134S Proceedings of the NASS 22nd Annual Meeting / The Spine Journal 7 (2007) 1S–163S
incorporation of allografts into the vertebrae. Finally, perioperative and
long-term complications were noted.
RESULTS: Mean patient age was 56. The average FU was 18 months
(12–42 months). The radiographic fusion rate was 97% of patients (32/33)
and 99% of levels (101/102). Minimal graft settling occurred even though
aggressive remodeling occurs (2 with over 5 deg settling). Graft incorpo-
ration by radiographic criteria was almost uniformly Grade I by the mod-
ified Bridwell-Lenke criteria, which correlates with the almost 100%
fusion rate. With the conservative BMP-use techniques used by surgeons
in our institute, which confines the BMP inside the allografts, there were
no incidents of respiratory complications.
CONCLUSIONS: RhBMP-2 is effective in significantly increasing ante-
rior multi-level cervical fusion rates when used with allograft and dynamic
plating. There is minimal graft settling without significantly affecting cer-
vical lordosis or fusion rate. The radiographic quality of fusion is also im-
proved, with allograft incorporation seen uniformly. When the rhBMP-2
containing sponge is confined entirely within the graft, no untoward
complications related to excessive neck swelling were observed.
FDA DEVICE/DRUG STATUS: rhBMP-2 (INFUSE): Not approved for
this indication.
doi: 10.1016/j.spinee.2007.07.319
P112. Surgical Repair of Pars Interarticularis Defect, 12 Year
Experience
Paul Lin, MD1; 1SUN Orthopaedic Group Inc., Lewisburg, PA, USA
BACKGROUND CONTEXT: Pars interarticularis defect may cause back
and leg pain and neurological compromise is some patients. A potential
outcome is isthmic spondlyolisthesis. Surgical options have included
any combination of the following: neural decompression, interbody or
posterolateral fusion, instrumentation, and reduction. This novel technique
improves the clinical outcome, prevents the development of spondylolis-
thesis and eliminates the need for lumbar fusion.
PURPOSE: The purpose of this paper is to describe the 12 year experi-
ence of the author in performing pars defect repairs. This includes a de-
scription of the evolution of the technique to where it stands today;
a novel approach using rhBMP and a pedicle screw based, compressive
tension band, posterior element fixation.
STUDY DESIGN/SETTING: Analysis of patient outcomes consisted of
review of 23 patients who underwent pars defect repair with a pedicle
based-posterior element fixation.
PATIENT SAMPLE: The patient population consisted of 18 males, and 5
females with an average age of 18 years (range 12-36 years) and a mean
follow-up of 3 years.
OUTCOME MEASURES: The surgery was considered successful if
there was a good clinical outcome, there was no development of spondy-
lolisthesis, and there was significant bone formation at the site of the par
defect. Clinical outcome was based on assessment of preoperative and
postoperative back and leg pain. Radiographic review was used to evaluate
development of spondylolisthesis and bone formation.
METHODS: Patients were evaluated clinically at regular intervals and as-
sessments made regarding use of pain medication, resumption of prior ac-
tivities including athletics, and ability to work if applicable. AP and lateral
radiographs were obtained every 6 months for 2 years. CT scans done prior
to surgery, and recommended at the 1 and 2 year follow-up exam. An in-
dependent radiologist was used for assessment of the development of spon-
dylolisthesis, bone formation at the level of the pars, and whether a union
of the defect had occurred.
RESULTS: Of the 23 patients included in the study, 20 rated their out-
come as ‘‘excellent’’, and 3 ‘‘very good’’. All agreed that the surgery
was worthwhile, and none were using narcotics. None of the 23 patients
had gone on to develop a spondylolisthesis, none required additional sur-
gery. There were no instances of hardware failure or removal. No surgical
complications were reported. Of the 9 patients who underwent repair using
the newer technique of repair using the Dynesys system (pedicle screws,
cord, and spacers) for posterior element fixation, and rhBMP with iliac
crest for graft, 4 went on to show CT evidence of bony healing of the
defect. Of the remaining 5, bone formation was present however a clear
union had not occurred.
