Biomechanical Comparison of Different Volar Fracture
Fixation Plates for Distal Radius Fractures
Kareem Sobky & Todd Baldini & Kenneth Thomas &
Joel Bach & Allison Williams & Jennifer Moriatis Wolf
Received: 14 April 2007 /Accepted: 17 August 2007 /Published online: 7 September 2007
# American Association for Hand Surgery 2007
Abstract The purpose of this study was to compare the
biomechanical properties of four volar fixed-angle fracture
fixation plate designs in a novel sawbones model as well as
in cadavers. Four volar fixed angle plating systems (Hand
Innovations DVR-A, Avanta SCS/V, Wright Medical Lo-
Con VLS, and Synthes stainless volar locking) were tested
on sawbones models using an osteotomy gap model to
simulate a distal radius fracture. Based on a power analysis,
six plates from each system were tested to failure in axial
compression. To simulate loads with physiologic wrist
motion, six plates of each type were then tested to failure
following 10,000 cycles applying 100N of compression. To
compare plate failure behavior, two plates of each type
were implanted in cadaver wrists and similar testing
applied.All plate constructs were loaded to failure. All
failed with in apex volar angulation.The Hand Innova-
tions DVR-A plate demonstrated significantly more
strength in peak load to failure and failure after fatigue
cycling (p value<0.001 for single load and fatigue
failure). However, there was no significant difference in
stiffness among the four plates in synthetic bone. The
cadaveric model demonstrated the same mode of failure as
the sawbones. None of the volar plates demonstrated
screw breakage or pullout, except the tine plate (Avanta
SCS/V) with 1 mm of pullout in 2 of 12 plates. This study
demonstrates the utility of sawbones in biomechanical
testing and indicates that volar fixation of unstable distal
radius fractures with a fixed angle device is a reliable
means of stabilization.
Operative stabilization with restoration of joint congruity is
the recommended treatment for unstable distal radius
fractures.  Techniques described include Kirschner wire
stabilization, external fixation, and internal fixation. [10,
25, 27] Stable fixation permits early functional rehabilita-
tion and may improve long term outcomes.  Plate
fixation of the distal radius fracture placed through a dorsal
approach has been shown to achieve stability and joint
realignment. [2, 6] However, complications including soft
tissue irritation, extensor tendonitis, extensor tendon rup-
ture, and chronic dorsal irritation requiring plate removal
have been documented, particularly with π-type dorsal
plates. [4, 20, 21, 24] More recent studies of lower profile
dorsal plates have shown a lower rate of dorsal tissue
complications, although authors have reported reoperation
for extensor pollicis longus tenolysis  and hardware
removal due to dorsal wrist pain. 
In an attempt to avoid the complications of dorsal plate
placement, volar plating of distal radius fractures has been
advocated. Volar plate designs with fixed-angle locking
technology and lower profiles are thought to enhance
stability and avoid soft tissue complications. [16, 17] One
report with short-term follow-up showed restoration of tilt,
height and inclination, with promising functional outcomes
scores in patients with dorsally displaced and comminuted
distal radius fractures. 
HAND (2008) 3:96–101
K. Sobky:T. Baldini:K. Thomas:J. Bach:A. Williams:
J. M. Wolf (*)
Department of Orthopaedics, University of Colorado Health
4200 E. 9th Avenue, B202,
Denver, CO 80262, USA
The biomechanical properties of both dorsal and volar
plates have been evaluated to analyze plates’ ability to
withstand joint forces and physiologic loading. [1, 3, 7, 11,
14, 18, 19, 28] This analysis has particular relevance in the
immediate post-operative period, where early motion can
potentially prevent complications of stiffness and allow
earlier return to activity. Based on earlier postulated forces
of physiologic load, [8, 29] the majority of these studies
showed that both dorsal and volar plates were capable of
sustaining the forces of early active wrist motion. Only one
previous study was performed in sawbones to standardize the
material; this showed that the dorsal π plate had the greatest
resistance to fracture gap motion, and that locked volar plates
withstood loading better than unlocked volar plates. 
