Bone absorption of spinous process and its risk factors after interspinous dynamic stabilization device implantation one year after operation

English Keywords:Spinous process  Bone absorption  Interspinous stabilization device  Wallis  Risk factor

English Abstract:

  【Abstract】 Objectives: To investigate the bone absorption of L4 and L5 spinous process at 1 year post-operation and its risk factors. Methods: Patients from 2009 to 2011 in our department undergoing L4/5 Wallis implantation were reviewed retrospectively. According to the bone absorption rate meassured from the height, length and width of L4 and L5 spinous process on one-week and one-year X-ray image, patients were divided into two groups: Bone absorption group and Non bone absorption group. The patients′ gender, age, BMI, smoking, osteoporosis, operation time, blood loss, low back muscle exercise, time of brace applied, height of preoperative L4/5 interspinous space, height of preoperative L4/5 disc space and LL, and disc degeneration grade measured by preoperative and 1-year postoperative magnetic resonance image(MRI) as the VAS, JOA and ODI score. Chi-square test, T-test and Binary logistic regression analysis were compared between 2 groups. Results: 44 patients completed the one-year follow-up, there were 24 males and 20 females, with an average age of 42.7 years. 29 patients had bone absorption, of them, 16 were women(55.2%), 16 patients had both L4 and L5 spinous process bone absorption simultaneously. Severe bone absorption occurred at the height of L4 and L5 spinous process, with an absorption rate of (16.28±1.46)% and (22.93±1.63)% respevtively. 7 patients with preoperative osteoporosis all showed bone absorption. Independent risk factors for bone absorption were: preoperative BMI(odds ratio[OR]: 1.337, 95% confidence interval[CI]: 1.048-1.705), 3050 (OR:11.718, 95% CI:1.535-89.436). MRI, VAS, JOA and ODI had no statistically significant differences between the two groups(P>0.05). Conclusions: Bone absorption after Wallis implantation can be observed one year after operation, Preoperative BMI and LL are independent risk factors, osteoporosis is also one of the possible causes. However, there is no significant association between the onset of this phenomenon with postoperative symptoms.