were apparent, but whether these differences persist over 10 months after THA is still unknown.

Conclusion

Despite the inevitable changes in kinematics and kinetics in sit-to-stand transfers after THA, it appears to be important to resolve asymmetrical loading between the operative and nonoperative limbs to minimize risk for subsequent joint problems.

Recovery of Lower Extremity Function in the Initial Year Following Periacetabular Osteotomy: A Single Subject Analysis

BACKGROUND

Little is known regarding how lower extremity joint function recovers in the 6 months following periacetabular osteotomy (PAO) for activities other than walking.

PURPOSE

Assess patient-reported outcomes, hip strength, lower extremity joint moments, and moment distributions during sit-to-stand in a female athlete during the one-year period following PAO.

METHODS

Patient-reported outcomes (i.e. hip and groin outcome score; HAGOS), hip strength, and lower extremity joint moments and contributions to peak support moment during the sit-to-stand were assessed pre-operatively and at 6 weeks, 12 weeks, 6 months, and 13 months following PAO.

RESULTS

HAGOS scores returned to normative ranges, however overall quality of life scores remained low. By 13-month muscle strength recovered to baseline values. Following surgery, peak support and hip extensor moments were higher on the non-surgical limb, but the contributions of hip, knee, and ankle to peak support moment did not change. On the surgical limb, while peak support moments were lower, the hip contributed less, and the knee contributed more. These asymmetric loading patterns gradually normalized over 1 yea-.

CONCLUSIONS

Asymmetric loading following PAO should be considered when developing rehabilitation plans following this surgery.

In vivo kinematics, component alignment and hardware variables influence on the liner-to-neck clearance during chair-rising after total hip arthroplasty

BACKGROUND

There is an interest in quantifying dynamic hip kinematics before and after total hip arthroplasty (THA) during chair-rising: one of daily life activities.

METHODS

The study consisted of 21 patients who underwent unilateral total hip arthroplasty for symptomatic osteoarthritis. We obtained continuous radiographs using a flat-panel X-ray detector while the participants rose from chair. We assessed the pre and postoperative hip joint's movements using three-dimensional-to-two-dimensional model-to-image registration techniques. We also measured minimum liner-to-neck distances at maximum hip flexion and extension as anterior and posterior liner-to-neck distances, respectively. Multivariate analyses were applied to determine which factors were associated with liner-to-neck distances.

RESULTS

The cup inclination, cup anteversion, and stem anteversion averaged 37.4°, 23.1°, and 30.1°, respectively. Significantly larger maximum hip flexion angle (72°) was found during chair-rising after THA compared to that before THA (63°, P < 0.01). The anterior pelvic tilt at the maximum hip flexion after THA (3° of anterior tilt) was significantly (P < 0.05) anterior compared to that before THA (1° of posterior tilt). The anterior and posterior liner-to-neck distances averaged 12.3 mm and 8.1 mm, respectively, with a significant difference (P < 0.01). No liner-to-neck contact was found in any hips. In multivariate analysis, the hip flexion angle, cup inclination, stem anteversion and head diameter were significantly associated with the anterior liner-to-neck distance (P < 0.05), the hip extension angle, cup anteversion, neck length and with or without elevated rim were significantly associated with the posterior liner-to-neck distance (P < 0.05, 0.01, 0.05, 0.01, respectively).

CONCLUSION

This study indicates that well-positioned THA provide increased range of hip flexion with sufficient anterior liner-to-neck clearance during chair-rising. Dynamic hip kinematics, component position, and hardware variables significantly influenced on the liner-to-neck clearance under weight-bearing conditions.

Raising and stabilization phase of the sit-to-stand movement better discriminate healthy elderly adults from young subjects: a pilot cross-sectional study

Background

The sit-to-stand (STS) test is usually included in the clinical assessment of balance and its instrumented analysis may support clinicians in objectively assessing the risk of falling. The aim of the present study was to assess if kinetic parameters of STS collected using a force platform, with particular focus on the raising and stabilization phase, could discriminate between young and older adults.

Methods

Twenty-four adults (age ranging from 18 to 65 years old) and 28 elderly adults (older than 65 years old) performed STS on a force platform. Data on ground reaction forces, sway, displacement and velocity of the center of pressure were gathered during the raising and the stabilization phases.

