Risk factors for screw loosening in patients with lumbar degenerative spondylolisthesis treated with Dynesys dynamic stabilization

Q: How was pedicle screw loosening defined in the study?

Screw loosening was defined as the presence of a halo or double-halo sign on plain radiography.

Q: What is the overall incidence of screw loosening after Dynesys dynamic stabilization?

The screw loosening rate was 4.8% among screws and 11.7% among patients.

Q: Which factors were associated with increased risk of pedicle screw loosening after DDS?

Age over 65 years, smoking, segmental range of motion greater than 13°, and L1 vertebral body Hounsfield unit below 110 were identified as risk factors.

Sep 29, 2026

Uploaded by Noah

Posterior decompression combined with Dynesys dynamic stabilization (DDS) is used for degenerative spondylolisthesis, yet postoperative pedicle screw loosening (PSL) can lead to unsatisfactory outcomes and reoperation. A retrospective cohort analyzed 94 L4-L5 grade I patients undergoing elective DDS from May 2008 to February 2015. Screw loosening was defined by halo/double-halo signs on plain radiographs. Multivariable analysis identified age >65, smoking, segmental ROM >13°, and low L1 vertebral body Hounsfield unit (<110) as PSL risks. Reoperations occurred without screw breakage.

LanguageEnglish

CategoryHealthcare

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Pages5

Reading Time13 min

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Abstract

1. INTRODUCTION

2. METHODS

2.1. Study design and patient selection

J Chin MedAssoc Original article Risk factors for screw loosening in patients with lumbar degenerative spondylolisthesis treated with Dynesys dynamic stabilization Yen-Chun Huanga,b, Hsi-Hsien Lina,b, Shih-Tien Wangc, Po-Hsin Choua,b, Chien-Lin Liua,b, Yu-Cheng Yaoa,b,* aSchool of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan, ROC; bDepartment of Orthopedics and Traumatology, Taipei Veterans General Hospital, Taipei, Taiwan, ROC; cDepartment of Orthopedics and Traumatology, Kinmen Hospital, Ministry of Health and Welfare, Kinmen, Taiwan, ROC Abstract Background: Posterior decompression with Dynesys dynamic stabilization (DDS) is an effective treatment option for degenerative spondylolisthesis. However, postoperative pedicle screw loosening (PSL) often results in poor outcomes. Determining possible risk factors may aid in making informed decisions. This study aimed to evaluate the incidence and risk factors for PSL in patients who underwent elective DDS. Methods: We conducted a retrospective analysis of 94 patients with L4-L5 grade I degenerative spondylolisthesis who underwent DSS at a single academic institution between May 2008 and February 2015. Screw loosening was defined as the presence of a halo or double-halo sign on plain radiography. Results: The rate of screw loosening was 4.8% among screws and 11.7% among patients. Multivariable analysis revealed that age >65 years, smoking, segmental range of motion (ROM) >13°, and L1 vertebral body Hounsfield unit <110 were risk factors for PSL after DDS. Five reoperations were performed; however, no instances of screw breakage were observed. Conclusion: Our study identified risk factors for PSL after DDS, including older age, smoking, larger preoperative segmental ROM, and lower L1 vertebral body HU, which could assist in preoperative decision-making and surgical planning. Keywords: Dynesys dynamic stabilization; Lumbar degenerative spondylolisthesis; Screw loosening 1. INTRODUCTION Posterior decompression with Dynesys dynamic stabilization (DDS) is an effective treatment method for symptomatic degenerative spondylolisthesis because it prevents slippage progression and decreases the incidence of revision.1 Compared with rigid fixation and fusion, DDS has been proposed to reduce the range of motion (ROM) at the treated level, reducing symptomatic adjacent segment disease. Recent studies have investigated the segmental ROM between DDS implantation and concluded that approximately 25% to 50% of the ROM is restored.2 Although the benefits of preserving segmental ROM have been proposed,3–5 evidence is scarce regarding whether it is associated with any possible adverse events. The DDS involves a pedicle screw-based instrument, and pedicle screw loosening (PSL) is a common complication that causes poor clinical outcomes and reoperation.6 The incidence of PSL is 19.7% in patients and 4.6% in screws after DDS for one- and two-level lumbar spondylosis.7 Osteoporosis,2 long *Address correspondence. Dr. Yu-Cheng Yao, Department of Orthopedics and Traumatology, Taipei Veterans General Hospital, 201, Section 2, Shi-Pai Road, Taipei 112, Taiwan, [ROC. E-mail address: orthycyao@gmail.com](ROC. E-mail address: orthycyao@gmail.com) (Y.-C. Yao). Conflicts of interest: The authors declare that they have no conflicts of interest related to the subject matter or materials discussed in this article. Journal of Chinese Medical Association. (2025) 88: 151-155. Received April 26, 2024; accepted September 11, 2024. doi: 10. 1097/JCMA.0000000000001187 Copyright © 2024, the Chinese Medical Association. This is an open access article under the CC BY-NC-ND license ([http://creativecommons.org/licenses/](http://creativecommons.org/licenses/)[ ](http://creativecommons.org/licenses/)[by-nc-nd/4.0/](by-nc-nd/4.0/)) fusion length,2,4 sacral involvement,4 and failure to gain lumbar lordosis postoperatively are associated with a higher risk of PSL. Among these

FAQs

How was pedicle screw loosening defined in the study?

Screw loosening was defined as the presence of a halo or double-halo sign on plain radiography.

What is the overall incidence of screw loosening after Dynesys dynamic stabilization?

The screw loosening rate was 4.8% among screws and 11.7% among patients.

Which factors were associated with increased risk of pedicle screw loosening after DDS?

Age over 65 years, smoking, segmental range of motion greater than 13°, and L1 vertebral body Hounsfield unit below 110 were identified as risk factors.

Sep 29, 2026

Uploaded by Noah