Anja Van Campenhout

Personalized MR-based musculoskeletal models compared to rescaled generic models in the presence of increased femoral anteversion: effect on hip moment arm lengths.

Advanced biomechanical analysis of muscle function during gait relies on the use of a musculoskeletal model. In clinical practice, personalization of the model is usually limited to rescaling a generic model to approximate the patients anthropometry, even in the presence of bony deformities, as in the case of cerebral palsy (CP). However, the current state of the art in biomechanics allows highly detailed subject-specific models to be built based on magnetic resonance (MR) images. We hypothesized that moment arm length (MAL) calculations from MR-based models would be more accurate than those from rescaled generic musculoskeletal models. Our study compared hip muscle MAL estimated by (1) a personalized model based on full-leg MR scans and (2) a rescaled generic model of both lower limbs in six children presenting with increased femoral anteversion. Personalized MR-based models were created using a custom-built workflow. Rescaled generic models were created based on three-dimensional positions of anatomical markers measured during a standing trial. For all 12 lower limb models, the hip flexion, adduction and rotation MAL of 13 major muscles were analyzed over a physiological range of hip motion using Software for interactive musculoskeletal modelling (SIMM) (Motion Analysis Corporation, USA). Our results showed that rescaled generic models, which do not take into account the subjects femoral geometry, overestimate MAL for hip flexion, extension, adduction, abduction and external rotation, but underestimate MAL for hip internal rotation. The differences in MAL introduced by taking the aberrant femoral geometry into account in the MR-based model were consistent with major gait characteristics presented in CP patients.

The use of botulinum toxin A in children with cerebral palsy, with a focus on the lower limb

PurposeThe purpose of this review is to clarify the role of botulinum toxin serotype A (BTX-A) in the treatment of children with cerebral palsy (CP), with a special focus on the lower limb.BackgroundThe treatment of spasticity is central in the clinical management of children with CP. BTX-A blocks the release of acetylcholine at the motor end plate, causing a temporary muscular denervation and, in an indirect way, a reduced spasticity. Children with increased tone develop secondary problems over time, such as muscle contractures and bony deformities, which impair their function and which need orthopaedic surgery. However in these younger children, delaying surgery is crucial because the results of early surgical interventions are less predictable and have a higher risk of failure and relapse. As BTX-A treatment reduces tone in a selective way, it allows a better motor control and muscle balance across joints, resulting in an improved range of motion and potential to strengthen antagonist muscles, when started at a young age. The effects are even more obvious when the correct BTX-A application is combined with other conservative therapies, such as physiotherapy, orthotic management and casts. There is now clear evidence that the consequences of persistent increased muscle tone can be limited by applying an integrated multi-level BTX-A treatment approach. Nevertheless, important challenges such as patient selection, defining appropriate individual goals, timing, dosing and dilution, accuracy of injection technique and how to measure outcomes will be questioned. Therefore, “reflection is more important than injection” remains an actual statement.

Motor function following multilevel botulinum toxin type A treatment in children with cerebral palsy

This study evaluated the effects of multilevel botulinum toxin type A (BTX‐A) treatments on the gait pattern of children with spastic cerebral palsy (Gross Motor Function Classification System Levels I‐III). In this nested case—control design, 30 children (mean age 6y 11mo [SD 1y 5mo]; 21 males, nine females; 19 with hemiplegia, 11 with diplegia) were treated according to best practice guidelines in paediatric orthopaedics, including BTX‐A injections. A matched control group of 30 children (mean age 7y 8mo [SD 1y 10mo]; 13 males, 17 females; 19 with hemiplegia, 11 with diplegia) were treated identically, but without BTX‐A. Motor development status at 5 to 10 years of age was assessed by means of three‐dimensional gait analysis at a mean time of 1 year 10 months (SD 10mo) after the last BTX‐A treatment. The control group showed a significantly more pronounced pathological gait pattern than the BTX‐A group. Major differences were found for pelvic anterior tilt, maximum hip and knee extension, and internal hip rotation. These results provide evidence for a prolonged effect of BTX‐A and suggest that BTX‐A injections, in combination with common conservative treatment options, result in a gait pattern that is less defined by secondary problems (e.g. bony deformities) at 5 to 10 years of age, minimizing the need for complex surgery at a later age and enhancing quality of life.

