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[Indentification of lumbar foramina with percutaneous pins. A cadaveric study].

INTRODUCTION
Patients diagnosed with a lumbar disc hernia and nerve root compression, in which conservative treatment failed are candidates for lumbar discectomy. This technique often results in failed spine surgery syndrome which includes different complications such as arachnoiditis, discitis, and sac tears resulting in pain and neurological deficit. This has led to research of minimally invasive surgery in which the medullary canal is not involved and is performed under local anesthesia. In order to perform this technique, the anatomical and radiological identification of the intervertebral foramina is necessary. Kambin's triangle is an anatomical safe place for percutaneous procedures.


OBJECTIVES
(1) To identify Kambin's triangle in the cadaver and its anatomical elements. (2) To describe the relationship between cutaneous lines traced on the patient with the anatomic elements in the cadaver by using guide needles. (3) To describe the position of the surgical instruments used in a posterolateral discectomy approach to identify the triangle.


METHODS
(1) Dissection through a standard approach to L1-L5 foramina. (2) Observation of the anatomic planes that the guide needle follows. (3) Radiological study of the foramen. (4) Positioning of the surgical instruments on the foramen to establish the size and space.


RESULTS
(1) The intervertebral foramina were dissected and the anatomical components of Kambin's triangle were identified, also we compared size of this triangle (10 mm) and compared it with surgical instruments (7 mm). (2) Skin lines were tested as reliable and safe routes to identify foramina. (3) We proved safety of endoscopic surgery instruments by a posterolateral approach. (4) A visual aid was developed for adequate placement of the guide needle through the foramen.


CONCLUSIONS
(1) Foramina need to be perfectly identified with image techniques so that the surgical instruments can be placed safely. (2) Skin lines are a safe and reliable guide. (3) The technique is safe if performed through Kambin's triangle.