title: How does spinal canal decompression and dorsal stabilization affect segmental mobility? A biomechanical study.
abstract: BACKGROUND
  When decompression of the lumbar spinal canal is performed, segmental stability might be affected. Exactly which anatomical structures can thereby be resected without interfering with stability, and when, respectively how, additional stabilization is essential, has not been adequately investigated so far. The present investigation describes kinetic changes in a surgically treated motion segment as well as in its adjacent segments.
  
  
  METHODS
  Segmental biomechanical examination of nine human lumbar cadaver spines (L1 to L5) was performed without preload in a spine-testing apparatus by means of a precise, ultrasound-guided measuring system. Thus, samples consisting of four free motion segments were made available. Besides measurements in the native (untreated) spine specimen further measurements were done after progressive resection of dorsal elements like lig. flavum, hemilaminectomy, laminectomy and facetectomy. The segment was then stabilised by means of a rigid system (ART((R))) and by means of a dynamic, transpedicularly fixed system (Dynesys((R))).
  
  
  RESULTS
  For the analysis, range of motion (ROM) values and separately viewed data of the respective direction of motion were considered in equal measure. A very high reproducibility of the individual measurements could be verified. In the sagittal and frontal plane, flavectomy and hemilaminectomy did not achieve any relevant change in the ROM in both directions. This applies to the segment operated on as well as to the adjacent segments examined. Resection of the facet likewise does not lead to any distinct increase of mobility in the operated segment as far as flexion and right/left bending is concerned. In extension a striking increase in mobility of more than 1degree compared to the native value can be perceived in the operated segment. Stabilization with the rigid and dynamic system effect an almost equal reduction of flexion/extension and right/left bending. In the adjacent segments, a slightly higher mobility is to be noted for rigid stabilization than for dynamic stabilisation. A linear regression analysis shows that in flexion/extension monosegmental rigid stabilisation is compensated predominantly in the first cranial adjacent segment. In case of a dynamic stabilisation the compensation is distributed among the first and second cranial, and by 20% in the caudal adjacent segment.
  
  
  CONCLUSIONS
  Monosegmental decompression of the lumbar spinal canal does not essentially destabilise the motion segment during in vitro conditions. Regarding rigid or dynamic stabilisation, the ROM does not differ within the operated segment, but the distribution of the compensatory movement is different.
authors: Department of Orthopaedic and Trauma Surgery, Cologne University, Joseph-Stelzmann Street 9, 50924 Cologne, Germany. stefan.delank@uk-koeln.de
authors: Karl-Stefan
authors: KS
authors: Delank
authors: Erol
authors: E
authors: Gercek
authors: Sebastian
authors: S
authors: Kuhn
authors: Frank
authors: F
authors: Hartmann
authors: H
authors: H
authors: Hely
authors: Marc
authors: M
authors: Röllinghoff
authors: M A
authors: MA
authors: Rothschild
authors: H
authors: H
authors: Stützer
authors: Rolf
authors: R
authors: Sobottke
authors: Peer
authors: P
authors: Eysel
mesh_terms: D001696:Biomechanical Phenomena; D002102:Cadaver; D019299:Decompression, Surgical; D006801:Humans; D007593:Joint Instability / Q000209:etiology; D007796:Laminectomy / Q000009:adverse effects*; D017843:Ligamentum Flavum / Q000601:surgery; D008159:Lumbar Vertebrae / Q000601:surgery*; D013115:Spinal Canal / Q000601:surgery*; D013123:Spinal Fusion; D021801:Zygapophyseal Joint / Q000601:surgery