CONCLUSIONS: Pars defect repair is an excellent alternative to offer se-
verely symptomatic patients who have failed conservative care. Rather
than fuse across a healthy disc space, this technique allows for a direct
repair of the defect. The literature is sparse regarding techniques that allow
for this. The author has been able to devise a techique that allows for se-
cure fixation of the posterior elements to a pedicle screw, and describes the
evolution of the grafting process to where it is today with autogenous iliac
graft and rhBMP. In the very least, this procedure allows for an excellent
clinical outcome with stabilization of the segment, and in some instances
allows for CT evidence of healing.
FDA DEVICE/DRUG STATUS: Dynesys: Not approved for this indica-
tion; Infuse: Not approved for this indication.
doi: 10.1016/j.spinee.2007.07.320
P113. In Vitro Effects of Recombinant Human GDF-5 on Human
and Rabbit Intervertebral Disc Cells
Cynthia Lee1, Mohamed Attawia1, Chantal Holy., PhD1, Liesbeth Brown1;1Johnson & Johnson Regenerative Therapeutics, Raynham, MA, USA
BACKGROUND CONTEXT: The stimulatory effects of recombinant hu-
man growth and differentiation factor-5 (rhGDF-5) on bovine interverte-
bral disc (IVD) cell biosynthesis in vitro has recently been reported and
in vivo studies have shown that intradiscal injections of rhGDF-5 can have
regenerative effects in a rabbit degeneration model. A link to the potential
efficacy in human patients, however, has been lacking.
PURPOSE: The purpose of this study was to investigate the dose-response
of human and rabbit annulus fibrosus (AF) and nucleus pulposus (NP) cells
to rhGDF-5.
STUDY DESIGN/SETTING: An in vitro experiment using human and
rabbit IVD cells in alginate beads.
METHODS: AF and NP cells from macroscopically normal human and
rabbit lumbar IVDs (n52 spines/species) were enzymatically isolated us-
ing sequential protease and collagenase digestion. Following expansion in
monolayer, cells were encapsulated in alginate beads and cultured in the
presence of 0, 30, 100, 200, or 500 ng/ml rhGDF-5 (BIOPHARM, GmbH).
On days 7 and 21, beads were harvested for DNA and GAG analysis (n53
groups of 9 beads for each dose and timepoint). On days 3 and 21, addi-
tional beads were harvested for gene expression analysis of aggrecan
(agg), collagen Ia2 (col1), collagen IIa1 (col2), collagen X (colX), and de-
corin (dcn) by real-time RT-PCR (n53 groups of 9 beads for each dose and
timepoint).
RESULTS: Biochemistry: There was no significant effect of rhGDF-5 on
DNA content. GAG accumulation for human AF cells was not affected by
rhGDF-5 on day 7, but was increased by day 21 for all rhGDF-5 doses. The
GAG content in human NP beads was increased with all rhGDF-5 concen-
trations by day 7 and sustained through day 21. In contrast, rabbit AF cells
showed a dose-dependent increase in GAG accumulation (on day 7 for one
donor and only on day 21 for the other) and no significant increase in NP
GAG accumulation over the 21 days. Gene Expression: The most dramatic
effects of rhGDF-5 on gene expression were seen for agg and col2 on day
21. Human AF cells showed an apparent peak in expression of these 2
genes at 100 ng/ml for one donor and a dose-dependent increase of the
same 2 genes through the 500 ng/ml dose for the other donor. Human
NP cells had an increase in gene expression with all doses of rhGDF-5,
with little difference from 100-500 ng/ml for one donor and from 30-
500 ng/ml for the other donor. For rabbit AF cells, the relative increase
in gene expression with rhGDF-5 treatment was seen at all dose levels,
was much greater than for humans, and the dose-dependent nature of the