Andreas Kranzl

Torsional profile versus gait analysis: Consistency between the anatomic torsion and the resulting gait pattern in patients with rotational malalignment of the lower extremity.

Measurements of femoral and tibial torsion obtained from radiographs or computed tomographic scans have been used to describe rotational malalignment of the lower extremities and to clarify indications for surgery. A weak relationship between anatomic torsion deformity and the resulting transverse plane gait pattern in patients with cerebral palsy has been described, but the observations have not yet been tested in an able-bodied patient population. We conducted a prospective study to investigate the correlation of femoral torsion and tibial torsion as measured by using computed tomography with transverse plane gait data for patients with rotational malalignment. Twenty-six lower limbs from 26 patients selected for surgery based on gait analysis were evaluated. Calculation of Pearson correlations showed that increase of femoral anteversion resulted in increase of pelvic range of motion. A very weak correlation between femoral torsion and hip rotation (determination coefficient, R(2)=0.22) was found in a linear regression model, whereas tibial torsion and knee rotation showed a strong correlation (determination coefficient, R(2)=0.71). The correlation between the foot progression angle and tibial torsion was higher than between the foot progression angle and femoral torsion. We conclude that there is a considerable dynamic influence of mechanisms of compensation, especially in the hip, that should be considered when evaluating the torsional profile. We therefore recommend conducting three-dimensional instrumented gait analysis for patients undergoing surgical correction of rotational malalignment.

Results of Gait Analysis Including the Oxford Foot Model in Children with Clubfoot Treated with the Ponseti Method

BACKGROUND The aim of the study was to evaluate how clubfeet treated with the Ponseti method compare with control feet in gait analysis and whether additional information can be provided by the Oxford foot model. METHODS All patients with a minimum age of three years in our prospective database of clubfeet treated with the Ponseti method were considered for inclusion. Exclusion criteria were an associated syndrome or neurological disease, positional (slight) clubfoot, and presentation at an age of more than three months. Of the 125 patients with 199 clubfeet who satisfied the criteria, thirty-six (29%) agreed to participate in the study. Four of these were excluded because of insufficient gait analysis data, leaving thirty-two patients with fifty clubfeet for evaluation. Clinical examination and three-dimensional gait analysis including the Oxford foot model were performed, and a disease-specific questionnaire was administered. Kinetic and kinematic results were compared with those of an age-matched control group (n = 15). RESULTS The mean score on the disease-specific questionnaire was 83.5. Gait analysis showed significantly decreased range of motion, plantar flexion, and power of the ankle compared with controls. The mean external foot progression angle of 5.7° in the Ponseti group was slightly less than that in the controls. Slight intoeing occurred in 24%, and 12% did not achieve a neutral position during swing phase. Slight compensation was observed, including external rotation of the hip in 28%. The Oxford foot model revealed differences in foot motion between the groups. CONCLUSIONS Clubfoot treatment with the Ponseti method yielded good clinical results with high functional scores. Three-dimensional gait analysis demonstrated distinctive but slight deviations. Intoeing was less frequent and less severe compared with groups in the literature. We recommend the use of three-dimensional gait analysis, including a foot model, as an objective tool for evaluation of the results of clubfoot treatment. LEVEL OF EVIDENCE Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Functional and radiographic consideration of lower limb malalignment in children and adolescents with idiopathic genu valgum

Three‐dimensional gait analysis is capable of assessing dynamic load characteristics and the resulting compensatory effects of lower limb malalignment, which are generally not reflected in static imaging. This study determined differences in gait parameters in the frontal and transverse plane between patients and controls in order to identify compensatory mechanisms, and to correlate radiographic measurements and gait parameters in a consecutive series of children with idiopathic genu valgum. Thirty‐three patients (mean age 12.3 years) were retrospectively reviewed and compared to a healthy control group. Children with genu valgum demonstrated significantly decreased internal knee valgus moments, shifting into varus moments. Furthermore, significantly different transverse plane gait patterns (decreased external knee rotation, increased external hip rotation) were observed. These patterns showed a relevant influence on the frontal knee moments, with knee rotation and foot progression angle showing the highest predictive value for changes and possible compensation of frontal knee moments. The correlation between commonly used radiographic measurements (i.e., mechanical axis deviation) and findings of the gait analysis was only low. Besides showing decreased internal knee valgus moments, our results suggest that considerable compensatory gait mechanisms may be present in children with idiopathic genu valgum to reduce joint loading.

Within-assessor reliability and minimal detectable change of gait kinematics in a young obese demographic

INTRODUCTION Three-dimensional gait analysis (3DGA) in obese populations is a difficult task due to a great amount of subcutaneous fat. This makes it more challenging to identify anatomical landmarks, thus leading to inconsistent marker placement. Therefore, the purpose of this study was to investigate the test-retest reliability for kinematic measurements of obese children and adolescents. METHODS Nine males and two females with an age-based BMI above the 97th percentile (age: 14.6±2.6years, BMI: 33.4±4.4kg/m2) were administered to two 3DGA sessions. To quantify reliability of discrete parameters the intraclass correlation coefficient (ICC2,k), standard error of measurement (SEM) and minimal detectable change (MDC) were calculated. To quantify waveform similarity, the coefficient of multiple correlation (CMC) and the linear fit method (LFM) were used. RESULTS From 28 kinematic parameters, 23 showed acceptable ICCs (≥0.70) and the remaining parameters demonstrated moderate values. These were peak hip extension during stance (0.58), mean pelvis rotation (0.60), mean anterior pelvic tilt (0.64), peak knee flexion during swing (0.67) and peak hip abduction during swing (0.69). The SEM was below 5° for all parameters. The MDC for the sagittal, frontal, and transversal plane were on average 7.5°±2.2, 4.6°±1.3 and 6.0°±0.9 respectively. Both the LFM and CMC showed, in general, moderate to good reliability except for pelvis tilt and hip rotation. CONCLUSION Data demonstrated acceptable error margins especially for the sagittal and frontal plane. Low reliability for the pelvis tilt indicates that great effort is necessary to position the pelvic markers consistently during repeated sessions.

