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Journal of Orthopaedics
ISSN 0972-978X
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ORIGINAL ARTICLE
Current Issue
Comparative Study of Rigid Versus Dynamic Spine
Stabilization for Degenerative Lumbar Spine disorders
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Ganesh Natarajan*,Manish Desai*,Muralikuttan**
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* Senior House Officer (Orthopaedics
and Trauma)
**Consultant, (Orthopaedics and Trauma)
CalderdaleRoyal hospital, Halifax, HX3 OLF,West Yorkshire, U.K
Address for Correspondence:
Mr Ganesh Natarajan, MBBS, MS (Ortho), MRCS
Senior House Officer (Orthopaedics and Trauma)
CalderdaleRoyal Hospital, Halifax, HX3 OLF
West Yorkshire. U.K.
Tel: 0044-1422301726
Fax: 0044-1422222296
E-mail: [email protected]
Abstract:
Discussions
About COAA
Dept of
Orthopedics
Med College,
Calicut
Design: Retrospective study
Objectives: Analyze short-term effects of Rigid (Group R) Versus Dynamic(Group
instrumentation in terms of Subjective evaluation & Patient oriented outcome.
Materials and Methods: 50 patients (Male 17: female 33), 25 in each group. Evaluation based I
pre & postoperative Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) at fixe
interval at 6 weeks, 6 months, 1 and 2 years.
Results: Mean preoperative VAS for LBP (Group D) was 6.9, and decreased at 24 mont
postoperative to 3.4 and for Group R was 7.6 to 3.7. Mean VAS for leg pain for Group D was frc
6.2 to 2.1 a t 24 months and for Group R 6.9 t o 3.0. Mean ODI for Group D was from 54 to
and for Group R i t was 56 t o 39, suggesting less improvement in cases operated with ric
stabilization compare to Dynesys system. ODI for Group D, follows descending Pattern as scor
43.0, 38, 32.5 and 29 , whereas for Group R was 27, 30, 35 and 39 at 6 wks, 6 months, 1 and
yrs, respectively. There is no age related difference in outcome in both systems. Disc prolap
patients improved significantly with Rigid system, while Spine instability had better outcome wi
Dynesys.
Discussion: Rigid fixation, there is no consistent improvement in the ODI, up t o 2 yrs follow up.
rigid fixation system even after fusion the instrumentation is in place, which contributes
unfavorable outcome in relation to probably loss of lumbar lordosis, and progression
degenerative process at adjacent levels contributing to less favorable clinical outcome.
Conclusion: Dynesys has better outcome in older age group patients, stenosis and listhes
Dynesys can be considered as an effective option to rigid stabilization systems.
J. Orthopaedics 2007;4(3)e7
Study Design:
Retrospective comparative clinical study on a consecutive series of 25 patients in each group.
Keywords:
Dynesys - semi rigid spinal instrumentation system; Rigid fixation - pedicle screw and rod syst€
with fusion; VAS- Visual Analogue Score; ODI- Oswestry Disability Index
Background Data:
Journal of Orthopaedics
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Lurnbar spine fusion with rigid instrurnentation for degenerative spinal disorders seems to increa
the fusion rate. However, rigid instrumentation may be associated with some undesirable effeci
such as increased low back pain following decrease of lumbar lordosis, fracture of the vertebi
body and pedicle, pedicle screw loosening, and adjacent segment degenerationll. The use of sei
rigid and dynamic devices has been advocated to reduce such adverse effects of the ric_
instrurnentation and thus t o achieve a more physiologic bony fusion.
Dynesys is design t o preserve intersegrnental kinernatics and alleviate loading of facet joints a!
they're by preserving articular function2&3. I n the Course of degenerative process, during whi
the segment undergoes various anatomic alterations, there are significant changes in both moil
characteristics of, and the load distribution across the affected segments4.
