ATP Series

Asymmetry in Balance

Do you intervene? Accommodate? Or do both?



ATPs and clinicians who are recommending, determining and building the seating systems for wheelchair users are not starting on a symbolically level playing field. That’s just the nature of the seating and mobility calling.

Instead, seating teams must contend with a range of clinical challenges, including client histories, diagnoses and prognoses, and balance all of that with the client’s daily goals and environments.

The Asymmetrical Posture

One such wheelchair seating challenge is the asymmetrical posture — common due to the number of conditions that can cause its presentation.

“Asymmetry can be defined by the presentation of the body either not appearing to be identical on the left and right side, or an imbalance between the body halves,” said Lee Ann Hoffman, OT, MSc. Rehabilitation: Posture Management, Solutions Specialist/Seating & Positioning, Invacare Corp. “It’s a deviation from the symmetrical presentation — even-sided or equal presentation of the left and right side.”

“Clinical reasons for an asymmetry could include a pelvic obliquity, scoliosis or a leg-length discrepancy,” said Sam Hannah, ATP, Symmetric Designs. “Some of the causes can stem from a consumer trying to offload pressure, [or having] low muscle tone and/or poor seating.”

Steve Cousins, Ph.D., R&D director for Matrix Seating Ltd., said asymmetrical postures could be caused by “cerebral palsy, brain injury, multiple sclerosis, spinal muscular atrophy, muscular dystrophy, spina bifida and other disorders. [Or by] simple biomechanical issues, like using a canvas sling seat in a wheelchair so the pelvis can slip and sideways tilt, inducing a spinal curve, or slipping forward (too open a seat/back angle, no shaping to the seat/cushion) in a wheelchair seat so that the pelvis tilts posteriorly, affecting the natural spinal lordosis (which helps to protect the back from developing scoliosis). Causes related to the underlying clinical issues are abnormal muscle tension (pulling asymmetrically) and collapse under gravity due to muscle weakness.”

Kirsten Davin, OTDR/L, ATP/SMS, added that an asymmetrical posture can develop over time.

“In some cases, what was a minor asymmetry or a non-emergent diagnosis at one time may progress into a significant postural issue, and could eventually present with vital organ structure compromise,” she explained. “For example, a child who presents with minimally invasive scoliosis at age 3 may experience spinal stenosis, continued progression of scoliosis, and perhaps as a result of poor positioning or clinical progression, may experience pelvic involvement in the form of posterior pelvic tilt or pelvic obliquity, thus leading to issues of kyphosis or increased cervical or thoracic spine asymmetry.”

And the impact, Davin said, can be dire: “This now-significant postural asymmetry can easily cause respiratory impairments as a result of decreased lung volume capacity (from the compressed or flexed position of the trunk), thus preventing adequate air exchange. In addition to respiratory impairments, clients may experience decreased bowel and bladder function, decreased digestive function, or reduced visual field and/or functional performance of activities of daily living, as a result of continued progression of asymmetry.”

“Asymmetry can both be the result of instability or the cause of instability,” Hoffman said. “Consider if the individual experiences weakness due to a neurological condition — the weakness may result in an imbalance, and the body will no longer be able to maintain symmetry, against gravity. One side may collapse or seek support from the environment, resulting in instability.

“Asymmetry also has the ability to cause instability. If the individual is in contact with a non-shape conforming surface, then contact points between the individual and the supporting surface are reduced, resulting in potential peak pressure points and instability — e.g., a kypho-scoliotic spine, with a posterior asymmetric fullness (aka, rib-hump) positioned on a flat back seating system, is unstable, as the surface is not conforming or offering support. Therefore, the trunk will rotate (and roll) until it meets with a surface of the body which has less fullness to gain stability.”

“Fixed” vs. “Flexible” Asymmetries

Until fairly recently, asymmetrical postures were often described as fixed or flexible, to supposedly denote whether they could or could not be changed.

As it turns out (see below), those terms weren’t optimally precise, since even “fixed” asymmetries can be capable of change under certain circumstances.

Asymmetries: No Longer Fixed vs. Flexible

Fixed vs Flexible AsymmetryAs complex rehab seating evolves to better serve clients with asymmetrical postures, so does the terminology used to refer to the types of those postures.

