## 4 Discussion  
Lumbar fusion surgery constitutes a widely accepted treatment strategy for lumbar diseases, such as lumbar stenosis, trauma, tumors, and spondylolisthesis. Development of new instruments and improved bone graft materials have resulted in higher fusion and clinical success rates. Nevertheless, many complications and problems related to fusion surgery have been reported, with ASP being one of the most troublesome issues [18; 19; 20]. The various types of pathological changes of the adjacent segments are spondylolisthesis, canal stenosis, disc herniation, disc height loss, osteophyte formation, and scoliosis. The incidence of radiographic adjacent segmental pathology ranges from 8% to as high as 100%, with a symptomatic disease in 5.2%-18.5% of cases, as reported in studies with an average follow-up of 36-396 months [21]. The most common reported risk factors for developing ASP are age, sex, body mass index (BMI), smoking, osteoporosis, preexisting degeneration of an adjacent disc, violation of adjacent facet during surgery, sagittal imbalance, rigid fixation, and length of fusion [21]. Despite extensive research, the exact causes of ASP are not fully elucidated, but changes in spinal biomechanics, including increased facet loading, increased intradiscal pressure, and hypermobility at the segments adjacent to the fusion levels, are thought to play a key role is ASP pathogenesis [21]. [PERSON] et al. found that as flexion motion increases, intradiscal pressure increases within adjacent levels [22]. [PERSON] et al. reported a significant increase in weight bearing and load burden of the posterior column at the adjacent segments following lumbar fusion [23]. [PERSON] et al. reported that facet joint violation occurred in over 30% of patients and was triggered by 20% of screws [13]. [PERSON] et al. reported that top-level facet joint violations occurred in 15% of cases with cephalad pedicle screws and in 24% of patients [24]. In our study, as mentioned above, 55.4% of the cases and 47.3% of the screws in the ASP group \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **ASP Group** & **Non-ASP Group** & **\(p\)-Value** \\  & **(\(n\) = 56)** & **(\(n\) = 31)** & **\(p\)-Value** \\ \hline  & 0 & 25 (45\%) & 18 (58\%) & \\  & 1 & 8 (14\%) & 4 (13\%) & \\ Score & 2 & 4 (7\%) & 7 (23\%) & \\  & 3 & 11 (20\%) & 2 (6\%) & \\  & 4 & 8 (14\%) & 0 (0\%) & \\ Mean score & 1.4 & 0.8 & \textless{}0.05 \\ \hline \hline \end{tabular}  
* Score measures: 0, if non-violated (Type I); 1, if violation is suspected (type II); 2, if facet joint is definitely violated by the screw (type III). Independent \(t\)-test data are presented as median \(\pm\) standard deviation. The \(p\)-values are of inter-group comparisons, with \(p<0.05\) indicating statistical significance.  
\end{table} 
Table 4: Score of facet joint violation. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Type (Score)** & **ASP Group** & **Non-ASP Group** \\  & **(112 Screws)** & **(62 Screws)** \\ \hline I (0) & 59 screws (52.7\%) & 43 screws (69.4\%) \\ II (1) & 26 screws (23.2\%) & 14 screws (22.6\%) \\ III (2) & 27 screws (24.1\%) & 5 screws (8.0\%) \\ \hline \hline \end{tabular}  
* Non-violated (Type I); if violation is suspected (type II); facet joint is definitely violated by the screw (type III).  
\end{table} 
Table 3: Incidence of superior facet joint violation on CT scan in the ASP group and non-ASP group. and 41.9% of the cases and 30.6% of the screws in the non-ASP group were associated with facet joint violations. The incidence of facet joint violation reported here was higher than other studies, as we applied stricter diagnostic criteria, for example, by including any doubtful part in C.T. [PERSON] et al. reported that bilateral facet joint violation contributes to torsional instability after surgery [6].