DON T JUST PROVIDE A BAND-AID ELIZABETH COLE, MSPT, ATP U.S. Rehab / VGM Selecting the most appropriate product solutions for specific postural problems should be a thoughtful exercise in analyzing the clinical evaluation results, matching the results to product parameters and choosing appropriate products to provide these features. One of the most important steps in the analysis is to identify the specific cause of the postural abnormality before choosing a solution. Merely treating the postural issue with generic solutions will only serve to put a Band-aid on the problem and may actually cause further harm. By identifying the specific cause we can choose solutions that specifically address that cause, appropriately correct or accommodate the problem and prevent further deformity. There are many times when a person sits in a postural deformity because of an intrinsic physical, functional, behavioral or cognitive limitation. Unfortunately, there are also many times when the posture is caused by an inappropriate feature, configuration, option or dimension of the seating or wheelchair frame. The following paragraphs will examine the potential physical causes and equipment causes of each of the primary postural deformities that we encounter in our seating and mobility evaluations. Equipment Causes of Posterior Pelvic Tilt and Thoraco-Lumbar Kyphosis A posterior pelvic tilt occurs when the pelvis rotates back and the ischial tuberosities slide forward on the seat surface. This results in a rearward lean of the trunk and a field of vision that is no longer level in the vertical plane. To achieve an upright head and a level eye gaze, the trunk curves forward, flattening the lumbar spine and increasing kyphosis in the thoracic spine. Poor seat and back support if the pelvis and trunk are not sufficiently supported, it may be difficult or impossible for an individual to maintain a neutral pelvis and upright trunk, especially if there is compromised strength, tone or balance along with prolonged sitting. Old, overstretched upholstery and/or a non-supportive cushion provide little support for the pelvis and lower extremities and are primary culprits in causing the individual to slide into a posterior pelvic tilt and kyphotic trunk. Armrests are too low many individuals need armrest support to help maintain upright posture or as a place to rest the upper extremities during periods of rest. If the armrests are too low, these individuals must either slide the hips forward in the seat to lower themselves in the wheelchair or curl the trunk forward to reach the armrests. Either way, the result is a posterior pelvic tilt and increased kyphosis. Footrests are too low - in order to maintain good pelvic and trunk position, the feet should rest firmly on the footplates such that they are weight bearing and the upper legs are parallel to the seat surface. If the footrests are too long, the legs hang down and the pelvis is pulled forward on the seat. Seat depth is too long if the seat depth is too long, the sling upholstery or cushion will press into the back of the knee, causing circulatory compromise, discomfort, numbness and tingling. Over time, the individual will tend to slide forward in the seat to relieve the pressure, resulting in a posterior pelvic tilt and subsequent kyphosis. In some cases, the person may be unable to sit in a neutral pelvis at all, since the excessive seat depth will prevent the pelvis and hips from reaching the back of the seat altogether. Back height is too high or too low a back height that is too high this can create a feeling of being pushed forward, especially if the wheelchair is oriented vertically with no tilt in the frame. The individual may slide into a posterior pelvic tilt to maintain stability. On the other hand, if the back is too low and does not provide sufficient support, the individual will slide the pelvis forward to sit lower in the seat. 34
Seat to floor height is too high to effectively propel a wheelchair with one or both legs, an individual must be able to reach the ground with the heel(s). If the STFH is too high, the heel(s) cannot access the ground and the individual may slide the pelvis forward in the seat to effectively lengthen the leg(s). Physical Causes of Posterior Pelvic Tilt and Thoraco-lumbar Kyphosis Weak core muscles and decreased balance and postural stability maintaining the resting contractions of the trunk, pelvis and hips muscles that are necessary to sit in an upright normal posture against gravity can be difficult/impossible for many individuals with physical limitations. These individuals tend to slide into a posterior pelvic tilt and kyphotic posture in order to maintain some kind of stability in the chair. Spasticity extreme extensor spasticity can cause extension in the spine, pelvis and lower extremity muscles, which causes the hips and pelvis to slide forward in the seat into a posterior pelvic tilt. Hip extension contractures in order to sit in a fully upright position in a standard 90 degree seat to back angle, the individual must be able to flex the hip to at least 90 degrees. A significant extension contracture in one or both hips may make this degree of flexion unachievable. Unable to get the hips to the back of the seat, the individual will be forced to slide further forward into a posterior pelvic tilt. Tight hamstrings the hamstrings are 2-joint muscles that originate at the ischial tuberosities, cross over the back of the hip joint, cross over the back of the knee joint and insert at the back of the tibia. If an individual has tight hamstrings and the leg is pulled into extension to place it on a