Para-muscular and trans-muscular approaches to the lumbar inter-vertebral foramen: an anatomical comparison

Abstract

-Foraminal and extra-foraminal disc herniations comprise up to 11.7% of all lumbar disc herniations. Facetectomy, which had been the classic approach, is now recognized as cause of pain and instability after surgery. Otherwise, posterior lateral approaches through a trans-muscular or a para-muscular technique offer no significant damage to key structures for spinal stability. The surgical anatomy of these approaches has already been described, but they were not compared. In order to quantify the angle of vision towards the intervertebral foramen offered by each technique, 12 fresh cadavers were dissected and studied regarding these approaches. The angle presented by trans-muscular approach was wider in all studied lumbar levels. Surgery through the trans-muscular approach is performed with a better working angle, requiring a smaller resection of surrounding tissues. Therefore, minor surgical trauma can be expected. Our measurements support previously published data that point the trans-muscular approach as the best surgical option.KEY WORDS: intervertebral disc displacement, low back pain, lumbar vertebrae, sciatica, comparative study.Acessos paramuscular e transmuscular ao forame intervertebral lombar: comparação anatômica RESUMO -As hérnias de disco lombares apresentam-se como foraminais ou extra-foraminais em até 11,7% dos casos. Seu tratamento cirúrgico através de facetectomias pode causar dor e instabilidade, o que não ocorre com a utilização de acessos cirúrgicos posteriores laterais ao canal central, quer seja por via transmuscular ou paramuscular. Nosso objetivo foi comparar o ângulo de trabalho relativo ao forame intervertebral permitido por cada via e avaliar possíveis implicações cirúrgicas. Dissecções e medidas realizadas em doze cadáveres frescos demonstraram que este ângulo é maior na via transmuscular em todos os níveis lombares estudados. Dado que um ângulo mais favorável permite uma ressecção menor das estruturas envolvidas para que se estabeleça o campo de trabalho, a cirurgia por meio da via transmuscular permitirá, então, um trauma cirúrgico menor. Nossos resultados corroboram publicações prévias que apontam a via transmuscular como a melhor opção cirúrgica. PALAVRAS-CHAVE: deslocamento do disco intervertebral, dor lombar, vértebras lombares, ciática, estudo comparativo.Foraminal and extra-foraminal lumbar disc herniations have historically been a challenge in spine surgery due to their particular anatomical relationship with the nerve roots and the facet joints, comprising up to 11.7% of all lumbar disc herniations 1,2 . Facetectomy used to be the standard technique in treating such herniations for a long time 1,3,4,5 . Despite the familiar surgical anatomy and the success in relieving root compression in most of the cases, this approach has been reviewed and criticized. The incidence of back pain after surgery, related to instability, is significant, as pointed out by several authors [6][7][8][9][10]