By K. Missy Ball, MT, PT, ATP, Pediatric NDT | Posture and position are two distinctly different terms, used interchangeably by seating and mobility specialist. Position describes the location of an object in space. It is nonresponsive-passive. Posture is dynamic, multifaceted in regard to what can influence it. When someone talks about positioning a client, immediately what comes to mind is statically addressing the client-evaluating range of motion limitations, skeletal deformities, pressure distribution and comfort needs. Posture, on the other hand, is fluid, ever able to receive input and possibly change in some manner. Postural stability is the ability to manage one’s center of mass over one’s base of support. Postural orientation is the ability to orient the body to perform a specific task. Both of these are dynamic skill sets. Throughout the day individuals manage changes in weight distribution to keep stable as well as to perform everyday tasks-putting on shoes, lifting a fork of food to the mouth.
So what impacts posture?
There are many influences on posture including: Skeletal alignment, muscle strength/endurance, neuromotor status (muscle tone, force generation & scaling of force, interplay between different muscle groups around a specific joint), 4 sensory systems, sensory-motor strategies learned through experience, and cognitive influences. These can enhance or diminish one’s postural fluidity. For instance, unrelenting spasticity can overtime reduce joint range of motion, as well as impact on muscular balance at the specific joint. Contractures can develop limiting potential. Skeletal deformities which can develop for several reasons can also hamper postural control. In clients diagnosed with the various types of cerebral palsy, multiple variables, including tonal abnormalities, muscle weakness or imbalance, sensory issues, can offset normal skeletal alignment during motor development.
For example, when propping on elbows, the general population biomechanically places elbows forward or directly under shoulder girdle, which provides a biomechanically advantage for the middle trapezius & rhomboids to activate and produce spinal extension. In clients with quadriplegia cerebral palsy, the spastic muscle groups of pectorals, rectus abdominus and tight scapular-humeral muscles change the skeletal alignment. The elbows are pulled back of the shoulder, so with effort these muscles produce flexion of the trunk reducing spinal extension needed for further gross motor progress. Also, internal rotation occurs in the arms which over time produces heavy load to the prehensile side of the hand which interferes with fine motor activities. Hence, they learn to couple the wrong muscle groups (synergy) together for a specific task that limits their full postural potential. A therapist working with children will attempt to intervene and facilitate more effective sensory-motor strategies before they are habituated to allow greater improvement in gross and fine motor functional skills and preservation of the musculoskeletal system. Seating & mobility equipment as well as therapy can be useful here.
An intelligent 4 year old male diagnosed with spastic diplegia CP was being followed by an neurodevelopmental certified OT for several months when family requested PT. The OT had been working on beading to improve active forearm supination. His mode of mobility in the home was commando crawling, which he performed rapidly throughout the home regularly. He had just received a scooter with central tiller. Family’s goal was independent ambulation. On observation, the boy used a rolling front walker with moderate assistance at least and much lower extremity scissoring with limited reciprocity. When asked to draw his body image, he drew a single line for his torso and legs, 2 lines for his arms and a circle for his head. He rarely felt dissociation of his legs, therefore drew only one line to represent both torso and legs. Body image is learned and movement is a major way in which one learns it.
The muscle synergy he used to stabilize his pelvis was hip flexors, adductors, internal rotators and hamstrings. This produced limited segregation of his legs during walking, much scissoring, and limited postural stability. When squeezing the tiller on the scooter, due to his weak grip strength he pulled in the muscular strategy of pectorals and central abdominals, producing a rounded spine and humeral internal rotation further impairing his fine motor capability and spinal extension. This is the strategy he used to commando crawl and had habituated. He also crushed the pommel with his knees. So what could be done?
He is only 4 years old with many years ahead of him. Do not feed into strategies that are limiting him functionally. There was an attendant switch on the scooter, so the mother drove him one block to school and he used it intermittently on his own at school. The better choice for long distances would have been a power chair with joystick mounted off to side with intermittent anterior sloped seat or a front wheel drive manual wheelchair set up specifically for him. A trial manual wheelchair was introduced with a seat that could be flat or anteriorly tipped periodically throughout the day, with the footplate moved back to disadvantage the hamstrings from use. The sloped seat challenged his postural stability which elicited active buttock muscles, with lateral hip muscles. No abduction pommel was used or needed, whereas in the scooter he crushed the pommel with his knees. The drive wheel was positioned where he would engage the wheel about 10:30-11:00 position and push off near 12:30-1:00 position with shoulder flexion, external rotation and scapular depression facilitating thoracic extension. When placed in this chair, he immediately sat erect with legs separated without support and stated, “this is it” and took off pushing the chair all over the house with effective spinal extension evident. The front rolling walker was changed to a Kaye walker to facilitate external rotation of the humerus when arms were loaded which in turn encouraged spinal extension. His ambulation did improve as he used more effective muscle strategies.
Another scenario involves a low tone, intellectually limited child who is able to prop sit with upper extremities, but does not have the strength or endurance to sit independently, has no form of mobility and is not capable of propelling a manual wheelchair.
The Convaid Trekker wheeled mobility base would benefit this client. The Trekker has 5 degrees of anterior tilt and 45 degrees of posterior tilt. The anterior tilt can be used brief periods throughout the day to facilitate spinal and hip extension essential for independent sitting without arms and improvement in overall postural control essential for advancement in gross and fine motor skills. This could happen during feeding or fine motor activities. The posterior tilt can be used intermittently for comfort, pressure relief, and assist with anti-gravity positioning for the skeletal system. This base also has adjustable recline up to 170 degrees which would allow for diaper changes and age appropriate rest.
Choosing Accommodation instead of Intervention
It does not always work like the above cases. In the above cases, time was needed to practice more effective sensory motor strategies which these children could accomplish. What is practiced often is what will be used- habituated. Skeletal limitations (contractures, skeletal deformity), muscle imbalance, muscle tone may progress and limit effective change. From another perspective, after many years of moving a certain way, who are we to challenge how one moves. Some of these movement strategies maybe more effective than one realizes. Hence accommodating the individual would be the way to go, capitalizing on their movement to increase function wherever possible. Pressure relief, increasing sitting tolerance, reducing skeletal deterioration and at least maintaining their functional status at present are the goals. If the client is cognitively intact, the team should ask the client what their goals are, as well as ask about their living environment, assistance available to them, and mode of transportation. Engaging the client and/or caregivers in the decision making process will increase their input and interest as well as motivation to use the prescribed equipment.
Karen “Missy” Ball, MT, PT, ATP, who is the former Acting Director and Assistant Director of the Physical Therapy Department at Children’s Hospital in New Orleans. She was the co-director of the seating program at the hospital for a 10-year period as well as a consultant for the United Cerebral Palsy Center’s seating clinic. She served as educational specialist for Freedom Designs for 21 years and presently is an educational consultant for Convaid Products, LLC and R82, Inc. She has lectured both nationally and internationally on seating and mobility for over 20 years. She has a private practice specializing in pediatric neurology. She is an ATP and is certified in pediatric NDT with a focus on improving function through treatment and equipment.