title: Lumbar clinical adjacent segment pathology: predilection for proximal levels.
abstract: METHODS
  Retrospective case series.
  
  
  OBJECTIVE
  To evaluate reoperations for lumbar adjacent segment pathology (ASP) during a 10-year period.
  
  
  BACKGROUND
  ASP after lumbar arthrodesis is an important clinical problem. There remains controversy, however, on the distribution of the most commonly affected levels.
  
  
  METHODS
  Thirty-one patients undergoing revision operation for ASP in the lumbar spine were included in this study. Patients' charts were evaluated for demographic data including age at index and revision operations, time to revision operation, and index and revision levels fused.
  
  
  RESULTS
  L4-L5 was the most commonly instrumented level in both single-level (n = 12), and multilevel (n = 13) index fusions. The mean length of time from the index operation to revision surgery was 81 months (range, 11-570 mo). Kaplan-Meier analysis predicted a disease-free survival rate of 32.3% at 5 years and of 12.9% at 10 years after the index operation. L3-L4 was the most commonly affected level by ASP with 75% (16/20) requiring reoperation. L2-L3 was the next most commonly affected level at 52% (14/27). The L5-S1 disk was relatively protected from ASP, with only 4/17 (24%) disks at risk developing ASP. A subgroup analysis of patients undergoing revision after a single-level L4-L5 arthrodesis revealed ASP at L3-L4 in 83% (10/12) of patients, compared with only 3/12 (25%) at L5-S1 (P < 0.05). Of all cases of ASP, the proximal segments were involved 90% of the time.
  
  
  CONCLUSIONS
  ASP most commonly affects proximal levels in the lumbar spine. In this cohort of patients undergoing revision fusion for ASP, 90% of affected levels were rostral to the index level(s). In patients undergoing L4-L5 single-level arthrodesis, L3-L4 is at high risk, whereas L5-S1 is somewhat protected. Surgeons should pay particular attention to proximal levels when planning a lumbar arthrodesis, however, motion segments distal to fusion may not be as protected as previously thought.
  
  
  METHODS
  4.
authors.affiliation: *Norton Leatherman Spine Center, Louisville, KY †UCLA Department of Orthopaedic Surgery, Los Angeles, CA; and ‡USC Spine Center, Los Angeles, CA.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Celestre
authors.forename: Scott R
authors.initials: SR
authors.lastname: Montgomery
authors.forename: Asher I
authors.initials: AI
authors.lastname: Kupperman
authors.forename: Bayan
authors.initials: B
authors.lastname: Aghdasi
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Inoue
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Wang
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001174:Arthrodesis / Q000009:adverse effects* / Q000639:trends; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis* / Q000453:epidemiology; D012086:Reoperation / Q000639:trends; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000009:adverse effects* / Q000639:trends; D055009:Spondylosis / Q000175:diagnosis / Q000453:epidemiology / Q000601:surgery*