Deep gluteal space problems: piriformis syndrome, ischiofemoral impingement and sciatic nerve release

Abstract

Background: Deep gluteal syndrome (DGS) is an underdiagnosed entity characterized by pain and/or dysesthesias in the buttock area, hip or posterior thigh and/or radicular pain due to a non-discogenic sciatic nerve entrapment in the subgluteal space. Multiple pathologies have been incorporated in this all-included "piriformis syndrome", a term that has nothing to do with the presence of fibrous bands, obturator internus/gemellus syndrome, quadratus femoris/ischiofemoral pathology, hamstring conditions, gluteal disorders and orthopedic causes.

Methods: This article describes the subgluteal space anatomy, reviews known and new etiologies of DGS, and assesses the role of the radiologist and orthopaedic surgeons in the diagnosis, treatment and postoperative evaluation of sciatic nerve entrapments.

Conclusion: DGS is an under-recognized and multifactorial pathology. The development of periarticular hip endoscopy has led to an understanding of the pathophysiological mechanisms underlying piriformis syndrome, which has supported its further classification. The whole sciatic nerve trajectory in the deep gluteal space can be addressed by an endoscopic surgical technique. Endoscopic decompression of the sciatic nerve appears useful in improving function and diminishing hip pain in sciatic nerve entrapments, but requires significant experience and familiarity with the gross and endoscopic anatomy.

Level of evidence: IV.

Keywords: deep gluteal syndrome; hip arthroscopy; hip endoscopy; ischiofemoral impingement; piriformis syndrome; sciatic nerve entrapment.

Figure 1

Normal anatomy of the subgluteal space. The diagram illustrates the main bone, ligament, muscle and tendon structures located in subgluteal space in a back view. SP sacral plexus, SN sciatic nerve, STL sacrotuberous ligament, P piriformis muscle, SG superior gemellus muscle, OI obturator internus muscle, IG inferior gemellus muscle (Reprint with permission from19).

Figure 2

a–f. Anatomic variations of the relationship between the piriformis muscle and sciatic nerve. Diagrams illustrate the six variants, originally described by Beaton and Anson. (a) An undivided nerve comes out below the piriformis muscle (normal course). (b) A divided sciatic nerve passing through and below the piriformis muscle. (c) A divided nerve passing above and below an undivided muscle. (d) An undivided sciatic nerve passing through the piriformis muscle. (e) A divided nerve passing through and above the muscle heads. (f) Diagram showing an unreported additional B-type variation consisting of a smaller accessory piriformis (AP) with its own separate tendon. SN sciatic nerve, P piriformis muscle, SG superior gemellus muscle (Reprint with permission from19).

Figure 3 a, b

Endoscopic view showing the pathogenic mechanism of DGS. (a) Edematous and flattened sciatic nerve due to fibrovascular entrapment in a patient with ischemic neuritis. (b) Normal vascularization recovery after nerve neurolysis (Reprint with permission from19).

Figure 4 a–e

Pathogenic classification of fibrous/fibrovascular bands. (a, b) Compressive or bridge-type bands limiting the movement of the sciatic nerve from anterior to posterior (type 1A) or from posterior to anterior (type 1B). (c, d) Adhesive or horse-strap bands (type 2), which bind strongly to the sciatic nerve structure, anchoring it in a single direction. They can be attached to the sciatic nerve laterally (type 2A) or medially (type 2B). (e) Bands anchored to the sciatic nerve with undefined distribution (type 3) (Reprint with permission from19).

Figure 5

Left hip. Endoscopic view of type-3 scarred bands in a 51-year-old female with DGS. SN Sciatic nerve, PS Piriformis scar, FB Fibrous bands.

Figure 6

Left hip. The endoscopic image shows the sciatic nerve decompression, more complex when this type of bands are resected. SN Sciatic nerve, FB Fibrous bands with undefined distribution (Type 3).

Figure 7

Right hip: Endoscopic image shows a severe degenerative calcifying tendinopathy of hamstring tendons with reactive sciatic neuritis. tc Calcifying tendinopathy, HT Hamstring tendons, SN Sciatic nerve.

Figure 8

Right hip. Entering at vastus lateralis ridge avoids inadvertent deep penetration of vastus lateralis or gluteus medius muscle.

Figure 9

Left gluteal region showing portal placement for subgluteal endoscopy. (1) Midanterior portal (2) Distal anterolateral accessory portal (3) Anterolateral portal (4) Posterolateral portal (5) Auxiliary posterolateral portal placement.

Figure 10

Endoscopic view right hip. Visualizing through the peritrochanteric portal, the examination begins at the gluteus maximus insertion at the linea aspera. (a) Gluteus maximus insertion; (b) Vastus lateralis.

Figure 11

Left hip. Normal sciatic nerve with noticeable epineural blood flow.

Figure 12

Left hip. Sciatic nerve at the sciatic notch. a) Piriformis tendon after release; b) fibrovascular band, SG Superior gemellus muscle, SN Sciatic nerve.

Figure 13

Left hip. Endoscopic view of obturator splitting the sciatic nerve.

Figure 14

Fluoroscopic view showing location of the scope and instruments in the subgluteal space. Radiofrequency probe at the sciatic notch.

Figure 15

Left hip. Intraoperative endoscopic image showing resection of the lesser trochanter with a 5.5 mm burr. LT Lesser trochanter.

Figure 16

Left hip. Transquadratus endoscopic treatment of isquiofemoral impingement. The aim of the osteoplasty of the posterior one third of the lesser trochanter is to obtain an isquiofemoral space of at least 17 mm leaving non-impingement bone and the iliopsoas insertion intact. Radiofrecuency probe measuring the distance. SN Sciatic nerve LT Lesser trochanter after osteoplasty.