Intraobserver Reliability and Construct Validity of the Squat Test in Children With Cerebral Palsy.

PURPOSE: This study evaluated intraobserver reliability and construct validity of the squat test to assess lower extremity strength in children with cerebral palsy (CP) and spastic diplegia. METHODS: Children with CP performed 2 trials of the squat test and calculated the intraclass correlation coefficient to evaluate intraobserver reliability. Correlations between outcomes of hand-held dynamometry (HHD) of knee extensor strength and an 8-repetition maximum (8RM) leg press test and the squat test were calculated to evaluate construct validity. RESULTS: Excellent intraobserver reliability was observed for the squat test. Correlations between squat test performance and HHD knee extension and 8RM leg press test demonstrated good construct validity. CONCLUSIONS: The squat test is a reliable and valid tool to assess lower extremity strength in children with CP and spastic diplegia. The squat test is inexpensive and less time-consuming, and therefore particularly suitable for clinicians.

Mobility of the rotating platform in low contact stress knee arthroplasty is durable.

PURPOSE: The mobile bearing or rotating platform (RP) in total knee arthroplasty (TKA) is originally part of a low contact stress (LCS) concept, with bearing undersurface mobility compensating higher bearing upper-surface congruency. The in vivo range of axial femorotibial rotation in RP knees has been the subject of many studies, but always involving the performance of relatively low demanding task conditions. Hardly any study has addressed the maintenance of this rotation over time. METHODS: Two consecutive series of patients with LCS RP knees were studied in a cross-sectional study of 1- and 5-year follow-up. They were assessed using optoelectronic movement analysis during gait and the performance of a sit-to-walk (STW) task with and without turning steps. RESULTS: A mean range of rotation (SD) was found in the 1-year group of 13.4° (3.7) during gait, 17.8° (6.8) during STW straight, and 17.9° (6.9) during STW with turning. The range in the 5-year group was 11.2° (6.0) during gait, 18.5° (8.7) during STW straight, and 18.3° (8.3) during STW with turning. A so-called paradoxical axial rotation pattern during gait and STW straight occurred in both groups in a normal prevalence. CONCLUSION: The amount and pattern of rotation in a LCS RP knee does not become impaired between 1 and 5 years postoperatively. The theoretical benefit of RP TKA has not been proven in any clinical study so far, and studies with suitable long-term follow-up need to prove whether this mobility also leads to improved prosthesis survival. However, our findings support the functioning of the rotating platform at a basal science level and illustrate the need for the use of more complex tasks in kinematic studies. LEVEL OF EVIDENCE: Therapeutic study, Level III.

Development of a core set of gait features and their potential underlying impairments to assist gait data interpretation in children with cerebral palsy.

Background: The interpretation of clinical gait data in children with cerebral palsy (CP) is time-consuming, requires extensive expertise and often lacks transparency. Here we aimed to develop a set of look-up tables to support this process, linking typical gait features as present in CP to their potential underlying impairments. Methods: We developed an initial core set of gait features and their potential underlying impairments based on biomechanical reasoning, literature and clinical experience. This core set was further specified through a Delphi process in a multidisciplinary group of experts in gait analysis of children with CP and evaluated on 20 patient cases. The likelihood of the listed gait feature-impairment relationships was scored by the expert panel on a five-point scale. Results: The final core set included 120 relevant gait feature-impairment relations including likelihood scores. This set was presented in the form of look-up tables in both directions, i.e., sorted by gait features with potential underlying impairment, and sorted by impairments with potential related gait features. The average likelihood score for the relations was 3.5 ± 0.6 (range 2.1-4.6). Conclusion: The developed set of look-up tables linking gait features and impairments, can assist gait analysts and clinicians in standardized biomechanical reasoning, to support treatment decision-making for gait impairments in children with CP.

Recording scapular motion using an acromion marker cluster.

Disorders of the shoulder complex can be accompanied by changes in the movement pattern of the scapula. However, scapular motion is difficult to measure. A possible non-invasive method for dynamic three-dimensional kinematic measurement of the human scapula is the use of a marker cluster placed on the flat part of the acromion. A small light-weight acromion marker cluster (AMC) is presented in this study. In order to assess validity, kinematics obtained with the AMC were compared to simultaneous scapula locator (SL) recordings in a series of postures. The test/retest variability of replacement of the AMC, was also assessed. Measurement errors appeared to be sensitive for the plane of movement, the degree of humerus elevation, and replacement of the AMC. The AMC generally under-estimated scapula motion, compared to the SL. Some significant differences were found between the two methods, although the absolute differences were small (maximum mean difference 8.4 degrees in extreme position). In humerus forward flexion and abduction the maximum mean differences were 6 degrees or lower. In conclusion, the AMC is a valid method of measuring scapular movement during arm elevation that could be used in shoulder pathologies. Placement and planes of movement should be carefully considered and elevation of the humerus should not exceed 100 degrees.

