PDN PROSTHETIC DISC NUCLEUS: 28 Patient Study Results 28

PDN PROSTHETIC DISC NUCLEUS:
28 Patient Study Results
Björ n Branth, MD
S:t Göran Hospital
Tycho Tullber g, MD
Stockholm, Sweden
Purpose
Evaluate safety and performance of the PDN® Prosthetic
Disc Nucleus in 28 patients with disc herniation and
degenerative disc disease. Patients underwent
surgery between May 1997 and June 2000 and were
implanted utilizing improved surgical techniques, tools,
devices and rehabilitation plan.
Patients
Sex
28
16 M, 12 F
Operative L4/L5 (n =9) L5/L6 (n=1)
Levels
L5/S1 (n=18) (1 at 2 levels)
Blood Loss ~ 61cc.
* 14 enrolled in feasibility study
* Study indications: disc herniation cases with
chronic low back pain (LBP), with or without
leg pain.
Mean Age 36.4 years
Operative Time ~ 95 min.
Fig. 1. PDN
Device
* Majority suffered from LBP from 2+ to 10 years.
* Referred to clinic as fusion candidates.
Fig. 2. Preop
A/P View
Fig. 3. Preop
Lateral View
Fig. 4. Two Day Postop
A/P View
Fig. 5. Two Day Postop
Lateral View
Fig. 6. Six Month Postop
A/P View
Fig. 7. Six Month Postop
Lateral View
Fig. 8. Two Year Postop
A/P View
Fig. 9. Two Year Postop
Lateral View
Materials/Methods
* Implanted in pairs, PDN device is comprised of polymeric hydrogel encased in inelastic polypropylene
jacket. Upon implantation, devices absorb body fluid,
expanding approximately 2 mm in height to act as
spacer, maintaining or restoring disc height and
segmental stability (Fig. 1).
* Patients implanted with PDN device after unilateral
discectomy. As much nucleus material removed as
possible. Two PDN devices inserted and positioned
transversely in disc space.
* In second series of 14 patients, 2 PDN devices were
sutured together.
Findings
At 2 years follow-up there was a 70% (4 patients)
improvement in the Oswestry score and a 70%
(4 patients) improvement in the Visual Analog Scale.
Complications
100.0
Bed Bound
Fig. 10. Oswestry Scores
90.0
80.0
Crippled
70.0
60.0
Severe
Disability
50.0
40.0
Moderate
Disability
Minimal
Disability
30.0
n=14
n=13
n=11
n=12
20.0
0.0
n=10
n=12
10.0
n=2
n=11
Pre-Op
1.5Mo
3Mo
6Mo
1996-1999
40.0
38.9
21.0
1999-Present
45.5
0.0
30.8
Pain is as bad
as it can be
n=2
n=9
n=4
9Mo
12Mo
24Mo
21.2
0.0
11.6
13.0
16.5
13.0
19.0
0.0
Fig. 11. Visual Analog (VAS)
Scores
10.0
9.0
8.0
7.0
6.0
n=14
5.0
4.0
n=6
n=7
3.0
n=7
n=7
2.0
n=7
1.0
No Pain
0.0
n=2
n=11
n=4
n=11
n=2
Pre-Op
1.5 Mo
3 Mo
6 Mo
9Mo
12Mo
24Mo
1996-1999
5.4
3.4
4.6
4.0
0.0
2.4
1.8
1999-Present
6.1
0.0
3.2
1.4
3.5
1.0
0.0
Within the first series of 14 patients, implanted May 1997 to
May 1998, 7 patients (50%) had device displacements due
to either protrusion or extrusion of device (5 patients) or
migration (2 patients), which occurred with device design
no longer being manufactured. Others are believed to
have been due to an operative technique learning curve
and insufficient removal of nucleus material. All displacements occurred within first 2 postoperative months. In the
second series of 14 patients, implanted June 1999 to June
2000, 2 patients experienced complications. One patient:
device protrusion leading to readjustment and fixation of
the device; 1 patient developed infection leading to
removal of both PDN devices.
Conclusions
Early experience with the PDN device showed a high
extrusion rate, which while unacceptable, can be
explained by the changes made to the shape of the device
and typical learning curve in a product development cycle.
The Raymedica PDN implant is a very promising product
that is definitely preferable to fusion for this patient population. This product also allows the option of conversion to a
fusion if needed. Patient selection is critical and early
experience has shown it to be suitable for mild to moderate
DDD while not suitable for severely degenerated discs.