The implementation of the femoral neck surgical central axis guide pins to establish the stable implanting-screws spatial coordinate system.

backgroundFor internal-fixation of femoral neck fractures, determining the femoral neck central axis intraoperatively and calculating screw coordinates accurately remain crucial but extremely challenging. Previous research has shown that the flat anterior cortex of the femoral neck base (AC-FNB) can be used to establish a constant spatial coordinate system parallel to the surgical central axis (SCA) of the femoral neck theoretically, promising for solving the above conundrums. In this study, based on osseous marker AC-FNB, three guide pins of femoral neck surgical central axis (GPs-SCA) were implanted to build the stable implanting-screws spatial coordinate system, for providing convenience for controllable inserting femoral neck screws accurately during surgery.

methodsAfter three-dimensional-reconstruction of forty sawbone synthetic femoral necks by CT scanning, the axial safety target areas (ASTA) for drilling femoral neck screw channels were determined by the intersection method to measure parameters such as superior-inferior diameter (D-SI) and anterior-posterior diameter (D-AP), verifying sawbones meet the inclusion criteria. Utilizing the robot-assisted patented technologies, the GPs-SCA were drilled with reference to the AC-FNB. Postoperatively, the ratio coordinates of each GP-SCA and the angle deviations between the GPs-SCA and the SCA of the corresponding femoral neck were measured using orthogonal X-rays and CT three-dimensional-reconstructions. The parameters of each GP-SCA on both X-rays and CT scans were then calculated, and paired t-tests were conducted.

resultsAll preoperative parameters were within normal ranges for the femoral neck. Postoperatively, angular deviations between GPs-SCA and SCA were less than 5° on both orthogonal X-rays and CT scans. The Y-axis ratio coordinates of GP-SCA were - 0.41% ± 2.32% on orthogonal X-rays and - 0.32% ± 2.29% on axial CT, while the Z-axis ratio coordinates of GP-SCA were 0.74% ± 2.76% on orthogonal X-rays and 0.64% ± 2.87% on axial CT, respectively. There were no significant differences found (Py = 0.245, Pz = 0.185).

conclusionsBy utilizing the AC-FNB as a landmark, GPs-SCA could be successfully implanted within the allowable error ranges to facilitate building a reliable spatial rectangular coordinate system for controllable implanting screws. This coordinate system offers convenience in determining the directions of implanting screws, standardizing orthogonal fluoroscopies, registering X-rays and CT images, and converting X-ray data to axial coordinates.