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Microdiscectomy is a common surgical procedure used to treat lumbar disc herniation. Following microdiscectomy, the space of the excised nucleus pulposus is replaced by fibrocartilaginous granulation tissue. This results in alterations of both the material properties of the intervertebral disc and the biomechanics of the lumbar motion segments, potentially contributing to adjacent segmental disc degeneration. To our knowledge, there is no published study in the English literature investigating this potential effect.
Materials and methods:
A previously developed three-dimensional finite element model of L3-L5 was used as a normal control. From this normal model, two different grades of disc degeneration models (mild and moderate) and corresponding microdiscectomy models were developed by changing either the geometry or associated material properties of L4-L5 segment. The 800 N pre-compressive loading plus 10 Nm moments simulating flexion, extension, lateral bending, and axial rotation were imposed on L3 superior end plate of each model. The intradiscal pressure, intersegmental rotation, and tresca stress of annulus fibrosus in L3-L4 segment were investigated.
The intradiscal pressure, intersegmental rotation, and tresca stress of L3-L4 segment in mild degeneration microdiscectomy model are higher than those in the mild degeneration model under all motion directions. The above parameters in moderate degeneration microdiscectomy model present a similar trend to the mild degeneration microdiscectomy model. However, the intersegmental rotation of L3-L4 in moderate degeneration microdiscectomy model is lower than that in the moderate degeneration model in lateral bending, and the intradiscal pressure of L3-L4 in moderate degeneration microdiscectomy model is lower than that in the moderate degeneration model in axial rotation.
Lumbar microdiscectomy can result in altered biomechanics, which may have an adverse effect on the development of adjacent upper segmental disc degeneration.
Journal of Surgical Research 09/2012; 182(1). DOI:10.1016/j.jss.2012.09.012 · 1.94 Impact Factor
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ABSTRACT: Our goal was to investigate the long-term results of anterior lumbar interbody fusion combined with percutaneous pedicle screw fixation for degenerative lumbar instability.
Forty-seven patients that had undergone anterior lumbar interbody fusion combined with percutaneous pedicle screw fixation for degenerative lumbar instability at Tianjin Hospital between May 2003 and January 2007 were reviewed retrospectively. Radiographic results including the fusion rate, disc space height, segmental lordosis and whole lumbar lordosis were analyzed, and clinical outcomes were assessed using the Japanese Orthopaedic Association score.
In 47 patients, no surgery-related neurological deficit or wound breakdown was observed and 45 patients obtained a solid fusion. The mean JOA score increased significantly (p < 0.05) from 9.4 before surgery to 24.6 six months after surgery and 26.1 at final follow-up. The disc space height, segmental lordosis and whole lumbar lordosis increased significantly from pre-operative values to both six months postoperatively (p < 0.05) and at the final follow up (p < 0.05). Radiographic evidence of adjacent segmental degeneration was found in 14 patients (29.8%) and symptomatic adjacent segmental disease developed in 1 patient (2.1%).
Anterior lumbar interbody fusion combined with percutaneous pedicle screws fixation in patients with degenerative lumbar instability results in good clinical and radiographic outcomes at long-term follow-up.
Turkish neurosurgery 03/2012; 22(2):156-60. DOI:10.5137/1019-5149.JTN.4214-11.1 · 0.58 Impact Factor
Journal of Orthopaedic Science 06/2011; 17(5):659-62. DOI:10.1007/s00776-011-0104-9 · 0.94 Impact Factor
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ABSTRACT: The increase in the number of anterior lumbar interbody fusions being performed carries with it the potential for the long-term complication of adjacent segmental degeneration. While its exact mechanism remains uncertain, adjacent segment degeneration has become much more widespread. Using a nonlinear, three-dimensional finite element model to analyze and compare the biomechanical influence of anterior lumbar interbody fusion and lumbar disc degeneration on the superior adjacent intervertebral disc, we attempt to determine if anterior lumbar interbody fusion aggravates adjacent segment degeneration.
A normal three-dimensional non-linear finite element model of L3-5 has been developed. Three different grades of disc degeneration models (mild, moderate, severe) and one anterior lumbar interbody fusion model were developed by changing either the geometry or associated material properties of the L4-5 segment. The 800 N pre-compressive loading plus 10 Nm moments simulating flexion, extension, lateral bending and axial rotation in five steps was imposed on the L3 superior endplate of all models. The intradiscal pressure, intersegmental rotation range and Tresca stress of the annulus fibrosus in the L3-4 segment were investigated.
The intradiscal pressure, intersegmental rotation range and Tresca stress of the L3-4 segment in the fusion model are higher than in the normal model and different degeneration models under all motion directions. The intradiscal pressures in the three degenerative models are higher than in the normal model in flexion, extension and lateral bending, whereas in axial rotation, the value of the mild degeneration model is lower. The intersegmental rotation ranges in the three degenerative models are higher than in the normal model in flexion and extension. The values for the mild degeneration model in lateral bending and all the degeneration models in axial rotation are lower than in the normal model. The Tresca stresses are higher in the three degenerative models than in the normal model.
Anterior lumbar interbody fusion has more adverse biomechanical influence than disc degeneration on the adjacent upper disc and may aggravate the adjacent upper segmental degeneration.
Journal of Orthopaedic Science 02/2011; 16(2):221-8. DOI:10.1007/s00776-011-0037-3 · 0.94 Impact Factor