Persisting inter-limb differences in patients following total hip arthroplasty four to five years after surgery? A preliminary cross-sectional study.

BACKGROUND: Total hip arthroplasty (THA) is an effective procedure for patients with end-stage hip osteoarthritis. However, whether or not pre-operatively existing functional deficits are persisting several years post-surgery in the affected limb has not been thoroughly researched. Therefore, the primary aim of this preliminary study was to include patients four to five years after undergoing THA and to investigate potential differences between the operated and non-operated leg in hip strength, range of motion (ROM), balance, and gait. The secondary aim was to compare these values from the operated leg of the patients to those of the legs of healthy subjects. METHODS: Sixteen patients (age: 65.20 ± 5.32 years) following unilateral THA (post-operation time: 4.7 ± 0.7 years) and ten, healthy, age-matched control subjects (age: 60.85 ± 7.57 years) were examined for maximum isometric hip muscle strength, active ROM of the hip joint, balance and gait on both limbs. Paired t-tests were used to assess the inter-limb differences in the THA group. Analyses of covariance (ANCOVA) were performed to compare groups, using age as a covariate. RESULTS: The analysis of inter-limb differences in patients following THA revealed significant deficits on the operated side for hip abduction strength (p = 0.02), for hip flexion ROM (p < 0.01) and for balance in terms of the length of center of pressure (COP) (p = 0.04). Compared to values of the control subjects, the patients demonstrated significantly reduced hip strength in flexion, extension and abduction (p < 0.05) on the operated leg as well as reduced ROM measures in hip flexion, extension and abduction (p < 0.05). CONCLUSIONS: The first results of this explorative study indicated that inter-limb differences as well as reduced hip strength and hip ROM compared with control subjects were still present four to five years after THA. These persisting asymmetries and deficits in patients following THA may be one explanation for the decrease in health-related quality of life (HRQoL) seen in patients over the years after surgery. Further studies are required to replicate these findings with a larger sample size. TRIAL REGISTRATION: DRKS, DRKS00016945. Registered 12 March 2019 - Retrospectively registered.

Cortical activation during balancing on a balance board.

BACKGROUND: Keeping one's balance is a complex motor task which requires the integration and processing of different sensory information. For this, higher cortical processes are essential. However, in the past research dedicated to the brain's involvement in balance control has predominantly used virtual reality paradigms whilst little is known about cortical activation during the challenging balancing on unstable surfaces (e.g. balance board). Hence, the main goal of this study was the simultaneous evaluation of cortical activation patterns and sway parameters during balancing on a balance board. METHODS: Ten healthy adults were instructed to balance on a balance board while brain activation in supplementary motor area (SMA), precentral gyrus (PrG) and postcentral gyrus (PoG) was measured with functional near-infrared spectroscopy (fNIRS). Additionally, sway parameters were simultaneously recorded with one inertial sensor. RESULTS: Enhanced activation of SMA, PrG and PoG was observed when balancing was compared with still standing. Furthermore, the sway of pelvis (indicated by root mean square) increased in medio-lateral (ML) and anterior-posterior (AP) direction during the balance condition. Notably, a strong negative correlation was found between SMA activation and sway in ML direction during balancing, which was not observed during standing. CONCLUSION: Our results underline the important role of sensorimotor cortical areas for balance control. Moreover, the observed correlations suggest a crucial involvement of SMA in online control of sway in ML direction. Further research is needed to understand the contribution of other cortical and subcortcial areas to online balance control.

Examination of the reliability of an inertial sensor-based gait analysis system.

Gait analysis is an important and useful part of the daily therapeutic routine. InvestiGAIT, an inertial sensor-based system, was developed for using in different research projects with a changing number and position of sensors and because commercial systems do not capture the motion of the upper body. The current study is designed to evaluate the reliability of InvestiGAIT consisting of four off-the-shelf inertial sensors and in-house capturing and analysis software. Besides the determination of standard gait parameters, the motion of the upper body (pelvis and spine) can be investigated. Kinematic data of 25 healthy individuals (age: 25.6±3.3 years) were collected using a test-retest design with 1 week between measurement sessions. We calculated different parameters for absolute [e.g. limits of agreement (LoA)] and relative reliability [intraclass correlation coefficients (ICC)]. Our results show excellent ICC values for most of the gait parameters. Midswing height (MH), height difference (HD) of initial contact (IC) and terminal contact (TC) and stride length (SL) are the gait parameters, which did not exhibit acceptable values representing absolute reliability. Moreover, the parameters derived from the motion of the upper body (pelvis and spine) show excellent ICC values or high correlations. Our results indicate that InvestiGAIT is suitable for reliable measurement of almost all the considered gait parameters.