DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY
ORIGINAL ARTICLE
Construct validity and reliability of the Selective Control Assessment of the Lower Extremity in children with cerebral palsy JULIA BALZER 1 | PETRA MARSICO 1 | ELENA MITTEREGGER 2 THOMAS H MERCER 3 | HUBERTUS J A VAN HEDEL 1
| MARIETTA L VAN DER LINDEN 3 |
1 Pediatric Rehab Research Group, Rehabilitation Center for Children and Adolescents, University Children’s Hospital Zurich, Affoltern am Albis; 2 Regional Group Zurich Foundation Cerebral Palsy (RGZ), Zurich, Switzerland. 3 Rehabilitation Sciences, School of Health Sciences, Queen Margaret University, Edinburgh, UK. Correspondence to Julia Balzer, Pediatric Rehab Research Group, Rehabilitation Center for Children and Adolescents, University Children’s Hospital Zurich, M€uhlebergstrasse 104, CH-8910 Affoltern am Albis, Switzerland. E-mail: [email protected] This article is commented on by Fowler on page 116 of this issue.
PUBLICATION DATA
Accepted for publication 14th April 2015. Published online 20th May 2015. ABBREVIATIONS
FMA ICC IQR MAS MDC MMT SCALE SVMC
Fugl-Meyer Assessment Intraclass correlation coefficient Interquartile range Modified Ashworth Scale Minimal detectable change Manual Muscle Test Selective Control Assessment of the Lower Extremity Selective voluntary motor control
AIM Assessing impaired selective voluntary movement control in children with cerebral palsy (CP) has gained increasing interest. We investigated construct validity and intra- and interrater reliability of the Selective Control Assessment of the Lower Extremity (SCALE). METHOD Thirty-nine children (21 males, 18 females) with spastic CP, mean age 12 years 6 months [range 6y 11mo–19y 9mo], Gross Motor Function Classification System (GMFCS) levels I to IV, participated. Differences in SCALE scores were determined on joint levels and between patients categorized according to their limb distribution and GMFCS levels. SCALE scores were correlated with the Fugl-Meyer Assessment, Manual Muscle Test, and Modified Ashworth Scale. To determine reliability, the SCALE was applied once and recorded on video. RESULTS SCALE scores differed significantly between the less and more affected leg (p0.70) between the SCALE and the FuglMeyer Assessment (FMA) was expected. We further hypothesized that children with spastic CP and a high degree of muscle weakness and/or spasticity would score low via the SCALE assessment. Finally, we hypothesized that reliability would be excellent, with ICC values exceeding 0.8 (see also Fowler et al.10) and accompanied by acceptable levels of absolute measurement error.
METHOD Participants In- and outpatients of the Rehabilitation Centre Affoltern am Albis, University Children’s Hospital Zurich were recruited by convenience sampling. A minimum sample size of 25 to 30 participants was required, in order to provide an accurate estimate of the random error.16 Inclusion criteria were: diagnosis of CP, aged between 5 and 20 years, ability to walk (GMFCS levels I–IV), and ability to 168 Developmental Medicine & Child Neurology 2016, 58: 167–172
• • •
What this paper adds The Selective Control Assessment of the Lower Extremity (SCALE) German version is a valid and reliable assessment for children with spastic CP. Total SCALE scores differed significantly between Gross Motor Function Classification System levels I versus II. Minimal detectable change of the SCALE is 2 points.
follow simple instructions. Participants with an unstable situation regarding their tonus-regulating medications and/ or who had a botulinum toxin injection within the last 6 months, or any surgical correction within the last year, were excluded. The study was approved by the ethical committee of the Canton of Zurich (KEK-ZH-Nr.20110404). Informed consent and assent were obtained from parents and participants.
