Booster arms as "artificial hips"

bearwithmoi

New member
Hi,

I'm an avid reader of car-seat.org and an infrequent poster. Many people have referred to the arms of boosters as acting as "artificial hips.". I currently have my 6.5 y/o 50" - 51 lb. dd on the built-in booster in the center of my Volvo XC90. Because it's intergrated in the seat, it has no arms. Is this okay? Am I short changing my daughter's safety by not having a booster with arms (though none will really fit in the middle next to my other dd's RF marathon).

Thank you,

Sarah
 
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wendytthomas

Admin - CPST Instructor
Staff member
I don't know how well the Volvo seats work. I'm guessing well, since they're Volvo, but I couldn't tell you how. The armrests (or belt guides, in the case of the BubbleBum, Oto, old Parkway, and other armrest-less boosters) hold down the lap belt. I can only guess that the Volvo booster has incorporated this somehow, maybe into the belt geometry or something? I'm not sure. I believe those seats are required to pass the same testing as carseats, but again, I'm not sure.

My biggest issue with built in seats has little to do with built in seats. It's what do you do if your Volvo breaks down, or your 6.5 year old needs a ride with someone else? And if you have a dedicated booster for those purposes, where do you store it that's safe and easy (ie, in the car) so why not use it? Not so much the seat itself. Just the practicality in my lifestyle.

Wendy
 

bearwithmoi

New member
Don't worry Wendy - I always have an extra NBB buckled in the other seat in the back row and usual one on the trunk too. I really appreciate the concern though - I've seen way too many kids recently not in booster seats because it's not "convenient."
 

Jenny

New member
This is something I ponder alot as well. I have read in some of volvo's literature that the best type of booster is one with "hooks" -- aka arms. However I know that volvo also goes overkill oncrash testing their vehicles, which is a good thing so I have faith in their built in. However if volvo had their way, they would offer the volvo-branded britax kidfix as they worked with them and crash tested it for a volvo. So the fact that volvo created a hbb with britax tells me that hbb is the best in their opinion.

That said, My kids take turns riding in the middle booster (taking turns = fighting until someone wins). I just told them this morning that come winter, we live in snowy rural NE, NO ONE is sitting in that booster.

The belt fit on both of them in the built in is very good -- they are 6 and 7 and mid-40 lbs. Ive also removed the middle console therefore they have plenty of room for forward excursion in the event of the unthinkable.

I think there is something to be said for some crashforces being absorbed by the booster sides itself. I am considering buying the volvo booster cushion from the dealer and seeing if that fits in the middle so I havea "safer" (perception not facts) middle option. I too also keep an extra booster buckled in the third row.

The other thing I find fascinating is that my 48", 46 lb 7 year old just about 5 steps in the 3rd row. Have you noticed that?
 

Brigala

Well-known member
For what it's worth, car-seat.org and other similar forums (often with the same techs) are the only place I've heard of "artificial hips."

It's not in my CPST curriculum that I can find (if it is and I've missed it, can someone post the page #?). The Bubble Bum passes the same tests, and doesn't have any "artificial hips" on it. Likewise for the Ride Safer Travel Vest.

I am not fully convinced that it's more than theory. That doesn't mean it isn't correct, just that it may not be proven. The way I see it, belt guides are belt guides and the point is to make the seat belt fit. If it happens to also absorb some of the crash test forces, that's just bonus.

I trust Volvo to make sure their integrated seats are safe, far above any other vehicle manufacturer. My biggest accident was in a 1975 Volvo and it's a miracle of Volvo engineering that nobody died in that wreck. In fact, there's a good chance I would have been more or less uninjured if the back bench seat I was sitting on hadn't been improperly replaced (it wasn't bolted down like it was supposed to be). I would not hesitate to use an integrated booster in a Volvo although I might be wary of it in a Ford.
 

Brigala

Well-known member
For the purpose of belt positioning, yes. But I'm not sure I can see how clips attached to a non-rigid surface (as is the case for both the BB and the RSTV) would really absorb crash forces. Maybe I'm not understanding what is meant by "artificial hips." To me that implies that it provides structural integrity to make up for the child's lack of skeletal strength.
 

LISmama810

Admin - CPS Technician
SafetyBeltSafe's technical encyclopedia also says nothing about a booster serving as artificial hips for energy-absorbing purposes.

I'm also not sure I buy that theory. Unless the belt guides sit forward or exactly in alignment with the kid's actual hips, wouldn't the child's body take the brunt of the crash forces before the booster does? And if it's a seat that's LATCHed in, the child's body will move forward farther than the seat would.
 

wendytthomas

Admin - CPST Instructor
Staff member
Here's how I see it. The belt guides or armrests hold the lap belt down, which keeps the belt on the hips, not the soft part of the abdomen. And so when the forces hip, the booster is taking some of that. It'd be impossible for the booster to hold the belt down without taking *some* of the force. Do I know the percentage? No. Do I think it's more than 50%? Hadn't thought about it. Likely not. But it simply must take some of the forces.

I don't know how boosters without armrests/belt guides work. If they were ok, the phone books of the world would have a purpose.

Wendy
 

Jenny

New member
This theory of ‘artificial hips’ is supported by Kiddy, in the creation of their KSA – Kiddy Shock Absorber.

http://www.kiddy.de/en/kiddy-innovation/safety/kiddy-shock-absorber-ksa.html


The crash test illustration:

http://www.kiddy.de/en/kiddy-innovation/safety/crash-tests.html

However as Wendy and others have pointed out, there is no evidence in the literature to support this. It certainly makes sense in theory though.

However, another feature of Volvo seatbelts have been proven as an advantage:

Their use of pretensioning force load limiter on all safety belts in the second row.

Several studies of boostered occupants (Bostrom, Forman, Kent and Lopez-Valdez, 2010, Smith et al, 2005, Michaelson, et al 2008, Fourman et al, 2008)) found that these types of seat belts reduced the loading of the head, neck and chest,thereby reducing cervical spine, thoracic and head injuries as well over traditional seat belts.

Hopefully this will help you make your decision about the middle booster.

Would love for Kiddy to publish their actual #s on the KSA vs non KSA crash tests! Jenny
 

murphydog77

Admin - CPST Instructor
Staff member
They're artificial hips in that they help position the lap belt, like mature hip bones do. They obviously don't have to be there to accept crash forces, but by the design of some boosters, they are. The belt guides on the Bubble Bum and Oto, for instance, are probably there more to keep the booster under the child in a crash. Otherwise why not simply use a phone book (do those exist anymore?)?

The most important role a booster serves is to raise the child high enough so that the vehicle seatbelt is positioned correctly. As long as the lap belt is touching the thighs and the shoulder belt is across the middle (or closer to the neck) of the shoulder, it's a good fit regardless of whether or not it has armrests.
 

bearwithmoi

New member
Thank you all for your thoughtful and informative responses. I feel a lot better keeping her in the integrated booster now.

Now I just have to get my CPST certification

Thank you!

Sarah
 

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