#418 Retroperitoneal Oblique Window to the L2-S1 Intervertebral Discs in the Lateral Position: An Anatomic Study

General Session: Lateral Interbody Fusion

Presented by: T. Davis


T.T. Davis (1)
R. Hynes (2)
S. Spann (3)
M. MacMillan (4)
B. Kwon (5)
J. Liu (6)
F. Acosta (6)
T. Drochner (7)

(1) The Center for Spine and Joint Restoration, Santa Monica, CA, USA
(2) B.A.C.K. Center, Melbourne, FL, USA
(3) Westlake Orthopaedics and Spine, Austin, TX, USA
(4) University of Florida, Orthopaedics and Rehabilitation, Gainesville, FL, USA
(5) Tufts University School of Medicine, Orthopedic Surgery, Boston, MA, USA
(6) Cedars Sinai Medical Center, Los Angeles, CA, USA
(7) Medtronic Spine & Biologics, Memphis, TN, USA


Introduction: Access to the intervertebral discs from L2-S1 in one surgical position can be challenging. The lateral transpsoas minimally invasive surgical (MIS) approach is preferred by many surgeons due to the ease of access, decreased postoperative pain, decreased muscle disruption, decreased risk of vascular injury, and decreased recovery time. The transpsoas approach does however pose potential risk to neural structures of the lumbar plexus as they course through the psoas. The large psoas and overlap of the iliac crest limits access to the L4-5 disc in many patients.

Objective: The purpose of the study is to investigate a MIS oblique approach to the lumbar spine including L5-S1 while keeping the patient in a lateral decubitus position with minimal disruption of the psoas.

Methods: Nineteen fresh frozen cadaveric specimens (10 female, 9 male; 31-103 yrs; BMI 15.1-39.7) with peritoneal contents intact were dissected while in a right lateral decubitus position. An oblique anatomic window to access the L2-S1 discs was examined. Measurements were taken in a static state and then with mild retraction of the psoas. The access window was defined at L2-3, L3-4, and L4-5 as the left lateral border of the aorta (or iliac artery) and the anterior medial border of the psoas. The L5-S1 window of access was defined transversely from the mid-sagittal line of the inferior endplate of L5 to the medial border of the left common iliac vessel and vertically to the first vascular structure that crosses midline.

Results: The mean static/retracted access window was as follows; L2-3 = 17.7mm/24.5mm, L3-4 = 18.9mm/26.5mm, L4-5 = 14.3mm/23.6mm.The L5-S1 disc space means were 15.2mm between midline and left common iliac vessel, and 24.8mm from the first midline vessel to the inferior endplate of L5.

Conclusion: The MIS oblique window allows access to lumbar intervertebral discs including L5-S1 while keeping the patient in a lateral decubitus position. The oblique anatomic window was present at L2 to S1 on 18 of 19 specimens. Minimal psoas retraction without significant tendon disruption allowed for a generous window to the disc space. The L5-S1 disc space can be accessed from an oblique angle consistently with gentle retraction of the iliac vessels on the ipsilateral side of the approach. This study supports the potential of an MIS oblique retroperitoneal approach to the L2-S1 discs.