Spondylolysis in Children | Pars Interarticularis Fracture

An Overview of Pars Interarticularis Fractures
and Spondylolysis in Children

Anatomy

The pars interarticularis is the bony portion of the vertebra that connects the pedicles to the inferior (lower) facets. In fact, the term “interarticularis” means the area between two articulations (joints). There are two pars interarticularis bony junctions- one on each side. The two lower joints below the pars articulate with (hook onto) the upper joints of the vertebra below.

The purpose of these lower joints is two fold. One is that these joints act like railroad tracks to guide the motion of the vertebrae above on the vertebra below. The second function of these joints is that they act as “doorstops” to prevent the vertebra above from sliding forward on the lower vertebra. The lower two vertebra (L4 and L5) sit on a ski slope pointing downhill and these intact “doorstops” prevent this slide.

In the front of the two vertebrae sits the disc. The disc is an excellent shock absorber or “bushing”. This disc is the main cushion for spinal impact. The disc however has no directional stability. Without the facets in back to protect it, the disc can twist, flex and extend, laterally bend and tilt and shear (slip forward and backwards). It is the intact facets that prevent the spine from bending in certain injurious directions.

When the connections between the facets and the pedicles are severed (pars interarticularis fractures), the disc is unprotected and can undergo motions that can cause damage. The disc is especially sensitive to rotational and shear forces, the forces that cause one vertebra to slide forward, sideways or rotate on the other. The facets prevent these forces on the disc by acting as “doorstops”.

Because the upper vertebra’s lower facets hook onto the lower vertebra’s upper facets, the intact facets restrict the shear forces of the vertebral segments. If the facets wear out (as in the case of a degenerative spondylolisthesis) or break off (as in the case of bilateral pars fractures or isthmic spondylolysis), this protection is lost. If the disc gives way and the vertebra then slips forward on the one below, this problem is called an isthmic spondylolisthesis.

It is estimated that one of every twenty children will develop pars interarticularis fractures. If these fractures occur, they normally occur between the ages of 8 and 15 years. Why are these fractures not more commonly diagnosed in this age group? Many times the child that develops new fractures will not initially complain of significant symptoms or will ignore the pain and not report it to parents, coaches and trainers.

Early Diagnosis and Potential Healing

If the fractures are diagnosed early in childhood, the pediatrician is the physician that normally uncovers the fractures. Many injured children however never become diagnosed. This section deals with what to do if these fractures are diagnosed early when the child still has a chance to heal and the disc has not been injured.

In general, children generally have very good bone fracture healing potential. The pars interarticularis fractures however are the one set of fractures in particular that are resistant to healing. There are three reasons for this. One is that the surface area of these fractures is very small. Bone fractures heal best with large surface areas and the surface area of this fracture is smaller than some of the smallest bones in the hand.

Bone also has better healing potential when large cancellous surface areas are exposed. Cancellous bone is the “spongy bone” inside the hard cortical bone and has many bone generating cells. Unfortunately, the pars interarticularis has almost no cancellous bone.

The third problem is that this area of the spine has some of the greatest motion and shear forces acting on it, This fact is one of the main reasons the bone fractured in the first place. Getting an active child or teenager to rest this area is almost an act of God. A brace can slow a child down but will not immobilize the area and healing bone cells do not respond well to motion.

In the typical bilateral pars fractures, healing without a brace and without reduced activity has a very poor repair rate. Healing with a brace and three to six months of reduced activity has a success rate of about 50%. The chance of re-fracture is not know at this time but children with healed fractures can occasionally re-fracture if they go back to their previous level and type of activity.

(Click to Enlarge Image) Illustration of pars interarticularis.

(Click to Enlarge Image) CT scan of pars fracture of L5. White arrow points to fracture. Thisadolescent had 4 months in brace and continued to have pain upon return to activity.

(Click to Enlarge Image) CT axial scan of L5 pars fracture. White arrows point to fractures of pars interarticularis.

(Click to Enlarge Image) Illustration of Isthmic Spondylolysis. Thin arrowpoints to bone spur compressing the nerve. Medium arrow points to the slipof L5 on the sacrum. Thick arrow points to the non-healed fracturepannus.

(Click to Enlarge Image) Isthmic Spondylolysis. Note the slipof the L5 vertebra on the sacrum. This is the endpoint of degenerativewear resulting initially from an undiagnosed spondylolysis when thepatient was a child.

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(Please keep reading below for more information on this condition.)

