Validation of inertial measurement units with optical tracking system in patients operated with Total hip arthroplasty

Patient reported outcome measurement (PROMs) will not capture in detail the functional joint motion before and after total hip arthroplasty (THA). Therefore, methods more specifically aimed to analyse joint movements may be of interest. An analysis method that addresses these issues should be readily accessible and easy to use especially if applied to large groups of patients, who you want to study both before and after a surgical intervention such as THA. Our aim was to evaluate the accuracy of inertial measurement units (IMU) by comparison with an optical tracking system (OTS) to record pelvic tilt, hip and knee flexion in patients who had undergone THA.This article is freely available via Open Access. Click on the Publisher's URL to access the full-text

Gait and motion analysis of hip arthroplasty. Validity, reliability and longterm results

Introduction: Walking is one of the most fundamental activities of daily living in humans, when the hip joints transfer power between the lower extremities and the pelvis. Hip osteoarthritis (OA) will more or less influence this function and is increasing in an ageing population. Total hip arthroplasty (THA) is a common treatment for patients diagnosed with hip osteoarthritis when non-surgical treatments have failed. Optical tracking systems (OTS) based on cameras and force plates mounted in the floor have been used since the 1960s. The technique includes attachment of reflective markers with double-adhesive tape to the skin of the patient. Marker positions are recorded when the patient walks through a calibrated measurement volume. Material and methods: In Study I, hip joint movements were measured with two different dynamic motion analysis systems, an optical tracking system and roentgen stereophotogrammetric analysis (RSA) in 16 patients with THA. In Study II, three patient groups were examined to study if the reproducibility of meas-ured values differs depending on whether the hip joint is normal, has developed OA or has been replaced with a THA. The aim of Study III was to investigate the gait in 22 patients operated bilaterally with two different types of stems at the same occasion. In Study IV, 62 patients operated with a Madreporic Lord hip prosthesis between 1979 and 1986 were followed for an average period of 26 years. In Study V, gait analy-sis was performed using two different motion analysis systems, one based on an optical tracking system and one based on accelerometers. Forty-nine THA patients were simultaneously evaluated with both methods. Results: During active hip motions soft-tissue displacements caused an underestimation of the true skeletal motion (Study I). In Study II the hip motions in patients with OA showed inferior repeatability between different investigators compared with THA patients and healthy controls. The gait pattern in the THA patients had not returned to normal one to two years after the operation. Study III showed no differences in speed, step length and frequency, or regarding kinematics or kinetics between short and conventional stems. Although both hip joints were operated during one-stage bilateral THA, there was still a difference between gait patterns two years after surgery compared with controls. In Study IV, the follow-up showed an average HHS of 81 (SD 14) and a pain score of 41 (SD 5), despite that more than half of the patients had undergone a revision of the acetabular cup. Some hips, but not all showed pronounced loss of bone mineral density around the stem. In Study V the accelerometer system measured movements of the pelvis and knee joint that did not differ from the optical system. However, significantly smaller flexion-extension was recorded. Conclusion: This dissertation shows that the deviation from skeletal movements measured using OTS is smallest when measuring hip flexion-extension in patients with THA. OTS is able to distinguish patients with hip osteoarthritis and patients with THA from a healthy control group while walking. The walking ability of patients with THA was still affected at least two years after surgery. A long-term follow-up of patients with an uncemented hip prosthesis revealed good function, despite that the acetabular component had been replaced in almost 50% of cases. The accelerometer-based motion analysis system that was exam-ined had good validity when measuring pelvis and knee movements in the sagittal plane, but underestimated hip joint flexion and extension

Different reliability of instrumented gait analysis between patients with unilateral hip osteoarthritis, unilateral hip prosthesis and healthy controls

Abstract Background The gait pattern varies within the population and between patient groups with different musculoskeletal diseases. It also varies over time due to various reasons. Three-dimensional gait analysis (3DGA) is frequently used to measure these changes, but the precision of this methodology may vary. Methods We primarily aimed to study the repeatability of hip motion measurements in patients with unilateral osteoarthritis (OA), patients with unilateral total hip arthroplasty (THA) and healthy controls. A secondary aim was to delineate any differences in hip motion during walking between these groups. Ten males and 10 females in each group were recruited. All patients underwent gait assessments using 3DGA recorded by 2 examiners. Data was analysed with comparison of variance and linear regression. Results The variability of the extension-flexion recordings was smallest in healthy controls (SD < 7.7°), increased in patients with THA (SD < 11.1°) and was most pronounced in the OA patients (SD < 12.2°). The degree of hip extension-flexion turned out to be the variable that most effectively could separate the controls from the 2 patient groups and the patient groups from each other. One to 2 years after THA the gait pattern was improved but still differed comparing a group of THA from a group of healthy controls. Conclusions Patients with hip osteoarthritis showed the poorest repeatability between gait recordings collected by different examiners, as compared to patients operated with a THA and healthy controls. The walking pattern after THA still differed from healthy controls 1–2 years after the operation

A wearable gait analysis system using inertial sensors Part I : Evaluation of measures of gait symmetry and normality against 3D kinematic data