In other words, such terminology is flexible rather than fixed.

Kirsten Davin, OTDR/L, ATP, SMS, explained: “There are two types of asymmetries. Prior to about four to five years ago, these two types of asymmetry were referred to as ‘flexible’ versus ‘fixed.’

“Recently, the preferred terminology has shifted to the terms ‘correctable’ versus ‘non-correctable,’ respectively. The reason behind the shift in terminology is due to the fact that many asymmetries were not truly fixed — rather, were flexible to a point, and fixed after a certain point. The term non-correctable is a more appropriate and widely accepted term, as it does not suggest the finality and rigidity that ‘fixed’ implies. A correctable (aka, flexible) asymmetry is an asymmetry which appears to be notable and significant when not in a supported position, although with the application of the appropriate seating supports, can be corrected to a near neutral or neutral position, thus significantly reducing or eliminating the once asymmetrical client presentation.”

Cousins said, “In the event the deformity has progressed (and symmetry has been lost), muscle length changes occur, limiting movement and subsequent correction. ‘Bony’ changes may also occur with time, limiting subsequent correction. If the bony changes have fused the bone segments, then, of course, fixed means fixed; the correction in these cases will be quite limited. My opinion is, however, that because most deformities are not fixed, then with strong enough corrective forces (assuming these are tolerated by the individual, for example, applied over large surface areas), a fixed deformity can be corrected over time, although maybe not fully. These forces have to exceed the gravitational or muscular forces that are causing the asymmetries in the first place.”

So, even “fixed” asymmetries could be at least somewhat “flexible” regarding eventual outcomes, which is why correctable and non-correctable are the preferred descriptions for asymmetries today. And a great number of factors can determine whether and how much an asymmetry can be changed.

“The clinical cause of the client’s asymmetrical posture can definitely have an impact as to whether the asymmetry has correctable or non-correctable tendencies,” Davin said. “For example, a client who presents with severe thoracic scoliosis may have rods placed surgically to aid in the prevention of continued scoliosis as he or she ages. In the event of surgical intervention and rod placement, the client will now face a definitive point at which further correction is not only be impossible (due to the surgical intervention), but harmful to the client. On a side note, this is why it is imperative to obtain a thorough medical history while performing the seating and positioning evaluation.”

Hoffman said, “To understand fixed or flexible — or correctable, as your U.K. cousins would call it — it is important to identify the difference between tissue adaptation and contracture. Pope (2007) identifies tissue adaptation as ‘the stage at which the tissues feel tight, but a full range of movement is possible on a slow stretch.’ Generally, the tissue here will be flexible or correctable to a point — through corrective positioning (following a comprehensive assessment, of course). Tissue adaptation may present as a flexible posture/correctable posture within certain parameters.”

Hoffman noted, “Bower (2008) defined contracture as shortening of muscles and tendons. Long (2014) defines the effects of a ‘plastic response,’ when too much loading occurs and the ‘elastic limit is passed,’ causing deformation. Plastic adaptation takes place in both bone and soft tissue; commonly seen examples are kyphosis, scoliosis and contracture of joints, which in turn limit ranges and result in asymmetry.”

She pointed out, “Contracture is synonymous with fixed postures, and accommodation (making allowances in the seating system for the presenting asymmetry) of the postural presentation is required. Contracture development is a gradual process. Remember that nerve tissue and blood vessels will also adapt — therefore, awareness is essential when entering into any intervention which rapidly promotes increasing tissue length, as neurological and circulatory systems may be negatively affected.”

What If There Is No Intervention?

What happens if an asymmetry is not addressed by the seating team? As is often the case in complex rehab seating and positioning… it depends.

Asked if a truly “fixed” asymmetry will worsen if it’s not corrected, Hannah said, “Typically no. Asymmetry cannot worsen or be corrected if the posture is fixed. The seating components around a fixed position are intended to give the consumer function and even pressure distribution or off-loading, if needed.”

Of course, everything changes if a supposedly fixed asymmetry isn’t entirely fixed.

“Yes,” Cousins said, “asymmetry can worsen without the appropriate seating intervention if the underlying causes — for example, abnormal muscle tension or weakness — are still present.”

Hoffman said the simple answer to whether an unaddressed asymmetry will progress is yes.

