Postural Stability Characteristics Research Articles

Smartphone-Based Prediction Model for Postoperative Cardiac Surgery Outcomes Using Preoperative Gait and Posture Measures.

Gait speed assessment increases the predictive value of mortality and morbidity following older adults’ cardiac surgery. The purpose of this study was to improve clinical assessment and prediction of mortality and morbidity among older patients undergoing cardiac surgery through the identification of the relationships between preoperative gait and postural stability characteristics utilizing a noninvasive-wearable mobile phone device and postoperative cardiac surgical outcomes. This research was a prospective study of ambulatory patients aged over 70 years undergoing non-emergent cardiac surgery. Sixteen older adults with cardiovascular disease (Age 76.1 ± 3.6 years) scheduled for cardiac surgery within the next 24 h were recruited for this study. As per the Society of Thoracic Surgeons (STS) recommendation guidelines, eight of the cardiovascular disease (CVD) patients were classified as frail (prone to adverse outcomes with gait speed ≤0.833 m/s) and the remaining eight patients as non-frail (gait speed >0.833 m/s). Treating physicians and patients were blinded to gait and posture assessment results not to influence the decision to proceed with surgery or postoperative management. Follow-ups regarding patient outcomes were continued until patients were discharged or transferred from the hospital, at which time data regarding outcomes were extracted from the records. In the preoperative setting, patients performed the 5-m walk and stand still for 30 s in the clinic while wearing a mobile phone with a customized app “Lockhart Monitor” available at iOS App Store. Systematic evaluations of different gait and posture measures identified a subset of smartphone measures most sensitive to differences in two groups (frail versus non-frail) with adverse postoperative outcomes (morbidity/mortality). A regression model based on these smartphone measures tested positive on five CVD patients. Thus, clinical settings can readily utilize mobile technology, and the proposed regression model can predict adverse postoperative outcomes such as morbidity or mortality events.

Recurrence Quantitative Analysis of Postural Sway using Force Plate and Smartphone

Although modern medicine and new medical technologies offer enormous potential to improve diagnosis and treatment of many diseases, mortalities from fall accidents are steadily on the rise for the elderly. Since postural stability characteristics are considered to be important in maintaining functional independence free of falls and healthy life style especially for the growing elderly population, there is an imminent need in inexpensive and portable device that can assess balance. While inertial sensors embedded in smartphone are seen as an alternative to force plate (ground truth) to unobtrusively assess postural stability in home environments, no study has yet reported the non-linear physiological information captured by smartphone affixed at pelvic region. By using recurrence quantitative analysis (RQA), this study investigates non-linear dynamical features of postural sway measured from force plate and smartphone. The resultant position vector of postural sway from the two systems was highly coherent and was used for non-linear analysis. Even though most of RQA measures collected from the projected postural sway using the smartphone were significantly different than measures collected using the force plate, deterministic characteristics of postural sway were not found significantly different. This study opens new prospects of easy clinical testing using postural variables that may be relevant for assessing fall risks at home and patient environment in future.

The effects of a high-intensity free-weight back-squat exercise protocol on postural stability in resistance-trained males

The purpose of this study was to investigate the effects of a high-intensity free-weight back-squat exercise on postural stability characteristics in resistance-trained males. Eighteen college-aged (mean ± SD: age = 22.9 ± 2.9 years; height = 175.8 ± 6.4 cm; mass = 86.3 ± 9.3 kg), resistance-trained males performed postural stability testing before and after completing five sets of eight repetitions of back-squat exercises at 80% of one-repetition maximum. A commercial balance testing device was used to assess sway index at pre- and at 0, 5, 10, 15 and 20 min post-exercise. Each balance assessment consisted of four, 20-s static stance conditions: eyes-open firm surface, eyes-closed firm surface, eyes-open soft surface and eyes-closed soft surface. Sway index was greater (P = 0.001–0.020) at Post 0 than at all other time points. No differences (P > 0.05) were observed between any other time phases. Sway index was greater (P < 0.001) for eyes-closed soft surface than all other conditions. These findings revealed sway index for all conditions significantly increased following completion of the back-squat; however, sway index recovered within 5 min of exercise. Higher sway index values as a result of neuromuscular fatigue induced by a back-squat exercise may have performance and injury risk consequences to subsequent activities that rely on postural stability. However, these findings suggest balance impairments may recover in ~5 min following high-intensity lower body resistance exercise.

