Archives

  • 2018-07
  • 2018-10
  • 2018-11
  • 2019-04
  • 2019-05
  • 2019-06
  • 2019-07
  • 2019-08
  • 2019-09
  • 2019-10
  • 2019-11
  • 2019-12
  • 2020-01
  • 2020-02
  • 2020-03
  • 2020-04
  • 2020-05
  • 2020-06
  • 2020-07
  • 2020-08
  • 2020-09
  • 2020-10
  • 2020-11
  • 2020-12
  • 2021-01
  • 2021-02
  • 2021-03
  • 2021-04
  • 2021-05
  • 2021-06
  • 2021-07
  • 2021-08
  • 2021-09
  • 2021-10
  • 2021-11
  • 2021-12
  • 2022-01
  • 2022-02
  • 2022-03
  • 2022-04
  • 2022-05
  • 2022-06
  • 2022-07
  • 2022-08
  • 2022-09
  • 2022-10
  • 2022-11
  • 2022-12
  • 2023-01
  • 2023-02
  • 2023-03
  • 2023-04
  • 2023-05
  • 2023-06
  • 2023-07
  • 2023-08
  • 2023-09
  • 2023-10
  • 2023-11
  • 2023-12
  • 2024-01
  • 2024-02
  • 2024-03
  • 2024-04

    • The lateral lumbar spinal canal may be

    2018-10-25

    The lateral lumbar spinal canal may be subdivided into the subarticular (lateral recess), the foraminal (pedicle) and the extraforaminal (far lateral) zone. Within these regions lies the “hidden zone”, an area known for its difficult surgical exposure (A) (). Common pathologies of this region include foraminal osseous stenosis (narrowing of the foramen through which the nerve root exits the spinal canal) as well as disc herniations. It has been estimated that roughly 10–20% of all disc herniations migrate in a craniolateral direction and may hence be located in the preforaminal and foraminal regions of the “hidden zone”. Due to the local anatomy, these lesions may affect both the traversing (level below) as well as the exiting (same level) nerve root. Patients typically present with neurological symptoms of (poly-)radiculopathy, including pain, weakness and numbness. Commonly, and in hmg-coa reductase inhibitors to the above-mentioned zones, all types of disc herniations that affect the exiting nerve root at the same level are referred to as “far- or extreme-lateral”, including pre-, intra- and extra-foraminal herniations. Whilst a variety of effective techniques for approaching extraforaminal and purely intraforaminal lesions have been developed, there continues to be disagreement with regard to the optimal approach to lesions located in the pre- and intra-foraminal regions of the hidden zone. In order to understand this discord, it is crucial to comprehend the difficulties and patient-specific concerns associated with the surgical exposure of this region. Anatomically, the medial hidden zone is an area bordered laterally by the pedicle, ventrally by the dorsal part of the vertebral body and covered dorsally by the pars interarticularis of the hemilamina (A). Open surgical exploration of this region via the traditional interlaminar route (B) is therefore only possible after at least partial removal of the ipsilateral hemilamina (extended laminotomy or even hemilaminectomy) and may additionally require partial or complete facetectomy (removal of the facet joint) (). Extended laminotomy as a means to approach the hidden zone has therefore lost popularity, since the associated removal of biomechanically important bony structures has been suggested to increase the risk of secondary segmental instability () and may subsequently necessitate fusion surgery. Other, more lateral approaches have been suggested; however, these require specific anatomical knowledge, and offer inferior access to more medial spinal pathologies of the hidden zone. In 1998, proposed a less invasive direct procedure by utilizing a translaminar approach (TLA) through a fenestration of the pars interarticularis, thus circumventing facetectomy or hemilaminectomy in many cases (C). The increasing availability of high-definition imaging modalities (MRI, CT) has contributed to the growing popularity of the TLA, since identifying the exact location and extent of the spinal lesion is crucial for surgical planning to limit unnecessary biomechanical damage and prevent intraoperative conversion to conventional approaches. In recent years, several studies have demonstrated the feasibility, safety and efficacy of this technique to successfully treat disc herniations affecting the foraminal and preforaminal regions. Endoscopic approaches to the hidden zone have been suggested, including endoscopic transforaminal (D) or translaminar techniques (). However, whilst the endoscopic TLA might offer an incremental improvement with regard to trauma, transforaminal endoscopic procedures are not recommended for the more medial foraminal lesions of the hidden zone due to imposed spatial restrictions, especially in the lower lumbar levels. Consequently, endoscopic transforaminal approaches to these pathologies have been associated with increased operating times as well as higher complication and revision rates (). Nevertheless, even though the TLA seems to be the method of choice to approach craniolateral disc herniations, some authors have argued that this technique also has its limitations. Due to segment-dependent changes of vertebral anatomy, Di Lorenzo\'s approach must be located very laterally in the more upper lumbar levels in order to reach the medial hidden zone. Disruption of the lateral hemilamina (pars interarticularis), however, has been linked to an increased risk of stress fracture and instability (). This becomes more relevant as the relative risk of cranial disc sequestration increases significantly in higher lumbar levels and cranial sequestration is strongly correlated with increased age (). Since older patients are also more likely to suffer from osteoporosis and degenerative spinal disorders such as facet joint hypertrophy, which may manifest segmental instability, less invasive medial approaches to the hidden zone are warranted.