Localization of the motor endplate zone in human skeletal muscles of the lower limb: anatomical guidelines for injection with botulinum toxin

Aim  Botulinum toxin gives a local tone reduction by blocking neurotransmission at the motor endplate (MEP). The importance of using MEP‐targeted injections is demonstrated in animal models and in a clinical human study. The goal of this review is to present the available data on the localization of the MEP zone of frequently injected muscles of the lower limb and to compare this with current practice.

Long-term use of botulinum toxin type A in children with cerebral palsy: Treatment consistency

At the University Hospital of Pellenberg (Belgium), more than 1000 patients have been treated with Botulinum toxin type A (BTX-A) over the last decade. Ten percent of these patients (n=106) received multiple (at least four times), multi-level, high-dosage treatments. The aim of this study was to evaluate the stability of dosage and treatment intervals in long-term, multi-level, high-dosage treated children with cerebral palsy and to evaluate the evidence for a safe and stable response to this treatment. Data on disease, age, dosage and target muscles were extracted for each treatment session of 106 patients who received multiple BTX-A treatment sessions. Patients had a follow-up of 4y 6mo (range 1y 8mo-8y 9mo) on average and received 4 to 12 BTX-A treatments within the period of January 1996 and December 2005. Patients received a mean dosage of 23.5+/-5.2U/kgbw at first treatment with stable subsequent values. Mean dosages for children with diplegia, hemiplegia and quadriplegia were 24.5+/-4.7U/kgbw, 15.9+/-3.7U/kgbw and 22.0+/-4.8U/kgbw, respectively. Mean age at first treatment was 4y 6mo (range 1y 11mo-18y 10mo) with a majority of patients (76.4%) first treated within 2 and 4y of age. Treatment intervals of approximately 1y remained stable within four, five and six subsequent treatments. Long-term, high-dosage, multi-level BTX-A applications can be considered as a safe and stable treatment option for children with cerebral palsy and the formation of antibodies, responsible for secondary non-response, can be indirectly precluded.

Spasticity and Its Contribution to Hypertonia in Cerebral Palsy

Spasticity is considered an important neural contributor to muscle hypertonia in children with cerebral palsy (CP). It is most often treated with antispasticity medication, such as Botulinum Toxin-A. However, treatment response is highly variable. Part of this variability may be due to the inability of clinical tests to differentiate between the neural (e.g., spasticity) and nonneural (e.g., soft tissue properties) contributions to hypertonia, leading to the terms “spasticity” and “hypertonia” often being used interchangeably. Recent advancements in instrumented spasticity assessments offer objective measurement methods for distinction and quantification of hypertonia components. These methods can be applied in clinical settings and their results used to fine-tune and improve treatment. We reviewed current advancements and new insights with respect to quantifying spasticity and its contribution to muscle hypertonia in children with CP. First, we revisit what is known about spasticity in children with CP, including the various definitions and its pathophysiology. Second, we summarize the state of the art on instrumented spasticity assessment in CP and review the parameters developed to quantify the neural and nonneural components of hypertonia. Lastly, the impact these quantitative parameters have on clinical decision-making is considered and recommendations for future clinical and research investigations are discussed.

Is an Instrumented Spasticity Assessment an Improvement Over Clinical Spasticity Scales in Assessing and Predicting the Response to Integrated Botulinum Toxin Type A Treatment in Children With Cerebral Palsy

