Cerebral Palsy (CP) is a non-progressive, neurological condition which occurs due to an insult to the developing brain (Paneth, 2006). It might occur due to malformations during the prenatal development or damage to the central nervous system prenatally or perinatally (Shurtleff, 2009). It has an incidence of 1.5-2.5 per 1000 live born children (Himmelman, 2005). It is associated with motor and postural abnormalities, which may lead to functional impairment and loss of independence. There are various forms of CP such as spastic, ataxic or dyskinetic depending upon the extent of brain damage (Hagberg, 1993).
Spasticity is defined as an "motor disorder characterized by a velocity dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyper-excitability of the stretch reflex as one component of the upper motor neuron syndrome" (Lance, 1980). It arises from upper motor neuron lesions involving the brain or the brainstem, but also affects the peripheral motor systems such as joints, tendons, muscles etc. It is due to these peripheral manifestations that management of spasticity is difficult (Priori, 2006). In CP, spasticity occurs with the involvement of the motor cortex, which includes the premotor area, primary motor area and the supplementary motor area (Sheaan, 2002). When the peripheral systems are involved, spasticity is said to occur due to an increase in the excitability of the lower motor neuron which causes stretch reflexes to become hyperactive. This causes an imbalance in the responses of excitatory and inhibitory inputs to the motor neuron pool. The decrease in inhibitory inputs causes hyper-excitability of lower motor neurons, thus causing spasticity (Mayer, 2002).
The extent of the physical manifestations of CP depends upon the extent of the insult to the brain, and the cortical areas affected. The occurrence of spasticity can affect different areas and this is further be classified into monoplegia, diplegia or quadriplegia (Hagberg, 1993). Out of these, spastic diplegia (SD) occurs most commonly (Bax, 2006). SD involves lower extremities (LE) more than the upper extremities (UE), along with the trunk. There may be associated loss of head/trunk stability as postural muscle contractions get affected (van der Heide, 2004). Gross motor function loss, impaired/incorrect pattern of walking, scissoring gait, increased energy expenditure for simple tasks, incoordinated movements are some of the manifestations of SD (van der Heide, 2005).
Children with SD should be treated with a combination of various interventions such as medical, physical, surgical, chemical etc. The primary goal should be functional independence, along with prevention of secondary impairments. Conventional methods of treatment include physical therapy such as exercises on a swiss ball, passive muscle stretching, neurodevelopmental techniques, sensory integration techniques; botulinum toxin injections for spasticity management; orthopedic interventions such as tendon lengthening etc., hippotherapy and other methods to develop motor skills (Sharan, 2005).
Hippotherapy is an up and coming form of therapy which involves the use of horses in the treatment of children with SD. "Hippos" is the greek word for horse (Shurtleff, 2010), and the term "Hippotherapy" was first coined in late 1960s in Germany (Debuse, 2009). In this form of therapy, the movement of the horse is used "to challenge balance, posture and strength and to integrate sensory input (tactile, vestibular, visual and proprioceptive)" (Shurtleff, 2010). Position of the patient on the horse, and the type of movements the horse makes determines which system gets engaged. When a child sits astride a horse, its movement generates impulses which facilitate appropriate movement responses which help overcome the muscular or postural impairments. The horse is directed by a special trained handler, under the guidance of a Physiotherapist. The therapist decides the direction, speed and type of movement of the horse in order to gain maximal facilitation of the targeted motor groups. Thus, hippotherapy has been often described as a "specialist physiotherapy and rehabilitative treatment, and not a recreational activity" (Debuse, 2009).
Hippotherapy is based on facilitating appropriate motor responses through the rhythmic nature of the horses' movements. It helps to activate postural control mechanisms and righting reactions which help in increasing truncal stability (Benjamin, 2000; Casady and Nichols-Larsen, 2004; Sterba, 2002). A horse on an average takes 55 steps a minute at a medium pace. Each step causes a forward translation of its pelvis, along with its rotation in a steady rhythm. A session for 30-45 minutes provides the patient with 3000-5000 repetitions of trunk control recovery exercises. The parameters of a treatment session can be varied according to the type of response required. A change in speed with direction can be brought about by placing weaving cones, the gait and speed of the horse can be changed from a walk to a trot to a canter; or the trunk control and balance can further be challenged by carrying out the session on a challenging terrain such as an uneven surface (Clayton, 2002). The forward direction of each thrust activates different motor units in the head and trunk, thus facilitating various postural control mechanisms.
