Baldwin, Evan

Brantley, Justin

Clark, James

Mercer, Deana

Salas, Christina

Taha, Mahmoud Reda

English

University of New Mexico

University of New Mexico
UNM Digital Repository
Hand and Wrist Orthopedics
3-15-2014
Patterns of failure in the distal radius following
treatment for extra-articular fractures (AO
23-A3.2) using two-column volar plates
Christina Salas
Justin Brantley
James Clark
Evan Baldwin
Mahmoud Reda Taha
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Recommended Citation
Christina Salas, Justin Brantley, James Clark, Evan Baldwin, Mahmoud Reda Taha, Deana Mercer. Patterns of failure in the distal radius
following treatment for extra-articular fractures (AO 23-A3.2) using two-column volar plates. Poster presented at: ORS 2014 Annual
Meeting; Mar 15-18 2014; New Orleans, LA
Authors
Christina Salas, Justin Brantley, James Clark, Evan Baldwin, Mahmoud Reda Taha, and Deana Mercer
This poster is available at UNM Digital Repository: https://digitalrepository.unm.edu/hand_wrist/13
  
 
 
 
 
 
 
                         A 
 
 
 
 
 
 
 
 
                             B 
 The distal radius is the most common fracture site in 
the upper extremity. 
 Dorsally displaced, unstable fractures are commonly 
treated with locked plate fixation using a volar 
approach. 
 Damage analysis of matched paired specimens with 
simulated AO 23-A3.2 fracture treated with volar 
plating may provide information on whether implant 
geometry may affect fracture stability. (Fig. 1) 
Patterns of Failure in the Distal Radius Following Treatment for Extra-Articular 
Fractures (AO 23-A3.2) Using Two-Column Volar Plates 
Christina Salas, MS1,2; Justin Brantley, BS1,2; James Clark, MD1; Evan Baldwin, MD1,3; Mahmoud Reda Taha, PhD2,4; Deana Mercer, MD1  
1. Department of Orthopaedics and Rehabilitation  
2. Center for Biomedical Engineering  3. Department of Surgery 
4. Department of Civil Engineering 
 The University of New Mexico, Albuquerque, USA 
 The purpose of our study was to characterize the 
damage accumulated in a model of extra-articular 
distal radius fracture with dorsal comminution 
treated using two-column volar distal radius plates 
during a simulated post-operative healing period. 
Patterns of failure of the bone and implant are 
reported from cyclic testing and ramped load to 
failure experiments.  
 Ten matched pairs of fresh-frozen, cadaveric distal 
radii were used in this study: 
 
 One radius from each donor was randomized to Group 
I; the contralateral limb from the same donor assigned 
to Group II 
 Group I:  Prepared with Geminus® volar distal radius 
plating system by Skeletal Dynamics. (n=10) This 
implant uses a dual head design for independent two-
tier scaffolding. (Fig. 2A) 
 Group II: Prepared with Acu-Loc® 2 Proximal Volar 
Distal Radius Plate by Acumed. (n=10) This implant 
uses a single head design for enhanced ulnar 
butressing. (Fig. 2B) 
INTRODUCTION 
PURPOSE 
METHODS 
RESULTS 
 METHODS 
CONCLUSIONS 
RESULTS 
 Structural damage, though greater in Group II 
specimens during low cycle loading, did not 
significantly affect the ultimate failure force of the 
bone/implant constructs 
 In order to determine the cause of the low-cycle 
structural damage to Group I and Group II 
specimens, a patient-specific computational analysis 
is underway, developed using pre-study calibrated 
quantitative computed tomography scans of the 
bones and solid models of the implants  
 Group II specimens experienced significantly more 
damage under cyclic loading than Group I 
specimens. (0.78+/-0.11 and 0.66+/-0.10, respectively; 
p=0.02) (Fig. 4A, Fig. 4B) 
 One specimen in Group II experienced coronal 
fracture of the dorsal pole of the lunate during cyclic 
loading and was excluded from load to failure tests. 
 Group I specimens were significantly stiffer than 
group II specimens. (481.47+/-161.37 N/mm and 
337.90+/-112.04 N/mm, respectively; p=0.04) (Fig. 4C) 
 Ultimate force at failure in Group I (1268.50+/-307.69 
N) and Group II (1025.63+/-496.45 N) specimens was 
not significantly different (p=0.11) (Fig. 4D) 
 If a patient is subject to high impact loading of the 
distal radius (fall on outstretched hand) prior to the 
end of their post-operative healing period, both 
implants may provide equivalent resistance to 
fracture 
 Should the post-operative healing period be delayed, 
it is likely that increasing damage may lead to 
fracture with Group II implants; high frequency 
fatigue testing is necessary to confirm  
ACKNOWLEDGEMENTS 
FIG. 5 
FIG. 4 
 This project was supported in part by the National 
Center for Advancing Translational Sciences of the 
National Institutes of Health through grant number 
UL1 TR000041. The content does not necessarily 
represent the official views of the NIH. 
Figure 1: A. Extra-articular multi-fragmentary fracture of the distal 
radius with angulated dorsal wedge fragment (AO 23-A3.2). B. 
Radiographic depictions of AO 23-A3.2 fracture. 
A B 
Figure 2: A. Group I radius plated with Geminus® volar distal radius 
plate from Skeletal Dynamics. B. Group II radius plated with Acu-Loc® 2 
proximal volar distal radius plate from Acumed. 
Figure 4: A. Representative force-displacement hysteresis curves of a 
single specimen from Group I and contralateral limb in Group II. B. 
Representative damage plots. C. Stiffness results from load-to-failure 
testing. D. Ultimate failure force results from load-to-failure testing. 
CLINICAL RELEVANCE 
 Damage (D), which defines the period between a state 
of material perfection and the onset of crack 
initiation, was calculated using the effective Modulus 
of Elasticity (         ) from hysteresis data (Fig. 3B)  
                      , where               is calculated at cycle 5;             
 is calculated at every 500th cycle 
 Constructs not failed during cyclic loading were 
subject to a ramped load to failure at 1mm/s 
 A matched-paired t-test was used to determine 
statistical significance (p=0.05)  
Figure 3: A. Experimental testing fixture. B. Figure depicting axial 
loading for calculation of effective Modulus of Elasticity. 
 A custom fixture was designed to apply a 60/40 ratio 
through scaphoid and lunate facets. (Fig. 3A)   
 Specimens were subject to cyclic axial loading; 
sinusoidally compressed from 75-250N at a rate of 1 
Hz for 5,000 cycles 
D 
L 
P 
P 
A 
A B 
 Specimens failed by distal fragment collapse leading 
to plate bending (Group I n=5/10; Group II n=2/9) and 
fracture of the lunate facet (Group I n=5/10; Group II 
n=7/9) 
 
A 
 
B 
 
C A B 
0
500
1000
1500
2000
1 2 3 4 5 6 7 8 9
U
lt
im
a
te
 f
o
rc
e
(N
) 
Group I Group II
D 
0
100
200
300
400
500
600
700
1 2 3 4 5 6 7 8 9
S
ti
ff
n
e
s
s
 (
N
/m
m
) 
Group I Group II
C 
0
50
100
150
200
250
300
0 1 2 3 4
F
o
rc
e
 (
N
) 
Displacement (mm) 
Group I Group II


Patterns of failure in the distal radius following treatment for extra-articular fractures (AO 23-A3.2) using two-column volar plates

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Patterns of failure in the distal radius following treatment for extra-articular fractures (AO 23-A3.2) using two-column volar plates

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