Limits...
Postero-lateral disc prosthesis combined with a unilateral facet replacement device maintains quantity and quality of motion at a single lumbar level.

Nayak AN, Doarn MC, Gaskins RB, James CR, Cabezas AF, Castellvi AE, Santoni BG - Int J Spine Surg (2014)

Bottom Line: ROM, ICR, and IPT measurements were compared (repeated measures ANOVA) between the three conditions.Compared to the intact spine, no significant changes in F/E, LB or AR ROM were identified as a result of unilateral FR or unilateral FR + PDR.No significant changes in adjacent L3-L4 or L5-S1 ROM were identified in any loading mode.

View Article: PubMed Central - PubMed

Affiliation: Phillip Spiegel Orthopaedic Research Laboratory, Foundation for Orthopaedic Research & Education, Tampa, FL, USA.

ABSTRACT

Background: Mechanically replacing one or more pain generating articulations in the functional spinal unit (FSU) may be a motion preservation alternative to arthrodesis at the affected level. Baseline biomechanical data elucidating the quantity and quality of motion in such arthroplasty constructs is non-existent.

Purpose: The purpose of the study was to quantify the motion-preserving effect of a posterior total disc replacement (PDR) combined with a unilateral facet replacement (FR) system at a single lumbar level (L4-L5). We hypothesized that reinforcement of the FSU with unilateral FR to replace the resected, native facet joint following PDR implantation would restore quality and quantity of motion and additionally not change biomechanics at the adjacent levels.

Study design: In-vitro study using human cadaveric lumbar spines.

Methods: Six (n = 6) cadaveric lumbar spines (L1-S1) were evaluated using a pure-moment stability testing protocol (±7.5 Nm) in flexion-extension (F/E), lateral bending (LB) and axial rotation (AR). Each specimen was tested in: (1) intact; (2) unilateral FR; and (3) unilateral FR + PDR conditions. Index and adjacent level ROM (using hybrid protocol) were determined opto-electronically. Interpedicular travel (IPT) and instantaneous center of rotation (ICR) at the index level were radiographically determined for each condition. ROM, ICR, and IPT measurements were compared (repeated measures ANOVA) between the three conditions.

Results: Compared to the intact spine, no significant changes in F/E, LB or AR ROM were identified as a result of unilateral FR or unilateral FR + PDR. No significant changes in adjacent L3-L4 or L5-S1 ROM were identified in any loading mode. No significant differences in IPT were identified between the three test conditions in F/E, LB or AR at the L4-L5 level. The ICRs qualitatively were similar for the intact and unilateral FR conditions and appeared to follow placement (along the anterior-posterior (AP) direction) of the PDR in the disc space.

Conclusion: Biomechanically, quantity and quality of motion are maintained with combined unilateral FR + PDR at a single lumbar spinal level.

No MeSH data available.


Related in: MedlinePlus

Representative lateral radiographs with plot of the center of rotation for all six specimens at the L4-L5 level as a function of instrumentation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4325497&req=5

Figure 0006: Representative lateral radiographs with plot of the center of rotation for all six specimens at the L4-L5 level as a function of instrumentation.

Mentions: The calculated ICR at the instrumented level was plotted on lateral radiographs of a single specimen, not tested as part of the current experiment, in the intact and progressively instrumented conditions. A best-fit plot was created to demonstrate the relative changes in position of the centroid of motion as a function of instrumented condition (Figure 6). Overall, intact ICRs were generally localized in the anterior and middle columns of the L4-L5 FSU within the disc space and inferior to the superior endplate of L5. Unilateral facet arthroplasty after facetectomy (Uni-FR) qualitatively maintained the ICR in a location consistent with that of the intact FSU. The addition of the posterior total disc (Uni FR + PDR) resulted in a more diffuse pattern of ICR localized inferior to the superior L5 endplate. The ICRs appeared to qualitatively shift along the AP direction as a result of sagittal plane placement of the PDR within the disc space. A slightly posterior placement of the PDR within the disc space appeared to restore the ICR to near that of the intact FSU, while a more central placement shifted the ICR slightly in the anterior direction.


