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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

Lateral radiographs indicating sequential index level (L4-L5) instrumentation with the facet and disc replacement devices. As shown [L-R]: Unilateral FR and Unilateral FR + PDR.
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Figure 0004: Lateral radiographs indicating sequential index level (L4-L5) instrumentation with the facet and disc replacement devices. As shown [L-R]: Unilateral FR and Unilateral FR + PDR.

Mentions: Following kinematic evaluation of the intact L1-S1 specimen, a complete unilateral facetectomy at the L4-L5 index level was performed. The disc was left intact. The resected facet was subsequently reconstructed (Figure 4A) and tested (Unilateral -FR) with an appropriately sized arthroplasty device (ACADIA Facet Replacement System, Globus Medical Inc., Audubon, PA). The FR has been designed to closely mimic natural anatomy, kinematics and range of motion of the joint and is made of cobalt chrome alloy (Co-Cr-Mo) with highly polished articulating surfaces. The backing of the implant that interfaces with bone is plasma sprayed and coated with hydroxyapatite to promote bony in-growth. The implant was secured to the pedicle screws that were previously instrumented with locking nuts. Right or left side resection and replacement of the FR in the unilateral condition was randomized such that there were 3 right and 3 left unilateral facet replacements to account for instrumentation bias. For the third condition, the unilateral FR was temporarily removed, and a single posterior-lateral total disc prosthesis (PDR) was implanted (Triumph Lumbar Disc, Globus Medical Inc.) postero-laterally in the disc space. The PDR is a semi-constrained device made of Co-Cr-Mo alloy and has serrated endplate keels coated with titanium plasma and hydroxyapatite for enhanced bony in-growth (Figure 1B, Figure 4B). The device allows up to ± 15° of flexion/extension and lateral bending motion, and restricts axial rotation to ± 3° with a locking mechanism.


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)

Lateral radiographs indicating sequential index level (L4-L5) instrumentation with the facet and disc replacement devices. As shown [L-R]: Unilateral FR and Unilateral FR + PDR.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 0004: Lateral radiographs indicating sequential index level (L4-L5) instrumentation with the facet and disc replacement devices. As shown [L-R]: Unilateral FR and Unilateral FR + PDR.
Mentions: Following kinematic evaluation of the intact L1-S1 specimen, a complete unilateral facetectomy at the L4-L5 index level was performed. The disc was left intact. The resected facet was subsequently reconstructed (Figure 4A) and tested (Unilateral -FR) with an appropriately sized arthroplasty device (ACADIA Facet Replacement System, Globus Medical Inc., Audubon, PA). The FR has been designed to closely mimic natural anatomy, kinematics and range of motion of the joint and is made of cobalt chrome alloy (Co-Cr-Mo) with highly polished articulating surfaces. The backing of the implant that interfaces with bone is plasma sprayed and coated with hydroxyapatite to promote bony in-growth. The implant was secured to the pedicle screws that were previously instrumented with locking nuts. Right or left side resection and replacement of the FR in the unilateral condition was randomized such that there were 3 right and 3 left unilateral facet replacements to account for instrumentation bias. For the third condition, the unilateral FR was temporarily removed, and a single posterior-lateral total disc prosthesis (PDR) was implanted (Triumph Lumbar Disc, Globus Medical Inc.) postero-laterally in the disc space. The PDR is a semi-constrained device made of Co-Cr-Mo alloy and has serrated endplate keels coated with titanium plasma and hydroxyapatite for enhanced bony in-growth (Figure 1B, Figure 4B). The device allows up to ± 15° of flexion/extension and lateral bending motion, and restricts axial rotation to ± 3° with a locking mechanism.

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