Postural stability in relation to anthropometric and functional characteristics in women with knee osteoarthritis following total knee arthroplasty

Due to the controversial information about postural stability in patients with lower limb joints osteoarthritis (OA), the following main questions are raised: how serious is the postural stability disturbance and which factors have an impact on postural stability before and after total knee arthroplasty (TKA). Force plate was used to assess postural stability and custom-made dynamometer was used to assess isometric maximal voluntary contraction (MVC) force of leg extensor muscles; besides, knee pain and knee range of motion (ROM) was evaluated in 14 female patients (aged 46-68years) with knee OA 1day before, and 3 and 6months following TKA and once in healthy controls (aged 48-70). Relationship between postural stability during standing and selected anthropometric and functional characteristics were investigated with Spearman's correlation coefficients. Remarkable reduction of knee pain and improvement in active ROM for the operated leg were shown after unilateral TKA. MVC force of leg extensor muscles achieved the preoperative level half a year after TKA. The centre of pressure (COP) of sway displacement in anterioposterior (AP) and mediolateral direction and the equivalent area of COP sway for the operated leg did not differ before, 3 and 6months after TKA and compared to the non-operated leg. The trace speed was 6months after TKA equal to the preoperative level. Only the COP of sway displacement in AP direction is significantly greater in knee OA patients both before and after TKA compared with healthy controls. Knee OA patients' postural stability characteristics did not differ significantly both before and after TKA. Compared to healthy controls, the COP of sway displacement in AP direction is mostly disturbed. Correlation analysis confirms that increased postural sway is associated with an increased equivalent area of COP. In knee OA patients higher body mass index ensures reduced trace speed and lower knee ROM. Prospective comparative study, Level II.

Leg Extensor Muscle Strength, Postural Stability, and Fear of Falling After a 2-Month Home Exercise Program in Women With Severe Knee Joint Osteoarthritis

BACKGROUND AND OBJECTIVE. The aim of this study was to compare the leg extensor muscle strength, the postural stability, and the fear of falling in the women with severe knee joint osteoarthritis (OA) before and after a 2-month home exercise program (HEP). MATERIAL AND METHODS. In total, 17 women aged 46-72 years with late-stage knee joint OA scheduled for total knee arthroplasty participated in this study before and after the 2-month HEP with strengthening, stretching, balance, and step exercises. The isometric peak torque (PT) of the leg extensors and postural stability characteristics when standing on a firm or a foam surface for 30 seconds were recorded. The fear of falling and the pain intensity (VAS) were estimated. RESULTS. A significant increase in the PT and the PT-to-body weight (PT-to-BW) ratio of the involved leg as well as the bilateral PT and the PT-to-BW ratio was found after the 2-month HEP compared with the data before the HEP (P<0.05). The PT and the PT-to-BW ratio of the involved leg were significantly lower compared with the uninvolved leg before the HEP (P<0.05). The center of the pressure sway length (foam surface) decreased significantly after the HEP (P<0.05). Significant correlations were found between the PT of the involved leg and the bilateral PT and the fear of falling and between the PT of the involved leg and the postural sway (foam surface) before the HEP. CONCLUSIONS. After the 2-month HEP, the leg extensor muscle strength increased and the postural sway length on a foam surface decreased. The results indicate that the increased leg extensor muscle strength improves postural stability and diminishes the fear of falling in women with late-stage knee joint OA.

Knee pain and postural stability in women with gonarthrosis before and six months after unilateral total knee replacement

The aim of this study was to investigate knee pain and postural stability in women with knee osteoarthritis (OA), who used postoperative home exercise program (HEP) with balance exercises. 14 women with knee OA in stage III–IV (aged 48–70 years) participated in this study before and 6 months after unilateral total knee arthroplasty (TKA). All patients performed HEP during 6 months after unilateral TKA. Data of patients was compared with healthy age-matched women (controls, n=10). Postural stability characteristics (centre of pressure (COP) displacement in the anterior-posterior (AP) and mediolateral (ML) direction, COP sway equivalent radius and area) during 30 s bipedal standing (eyes open) were recorded on two dynamographic force plates. Pain in knee joint was estimated with visual-analogue scale. COP displacement in AP direction of the operated and non-operated leg was greater (p<0.05) in women with knee OA before and 6 months after TKA compared to the controls. Knee joint pain in the operated leg reduced 70% after TKA. TKA together with HEP has an important role in preserving postural stability and reducing knee joint pain in women with III–IV stage gonarthrosis.

