Biomechanics of pedicle screw and how they fail

Learn about the bio mechanics of the pedicle screw and why they are sub-optimal fixation for spine.

[@jrchicago9216]

Thank you for these well observed details... This is an important discussion... in engineering you may be interested in the Charpy V-Notch Test, it’s about determining the sudden point of failure. In pedicle screws, the more hardened, the more brittle to sheer (typically - unless other materials are introduced which may not be surgically suitable). The screw breakage is primarily at sheer, not bending flexes over the screw length because the screw shaft is primarily held in constant until the very near the area it protrudes. It’s much like an electrical fuse - like a glass fuse we see the wire. The fuse is totally fine but it has a very sudden defined breaking point that is immediate. Once a pedicle screw has exceeded its tolerance, it breaks off. This tells two stories. 1. The human movements are capable of breakage and this makes pedicle screws less attractive for use; 2. The assumptions that a long screw is a great fixation is a failed belief if and when the screw breaks. If you asked the surgeons who have performed thousands of artificial spinal disc implants, they will explain it’s not about fixation, it’s about natural movement the Spine was intended to function in the first place. Many suggest it’s old school and verges on barbaric to fuse operating bones together when mobility options exist. Check out surgeon to surgeon presentation videos at Seattle Science Foundation Dr. John Hsiang and Dr. Michael E. Janssen who have performed many thousands of artificial disc implants. If a patient is an good candidate for an artificial disc implant, there is no medical benefit to spinal fusion. Spinal Fusion leaves the patient far less physically able, causes ASD eventually and is old school. In Europe where the artificial disc implant was invented in Germany in the mid 70’s, they have decades more experience and far better patient outcomes. The US is shamefully not the leader. It’s arrogance and the imbalance of the FDA and big corporate money that has blocked the best implants like the Spinal Kinetics M6 from being a standard in the US. The M6 is the go to implant in Europe for the past decade, as well as the slightly newer ESP. The US is being bombarded with patients who are on the internet and demanding artificial disc implants over fusion. Natural movement will win most people’s desire. Would you really fuse someone’s knee anymore? Time to move towards reality.

[@sabetibrahim860]

You got right into the point instead of blaming patients.

[@raulocasio9168]

Brilliant engineering explanation of TOGGLE: toggle mechanism, a combination of solid, usually metallic links (bars), connected by pin (hinge) joints that are so arranged that a small force applied at one point can create a much larger force at another point. I am a retired Architect that has had a Laminectomy from L3-5 which is causing some uncomfortable quad muscle tightness/pain symptoms. I have received some transforaminal epidural injections at L3-4 with 85% relief. The surgeons have recommended an ALIF and posterior hardware procedures L3 - S1. THANK YOU, THANK YOU!!! I WILL NOT CONSIDER ANY SURGICAL PROCEDURE UNLESS IT IS LIFE-SAVING!!! I will continue to do the injections every 4-6 months and carry on!!!

[@bluewyvern7858]

Thank you so much for making this video. It's a great help to students. We need people such as yourself to challenge pre-existing notions, especially in the medical field.

[@RunningNotStopping]

Patient here: I'm living proof (unfortunately) that this is all very real. You explain good. Thanks Also might be doing xlif next.

[@jdjd2059]

already 6 years since I got my doctor's and spine professor expert, a decision that I should go through L4-L5-S1 fusion. But all these years i was questioning that decision because I could not understand, how metal screws inserted to my weak spine will enforce the whole structure? how is my post surgery damaged back muscles and tissue will supports the spine? I was and still in great doubts about this procedure, now after watching your video, I have no doubts, that i will not take this surgery, even as a last resort, it's doom to fail. THANK YOU for sharing a vital true info, most doctors will not dare to say the truth, they only think about career and money!

[@kickdog6934]

You are 100% right...

[@giuseppeamendolara2367]

discogel and stem cell can help out the disc regeneration. Fusion is a criminal activity.

