The Recline of Civilization

The Physics, the Indications & How Recline Can Work with (While Differing from) Tilt

• By Laurie Watanabe
• Aug 01, 2010

The prevalent use of tilt today among complex rehab clients makes it easy to forget that for all its impressive evolution — Center of gravity tilt! Cable-free tilt! Easy-to-use tilt! — it’s still a relatively new positioning option. It’s similarly easy to overlook that before tilt became so ubiquitous, there was recline.

And recline is still here, not just as half of “tilt and recline,” but also as a distinct positioning option with its own physics, its own benefits and the ability to help some clients achieve what tilt alone cannot.

The Physics of Recline

Mechanically, recline operates quite differently from tilt.

“Recline systems provide a change in position by allowing the back to pivot rearward without any change in the position of the seat,” says Mike Babinec, OTR/L, ABDA, ATP, product manager of power chair electronics at Invacare Corp. “Tilt-in-space systems operate with a completely different geometry, as the entire seating system pivots back on the system base without change in the seat-to-back or knee angles.”

Says Jay Doherty, OTR, ATP, clinical education manager for Pride Mobility Products Corp., “The angle of the backrest opens slowly when you’re using recline, and it actually lies the person down into a supine position. The big difference between tilt and recline is that recline takes the pressure under the buttocks and spreads it over the entire body. Tilt takes the pressure from the buttocks and moves it onto the back of the person.”

As with tilt, recline works to redistribute body weight — and pressure — over a larger surface area of the body. Recline therefore is commonly used as a way to accomplish pressure relief by changing a client’s position. But that moving of the backrest can cause another type of pressure concern: shear.

The Problem with Shear

Shear forces, Babinec explains, “are those parallel or tangential between the user and the seating surface, or those between the bony prominences and soft tissues beneath the skin. Shear forces play a very significant role in the development of pressure sores, and also are culprits for causing an individual to slide out of seating systems, away from support surfaces — and driver controls — during a recline cycle.”

As a simple illustration of shear, Greg Peek, a complex rehab industry veteran currently heading Dégagé (aka, American Track Roadsters), suggests putting “your two hands together like you’re in Sunday school. Then rotate your hands to the left or the right; try to do it without moving your wrists. You’re going to see that one hand slides against the other. So that’s what goes on with the back and the back seat surface in a recline.”

Shear is a special concern for users of recline systems because of how a wheelchair back moves during the reclining process.

“For decades,” says Stephanie Tanguay, OTR, ATP, clinical education specialist for Motion Concepts, “manual and power reclining chairs utilized a pivoting point from which the back canes moved to open (recline) and close (sit upright) and which was level with the seat rail of the chair. The shearing effect of the back support moving against the seated person’s skin was related to this lower pivot point.”

The effects became more severe, Tanguay says, as seat cushions were added to the wheelchairs, thus raising the consumer’s body (and their hip joint, i.e., their “pivot point”) further away from the pivot point of the reclining wheelchair. “In this scenario, shear moves against the seated consumer’s back and sacrum as they recline. There is also a shearing force of movement against the seat surface; opening and closing the reclining low pivot back supports often displaced the consumer’s pelvis posterior with recline and anterior when the back angle was closed.”

By the mid ‘80s, Tanguay adds, “several power seating manufacturers were aware of the negative effects of shear and were implementing design changes in their power recline systems to reduce or eliminate the occurrence of shear. The incorporation of a raised pivot point for the back canes helps to reduce the amount of shear or displacement of the back support surface against the seated consumer by bringing it closer to the body’s pivot point. The sliding back mechanism and the power sliding back were also designed to reduce shear.”

“The object,” Peek says, “is to keep the person’s skin in intimate contact with the back upholstery during that recline. Most of the shear takes place in the first 20 to 30 degrees of recline, because that’s when the greatest change takes place.”

Indications & Contraindications for Recline

As a means of positioning and repositioning, recline can be beneficial in a number of situations.

“There are people out there who become very anxious when they tilt,” Doherty says. “I don’t know if it’s a gravitational insecurity or what the case might be, but they physically become anxious over that tilted position. However, they can lie down in the bed fine. Typically, you can get them to use recline. So for these folks, it’s really important that recline be available because that’s a way for them to distribute the pressure, to decrease the pressure under their buttocks to get the pressure relief that they need.”

He adds, “It’s also very beneficial for folks who catheterize themselves in their chair or have to have somebody else cath them while they’re in the chair.” Clients with orthostatic hypotension — low blood pressure upon standing up or moving into an upright position — might also find recline beneficial. “These individuals, when they start out in the morning, might need to transfer into the chair and start out fl at, and then bring themselves up slowly so their bodies can accommodate for their change in blood pressure,” Doherty says.

Babinec says the list of benefits from recline “is a long one,” and besides pressure relief includes passive range of motion of the hip joints (and knees, if elevating legrests [ELRs] are also used); decreased fatigue and increased sitting tolerance; lower-extremity edema management, particularly if recline is used in combination with ELRs; better positioning for respiratory care; muscle tone management; increased blood flow to lower extremities, reducing incidents of venous stasis and concomitant vascular problems; more convenient and safer positioning for supine transfers; gravity-assisted, caregiver-provided repositioning; independent weight shifting; reduced respiratory difficulty through decreasing pressure on the diaphragm and increasing trunk extension; improved line of sight and head control; improved postural/proximal stability and accompanying improvement in upper-extremity function; and reduced hip pain with increased comfort.

But there are also some contraindications to consider when assessing a client for recline.

