title: Posterolateral versus circumferential instrumented fusion for monosegmental lumbar degenerative disc disease using an expandable cage.
abstract: BACKGROUND
  Theoretically, 360° instrumented fusion has been considered to offer better radiological correction than PLF. Despite numerous publications, this correlation is still weak with several controversies in the relative literature.
  
  
  OBJECTIVE
  This prospective randomized study was designed to compare the radiological segmental results, complications and outcome of 360° instrumented fusion with the use of a single diagonal expandable PLIF device versus posterolateral pedicle screw fixation in monosegmental lumbar DDD and to show that the use of an novel expandable cage is associated with low PLIF-related complication rate compared to conventional cages reported previously.
  
  
  METHODS
  Prospective randomized controlled clinical and radiological study.
  
  
  METHODS
  Adults who suffered from monosegmental DDD were eligible for enrolment in this trial. We randomly assigned 150 patients to receive either 360° instrumented fusion (group A) with expandable cage or PLF (group B).
  
  
  METHODS
  Differences between the two groups regarding clinical parameters and radiographic sagittal measurements after 36 months of follow-up.
  
  
  METHODS
  The record included global [T12-S1 lordosis, sagittal global spinal balance (SB) (C7-mid-femoral axis)] and segmental [segmental disc wedging (SDW), anterior (ADHr) and posterior (PDHr) disc height ratio] radiological measurements at the instrumented segment. Additionally, clinical outcome was evaluated with VAS, SF-36 (Physical function and Bodily Pain) and ODI questionnaires. Fusion was evaluated with the use of Christiansen method.
  
  
  RESULTS
  In 73 and 72 participants of group A and B, respectively, who completed follow-up to 36 months, there were no differences with respect to the rate of improvement in SF-36, ODI and VAS scores. However, in the spines of group A, there was a significant increase in anterior disc height ratio (P = 0.0057), posterior disc height (P = 0.016) and segmental disc wedging (P = 0.00021) without subsequent loss of correction. Fusion rate was radiologically shown in 94.5% and 87% spines of group A and B, respectively (P > 0.2). Four and 9 spines in group A and B, respectively, showed non-union at the final observation.
  
  
  CONCLUSIONS
  Our findings suggest that 360° fusion offers better sagittal radiological restoration associated with circumferential fusion. However, this difference seemed not to have any medium-term clinical impact. The use of expandable cage was associated with low PLIF-related complications compared to conventional cages.
authors.affiliation: Orthopaedic Department, General Hospital 'Agios Andreas', 1 Tsertidou str, 26224, Patras, Greece. korovess@otenet.gr.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Korovessis
authors.affiliation: Orthopaedic Department, General Hospital 'Agios Andreas', 1 Tsertidou str, 26224, Patras, Greece.
authors.forename: Thomas
authors.initials: T
authors.lastname: Repantis
authors.affiliation: Orthopaedic Department, General Hospital of Messolonghi, Messolonghi, Greece.
authors.forename: Andreas
authors.initials: A
authors.lastname: Baikousis
authors.affiliation: Radiology Department, General Hospital 'Agios Andreas' Patras, Patras, Greece.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Iliopoulos
keywords: B-twin; Circumferential fusion; Degenerative lumbar disease; PLIF