[@objetividad693]

@@giuseppeamendolara2367 And what to do if you have spondylolisthesis? How do you fix the vertebra without screws, greetings

[@vortex21rainz26]

@@objetividad693 yes that is my question too

[@KiwikimNZ]

Agree I’ve had 2 fusions and I would wait for better surgical developments such as artificial discs. From my two fusions I’ve had adjacent disc herniations due to the extra mechanical forces. The thoracic fusion has collapsed and is now fused, the curve in my spine (kyphosis) which should be between 20-40 degrees is now at 90 degrees and getting worse.

[@gregorydashnaw2522]

Excellent presentation and thank you for the references to additional supporting clinical studies doctor. I am grateful, nevertheless, what other option is there really for a patient who has one or two lumbar vertebra that have now moved out of position towards the spinal cord resulting in a type (grade) two or three outcome? In other words, a position deviation equivalent to type 2 (25% to 50%) or a type 3 (50% to 75%). Additionally, for someone like myself, living in Denmark and thus restricted to the present approved and applied method of spinal rehabilitation, the options are further limited to what currently is available and whatever is considered best practice in the given geographic region one finds ones self residing. If a patient is experiencing chronic numbness and balance instability from the waist down and it is reported that the problem cannot be trained away what other options are there? It can be quit a dilemma you understand. You apparently continue to employ the devices, so there must be some viable logic with implementing the procedure anyway. For myself at least, I may very need to accept the challenge and take the risk because I cannot just remain in a chair and continue to limit my ability to walk more that 50 meters before I get numb. It is a hard call! Thanks again from Denmark..................

[@imveryhungry112]

you should get another fusion maybe ?

[@irmatubi564]

I thought of this recently since my broken 2 screws on S1 (those broke below the head-pressure point)... realisation of the screw mechanics came too late cause i have pain now at my right buttock and fusion had not taken place. They made me wear a lumbar sacro brace belt for now.

[@Latviaitalia]

Jan 2023 Had Spondylolisthesis unstable grade 3/4. Apparently it’s a 2/4 post surgery. Spine crushed into pelvis. Procedure to fix was ALIF one cage, S1/L5 Pedicle screws & rods (4 total). Felt amazing for 6 weeks post op. Suddenly had debilitating pain. MRI shows 2 loosened Pedicle screws on both sides (1/2 is debilitating more than I was prior to surgery). Surgeon keeps stating “bone fused successful”, overseeing L4 is still junked up & screws are failing. I can feel my Rod on the side that hurts the most. It’s ruining my life. I am trying to do all the research I can

[@jojosangrytarots]

I have a pedicle screw loose on L5-S1. Its getting worse with each MRI. It is very painful, however I have other issues going on in there. I have another degenerated disk just above that level. Neurosurgeon ordered a Mylogram. We will see what he can do. I had the surgery and fusion in 2014. I am watching this because of my circumstance. Im hoping something can be done. I have alot of scar tissue and ospheophytes in that area. Very great video. Very informative. Thank you.

[@2K9s]

My L-4&5 are fused and my L-3 is trashed. Surgeon is taking out all the hardware (minus the disc spacers, fusing l3 and eventually taking out that hardware there down the road. I had a “clean-up” of my fusion and L-3 (laminectomy) two year’s ago that helped for awhile but my 5th surgery is going to address the current situation. Hopeful this helps and whatever you have does for you too.

[@barbaraanderson3838]

I have the same issue. My pain is in my SI Joint

[@ritastutler1470]

@@2K9s fusion makes u strong there but weakens the above and below...so now I have more bulging and a tear.

[@2K9s]

@@ritastutler1470 Yes, I had adjacent segment disease so doc did fuse my L3. Now I’m trying to preserve the levels above. Pain management has become a joke in this country but that’s for another day. Hopefully you’re managing. 👍

[@ritastutler1470]