footplate, the end of the available stretch of the muscles may be reached. Further tugging beyond this point will pull the ischial tuberosities forward, causing the pelvis to rotate posteriorally. Obesity Many severely obese individuals carry much of their excess weight in their abdominal region. A significant amount of redundant tissue in this area can make it difficult for the individual to sit in 90 of hip flexion. He/she is forced to tilt the pelvis back and sit in a posterior pelvic tilt. Equipment Causes of Anterior Pelvic Tilt and Lumbar Lordosis An anterior pelvic tilt occurs when the pelvis rotates forward, resulting in a forward lean in the trunk and a field of vision that is no longer vertically level. To achieve an upright head and a level eye gaze, the individual will curve the trunk back and increase the lumbar lordosis. Poor seat and back support probably the most common equipment cause of an anterior pelvic tilt / lumbar lordosis is inadequate support from the seat and/or back of the wheelchair, which makes it difficult or impossible for an individual with compromised strength, tone or balance to maintain a neutral pelvis and upright trunk. One strategy to prevent loss of balance and upright posture against the force of gravity is to essentially stack the head, spine and pelvis in an anterior pelvic tilt and severe lumbar lordosis. Physical Causes of Anterior Pelvic Tilt and Lumbar Lordosis Decreased balance or stability - as is the case when there is inadequate support from the equipment, some individuals with decreased strength and tone in the core muscles will position the pelvis into an anterior pelvic tilt and extend the lumbar spine in order to stack the body to create a stable posture. Weak abdominal muscles weak and over-stretched abdominal muscles do not exert sufficient pull on the pelvis to keep it in proper position, allowing the pelvis to tip forward into an anterior tilt. Tight hip flexors or flexion contractures permanently shortened hip flexors and/or tightness in the joint capsule and connective tissue can result from prolonged positioning in flexion (i.e., in bed), 35
hypertonicity, trauma or surgery. In extreme cases, the muscles pull on the pelvis, resulting in an anterior pelvic tilt. Hyperflexibility Too much flexibility in the lumbar spine can cause a significant increase in the amount of lumbar lordosis or lumbar curve. The pelvis must rotate forward into an anterior pelvic tilt as the individual attempts to maintain balance and a level field of visual. Equipment Causes of Pelvic Obliquity, Scoliosis and Lateral Neck Flexion A pelvic obliquity occurs when the pelvis tilts to one side, resulting in a lateral lean of the trunk and a field of vision that is no longer horizontally level. To achieve midline, the individual will curve the trunk towards the other side, resulting in a scoliosis. Poor seat support a pelvic obliquity is often caused by poor support under the pelvis, such as that provided by loose, overstretched sling upholstery. For individuals with deficits in strength, range of motion, coordination and endurance, it is virtually impossible to sit with a level pelvis on such a surface. It should be noted that a cushion is not always a sufficient remedy to over-slung upholstery, since the cushion will most likely, over time, assume the curve of the upholstery, even if it has a firm foam base. Seat width too wide a seat that is too wide for an individual s anatomy will not support the lateral pelvis, allowing it to slide to one side into a pelvic obliquity. A seat that is too wide will also position the armrests further from the individual s upper extremities. To gain support under at least one arm and/or to reach a joystick or other power wheelchair control, he/she will lean to that side. Armrests too low if the armrests are too low for the individual to comfortably and easily reach with both upper extremities, he/she will most likely lean to the side to access at least one. Footplates at different heights if the footrests are not adjusted evenly, one footplate will be higher than the other. This forces one side of the pelvis up, creating a pelvic obliquity. Back support too low if the back support is too low, some individuals will seek out support from the trunk, by tilting the pelvis to the side and leaning the spine against one of the back posts. Solid support too narrow a common remedy to over-stretched upholstery is to place a solid board between the cushion and the sling upholstery to provide a solid support. However, if the board is not quite wide enough to span the side rails of the wheelchair, it can slip off one side rail and down into the upholstery. This uneven base will force the pelvis to sit in an obliquity. Cushion does not support trochanters some wheelchair cushions have contours in the rear of the cushion that create a posterior well. This well may be designed such that the greater trochanters are supported on the edges, while the ischial tuberosities sit into it. If the well is too wide, one trochanter might be supported on one edge, but the other will fall into the well, creating a lateral tilt in the pelvis. Physical Causes of Pelvic Obliquity, Scoliosis and Lateral Neck Flexion Asymmetry in muscle strength or tone - a pelvic obliquity is often caused by some kind of asymmetry in the body. Weak muscles on one side of the pelvis and/or trunk may be unable to hold the hips, pelvis and spine together in correct alignment. Instead, they allow that side of the body to elongate such that the pelvis drops down on that side and the spine curves to the other side. Similarly, too much tone in the muscles of the pelvis and/or trunk may pull the pelvis and trunk together on one side, causing the trunk to shorten and the pelvis to raise on that side. Asymmetry in tissue or bony mass a decrease in the amount of tissue under one side of the buttocks can cause the pelvis to drop on this side. This decrease in tissue may be caused by a 36