Hippotherapy is carried out in two different forms. Recreational horseback riding often has similar physiological effects on the postural mechanisms on a child with SD. In this form of therapy, a horse trainer (non therapist) guides the child into doing various activities based on his knowledge and training in this field. All safety measures are applied and a thorough analysis of the child's impairments is made, and the treatment is given based on this evaluation. Another form of hippotherapy is physical therapist directed hippotherapy. This involves therapy under the guidance of a licensed physical therapist, who plans and oversees every treatment session. The therapist takes into account the musculoskeletal as well as neurological impairments, functional limitations and gait disturbances faced by the children, which help form the basis for the treatment (Sterba, 2007).
In order to understand the extent of availability of literature in the field of hippotherapy, Laurie Snider conducted a study in 2007. This systematic review aimed to evaluate all the available literature in hippotherapy in children with CP and classify it into a particular level of evidence as per the International Classification of Functioning, Disability and Health. This study included articles which assessed the efficacy of hippotherapy on the trunk control in children with SD. According to the review, the evidence available stood at level 2A i.e. one or more fair quality randomized controlled trials with a PEDro score of 4-5 (Snider, 2007). Since then, numerous studies have been carried out to establish the efficacy of hippotherapy in reducing spasticity and encouraging trunk control.
In a systematic review done by John Sterba in 2007, a literature search for articles involving hippotherapy to improve gross motor functions was undertaken. A total of eleven studies were included which contained six studies on recreational horseback riding therapy, and five studies on physical therapist directed hippotherapy. A comparison was done between the improvements seen with recreational horseback riding therapy and a physical therapist directed hippotherapy. Five out of the six studies on recreational horseback riding therapy showed a significant improvement in gross motor functions of children with spastic CP. The five studies conducted on physical therapist directed hippotherapy showed significant gross motor improvement in the development of children with spastic CP. The population included in these studies was children with spastic CP including diplegic children and children with quadriplegia.
The review revealed that the rhythmic reciprocal gait pattern of the horse helped to regularize pelvic girdle movement in the rider, which was similar to the regular pelvic movements of ambulation children without disability. The postural and equilibrium reactions and responses improved with improvement in joint stability, better weight shifting ability and improved co-contractions with the steady movements of the horse. Dynamic postural responses to perturbations have also been shown to have improved with both the types of therapies used. The researchers have hence summarized that both forms of hippotherapy, i. e. recreational as well as physical therapist directed, are beneficial for children with gross motor impairments and trunk control impairments caused by spastic CP (Sterba, 2007).
In 2008, a randomized controlled trial was carried out by Lorraine Fernandes, which studied the effects of artificial horse riding (AHR) on postural control in children with SD. 30 children with SD were randomly but equally allocated to either the AHR group or the control group. The control group received conventional physiotherapy in the form of exercises on surfaces other than the artificial horse. Therapy sessions were carried out thrice a week for 6 weeks. The outcome measures used were the Gross Motor Functional Measure (GMFM) and the Pediatric Balance Scale (PBS). These were recorded at baseline before the intervention, and again after the intervention period was completed.
On analyzing the data, the author recorded a significant improvement in the postural control among children with SD with the GMFM. The data recorded through the PBS also showed an improvement in postural control, but it was not found to be statistically significant. The author thus concluded that postural control does improve after therapy through artificial horse riding and is beneficial in improving the gross motor functions of children with SD.
A study conducted by Tim Shurtleff in 2009 aimed to study the effects of hippotherapy on the head/trunk stability and the functional reach of the children with SD. 11 subjects with SD were considered for this study, and 8 children without disability were also recruited to gather normative data for the study. The outcome measures used for this study were the UE functional reach test and the barrel test which captured the data on video. This helped to get reliable and valid data, correlating with the actual circumstances of sitting on a horse. The data was measured at two weeks after the beginning of the intervention, within two weeks of completion of the intervention, and at 12-14 weeks after intervention. The recorded data could be observed in any direction, and this was used to analyse the postural responses to the movement of the barrel. The psychometric properties of the mechanical barrel were also reported in the study. The UE functional reach test used a simple reaching task to examine the extent of the patient's ability to reach an object, while sitting on a backless stool. The data was recorded using surface markers and measuring the distance.