@@2K9s My husband has been disabled for a while , but he is six days out on second knee replacement. I did hair. We live on five acres and I push mow a lot, ride a tractor, garden etc. I may have done too much. I walked four times a day for weeks after my surgery as prescribed by my doctor. I did pretty well at first, but the sixth month I had just as much pain…arthritis. I am sad because soon my husband will be in good shape. I stepped in a hole in July. My husband always says At least you have great knees. I thought I did. I tore something but they found bone on bone in my right knee. I want to hike and walk with my friend…three miles just last year, and camp…but nothing is promised and I will be thrilled if my husband is not in pain. How long are you out from surgery. Do you have pain. I still do a lot, but the cold weather kills me as doe’s barometric pressure changes..it is the early morning spasms that kill me. They last sometimes three hours. Muscle relaxers don’t stop them. I should not complain though…could be way way worse. Hope you do very well. I love people who comment to me. I miss doing hair…had the best people, and I guess I am not used to not talking all day..lol

[@mikeabarringer]

Please do a video on 3 level fusion, bilateral

[@daddyp4912]

I wish this dr would do a video about modic changes. And the Antibiotic treatment. It needs to be hughlited

[@LucasHendrickx]

i always thought that this was the case. i can not rebuild the broken tower when all the bricks are damages. therefor i had my thoughts. thank you to confirm my believes

[@TREEHUGGAH1]

thank you Doctor. thank you very much.

[@josephp8712]

Dr has your opinion on disk replacement changed?

[@DamienMearns]

What happens when the patient gets to 70 years and they have shrunk by 2 inches, but the metal work they had as a teenager has not. "Research" only goes out two years as a standard

[@Liz_678]

Saw a video on this procedure. Didn’t care for the procedure. All those screws in the back bothered me. Now I understand why!

[@jcaleca60]

What do you think of coflex steel implant 🤔

[@barbaraanderson3838]

I have 2 pedicle screws(L5-S1) that are loose

[@briankim75]

What is the rate for ASD?

[@sssrbija]

Very interesting..

[@gendennyamtsoo7551]

Thank you.

[@nolandomurray]

so will my l5 s1 srews hold up ,you got me a little paranoid with this one

[@Veraux]

Same here, Like, I feel it's very polarized I've seen many many videos of success stories even after years post-op but I've also seen many failure videos. I dunno what to think anymore.

[@devinramdihal8149]

is there any reason why doctors dont wnna help patient to recover a fusion on spine like l5 and s1 . but if a patient have a bad dics ,u guys do the surgery to replace the bad dics no question? i seek help with fused lumbar l5 and s1 ?

[@ritastutler1470]

I am in so much pain. I had fusion in 2015. I am getting worse everyday. I have spasms every morning, but now I have pain like my spine is moving in an usual movement.

[@imveryhungry112]

maybe you need to get a new fusion?

[@ritastutler1470]

@@imveryhungry112 I had a new mri..abovevand below disc bad..torn disc, facet disease, severe stenosis..

[@shapourshamss]

In last 2 years i did 3 spine surgery,my 2nd surgery they install 5 screws & after couple months 3 of them become loos,i did the 3rd surgery on last september and they change all the hardware with new screws .....now after i did new MRI again show 2 screws loosing again.Its any doctor out there can tell me what i have to do ? the back pain killing me day by day ....,,,

[@issis666]

Perhaps contact Dr. Gillard for a consultation ... chirogeek.com/ (dumb name for a web site but he seems to know Spines). The Cleveland Clinic also provides consultations eclevelandclinic.org/onlineSecondOpinionProductHome. There are many other reputable health /hospital sites (i.e. Mayo Clinic in Rochester, MN) that will provide second opinions / consultations for a fee.). It sounds like you also need to consult with a lawyer that handles medical malpractice. Hopefully they will represent you on a contingency basis.

[@stevenlee9064]

I like the way you think, but it may be a bit too complex for the average viewer. Keep making the videos

[@batbara2605]

I feel every moment of each screw and rod and I still freeze up my back pain is a 10 am in bed a lot but I do move around refuse to be a pill bottle just to sleep all the time I tell myself no pain no gain and I cry myself too sleep a few hours my husband say I. Cry in my sleep every night

[@ryseuglh]

Good info, a little scary though for someone considering surgery for scoliosis like myself

[@j.w.1419]

I wonder if you did it and how did it turn out?