Results

elderly subjects showed significant greater global sway (146.97 vs 119.85; p < 0.05) and a higher velocity (vs 40.03 vs 34.35 mm/s; p < 0.05) of execution of STS. Between-group comparisons highlighted a greater postural sway in the raising phase (21.63 vs 13.58; p < 0.001) and a doubled sway during the stabilization phase (12.38 vs 4.98; p < 0.001).

Conclusions

The analysis of STS performed on a force platform provides further information about the age-specific pattern of STS execution. The stabilization phase of STS seems to be the more challenging for functional independent older adults and should be considered during balance assessment.Further studies are needed to confirm findings and improve generalizability of this study.

Functional movement compensations persist in individuals with hip osteoarthritis performing the five times sit-to-stand test 1 year after total hip arthroplasty

Background

Methods to quantify and evaluate function are important for development of specific rehabilitation interventions. This study aimed to evaluate functional movement compensation in individuals with hip osteoarthritis performing the five times sit-to-stand test and change following total hip arthroplasty. To this end, trajectories of the body’s center of mass in the medial-lateral and anterior-posterior dimensions were quantified prior to and 1 year after total hip arthroplasty and compared to a healthy control group.

Methods

Twenty-eight individuals with hip osteoarthritis and 21 matched healthy controls were enrolled in this prospective study. Within 1 month prior to and 1 year after total hip arthroplasty, performance on the five times sit-to-stand test was evaluated using three-dimensional motion analysis and perceived pain using a visual analog scale. The center of mass trajectories for the medial-lateral and the anterior-posterior dimensions were identified, and the area under the curve was calculated, respectively. Repeated measures ANOVA were used to evaluate differences in the area under the curve, between pre- and postoperative performance, and between participants with hip osteoarthritis and controls.

Results

Preoperatively, individuals with hip osteoarthritis displayed a larger contralateral shift (p < 0.001) and forward displacement of the center of mass (p = 0.022) compared to controls. After surgery, deviations in both dimensions were reduced (medial-lateral p = 0.013; anterior-posterior p = 0.009). However, as compared to controls, the contralateral shift of the center of mass remained larger (p = 0.010), indicative of persistent asymmetric limb loading. Perceived pain was significantly reduced postoperatively (p < 0.001).

Conclusions

By quantifying the center of mass trajectory during five times sit-to-stand test performance, functional movement compensations could be detected and evaluated over time. Prior to total hip arthroplasty, individuals with hip osteoarthritis presented with an increased contralateral shift and forward displacement of the center of mass, representing a strategy to reduce pain by unloading the affected hip and reducing required hip and knee extension moments. After surgery, individuals with total hip arthroplasty displayed a persistent increased contralateral shift as compared to controls. This finding has implications for rehabilitation, where more focus must be directed towards normalizing loading of the limbs.

Identifying car ingress movement strategies before and after total knee replacement

Background: Post-operative performance of knee bearings is typically assessed in activities of daily living by means of motion capture. Biomechanical studies predominantly explore common tasks such as walking, standing and stair climbing, while overlooking equally demanding activities such as embarking a vehicle. Aims: The aim of this work is to evaluate changes in the movement habits of patients after total knee arthroplasty surgery in comparison to healthy age-matched control participants. Methods: A mock-up car was fabricated based on the architecture of a common vehicle. Ten control participants and 10 patients with severe osteoarthritis of the knee attended a single- and three-motion capture session(s), respectively. Participants were asked to enter the car and sit comfortably adopting a driving position. Three trials per session were used for the identification of movement strategies by means of hierarchical clustering. Task completion time was also measured. Results: Patients’ movement behaviour didn’t change significantly following total knee arthroplasty surgery. Control participants favoured different movement strategies compared to patients post-operatively. Group membership, height and sidedness of the affected joint were found to be non-significant in task completion time. Conclusion: This study describes an alternative movement identification technique for the analysis of the ingress movement that may be used to clinically assess knee bearings and aid in movement simulations and vehicle design.

