Weight-shifting-based robot control system improves the weight-bearing rate and balance ability of the static standing position in hip osteoarthritis patients: a randomized controlled trial focusing on outcomes after total hip arthroplasty

Background

After a total hip arthroplasty (THA), standing and walking balance are greatly affected in the early stages of recovery, so it is important to increase the weight-bearing amount (WBA) on the operated side. Sometimes, traditional treatments may not be enough to improve WBA and weight-bearing ratio (WBR) on the operated side in a satisfactory way. To solve this problem, we came up with a new weight-shifting-based robot control system called LOCOBOT. This system can control a spherical robot on a floor by changing the center of pressure (COP) on a force-sensing board in rehabilitation after THA. The goal of this study was to find out how rehabilitation with the LOCOBOT affects the WBR and balance in a static standing position in patients with unilateral hip osteoarthritis (OA) who had a primary uncemented THA.

Methods

This randomized controlled trial included 20 patients diagnosed with Kellgren-Lawrence (K-L) grade 3 or 4 hip OA on the operative side and K-L grade 0 normal hip on the nonoperative side. We used the minimization method for allocation and randomly assigned patients to either the LOCOBOT group or the control group. As a result, 10 patient seach were randomly assigned to the LOCOBOT and control groups. Both groups received 40 min of rehabilitation treatment. Out of the 40 min, the LOCOBOT group underwent treatment for 10 min with LOCOBOT. The control group performed COP-controlled exercises on a flat floor instead of using LOCOBOT for 10 of the 40 min. All theoutcome measures were performed pre-THA and 11.9 ± 1.6 days after THA (12 days after THA). The primary outcome measure included WBR in the static standing position.

Results

After12 days of THA, the LOCOBOT group exhibited significantly higher mean WBR and WBA (operated side) values than the control group. Furthermore, the LOCOBOT group exhibited significantly lower mean WBA (non-operated side) and outer diameter area (ODA) values than the control group. From pre-THA to 12 days after THA, the LOCOBOT group exhibited a significant improvement in mean WBR and WBA (operated side). Moreover, the mean WBA (non-operated side) and ODA significantly decreased. From pre-THA to 12 days after THA, the control group showed a significant increase in total trajectory length and ODA.

Conclusions

The most important finding of this study was that patients were able to perform the LOCOBOT exercise as early as the second day after THA, and that WBR and ODA significantly improved by the 12th day after THA. This result demonstrated that the LOCOBOT effectively improves WBR in a short period of time after THA and is a valuable system for enhancing balance ability. This expedites the acquisition of independence in activities of daily living after THA and may contribute to optimizing the effectiveness of medical care.

The effect of foot position during static calibration trials on knee kinematic and kinetics during walking

BACKGROUND

Gait analysis has been used extensively for computing knee kinematics and kinetics, in particular, in healthy and impaired individuals. One variable assessed is the external knee adduction moment (EKAM). Variations in EKAM values between investigations may be caused by changes in static standing position, especially foot placement angles which may increase or reduce any differences seen.

PURPOSE OF THE STUDY

The current study aimed to explore the influence of static trial foot position on knee kinematic and kinetic variables during walking.

METHODS

Twelve healthy male participants completed three different static standing trials; 1) 20-degrees toe-in, 2) 0° and 3) 20-degrees toe-out before walking at their own pace during a lower limb kinematics and kinetics assessment. First and second peak EKAM was compared between static foot position trials, as well other knee kinematic and kinetic outcomes. Repeated measures ANOVA was used with post hoc pairwise comparison to determine the differences between static foot position trials.

RESULTS

The first peak of EKAM was significantly smaller in the 20^o toe-out angle, than the 20^o toe-in angle (p = 0.04-8.16% reduction). Furthermore, significant changes were found in peak knee kinematics and kinetics variables (adduction angle, external rotation angle, knee flexion moment external rotation moment, abduction angle and internal rotation angle) in the different positions.

CONCLUSION

Modification in static foot position between study visits may result in changes especially in the 1st peak EKAM and other kinematics and kinetics variables during walking. Therefore, standardisation of static foot position should be utilised in longitudinal studies to ensure changes in EKAM are not masked or accentuated between assessments.