Measurements In order to promote assessment of the SCALE in the German-speaking clinical environment, the SCALE was translated into German according to international guidelines:17 (1) translation into German by two independent native German-speaking physiotherapists; (2) creation of a consensus version; (3) back-translation into English by a translation company; and (4) endorsement by the authors of the original version (see Appendix S1, online supporting information, for the final German SCALE version). Testing procedures were standardized according to the assessment guidelines. All tests were carried out by the same two experienced neuropaediatric physiotherapists, one assessing and one assisting. Tests were performed for both legs within a maximum time-frame of 1 hour. SCALE administration required patients to perform specific isolated movement patterns at the hip, knee, ankle, subtalar, and toe joint. SVMC of each joint movement was scored on a 3-point ordinal scale. SVMC was scored as ‘normal’ (2 points) if the patient could move the tested joint isolated (e.g. without moving other joints), within at least 50% of the possible range of motion, and at a physiological cadence cued verbally by the therapist (e.g. ‘flex, extend, flex’). If any deviation in performance occurred (movement performed slower, below 50% of range of movement, with co-/mirror-/synergistic-movements), selectivity was regarded as impaired (1 point). The score unable was given, if no joint movement could be made or masssynergy-patterns occurred. SVMC was scored separately for each joint, for each limb, and for both limbs together. To analyze discriminant validity, patients were classified according to their limb involvement and GMFCS18 level (I–IV). The Manual Muscle Test (MMT) leg-score was used to determine the more and less affected leg. If MMT scores were similar, further differentiation was based on Modified Ashworth Scale (MAS) scores. To assess the SCALE‘s concurrent validity, the FMA19 was measured. The FMA is a valid assessment tool for testing SVMC in stroke and contains specific items for testing selectivity of the knee (FMA items IIIa; IVa) and ankle joint (FMA items IIIb; IVb). Like the SCALE, the FMA
uses a 3-point ordinal scale to score (0=cannot perform; 1=performs partly; 2=performs fully) selectivity of the joint movement. Furthermore, when correctly applied, the MMT should also reflect the selective activation of a muscle (group). We therefore assessed strength of the hip and knee flexors and extensors, and of ankle dorsi- and plantar-flexors by the MMT (0–5; Kendall et al.20). Despite spasticity and SVMC being different constructs, spasticity can negatively influence SVMC and therefore we were interested in correlating the SCALE with MAS scores (0–4; Bohannon and Smith21). We assessed the MAS also for hip, knee, and ankle joints. The SCALE assessment was videotaped for (intra- and interrater) reliability testing, in order to minimize participants’ strain. The camera was positioned in front of the participant. This position allowed observation of the tested joint movement and of possible compensatory and mirror movements of the contralateral limb, as well as of other body parts. Although an additional video from the sagittal plane may have allowed for a more accurate evaluation of the range of motion of the ankle and knee joint, none of the raters experienced difficulties in evaluating whether the movement exceeded 50% of the passive range of motion (one criterion that differentiates between normal or impaired SVMC) or not. For reliability testing the videotaped assessment was scored twice within a timeframe of 6 to 8 weeks after the first scoring. Rater(s) was (were) blinded to the results of the first scoring (intrarater) or results from the other rater (interrater).
Statistical analysis The Shapiro–Wilk test showed that most scores were not normally distributed, hence non-parametric statistical tests were used. Therefore, a Friedman test was performed to determine whether SCALE scores differed between joint pairs of each leg. Alpha was set at 0.05 (two-tailed). Post hoc differences between adjacent joints (i.e. hip vs knee), as well as between sum scores of the more and less involved leg, were determined with the Wilcoxon signed rank test (to adjust for multiple comparisons, alpha was set at 0.01). Differences in total SCALE scores for children categorized via GMFCS level were evaluated with the Kruskal–Wallis test. We defined a priori that we performed post hoc successive pair-wise testing between adjacent GMFCS levels (e.g. level I vs II, level II vs III) with Mann–Whitney U tests (post hoc tests: alpha=0.025). To further evaluate the validity of the SCALE Spearman’s rank correlation coefficients (q) between SCALE scores on joint, limb, and total levels and FMA, MMT, and MAS scores were calculated. Relative intra- and interrater reliability was evaluated by ICCs (two-way mixed model; type absolute agreement) and corresponding 95% confidence intervals were calculated for the less and more involved leg. Absolute reliability was determined by the standard error of measurement (SEM=SD9√(1-r)) and the minimal detectable change (MDC=SEM9√291.96).
Statistical analysis was performed with Armonk, NY, USA).
SPSS
17.0 (IBM,
RESULTS Forty-two children with spastic CP gave informed consent to participate in this study. One child did not complete the assessments because of a lack of compliance. As allocation of the more and less affected leg was not possible in two data sets, these data sets were omitted from all analyses. Therefore, demographic and clinical characteristics of 39 children with spastic CP (unilateral n=20; bilateral n=19) were available. The mean age was 12y 6mo (SD 3y 7mo). Eighteen children were female. Twenty-three children had a GMFCS level I, five had level II, eight level III and three level IV. Further characteristics are presented in Table I. Discriminant validity SCALE scores of contralateral joint pairs (i.e. knee vs knee) of the less affected leg were significantly higher compared to those of the more affected leg, with the exception of the hip joint, p=0.157 (Fig. 1a). SCALE scores were generally lower for distal compared to proximal joints for both legs, with the exception of the ankle versus toes for the less affected leg, and bilaterally for the subtalar joint on toes (Fig. 1a). SCALE limb scores were higher for the less affected limb (median=7; interquartile range [IQR]=0– 10) compared to the more affected limb (median=5; IQR=0–9; p
ORIGINAL ARTICLE
Construct validity and reliability of the Selective Control Assessment of the Lower Extremity in children with cerebral palsy JULIA BALZER 1 | PETRA MARSICO 1 | ELENA MITTEREGGER 2 THOMAS H MERCER 3 | HUBERTUS J A VAN HEDEL 1
| MARIETTA L VAN DER LINDEN 3 |
1 Pediatric Rehab Research Group, Rehabilitation Center for Children and Adolescents, University Children’s Hospital Zurich, Affoltern am Albis; 2 Regional Group Zurich Foundation Cerebral Palsy (RGZ), Zurich, Switzerland. 3 Rehabilitation Sciences, School of Health Sciences, Queen Margaret University, Edinburgh, UK. Correspondence to Julia Balzer, Pediatric Rehab Research Group, Rehabilitation Center for Children and Adolescents, University Children’s Hospital Zurich, M€uhlebergstrasse 104, CH-8910 Affoltern am Albis, Switzerland. E-mail: [email protected] This article is commented on by Fowler on page 116 of this issue.
