Interspinous process device coflex treats degenerative lumbar spinal stenosis: Research progress and finite element analysis

BACKGROUND: Traditional lumbar fusion and internal fixation technology brings various postoperative complications; therefore, non-fusion technology is increasingly used in clinical practice. Interspinous process device Coflex has unique biomechanical advantage compared with conventional lumbar fusion and internal fixation technology. With the continuous improvement of Coflex prosthesis, it will have a bright prospect in the future. OBJECTIVE: To review the clinical effect, biomechanics, finite element analysis, complications and latest advances of Coflex in the treatment of lumbar spinal stenosis. METHODS: CNKI, WanFang, Sinomed, PubMed, SpringerLink, SCIE, CSCI and IEEE Xplore Digital Library databases between 2005 and 2018 were retrieved using the keywords of “lumbar spine, biomechanics, lumbar spinal stenosis, Coflex, finite element analysis” in Chinese and English, respectively. The studies on clinical investigation, biomechanical analysis and finite element analysis of Coflex in the treatment of degenerative lumbar spinal stenosis were included, and repeated studies were excluded. Finally 34 eligible articles were selected for review by reading the abstract, including 9 Chinese and 25 English articles. RESULTS AND CONCLUSION: (1) The effect of Coflex interspinous dynamic device is similar to the same type of interspinous device. Coflex has certain advantages compared with traditional lumbar fusion and internal fixation technology, which has little trauma, short time, rapid recovery, preserves the activity of the surgical segments and can delay the degeneration of adjacent segments and reduces the occurrence of vertebral disease to some extent. (2) In terms of biomechanics, Coflex can retain the activity of the responsible segments, reduce the load on the disc and the facet of the responsible segments, indirectly increase the height of the intervertebral foramen, and alleviate the clinical symptoms. (3) Stress nephogram of three-dimensional finite element analysis shows that Coflex has a significant load-bearing effect on the discs and facets of the responsible segments, and can reduce the intervertebral disc and small joint stress of adjacent segments. Finite element analysis can simulate different in vivo mechanical environments, analyze the changes of mechanical distribution in different research objects, activities and load-bearing units before and after Coflex placement. It is a reproducible and effective method, but the finite element analysis only simulates local mechanics. Its scope is limited, and it is easy to cover the real complications of Coflex. (4) Coflex will cause complications such as internal fixation loosening, spinous process fractures, recurrence of degenerative diseases, and heterotopic ossification, leading to secondary surgery. There is no specific standard for the use of Coflex, and the application scope has not been completely unified. Therefore, the clinical application of Coflex still needs further exploration.