In this study, participants were made to sit on the horse for 45 minutes, once a week for 12 weeks. The horse was made to walk, or trot as per the requirements with the children assuming different postures such as forward astride, side sit, quadruped etc. It also included UE exercises to encourage activities such as catching a ball, placing rings or toys in marked areas etc, along with other cognitive games such as memory games or finding toys around the arena etc.
This study revealed that there was a definite increase in the motor control of the head and the trunk in 10 out of 11 children that continued the follow up. One child did not return for follow up and hence, his data could not be included in the calculation of the results. The functional reach of the children also improved, which may be attributed to the better head and trunk control of the children (Shurtleff, 2009).
In 2009, Dorothy Debuse and her team conducted the first qualitative study to identify the effects of hippotherapy as experienced by the patients who underwent this form of therapy. 17 users with spastic CP including SD, hemiplegia and quadriplegia, between ages 4-63 were recruited for this therapy. The participant should have been treated by hippotherapy for at least six sessions and also been able to verbally communicate his/her opinions. The pediatric population was accompanied by parents who also contributed in this study. The participants were extensively interviewed on an individual basis as well as through focus group discussions. It was a semi-structured interview, where free discussion was encouraged. At no point were the questions narrow-ended or leading favourably towards hippotherapy. The questions were loosely based on the physiological and psychological effects experienced by the participants, along with their interpretation of this form of therapy.
All the participants reported a definite improvement in their motor control and ability to carry out their daily tasks. They also reported an increased carry-over effect after getting off the horse. Improved tone, trunk control and walking ability were the specific positive physiological effects reported by the participants and parents. The parents as well as the participants were of the opinion that hippotherapy was more effective than conventional therapy methods. Also, positive psychological effects such as increased confidence, increased participation level etc. highlighted the benefits of hippotherapy. Hence, the authors came to a conclusion that hippotherapy is beneficial to patients with cerebral palsy at the levels of impairment, activity and participation. It also helps to improve self-esteem. There is also an improvement in the quality of life of children with spastic CP as reported by the users themselves (Debuse, 2009).
In 2010, Tim Shurtleff conducted a pilot study to assess the changes in head and trunk stability in children with CP post hippotherapy. 6 children with SD were recruited and compared with 6 children without disability. A motorized barrel was used to test the head and trunk stability with a video motion capture system to record the data before and after the intervention period. Measurements of the antero-posterior head angles and the antero-posterior translation of the head and spine were recorded. The intervention was carried out on the horse once a week for 12 weeks. Each session lasted for 45 minutes.
The treatment sessions were planned individually for each participant as per the pre-intervention assessment. The only common criterion was the amount of time spent on the horse. During the session the children were made to maintain various positions such as side sit, forward astride, quadruped etc. Transition from one position to another was also considered a part of the session. Activities such as catching and throwing a ball, grasping objects in all planes, placing objects on other surfaces while the horse is moving etc. were incorporated to challenge the head, trunk and postural control. The speed of the horse was altered from walk to half trot to sudden halts etc. and the terrain was also changed from smooth to uneven to further challenge the motor control.
It was reported that children with SD showed a decrease in the antero-posterior translation of the trunk, along with decrease in the range of motion of the neck and head, and variability of the head angle as an effect of the perturbations. Hence, the authors concluded that rhythmic movement of the horse does help improve the head and trunk control in children with SD (Shurtleff, 2010).
Most of the studies have reported a significant improvement in the trunk control of children with CP, which has reflected in their ability to carry out their daily activities such as sitting, walking etc. One study reported an improvement in the balance of the patients, but the improvement was not significant statistically. One study has also reported an improvement in the psychological status of the patients, with increase in their self esteem and confidence to participate in social activities, along with physiological improvements in their trunk tone and motor control. The long term retention of these effects has also been reported in the studies mentioned above.
From the above review of literature, it can be inferred that hippotherapy has shown to be an effective method of treatment in children with Spastic Diplegia. Its implementation to regular practice has yielded beneficial effects, which are longitudinal in nature. Hence, it can be concluded that hippotherapy has a positive effect on the trunk control in children with spastic diplegia. It may be used in regular practice, provided the safety precautions are adhered to by the horse trainer as well as the physical therapist.