“It is absolutely necessary to make sure that the consumer has the range of motion in their lower extremities and can tolerate elevation,” Tanguay says. “It might sound overly basic, but I have seen this mistake made several times. Joint range of motion and muscle length must be adequate. Likewise, the consumer’s hip range of motion must be adequate to move through the range of recline. In some instances where the consumer’s hiprange is limited but recline is prescribed, it would be necessary to use or set limits to the recline angles compatible with their range of motion. It is not uncommon for combination tilt-and-recline systems to be prescribed to maximize the potential for small incremental adjustments, even in instances where the consumer cannot utilize the full range of recline.”

As an example of when recline might need to be adjusted per a specific client’s needs, Tanguay cites a former spinal cord injury patient from years ago whose chairs always included power recline. “Within a couple of years — and it’s something that’s highly prevalent in people with spinal cord injuries — he developed a condition called heterotopic ossification. It’s basically abnormal growth or calcification that grows into the muscles and the joints, usually the large joints.” Hips, she says, are especially susceptible, though the ossification can also occur in knees, shoulders and elbows.

Tanguay’s client developed bony growth that limited his ability to sit with his wheelchair’s back angle closed, i.e., upright. “He still had a power recline that tried to close his back angle,” Tanguay says. “This was back in the day before you could limit range of motion or the throw of the back angle. So for him, he could recline back, and as he closed the back angle to sit upright, that power recline would go up to the point where his limitation was, and because he wasn’t really aware of that, it would scoot his whole pelvis anterior on the cushion. Because it wouldn’t close his joint anymore.” The result of being pushed forward: shear of his skin against the seat surface, which would periodically result in pressure sores.

“Over the years, as the technology improved, he ended up with a power recline system where you could limit the degrees of throw on the recline,” Tanguay says, explaining that the system would be programmed to stop at a certain point. “That way we could set it to stop at the limitation of the bony prominence, so we’d eliminate that displacement when the back would try to close the body more than the joint would actually allow. Sometimes, you have to really look at that. Different diagnoses are going to pose different issues.”

“For someone who has a molded seating system, recline is not generally advisable,” Doherty says. “As you recline, the contact with the mold does change. So it no longer matches the individual’s body shape because you’re changing the position it’s being used in. Also, for somebody who has extensor tone, going into recline can initiate that tone and cause problems with the seated position.” And for clients with a history of pressure ulcers caused by shear, Doherty says, “Because the recline mechanism can cause a certain amount of shear to occur, it may not be a very good system for those individuals in some cases.”

Babinec notes that users “who slide forward out of the seat during a recline cycle may also slide away from the headrest, driver controls or powered seating switches.”

Recline with Tilt: The Best of Both Worlds?

Today, recline is often used in conjunction with tilt, and for good reason.

“Tilt and recline systems definitely have some common benefits, but also their own unique sets of strengths and liabilities,” Babinec says. “The challenge is to make or recommend choices that match the strengths of a system to a user’s needs while negating the liabilities. Combination systems offer both tilt and recline. Generally, they provide the benefits of each, while minimizing the liabilities.”

He notes that while tilt and recline can be used together, many clients use each option to accomplish separate goals, for instance “tilt for pressure relief, recline for respiratory care or bladder management, or perhaps recline to address pain management issues through providing range of motion at the hips. There is significant documentation to support that the most effective system for many users to manage pressure is a combination tilt-and-recline system.”

Used together, tilt and recline can provide more complete pressure relief for many clients, Doherty says. “When you tilt back about 25 degrees and then you recline, you pretty much reduce shear from the picture because now gravity’s holding you back in the system as you open up the recline angle. You can tilt all the way back and then open the recline angle, and you’re mostly bearing weight over your back at that point. You’re reducing it almost entirely from your buttocks.”

Adding ELRs, he says, can also be helpful: “Also for edema management, with tilt and recline together — you tilt back and then you elevate the legs and open up the backrest a little bit. Now you really have the legs in a position where the feet are higher than the knees, and the legs are higher than the heart, which is the optimum position for reducing edema.”

When including ELRs with recline, Doherty notes, “Typically you’re dealing with articulating elevating legrests or an articulating elevating foot platform. As you open the back angle, the seat depth does become longer because you’re (opening) that angle. So you need to bring the legs up in order for it to be mechanically advantageous to the person. The articulating elevating legrests or foot platform are a really good match for the reclining seating system because the articulating feature is necessary to compensate for the difference between the knee pivot point and the legrest pivot point. As the elevating legrests come up, if you don’t compensate for that, the knees actually end up flexed, and you end up with more weight on the buttocks as well as the feet, which is what we want to avoid. So an articulating elevating legrest or the articulating elevating foot platform is necessary because as it comes up, it lengthens so it compensates for that. You can keep the legs in a straighter position, and you get better weight-bearing through those surfaces. You want to take the weight from the butt and spread it over the back and the legs. You want to optimize that weight distribution.”

Venerable Technology, Fresh Solutions

While tilt is more commonly discussed in seating & mobility circles today — and some payors would rather pay only for tilt, as well — recline continues to offer substantial benefits to complex rehab clients and can also offer significant help when used in tandem with tilt.

As an example, Tanguay mentions consumers with muscular dystrophy. “Those tend to be consumers where we want them to have tilt and recline because they spend a lot of time making small, incremental adjustments. It’s really about comfort, and a couple of degrees of recline either way is like a mile for some of them. That’s a population that tends to make multiple changes in power positioning, even over the course of an hour. It’s change, change, change, tweak, tweak, tweak. Not full ranges of tilt or recline, but little tweaks: close, open, open, close, tilt, back upright.

“That’s a population that usually has sensation, and they have a lot of discomfort issues. It’s just a couple of degrees between comfortable and uncomfortable.”

This article originally appeared in the August 2010 issue of Mobility Management.