Necessity of routinely performing foraminoplasty during percutaneous endoscopic transforaminal discectomy in treating lumbar disc herniation

Objective To analyze the necessity of routinely performing foraminoplasty during percutaneous transforaminal endoscopic discectomy (PETD). Methods A total of 412 patients including 231 males and 181 females with an average age of 39.1±13 (20-80) years were enrolled in the present study. All patients were preoperatively diagnosed with single-segment lumbar disc herniation and underwent PETD by the same surgical group. The affected segments were at L3-4 in 32 cases, L4-5 in 289 cases, and L5S1 in 91 cases. Among them, 306 cases had no prolapse, 89 had mild up/down prolapse, and 17 had severe prolapse. MRI sagittal imaging was used to measure the height and width of the intervertebral foramen of L3, 4, L4, 5 and L5S1 segments, the distance between the lower edge of vertebral pedicle and the upper edge of the lower vertebral pedicle and the distance between the point 3 mm to the ventral side of the intervertebral space to the superior articular process. The necessity of performing foraminoplasty was evaluated by measuring the change of intervertebral foramen width using dynamic X-ray and verified during operation. Results The height of the intervertebral foramen of L3,4, L4,5 and L5S1 segments were 1.99±0.25, 1.89±0.15 and 1.52±0.26 cm, respectively. The width of the intervertebral foramen was 0.78±0.14, 0.75±0.13 and 0.64±0.13 cm, respectively. The distance between the lower edge of vertebral pedicle and the upper edge of the lower vertebral pedicle were 1.14±0.17, 1.05±0.16, and 0.98±0.19 cm, respectively. The distance between the point 3 mm to the ventral side of the intervertebral space to the superior articular process were 1.11±0.31, 1.17±0.20, and 0.95±0.14 cm, respectively. The width of the intervertebral foramen of the L3, 4 and L4,5 segments was significantly greater at the over-flexion position than at the over-extension position (P<0.05). Intraoperative verification showed that 347 cases (group A) did not need foraminoplasty. However, the other 65 patients (group B) needed foraminoplasty, including 31 at L4, 5 segment and 34 at L5S1 segment. One patient in group A and one in group B underwent revision operation due to residual intervertebral disc. At 2 years of follow-up, recurrence occurred in 4 patients in group A and 2 patients in group B. The ODI score and JOA score in group A and B were 18%±9%, 24.2±1.3 and 16%±7%, 23.9±1.3, respectively. There were not significantly different between patients in group A and B (t=1.70, P=0.090; t=1.71, P=0.088). The VAS score of lumbar pain of patients in group A was better than that of patients in group B (P<0.05). Conclusion Most of PETD of L3-S1 segments can reach the therapeutic target without performing foraminoplasty with half-half technique combined with far lateral access technique. Due to the special anatomical position of L5-S1 segment, the probability of performing foraminoplasty during operation is much higher. Performing foraminoplasty or not depends on the preoperative measurement of foramina and verification during the operation. Key words: Lumbar vertebrae; Intervertebral disc displacement; Diskectomy, percutaneous; Foraminotomy