title: Does pre-existing L5-S1 degeneration affect outcomes after isolated L4-5 fusion for spondylolisthesis?
abstract: BACKGROUND
  Concerns have been raised regarding residual symptoms of caudal segment (L5-S1) degeneration that may affect clinical outcomes or require additional surgery after isolated L4-5 fusion, especially if there is pre-existing L5-S1 degeneration. This study aimed to evaluate the L5-S1 segment after minimally invasive lumbar interbody fusion at the L4-5 segment, as well as the influence of pre-existing L5-S1 degeneration on radiologic and clinical outcomes.
  
  
  METHODS
  This retrospective study evaluated patients with isthmic spondylolisthesis and degenerative spondylolisthesis who underwent mini-open anterior lumbar interbody fusion with percutaneous pedicle screw fixation (PSF) or minimally invasive transforaminal interbody fusion with PSF at the L4-5 segment. The minimum follow-up period was 7 years, and radiographic evaluations were conducted via magnetic resonance imaging, computed tomography, and plain radiography at the 5-year follow-up. Clinical outcomes were assessed using the Visual Analog Score, Oswestry Disability Index, and surgical satisfaction rate. Patients were divided into two groups, those with and without pre-existing L5-S1 degeneration, and their final outcomes and incidence of radiographic and clinical adjacent segment disease (ASD) were compared.
  
  
  RESULTS
  Among 70 patients who underwent the procedures at our institution, 12 (17.1%) were lost to follow-up. Therefore, this study evaluated 58 patients, with a mean follow-up period of 9.4 ± 2.1 years. Among these patients, 22 patients had pre-existing L5-S1 degeneration, while 36 patients did not have pre-existing L5-S1 segmental degeneration. There were no significant differences in the clinical outcomes at the final follow-up when the two groups were compared. However, radiographic ASD at L5-S1 occurred in seven patients (12.1%), clinical ASD at L5-S1 occurred in three patients (5.2%), and one patient (1.7%) required surgery. In the group with pre-existing degeneration, L5-S1 degeneration was radiographically accelerated in four patients (18.2%) and clinical ASD developed in one patient (4.5%). In the group without pre-existing degeneration, L5-S1 degeneration was radiographically accelerated in three patients (8.3%) and clinical ASD developed in two patients (5.7%). There were no differences in the incidence of ASD when we compared the two groups.
  
  
  CONCLUSIONS
  Pre-existing L5-S1 degeneration does not affect clinical and radiographical outcomes after isolated L4-5 fusion.
authors.affiliation: Department of Neurosurgery, The Leon Wiltse Memorial Hospital, Anyang, Korea. chul5104@hanmail.net.
authors.forename: Kyung-Chul
authors.initials: KC
authors.lastname: Choi
authors.affiliation: Department of Neurosurgery, Prime Hospital, Busan, Korea. leoshk1@naver.com.
authors.forename: Hyeong-Ki
authors.initials: HK
authors.lastname: Shim
authors.affiliation: Department of Neurosurgery, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, 222 Banpo Daero Seocho-gu, 137-701, Seoul, Korea. mddavidk@dreamwiz.com.
authors.forename: Jin-Sung
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Wooridul Spine Hospital, Seoul, Korea. shlee@wooridul.co.kr.
authors.forename: Sang-Ho
authors.initials: SH
authors.lastname: Lee
mesh_terms: D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012447:Sacrum / Q000473:pathology; D013123:Spinal Fusion / Q000009:adverse effects*; D013168:Spondylolisthesis / Q000150:complications / Q000601:surgery*; D016896:Treatment Outcome