Is the reliability of 3D kinematics of young obese participants dependent on the hip joint center localization method used

The aim of this study was to investigate if the test-retest reliability for three-dimensional (3D) gait kinematics in a young obese population is affected by using either a predictive (Davis) or a functional (SCoRE) hip joint center (HJC) localization approach. A secondary goal was to analyze how consistent both methods perform in estimating the HJC position. A convenience sample of ten participants, two females and eight males with an age-based body mass index (BMI) above the 97th percentile (mean±SD: 34.2±3.9kg/m2) was recruited. Participants underwent two 3D gait analysis sessions separated by a minimum of one day and a maximum of seven days. The standard error of measurement (SEM) and the root mean square error (RMSE) of key kinematic parameters along with the root mean square deviation (RMSD) of the entire waveforms were used to analyze the test-retest reliability. To get an estimate of the consistency of both HJC localization methods, the HJC positions determined by both methods were compared to each other. SEM, RMSE, and RMSD results indicate that the HJC position estimations between both methods are not different and demonstrate moderate to good reliability to estimate joint kinematics. With respect to the localization of the HJC, notable inconsistencies ranging from 0 to 5.4cm were observed. In conclusion, both approaches appear equally reliable. However, the inconsistent HJC estimation points out, that accuracy seems to be a big issue in these methods. Future research should attend to this matter.

Reliability of joint kinematic calculations based on direct kinematic and inverse kinematic models in obese children

BACKGROUND In recent years, the reliability of inverse (IK) and direct kinematic (DK) models in gait analysis have been assessed intensively, but mainly for lean populations. However, obesity is a growing issue. So far, the sparse results available for the reliability of clinical gait analysis in obese populations are limited to direct kinematic models. Reliability error-margins for inverse kinematic models in obese populations have not been reported yet. RESEARCH QUESTIONS Is there a difference in the reliability of IK models compared with a DK model in obese children? Are there any differences in the joint kinematic output between IK and DK models? METHODS A test-retest study was conducted using three-dimensional gait analysis data from two obese female and eight obese male participants from an earlier study. Data were analyzed using a DK model and two OpenSim-based IK models. Test-retest reliability was compared by calculating the Standard Error of Measurement (SEM) along with similar absolute reliability measures. A Friedman Test was used to assess whether there were any significant differences in the reliability between the models. Kinematic output of the models was compared by using Statistical Parametric Mapping (SPM). RESULTS No significant differences were found in the reliability between the DK and IK models. The SPM analysis indicated several significant differences between both IK models and the DK approach. Most of these differences were continuous offsets. SIGNIFICANCE Reliability values showed clinically acceptable error-margins and were comparable between all models. Therefore, our results support the careful use of IK models in overweight or obese populations, e.g. for musculoskeletal modelling studies. The inconsistent kinematic output can mainly be explained by different model conventions and anatomical segment coordinate frame definitions.

Rotational gait patterns in children and adolescents following tension band plating of idiopathic genua valga

Literature suggests that children and adolescents with idiopathic genua valga present with considerable gait deviations in frontal and transverse planes, including altered frontal knee moments, reduced external knee rotation, and increased external hip rotation. This study aimed to evaluate gait parameters in these patients after surgical correction using tension band plating (TBP). We prospectively evaluated 24 consecutive, skeletally immature patients, who received full‐length standing radiographs and three‐dimensional gait analysis before and after correction, and compared the results observed to a group of 11 typically developing peers. Prior to TBP the cohort showed significantly decreased (worse) internal frontal knee moments compared to the control group. After axis correction the mean and maximum knee moments changed significantly into normalized knee moments (p < 0.0001). In the transverse plane, only the foot progression angle (p = 0.020) changed significantly following intervention. Post‐correction knee moments were similar to controls (p = 0.175), but the patient cohort exhibited a significantly decreased knee external rotation (p = 0.004) and increased external hip rotation (p < 0.001) during gait. In addition, the effect of transverse plane changes on knee moments in patients with restored, straight limb axis was calculated. Hence, patients with restored alignment but persistence of decreased external knee rotation demonstrated significantly greater knee moments than those without rotational abnormalities (p = 0.001). This study found that frontal knee moments during gait normalized in children with idiopathic genua valga after surgery. However, decreased external knee rotation and increased external hip rotation during gait persisted in the study cohort. Despite radiological correction, decreased external rotation during gait was associated with increases in medial knee loading. Surgical correction for children with genua valga but normal knee moments may be detrimental, due to redistribution of dynamic knee loading into the opposite joint compartment.