Toward clinically-relevant joint moment estimation during sit to stand: a feasibility study

Conventional motion analysis system to measure joint moment during sit to stand is impractical to be used in clinics. Inertial sensor-based motion analysis system has been proposed to improve usability. In this study, we propose a simple system that can predict joint moment, especially maximum joint moment, with a minimum number of an inertial sensor attached and force plate; shank and thigh angles were estimated with a kinematic model and an effective joint moment analysis period. Through a validation experiment with eight subjects, the estimated joint moments were comparable to be actual joint moment measured by the conventional system, also the previous study with the inertial system.

Five-repetition sit-to-Stand test among patients post-stroke and healthy-matched controls: the use of different chair types and number of trials

Background: In 2018, the American Physical Therapy Association (APTA) published a clinical guideline for adults with neurological conditions, which included recommendations for the Five-Repetition Sit-to-Stand test (5STSt). According to the APTA, a standard-height chair should be used, but there is no recommendation regarding seat depth. In addition, the APTA recommended the use of one trial of the test, based on expert opinion.Objectives: (1) Compare the 5STSt scores of patients post-stroke and healthy-matched controls using two types of chairs (one standardized and one adjusted to the individual's anthropometric characteristics); and (2) Verify whether different numbers of trial affect the 5STSt scores.Methods: Eighteen patients post-stroke and 18 healthy-matched controls performed three trials of the 5STSt for each type of chair. ANOVA was used for analysis (α = 0.05).Results: No significant interaction between groups and chairs was found. Patients post-stroke showed worsened performances in 5STSt when using both chairs compared to the healthy controls (p = .001). In both groups, the 5STSt scores were lower when using a standardized chair than an adjusted chair (p < .003) and different numbers of trials provided similar 5STSt scores (0.44 ≤ p ≤ 0.98).Conclusion: The 5STSt scores were affected by the physical characteristics of the chair, and an adjusted chair should be used. The APTA recommendation for one trial of the 5STSt is supported by the present results.

Individuals with mild-to-moderate hip osteoarthritis exhibit altered pelvis and hip kinematics during sit-to-stand

BACKGROUND

Performance of the sit-to-stand (STS) task is compromised in individuals with advanced hip osteoarthritis (OA). Understanding how STS performance is altered in individuals with mild-to-moderate hip OA may inform interventions to improve function and slow disease progression.

RESEARCH QUESTION

Do trunk, pelvis, and hip biomechanics differ during a STS task between individuals with mild-to-moderate hip OA and a healthy, age-matched control group?

METHODS

Thirteen individuals with mild-to-moderate symptomatic and radiographic hip OA and seventeen healthy, age-matched controls performed a standardized STS task. Data were acquired using a three-dimensional motion capture system. The primary outcome measures were task duration, sagittal and frontal plane trunk, pelvis, and hip joint angles, and sagittal and frontal plane trunk and hip joint moments. Comparisons of lower-limb measures were between the most affected side in the hip OA group and a randomly chosen limb for the control group, termed the index limb, prior to and following lift-off from the chair.

RESULTS

Participants with mild-to-moderate hip OA took longer to perform the STS task compared to controls. Prior to lift-off, the hip OA group exhibited greater posterior pelvic tilt, greater pelvic rise on the index side and less hip joint flexion relative to controls. Following lift-off, the hip OA group exhibited greater pelvic rise on the index side compared to controls.

SIGNIFICANCE

Individuals with mild-to-moderate hip OA exhibit subtle alterations in movement strategy compared to healthy controls when completing a STS task similar, to a small extent, to adaptations reported in advanced stages of the disease. Interventions to target these features and prevent further decline in physical function may be warranted in the management of mild-to-moderate hip OA while the opportunity remains.

Patients with sacroiliac joint dysfunction exhibit altered movement strategies when performing a sit-to-stand task

OF BACKGROUND DATA

The ability to rise from a chair is a basic functional task that is frequently compromised in individuals diagnosed with orthopedic disorders in the low back and hip. There is no published literature that describes how this task is altered by sacroiliac joint dysfunction (SIJD).

PURPOSE

The objective of this study was to compare lower extremity biomechanics and the onset of muscle activity when rising from a chair in subjects with SIJD and in healthy persons.

STUDY DESIGN

Six women with unilateral SIJD and six age-matched healthy controls performed a sit-to-stand task while we measured kinematics, kinetics, and muscle activity.