“If some individual presents with what appears to be a scoliosis, which is fixed, and no appropriate, supportive seating is proved, then it is highly probable that the posture will continue to deteriorate, and the scoliosis (Cobb angle) will increase,” she explained.

Davin used the example of a significant asymmetry that likely had a very modest beginning.

“Picture a client you may have seen in seating clinic, or imagine a client who presents with perhaps a left-sided pelvic obliquity (the left side of the pelvis is lower than the right), thus causing a left-sided scoliotic position (with the convex side of the scoliotic spine pointing toward the client’s left-hand side) with a right-sided lean (the client’s head leaning toward the right — right shoulder lower than the left, and right side of the pelvis higher than the left).

“This position could have very likely started with a very minor pelvic obliquity that was left unaddressed or not properly neutralized. This once-small pelvic asymmetry could have started as just that: a minor discrepancy perhaps due to an ill-fitting wheelchair seating system or inappropriate wheelchair cushion, which has now, due to lack of intervention, turned into not only a pelvic asymmetry, but whole trunk involvement. Furthermore, if this asymmetry is allowed to progress and remain unaddressed, it is likely that soft tissue contractures may develop as muscle tissue becomes affected by lack of movement and joint mobility potentially decreases. When an asymmetry is spotted, regardless of how insignificant it may seem at the time, it is imperative that the appropriate action be taken swiftly and effectively to neutralize the asymmetry and prevent the risk of further asymmetries from developing.”

“Seating intervention is only one part of the kaleidoscope approach, which encompasses 24-hour posture management,” Hoffman added (see sidebar). “By attempting to only address the fixed/inflexible posture through seating provision, a keyhole approach is adopted. To only provide one intervention, namely seating, which may only comprise several hours of the day over the 24-hour period, is not sufficient in the fight against body shape distortion.”

Hoffman is an ardent believer in a holistic postural support approach.

“Time spent outside of the supportive seating/wheelchair needs to become a priority, and positioning in lying is quintessential to achieving not only better seating outcomes through gentle positioning, but also has a profound effect on the quality of sleep for the individual and their caregivers,” she explained. “Furthermore, the provision of a supportive lying position can conversely serve to improve posture and restore symmetry, which in turn will have improved outcomes for sitting and positioning in the seating system.”

When & How to Intervene

Hoffman is adamant about the need to intervene when a seating team is confronted by an asymmetrical posture.

“Intervention is essential in the fight against postural deformity,” she said. “Poor posture and positioning can lead to death. Postural collapse can result in compression of the chest, which will affect respiration. Poor respiration and poor posture may increase the risk of pneumonia, through aspiration and inability to clear the lungs productively. Pneumonia can result in death.”

An asymmetrical posture can also cause pressure problems, Hoffman added: “Poor posture and positioning may result in asymmetry, which in turn may present as deformity with unequal loading and distribution of the body on the supporting surface. This may lead to areas developing peak pressures or invariably a pressure injury — which may in turn lead to sepsis and result in death.

“It is that simple — intervention is essential. In fact, it should be deemed as human-rights issue. Everyone has the right to a healthy and safe life.”

So then, the question becomes how to intervene.

“The comfort and function of the consumer will play a role” in any successful intervention, Hannah said. “Can they tolerate support into a new posture?”

“The seating team has a responsibility to ensure that the consumer is seated as appropriately and comfortably as possible,” said Greg Sims, CEO, Matrix Seating USA. “Intervention ultimately is the choice of the consumer or caregivers, but given the choice of being healthier and not deteriorating, most consumers will choose intervention if they can tolerate the methodologies involved.”

Increasingly, those methodologies include the possibilities of combining what used to be opposite perspectives — accommodating what used to be called a “fixed” posture while also seeking to intervene and shape its future.

The Adjustable Future of Seating

Adjustability has become a key component of today’s seating systems for complex rehab clients — and adjustability can be tremendously valuable for clients with asymmetries.

