Quantifying the separate effects of Botulinum toxin-A and lower leg casting on ankle joint hyper-resistance in children with cerebral palsy

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Do Botulinum toxin-A and lower leg casting alter calf muscle and tendon lengths in children with spastic cerebral palsy?

Introduction: Ankle joint hyper-resistance in children with spastic cerebral palsy (SCP) is commonly treated with Botulinum Toxin-A (BoNT-A) injections in the medial gastrocnemius (MG) combined with lower-leg casting. The overall aim of this combined treatment is to reduce spasticity and increase range of motion (1). Since hyper-resistance assessment mainly focuses on the joint level, whereas the treatment is directed at the muscle, it is worthwhile investigating the individual effects of BoNT-A and casting on MG and tendon lengths, to provide insight into the working mechanisms and to help improving treatment efficacy. Research question: What are the effects of BoNT-A injections and lower-leg casting on the MG and tendon lengths, at resting position and maximum dorsiflexion, in children with SCP? Methods: Children with SCP were assigned by minimization to receive either two weeks of lower-leg casts (n = 12, mean age 8.27 years; GMFCS-level I-III) or MG BoNT-A injections (n = 11, mean age: 6.75 years; GMFCS-level I-III). Data was acquired by 3D-freehand-ultrasound (2) at baseline and two weeks post-intervention with the knee in flexion (30.9° ± 3.7°) and the ankle in resting position and maximum dorsiflexion (maxDF). The same assessor extracted muscle and tendon lengths from the 3D reconstructions twice, and the standard error of measurement (SEM) was quantified. Muscle tendon unit (MTU) length was calculated as the summation of muscle (ML) and tendon length (TL). The change in ML and TL between rest and maxDF was used to calculate extensibility. Within-group treatment effect was evaluated with Wilcoxon signed rank tests and treatment differences, with Mann-Whitney U tests. Post-treatment changes were considered significant when >SEM and p < 0.05. Results: At baseline, groups did not differ for age, joint angles and lengths. Post-casting, resting angle, maxDF, MTU and TL at maxDF significantly increased. While two weeks post-BoNT-A-injection only MTU length and ML at rest significantly increased. There was no treatment effect on the extensibility. The change in maxDF, and ML at rest were significantly larger post-casting compared to post-BoNT-A. Similarly, the post-treatment change in MTU length at maxDF was significantly larger after casting compared to BoNT-A. Discussion: The results suggest that two weeks casting resulted in increased maxDF and MTU-length by increased TL (or compliance). This confirms previous research on the effects of ankle foot orthoses on MG morphology (3). BoNT-A on the other hand, affected the muscle's resting length, however without gain in extensibility or MTU-length. This emphasizes the requirement to combine both treatments, but also cautions the use of stretching casts for having adverse effects on the tendon. The treatment-effects on the MTU on the long-term and their carry over effect to gait is material for further investigation

Is One Trial Sufficient to Obtain Excellent Pressure Pain Threshold Reliability in the Low Back of Asymptomatic Individuals? A Test-Retest Study.

The assessment of pressure pain threshold (PPT) provides a quantitative value related to the mechanical sensitivity to pain of deep structures. Although excellent reliability of PPT has been reported in numerous anatomical locations, its absolute and relative reliability in the lower back region remains to be determined. Because of the high prevalence of low back pain in the general population and because low back pain is one of the leading causes of disability in industrialized countries, assessing pressure pain thresholds over the low back is particularly of interest. The purpose of this study study was (1) to evaluate the intra- and inter- absolute and relative reliability of PPT within 14 locations covering the low back region of asymptomatic individuals and (2) to determine the number of trial required to ensure reliable PPT measurements. Fifteen asymptomatic subjects were included in this study. PPTs were assessed among 14 anatomical locations in the low back region over two sessions separated by one hour interval. For the two sessions, three PPT assessments were performed on each location. Reliability was assessed computing intraclass correlation coefficients (ICC), standard error of measurement (SEM) and minimum detectable change (MDC) for all possible combinations between trials and sessions. Bland-Altman plots were also generated to assess potential bias in the dataset. Relative reliability for both intra- and inter- session was almost perfect with ICC ranged from 0.85 to 0.99. With respect to the intra-session, no statistical difference was reported for ICCs and SEM regardless of the conducted comparisons between trials. Conversely, for inter-session, ICCs and SEM values were significantly larger when two consecutive PPT measurements were used for data analysis. No significant difference was observed for the comparison between two consecutive measurements and three measurements. Excellent relative and absolute reliabilities were reported for both intra- and inter-session. Reliable measurements can be equally achieved when using the mean of two or three consecutive PPT measurements, as usually proposed in the literature, or with only the first one. Although reliability was almost perfect regardless of the conducted comparison between PPT assessments, our results suggest using two consecutive measurements to obtain higher short term absolute reliability