title: Posterior dynamic stabilization in the treatment of degenerative lumbar stenosis: validity of its rationale.
abstract: OBJECTIVE
  The authors undertook this study to investigate the validity of the rationale for posterior dynamic stabilization using the Device for Intervertebral Assisted Motion (DIAM) in the treatment of degenerative lumbar stenosis.
  
  
  METHODS
  A cohort of 31 patients who underwent single-level decompression and DIAM placement for degenerative lumbar stenosis were followed up for at least 2 years and data pertaining to their cases were analyzed prospectively. Of these patients, 7 had retrolisthesis. Preoperative and postoperative plain lumbar radiographs obtained in all patients and CT images obtained in 14 patients were analyzed. Posterior disc heights; range of motion (ROM) of proximal, distal, and implant segments; lordotic angles of implant segments; percentage of retrolisthesis; and cross-sectional area and heights of intervertebral foramina on CT sagittal images were analyzed. Clinical outcomes were evaluated using visual analog scale scores and Oswestry Disability Index scores.
  
  
  RESULTS
  The mean values for posterior disc height before surgery, at 1 week after surgery, and at the final follow-up visits were 6.4 ± 2.0 mm, 9.7 ± 2.8 mm, and 6.8 ± 2.5 mm, respectively. The mean lordotic angles at the implant levels before surgery, at 1 week after surgery, and at the final follow-up visits were 7.1° ± 3.3°, 4.1° ± 2.7°, and 7.0° ± 3.7°, respectively. No statistically significant difference was found between the preoperative values and values from final follow-up visits for posterior disc height and lordotic angles at implant levels (p = 0.17 and p = 0.10, respectively). There was no statistically significant difference between the preoperative and final follow-up visit values for intervertebral foramen cross-sectional area and heights on CT images. The ROMs of proximal and distal segments also showed no significant decrease (p = 0.98 and p = 0.92, respectively). However, the ROMs of implant segments decreased significantly (p = 0.02). The average 31.4-month improvement for all clinical outcome measures was significant (p < 0.001).
  
  
  CONCLUSIONS
  Based on radiological findings, the DIAM failed to show validity in terms of the rationale of indirect decompression, but it did restrict motion at the instrumented level without significant change in adjacent-segment ROM. The clinical condition of the patients, however, was improved, and improvement was maintained despite progressive loss of posterior disc height after surgery.
authors.affiliation: Department of Orthopaedic Surgery, College of Medicine, The Catholic University of Korea, Seoul, Korea. kyh@catholic.ac.kr
authors.forename: Kee-Yong
authors.initials: KY
authors.lastname: Ha
authors.forename: Jun-Yeong
authors.initials: JY
authors.lastname: Seo
authors.forename: Soon-Eok
authors.initials: SE
authors.lastname: Kwon
authors.forename: Il-Nam
authors.initials: IN
authors.lastname: Son
authors.forename: Ki-Won
authors.initials: KW
authors.lastname: Kim
authors.forename: Young-Hoon
authors.initials: YH
authors.lastname: Kim
mesh_terms: D000368:Aged; D019299:Decompression, Surgical; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology; D013123:Spinal Fusion / Q000379:methods*; D013130:Spinal Stenosis / Q000000981:diagnostic imaging / Q000601:surgery*; D016896:Treatment Outcome