Importance of Sacrotuberous Ligament in Transgluteal Approach for Sciatic Nerve Entrapment in the Greater Sciatic Notch (Piriformis Syndrome)

Abstract

Objective: The efficacy of sciatic nerve decompression via transgluteal approach for entrapment of the sciatic nerve at the greater sciatic notch, called piriformis syndrome, and factors affecting the surgical outcome were analyzed.

Methods: The outcome of pain reduction was analyzed in 81 patients with sciatic nerve entrapment who underwent decompression through a transgluteal approach. The patients were followed up for at least 6 months. The degree of pain reduction was analyzed using a numerical rating scale-11 (NRS-11) score and percent pain relief before and after last follow-up following surgery. Success was defined by at least 50% reduction in pain measured via NRS-11. To assess the degree of subjective satisfaction, a 10-point Likert scale was used. In addition, demographic characteristics, anatomical variations, and variations in surgical technique involving sacrotuberous ligamentectomy were analyzed as factors that affect the surgical outcome.

Results: At a follow-up of 17.5±12.5 months, sciatic nerve decompression was successful in 50 of 81 patients (61.7%), and the pain relief rate was 43.9±34.17. Subjective improvement based on a 10-point Likert scale was 4.90±3.43. Among the factors that affect the surgical outcome, only additional division of the sacrotuberous ligament during piriformis muscle resection played a significant role. The success rate was higher in the scarotuberous ligementectomy group (79.4%) than in the non-resection group (42.6%), resulting in statistically significant difference based on average NRS-11 score, percent pain relief, and subjective improvement (p<0.05, independent t-test).

Conclusion: Sciatic nerve decompression is effective in pain relief in chronic sciatica due to sciatic nerve entrapment at the greater sciatic notch. Its effect was further enhanced by circumferential dissection of the sciatic nerve based on the compartment formed by the piriformis muscle and the sacrotuberous ligament in the greater sciatic notch.

Keywords: Piriformis syndrome; Sacrotuberous ligament; Sciatic nerve; Sciatica.

Fig. 1.

Changes in the extent of decompression of the sciatic nerve pathway during transgluteal sciatic nerve decompression. A : Extent of decompression of the sciatic nerve pathway via conventional method (black-dotted line circle). B : Circumferential dissection of the sciatic nerve performed more proximally than in the conventional method to decompress the compartment (red-dotted circle) composed of the sacrotuberous ligament, piriformis muscle, and sciatic nerve. STL : sacrotuberous ligament, Pfm : piriformis muscle, SN : sciatic nerve, PN : pudendal nerve.

Fig. 2.

Circumferential decompression of the left sciatic nerve at the greater sciatic notch. A : Splitting of the gluteus maximus muscle (GMm) exposes the subgluteal fat layer (Sgf) and sacrotuberous ligament (STL). A dotted white line indicates the path of the lateral margin of STL overlying the proximal course of the piriformis muscle at the greater sciatic notch. B : Intraoperative image showing partial division of STL. The white arrow indicates resection of the lateral margin of the sacrotuberous ligament running over the piriformis muscle. C : Partial division of the sacrotuberous ligament and isolation of the proximal piriformis muscle from the sciatic nerve are shown. The tendon of the piriformis (white arrow) muscle compressing the sciatic nerve is identified. The black arrow shows the part of the sciatic nerve that is severely compressed. D : Resection of the piriformis muscle is initiated proximally below the lateral margin of the resected sacrotuberous ligament. E : Dissection of the distal tendon (white arrow) of the piriformis muscle transitioning into the greater trochanter. F : An intraoperative photograph showing the completion of the circumferential dissection and neurolysis of the sciatic nerve. Pfm : piriformis muscle of the remaining part after resection, SN : sciatic nerve, IGv : inferior gluteal vein, IGN : inferior gluteal nerve, PN : peroneal division of the sciatic nerve, TN : tibial division of the sciatic nerve, NGM : nerve to the gluteus maximus muscle, a branch of the inferior gluteal nerve.