Postural control in total knee arthroplasty patients with patellofemoral pain syndrome before and six months after re‐operation

Background Although excellent long-term clinical results have been reported for the total knee arthroplasty (TKA), 37% of patients have limited functional improvement one year after the surgery [1]. Patients with a clinical presentation of anterior knee pain could be diagnosed with patellofemoral pain syndrome (PFPS). Modified clinical classification of PFPS patients includes two main groups: with malalignment and with muscular dysfunction [2]. The aim of the study was to compare postural stability characteristics in TKA patients with PFPS before and six months after re-operation.

Evaluation of postural stability during quiet standing, step-up and step-up with lateral perturbation in subjects with and without low back pain.

The evaluation of postural stability during quiet stance, step up and step up task with perturbation using posturography could be useful in treatment and outcome monitoring in chronic low back pain rehabilitation (CLBP). The aims of this study were twofold and investigating 1) differences of postural stability measures between CLBP patients and healthy participants during above mentioned tasks. 2) postural stability characteristics between control and movement impairment groups of CLBP patients on above tasks. Fourteen CLBP and fifteen normal individuals participated and posturography outcome variables were obtained during above tasks. The low back pain subjects showed significantly different anterior-posterior (p=0 .01) as well as medio- lateral (p=0.05) postural stability characteristics during the step up task with external perturbation, whereas quiet standing and simple step up task did not show any differences. In addition to these values, in CLBP population, the maximum COP excursion (p=0.01), standard stability (p=0.02) and the stability scores (p=0.02) were also found significant in step up with perturbation task compared to healthy participants. As the task difficulty increases CLBP patients exhibited significantly different postural stability characteristics compared to healthy participants. Conversely, sub-group analysis in CLBP patients revealed significant differences only in medio-lateral COP excursions during normal standing (p=0.005). No significant differences were observed in tasks of higher difficulties such as step up and step up task with lateral perturbation in-between patients with movement and control impairment groups of CLBP. These findings have implications for assessment and optimizing postural control interventions on functional back pain rehabilitation.

Balance in lower limb child amputees.

Postural stability of five unilateral above-knee amputee children was measured when wearing the SACH and the experimental Child Amputee Prosthetic Project (CAPP) prosthetic foot. Excursions of the centre of pressure of the supportive forces were recorded via force platform during sustained weight-shifting forward, backward, left, right, and during normal standing. Visual proprioception effects on upright stance were also demonstrated with these child amputees. Total base of support did not differ for the two types of prosthetic feet, but the functional base of support for SACH foot was significantly larger than CAPP. Fluctuations of centre of pressure about a mean position in normal standing were less when children used CAPP foot. Focusing on a static target had no effect on postural stability in either anterior-posterior or lateral direction for CAPP foot conditions, but lack of visual target had a deleterious effect on lateral stability when SACH foot was worn. Balance is one of the most difficult problems for a lower limb amputee (Hellebrandt et al, 1950; Moncur, 1969; Murdoch, 1969). The absence of part or all of a lower limb reduces the amount of proprioceptive information about the surfaces on which the foot is resting and the precise location of the prosthetic limb. While limited data have been reported on the balance and stability characteristics of adult amputees (Fernie and Holliday, 1978; Hellebrandt et al, 1950), information about balance of child amputees is almost non-existent. We have found only one report of the postural stability characteristics of a child amputee; Shambes and Waterland (1970) studied an 11-year-old quadrilateral amputee who had congenital Lisfranc amputations of both lower limbs, long above-elbow amputation of the left upper limb, and medium below-elbow amputation of the right upper limb. The purpose of this study was to detail the postural stability characteristics for lower limb child amputees. In addition, the conventional SACH prosthetic foot was compared with the experimental Child Amputee Prosthetic Project (CAPP) foot for various postural tasks. The SACH foot (Fig. la) is usually constructed with a moulded polyurethane material which incorporates a heel cushion to allow some compression of the heel during heel strike in walking to simulate plantar flexion of a normal foot. The CAPP foot (Fig. lb) is an experimental prosthesis undergoing development at the UCLA Child Amputee Prosthetic Project. It is designed to provide more knee stability during early stance phase during walking and also to respond to torsional loads occurring in the stance phase of walking. The heel projection of the CAPP foot is non-weight bearing and deflects upward at heelstrike. With the ground reaction forces shifted more anteriorly on the supporting foot there is an expected increase in dynamic knee stability during the stance phase of walking. While additional research is being conducted on the dynamic characteristics of the CAPP foot, the present study provides some preliminary information about the postural stability of child amputees using the experimental CAPP foot, as well as providing a comparison with the conventional SACH foot.