This new system for treating Lumbar degenerative pathology based on lumbar stabilization ai
preservation of articular function, as opposed to traditional arthrodesis restrictions3
The concept of spinal fusion originally arose from the notion that a degenerated motion segment
often"unstable" or shows " Movement abnormalities," and that accordingly, the elimination
motion in the affected segment would prevent i t from undertaking the movements associated wi
the generation of pain. Recent thinking, however, suggests that the preservation of movement
say rnay not be the most irnportant factor accounting for the success of fusion.
By preserving flexibility of a motion segment may allows greater physiological function7.
Rigid fixation system for fusion only, has t o serve temporary stabilization until fusion has t a k ~
place while on the other hand, the soft stabilization system has t o provide stability throughout
life8.
This study is to compare the postoperative effects of a rigid versus dynamic instrumentation f
degenerative spine disease and stenosis and to investigate if a dynamic spine system can repla
the commonly used rigid systems in order to avoid the above mentioned disadvantages of ric
fixation.
Objectives:
1) To analyze the short-term effects of Rigid Versus Dynamic instrumentation on
lumbar spine surgery.
2) Subjective evaluation & Patient oriented outcome of the result.
3) To evaluate complications rate associated with both system.
Materials And Methods:
Patients: This study analyzes series of 50 adult patients (Male 17: female 33), 25 in Group
(Rigid Fixation) and 25 patients in Group D (Dynesys System) operated at District General Hospit,
by Same Surgeon Using Rigid and Dynesys System.
Clinical evaluation for both groups was based on pre & post operative Visual Analogue Scale (VA
and Oswestry Disability Index (ODI) at Fixed interval at 6 weeks, 6 rnonths, 1 and 2 years. Me,
age of the study Group R was 49 yrs (range 23-74 yrs) and 52yrs (range 24 - 70 yrs) for group
We analyzed the outcorne of both Systems in different indications like Lumbar Stenosis, Di
Prolapse, and Spondylolisthesis and with Degenerative Disc Disease.
In-group D, 6 patients and group R 1 patient had pedicle screw Fixation of more than two levels.
patients were investigated with pre & postoperative standard X-ray and MRI of Lurnbar spine.
Preoperative evaluation: Preoperative evaluation included patient history, imaging, and clinic
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Journal of Orthopaedics
and neurological evaluation by the treating surgeon.
Surgery: Both the systerns consist of pedicle screws made of Ti-Al-Nb forge alloy. The screws a
connected with a polyethylene terephthalate cord (Dynesys) / Ti-Al-Nb Rods. Tethering the CO
and selecting the appropriate length of the spacerlrod between the screws rnay apply segmeni
distraction or compression.
The procedure was peiformed in prone position. A midline approach, with dissection of the erect
spinae rnuscles, provided access to the bony anatorny of the lurnbar spine. I f indicat,
decompression of the spinal canal was performed first. Insertion oF the pedicle screws was carri,
out under radiologic control using a C-arm. The polycarbonate urethane spacer was cut accordi
to the measure distance between the screws, with the length being chosen to cornpensate a
existing lordosis or kyphosis. The central cord and the spacer were then locked within the scrc
heads. No postoperative brace was given, and patients were rnobilized if safe to do.
Radiologie and Clinical follow-up: The first post op
error, or other complications were docurnented.
X
rays were exarnined and any technic
Results:
All patients were evaluated up to 24 months after surgery. The results were analyzed based of t
clinical Scores of VAS & ODI systern and also study of complications by analyzing the X ray and M
as indicated.
Regarding VAS scoring systern we considered VAS for Low Back Pain (LBP) and Leg Pain separat6
for surgical outcorne analysis.
VAS SCORE - LBP FOR DYllESYS
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The rnean preoperative Scores of Visual Analogue Scale for low back Pain for (Group D) was 6.
and decreased after surgery at end of 24 months follow up t o 3.4 and for Group R Same was 7
and post op Score was irnproved t o 3.7.
