Infant Carriers and Spinal Stress

As we are finally realizing the benefits of “wearing” our infants while we perform our daily activities, we must be careful not to compromise the integrity of our child’s spine through the use of improper carriers.

Spondylolisthesis (specifically, Type II/isthmic) is a condition that can result from excessive stress in the low back, such as a baby’s spine might experience in certain carriers on the market today. It is relatively uncommon, but when aggravated is extremely painful. This article explains which styles of baby carriers promote healthy spine development in an infant and describes the unnecessary stress and resulting spinal condition that can result from using certain carriers.

A healthy adult spine has four curves when viewed from the side, located in the neck (cervical spine), mid-back (thoracic), low back (lumbar) and base of the spine (sacrum). Upon entering the world, a newborn has only two curves in her spine: the mid-back and the base of the spine. These two curves are called the primary or kyphotic curves. They have an apex or “hump” at the back of the body. The curves in the neck and low back develop later and are termed secondary or lordotic curves. The curve in the cervical spine develops as the child begins to lift his head and the neck muscles are strengthened. The curve in the lumbar spine results as the child starts to crawl. The lordotic curves have an apex at the front of the body. These four curves — two primary and two secondary — are extremely important in the spine (both adult and child), for this is how the body handles the stress of gravity. If these curves do not exist, the body’s center of balance is shifted, causing undue stress on the spinal column and spinal cord.

A baby’s spine is placed in a compromising position in many of today’s popular carriers. If the carrier positions the infant upright, with the legs hanging down and the bodyweight supported at the base of the baby’s spine (i.e. at the crotch), it puts undue stress on the spine which can adversely affect the development of the spinal curves and, in some cases, cause spondylolisthesis.

Spondylolisthesis is defined as the forward slipping of a vertebra on the one below it. The degrees of severity are determined using the Meyerding grading scale, with grade 1 being the least amount of slippage and grade 5 being complete slippage off the vertebra below. This condition may have a related stress fracture at the pars interarticularis, a structure at the back of the vertebra that takes most of the stress inflicted on the spine when it is arched backwards. When present, a spondylolisthesis occurs at the fifth lumbar vertebra 90% of the time and at the fourth lumbar vertebra 9% of the time.

Spondylolisthesis is documented in approximately 5% of white males, but is prevalent in native Eskimos (as high as 60% of the population is affected). There has been much discussion on the high percentage of affected Eskimos as to whether it is a genetic predisposition or related to environmental factors (i.e., papoose carriers). Knowing how dynamic and vital the biomechanics of the spine are, I believe that environmental factors are the cause. If the trend continues in the U.S. to carry infants in carriers (or place them in walkers, jumpers, etc.) that place their spines in a weight bearing position before the spine is developmentally ready to do so, I believe we will see an increase in the incidence of spondylolisthesis.

Spondylolisthesis has been referred to as congenital anomalies of the spine, but there is no supporting embryological evidence for this assumption.¹ There are factors that predispose a person to this condition, such as weakness in the posterior structures of the vertebra, failure of muscles and ligaments to absorb forces, anomalies of the lubosacral spine, and activities that place high stress on the posterior structures of the spine. Little is known about spondylolisthesis. More research needs to be done specifically addressing the weight bearing position of some carriers. In the meantime, we can take preventative steps by choosing alternate carriers, both for ourselves and as gifts for others.

What I have found to be the ideal carrier is the sling. There are many variations of the sling, but one should look for the following in any type of carrier:

1. Before an infant can hold her head on her own, the carrier should support the neck. A sling cradles the infant just like your arms would, unlike vertical carriers which can actually allow a whiplash type injury.
2. The carrier should not place the infant’s spine in a weight bearing position too early. (The young baby should be horizontal or inclined, with the spine supported along its length.)
3. When a baby wants to be more upright to see the world around him (usually around age 4 to 5 months), the carrier should allow him to sit cross-legged, so his weight is dissipated through his legs and hips, as opposed to the style that has the legs hanging down, where the young spine has to bear the entire weight.

When considering the purchase of a baby carrier, you can often just ask yourself if you would be comfortable in it. Would you feel like you were in a hammock (a sling), or in a parachute harness, with your legs hanging down? Laying in a hammock is better for all of us.

Other benefits of sling type carriers include easy accessibility to breastfeeding, ability to wear baby facing toward or away from wearer, ability to wear sling on back, front or side.

You may be wondering, “What about backpacks? Are they bad? At what age or stage of development is it okay to carry a child in a backpack? What should you look for when buying one?” Wait until your child can sit alone well before carrying him in a backpack. The seat of the backpack should support the child’s entire bottom — not just between the legs, leaving the legs to dangle. One that has a foot rest is preferred.

The choice of infant carriers is a small thing when compared to all the other concerns that face parents, but it is a decision that can have lifelong effects. By choosing a sling type carrier for your baby, you may be preventing a lifetime of backaches and other spinal stresses.

REFERENCES

1. Hensinger, R. N.; Spondylolysis and Spondylolisthesis in Children and Adolescents; Journal of Bone and Joint Surgery, August 1989 71A: 1098-1107
2. Shahriaae, H.; A Family with Spondylolisthesis; Journal of Bone and Joint Surgery, December 1979 61A: 1256-1258
3. Tower S. S. and Pratt W.; Spondylolysis and Associated Spondylolisthesis in Eskimo and Athabascan Populations; Clinical Orthopedics, January 1990
4. Wiltse, Leon; Fatigue Fracture: The Basic Lesion in Isthmic Spondylolisthesis; Journal of Bone and Joint Surgery, January 1975 57A: 17-22

Note: This article was originally written for The Continuum Concept Letter (now defunct) and has been edited for this website.