title: Sagittal Plane Correction Using the Lateral Transpsoas Approach: A Biomechanical Study on the Effect of Cage Angle and Surgical Technique on Segmental Lordosis.
abstract: METHODS
  Cadaveric biomechanical study.
  
  
  OBJECTIVE
  To determine the degree of segmental correction that can be achieved through lateral transpsoas approach by varying cage angle and adding anterior longitudinal ligament (ALL) release and posterior element resection.
  
  
  BACKGROUND
  Lordotic cage insertion through the lateral transpsoas approach is being used increasingly for restoration of sagittal alignment. However, the degree of correction achieved by varying cage angle and ALL release and posterior element resection is not well defined.
  
  
  METHODS
  Thirteen lumbar motion segments between L1 and L5 were dissected into single motion segments. Segmental angles and disk heights were measured under both 50 N and 500 N compressive loads under the following conditions: intact specimen, discectomy (collapsed disk simulation), insertion of parallel cage, 10° cage, 30° cage with ALL release, 30° cage with ALL release and spinous process (SP) resection, 30° cage with ALL release, SP resection, facetectomy, and compression with pedicle screws.
  
  
  RESULTS
  Segmental lordosis was not increased by either parallel or 10° cages as compared with intact disks, and contributed small amounts of lordosis when compared with the collapsed disk condition. Placement of 30° cages with ALL release increased segmental lordosis by 10.5°. Adding SP resection increased lordosis to 12.4°. Facetectomy and compression with pedicle screws further increased lordosis to approximately 26°. No interventions resulted in a decrease in either anterior or posterior disk height.
  
  
  CONCLUSIONS
  Insertion of a parallel or 10° cage has little effect on lordosis. A 30° cage insertion with ALL release resulted in a modest increase in lordosis (10.5°). The addition of SP resection and facetectomy was needed to obtain a larger amount of correction (26°). None of the cages, including the 30° lordotic cage, caused a decrease in posterior disk height suggesting hyperlordotic cages do not cause foraminal stenosis.
  
  
  METHODS
  N/A.
authors.affiliation: Department of Orthopedic Surgery, Emory University, Veterans Affairs Medical Center Atlanta, Atlanta, GA.
authors.forename: Rojeh
authors.initials: R
authors.lastname: Melikian
authors.affiliation: Department of Orthopedic Surgery, Emory University, Veterans Affairs Medical Center Atlanta, Atlanta, GA.
authors.forename: Sangwook Tim
authors.initials: ST
authors.lastname: Yoon
authors.affiliation: Department of Orthopedic Surgery, Emory University, Veterans Affairs Medical Center Atlanta, Atlanta, GA.
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Orthopedic Surgery, Daejeon Veterans Hospital, Daejeon, Korea.
authors.forename: Kun Young
authors.initials: KY
authors.lastname: Park
authors.affiliation: Department of Orthopedic Surgery, Emory University, Veterans Affairs Medical Center Atlanta, Atlanta, GA.
authors.forename: Caroline
authors.initials: C
authors.lastname: Yoon
authors.affiliation: Department of Orthopedic Surgery, Emory University, Veterans Affairs Medical Center Atlanta, Atlanta, GA.
authors.forename: William
authors.initials: W
authors.lastname: Hutton
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery*; D017846:Longitudinal Ligaments / Q000601:surgery*; D008141:Lordosis / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008161:Lumbosacral Region / Q000601:surgery; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000295:instrumentation / Q000379:methods; D065289:Pedicle Screws; D013123:Spinal Fusion / Q000379:methods; D016896:Treatment Outcome