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VAS SCORE- LBP FOR RlGlDFlXATlON
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Journal of Orthopaedics
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Similarly mean Scores of Visual Analogue Scale for Leg pain for (Group D) was decreased from
op 6.2 to 2.1 at end of 24 months follow up., and Same was improved from 6.9 to 3.0 for Group F
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VAS SCORE - LEG PAIN FOR OYlrlESYS
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VAS SCORE - LEG PAlN FOR RIGID FIXATIOtJ
The final results of ODI scoring for group D were 29 at end of 24 months post operative follow LI
with respect to 54 score, prior to treatment and for group R i t was 39 at post op follow up from I:
operative score of 56, suggesting less improvement in cases operated with rigid stabilizatil
compare to Dynesys System.
The improvement pattern for ODI score for Group D was observed at different interval, whi
follows a descending pattern as 43.0, 38, 32.5 and 29 at 6 wks, 6 months, 1 yr, and 2 yi
respectively that represents an improvement of 20°/o, 29%, 40% and 46%.
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ODI SCORE FOR DYNESY S
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The improvement Pattern for ODI Score for Group R was observed at different interval, whi
follows a different Pattern from group D as 27.0, 30.5, 35 and 39 at 6 wks, 6 months, 1 yr, and
yrs, respectively that represents an improvement of 5l0/0, 46%, 37% and 30%.
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I n patients operated for more than two Segments of Dynesys fixation the ODI score was 52, and :
preop and post op respectively, which suggests less improvement in clinical outcome whl
compared with entire study group.
I n this study we compared clinical outcome in age group more than 50 yrs, (Group A), with those
the age group less than 50 yrs (Group B).
I n Group A (Dynesys) mean ODI score was 50 and 25, pre and post operative respectively, th
suggests >50 O/O improvement in clinical outcome.
I n Group A (Rigid) mean ODI score was 52 and 39, pre and post operative respectively, th
suggests >25 O/O improvement in clinical outcome.
Group B (Dynesys) mean ODI Score was 62, and 34, pre and post operative respectively.
Group B (Rigid) mean ODI Score was 60, and 39, pre and post operative respectively
This suggests there is no age related difference in final clinical outcome in relation to this bo
Fixation Systems.
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Journal of Orthopaedics
When analyzing the final outcome for Dynesys in relation t o different surgical indications, it W
observed that more than 5O0/0 improvement in the ODI Score, from 49 to 21, pre and pc
operative respectively in lumbar instability especially spondylolisthesis and Lumbar canal Steno!
(post laminectomy).
INDICATIONS FOR DYNESYS
U POST
STEFlDSlS
DlSC PROLAPSE
OP
LlSTHESlS
Final Outcome for rigid fixation in relation to different surgical indications was observed wi
different Pattern, Disc prolapse ODI improved from 76 t o 25, for Stenosis from 46 t o 37, and f
Listhesis it changed from 50 to 37.
INDICATIONS FOR RIGID FIXATION
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POST OP
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STENOSIS
DlSC PROLAPSE
LISTHESIS
Complications:
With regard to complications, we would like to point out total 10 (20°/0) cases, 3 superfic
infections, 1 seroma, and 4 cases due to technical error and 2 cases had nerve root irritation.
lnfection
1
Nerve irritation
Technical error
http://www.jortho.org/2007/4/3/e7/index.html
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Journal of Orthopaedics
Discussion:
This study shows that Rigid instrumentation applied over a short area for Disc Prolapse patholof
OF lumbar spine has significant clinical improvement by 70% of both self-assessment and P i
score. But in case of Dynesys instrumentation applied for indications including Stenosis ai
Listhesis of lumbar spine has significant clinical improvement by >SO% of both self-assessment al
pain score.
From this study we infer that VAS system for back pain and leg pain shows significant improveme
in final assessment score at 2 yrs follow up, using Dynesys system, as a method of dynan
fixation except in some patients, in whom results are not up to expectation because of associatm
post operative complication like infection and screw malposition. Though our study did not shc
any more complications related to this system itself.
As Dynesys is not a rigid method of fixation and fusion, i t has been observed that, there is gradi
improvement of symptoms and score over a period of two years follow up as per the graph.