PUBLICATION DATA
Accepted for publication 14th April 2015. Published online 20th May 2015. ABBREVIATIONS
FMA ICC IQR MAS MDC MMT SCALE SVMC
Fugl-Meyer Assessment Intraclass correlation coefficient Interquartile range Modified Ashworth Scale Minimal detectable change Manual Muscle Test Selective Control Assessment of the Lower Extremity Selective voluntary motor control
AIM Assessing impaired selective voluntary movement control in children with cerebral palsy (CP) has gained increasing interest. We investigated construct validity and intra- and interrater reliability of the Selective Control Assessment of the Lower Extremity (SCALE). METHOD Thirty-nine children (21 males, 18 females) with spastic CP, mean age 12 years 6 months [range 6y 11mo–19y 9mo], Gross Motor Function Classification System (GMFCS) levels I to IV, participated. Differences in SCALE scores were determined on joint levels and between patients categorized according to their limb distribution and GMFCS levels. SCALE scores were correlated with the Fugl-Meyer Assessment, Manual Muscle Test, and Modified Ashworth Scale. To determine reliability, the SCALE was applied once and recorded on video. RESULTS SCALE scores differed significantly between the less and more affected leg (p0.70) between the SCALE and the FuglMeyer Assessment (FMA) was expected. We further hypothesized that children with spastic CP and a high degree of muscle weakness and/or spasticity would score low via the SCALE assessment. Finally, we hypothesized that reliability would be excellent, with ICC values exceeding 0.8 (see also Fowler et al.10) and accompanied by acceptable levels of absolute measurement error.
METHOD Participants In- and outpatients of the Rehabilitation Centre Affoltern am Albis, University Children’s Hospital Zurich were recruited by convenience sampling. A minimum sample size of 25 to 30 participants was required, in order to provide an accurate estimate of the random error.16 Inclusion criteria were: diagnosis of CP, aged between 5 and 20 years, ability to walk (GMFCS levels I–IV), and ability to 168 Developmental Medicine & Child Neurology 2016, 58: 167–172
• • •
What this paper adds The Selective Control Assessment of the Lower Extremity (SCALE) German version is a valid and reliable assessment for children with spastic CP. Total SCALE scores differed significantly between Gross Motor Function Classification System levels I versus II. Minimal detectable change of the SCALE is 2 points.
follow simple instructions. Participants with an unstable situation regarding their tonus-regulating medications and/ or who had a botulinum toxin injection within the last 6 months, or any surgical correction within the last year, were excluded. The study was approved by the ethical committee of the Canton of Zurich (KEK-ZH-Nr.20110404). Informed consent and assent were obtained from parents and participants.