The purpose of this study was to compare the load to
failure of four fixed-angle volar plates with a single static
load and also after cyclical loading, simulating physiologic
wrist motion. A secondary goal was to validate the use of
sawbones as a distal radius fracture model, and thus, a
small cadaver sample was included in our testing to
evaluate the consistency and forces of modes of plate
failure between sawbones and cadaver bone.
Materials and Methods
Left sawbone radii with white plastic cortical shell and
foam cancellous core (#1105, Pacific Research Labs,
Vashon, WA) were used for this study. An unstable, extra-
articular fracture was simulated by making a 10 mm gap
with a saw starting 20 mm proximal to the articular surface
at Lister’s tubercle. The cuts were made perpendicular to
the long axis of the bone to allow for a consistent fracture
gap on the dorsal and volar sides of the radius.
Four volar fixed-angle constructs were tested. These
were (1) Hand Innovations double row DVR-A plate (Hand
Innovations, Miami, FL): (2) Avanta SCS/V (San Diego,
CA); (3) Wright Medical Lo-Con VLS plate (Arlington,
TN); and (4) Synthes volar radius stainless locking plate
(West Chester, PA). Plates from each volar fixation system
were implanted in sawbones in the standard fashion. All
distal fixation holes were used. Group 1 specimens were
fixed with three 3.5-mm bicortical proximal screws and seven
2.0 mm terminally threaded bicortical distal locking screws.
Group 2 specimens were fixed by using three 3.5-mm
bicortical proximal screws and four-fixed angle tines that are
part of the plate (Fig. 1). Group 3 specimens were stabilized
using three 3.5 mm proximal bicortical screws and four
2.7 mm fully threaded bicortical distal locking screws. Group
4 specimens were fixed by using three 2.7 mm proximal
bicortical screws and five 2.0 mm fully threaded bicortical
distal locking screws.
A power analysis was performed using data from a study
of biomechanical differences in sawbones humerus fixation.
 This statistical analysis indicated that to detect a 15%
difference with a 10% standard deviation while assuming a
pattern of intermediate variability among plating techni-
ques, six subjects per group were necessary to achieve
power equal to 0.80, with alpha set at 0.05. 
Each synthetic radius model was potted in methylmetha-
crylate and tested in an Instron (Instron Corporation, Canton,
MA) bi-axial servo-hydraulic test frame (model 1321). Six
plate-radii constructs of each group of specimens were tested
for load to failure by advancing a cobalt chrome sphere
centered over the articular surface at a constant rate of
displacement of 10 mm/min. The sphere was advanced until
the construct failed or the dorsal edges of the fracture met
(Fig. 2). The resultant force was defined as load to failure.
Resulting angle of deformation was measured and recorded.
Stiffness was also calculated from the linear portion of the
load-displacement curve. Six specimens of each group were
then cycled with a repeated load of 100 N for 10,000 cycles,
then tested to failure as above. The choice of a 100 N load
Figure 1 Specimens fixed by using three 3.5-mm bicortical proximal
screws and four-fixed angle tines.
HAND (2008) 3:96–10197 97
was based on previously published papers estimating
physiologic load across the wrist with normal motion. [8, 29]
To compare behavior in sawbones to that in human
cadaveric bone, two of each plating system were implanted
into fresh frozen cadaver radii. After thawing the cadaver
specimens overnight, all of the soft tissues were stripped from
the specimen. Using the same technique as that used in
sawbones, a 20-mm fracture gap was created, and the
cadaverswerepottedinthe samemanner. All eight specimens
were then loaded to failure to evaluate possible differences in
mode of failure and the force required for construct bending.
Load to failure, physiologic force effects on load to
failure, and stiffness were calculated and compared between
groups. Analysis of variance was utilized to evaluate the
differences among the groups.
