To investigate the L₅ pedicle morphological changes during the development and progression of lumbar spondylolysis and further analyze the effects of L₅ pedicle morphological characteristics on the risk of lumbar spondylolysis.

A case-control study was conducted to analyze the image data of 144 patients with lumbar spondylolysis who were admitted to 960th Hospital of Joint Logistic Support Force of PLA from July 2022 to June 2023, including 124 males and 20 females, aged 18-70 years [(35.7±14.4)years]. Of them, 79 patients had bilateral spondylolysis (spondylolysis group) and 65 patients had isthmic spondylolisthesis (spondylolisthesis group). At the same time, 144 volunteers with no obvious structural abnormalities in a lumbar CT scan were selected as the control group. Picture archiving and communication system (PACS) was used to measure the morphological parameters of L₅ pedicle on CT images, including pedicle length (PL), pedicle screw trajectory length (PSTL), pedicle width (PW), pedicle camber angle (PCA), pedicle height (PH), and pedicle isthmus angle (PIA). The differences of each parameter between the left and right sides in the three groups were compared first, and then the data of the left and right sides were merged to compare the differences of each parameter among the three groups. In order to further explore the effects of L₅ pedicle morphological characteristics on the risk of lumbar spondylolysis, the measurement parameters with statistically significant differences between the spondylolysis group and the control group were included in the binary Logistic regression analysis to screen the risk factors of lumbar spondylolysis related to L₅ pedicle morphological characteristics.

There were no significant differences in the values of PL, PSTL, PW, PCA, PH or PIA between the left and right sides in the three groups (P>0.05), indicating those parameters were not affected by the left and right side factors. The values of PL, PSTL, PW, PCA and PIA in the spondylolysis group were (13.5±2.0)mm, (47.6±2.4)mm, (15.5±2.0)mm, (29.0±2.9)°, and (118.6±5.9)° respectively, which were not significantly different from those in the spondylolisthesis group [(13.6±2.0)mm, (47.7±3.2)mm, (15.9±2.7)mm, (28.3±3.1)°, and (119.2±5.8)° respectively] (P>0.05), but the values of the parameters of the above two groups were larger than those of the control group [(12.8±1.7)mm, (45.1±3.1)mm, (14.9±2.0)mm, (25.6±3.0)°, and (106.6±5.5)°] (P<0.05). There was no significant difference in the value of PH between the spondylolysis group [(10.5±1.2)mm] and the control group [(10.8±1.3)mm] (P>0.05), but the values of PH of the above two groups were higher than that in the spondylolisthesis group [(10.0±1.3)mm] (P<0.05). The results of binary Logistic regression analysis showed that the increased PCA (OR=1.40, 95%CI 1.17, 1.67, P<0.01) and increased PIA (OR=1.46, 95%CI 1.30, 1.64, P<0.01) were significantly correlated with lumbar spondylolysis.

The L₅ pedicle in patients with lumbar spondylolysis has longer PL and PSTL, wider PW, and larger PCA and PIA than the normal population, showing the morphological characteristics of being "long, wide and extended". The morphological changes of the L₅ pedicle mainly occur before the fracture of the lumbar isthmus, with increased PCA and PIA being the risk factors for lumbar spondylolysis.

Lumbar vertebrae; Spondylolisthesis; Anthropometry; Risk factors