Gait analysis (GA) is an important tool in the assessment of several physical and cognitive conditions. The lack of simple and economically viable quantitative GA systems has hindered the routine clinical use of GA in many areas. As a result, patients may be receiving sub-optimal treatment. The present study introduces and evaluates measures of gait symmetry and gait normality calculated from inertial sensor data. These indices support the creation of mobile, cheap and easy to use quantitative GA systems. The proposed method was compared to measures of symmetry and normality derived from 3D kinematic data. Results show that the proposed method is well correlated to the kinematic analysis in both symmetry (r=0.84, p&lt;0.0001) and normality (r=0.81, p&lt;0.0001). In addition, the proposed indices can be used to classify normal from abnormal gait.Partially funded by the PromobiliaFoundation and the Institute of Health and Care Sci-ences, Sahlgrenska Academy, University of Gothen-burg, Sweden.AccelGai

Vertical drop jump landing depth influences knee kinematics in female recreational athletes

ObjectivesTo examine whether different vertical drop jump (VDJ) landing depth (small versus deep) and stance width (wide versus narrow) may alter movement biomechanics in female recreational athletes. The purpose was also to identify whether leg muscle strength is a predictive factor for knee control during a VDJ.DesignCross-sectional.SettingBiomechanics laboratory. Participants: Eighteen women aged between 18 and 30 years.Main outcome measuresThree VDJ tests were used for biomechanical analysis: 1) small “bounce” jump (BJ), 2) deep “countermovement” jump with wide (CMJW) and 3) narrow foot position (CMJN). Subjects also performed an isometric knee-extension strength test, dichotomized to ‘weak’ versus ‘strong’ subjects according to median and quartiles.ResultsThere were greater knee valgus angles during landing for both the CMJW and CMJN test compared to the BJ test (p ≤ 0.05). Differences in knee valgus between weak and strong subjects were significant for the BJ test (p = 0.044) but not for any of the other tests.ConclusionsVDJ landing depth influences knee kinematics in women. Landing depth may therefore be considered when screening athletes using the VDJ test. Also, muscle strength seems to influence the amount of knee valgus angles, but the difference was not statistically significant (except for the BJ test) in this small cohort

Single-leg vertical jumping in young adults with spastic cerebral palsy

Background Maximum-strength tests are commonly used to detect muscle weakness in persons with cerebral palsy (CP). Tests of explosive strength (power) in the lower extremities, such as vertical jump tests, are more uncommon but might supplement maximum-strength testing by providing additional information about motor function.Research questionIs it feasible and useful to measure single-leg vertical jumping in young adults with CP? Methods Eleven persons with spastic CP (18–30 years), able to walk without support, were compared with a reference group. Jump height and power generation in jumping were measured using a 3D motion-analysis system and force plates. Maximum strength in plantarflexors was measured on the same occasion. Data were analysed using non-parametric statistics. Results Jump height was significantly greater in the reference group than in the group with CP, both relative to the less-involved leg of the participants with CP (p = .007) and relative to their more-involved leg (p &lt; .001). In the group with CP, jump height was twice as great for the less-involved leg than for the more-involved leg (p = .008). Power generation at the hip joint was similar between the groups but differed for the knee and ankle joints (p = .001–.033). In the reference group, most of the power was generated at the ankle joint, while the hip was the dominant power generator for the more-involved leg in the group with CP. Muscle strength in the group with CP showed a high correlation with jump height (rho = .745, p &lt; .001) and power generation at the ankle (rho = .780, p = .001). Significance The single-leg vertical jump test proved capable of measuring jump height and power generation in participants with CP. It also identified explosive muscle weakness both relative to a reference group and between legs. Hence the jump test may provide information additional to common tests of maximal muscle strength in persons with CP

Gluteus Maximus Transfer following Total Hip Arthroplasty Does Not Improve Abductor Moment: A Case-Control Gait Analysis Study of 15 Patients with Gluteus Medius Disruption

Gluteus maximus flap transfer (GMT) is a surgical technique used to improve gait kinematics and kinetics, as well as to reduce and ameliorate the functional outcome in patients with hip abductor deficiency following total hip arthroplasty (THA). The purpose of this observational study was to evaluate the gait pre- and postoperatively and examine whether GMT increases the abduction moment. Materials and Methods: A gait analysis based on reflective markers and force plates was performed in 15 patients who underwent GMT and were examined using an optical tracking system before and at a minimum of 13 months after the operation. The median follow-up time was 24 (13–60) months. The primary outcome was hip abduction moment (Nm/kg) during gait. The control group consisted of 15 female subjects without any gait pathology. Results: The mean adduction moment was significantly higher compared with controls before the operation (p = 0.02), but this did not apply to the abduction moment (p = 0.60). At the group level, the abduction moment did not improve postoperatively (p = 0.30). Only six of fifteen patients slightly improved their hip abduction moment postoperatively. However, speed (0.74 to 0.80 m/s) and cadence (94 to 105 steps/min) were improved (p < 0.03). Discussion: The results of this study showed no improvement in the hip abduction moment after GMT surgery. In our experience, abduction deficiency following primary THA is still a difficult and unsolved problem

Effect of stance width on kinematics of laboratory landings with fixed feet on a kiteboard

Funding: Swedish Research Council for Sport Science, and the Gothenburg Sports Test Centre</p