S1 Dataset -

Purpose
Polyaxial locking plates rely on the alignment between the thread-to-thread connections of the screw head and the plate hole. These implants have provided substantial support for surgeons. In particular, extended screw positioning have proven to be beneficial in the fixation of challenging fractures. This study aimed to investigate the mechanical properties of ChM 5.0 ChLP polyaxial screws inserted in off-axis trajectories, including multiple insertions and to correlate these parameters with the screw head and the plate hole thread-to-thread engagement.
Methods
Polyaxial locking screws were inserted into the plates at various angles (0°,10°,15°, -15° off-axis). Multiple time inserted screws were placed firstly at 15°, then 0° and finally -15° off-axis in the same plate hole. A microCT scan of the plate-hole and screw-head interface was conducted before destructive tests. Representative screws from each group were also examined by Scanning Electron Microscope.
Results
The standard insertion at 0° sustained the greatest maximum bending strength without relocation in the screw hole. Screws inserted at 10° and 15° (one time) showed a significant reduction in load-to-failure of up to 36% and 55%, (p = 0.001) (p = 0.001) respectively. Screws inserted at -15° after a maximum of three multiple insertions with angle shift, showed a total reduction in force of up to 70% (p = 0.001). A microCT analysis of thread engagement showed significant correlations. However, the results obtained for multiple insertions were highly variable.
Conclusions
ChM 5.0 ChLP polyaxial locking system has valuable properties that foster fracture fixation, providing various surgical options. Nevertheless, the freedom of off-axis placement and multiple insertions of the screws comes at the price of reduced force. When possible surgeons should minimize the angles of insertions.

一、研究目的
多轴锁定接骨板（Polyaxial Locking Plate）的性能依赖于螺钉头与接骨板孔的螺纹啮合对齐精度。此类植入物可为外科医师提供可靠的支撑效果，尤其在复杂骨折的固定中，扩大螺钉置入范围已被证实具有显著益处。本研究旨在探究ChM 5.0 ChLP多轴螺钉（Polyaxial Screw）在偏轴置入路径下的力学性能（含多次置入场景），并将相关参数与螺钉头及接骨板孔的螺纹啮合情况进行关联分析。
二、研究方法
将多轴锁定螺钉以不同偏轴角度（0°、10°、15°、-15°）置入接骨板孔内。多次置入组的螺钉则先以15°偏轴角度置入，随后依次以0°、-15°偏轴角度置入同一接骨板孔。破坏性试验前，对所有接骨板孔与螺钉头的界面进行显微CT（microCT）扫描。此外，采用扫描电子显微镜（Scanning Electron Microscope, SEM）对各组的代表性螺钉进行了观测。
三、研究结果
标准置入（0°偏轴）的螺钉可承受最高的最大弯曲强度，且未出现螺钉在接骨板孔内移位的情况。单次置入的10°、15°偏轴螺钉的失效载荷分别显著降低了最高达36%和55%（均p=0.001）。经最多3次角度偏移的多次置入后再以-15°偏轴角度置入的螺钉，其总载荷降低幅度最高可达70%（p=0.001）。显微CT对螺纹啮合情况的分析结果显示二者存在显著相关性，但多次置入场景下的检测结果离散度较高。
四、研究结论
ChM 5.0 ChLP多轴锁定系统具备助力骨折固定的优良性能，可为临床提供多样化的手术选择。然而，螺钉偏轴置入与多次置入的操作自由度，是以载荷承载能力下降为代价的。若条件允许，外科医师应尽可能减小螺钉的置入偏轴角度。