Jiang Yize, Wei Yi, Liu Yuxuan, Yang Jiaxu, Zhou Kexin, Yang Haisheng
Department of Biomedical Engineering, College of Chemistry and Life Science, Beijing University of Technology, 100 Pingleyuan, Chaoyang District, Beijing 100124, China.
Department of Spinal Surgery, Beijing Jishuitan Hospital, Beijing 100035, China.
J Biomech. 2025 Mar;181:112542. doi: 10.1016/j.jbiomech.2025.112542. Epub 2025 Jan 30.
Screw loosening remains a serious complication for patients undergoing pedicle screw fixation surgeries. An accurate risk prediction is significant for prevention of screw loosening through preoperative planning. In this study, we proposed a novel index, namely the bone mineral density surrounding the screw thread (thread BMD), and tested its predictability in screw loosening.
86 screws (18 loosening and 68 non-loosening) from L3-L5 of 20 patients who experienced pedicle screw loosening were analyzed. The preoperative and postoperative quantitative CT scans of the same vertebra were spatially registered and a helix-based approach was developed to extract the thread BMD. BMDs of the vertebral body, the pedicle and the screw trajectory were also measured from the preoperative CT scans. Finite element analysis was conducted to determine pullout strength and tissue failure around the screw. Receiver operating characteristic (ROC) curve analysis was used to assess the performances of all BMD indices and pullout strength in predicting screw loosening. Linear regression was used to examine correlations between different BMD indices and screw pullout strength.
The thread BMD had the greatest value of area under the curve (AUC = 0.73, p = 0.004) compared to vertebral BMD (AUC = 0.51, p = 0.923), pedicle BMD (AUC = 0.56, p = 0.474) and trajectory BMD (AUC = 0.67, p = 0.020). Also, the thread BMD showed a stronger correlation with the pullout strength (r = 0.83, p < 0.001) than vertebral BMD (r = 0.59, p < 0.001), pedicle BMD (r = 0.65, p < 0.001) and trajectory BMD (r = 0.60, p < 0.001).
We developed a novel approach to measure a newly-defined thread BMD, which indicates superior capacities over other BMD indices in predicting pedicle screw loosening.
螺钉松动仍是接受椎弓根螺钉固定手术患者的严重并发症。准确的风险预测对于通过术前规划预防螺钉松动具有重要意义。在本研究中，我们提出了一种新指标，即螺钉螺纹周围的骨密度（螺纹骨密度），并测试了其对螺钉松动的预测能力。
对20例经历椎弓根螺钉松动患者L3 - L5节段的86枚螺钉（18枚松动，68枚未松动）进行分析。对同一椎体术前和术后的定量CT扫描进行空间配准，并开发了一种基于螺旋的方法来提取螺纹骨密度。还从术前CT扫描中测量椎体、椎弓根和螺钉轨迹的骨密度。进行有限元分析以确定螺钉周围的拔出强度和组织破坏情况。采用受试者操作特征（ROC）曲线分析来评估所有骨密度指标和拔出强度在预测螺钉松动方面的性能。使用线性回归来检验不同骨密度指标与螺钉拔出强度之间的相关性。
与椎体骨密度（AUC = 0.51，p = 0.923）、椎弓根骨密度（AUC = 0.56，p = 0.474）和轨迹骨密度（AUC = 0.67，p = 0.020）相比，螺纹骨密度的曲线下面积最大（AUC = 0.73，p = 0.004）。此外，螺纹骨密度与拔出强度的相关性（r = 0.83，p < 0.001）比椎体骨密度（r = 0.59，p < 0.001）、椎弓根骨密度（r = 0.65，p < 0.001）和轨迹骨密度（r = 0.60，p < 0.001）更强。
我们开发了一种测量新定义的螺纹骨密度的新方法，该方法在预测椎弓根螺钉松动方面显示出优于其他骨密度指标的能力。