MATERIALS AND METHODS

Subjects stood up at a preferred speed from a seated position on an armless and backless adjustable stool. We measured kinematics with a 10-camera motion capture system, ground reaction forces for each leg with force plates, and muscle activity with surface electromyography. Joint angles and torques were calculated using inverse dynamics. Leg-loading rate was quantified as the average slope of vertical ground reaction (VGRF) force during the 500-millisecond interval preceding maximal knee extension.

RESULTS

Between-leg differences in loading rates and peak VGRFs were significantly greater for the SIJD group than for the control group. Maximal hip angles were significantly less for the SIJD group (p=.001). Peak hip moment in the SIJD group was significantly greater in the unaffected leg (0.75±0.22 N⋅m/kg) than in the affected leg (0.47±0.29 N⋅m/kg, p=.005). There were no between-leg or between-group differences for peak knee or ankle moments. The onset of activity in the latissimus dorsi muscle on the affected side was delayed and the erector spinae muscles were activated earlier in the SIJD group than in the control group.

CONCLUSIONS

Subjects with SIJD have a greater VGRF on the unaffected leg, generate a greater peak hip moment in the unaffected leg, use a smaller range of motion at the hip joint of the affected leg, and delay the onset of a key muscle on the affected side when rising from a seated position.

Quantification of the sit-to-stand movement for monitoring age-related motor deterioration using the Nintendo Wii Balance Board

Simple methods for quantitative evaluations of individual motor performance are crucial for the early detection of motor deterioration. Sit-to-stand movement from a chair is a mechanically demanding component of activities of daily living. Here, we developed a novel method using the ground reaction force and center of pressure measured from the Nintendo Wii Balance Board to quantify sit-to-stand movement (sit-to-stand score) and investigated the age-related change in the sit-to-stand score as a method to evaluate reduction in motor performance. The study enrolled 503 participants (mean age ± standard deviation, 51.0 ± 19.7 years; range, 20-88 years; male/female ratio, 226/277) without any known musculoskeletal conditions that limit sit-to-stand movement, which were divided into seven 10-year age groups. The participants were instructed to stand up as quickly as possible, and the sit-to-stand score was calculated as the combination of the speed and balance indices, which have a tradeoff relationship. We also performed the timed up and go test, a well-known clinical test used to evaluate an individual's mobility. There were significant differences in the sit-to-stand score and timed up and go time among age groups. The mean sit-to-stand score for 60s, 70s, and 80s were 77%, 68%, and 53% of that for the 20s, respectively. The timed up and go test confirmed the age-related decrease in mobility of the participants. In addition, the sit-to-stand score measured using the Wii Balance Board was compared with that from a laboratory-graded force plate using the Bland-Altman plot (bias = -3.1 [ms]-1, 95% limit of agreement: -11.0 to 3.9 [ms]-1). The sit-to-stand score has good inter-device reliability (intraclass correlation coefficient = 0.87). Furthermore, the test-retest reliability is substantial (intraclass correlation coefficient = 0.64). Thus, the proposed STS score will be useful to detect the early deterioration of motor performance.

Influence of weight bearing visual feedback on movement symmetry during sit to stand task

BACKGROUND

Weight-bearing asymmetry is common in individuals with hip osteoarthritis and after total hip arthroplasty. Including symmetry training to the rehabilitation programs may normalize movement strategies during dynamic tasks. The purpose of this study was to evaluate the immediate influences of real-time visual feedback of weight distribution on the interlimb movement symmetry during the sit-to-stand task, before and after total hip arthroplasty, and to determine whether physical impairments affect the response to visual feedback.

METHODS

Subjects before and after total hip arthroplasty participated in three- dimensional motion analysis. Subjects completed 3 trials of sit-to-stand task in two conditions; "without visual feedback" and "with visual feedback". Outcome measures were the interlimb symmetry of vertical ground reaction force, and joint kinematics and kinetics. Pain and strength of lower limbs were assessed.

FINDINGS

Compared to "without visual feedback" condition, subjects moved with greater symmetry of vertical ground reaction force and joint kinetics when visual feedback was received. However, subjects continued to demonstrate interlimb difference for joint kinetics and vertical ground reaction force in the visual feedback condition. The increase in symmetry was not strongly influenced by physical impairments and subjects before and after total hip arthroplasty responded similarly to the feedback.

