New Advances in Lumbar Disc Replacement Lumbar spine disorders continue to cause the vast majority of clinical problems in many patients. Motor unit preservation, such as lumbar disc replacement, has been extensively studied. However, their long-term follow-up results remain unclear, and it is unclear whether they can alter the course of degenerative lumbar spine disease. Lumbar disc replacement Lumbar disc replacement remains a controversial area of treatment for degenerative disc disease of the lumbar spine. Although the theory of the preserved motion unit technique is attractive, studies have not yet yielded convincing data on the long-term follow-up outcomes of patients who have undergone this technique. A recent study investigated follow-up outcomes five to eight years after a single disc replacement. A total of 506 patients were enrolled and followed in this prospective randomized study from 2000 to 2004. 352 of the 506 patients underwent single-segment replacement, 109 underwent double-segment replacement, 40 underwent triple-segment replacement, and the remaining patients underwent more segmental implantation. ODI scores showed significant improvement at three months postoperatively and continued to show improvement at the eight-year postoperative follow-up, and VAS pain intensity scores showed significant improvement at three months postoperatively and continued to show improvement at the eight-year postoperative follow-up time point. Imaging showed good lumbar spine motion at the prosthetic segment throughout the follow-up. Long-term follow-up showed good clinical efficacy of this internal fixation device at five years. A recent multicenter prospective randomized study directly compared two lumbar artificial disc prosthesis devices. The study included 457 patients who were treated with single-segment surgery. At the final (two-year) follow-up time point, there were no significant differences between the two groups in terms of surgical and follow-up metrics or clinical outcomes with the different prosthetic devices. Both groups showed significant improvements in clinical scores compared to the preoperative period and similar success rates. Notably, this study is the first to involve a direct comparison between two lumbar disc prostheses, and both devices achieved similar clinical outcomes. In another report by the same authors, based on data from the same study, a comparison of imaging data between the two groups was performed. A decrease in the level of lumbar segmental range of motion occurred in both groups at three months postoperatively, regardless of whether postoperative mobility was higher or significantly greater than preoperatively. A higher success rate was achieved as long as lumbar segmental motion was >4 degrees. Both devices appeared to maintain range of motion during the study time period. Adjacent segmental disease and progressive degeneration The theoretical advantage of artificial disc replacement is the potential reduction of adjacent segmental degenerative disease leading to revision surgery. In a recent study of patients who developed adjacent segmental disc degeneration after lumbar artificial disc replacement and underwent reoperation, 21 of 1000 patients who underwent lumbar artificial disc replacement required secondary surgical treatment for problems that occurred in the adjacent segment. The mean time to reoperation was 28.3 months postoperatively. Preoperative MRI showed that 38.3% of the adjacent segments were normal, 38.8% had moderate degeneration, and 22.2% had severe degeneration. 15 of the 21 patients underwent preoperative CT, 12 had normal articular surfaces, 7 had I degeneration, 2 had II degeneration, and no patients had III or IV degeneration. The incidence of adjacent segmental disease after artificial disc replacement was similar to that after fusion. Analysis of patients requiring revision surgery showed that many patients had adjacent segment degeneration prior to initial surgery. Therefore, patients with adjacent segment degeneration prior to initial surgery may have a delayed progression of degeneration. Another report examined adjacent segmental disc degeneration and synovial joint degeneration in the operated segment after lumbar artificial disc replacement. The authors reported on 93 patients who underwent single-segment lumbar disc replacement surgery. The mean follow-up time was 53.4 months (24.1-98.7 months). 10.2% of the patients developed adjacent segment disc degeneration; nevertheless, these degenerations were mild, occurring at a mean of 65.2% of the months postoperatively. The incidence of synovial degeneration at the surgical site was approximately 20% (44 cases) of the 220 synovial joints. It occurred more frequently in the lumbosacral joint. These common degenerative manifestations were significantly associated with poor postoperative outcomes and decreased lumbar spine mobility. Thus, degeneration of the synovial joints of the operated segments after artificial disc surgery does exist and affects outcome.