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Orthopaedic Surgery Spine
Figure 1: Probability of Not Requiring Re-operation
evaluable patients. The most common procedures were discectomy (47%
of the DuraGen patients, 57% of the standard patients), laminectomy
Re-operation rate curve (excluding patients >27 months elapsed since surgery)
(48% DuraGen, 45% standard) and hemilaminectomy (15% DuraGen,
Kaplan-Meier Curve
1
23% standard). It is of note that, because of multiple procedures, these
percentages add up to more than 100% for each treatment group. The
c
tion
0.75
relative frequencies were similar for the two treatment groups.
0.5 Anatomical Locations
al distribution fun
The most commonly occurring locations were lumbar L4–L5 (61% of the
0.25
DuraGen patients, 43% of the standard patients) and lumbar L5–S1
Surviv
(48% DuraGen, 55% standard). For lumbar L4–L5, the group difference
0
51015 20 25 30 of 18% was not considered to be clinically significant.
Time elapsed (months)
Duragen patients Standard patients
Diagnoses
Of the 430 diagnoses, the most common were ruptured disc (58% of the
Figure 2: Fibrosis in a Patient from the Control Group
DuraGen patients, 77% of the standard patients) and stenosis (42%
DuraGen, 17% standard). Although there was an imbalance, with
relatively more ruptured disc cases in the standard group and more
stenosis cases in the DuraGen group, the differences were not considered
to be clinically important.
Level
Single-level surgery was performed for 65% of the DuraGen patients and
85% of the standard group patients. The difference was not considered
to be clinically important.
Closed Suction Wound Drainage
Figure 3: Patient with DuraGen
®
Without Fibrosis
Wound drainage was reported for about 95% of the patients in each of
the treatment groups.
Primary Efficacy Parameter – Re-operation
The re-operation rate was defined to be the primary parameter. Overall,
re-operation was required for 7/250 (1.5%) of the DuraGen patients and
17/180 (9%) of the standard procedure patients. The difference was
statistically significant (p=0.004). A ‘survival analysis’ was carried out with
the construction of Kaplan-Meier curves and calculation of log rank
statistics. For this analysis, all patients were determined to be followed
from the date of operation to the date of re-operation, or to 1 April 2002
if re-operation was not performed. Thus, patients without re-operation
were considered to be ‘censored’ as of 1 April 2002.
Re-operation Rate Curves
The probability of not requiring re-operation plotted against the number of
months elapsed since initial surgery are shown in Figure 1. These plots were
Patient Disposition and Demographic Profile truncated at 27 months as none of the DuraGen patients were followed for
Treatment groups were similar with regard to age (overall mean age 47.8 longer than that time, while the standard patients were followed for
years, overall range 19–80 years of age), gender (53% male, 47% female) as long as four years. From the curves we note that there was essentially no
and race (100% Caucasian). difference between the groups with regard to the re-operation rate during
the first six months or so following initial surgery. Beyond that time, there
Surgical Characteristics were few additional re-operations required with DuraGen, while
Patients were categorised according to type of surgical procedure, there were many more cases with the standard procedure. A log rank
anatomical location, diagnosis, occurrence of fusion, level of analysis indicated these curves to be statistically significantly different in
procedure and occurrence of closed suction wound drainage. Patients favour of DuraGen (p<0.001).
were permitted to have multiple diagnoses with multiple procedures
performed at multiple anatomical locations. Within the first six months after initial surgery, 4/250 of the DuraGen
patients and 2/180 of the standard patients required re-operation. The
Surgical Procedure similarity in early response rates can be seen in Figure 1. The re-operation
A total of 430 original lumbar procedures were performed on the rates were 3/250 for DuraGen and 6/49 (12%) for the standard group.
56 EUROPEAN MUSCULOSKELETAL REVIEW
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