Lumbar Disc Replacement Preserves Motion. What Happens to the Segment Over Time?

Motion preservation has long been one of the primary goals of lumbar total disc replacement (TDR). In contrast to spinal fusion, which intentionally eliminates movement at the treated level to stabilize the spine, TDR is designed to maintain segmental motion while still addressing pain caused by degenerative disc disease. This shift in approach reflects a broader effort to preserve more natural spinal biomechanics but it also introduces an important clinical question.

Does preserving motion today translate into healthier spinal mechanics years later?

Long-term success depends on more than pain relief. Surgeons also want to know whether the implant continues to function as intended, whether motion remains physiologic, and whether adjacent structures including the facet joints and neighboring spinal levels continue to tolerate the altered biomechanics over time.

A long-term study by Pimenta and colleagues explored these questions by evaluating the Physio-L elastomeric lumbar total disc replacement after a minimum follow-up of 84 months. Rather than asking whether patients improved after surgery, the study examined what happened to the operated segment over the next seven years.

What This Study Explored? 

The prospective, single-center study followed 15 patients (20 lumbar disc replacements), including 10 single-level L5–S1 cases and 5 two-level cases. Clinical outcomes were measured using Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) scores, while radiographic evaluation assessed range of motion, implant integrity, facet degeneration, adjacent-level disease, and revision surgery.

Compared with many reports that emphasize short-term symptom improvement, this study focused on a question that becomes increasingly important with time: what happens to a motion-preserving segment years after implantation?

Image Source: https://pubmed.ncbi.nlm.nih.gov/30280083/ 

What Seven Years Have Revealed?

The clinical outcomes remained encouraging throughout follow-up. Mean VAS pain scores improved from 7.1 to 2.9, while ODI improved from 50 to 16, indicating sustained reductions in both pain and disability more than seven years after surgery.

Implant durability was similarly reassuring. The investigators reported no disc migration or breakage, and 89% of prostheses remained active at final follow-up.

Yet the study's most valuable insights came from looking beyond implant survival.

Although the prostheses remained structurally intact, segmental range of motion gradually declined, decreasing from 13.3° at one year to 9.9° at the final evaluation. The operated segment continued to move, but its biomechanics evolved over time rather than remaining static.

The surrounding anatomy also changed. Radiographic facet degeneration developed in 47% of patients, although only one patient became symptomatic. Adjacent-level surgery was required in 13% of patients, and adverse events occurred far more frequently in two-level procedures (60%) than in single-level cases (10%).

These findings suggest that preserving motion does not eliminate the biological and mechanical changes that continue to occur within the lumbar spine. Instead, it changes where clinicians should focus their attention during long-term follow-up.

Looking Beyond Pain Relief

One of the strengths of this study is that it shifts the conversation beyond whether lumbar disc replacement works in the early postoperative period. The more meaningful question is how the operated segment behaves after years of continuous loading.

Pain relief remained durable; implant survivorship was high, and catastrophic mechanical failures such as migration or breakage were not observed. At the same time, the study reminds us that motion preservation should not be viewed as a static endpoint. Changes in segmental motion, facet degeneration, and adjacent-level pathology can still emerge despite an intact implant.

The findings also reinforce the importance of patient selection. Outcomes appeared most favorable in single-level L5–S1 disease, whereas multilevel arthroplasty was associated with substantially higher complication rates. Although the study is limited by its small sample size and noncomparative design, it provides valuable long-term observations that are still relatively uncommon in lumbar arthroplasty literature. 

The Clinical Perspective

Lumbar disc replacement was developed to preserve motion, but preserving motion is not the final objective. The larger goal is to preserve function while maintaining healthy spinal biomechanics over time.

This study suggests that long-term outcomes should be evaluated not only by pain relief and implant survival, but also by how the treated segment continues to function years after surgery. For clinicians, that means monitoring more than the implant itself. Segmental motion, facet health, adjacent levels, and the complexity of multilevel disease all remain important considerations during long-term follow-up.

Reference

Pimenta L, Marchi L, Oliveira L, Nogueira-Neto J, Coutinho E, Amaral R. Elastomeric Lumbar Total Disc Replacement: Clinical and Radiological Results With Minimum 84 Months Follow-Up. Int J Spine Surg 2018;12:49–57. https://doi.org/10.14444/5009.