Unilateral (One Sided) Pars Interarticularis Fractures

Although it is uncommon for only one side of the pars interarticularis to fracture, unilateral fractures do occur. If a unilateral pars fracture does arise, the opposite pars will be placed under more stress and therefore will hypertrophy (lay down more bone-Wolfe’s Law) to resist the greater forces placed upon it. If the fractured side does not heal, the greater bone mass of the opposite side may allow an individual who has a unilateral pars fracture to live with it comfortably. However, the unilateral break may create enough stress on the opposite side to eventually fracture it also.

The unilateral pars fracture has a much better chance of healing with rest and bracing. Think of the vertebra and both pars interarticularis as a ring. If only one break of the ring occurs, the ring still has some torsional rigidity. If there are two breaks, the ring is broken in half and has no rigidity. A recently diagnosed one-sided (unilateral) break allowed three months of bracing and rest will normally heal.

Healing potential and resolution can be assessed by MRI, X-rays, bone scan and CT scan. There are particular appearances that may indicate an effort by the body to heal the fracture and conversely, a noted lack of healing potential.

The unilateral pars interarticularis fracture needs to be differentiated from a facet fracture. If the fracture line starts at the pars interarticularis but descends obliquely instead of normally traversing across the pars, this fault line can fracture off the entire facet. A facet fracture will not heal. The CT scan is the only useful tool to diagnose this injury.

Non-Healed Fractures and Altered Biomechanics

What is the future of the spine in the adolescent with bilateral pars fractures that do not heal? If both pars are fractured, the biomechanics of the spine changes. There is more stress placed upon the disc and the entire spine can slip forward (isthmic spondylolisthesis– see separate section on this website). This leads to disc tears and degenerative changes of the disc. Some patients develop lower back pain and even leg pain if a pedicular bone spur develops. To prevent degenerative changes from occurring, there is mounting evidence that the pars fractures need to be surgically repaired.

Please see section on surgical pars repair on this website for further information.

For more information on spondylolysis in children, or to discuss treatment options for a pars interarticularis fracture, please contact Dr. Donald Corenman, back doctor and spine specialist in the Vail, Aspen, Denver and Grand Junction, Colorado area.

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81 reviews

Eric S

Sep 26, 2021

by Eric S on Donald Corenman, MD, DC

Successful pars repair at 46 years old

Back in November of 2018 (at 46 years old) I came from Vancouver BC to have a pars repair done with Dr. Donald Corenman at the Steadman Clinic in Vail Colorado. I'm finally posting this review nearly three years later in late 2021. The reason I waited so long was I wanted to know the final result before I posted my review. Unfortunately in that time Dr. Corenman has retired. Nevertheless, I want to post this review of Dr. Corenman and his staff at the Steadman Clinic in their excellent treatment of my L5 pars interarticularis.

I fractured my pars at age 42 back in 2014 when rolling on the gym floor, and was denied treatment by the Canadian healthcare system, probably due to my age. First my GP told me there was no surgical option for a pars defect, which was quite incorrect! I tried to live with it, but the symptoms worsened (periodic random spine slippage and weeks of resultant pain after just bending over to tie my shoe, so I eventually learned to mostly squat and hardly bend). When I finally consulted with Canadian spine surgeons, I was told they believed my pars defect had been congenital (since birth). This was absurd, considering I had done extreme martial arts (including jiu jitsu) for years prior, as well as 5 years of reinforcing steel full time in my 20s, probably the hardest job on the back you can find. No pars defect like mine would possibly have allowed this--ergo it was impossible that I had had the defect since birth. I did however have an asymptomatic congenital spina bifida occulta that made me more susceptible to a pars fracture. In 2014 in one instant, I went from having the strongest back people I knew said they'd ever seen, to being unable to safely bend over and tie my shoe without a non-negligible risk of my spine slipping randomly (which would lead to weeks of pain after each occurrence). This was due to the unilateral L5 pars defect, otherwise known as spondylolysis. It was when lying in pain on the floor 4 years later after maybe the 6th spine slippage event post injury, that I had had enough, and resolved to have surgery. If Canada's "universal health care" said no, I would make lemonade from lemons, and find the very best surgeon in the world at pars repairs. That was Dr. Donald Corenman. Dr. Corenman back in 2018 ran a website https://neckandback.com/ that dedicated many pages to the science of every aspect of pars repairs, from eligibility (good discs on MRI), to best surgical techniques (minimal open compared to minimally invasive), best imaging to use (i.e., O-Arm with Stealth imaging vs. older fluoroscopy), the ideal amount of BMP to use and why not use too much or too little, and much more, all to do with pars repairs, pages upon pages of his site just on the pars, with scientific references and his own extensive expert opinion. As a health research statistician, I was very impressed with this. It was in stark contrast to the websites of other spine surgeons which barely gave the pars a word or two, focusing almost exclusively on fusions. I had found the best surgeon in the world for pars repairs, and so after Dr. Corenman personally screened my MRI to ensure my discs were healthy, I booked the surgery.