OBJECTIVE To compare responsiveness and predictive ability of clinical and instrumented spasticity assessments after botulinum toxin type A (BTX) treatment combined with casting in the medial hamstrings (MEHs) in children with spastic cerebral palsy (CP). DESIGN Prospective cohort study. SETTING Hospital. PARTICIPANTS Consecutive sample of children (N=31; 40 MEH muscles) with CP requiring BTX injections. INTERVENTION Clinical and instrumented spasticity assessments before and on average ± SD 53±14 days after BTX. MAIN OUTCOME MEASURES Clinical spasticity scales included the Modified Ashworth Scale and the Modified Tardieu Scale. The instrumented spasticity assessment integrated biomechanical (position and torque) and electrophysiological (surface electromyography) signals during manually performed low- and high-velocity passive stretches of the MEHs. Signals were compared between both stretch velocities and were examined pre- and post-BTX. Responsiveness of clinical and instrumented assessments was compared by percentage exact agreement. Prediction ability was assessed with a logistic regression and the area under the receiver operating characteristic (ROC) curves of the baseline parameters of responders versus nonresponders. RESULTS Both clinical and instrumented parameters improved post-BTX (P≤.005); however, they showed a low percentage exact agreement. The baseline Modified Tardieu Scale was the only clinical scale predictive for response (area under the ROC curve=0.7). For the instrumented assessment, baseline values of root mean square (RMS) electromyography and torque were better predictors for a positive response (area under the ROC curve=.82). Baseline RMS electromyography remained an important predictor in the logistic regression. CONCLUSIONS The instrumented spasticity assessment showed higher responsiveness than the clinical scales. The amount of RMS electromyography is considered a promising parameter to predict treatment response.

Localization of motor nerve branches of the human psoas muscle

Endplate‐targeted botulinum toxin injections can achieve optimal neuromuscular blockade. The goal of this study was to identify the motor endplate (MEP) zone in the human psoas muscle through dissection. In 24 human cadaver psoas muscles the nerve branches and their intramuscular course were followed by stereoscopic microscopic dissection as far as their terminal ramifications. From the lumbar plexus, an average of 3.7 (range 2–7) nerve branches enter the psoas muscle. The proximal and distal limit of the MEP‐zone are situated at about 30% and 70%, respectively, of the distance between the twelfth thoracic vertebra (Th12) and the passing of the psoas under the inguinal ligament. In reference to the sacral promontory (P), these limits are respectively from 50% of the Th12‐P distance to 20% of the P‐pubis distance. This study of the MEP zone of the human psoas muscle can allow the clinician to inject BTX‐A close to its site of action. Muscle Nerve, 2010

Botulinum toxin type A treatment in children with cerebral palsy: evaluation of treatment success or failure by means of goal attainment scaling

BACKGROUND There is considerable variability in the amount of response to BTX-A treatment between and within patients with cerebral palsy (CP). AIMS The purpose of this retrospective cohort study was to evaluate the clinical responsiveness of Botulinum toxin type A (BTX-A) treatment in children with CP and specifically delineate features of treatment success and failure. METHODS Four hundred and thirty-eight children (251 boys, 187 girls; mean age 8 years 2 months, SD 4 years) were included into the study. Goal Attainment Scaling (GAS) was used to classify and evaluate treatment efficacy. Two study groups were defined: one group with an excellent response (GAS≥60.0) and one group with a lack of response (GAS≤40.0) to BTX-A. RESULTS Seventy-five patients (17.1%) had an excellent response and treatment was found to be unsuccessful for 31 patients (7.1%). Children with a lack of response to BTX-A were significantly older compared to children with a high responsiveness (p=0.0013). In the latter group, more children received multi-level injections and fewer children had injections in proximal parts of the lower limb compared to the low responsiveness group (p=0.0024). Moreover, there was a significant difference in the use of different types of casts between both study groups (p=0.0263). CONCLUSION Age, level of treatment and casting seem to be crucial features of BTX-A treatment success or failure in children with CP.

Does functional treatment of idiopathic clubfoot reduce the indication for surgery? Call for a widely accepted rating system.

We present our experience of treatment by physiotherapy, continuous passive motion and strapping in a series of 100 clubfeet classified on a scale of severity according to Dimeglio. Twenty-five percent were good after conservative treatment, and 75% required an operation. There were no recurrences or additional procedures. Before the introduction of the functional treatment in our department, 100% required some sort of surgical intervention and 51% required an additional procedure. In comparison with the results published by Dimeglio et al., the greatest discordance is observed in grade 2 clubfeet.