Postero-lateral disc prosthesis combined with a unilateral facet replacement device maintains quantity and quality of motion at a single lumbar level.

Nayak AN, Doarn MC, Gaskins RB, James CR, Cabezas AF, Castellvi AE, Santoni BG - Int J Spine Surg (2014)

Representative lateral radiographs with plot of the center of rotation for all six specimens at the L4-L5 level as a function of instrumentation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4325497&req=5

Figure 0006: Representative lateral radiographs with plot of the center of rotation for all six specimens at the L4-L5 level as a function of instrumentation.
Mentions: The calculated ICR at the instrumented level was plotted on lateral radiographs of a single specimen, not tested as part of the current experiment, in the intact and progressively instrumented conditions. A best-fit plot was created to demonstrate the relative changes in position of the centroid of motion as a function of instrumented condition (Figure 6). Overall, intact ICRs were generally localized in the anterior and middle columns of the L4-L5 FSU within the disc space and inferior to the superior endplate of L5. Unilateral facet arthroplasty after facetectomy (Uni-FR) qualitatively maintained the ICR in a location consistent with that of the intact FSU. The addition of the posterior total disc (Uni FR + PDR) resulted in a more diffuse pattern of ICR localized inferior to the superior L5 endplate. The ICRs appeared to qualitatively shift along the AP direction as a result of sagittal plane placement of the PDR within the disc space. A slightly posterior placement of the PDR within the disc space appeared to restore the ICR to near that of the intact FSU, while a more central placement shifted the ICR slightly in the anterior direction.

Bottom Line: ROM, ICR, and IPT measurements were compared (repeated measures ANOVA) between the three conditions.Compared to the intact spine, no significant changes in F/E, LB or AR ROM were identified as a result of unilateral FR or unilateral FR + PDR.No significant changes in adjacent L3-L4 or L5-S1 ROM were identified in any loading mode.

View Article: PubMed Central - PubMed

Affiliation: Phillip Spiegel Orthopaedic Research Laboratory, Foundation for Orthopaedic Research & Education, Tampa, FL, USA.

ABSTRACT

Background: Mechanically replacing one or more pain generating articulations in the functional spinal unit (FSU) may be a motion preservation alternative to arthrodesis at the affected level. Baseline biomechanical data elucidating the quantity and quality of motion in such arthroplasty constructs is non-existent.

Purpose: The purpose of the study was to quantify the motion-preserving effect of a posterior total disc replacement (PDR) combined with a unilateral facet replacement (FR) system at a single lumbar level (L4-L5). We hypothesized that reinforcement of the FSU with unilateral FR to replace the resected, native facet joint following PDR implantation would restore quality and quantity of motion and additionally not change biomechanics at the adjacent levels.

Study design: In-vitro study using human cadaveric lumbar spines.

Methods: Six (n = 6) cadaveric lumbar spines (L1-S1) were evaluated using a pure-moment stability testing protocol (±7.5 Nm) in flexion-extension (F/E), lateral bending (LB) and axial rotation (AR). Each specimen was tested in: (1) intact; (2) unilateral FR; and (3) unilateral FR + PDR conditions. Index and adjacent level ROM (using hybrid protocol) were determined opto-electronically. Interpedicular travel (IPT) and instantaneous center of rotation (ICR) at the index level were radiographically determined for each condition. ROM, ICR, and IPT measurements were compared (repeated measures ANOVA) between the three conditions.

Results: Compared to the intact spine, no significant changes in F/E, LB or AR ROM were identified as a result of unilateral FR or unilateral FR + PDR. No significant changes in adjacent L3-L4 or L5-S1 ROM were identified in any loading mode. No significant differences in IPT were identified between the three test conditions in F/E, LB or AR at the L4-L5 level. The ICRs qualitatively were similar for the intact and unilateral FR conditions and appeared to follow placement (along the anterior-posterior (AP) direction) of the PDR in the disc space.

Conclusion: Biomechanically, quantity and quality of motion are maintained with combined unilateral FR + PDR at a single lumbar spinal level.

No MeSH data available.


Related in: MedlinePlus