2002 - University of Washington Bone and Joint Sources

Is the Absence of an Ipsilateral Fibular Fracture Predictive of
Tibial Pilon Fracture Severity
DAVID P. BAREI, M.D., F.R.C.S.(C), SEAN E. NORK, M.D., CARLO BELLABARBA, M.D,
AND BRUCE J. SANGEORZAN, M.D.
The management of tibial pilon
fractures remains controversial
and challenging. Axial-loading,
particularly from motor vehicle
collisions or falls from significant
heights, is a common mechanism of
injury. Principles of operative
treatment include reconstruction of the
distal tibial articular surface followed
by restoration of mechanical axes.
Anatomic reduction of the articular
surface along with stable fixation
allowing early motion has been shown
to be the most important predictor of
satisfactory outcome, and should be
prioritized. The ability to obtain
anatomic reduction with stable
fixation, however, decreases with
increasing comminution of the
articular surface.
Fibular fractures are commonly
associated with tibial pilon injuries,
particularly those caused by shearingtype
mechanisms. Other fracture
patterns, however, do not demonstrate
this associated feature. The absence of
an ipsilateral fibular fracture in patients
with tibial pilon injuries may predict a
more severe injury pattern to the tibial
plafond. Presumably, the injurious
energy is completely absorbed by the
tibial plafond resulting in more severe
epiphyseal and metaphyseal injury,
precluding accurate reduction and
worse outcomes. Further, the
deleterious effects of mechanical
impact at the chondrocyte level may
also lead to joint degeneration despite
an accurate reduction. The purpose of
this study is to evaluate the difference
in the radiographic severity of tibial
plafond injuries with fibular fractures
as compared to those without fibular
fractures.
MATERIALS AND METHODS
Between January 1997 and February
2000, 20 consecutive tibial pilon
injuries without associated fibular
fractures were retrospectively identified
using a prospectively gathered trauma
database. Over the same time period,
an age and gender matched cohort of
20 tibial pilon injuries with fibular
fractures were randomly selected. A
computer-based image editing software
program was used to digitize and
conceal the fibula on the initial
anteroposterior (AP) and lateral
radiographs on all 40 injuries. Care was
taken to completely eliminate any
fibular fracture, and associated fibular
malalignment, on both the AP and
lateral views. Every effort was made to
minimize concealment of the tibial
plafond while maximizing the
concealment of the fibula. Radiographs
were then independently rank ordered
(1 = least severe, 40 = most severe) by
three orthopaedic traumatologists
according to the severity of tibial
plafond injury. Observers ranked all
fractures taking into consideration all
the radiographic factors they believe are
important in the assessment of tibial
pilon fracture severity. The observers
were not given any specific guidelines
regarding ranking, but relied on their
significant clinical experience in
managing these fractures. Injuries were
also classified according to AO/OTA
guidelines, which assigns fractures an
alpha-numeric code according to body
region and fracture location. Fractures
affecting the metaphyseal and
epiphyseal portions are divided into A,
B, or C-type groupings, indicating an
extra-articular fracture, partial articular
fracture, or complete articular fracture,
respectively. The premise is that the
increasing alpha assignment indicates
a more severe fracture pattern, and
ultimately a worse prognosis.
RESULTS
Inter-observer agreement was
assessed using the weighted Kappa
statistic (k=0.6). Mean rank scores for
pilon injuries with fibula fractures was
24.4 while those without fibula
fractures was 16.7 (T-test = 0.02). Rank
order was repeated for only AO/OTA
C-type pilon injuries and demonstrated
a mean of 10.3 for those with fibular
fractures and 8.7 for those without
fibular fracture (T-test = 0.5). Mean
rank order for AO/OTA B-type injuries
was 11.1 whereas the mean rank order
for C-type injuries was 24.5 (T-test =
0.001). The proportion of fibula
fractures in B-type versus C-type pilon
injuries was assessed using the Chisquare
statistic (p = 0.006).
DISCUSSION
Operative treatment of tibial pilon
fractures is controversial. Evidence
suggests that increasing comminution
leads to a worse result for a variety of
reasons. Identifying factors that are
associated with a given outcome aid in
clinical decision making. It has been
theorized that the absence of fibular
fractures in association with ipsilateral
tibial pilon injuries may be associated
with a poor outcome. Two different
potential scenarios are suggested: the
first is that the injurious energy is of
lower magnitude and is insufficient to
injure the fibula, or conversely, the
energy is significant but is completely
absorbed by the tibial plafond. To
evaluate this theory, we used the rank
order technique with experienced
traumatologists blinded to the presence
or absence of a fibular injury, who then
independently assessed the
radiographic severity of the tibial pilon
fracture. The kappa statistic
demonstrated satisfactory correlation,
consistent with other published
material on interobserver reliability of
the AO/OTA fracture classification
system. This study demonstrates that,
overall, tibial pilon injuries with fibular
fractures are more severe than those
without fibular fractures. Complete
articular (C-type) injuries, with or
without fibular fractures, are equally
severe. Supporting the OTA
classification, C-type injuries were
consistently ranked as significantly
more severe than B-type injuries. The
presence of a fibular fracture was more
frequently associated with C-type
injury than B-type. This data suggests
that the presence of an intact fibula in
not predictive of a more severe injury
to the tibial pilon, but is predictive of a
less severe, B-type, injury.
2002 ORTHOPAEDIC RESEARCH REPORT 7