Reoperation rate and risk factors of reoperation for ossification of the posterior longitudinal ligament (OPLL): a systematic review and meta-analysis.

Revision surgery for OPLL is undesirable for both patients and physicians. However, the risk factors for reoperation are not clear. Thus, we sought to review the existing literature and determine the factors associated with higher reoperation rates in patients with OPLL. A search was performed using Pubmed, Embase, Web of Sciences, and Ovid to include studies regarding the risk factors of reoperation for OPLL. RoBANS (Risk of Bias Assessment tool for Nonrandomized Studies) was used for risk of bias analysis. Heterogeneity of studies and publication bias was assessed, and sensitivity analysis was performed. Statistical analysis was performed with a p-value < 0.05 using SPSS software (version 23). Twenty studies with 129 reoperated and 2,793 non-reoperated patients were included. The pooled reoperation rate was 5% (95% CI: 4% to 7). The most common cause of reoperation was residual OPLL or OPLL progression (n = 51, 39.53%). An increased risk of additional surgery was found with pre-operative cervical or thoracic angle (Standardized mean difference = -0.44; 95% CI: -0.69 to -0.19; p = 0.0061), post-operative CSF leak (Odds ratio, OR = 4.97; 95% CI: 2.48 to 9.96; p = 0.0005), and graft and/or hardware failure (OR = 192.09; 95% CI: 6.68 to 5521.69; p = 0.0101). Apart from the factors identified in our study, the association of other variables with the risk of second surgery could not be ruled out, owing to the complexity of the relationship and significant bias in the current literature.

Analysis of the mechanical response of damaged human cervical spine ligaments.

BACKGROUND: Cervical spine ligaments that protect the spinal cord and stabilize the spine are frequently injured in motor vehicle collisions and other traumatic situations. These injuries are usually incomplete, and often difficult to notice. The focus of the presented study is placed on analysis of the effect of subfailure load on the mechanical response of the three main cervical spine ligaments: the anterior and the posterior longitudinal ligament and the ligamentum flavum. METHODS: A total of 115 samples of human cadaveric ligaments removed within 24-48 h after death have been tested. Uniaxial tension tests along the fiber direction were performed in physiological conditions on a custom designed test equipment. The ligaments were loaded into an expected damage zone at two different subfailure values (based on previously reported reference group of 46 samples), and then reloaded to failure. FINDINGS: The main effect of a high subfailure load has proven to be the toe elongation change. The toe elongation increase is affected by the subfailure load value. While anterior and posterior longitudinal ligament showed similar changes, the smallest subfailure effect was found in ligamentum flavum. INTERPRETATIONS: The normal physiological region of the cervical spine ligaments mechanical response is modified by a high subfailure load. The observed ligament injury significantly compromises ligament ability to give tensile support within physiological spinal motion.