INTERPRETATIONS

We concluded that in a single session, the visual feedback of weight bearing distribution had a positive immediate effect on movement symmetry during the sit-to-stand task. Future studies that assess long-term retention and functional benefits are warranted before visual feedback is incorporated in rehabilitation for this patient population.

Vertical ground reaction force marker for Parkinson's disease

Parkinson’s disease (PD) patients regularly exhibit abnormal gait patterns. Automated differentiation of abnormal gait from normal gait can serve as a potential tool for early diagnosis as well as monitoring the effect of PD treatment. The aim of current study is to differentiate PD patients from healthy controls, on the basis of features derived from plantar vertical ground reaction force (VGRF) data during walking at normal pace. The current work presents a comprehensive study highlighting the efficacy of different machine learning classifiers towards devising an accurate prediction system. Selection of meaningful feature based on sequential forward feature selection, the swing time, stride time variability, and center of pressure features facilitated successful classification of control and PD gaits. Support Vector Machine (SVM), K-nearest neighbor (KNN), random forest, and decision trees classifiers were used to build the prediction model. We found that SVM with cubic kernel outperformed other classifiers with an accuracy of 93.6%, the sensitivity of 93.1%, and specificity of 94.1%. In comparison to other studies, utilizing same dataset, our designed prediction system improved the classification performance by approximately 10%. The results of the current study underscore the ability of the VGRF data obtained non-invasively from wearable devices, in combination with a SVM classifier trained on meticulously selected features, as a tool for diagnosis of PD and monitoring effectiveness of therapy post pathology.

A SIX-WEEK SUPERVISED EXERCISE AND EDUCATIONAL INTERVENTION AFTER TOTAL HIP ARTHROPLASTY: A CASE SERIES

BACKGROUND AND PURPOSE

Most rehabilitation interventions after total hip arthroplasty (THA) are not designed to return patients to high-levels of physical activity and, thus, low levels of physical activity and residual weakness are common. The purpose of this case series was to describe the feasibility and preliminary efficacy of an exercise and education intervention for patients after THA who have already completed formal outpatient physical therapy.

STUDY DESIGN

Case series.

CASE DESCRIPTION

Two participants underwent unilateral THA seven (case A) or eight (case B) months prior to the intervention. Individuals participated in 18 treatment sessions that included progressive aerobic and strengthening exercises and meetings with a health coach. Change in function, strength, and self-reported physical activity were measured. Outcomes 12 months after surgery were compared to a historical cohort of patients after THA.

OUTCOME

There were no adverse events during the intervention. At the end of the intervention, hip and knee strength on the surgical side increased approximately 30% compared to baseline in both cases. Activity level, and recreational performance, including walking up stairs and hiking uphill (case A), and running and golfing (case B), improved by the end of the intervention. Most changes were maintained at follow-up, although hip strength for case B decreased 27% after discharge from the intervention. Outcomes for both cases exceeded historical averages for patients 12 months after THA, with the exception of strength in case B.

DISCUSSION

The exercise intervention was well tolerated and without negative effects in two participants. Both participants increased their ability to complete demanding recreational and sports-related activities, physical activity, and demonstrated improved hip abductor and knee extensor strength. Further research is needed to evaluate the implementation and effectiveness of similar interventions after THA.

LEVEL OF EVIDENCE

Level 4.

Abnormal Joint Moment Distributions and Functional Performance During Sit-to-Stand in Femoroacetabular Impingement Patients

BACKGROUND

Femoroacetabular impingement (FAI) is a morphological abnormality of the hip joint that causes pain when performing a mechanically demanding activity of daily living such as the sit-to-stand (STS) task. Previous studies have assessed lower extremity joint mechanics during an STS task in various pathologies, yet the STS task has not been studied in FAI patients.

OBJECTIVE

The objective of this study was to identify differences in joint kinetics and performance between FAI patients and healthy controls during a STS task. It was hypothesized that FAI patients would exhibit altered time needed to complete the STS task, as well as altered lower extremity biomechanics, when compared to healthy controls.

DESIGN

This was a cross-sectional cohort study.

SETTING

The study took place at a motion capture laboratory at an institutional orthopedic facility.

PARTICIPANTS

Biomechanical analysis was performed in 17 FAI patients and 31 age- and body mass index (BMI)-matched healthy controls during the STS task.

