Abstract
BACKGROUND: To investigate the clinical effects and biomechanical properties of various coronal plane angulations during foraminoplasty in transforaminal endoscopic lumbar discectomy. METHODS: From December 2018 to December 2020, 72 patients who underwent transforaminal endoscopic lumbar discectomy were enrolled retrospectively. The patients were divided into 3 groups according to the different coronal plane angulations during foraminoplasty: group A, 0° < coronal plane angulation ≤ 10°; group B, 10°< coronal plane angulation ≤ 30°; and group C, 30° < coronal plane angulation ≤ 50°. The 3 groups were compared in terms of general data, clinical outcomes, and imaging parameters. In addition, a standard L4-5 3-dimensional finite element model was established and validated. A trephine with an 8.5-mm diameter was designed to simulate foraminoplasty at angles α1 = 10°, α2 = 30°, and α3 = 50° with the coronal plane of the normal model. Three foraminoplasty models were constructed. The differences in range of motion and L4-5 intradiscal pressure were compared among the models. RESULTS: There were 13 cases in group A, 43 cases in group B, and 16 cases in group C. Sex, age, surgical segment, length of hospital stay, duration of operation, intraoperative bleeding, time of fluoroscopy, and preoperative, postoperative, and 1-year follow-up clinical outcome scores and imaging parameters did not differ significantly between the 3 groups (p > 0.05). However, as the coronal plane angulation increased, postoperative foraminal height tended to decrease, as did the proportion of lumbar instability. There was no significant difference in foraminal height and width at 1 year postoperatively compared to preoperative values in group A (p > 0.05), but there was in groups B and C (p < 0.05). All groups showed a statistically significant decrease in intervertebral space height when compared to preoperative values (p < 0.05). The finite element analysis results were consistent with the clinical results. When compared to the normal model, the range of motion and intradiscal pressure of foraminoplasty models were significantly increased with extension, left bending, and left rotation, and the increasing trend was α1 < α2 < α3. CONCLUSIONS: When performing foraminoplasty, reducing coronal plane angulation and depressing the trephine to a near horizontal position could be considered an operative technique that protects lumbar stability.