Biomechanical Comparison of Lumbar Fixed-Point Oblique Pulling Manipulation and Traditional Oblique Pulling Manipulation in Treating Lumbar Intervertebral Disk Protrusion

Does Lumbar Interbody Fusion Modality Affect the Occurrence of Complications in an Osteoporotic Spine Under Whole-Body Vibration? A Finite Element Study

OBJECTIVE

To evaluate the effects of 3 lumbar interbody fusion techniques on the occurrence of complications in an osteoporotic spine under whole-body vibration.

METHODS

A previously developed and validated nonlinear finite element model of L1-S1was modified to develop anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF), and transforaminal lumbar interbody fusion (TLIF) models with osteoporosis. In each model, the lower surface of the sacrum was absolutely fixed, a follower load of 400N was applied through the axis of the lumbar spine, and an axial sinusoidal vertical load of ±40N (5 Hz) was imposed on the superior surface of L1, to perform a transient dynamic analysis. The maximal values of intradiscal pressure, shear stress on annulus substance, disc bulge, facet joint stress, and screw and rod stress, along with their dynamic response curves, were collected.

RESULTS

Among these 3 models, the TLIF model generated the greatest screw and rod stress, and the PLIF model generated the greatest cage-bone interface stress. At the L3-L4 level, compared with the other 2 models, the maximal values and dynamic response curves of intradiscal pressure, shear stress of annulus ground substance, and disc bulge were all lower in the ALIF model. However, the facet contact stress at the adjacent segment in the ALIF model was higher than that in the other 2 models.

CONCLUSIONS

In an osteoporotic spine under whole-body vibration, TLIF has the highest risk of screw and rod breakage, PLIF has the highest risk of cage subsidence, and ALIF has the lowest risk of upper adjacent disc degeneration, but the highest risk of adjacent facet joint degeneration.

Does Osteoporosis Affect the Adjacent Segments Following Anterior Lumbar Interbody Fusion? A Finite Element Study

BACKGROUND

Adjacent segment degeneration is a common complication following anterior lumbar interbody fusion (ALIF). Osteoporosis is becoming increasingly prevalent in the elderly population and thus patients undergoing ALIF may experience osteoporosis with age. However, the influence of osteoporosis on adjacent segment degeneration after ALIF remains unclear.

METHODS

Three finite element models of the L3-S1 segment, including a healthy model, an ALIF model, and an ALIF with osteoporosis model, were used for analysis. ALIF was simulated at the L4-L5 segment. Based on a hybrid test method, the models were imposed with a preload of 400 N and an adjusted moment in flexion, extension, lateral bending, and axial torsion. Intradiscal pressure, shear stress on anulus fibrosus, and range of motion at L3-L4 and L5-S1 were calculated and compared.

RESULTS

In each direction, the maximal values of intradiscal pressure and shear stress on anulus fibrosus at L3-L4 and L5-S1 were found in the ALIF model, and the minimal values were found in the healthy model. At L3-L4 and L5-S1, the maximal values of range of motion in most directions were found in the ALIF model followed by the ALIF with osteoporosis model, and the minimal values were found in the healthy model. However, the maximal value of range of motion at L5-S1 in axial torsion was found in the ALIF with osteoporosis model.

CONCLUSIONS

Osteoporosis may mitigate the adverse influence of ALIF on adjacent segments.