METHODS

Sagittal plane joint moments, total support moment (TSM), joint contributions to the TSM, and functional measures during the STS task were compared between groups.

MAIN OUTCOME MEASUREMENTS

Peak joint moments, TSM and joint contributions to the TSM were assessed during the STS task. In addition, the time to and value of the peak vertical ground reaction force (vGRF), limb symmetry index at peak vGRF, loading rate, and total time needed to perform the STS task were determined.

RESULTS

Compared to the control participants, the FAI patients exhibited worse Hip Disability and Osteoarthritis Outcome Score (HOOS) pain and function subscores. No group differences were observed in peak sagittal joint moments during the STS task. However, when compared to controls, the FAI patients demonstrated reduced knee joint contributions to the TSM. In addition, the FAI patients exhibited increased time needed to perform the STS task, increased time to reach peak vGRF, and reduced lower extremity loading rate during the STS task.

CONCLUSIONS

FAI patients demonstrated abnormal joint contributions to TSM and altered functional performance during the STS task. These altered movement patterns during the STS task may be compensatory mechanisms used by the FAI patients to reduce pain and to improve function.

LEVEL OF EVIDENCE

Not applicable.

Quadriceps strength asymmetry predicts loading asymmetry during sit-to-stand task in patients with unilateral total knee arthroplasty

PURPOSE

This study aimed to examine interlimb differences in muscle strength and sit-to-stand (STS) kinetics in persons who underwent unilateral total knee arthroplasty (TKA) and to determine whether knee pain, quadriceps or hip abductor weakness contributes to altered STS performance. It was hypothesized that the operated limb would have weaker muscles, lower mechanical loading and that operated knee pain and muscle strength symmetry would predict loading symmetry between limbs during STS.

METHODS

One hundred and forty-two patients, 6 or 12 months post-unilateral TKA, underwent 3D motion analysis (VICON) of the STS task and isometric strength testing of the quadriceps and hip abductors. Knee pain was also quantified using a question from the Knee Outcome Survey-Activities of Daily Living Scale.

RESULTS

The operated limb had weaker quadriceps (P < 0.001), lower hip (P = 0.004) and knee extension moments (P < 0.001), and lower vertical ground reaction forces (P < 0.001). Operated knee pain and quadriceps strength symmetry were related to symmetry in knee extension moment (P < 0.04), and vertical ground reaction forces (P < 0.02) 6 months after surgery, while quadriceps strength symmetry was related to symmetry in vertical ground reaction forces (P = 0.03), 1 year after surgery.

CONCLUSION

Patients with unilateral TKA unload the operated limb and shift the mechanical load to the joints of the contralateral limb even 1 year after surgery. Knee pain and quadriceps strength asymmetry may play a role in the asymmetrical loading during STS post-TKA. Clinicians should consider addressing these modifiable impairments to resolve the loading asymmetry.

LEVEL OF EVIDENCE

III.

Examination of Inertial Sensor-Based Estimation Methods of Lower Limb Joint Moments and Ground Reaction Force: Results for Squat and Sit-to-Stand Movements in the Sagittal Plane

Joint moment estimation by a camera-based motion measurement system and a force plate has a limitation of measurement environment and is costly. The purpose of this paper is to evaluate quantitatively inertial sensor-based joint moment estimation methods with five-link, four-link and three-link rigid body models using different trunk segmented models. Joint moments, ground reaction forces (GRF) and center of pressure (CoP) were estimated for squat and sit-to-stand movements in the sagittal plane measured with six healthy subjects. The five-link model and the four-link model that the trunk was divided at the highest point of the iliac crest (four-link-IC model) were appropriate for joint moment estimation with inertial sensors, which showed average RMS values of about 0.1 Nm/kg for all lower limb joints and average correlation coefficients of about 0.98 for hip and knee joints and about 0.80 for ankle joint. Average root mean square (RMS) errors of horizontal and vertical GRFs and CoP were about 10 N, 15 N and 2 cm, respectively. Inertial sensor-based method was suggested to be an option for estimating joint moments of the trunk segments. Inertial sensors were also shown to be useful for the bottom-up estimation method using measured GRFs, in which average RMS values and average correlation coefficients were about 0.06 Nm/kg and larger than about 0.98 for all joints.