@sandpiper49 Perhaps this needs some clarification.

According to several studies that I have found, artificial discs may reduce the risk of adjacent segment disease over spine fusions, but adjacent segment disease also does occur in patients with artificial discs, and it also occurs in patients who have had no spine surgery with multiple levels of pre-existing adjacent discs affected. According to the studies, there are a lot of additional factors that increase the risk of adjacent segment disease, such as spinal misalignment, body mass, cervical hardware plate near a disc than can rub against it, osteoporosis, length of fused levels, instrumented fusions, age, genetic factors, kyphosis, and poor correction of sagital alignment. I would think that habits like posture and activity of the patient can play a role because poor posture will stress discs more than a properly aligned spine with good core strength.

Consider this.
"2019 Position Statement from the International Society for the Advancement of Spine Surgery on Cervical and Lumbar Disc Replacements"
https://isass.org/2019-position-statement-from-the-international-society-for-the-advancement-of-spine-surgery-on-cervical-and-lumbar-disc-replacements/
The literature from the International Spine Society reads:
"Possible complications with cervical disc arthroplasty include heterotopic ossification, subsidence/migration, device wear and tear, and adjacent segment disease."

"Currently, there is compelling level I and II evidence with long-term follow-up which supports the use of TDR as a viable alternative to fusion procedures for appropriately selected patients. Those with exclusions per FDA labelling (e.g. > Grade I spondylolisthesis, instability, osteoporosis, etc) should not be considered for arthroplasty."

You also mentioned severe osteoporosis which brings a question to my mind because bone quality is very important when hardware is secured and held by screws, and failure can happen causing migration of a device. My elderly mom who has severe osteoporosis has had a spontaneous spinal compression fracture that added an abnormal curve to her spine when it healed.

Here are a couple other links to literature that may be of interest.

"Long-Term Residual-Mobility and Adjacent Segment Disease After Total Lumbar Disc Replacement"
https://journals.sagepub.com/doi/10.1177/2192568220935813
"Adjacent Segment Disease Perspective and Review of the Literature"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3963057/
"Adjacent Segment Disease
Current Evidence and the Role of Motion Preservation Technologies"
https://journals.lww.com/isoj/Fulltext/2023/06010/Adjacent_Segment_Disease__Current_Evidence_and_the.2.aspx
Of course every patient is different with different health considerations and risks, so the choice of what spine surgery is best for a patient has to be carefully considered by the surgeon. There isn't a one solution that fits every patient. I am a cervical one level fusion patient. I have no hardware, only a bone graft. Not having hardware allows my bones to retain their natural flexing ability that would have been lost if rigid metal had been attached. I also get to avoid any possible immune responses to foreign materials in my body. I am at the 7 year post operative mark with no further complications at this time, and according to one the studies I cited, 7 years is when aging should start affecting the spine after a fusion.

I can say that I maintain core strength, and spinal alignment, and having worked extensively with a physical therapist, I can address any muscle spams that can change spine alignment right away. I learned a lot of this from my PT, and the success of my spine surgery can also be attributed to myofascial release therapy that was done during several years before my spine surgery, and after it to maintain the suppleness of muscle and connective tissue. Tightness, and scar tissue tightness from surgery does play a big role in restricting movement and adding pressure to the body. If you keep that in check, you can move better and function better, and keep these extra forces from affecting the spine. I believe that this reduce my risks of further spine degeneration due to pressure on discs. My fused level is C5/C6 which doesn't do much at all in my ability to turn my head. I just lost a little bit of being able to bend forward to touch my chin to my chest. It is very close. My head turning range is the same as before surgery. C1 through C4 do more of the turning neck movements with C1 and C2 doing most of head turning because they are constructed specifically for that purpose.