Being 46 years old at the time of surgery in 2018, with a 4-year-old pars fracture from 2014 combined with a congenital SBO meant my pars fragment was somewhat atrophied, but it was "very solid", said Dr. Corenman in the operative report. Nevertheless, it was challenging with two things to fix, the pars and SBO, and OR time was around 4 hours. Recovery over the following months was guided by a very clear "Spine binder" from the Steadman Clinic with strict rules of "no BLT" (no bending, lifting or twisting), and illustrated physiotherapy guidelines. They even warned patients to avoid fish oil supplements, which could excessively dampen inflammation and hence slow bone healing. They answered many questions I had during months of recovery, with responses coming from the very supportive Lori Fugate (then director of Dr. Corenman's practice), and Ehrich Bean (then physician's assistant at the practice), as well as a couple calls with Dr. Corenman himself after two of the CT scans. Ehrich Bean offered great advice for taking the spine binder conservatively due to the nature of pars repairs vs. fusions. The final post-op CT scan I had was a couple weeks ago at 34 months post-op, and Dr. Corenman had retired, but I got a very positive and informative call from Eric Strauch (current PA at the Steadman Clinic under Dr. Corenman's replacement there, and who had also worked with Dr. Corenman previously). The staff at the Steadman Clinic were extremely supportive all the way through the process. I should mention, the local Canadian spine surgeon did offer me very good post-operative support including antibiotics as needed to deal with a mild surface incision-site infection early on, booking numerous x-rays when I felt something was amiss, as well as booking all four of my post-op CT scans. I am very grateful for that support also.

My final result shows plenty of solid bone across the pars and a healed SBO, with my vertebral body now a solid bone ring instead of being broken at two places as it was pre-op. Does my spine hold up in the real world? You bet! I have recently dug and moved several yards of dirt and sand and gravel by myself (shovel and wheelbarrow!) to fix our water main, pulled roots from the yard, moved several "portable" (these are HUGE) air conditioners up several flights of stairs my myself, and lifted weights. I now run 2 miles (3.2 KM) several times weekly with a hard 100 meter dash in the middle. I bend deeply before each run I go on, with no spine slippage. My spine feels amazing. I can bend over to do exercise, or real word tasks, with no risk of spine slippage.

My sincere thanks to God, Dr. Donald Corenman, Lori Fugate, Ehrich Bean, Eric Strauch, and the Steadman Clinic, as well as the Canadian spine surgeon who offered me excellent post-operative care back in Canada. You have all given me a new lease on life.

Sincerely,
Eric S

Robert S

May 11, 2021

by Robert S on Donald Corenman, MD, DC

Back Fusion Surgery

I had my entire lumbar spine fused in November of 2018. I had scoliosis , with pinched nerves that were so painful I could hardly walk - and standing for more than a few minutes was impossible. Even sitting was painful.
The fusion surgery produced immediate relief! And the recovery was much easier than I expected.
To this day I can do all the activities I love from hiking, to standing in a stream fly fishing to riding my bike long distances - or just walking down the street with my wife.
Kudos to Dr. Corenman and his staff, (including the two Erics) for taking such good care of me!

Leslie R

Jul 9, 2020

by Leslie R on Donald Corenman, MD, DC

TLIF

I had my TLIF surgery on 6/24/2020 by Dr. Corenman, I can not say enough good things about the Dr or his staff. I was always treated with respect and explained everything throughly, that made it easy for everyone to understand. I highly recommend Dr. Corenman and the Steadman Clinic.

Spondylolysis in Children- Healing Potential and Treatment/ Pars Interarticularis Fractures in the Lumbar Spine in Adolescents

An Overview of Pars Interarticularis Fractures
and Spondylolysis in Children

Anatomy

Early Diagnosis and Potential Healing

Is your child suffering from symptoms of a pars interarticularis fracture?

Unilateral (One Sided) Pars Interarticularis Fractures

Non-Healed Fractures and Altered Biomechanics

Related Content

About the Author: Donald Corenman, MD, DC

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Spondylolysis in Children- Healing Potential and Treatment/ Pars Interarticularis Fractures in the Lumbar Spine in Adolescents

An Overview of Pars Interarticularis Fractures and Spondylolysis in Children

Anatomy

Early Diagnosis and Potential Healing

Is your child suffering from symptoms of a pars interarticularis fracture?

Unilateral (One Sided) Pars Interarticularis Fractures

Non-Healed Fractures and Altered Biomechanics

Related Content

About the Author: Donald Corenman, MD, DC

An Overview of Pars Interarticularis Fractures
and Spondylolysis in Children