title: Relation between radiological assessment and biomechanical stability of lumbar interbody fusion in a large animal model.
abstract: OBJECTIVE
  To relate the progress of vertebral segmental stability after interbody fusion surgery with radiological assessment of spinal fusion.
  
  
  METHODS
  Twenty goats received double-level interbody fusion and were followed for a period of 3, 6 and 12 months. After killing, interbody fusion was assessed radiographically by two independent observers. Subsequently, the lumbar spines were subjected to four-point bending and rotational deformation, assessed with an optoelectronic 3D movement registration system. In addition, four caprine lumbar spines were analysed in both the native situation and after the insertion of a cage device, as to mimic the direct post-surgical situation. The range of motion (ROM) in flexion/extension, lateral bending and axial rotation was analysed ex vivo using a multi-segment testing system.
  
  
  RESULTS
  Significant reduction in ROM in the operated segments was already achieved with moderate bone ingrowth in flexion/extension (71 % reduction in ROM) and with only limited bone ingrowth in lateral bending (71 % reduction in ROM) compared to the post-surgical situation. The presence of a sentinel sign always resulted in a stable vertebral segment in both flexion/extension and lateral bending. For axial rotation, the ROM was already limited in both native and cage inserted situations, resulting in non-significant differences for all radiographic scores.
  
  
  CONCLUSIONS
  In vivo vertebral segment stability, defined as a significant reduction in ROM, is achieved in an early stage of spinal fusion, well before a radiological bony fusion between the vertebrae can be observed. Therefore, plain radiography underestimates vertebral segment stability.
authors.affiliation: Department of Orthopaedic Surgery, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands, rjkroeze@yahoo.com.
authors.forename: R J
authors.initials: RJ
authors.lastname: Kroeze
authors.forename: A J
authors.initials: AJ
authors.lastname: van der Veen
authors.forename: B J
authors.initials: BJ
authors.lastname: van Royen
authors.forename: R A
authors.initials: RA
authors.lastname: Bank
authors.forename: M N
authors.initials: MN
authors.lastname: Helder
authors.forename: T H
authors.initials: TH
authors.lastname: Smit
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D005260:Female; D005500:Follow-Up Studies; D006041:Goats; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery*; D023421:Models, Animal; D009068:Movement; D011859:Radiography; D016059:Range of Motion, Articular; D012399:Rotation; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D016474:Weight-Bearing / Q000502:physiology
references.citation: Clin Orthop Relat Res. 2002 Jan;(394):73-83
references.pmid: 11795754
references.citation: J Chin Med Assoc. 2003 Nov;66(11):676-81
references.pmid: 14768855
references.citation: Macromol Biosci. 2011 Jun 14;11(6):722-30
references.pmid: 21400658
references.citation: Spine (Phila Pa 1976). 2001 Feb 1;26(3):320-34
references.pmid: 11224871
references.citation: J Spinal Disord. 1996 Apr;9(2):117-20
references.pmid: 8793777
references.citation: Spine (Phila Pa 1976). 2001 May 15;26(10):1125-30
references.pmid: 11413423
references.citation: Eur Spine J. 2003 Feb;12(1):34-40
references.pmid: 12592545
references.citation: Acta Orthop. 2006 Jun;77(3):454-61
references.pmid: 16819685
references.citation: Spine J. 2009 Jul;9(7):607-8
references.pmid: 19560056
references.citation: J Bone Joint Surg Am. 2006 Apr;88 Suppl 2:103-9
references.pmid: 16595454
references.citation: Neurosurgery. 2006 Dec;59(6):1271-6; discussion 1276-7
references.pmid: 17277690
references.citation: Spine (Phila Pa 1976). 2002 Dec 1;27(23):2706-14
references.pmid: 12461397
references.citation: Spine (Phila Pa 1976). 2008 May 20;33(12):1337-43
references.pmid: 18496346
references.citation: Biomed Tech (Berl). 2003 Dec;48(12):349-55
references.pmid: 14740523
references.citation: Spine (Phila Pa 1976). 2006 Jun 15;31(14):1559-67
references.pmid: 16778688
references.citation: Spine (Phila Pa 1976). 2002 Apr 1;27(7):682-8
references.pmid: 11923659
references.citation: Eur Spine J. 2002 Apr;11(2):137-44
references.pmid: 11956920
references.citation: Spine (Phila Pa 1976). 2003 Aug 1;28(15 Suppl):S2-7
references.pmid: 12897467
references.citation: Eur Spine J. 2000 Feb;9 Suppl 1:S95-101
references.pmid: 10766064
references.citation: BMC Musculoskelet Disord. 2002 Oct 03;3:23
references.pmid: 12363369
references.citation: Spine (Phila Pa 1976). 1995 Dec 15;20(24 Suppl):85S-99S
references.pmid: 8747262
references.citation: J Bone Joint Surg Am. 1999 Jun;81(6):859-80
references.pmid: 10391552
references.citation: Spine (Phila Pa 1976). 2009 Dec 15;34(26):2858-64
references.pmid: 20010393
references.citation: Cytotherapy. 2009;11(8):1052-64
references.pmid: 19929469
references.citation: Acta Biomater. 2010 Jun;6(6):2060-5
references.pmid: 19944190
references.citation: Spine (Phila Pa 1976). 2004 Mar 15;29(6):635-41
references.pmid: 15014273