title: Which factors prognosticate rotational instability following lumbar laminectomy?
abstract: OBJECTIVE
  Reduced strength and stiffness of lumbar spinal motion segments following laminectomy may lead to instability. Factors that predict shear biomechanical properties of the lumbar spine were previously published. The purpose of the present study was to predict spinal torsion biomechanical properties with and without laminectomy from a total of 21 imaging parameters.
  
  
  METHODS
  Radiographs and MRI of ten human cadaveric lumbar spines (mean age 75.5, range 59-88 years) were obtained to quantify geometry and degeneration of the motion segments. Additionally, dual X-ray absorptiometry (DXA) scans were performed to measure bone mineral content and density. Facet-sparing lumbar laminectomy was performed either on L2 or L4. Spinal motion segments were dissected (L2-L3 and L4-L5) and tested in torsion, under 1,600 N axial compression. Torsion moment to failure (TMF), early torsion stiffness (ETS, at 20-40 % TMF) and late torsion stiffness (LTS, at 60-80 % TMF) were determined and bivariate correlations with all parameters were established. For dichotomized parameters, independent-sample t tests were used.
  
  
  RESULTS
  Univariate analyses showed that a range of geometric characteristics and disc and bone quality parameters were associated with torsion biomechanical properties of lumbar segments. Multivariate models showed that ETS, LTS and TMF could be predicted for segments without laminectomy (r (2) values 0.693, 0.610 and 0.452, respectively) and with laminectomy (r (2) values 0.952, 0.871 and 0.932, respectively), with DXA-derived measures of bone quality and quantity as the main predictors.
  
  
  CONCLUSIONS
  Vertebral bone content and geometry, i.e. intervertebral disc width, frontal area and facet joint tropism, were found to be strong predictors of ETS, LTS and TMF following laminectomy, suggesting that these variables could predict the possible development of post-operative rotational instability following lumbar laminectomy. Proposed diagnostic parameters might aid surgical decision-making when deciding upon the use of instrumentation techniques.
authors.affiliation: Department of Orthopedic Surgery, Research Institute MOVE, VU University Medical Center, De Boelelaan 1117, P.O. Box 7057, 1081 HV, Amsterdam, The Netherlands.
authors.forename: Arno
authors.initials: A
authors.lastname: Bisschop
authors.forename: Idsart
authors.initials: I
authors.lastname: Kingma
authors.forename: Ronald L A W
authors.initials: RL
authors.lastname: Bleys
authors.forename: Albert J
authors.initials: AJ
authors.lastname: van der Veen
authors.forename: Cornelis P L
authors.initials: CP
authors.lastname: Paul
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieën
authors.forename: Barend J
authors.initials: BJ
authors.lastname: van Royen
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D015519:Bone Density; D002102:Cadaver; D019299:Decompression, Surgical; D004548:Elasticity; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis / Q000209:etiology*; D007796:Laminectomy / Q000009:adverse effects*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016059:Range of Motion, Articular; D012307:Risk Factors; D013130:Spinal Stenosis / Q000175:diagnosis / Q000209:etiology; D054159:Torsion, Mechanical
references.citation: Radiology. 1987 Jul;164(1):227-30
references.pmid: 3588910
references.citation: J Clin Densitom. 2004 Winter;7(4):364-7
references.pmid: 15618595
references.citation: Eur Spine J. 2006 Jun;15(6):705-18
references.pmid: 16172902
references.citation: Skeletal Radiol. 1999 Apr;28(4):215-9
references.pmid: 10384992
references.citation: Eur Spine J. 2012 Mar;21(3):530-6
references.pmid: 21863461
references.citation: Eur Spine J. 2010 Dec;19(12):2130-6
references.pmid: 20582709
references.citation: Spine (Phila Pa 1976). 1989 Jun;14(6):606-10
references.pmid: 2749376
references.citation: Skeletal Radiol. 1989;17(8):556-60
references.pmid: 2919295
references.citation: J Rheumatol. 1993 Nov;20(11):1911-8
references.pmid: 8308778
references.citation: Spine (Phila Pa 1976). 1992 Jun;17(6 Suppl):S149-54
references.pmid: 1631714
references.citation: J Bone Joint Surg Am. 1996 Mar;78(3):403-11
references.pmid: 8613448
references.citation: Spine (Phila Pa 1976). 1991 Jan;16(1):22-8
references.pmid: 2003233
references.citation: Eur Spine J. 2006 Jun;15(6):720-30
references.pmid: 16328226
references.citation: Spine (Phila Pa 1976). 2007 Nov 15;32(24):E708-12
references.pmid: 18007231
references.citation: Eur Spine J. 2007 Aug;16(8):1209-14
references.pmid: 17203270
references.citation: Phys Ther. 2006 Aug;86(8):1091-105
references.pmid: 16879043
references.citation: Ergonomics. 2004 Oct 22;47(13):1365-85
references.pmid: 15513714
references.citation: Spine (Phila Pa 1976). 1991 Apr;16(4):450-6
references.pmid: 2047918
references.citation: Spine (Phila Pa 1976). 2001 Sep 1;26(17):1873-8
references.pmid: 11568697
references.citation: Spine (Phila Pa 1976). 2006 Jul 1;31(15):E494-8
references.pmid: 16816749
references.citation: Radiology. 1988 Jan;166(1 Pt 1):193-9
references.pmid: 3336678
references.citation: Radiology. 2001 May;219(2):368-74
references.pmid: 11323459
references.citation: Clin Orthop Relat Res. 1982 May;(165):110-23
references.pmid: 6210480
references.citation: Eur Spine J. 2012 Dec;21(12):2640-8
references.pmid: 22426708
references.citation: Eur Spine J. 1998;7(3):229-38
references.pmid: 9684957
references.citation: J Electromyogr Kinesiol. 2007 Feb;17(1):14-24
references.pmid: 16531071
references.citation: Eur Spine J. 2013 Aug;22(8):1785-93
references.pmid: 23460462
references.citation: Spine (Phila Pa 1976). 1984 Jan-Feb;9(1):53
references.pmid: 6719257