All plates in all groups failed with apex volar angulation at
the site of the gap created in the specimens. The Hand
Innovations DVR plates showed a significantly higher load
to failure than the Avanta, Lo-con VLS locking, and the
Synthes volar stainless plate (p<0.001; Fig. 3). The Synthes
stainless plates showed significantly higher load to failure
than the Avanta plates (p=0.048). There were no significant
differences between any other groups. For the measured
angle of deformation with failure, the DVR plate showed
a significantly less resulting deformity after single load to
failure than the Avanta, Lo-Con VLS, and Synthes plates
(p<0.001). The Lo-Con VLS had a lesser angle of
deformation than the Avanta tine plate (p=0.044), as did
the Synthes plate (p=0.007). Comparing the Lo-Con VLS
and Synthes stainless volar plates for angle of deformation
showed no differences (p=0.396; Table 1).
The DVR plate showed a significantly higher load to
failure after fatigue loading (10,000 cycles of 100N force
then load to failure) than the Avanta tine plate (p<0.001),
Lo-Con VLS (p<0.001), and Synthes volar plate (p=0.012;
Fig. 4). There were no significant differences when
Figure 3 The Hand Innovations DVR plates showed a significantly
higher load to failure than the Avanta, Lo-Con VLS locking, and the
Synthes volar stainless plate.
Table 1 Average angle (degrees) of deformation for single load to
Plate TypeDVR-A Avanta
Figure 4 The DVR plate showed a significantly higher load to failure
after fatigue loading than the other plates.
Figure 2 Six plate-radii constructs of each group of specimens were
tested for load to failure by advancing a cobalt chrome sphere
centered over the articular surface at a constant rate of displacement
of 10 mm/min. The sphere was advanced until the construct failed or
the dorsal edges of the fracture met.
98 HAND (2008) 3:96–101
comparing the Avanta plate to the Lo-Con VLS (p=0.643),
Avanta to Synthes plate (p=0.335), and Lo-Con VLS to
Synthes volar plate (p=0.161). In the measurement of
bending angle with failure, the DVR plate again showed
significantly less resulting deformity after fatigue failure
than the Avanta, Lo-Con VLS, and Synthes plates (p<0.001,
p<0.001, p=0.021, respectively). Analysis showed no
differences between the Avanta and Wright Lo-Con plate
(p=0.836), Avanta and Synthes plate (p=0.153), and
between the Lo-Con VLS and Synthes stainless plate (p=
0.106; Table 2).
The stiffness of each plate was calculated by fitting a
straight line to the linear portion of the load vs deflection
curve. The slope of the line represented the stiffness of the
plate and the R2 value was noted. ANOVA single factor
data analysis was performed to determine if there was a
significant difference (p<0.05) in stiffness between the four
plate designs tested for single load to failure or fatigue
pretesting before being loaded to failure. All R2 values
were greater than 0.97 showing that the curves could be fit
well with a straight line. The DVR plate showed the highest
stiffness in single loading to failure at 162 N/mm, but was
not significantly stiffer than any of the other three plates
(Fig. 5). The Lo-Con VLS plate demonstrated the highest
stiffness after fatigue loading, but again, this showed no
statistical difference when compared to other groups.
There were no significant differences among the four
plate groups in either load to failure or physiologic load
There were two plates of 12 in the Avanta tine group
that had 1 mm of tine pull out of the distal fragment.
There were no failures of the proximal fixation and no
other evidence of cut out or screw/tine bending or failure
in these constructs. There was no plate breakage across
Cadaver testing was performed with a single load to failure,
with the identical technique used in the synthetic bone
models. The purpose was to evaluate the mode of plate
failure as compared to the sawbones model. All plates
failed with apex volar angulation, similar to plates in
synthetic bone. Peak load to failure was higher in cadaver
bone, with an average of 549 N required for failure in
cadavers and 398 N seen with synthetic bone failure
(Fig. 6). There was no plate or screw breakage of the
cadaver-plate constructs under loading, and no pullout of
either proximal or distal fixation.
