Many people would be surprised to consider that just a few decades ago, the traditional treatment for an arthritic knee joint, or arthritic hip joint, was to fuse the joint and lock it in place to prevent movement and hopefully stop the pain coming from bone on bone friction. So people would be fairly immobile with fused knee and hip joints, greatly limiting their ability to walk. Forget about running or any other similar sports activity.

Today is a much different story thanks to artificial knee joints and artificial hip joints. According to a Mayo Clinic study, an estimated 4.7 million Americans have undergone total knee arthroplasty (TKA) and 2.5 million have undergone total hip arthroplasty (THA) and are currently living with these artificial joints. Many are able to enjoy sports activities and mobility in their senior years. According to the Mayo Clinic study, of those people in their 80s, about 6 percent have artificial joints in their body.

This new artificial joint technology enabled much of the American population to stay mobile despite the natural impact of arthritis and joint problems.

Surprising also to consider that spinal fusion — where two vertebrae are locked motionless together — even as of 2020 is still the standard treatment for spine problems caused by herniated discs.

Sadly artificial disc replacement has trailed hip replacement and knee replacement for decades. Part of the issue is the knee and hip joints are more easily accessible than having to work around internal organs to reach the front of the spine to install an artificial disc. Secondly, if there is a problem with the disc, or if it wears out and needs to be replaced, revision surgery for an artificial disc is far more complex than revising a hip or knee joint — especially when the patient is over age 70 when the disc wears out.

This explains why orthopedic surgeons try to delay knee replacement and hip replacement surgery until the patient is in their 50s or 60s and the pain is unbearable. The surgeon hopes the artificial knee or hip joint will last 15 to 20 years — perhaps long enough to outlive the patient. This also underscores why an orthopedic surgeon will mandate that a joint replacement patient lose weight before surgery as the extra weight on an artificial knee or hip will wear it out early, perhaps in as few as 10 years if the person is obese or morbidly obese. With half of the U.S. population classified as “overweight” and 25% of Americans classified as obese, this is a huge factor in estimating the life of an artificial joint.

Understanding spinal fusion

Many people are surprised to learn that in spine surgery for a herniated disc, the disc is not actually repaired during surgery. Instead, in most cases, the herniated disc is actually removed from between the vertebrae, and a piece of bone is installed in its place, along with a plate and screws, permanently locking the vertebrae together. The reason that the disc is typically removed, is that once the wall of the disc has ruptured, more of the soft nucleus will continue to escape in the future, impinging upon a nerve root and requiring a another spine surgery.

During your Internet search on spine surgery, you may learn that spinal fusion procedure is a common treatment for herniations in the low back, simply because artificial discs for the low back are still evolving and improving.

In the neck, however, there have been many advances over the past five year, along with corresponding research that is now favoring the benefits of artificial disc surgery for the neck.

Concerns about the early cervical artificial discs caused many surgeons to be cautious. Similarly, health insurance companies are typically skeptical of any new technology. That is changing quickly as more research documents that artificial disc can provide great advantages over spinal fusion.

This is especially the case in the neck where there are only 6 spinal discs (with the vertebrae labeled C-1 to C-7), compared to 17 below that in the thoracic and lumbar spine. The thoracic vertebra are labeled with a T and the lumbar vertebrae are labeled with an L.

A herniated disc in the neck, if fused, can put more stress on the remaining 5 discs and potentially causing herniations at the other levels. If 2 of the 6 disc levels are fused, the person would have little ability to rotate their neck.

Consequently, there has been great effort by artificial disc companies to get their disc approved by the FDA for 2 levels. This enables the spine surgeon to maintain nearly the same natural rotation of the normal healthy disc in the neck.

If your spine surgeon determines your herniation does qualify for an artificial disc, you may be able to retain the natural rotation in your neck which would lessen the stress placed other discs in your neck, and lowering the risk of a second herniation and another spine surgery later on.

As to evaluating the pros and cons, another factor is your age at the time of your surgery. For the person in their 50s or 60s, chances are good that the disc may last a lifetime. For the younger person with a herniated disc, such is in their 20s, 30s or 40s, revision surgery may be an issue at some point if the artificial disc wears out.

CONTRIBUTING AUTHOR

Sanjay Jatana, M.D.
Board-certified Spine Surgeon
Fellowship-trained spine surgeon
Specializing in Cervical Spine Care

As a fellowship trained spine surgeon, Dr. Sanjay Jatana specializes in treatment of complex disorders of the cervical spine. He is recognized as one of the top doctors in the specialty of cervical spine surgery. Dr. Jatana has special training in the cervical spine and treats patients who require repeat or revision surgery.