P35. Comprehensive analysis of novel uniportal trans-Kambin endoscopic lumbar interbody fusion with over one year of CT-based fusion evaluation and clinical follow-up

Abstract

BACKGROUND CONTEXT

Full-endoscopic lumbar interbody fusion (FELIF) is an evolving technique for lumbar degenerative disease (LDD). Among FELIF approaches, the novel FELIF technique, a modified trans-Kambin approach called Kambin Torpedo FELIF (KT-FELIF), enables bilateral decompression through a unilateral trajectory while allowing extensive discectomy and thorough endplate preparation. This study analyzes clinical, radiological, and procedural trends in KT-FELIF, including fusion progression, structural changes, and surgical refinements.

PURPOSE

This study aims to evaluate the clinical and radiological outcomes of KT-FELIF, particularly focusing on its effectiveness in achieving direct bilateral decompression, fusion progression, and structural stability. Additionally, it examines the influence of patient factors, surgical experience, and instrumentation refinements on fusion rates, surgical efficiency, and complication profiles.

STUDY DESIGN/SETTING

This is a retrospective observational study conducted at a single institution, analyzing patients who underwent KT-FELIF with a minimum follow-up period of one year. Clinical and radiological outcomes were systematically assessed using validated scoring systems and imaging modalities, including computed tomography (CT) for fusion evaluation.

PATIENT SAMPLE

The study included 75 patients diagnosed with lumbar degenerative disease (LDD), encompassing a total of 100 treated spinal segments.

OUTCOME MEASURES

Postoperative pain relief, including back pain and bilateral radiculopathy, was assessed to evaluate clinical improvement. Fusion progression was analyzed using CT scans and Bridwell grading to determine the extent of bony integration. Imaging assessments included changes in disc height, lordotic angle, foraminal expansion, spinal canal cross-sectional area, and adjacent segment stability. Surgical efficiency was measured based on operative time trends, while complication rates, including vertebral osteolysis, cage-related issues, infection, nerve injury, and heterotopic ossification, were documented.

METHODS

A retrospective analysis was conducted on 75 patients with lumbar degenerative disease (LDD), encompassing 100 treated spinal segments. The study followed patients for at least one year, assessing demographic factors including age, smoking status, osteoporosis medication use, and comorbidities in relation to endoscopic fusion outcomes. Clinical outcomes were evaluated preoperatively and postoperatively, including back pain severity, radiculopathy, and pain intensity on both ipsilateral and contralateral sides. Imaging assessments included adjacent segment stability, changes in disc height, lordotic change before and after surgery, foraminal expansion, and spinal canal cross-sectional area increase. We also analyzed the impact of Modic changes, fusion bone volume, and fusion bone graft containment on fusion speed, with fusion assessment performed using CT scans, while the degree of fusion success was classified using the Bridwell grade. Clinical and radiographic complications, including vertebral osteolysis, cage-related issues, infection, nerve injury, and other potential complications, were also documented. The relationship between surgeon experience and the use of specialized instruments was assessed to evaluate surgical efficiency.

RESULTS

Postoperative back pain and bilateral radicular pain significantly improved within two weeks. Surgical duration showed a decreasing trend, possibly influenced by surgical experience and refinements in technique. Postoperative imaging indicated improved stability and effective decompression. Fusion appeared to progress more rapidly in patients with Modic changes. Trends suggested an acceleration in fusion rates over time, potentially related to surgical refinements and changes in bone graft implantation techniques. Artificial bone substitute did not show a clear impact on fusion. Vertebral osteolysis was frequently observed with screw loosening but was not directly associated with cage subsidence or adverse clinical outcomes. The overall complication rate remained low, with a few cases of heterotopic ossification and one infection successfully managed with antibiotics. No cases of neurological injury were reported.

CONCLUSIONS

KT-FELIF enables effective bilateral direct decompression, leading to significant relief of bilateral radicular pain and back pain within two weeks postoperatively. This evolution of the trans-Kambin fusion technique demonstrates that it no longer relies solely on indirect decompression via cage augmentation. Imaging findings show a significant postoperative expansion of the dural sac and bilateral foramen. Postoperative dynamic X-rays indicate increased stability at adjacent levels, with reduced flexion and extension motion compared to preoperative assessments. In patients with Modic changes, fusion progression appeared notably faster. With increasing surgical experience, refinements in bone graft implantation techniques, and the adoption of specialized discectomy instruments, both surgical time and fusion speed showed improvement. However, the type of artificial bone used did not appear to significantly influence fusion outcomes. Some patients exhibited vertebral osteolysis, though this did not necessarily correlate with cage subsidence or increased postoperative pain. However, it was frequently associated with screw loosening. The overall complication rate remained low, with a few cases of heterotopic ossification and one infection that resolved with three months of oral antibiotics. No cases of surgery-induced neurological deficits were reported. Overall, KT-FELIF has proven to be a highly effective and dependable surgical technique, providing substantial neurological symptom relief, solid bony fusion, and a consistently low complication rate in follow-ups exceeding one year.

FDA Device/Drug Status

This abstract does not discuss or include any applicable devices or drugs.