BOTULINUM TOXIN A IN THE TREATMENT OF EQUINUS FOOT IN DIPLEGIC CHILDREN
by Dimitris Metaxiotis, MD
and Leonhard Doederlein, MD,
Medical Director of Gait Analysis Laboratory, Department of Orthopaedic Surgery,
University of Heidelberg, Schlierbacher Lanstr. 200A, 69118 Heidelberg, German
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Botulinum Toxin A - injection in the gastrocnemius muscle |
The Gait Analysis Laboratory is located in the Department of Orthopaedic Surgery of the University of Heidelberg, which is one of the largest orthopaedic clinics in Germany. The Laboratory has been in clinical operation since 1993 and features a six camera Vicon 370 system with two Kistler force platforms, an eight channel surface and a four channel fine wire EMG system (Neurodata - Noraxon), a Novel EMED SF platform and a Cosmed K2 oxygen consumption measurement system. In the past five years 974 patients and 100 “normals” were examined, and 1433 instrumented gait analyses, 282 foot pressure measurements, 1243 videos and 142 oxygen consumption measurements completed. Processing of the kinematic - kinetic data is performed with the Vicon Clinical Manager imported into a specially designed database program. Movement of the trunk is measured using the latest Vicon BodyBuilder version.The gait lab staff consists of a multi-disciplinary team which is working closely together in both clinical and research fields. The main focus is on cerebral palsy and also on spina bifida, sport injuries, orthoses, prostheses and foot deformities. Current research projects include Btx-A and shock wave therapy, operative techniques for CP children and foot modelling.
Introduction
The management of spasticity is a challenging field in paediatric orthopaedics. Spastic equinus foot is the most common deformity in ambulatory children with cerebral palsy (CP). The later outcomes of such an untreated foot include fixed contractures that require surgical treatment. The conservative treatment aims at a functional improvement and to postpone a necessary operation. One interesting option is treatment of the spastic calf muscles with Botulinum Toxin A (Btx-A) injections.
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Marker placement on an eight year old diplegic patient. |
Btx-A acts at the neuromuscular junction (motor end-plate), by blocking the acetylcholine release from the presynaptic nerve terminal synapse and leads to a temporary, reversible chemical denervation of the injected muscle changing a spastic paresis to a flaccid one. The introduction of Btx-A therapy has extended our treatment options in CP patients with opisthotonus, upper extremity and hip adductor spasticity but is predominantly used in diplegics and hemiplegics with lower limb involvement such as pes equinus.
Our experience with Btx-A in diplegic CP children, focused on 72 patients (30 males, 42 females), all included in a study design which was approved by the local Ethics Committee. Age range was between 2.5 to 10.4 years (mean 6.1). Inclusion criteria were: ambulatory (with or without walking-aids), spastic diplegia, dynamic equinus foot, no fixed contractures and no previous surgeries.
Examination protocol
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The Gait Laboratory staff at Heidelberg's Orthopaedic Clinic. From left to right, back row: Dr. Leonhard Doederlein, Orthopaeidic surgeon, Head of the department for cerberal palsy and technical orthopaedics; Alexander Pappas, Lab technician; Dimitrios Metaxiotis, Orthopaedic surgeon. Front row: Dr. Andrea Siebel, Lab co-ordinator, Sport scientist, PT; Waltraud Schuster, Medical technical assistant; Walter Accles, Research Assistant. |
All patients were recruited from our special routine cerebral palsy studies and underwent clinical examination and 3-D instrumented gait analysis including videotaping, kinematics, kinetics and surface EMG. Examinations were performed pre- and 4-6 weeks after injection. A further gait analysis was performed 4.5 - 6 months after injection to document any effects after cessation of the action of Btx-A.
Furthermore a questionnaire documented the parents’ and physiotherapists’ evaluation and impressions for the first 4 - 6 weeks. For the gait parameters significance was assumed at p < 0.05.
Injection protocol
Btx-A was injected in a dilution of 500 Units of Dysport® in 3 ml NaCl 0.9%.
Both gastrocnemius and soleus muscles were injected laterally and medially at four sites. Almost all children were sedated before the injection with Midazolam (Dormicum®) which was rectally given in a dosage of 0.1 ml/ Kg Body Weight. The injection sites were numbed using ice-spray (chlorethyl).
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Clinical examination of the same patient. |
Dosage
15 - 37 Units Dysport®/ Kg BW were divided into two calves giving a total dose of 150 - 300 Units Dysport® per calf. The total dosage was determined from the clinician, taking into account the degree of spasticity according to the modified Ashworth-Scale, the muscle volume, the body weight and the gait analysis.
Results
Clinically there was a reduction of the spasticity noticed on the first examination (4 - 6 weeks) after the injection.
Time distance parameters
Velocity, cadence, stride length and stride duration showed no significant statistical differences. This can be explained from the self selected speed of the patients.
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The dark line represents the curves pre-injection and the broken line 6 weeks post-injection. The grey area reflects the normal values. |
Kinematics
We investigated the following kinematic parameters: ankle angle at initial contact, maximum ankle dorsiflexion during stance and maximum dorsiflexion during swing. All measured parameters showed statistically significant improvement.
Kinetics
We collected kinetic data from only 31 out of 72 patients because of insufficient step length and the use of assistive devices by some patients.
We measured the plantar flexion moment at the end of first double support, the total power (range of power absorption/ generation) during the first third (0 - 30%)of the gait cycle, and peak power at second double support considering them to be the most important parameters.
A statistically significant improvement could be found in peak power at second double support at 6 weeks post injection (p = 0.0083) and in max. plantar flexion moment, 4.5 - 6 months after injection (p = 0.0339).
In our example a ten year old boy with spastic diplegia and spastic equinus foot was injected in both calves. His left side (which is presented on the diagram above) was injected with 300 Units Dysport® which was divided into 200 Units for gastrocnemius and 100 Units for soleus muscles. In the kinematics study the extreme ankle plantarflexion during the whole gait cycle before the injection, reached the normal values 6 weeks after the injection.
In the kinetics investigation the typical double bump ankle pattern of the ankle moment, as well as the absorption-generation pattern in the power diagrams, was diminished.
Discussion
The aim of this paper is not to discuss the advantages and disadvantages in comparison with other conservative treatments or to examine the side effects and duration of the effect. There are still some issues which have to be examined further, such as repeatability and antibody formation. Nevertheless, the question as to whether surgery can be postponed or even avoided could not be answered until now. Generally the use of Btx-A proved from our experience to be an effective, safe and easily applicable method for temporary treatment of the dynamic spastic equinus foot in children with spastic diplegia. Repeated injections into the calves remain effective as long as there are no fixed contractures. Older children (above 8 years) seem to gain less from this therapy. Btx-A supports the physiotherapy and the better tolerance of night splints.