Diagnostic vs Therapeutic Injections

There is a significant difference between diagnostic and therapeutic injections. These injections occasionally can be one and the same but generally, there is a difference.

Most non-diagnostic interventionalist’s goals are to try to give patients pain relief. These physicians are not there to accurately diagnose the exact cause of the pain as that is not their assigned task. They are not surgeons, they are pain relievers. These doctors use therapeutic injections in which a large volume of anesthetic and steroid is utilized to cover as many levels (or pain generators) as possible. Comfort of the patient is also important so IV sedation is used liberally to keep the patient at ease. These sedation medications of course take time to wear off so accurate thought is lost during the “golden diagnostic window” (the first three hours after the injection).

Injectionists who focus on diagnosis have to think differently. Diagnostic injections rely on only one structure to be anesthetized per injection. Obviously if two or three structures are numbed, there would be no way of ascertaining which structure could be the pain generator (assuming there is only one). Using a small volume of anesthetic agent on a specific structure is a very good way to determine if this structure is causing pain. If only a portion of pain is relieved with this one injection, then the deduction is that this structure is causing only this portion of the pain and other structures yet to be tested could be causing the other component(s) of pain. Further injections can then identify other pain structures to complete the picture.

Diagnostic injections depend upon an awake, minimally or non-sedated patient to accurately assess the pain levels after the injection. Essentially, the nerve, disc, facet, pars or canal is “numbed” with an anesthetic (Lidocaine, Marcaine or Novocain) and the patient has to evaluate if this numbed structure yields relief of the original pain. If the patient is too sedated, the patient will not be able to accurately measure the amount of pain relief (using a 0-10 visual analog scale) for the first three hours (the critical diagnostic window used to determine pain relief).

The diagnostic window is the period of time that the anesthetic agent is effective. This is similar to the injection a dentist gives you to numb your jaw. The total time your jaw is numb (about 2-3 hours) is generally about the same time this spinal injection will work to numb the area injected, be it a nerve, disc, spinal canal or facet. If the patient is too sedated during this period of time, the diagnostic window will be lost and with that, any information.

Pain medication also has to be limited prior to the injection. While some of these medications last only a short time (Fentanyl), some medications can last over 4 hours and will throw off the results of this test as pain relief from the narcotic can be misinterpreted as pain relief from the block. Patients should not take their regular or extra dose of pain medication prior to the injection.

Some patients have very active degradation enzymes and numbing agents do not work effectively on these individuals. This means that a diagnostic injection will not generally work. The best screening question is whether a dentist office injection is effective or if the dentist has to inject multiple times to gain some anesthesia effect. If multiple injections are the case, a high concentration anesthetic injection (2-4%) might work diagnostically but will cause a motor block of the nerve. This means that the patient will not be able to use that myotome (muscles connected to that nerve root) for 8-12 hours. This can be effective for the lumbar spine as patients can deal with a partially weak leg but should never be used in the cervical spine due to potential block of the spinal cord and temporary respiratory depression.

The patient has to aggravate the pain prior to the injection. If the pain level is a “2”prior to the injection and drops to a “1”, this yields little information. However, if the pain prior to injection is a “7” and drops to a “2”, this is quite valuable and demonstrates a direct correlation between the injected area and the pain relief.

In addition, some patients have to perform an activity to produce the pain (walk or lift for example). If the patient is too sedated, they will not be able to perform the activity necessary to aggravate pain after the injection (during this 2-3 hour diagnostic window) and the diagnostic portion of this injection will be lost. A good example is a patient with spinal stenosis who only aggravates pain with standing and walking. If they lie on the post-op gurney for an hour after the injection and then are driven home for another hour, the diagnostic window will close and this patient will have no idea if they gained relief for the first two hours.

One common misconception that many interventionists make is to assess the patient days after an injection. This is the period when the steroid (also injected at the same time as the anesthetic) becomes active. Steroids take between 24-36 hours before they become active. The steroid will distribute throughout the body and reduce irritation wherever inflammation is active. Feeling better outside the period of the three hour diagnostic window is not helpful to understand the pain generators. I could inject steroid into a knee and in three days, the back will feel better.

A pain diary needs to be filled out immediately in real time to make sure the results are memorialized. Memory is not always accurate. Having a patient fill the diary out in the office days to weeks later can be erroneous and can lead to false findings and conclusions.

Donald Corenman, MD, DC

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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.

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Diagnostic vs Therapeutic Injections

About the Author: Donald Corenman, MD, DC