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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

Diagram showing interpedicular travel (IPT) measurement technique. Position coordinates of radiopaque beads on the superior aspect of the L4 and L5 vertebrae were tracked at extremes of planar motion to determine IPT.
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Figure 0003: Diagram showing interpedicular travel (IPT) measurement technique. Position coordinates of radiopaque beads on the superior aspect of the L4 and L5 vertebrae were tracked at extremes of planar motion to determine IPT.

Mentions: Changes in the relative position of the pedicle at L4-L5 index level between peak planar loading conditions (± 7.5 Nm) was described using an IPT kinematic metric previously introduced by Cook et al.32 The magnitude of the three dimensional vector was calculated by tracking the digitized bead that was placed unilaterally on the superior notch of the L4 and L5 pedicles. From Figure 3, the vector r3(dashed) and can be expressed as its components (rx, ry, and rz) in each of the reference coordinate axes (x, y, z). The magnitude of this vector is defined as:


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)

Diagram showing interpedicular travel (IPT) measurement technique. Position coordinates of radiopaque beads on the superior aspect of the L4 and L5 vertebrae were tracked at extremes of planar motion to determine IPT.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 0003: Diagram showing interpedicular travel (IPT) measurement technique. Position coordinates of radiopaque beads on the superior aspect of the L4 and L5 vertebrae were tracked at extremes of planar motion to determine IPT.
Mentions: Changes in the relative position of the pedicle at L4-L5 index level between peak planar loading conditions (± 7.5 Nm) was described using an IPT kinematic metric previously introduced by Cook et al.32 The magnitude of the three dimensional vector was calculated by tracking the digitized bead that was placed unilaterally on the superior notch of the L4 and L5 pedicles. From Figure 3, the vector r3(dashed) and can be expressed as its components (rx, ry, and rz) in each of the reference coordinate axes (x, y, z). The magnitude of this vector is defined as:

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