[@MyGully1]

I am wondering too, I go in next week. It is a revision. I asked seven years ago for my surgeon to take the screws out because I thought that was why I had more pain. He took them out after they were there for two years and broke one of the four in half. Long story short the two vertebrae above that fusion had to be fused, it looks solid, screws etc are intact. (L2/3). However the lower vertebrate (L3/4) is not going well. On CT’s and bone scans you can see bad lipping, and both vertebraes , one going forward and one going toward the back, the disc has disappeared. Next week the plan is to stabilise the two vertebrae and place a plastic disc with bone material inside. I don’t know if I have a chance of it working especially after hearing this lecture because of the condition/quality of the vertebral bone but I am going to give it my best shot. I want to walk and stand properly. 😟

[@hilpei3675]

Thank you for this. Fusion has been recommended for me -- I can't do it -- I know my body and it would be a disaster.

[@Chuck.S.]

Not sure if anyone looks at this thread anymore, but I have been searching for answers for years. I had a Anterior/Posterior 360 deg fusion in August of 2013. I had a revision surgery in 2014 to replace screws that were too long ( went out the other side of my vertebra by 4mm. PLUS the surgeon told me one screw was already loose. I have had pain ( moderate to severe ) for the last few years, but also I have a very pronounced "clunk" when I move certain ways. It's random when it happens, but it is sometimes loud enough for my gf to hear it several feet away. No one seems to have any clue what is causing it. I have been dismissed several times with one Dr. telling me it was just a normal "cracking of a joint. No sir ...it is not. I know my body. They have checked with both an MRI and a CAT scan, but I guess because of the hardware it is difficult to see around the hardware because of "blooming". I realize my issues are complex, but the pedicle screws have always been a question for me since shortly after the initial surgery.

[@zzrgio]

same here Chuck, the clunk is getting worse by the min.

[@zzrgio]

how's it going for you?

[@KiwikimNZ]

Ask to get a PET/CT scan with contrast. I had one after years of pain after my multi level thoracic fusion. It was done to see if if my fusion was fused as I am needing reconstructive surgery, but it showed that my screws were directly into my nerves and into the joints that join the rib the the vertebrae. The hot spots were like a Xmas tree. Now I’m getting the metalware out in the hopes it will reduce the pain. However I’m not sure I’m a candidate for the reconstruction now. It’s really disheartening! Good luck

[@Chuck.S.]

@@KiwikimNZ I have had more CT and MRI's than a normal person should ever have to go through. Luckily and I believe shortly after I initially wrote this, i found a competent surgeon who noticed an issue with stenosis through parts that he felt were causing a lot of the pain. Now it didn't take care of all of it or the odd clunking, but reduced the pain to where I could manage my day to day with meds. Finding the right doctor is critical and, in a lot of cases, several doctors. I have a great group who now treats me. They have all been life savers.

[@ritastutler1470]

I feel like I have movement ..had fusion in 2015 L 4 and 5. I a,so hear a pop. I told my go today I feel like I have a metal box in my box moving.

[@j.w.1419]

I understand perfectly, but what I dont understand is after the fusion why do the screws have to stay in there forever? Me myself need C4/C5 but I cant go thru with it. Ill wait for some disc crazy glue cement to come out. Id rather be walking with a cane than have hardware in my neck...no thanks. Also don't want parts of a cadaver in my body.

[@Chuck.S.]

The muscle tissue and scar tissue grow around the hardware as you heal. Generally, they leave the hardware in so that they don't have to disturb everything again unless there is an issue. Everyone is different, but never be afraid to ask your surgeon or pain management hard questions as to why.

[@imveryhungry112]

did you ever get the acdf? they wan me to do it too but i dont wanna

[@LA-1969]

I had a broken washer within 2 wks and had to go back in.

[@j.w.1419]

Hope you are ok now.

[@LA-1969]

Surgery site is great. I just got back from getting SI Injections and learned I will need fusions. Have been battling this for years. Just more noticeable now that my spine is fixed.

[@imveryhungry112]

why cant they invent better screws or something?

[@batbara2605]

It didn't help me I hurt worse than I did before I had my surgery

[@imveryhungry112]

maybe you need another fusion?

[@vasccer3000]

I hope you dont use pedicular screws anymore