number of factors. In some cases, the muscles on that side of the buttocks have atrophied due to lack of muscle tone or paralysis. In other cases, a skin breakdown under one ischial tuberosity has destroyed not only the epidermis and dermis, but also the soft tissue and perhaps even the underlying muscle tissue. With a severe skin breakdown, infection in an ischial tuberosity might require partial amputation and even greater loss of mass. Hip flexion contracture a flexion contracture in one hip may position that hip in more flexion compared to the other. In order to sit levelly on the seat surface, the pelvis must drop down on that side. Structural deformity in spine in the cases above, a spinal scoliosis results from a primary pelvic obliquity; that is, the problem occurs first in the pelvis and the spine follows. However, there are some cases when the initial issue is in the spine and the pelvic obliquity is the subsequent result. For example, a structural curvature of the vertebrae will cause a scoliosis. In order to sit upright, the individual will drop the pelvis on the opposite side, creating an obliquity. Decreased balance any compromises in balance will make it difficult for a person to maintain a midline spine. Problems with balance can result from perceptual issues, poor equilibrium and/or deceases in muscle tone or strength on one side of the body. Equipment Causes of Pelvic Rotation, Trunk Rotation and Leg Length Discrepancy A pelvic rotation occurs when one side of the pelvis rotates either to the side left such that one side is more forward or more rearward than the other. To achieve a midline trunk, head and eye gaze, the individual will rotate the trunk in the opposite direction. Poor seat and/or back support a pelvic rotation can result from poor support under the pelvis and hips and/or behind the back, such as loose or stretched sling upholstery and/or an inadequate cushion or back support. If the pelvis is not well supported and the person does not feel secure, he/she will assume any posture that provides stability and this may include rotation of the pelvis. Seat to floor height is too high to effectively propel a wheelchair with one leg, an individual must be able to reach the ground with the heel of the foot. If the STFH is too high, the individual may rotate that side of the pelvis forward to essentially lengthen the leg in order to access the ground with that heel. Seat and/or back contours too narrow contours of the seat and/or back that are too narrow may rub against the hips, pelvis and/or trunk. To avoid the resulting discomfort (and even skin breakdown), the person may rotate the pelvis and trunk in the seat to effectively make the pelvis and trunk narrower. Physical Causes of Pelvic Rotation, Trunk Rotation and Leg Length Discrepancy Asymmetry in muscle strength or tone as with pelvic obliquity, a pelvic rotation is often caused by some kind of asymmetry in the body. Weak posterior muscles on one side of the pelvis may allow stronger anterior muscles to pull that side of the pelvis forward. Or increased tone in posterior muscles on one side of the pelvis may pull the pelvis back, causing it to rotate (this time in the posterior direction). Both are often followed by rotation of the spine in the opposite direction. Unilateral hip contracture a hip extension contracture on one side will prevent the hip on that side from flexing to at least 90 degrees to sit functionally in a standard seat to back angle. Some individuals will rotate the contracted side forward to allow the other side to get to the back of the seat into 90 degrees. Primary leg length discrepancy whenever there is a primary pelvic rotation, there will be a resulting leg length discrepancy. However, the presence of a leg length discrepancy does not necessarily 37
mean that there is a pelvic rotation, since leg length discrepancies can occur due to a variety of other causes. If we assume the pelvis is rotated and attempt to realign the legs by rotating the pelvis back to normal, we will actually be creating a pelvic rotation. In these cases, we should just accommodate the leg length discrepancy through the seat support and cushion so as not to create a deformity in the pelvis. References: 1. Hetzel, T. Posture and Postural Tendencies: What s the Difference?; Proceedings from the 29 th International Seating Symposium, March 7-9, 2013:pgs 75-76 2. Kangas K. Seating For Task Performance. Rehab Management. 2002;June/July:54-56, 74 3. Hahn ME, Simkins SL. Effects of Dynamic Wheelchair Seating in Children with Cerebral Palsy. Proceedings from the 24 th International Seating Symposium. March 6-8, 2008:pgs 153-158 Speaker Bio During the last 28 years, Elizabeth has been involved in many aspects of the provision of assistive technology, including practice as a Physical Therapist, coordination of a seating and wheelchair clinic, education in seating, wheeled mobility and assistive technology and reimbursement consulting. She has lectured extensively at conferences and trade shows, and has been published in national industry journals. Elizabeth has served on the board of directors for RESNA, is a member of the Clinician's Task Force and has been involved in many industry-wide work groups dedicated to regulatory and legislative policy changes related to complex rehab technology. 38