Outcome of medial hamstring lengthening in children with spastic paresis: A biomechanical and morphological observational study.

To improve gait in children with spastic paresis due to cerebral palsy or hereditary spastic paresis, the semitendinosus muscle is frequently lengthened amongst other medial hamstring muscles by orthopaedic surgery. Side effects on gait due to weakening of the hamstring muscles and overcorrections have been reported. How these side effects relate to semitendinosus morphology is unknown. This study assessed the effects of bilateral medial hamstring lengthening as part of single-event multilevel surgery (SEMLS) on (1) knee joint mechanics (2) semitendinosus muscle morphology and (3) gait kinematics. All variables were assessed for the right side only. Six children with spastic paresis selected for surgery to counteract limited knee range of motion were measured before and about a year after surgery. After surgery, in most subjects popliteal angle decreased and knee moment-angle curves were shifted towards a more extended knee joint, semitendinosus muscle belly length was approximately 30% decreased, while at all assessed knee angles tendon length was increased by about 80%. In the majority of children muscle volume of the semitendinosus muscle decreased substantially suggesting a reduction of physiological cross-sectional area. Gait kinematics showed more knee extension during stance (mean change ± standard deviation: 34±13°), but also increased pelvic anterior tilt (mean change ± standard deviation: 23±5°). In most subjects, surgical lengthening of semitendinosus tendon contributed to more extended knee joint angle during static measurements as well as during gait, whereas extensibility of semitendinosus muscle belly was decreased. Post-surgical treatment to maintain muscle belly length and physiological cross-sectional area may improve treatment outcome of medial hamstring lengthening.

Acclimatization of the gait pattern to wearing an ankle-foot orthosis in children with spastic cerebral palsy.

BACKGROUND: Ankle-foot orthoses can be prescribed to improve gait in children with cerebral palsy. Before evaluating the effects of ankle-foot orthoses on gait, a period to adapt or acclimatize is usually applied. It is however unknown whether an acclimatization period is actually needed to reliably evaluate the effect of a new orthosis on gait. This study aimed to investigate whether specific gait parameters in children with cerebral palsy would change within an acclimatization period after being provided with new ankle-foot orthoses. METHODS: Ten children with cerebral palsy, walking with excessive knee flexion in midstance (8 boys; mean (SD) 10.2 (1.9) years; Gross Motor Function Classification System levels I-II) were provided with ventral shell ankle-foot orthoses. The orthoses were worn in combination with the child's own shoes and tuned, based on ground reaction force alignment with respect to the lower limb joints. Directly after tuning (T0) and four weeks later (T1), 3D-gait analysis was performed using an optoelectronic motion capture system and a force plate. From this assessment, ten spatiotemporal, kinematic and kinetic gait parameters were derived for the most affected leg. Differences in parameters between T0 and T1 were analyzed using paired t-tests or Wilcoxon signed rank tests (P<0.05). FINDINGS: Over the course of four weeks, no significant differences (P ≥ 0.080) were observed for any investigated parameter. INTERPRETATION: These results imply that the biomechanical effect of ventral shell ankle-foot orthoses on gait in independent walking children with cerebral palsy is immediately apparent, i.e., there is no further change after acclimatization.

Mobile-bearing total knee arthroplasty: More rotation is evident during more demanding tasks.

BACKGROUND: Some reports showed few but significant more axial femorotibial rotation in favor of mobile-bearing (MB) versus fixed-bearing (FB) total knee arthroplasty (TKA), mostly during knee bend fluoroscopic studies. The goal of the current study was to submit MB and FB groups of TKA patients to a turning activity, in which additional rotation was to be expected. METHODS: Two consecutive cohorts of patients after TKA (10 FB and 11 MB knees in a total of 18 patients) were assessed using motion analysis five year postoperatively, while performing gait and sit-to-walk (STW) movements with and without turning steps. RESULTS: Mean range of rotation in the FB group increased from 9.7° during gait, to 11.7° during STW straight, and to 14.3° during STW turning. Mean range of rotation in the MB group increased from 13.4° during gait to 21.0° during STW straight, and stayed at 21.1° during STW turning. CONCLUSIONS: Too many uncontrolled variables in the current study hinder a meaningful discrimination of MB from FB TKA rotation. However, the study does illustrate how more demanding task loads could be helpful in exploring the geometric constraints of TKA variants. LEVEL OF EVIDENCE: Level III, therapeutic study.