title: Posterior lumbar interbody fusion for lytic spondylolisthesis: restoration of sagittal balance using insert-and-rotate interbody spacers.
abstract: BACKGROUND
  The role of surgical correction of sagittal plane deformity in cases of lytic spondylolisthesis remains controversial. While some early evidence is emerging of the possible short- and long-term benefits of restoring spinal balance, many surgeons have been concerned about the associated risks. The insert-and-rotate posterior lumbar interbody fusion (PLIF) technique, first described by Jaslow in 1946, may enable surgeons to safely and effectively correct sagittal balance through a single posterior approach.
  
  
  OBJECTIVE
  To determine whether the focal kyphosis and subluxation associated with a lytic lumbosacral spondylolisthesis can be safely and effectively corrected using a single-stage posterior distraction/reduction technique and insert-and-rotate interbody fusion spacers.
  
  
  METHODS
  A prospective, single cohort, observational study of the clinical outcomes and retrospective radiological review, in a series of 18 consecutive patients with lytic spondylolisthesis Grades I to IV, operated between September 2000 and December 2002.
  
  
  METHODS
  Mean age of 50.2 years (range, 15.5 to 77.8 years). Principal indication for surgery was relief of radicular pain secondary to foraminal stenosis in 16 of 18 patients, and back pain was the principal symptom in 2 patients. Mean preoperative slip was 30.2% (range, 9% to 78%). Mean preoperative focal lordosis was 10.6 degrees (range, -12 to 33 degrees).
  
  
  METHODS
  Minimum 12-month follow-up was available on all patients except one, who died of unrelated causes after his 6-month visit. Patients completed Visual Analogue Pain Score (VAS), Low Back Outcome Score (LBOS), Short Form (SF)-12 and patient satisfaction questionnaires. Pre- and postoperative measurements of the percentage slip and lumbar lordosis of the involved segments were available on 13 patients. SURGICAL METHODS: Decompressive laminectomy was followed by reduction of the spondylolisthesis with the aid of intervertebral disc space spreaders and supplementary pedicle screw instrumentation. The vertebral bodies were supported with bilateral intervertebral lordotic spacers made from carbon fiber, titanium mesh or polyether-ether-ketone (Medtronic Sofamor Danek, Memphis, TN). These were inserted on their sides and rotated 90 degrees before placing bone graft to either side of them, within the disc space.
  
  
  RESULTS
  Mean follow-up was 17.3 months. Mean preoperative measures of VAS and LBOS of 5.0+/-2.3 and 29.3+/-16.4, respectively, improved to 2.9+/-3.0 (p=.01) and 42.6+/-20.1 (p=.005) at last follow-up. Fifteen of 18 patients (83.3%) considered their outcome to be good or excellent. Mean preoperative slip reduced from 30.2% to 6.2% (p=.001). Mean focal lordosis improved from 10.6 to 18.1 degrees (p=.02). Lumbar lordosis (L1-S1) did not change, but the lordosis of the lumbar segments above the fusion reduced from 46.8 to 34.9 degrees (p=.02). There were no serious implant or procedural complications. Postoperatively, there was a delayed and temporary weakness of ankle dorsiflexion in a patient with Grade IV spondylolisthesis.
  
  
  CONCLUSIONS
  This series suggests that PLIF using an insert-and-rotate technique can yield satisfactory clinical outcomes and substantial deformity correction using a posterior only approach and with low levels of serious or permanent complications. Longer-term clinical outcome and comparative studies are required regarding the importance of the restoration of spinal balance.
authors.affiliation: Department of Neurosurgery, Royal North Shore Hospital, Pacific Highway, St. Leonards, NSW 2065, Australia. thesears@bigpond.com
authors.forename: William
authors.initials: W
authors.lastname: Sears
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019299:Decompression, Surgical / Q000379:methods*; D005260:Female; D006304:Health Status; D006801:Humans; D016268:Internal Fixators; D007796:Laminectomy; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D020127:Recovery of Function; D013121:Spinal Curvatures / Q000209:etiology / Q000503:physiopathology / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013168:Spondylolisthesis / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D011795:Surveys and Questionnaires