One of the purported advantages of volar plating for distal
radius fractures has been the ability to allow patients to
perform early postoperative motion. Evaluation of the
strength and stiffness of volar plates, through biomechan-
ical simulation of the forces across the wrist, tests this
hypothesis. Recent biomechanical investigations have
shown that multiple plating systems appear strong enough
to withstand physiologic force. [11, 13, 15, 18, 19, 28]
The most comprehensive study of distal radius volar
plate biomechanics to date compared the failure properties
and stiffness of ten volar plates,  which included three
of the four plate systems used in this study. The majority of
the biomechanical testing was performed using a wedge
Table 2 Average angle (degrees) of deformation for fatigue failure
Plate TypeDVR-A Avanta
Figure 5 There were no significant differences in stiffness among the
four plate types.
Figure 6 Peak load to failure was higher in cadaver bone compared
to synthetic bone.
HAND (2008) 3:96–1019999
osteotomy model, with a small comparison group of eight
segmental resection. This study showed that stainless steel
plates were stiffer than titanium plates, and that in the
segmental resection model, distal fixation failure was
common. All plates in all groups failed with plate
Willis et al. have published the only study to date
comparing the behavior of volar plates using a sawbones
model.  In this study, four volar plates were compared
to the Synthes π dorsal plate system. Two of the volar
plates were locking plates (Hand Innovations DVR, and
Synthes volar locking plate), but only the DVR used distal
locking technology. This study showed that the Synthes π
plate was significantly stiffer than the volar plates in a
wedge compression radius fracture model, and that the
DVR and volar locking plates were more stiff than the
nonlocking volar plates.
In our study, the use of a sawbones model to test volar
plates in a gap resection construct is novel. Synthetic
sawbones felt to simulate real bone most closely were
chosen to standardize the biomechanical protocol; saw-
bones also offer a cost-efficient model for implant trials.
Quantitative analysis of the angle of deformation confirmed
that the DVR plate had a significantly lower degree of
bending at failure than the Synthes, Wright, and Avanta
plates. Of the four plates tested, the DVR plate had a
significantly higher peak load at failure but did not differ in
stiffness when compared to the other three plates. In clinical
applications, these data would suggest that the DVR can
tolerate higher sustained force through the wrist before
failing. However, the stiffness data are likely more
clinically relevant since the measured forces replicate
physiologic loading more accurately. The similarities in
stiffness across the four plate systems support the idea that
since all four plates performed similarly during gradually
increasing load, with the same degree of displacement, all
provide sufficient fixation to tolerate physiologic forces
during healing. Compared to Koh’s study, only one of the
plate types showed any distal fixation failure, specifically
tine pullout in the Avanta plate.
To validate the sawbones model, a small cadaver study
was also performed. Cadaver specimens were not standard-
ized by densitometry, age, sex, or size. Cadaver construct
behavior was compared to synthetic bone and showed the
same mode of failure and comparable peak loads to failure.
This cadaver model, as a control measure, supports the use
of sawbones for future use in biomechanical studies.
There were several limitations in this study. A different
number of distal fixation points were used with each plating
system, as all possible distal fixation holes were filled.
While this reproduces the actual clinical scenario, the
difference in screw number is a weakness of nonexact
comparison. The comparative cadaver study was small
and thus not amenable to statistical analysis or compar-
ison of the plate constructs, and the specimens were not
This study evaluated four volar plates in peak load to
failure with constant compression and fatigue preloading,
as well as for stiffness of the implants. Our results showed a
significantly higher peak loading force required to deform
the DVR plating system with sustained compressive force
and after physiologic force application. However, there
were minimal differences in stiffness between the DVR,
Lo-Con VLS, Synthes stainless, and the Avanta tine plates.
There was no proximal fixation failure in any of the plates,
and only two of the Avanta plates showed distal fixation
failure. These results indicate that all of these plates can
withstand physiologic loading to allow early wrist range of
motion after surgery for distal radius fractures.
Innovations, Avanta, Wright Medical, and Synthes for donating the
plating systems tested. This work was supported by a grant from the
Dept. of Orthopaedics, UCHSC.
The authors would like to acknowledge Hand
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