Ligamentum Flavum Flap Technique in Lumbar Microdiscectomy

Background: Microdiscectomy has been the gold-standard technique for the treatment of lumbar disc herniation. A potential reason for suboptimal symptom resolution following microdiscectomy is postoperative epidural fibrosis¹. Preservation of the ligamentum flavum through the use of the ligamentum flavum flap technique reduces postoperative epidural fibrosis and leads to a favorable long-term prognosis.

Description: The L5-S1 interlaminar space on the operative side is exposed with use of a standard microsurgical approach, and the level is confirmed. The ligamentum flavum is held taut with use of tooth forceps, holding onto superficial layers, and a flap with its base on the lateral side is created. Initial separation is made at the midline (where the flavum is very thin) with use of a no.-15-blade scalpel. The flap is elevated by detaching the ligamentum flavum between the lower border of the L5 lamina and sacrum with use of a 1-mm Kerrison rongeur. The detachment of the ligamentum flavum is performed carefully, preserving the attachments on the lateral border. Having a thin base allows the flap to be elevated and rotated, and the flap thus can be tucked into the muscle above the facet joint. The nerve root is retracted, and discectomy is performed according to the location and size of the disc. After achieving good hemostasis, the ligamentum flavum flap is gently rotated back to its normal position. In most cases, the flap can be returned back to its original position without any gap and without any need for suture. Closure is performed in layers.

Alternatives: Nonoperative treatment yields good pain relief in more than 80% of patients with disc herniation. However, if surgery is required, the primary concern for the surgeon is the prevention of postoperative scarring and fibrosis around the nerve root. Previous attempts to mitigate this potential complication have revolved around the placement of a subcutaneous fat graft over the nerve root; however, no firm evidence exists to support this technique. Synthetic materials such as expanded polytetrafluoroethylene, Adcon-L gel (Wright Medical Technologies), and sodium hyaluronate have also been utilized to prevent epidural scarring; however, the ligamentum flavum is a natural biological solution.

Rationale: Postoperative fibrosis may occur if there is a dead space as a result of the excision of the ligamentum flavum or due to inflammation. Restoration of native tissue anatomy with use of the ligamentum flavum technique can prevent such fibrosis, as has been reported previously. In addition to reducing scar formation, preserving the ligamentum flavum can make revision surgery (which is rarely required) safer, as there is less or no epidural fibrosis or nerve root scarring.

Expected outcomes: Patients undergoing this procedure have shown good improvement in the Oswestry Disability Index (ODI) and a clinically notable reduction in visual analog scale (VAS) pain scores in the immediate postoperative period as well as on long-term follow-up. The chances of epidural fibrosis have been shown to be significantly decreased over long-term follow-up. Li et al. reported substantially lower VAS and ODI scores among patients who underwent the ligamentum flavum flap technique compared with a control group, as well as a significantly lower grade of epidural fibrosis at 6 months postoperatively². In a similar study, Özay et al. highlighted significant clinical improvement and reduced chances of postoperative epidural fibrosis in 51 patients who underwent the ligamentum flavum flap technique³. Additionally, Li et al. showed that patient age and the area of the laminar space were the 2 important factors that determine the preservation of the ligamentum flavum, as the failure rate was significantly higher in elderly patients (>43.5 years) and those with small interlaminar space (<1.95 cm²). ODI and VAS scores were substantially better, and fibrosis formation, as assessed on computed tomography (CT) scans with intravenous iopamidol injection, was significantly reduced in patients with preserved ligamentum flavum⁴.

Important tips: Properly set up the operating microscope and fluoroscopy unit in order to ensure accurate starting points.Utilize minimal cautery at all levels of dissection.Hold the ligamentum flavum taut superficially while incising with use of a no.-15 scalpel.Detach the ligamentum flavum while safely preserving the attachments on the lateral border.Perform proper repositioning of the ligamentum flavum after achieving hemostasis.

Acronyms and abbreviations: ODI = Oswestry Disability IndexVAS = visual analog scaleCT = computed tomographyLF = ligamentum flapSLRT = straight leg raise testAP = anteroposteriorMRI = magnetic resonance imagingASIS = anterior superior iliac spineCSF = cerebrospinal fluid.