Measurements In order to promote assessment of the SCALE in the German-speaking clinical environment, the SCALE was translated into German according to international guidelines:17 (1) translation into German by two independent native German-speaking physiotherapists; (2) creation of a consensus version; (3) back-translation into English by a translation company; and (4) endorsement by the authors of the original version (see Appendix S1, online supporting information, for the final German SCALE version). Testing procedures were standardized according to the assessment guidelines. All tests were carried out by the same two experienced neuropaediatric physiotherapists, one assessing and one assisting. Tests were performed for both legs within a maximum time-frame of 1 hour. SCALE administration required patients to perform specific isolated movement patterns at the hip, knee, ankle, subtalar, and toe joint. SVMC of each joint movement was scored on a 3-point ordinal scale. SVMC was scored as ‘normal’ (2 points) if the patient could move the tested joint isolated (e.g. without moving other joints), within at least 50% of the possible range of motion, and at a physiological cadence cued verbally by the therapist (e.g. ‘flex, extend, flex’). If any deviation in performance occurred (movement performed slower, below 50% of range of movement, with co-/mirror-/synergistic-movements), selectivity was regarded as impaired (1 point). The score unable was given, if no joint movement could be made or masssynergy-patterns occurred. SVMC was scored separately for each joint, for each limb, and for both limbs together. To analyze discriminant validity, patients were classified according to their limb involvement and GMFCS18 level (I–IV). The Manual Muscle Test (MMT) leg-score was used to determine the more and less affected leg. If MMT scores were similar, further differentiation was based on Modified Ashworth Scale (MAS) scores. To assess the SCALE‘s concurrent validity, the FMA19 was measured. The FMA is a valid assessment tool for testing SVMC in stroke and contains specific items for testing selectivity of the knee (FMA items IIIa; IVa) and ankle joint (FMA items IIIb; IVb). Like the SCALE, the FMA
uses a 3-point ordinal scale to score (0=cannot perform; 1=performs partly; 2=performs fully) selectivity of the joint movement. Furthermore, when correctly applied, the MMT should also reflect the selective activation of a muscle (group). We therefore assessed strength of the hip and knee flexors and extensors, and of ankle dorsi- and plantar-flexors by the MMT (0–5; Kendall et al.20). Despite spasticity and SVMC being different constructs, spasticity can negatively influence SVMC and therefore we were interested in correlating the SCALE with MAS scores (0–4; Bohannon and Smith21). We assessed the MAS also for hip, knee, and ankle joints. The SCALE assessment was videotaped for (intra- and interrater) reliability testing, in order to minimize participants’ strain. The camera was positioned in front of the participant. This position allowed observation of the tested joint movement and of possible compensatory and mirror movements of the contralateral limb, as well as of other body parts. Although an additional video from the sagittal plane may have allowed for a more accurate evaluation of the range of motion of the ankle and knee joint, none of the raters experienced difficulties in evaluating whether the movement exceeded 50% of the passive range of motion (one criterion that differentiates between normal or impaired SVMC) or not. For reliability testing the videotaped assessment was scored twice within a timeframe of 6 to 8 weeks after the first scoring. Rater(s) was (were) blinded to the results of the first scoring (intrarater) or results from the other rater (interrater).
Statistical analysis The Shapiro–Wilk test showed that most scores were not normally distributed, hence non-parametric statistical tests were used. Therefore, a Friedman test was performed to determine whether SCALE scores differed between joint pairs of each leg. Alpha was set at 0.05 (two-tailed). Post hoc differences between adjacent joints (i.e. hip vs knee), as well as between sum scores of the more and less involved leg, were determined with the Wilcoxon signed rank test (to adjust for multiple comparisons, alpha was set at 0.01). Differences in total SCALE scores for children categorized via GMFCS level were evaluated with the Kruskal–Wallis test. We defined a priori that we performed post hoc successive pair-wise testing between adjacent GMFCS levels (e.g. level I vs II, level II vs III) with Mann–Whitney U tests (post hoc tests: alpha=0.025). To further evaluate the validity of the SCALE Spearman’s rank correlation coefficients (q) between SCALE scores on joint, limb, and total levels and FMA, MMT, and MAS scores were calculated. Relative intra- and interrater reliability was evaluated by ICCs (two-way mixed model; type absolute agreement) and corresponding 95% confidence intervals were calculated for the less and more involved leg. Absolute reliability was determined by the standard error of measurement (SEM=SD9√(1-r)) and the minimal detectable change (MDC=SEM9√291.96).
Statistical analysis was performed with Armonk, NY, USA).
SPSS
17.0 (IBM,
RESULTS Forty-two children with spastic CP gave informed consent to participate in this study. One child did not complete the assessments because of a lack of compliance. As allocation of the more and less affected leg was not possible in two data sets, these data sets were omitted from all analyses. Therefore, demographic and clinical characteristics of 39 children with spastic CP (unilateral n=20; bilateral n=19) were available. The mean age was 12y 6mo (SD 3y 7mo). Eighteen children were female. Twenty-three children had a GMFCS level I, five had level II, eight level III and three level IV. Further characteristics are presented in Table I. Discriminant validity SCALE scores of contralateral joint pairs (i.e. knee vs knee) of the less affected leg were significantly higher compared to those of the more affected leg, with the exception of the hip joint, p=0.157 (Fig. 1a). SCALE scores were generally lower for distal compared to proximal joints for both legs, with the exception of the ankle versus toes for the less affected leg, and bilaterally for the subtalar joint on toes (Fig. 1a). SCALE limb scores were higher for the less affected limb (median=7; interquartile range [IQR]=0– 10) compared to the more affected limb (median=5; IQR=0–9; p
