Instantaneous Axis of Rotation as a Function of the Three Columns of the Spine

Häher, Thomas R.; O’Brien, Michael F.; Felmly, William T.; Welin, Daniel; Perrier, Greg; Choueka, Jack; Devlin, Vincent J.; Vassiliou, A.; Chow, G.

doi:10.1097/00007632-199206001-00015

Cited by 67 publications

(42 citation statements)

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“…In addition, the negative effect of laminectomy on ETS was marginally larger in severely degenerated discs (mean 2.7 Nm/degree) in comparison to mildly degenerated discs (mean 1.5 Nm/degree). As expected, an interaction between disc degeneration and laminectomy was found, since laminectomy causes a shift in load-bearing from the posterior elements to anterior elements [14]. Notably, spinal segments treated with laminectomy and in the presence of severe intervertebral disc degeneration were still found to be stiffer than untreated mildly degenerated segments.…”

Section: Discussionsupporting

confidence: 69%

Torsion biomechanics of the spine following lumbar laminectomy: a human cadaver study

et al. 2013

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Purpose Lumbar laminectomy affects spinal stability in shear loading. However, the effects of laminectomy on torsion biomechanics are unknown. The purpose of this study was to investigate the effect of laminectomy on torsion stiffness and torsion strength of lumbar spinal segments following laminectomy and whether these biomechanical parameters are affected by disc degeneration and bone mineral density (BMD). Methods Ten human cadaveric lumbar spines were obtained (age 75.5, range 59-88). Disc degeneration (MRI) and BMD (DXA) were assessed. Disc degeneration was classified according to Pfirrmann and dichotomized in mild or severe. BMD was defined as high BMD (Cmedian BMD) or low BMD (\median BMD). Laminectomy was performed either on L2 (59) or L4 (59). Twenty motion segments (L2-L3 and L4-L5) were isolated. The effects of laminectomy, disc degeneration and BMD on torsion stiffness (TS) and torsion moments to failure (TMF) were studied.Results Load-displacement curves showed a typical bi-phasic pattern with an early torsion stiffness (ETS), late torsion stiffness (LTS) and a TMF. Following laminectomy, ETS decreased 34.1 % (p \ 0.001), LTS decreased 30.1 % (p = 0.027) and TMF decreased 17.6 % (p = 0.041). Disc degeneration (p \ 0.001) and its interaction with laminectomy (p \ 0.031) did significantly affect ETS. In the mildly degenerated group, ETS decreased 19.7 % from 7.6 Nm/degree (6.4-8.4) to 6.1 Nm/degree (1.5-10.3) following laminectomy. In the severely degenerated group, ETS decreased 22.3 % from 12.1 Nm/degree (4.6-21.9) to 9.4 Nm/degree (5.6-14.3) following laminectomy. In segments with low BMD, TMF was 40.7 % (p \ 0.001) lower than segments with high BMD [34.9 Nm (range 23.7-51.2) versus 58.9 Nm (range 43.8-79.2)]. Conclusions Laminectomy affects both torsion stiffness and torsion load to failure. In addition, torsional strength is strongly affected by BMD whereas disc degeneration affects torsional stiffness. Assessment of disc degeneration and BMD pre-operatively improves the understanding of the biomechanical effects of a lumbar laminectomy.

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Section: Discussionsupporting

confidence: 69%

Torsion biomechanics of the spine following lumbar laminectomy: a human cadaver study

et al. 2013

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“…This phenomenon is known as the ''coupling'' of rotation and translation between anatomic axes [17][18][19]. Based on coupled motions of the spine, 3-dimensional correction with DVR appears to be an obvious component of scoliosis correction and should deliver an overall better result.…”

Section: Discussionmentioning

confidence: 99%

The Impact of Direct Vertebral Rotation (DVR) on Radiographic Outcome in Surgical Correction of Idiopathic Scoliosis

Urbański¹,

Wolańczyk²,

Jurasz³

et al. 2017

J Spine

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Introduction Recent developments of spinal instruments allow to address nearly all components of idiopathic scoliosis. Direct vertebral rotation (DVR) maneuver was introduced to correct apical axial vertebral rotation. It is however still not well established how efficiently DVR affects results of scoliosis correction. The object of the study was to evaluate en bloc apical vertebral rotation (DVR) and its impact on coronal and sagittal correction of the spine in patients undergoing surgical scoliosis treatment. Materials and methods Thirty-six consecutive patients who underwent posterior spinal fusion with pedicle screws only constructs for idiopathic scoliosis. Fifteen patients (20 curves) were corrected by rod derotation only and 21 patients (26 curves) had both rod derotation and DVR. Curve measurements were performed on x-rays obtained before and postoperatively-coronal curves, kyphosis (T2-T12, T5-T12). Spine flexibility was assessed on prone bending x-rays. Apical axial rotation was determined on CT scans obtained intraoperatively and postoperatively. Rotation angle (RAsag) was measured according to Aaro and Dahlborn. Results We observed reduction of RAsag in all patients; however, in DVR group, decrease was greater, by 31.8% comparing to non-DVR group, by 8.6% (p = 0.0003). Mean coronal correction in DVR group was 68.8% and in rod derotation group without DVR 55% (p = 0.002). No significant correlation was found between degree of derotation obtained and coronal correction. In DVR group T2-T12 kyphosis has increased in 28 (65%) patients whereas in non-DVR group in 31 (69%) cases. Mean value of T2-T12 kyphosis growth was 16.7% in DVR and 22.1% in non-DVR group. These differences however did not occur statistically significant. Conclusions Direct vertebral rotation (DVR) maneuver reduces significantly apical rotation of the spine, enhances ability of coronal correction, and it does not reduce thoracic kyphosis.

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“…It was striking that, in untreated segments, these geometrical parameters were significantly correlated to TMF, while in treated segments, a correlation with ETS was found. This possibly reflects the fact that laminectomy causes a shift in load-bearing from the posterior elements to the anterior elements [11], leading to a significant correlation between stiffness in the early phase and intervertebral disc geometry.…”

Section: Discussionmentioning

confidence: 99%

Which factors prognosticate rotational instability following lumbar laminectomy?

Bisschop

Kingma²,

Bleys³

et al. 2013

Eur Spine J

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Purpose 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. Method 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 postoperative rotational instability following lumbar laminectomy. Proposed diagnostic parameters might aid surgical decision-making when deciding upon the use of instrumentation techniques.

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Instantaneous Axis of Rotation as a Function of the Three Columns of the Spine

Cited by 67 publications

References 0 publications

Torsion biomechanics of the spine following lumbar laminectomy: a human cadaver study

Torsion biomechanics of the spine following lumbar laminectomy: a human cadaver study

The Impact of Direct Vertebral Rotation (DVR) on Radiographic Outcome in Surgical Correction of Idiopathic Scoliosis

Which factors prognosticate rotational instability following lumbar laminectomy?

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