Asked if it’s possible to both accommodate an asymmetry to a certain extent and intervene to direct its future course, Davin said, “Absolutely! There are some amazing new, innovative product lines that will offer the therapist and/or seating team the opportunity to not only accommodate, but intervene as well. For example, let’s say you have a client who presents with pelvic rotation, which results in a windswept presentation of the bilateral lower extremities, in which one leg is abducted (angled away from the body) and one is adducted (angled towards midline of the body). Anytime you correct an asymmetry, you are successfully preventing the progression of that asymmetry, thus positively impacting the client’s future posture.”

Davin mentioned the extreme adjustability in such products as Adaptive Engineering Lab’s Omnilink, capable of not just stabilizing a client’s trunk and torso, “but you can also ‘follow’ the patient back into a neutral position, should the client improve over time. The key to achieving both intervention and prevention of further asymmetry progression is to have supports which offer unparalleled adjustability, thus offering the seating team or therapist the opportunity to progress or ‘follow’ the client into improved positions as improvement is noted.”

Highly adjustable seating systems, capable of being quickly changed as a client’s needs evolve, are being offered by both Matrix Seating USA and Symmetric Designs.

And Hoffman said that incorporating other equipment beyond seating can also make inroads with asymmetrical postures.

“Again, to determine the role of the seating, a comprehensive assessment is required and an understanding of the ‘critical measures,’” she said. “Critical measures can best be described in the words of Long (2014), to determine the joint ranges of motion and to ‘identify critical limitations in the alignment of the pelvis and trunk.’ The limitations in the joint ranges of motion need to be considered, as they have implications for lying, sitting and standing orientations. If the critical measures are not taken into account, and equipment is provided which is not respectful of the ranges, then the success of the posture management intervention plan will be severely limited, fail or even worse, result in further injury or damage to the individual’s posture, function and quality of life.

“Once the critical measures have been determined, the provision of 24-hour posture management equipment can be implemented, alongside the appropriate training.”

Intervening and positively impacting a client’s asymmetrical posture can be a gradual, long-term process, Hoffman added.

“The critical measures will be the guide to the intervention when addressing asymmetry in sitting. There are a bevy of seating systems that can serve to meet the individual’s postural needs and seating requirements. Alongside, the intervention of positioning in the lying orientation with the support of an informal (pillows, blankets, towels) or formal (manufacturer-produced system or modular component) sleep positioning system can promote symmetry and restore body shape and alignment. This gentle and caring approach in lying is lengthy: Remember, it took several months or even years to establish the postural asymmetry, and it simply won’t take one week of good positioning to restore or resolve the postural asymmetry.”

Seating teams need to be ready to adjust seating systems as postures positively change.

“Seating systems selected need to possess the ability to be changed, amended and adapted to meet the changing postural needs and gains made through 24-hour posture care management,” Hoffman said.

While working with an asymmetry might therefore be seen as a continuous process, Davin made clear that intervention is critical.

“Even a minimal amount of asymmetry can eventually lead to a moderate or severe asymmetrical presentation if no intervention is provided,” she said. “Therefore, in this clinician’s opinion, it is imperative to intervene when any asymmetry is noted.

“There are some exceptions to this rule: For example, often clients who present with a diagnosis of muscular dystrophy will intentionally position themselves in a position of anterior pelvic tilt, to create a ‘tripod’ effect to better stabilize a weak core/trunk. Barring any exceptions, it is important to attempt to neutralize the client, and aid in positioning him or her in as neutral and functional of a position as possible, in order to promote improved activities of daily living performance, function and self-propulsion, if applicable — keeping in mind that a small asymmetry today turns in to a major asymmetry tomorrow with the potential for physiological impact.”


Bower, E. (2009) Finnie’s Handling the Young Child with Cerebral Palsy at Home (Fourth Edition), Butterworth-Heinemann, Edinburgh. ISBN 9780750688109.

Clayton S., Goldsmith L., Ellis T. (2017) 24-hour postural care: The journey so far in the UK. www.simplestuffworks. [accessed May 25, 2017].

Pope P. (2007) Severe and Complex Neurological Disability: Management of the Physical Condition. Butterworth-Heinemann Publishers.

Taktak A., Ganney P., Long D., White P. (2014) Clinical Engineering A Handbook for Clinical & Biomedical Engineers: Long, D., Chapter 19, P 285-308. [accessed May 5, 2017].

This article originally appeared in the September 2017 issue of Mobility Management.

In Support of Upper-Extremity Positioning