PAEAfl ODI SCORE FOR DYllESYS
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'IJEEKS
It has been observed that in using Rigid fixation, there is no consistent improvement in the 0
score, up to 2 yrs follow up. Though initial period of first 6 wks follow up shows significa
improvement in ODI score, but subsequent follow up scoring shows increase in Symptoms a
unfavorable over all long term outcome.
Rigid fixation system is for fusion only, has to serve temporary stabilization until fusion has takl
placel9 while in rigid fixation system even after fusion the instrumentation is in place whi
contributes to unfavorable outcome in relation to probably loss of lumbar lordosis, and progressil
of degenerative process at adjacent levels6.
MEAFl ODI SCORE FOR RIGID FIXATIOH
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The dynarnic neutralization obtained using this system, should not be considered as an arthrodes
but this device has been advocated to achieve rnore physiological bony fusion. With this system P
bone grafting is necessary therefore donor site rnorbidity can be avoided. Dynesys syste
rnaintains enough stability to prevent further progression of spondylolisthesis (instability).
Even sorne literature3 supports that dynesys systern has limitations in elderly age group wi
osteoporotic bone with severe segmental rnacro-instability, frorn our results we imply that, in old
age group Dynesys has better clinical outcorne cornpare t o Rigid fixation.
Conclusion:
This study supports the belief that the dynarnic system can be used with the sarne indications wi
the rigid in degenerative lurnbar spine because it can offer equally good short-terrn resu
regarding clinical outcorne of surgery, while i t has been previously rnentioned as per our stuc
Dynesys has better outcome in older age group patients, and specific indications like Stenosis al
listhesis5.
Dynesys can be considered as an effective option to rigid stabilization Systems, in terms of patie
based clinical outcorne, and avoidance of complications of rigid system like, screw loosenin
fractures of vertebral body, back pain because of loss of lurnbar lordosis , morbidity related to bo
grafting.
Because of sirnilar clinical and radiological data and no significant rate of cornplications related
either irnplant, in both groups and the relative srnall number of patients included in each group,
is difficult for authors t o rnake any definitive recornrnendation in favor of any instrumentation.
It is very essential to have prospective randornized controlled trial to support practice of evidenc
based medicine.
Reference :
1. Dynarnic stabilization in addition to decornpression for lurnbar spinal stenosis with
degenartive spondylolisthesis, Spine 2006, Feb 15; 31(4): 442-9.
2.
Influence of dynarnic stabilization systern on load bearing of a bridged disc: an in vitro stui
if intradiscal pressure, Eur spine J 2006, Jan 21: 1-10.
3.
Posterior Dynarnic Stabilization System: DYNESYS, Orthopedic Clinic Of North Arnerica,
2005, July; 36(3): 363-72.
4.
Kirkaldy- Willis WH,Farfan H, Instability of the Lurnbar spine. Clin Orthop 982:165:110-23
5.
Application of a dynarnic pedicle screw system for lurnbar segmental degenerationcornparison of clinical and radiological results for different indications, Z Orthop I h r e
Grenzgeb (Gerrnan), 2004 Mar-April; 142(2); 166-73
6.
Rigid, serni rigid versus dynarnic instrurnentation for degenerative lurnbar spinal stenosis:
correlative radiological and clinical analysis of short-terrn results, Spine, 2004 Apr 1; 29
(7): 735-42.
7.
Dynarnic neutralization systern for the spine: a multi Center study of a novel non fusion
systern, Eur Spine J, 2002, Oct; 11.
8.
Dynarnic stabilization devices in the treatrnent of Low Back Pain, Orthopedics Clinic North
Arnerica, 2004, Jan; 35(1): 43-56.
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Journal of Orthopaedics
This is a Peer reviewed paper
Please cite as : Ganesh Natarajan : Cornparative Study of Rigid Versus Dynarnic Spine
Stabilization for Degenerative Lurnbar Spine disorders
URL: http://www.jortho.org/2007/4/3/e7
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