Application of 3D printing skeletal models in percutaneous endoscopy lumbar discectomy

Abstract

Objective To explore the clinical value of 3D printed skeletal model in percutaneous spinal endoscopic lumbar discectomy. Methods Clinical data of 62 patients with lumbar disc herniation admitted to the department of spine surgery of the Third Affiliated Hospital of Suzhou University from July 2016 to October 2017 were retrospectively analyzed. There were 34 males and 28 females, the age ranged from 32 to 67 years, with an average of 52.3 years. The lesion segments were all L4/5 segments, including 8 cases with lateral recess stenosis. The types of disc herniation included 18 cases of paracentral disc herniation, 40 cases of lateral disc herniation and 4 cases of extreme lateral disc herniation. The WSPS V1.0 medical image processing software was used to process the imaging data to generate a GCODE format file recognizable by the 3D printer. A polylactic acid material was used to print a complete segmental lumbar skeletal model by using a 3D printer. According to the location of the lesion, the bilateral intervertebral foramen were divided into the affected side group and the healthy side group. The 5 points and 2 lines anatomical landmarks were determined on the skeletal model, and the 3 distances and 1 of the intervertebral foramen (intervertebral foramen width, posterior edge height of the intervertebral disc, intervertebral foramen height and ventral inclination angle of the superior articular process) were measured. Endoscopic lumbar discectomy via percutaneous intervertebral foramen approach was performed on all affected sides. According to whether or not foraminoplasty was performed during the operation, the patients were divided into two groups: foraminoplasty group and the non-foraminoplasty group. The three distances and one of the intervertebral foramen between the affected and healthy sides of the skeletal model, and the three distances and one of the intervertebral foramen between the foraminoplasty group and the non-foraminoplasty group were compared. Results In the print model, the width of the intervertebral foramen, the height of the posterior edge of the intervertebral disc, the height of the intervertebral foramen and the ventral inclination angle of the superior articular process in the affected side group were (6.30±1.71) mm, (4.88±1.63) mm, (21.07±3.78) mm and 16.28°±1.13°, respectively. The healthy side groups were (7.27±1.86) mm, (5.3±1.71) mm, (18.57±3.34) mm and 25.72°±1.03°, respectively. The width of the intervertebral foramen and the ventral inclination angle of the superior articular process in the affected side group were smaller than those in the healthy side group, and the difference was statistically significant (t=2.133, 2.877, all P values 0.05). All patients successfully completed the operation. Among them, 38 patients did not undergo foraminoplasty and 24 patients underwent foraminoplasty. Among 62 patients, the width of the affected intervertebral foramen, the height of the posterior edge of the affected intervertebral disc, the height of the affected intervertebral foramen and the ventral inclination angle of the affected superior articular process in the foraminoplasty group were (4.77±0.83) mm, (4.97±1.35) mm, (16.23±2.02) mm and 11.50°±2.15°, respectively, and those in the non-foraminoplasty group were (7.42±1.24) mm, (5.19±1.88)mm, (16.63±1.94) mm and 22.22°±4.28°, respectively. The width of intervertebral foramen, the height of posterior edge of intervertebral disc and the ventral inclination angle of the superior articular process in foraminoplasty group were smaller than those in non-foraminoplasty group. There were significant differences in the width of intervertebral foramen and the ventral inclination angle of superior articular process (t=6.681, 8.001, all P values 0.05). The width of intervertebral foramen was 3.34-5.92 mm and the ventral inclination angle of superior articular process was 9°-14° in 24 patients undergoing foraminoplasty. The results showed that the width of the affected intervertebral foramen was less than 6.0 mm and the ventral inclination angle of the superior articular process was less than 15° in L4/5 segment patients undergoing intervertebral foraminoplasty. Conclusions Using 3D printing skeleton model, the parameters of intervertebral foramen shape can be accurately measured before operation, the trial pathway can be established, the surgical approach and method can be selected, the foraminoplasty and can be predicted and the difficulty of operation can be predicted. It has guiding significance for the operation of percutaneous endoscopic lumbar discectomy. Key words: Intervertebral disc displacement; Lumbar vertebrae; Diskectomy, percutanecus; Three-dimensional printing; Surgical procedures, endoscope; Intervertebral foramen; Foraminoplasty