n Feature Article
Morphological Characteristics of
Posterolateral Articular Fragments
in Tibial Plateau Fractures
Gao Xiang, MD; Pan Zhi-Jun, MD; Zheng Qiang, MD; Li Hang, MD
abstract
Full article available online at Healio.com/Orthopedics. Search: 20130920-16
Treatment of posterolateral tibial plateau fractures is controversial, and information
regarding this specific fracture pattern is lacking. The purpose of this study was to elucidate the frequency and morphological features of posterolateral articular fragments
in tibial plateau fractures.
A retrospective radiographic and chart review was performed on a consecutive series
of patients who sustained tibial plateau fractures between May 2008 and August 2012.
The articular surface area, maximum posterior cortical height, sagittal fracture angle,
and amount of displacement were measured on computed tomography scans using the
Picture and Archiving Communication System. Thirty-six (15%) of 242 injuries demonstrated a posterolateral fracture fragment comprising a mean 14.3% of the articular
surface of the total tibial plateau (range, 8% to 32%). Mean major articular fragment
angle was 23° (range, 62° to 243°), mean maximum posterior cortical height was 29
mm (range, 18 to 42 mm), and mean sagittal fracture angle was 77° (range, 58° to 97°).
The posterolateral plateau articular fracture fragment has morphological characteristics of a conically shaped fragment with a relatively small articular surface area and
sagittal fracture angle. Recognizing these morphological features will help the clinician formulate an effective surgical plan.
Figure: Axial computed tomography scan at the
subchondral level showing a posterolateral (PL)
articular fragment. Point O is the center of the knee
(midpoint of 2 tibial spines), point A is the anterior
tibial tuberosity, point B is the posterior sulcus of
the tibial plateau, point C is the most anterior point
of the fibular head (F), and point D is the posteromedial (PM) ridge of the proximal tibia. Although
a fracture line exists in the posteromedial quadrant
(black arrow), the posteromedial cortex remains
intact and a posteromedial fracture was excluded.
Abbreviations: AL, anterolateral; AM, anteromedial.
The authors are from the Department of Orthopaedic Surgery, the Second Affiliated Hospital,
Medical School of Zhejiang University, Hangzhou, China.
The authors have no relevant financial relationships to disclose.
Correspondence should be addressed to: Pan Zhi-Jun, MD, Department of Orthopaedic Surgery, the
Second Affiliated Hospital, Medical School of Zhejiang University, 88 Jie Fang Rd, Hangzhou, Zhejiang,
310009, China ([email protected]).
doi: 10.3928/01477447-20130920-16
e1256
ORTHOPEDICS | Healio.com/Orthopedics
Posterolateral Articular Fragment in Tibial Plateau Fractures | Xiang et al
P
osterolateral tibial plateau fractures
are difficult to recognize, and, even
when recognized, treatment is dif1
ficult. Information about this specific
fracture pattern is lacking because the
condition has been previously underreported. This is clinically relevant because
it is difficult to detect fracture lines in
the posterolateral corner region on plain
radiography due to the overlapping bony
shadows of the tibial plateau.2
Because the posterolateral fragments
are often covered by the fibular head and
the mass of muscle and tissue are medial
to the fibula, the operative treatment of this
fracture pattern remains a challenge to most
surgeons. Visualization and manipulation
of posterolateral plateau fracture patterns
are difficult when using an anterolateral
or anteromedial approach. To address this
problem, a posterolateral transfibular approach was developed by Solomon et al.3 In
addition to fibular osteotomy, an additional
dissection of the posterolateral ligamentous structures is required. To minimize
soft tissue damage and favor the posterior
buttress plate, Carlson1 and Chang et al4
introduced a posterior approach and, more
recently, Frosch et al5 described a posterolateral approach that does not involve fibular head osteotomy. However, an important
disadvantage to all of these approaches is
that they are associated with a risk of iatrogenic injury to the anterior tibial artery
and cannot be extended distally. Selection
of optimal and rational surgical approaches
to various patterns is controversial.6
The lateral plateau is smaller and higher
than the medial plateau and bears relatively
little stress.7 Clinically, stability in flexion
may be one of the main complications associated with not reducing this fracture,
which may induce abnormal function of
the knee joint.8 However, data on the biomechanical changes of the knee, such as
stress distribution and kinematics behavior,
following this fracture pattern are lacking.
The current authors believe that establishing the frequency, size, and displacement of the posterolateral articular frag-
OCTOBER 2013 | Volume 36 • Number 10
ment should lead to a better awareness of
this injury and improved treatment. They
conducted a retrospective radiographic
and chart review of a consecutive series of
patients with posterolateral tibial plateau
fractures using computed tomography
(CT) scans. The study data may be used
to better model this fragment and may be
useful in formulating and executing a surgical plan for this injury pattern.
Materials and Methods
Between May 2008 and August
2012, a consecutive series of patients
with tibial plateau fractures were identified for a retrospective radiographic and
chart review. The Picture and Archiving
Communication System (PACS) was used
to review the radiographic records. A total
of 278 patients had 281 tibial plateau fractures. Thirty-nine fractures with CT scans
unavailable for review were excluded.
The remaining 242 tibial plateau fractures
formed the study group.
The tibial plateau can be anatomically
classified into the following 4 quadrants
on an axial CT image at the subchondral
level, as previously proposed by Luo et
al9: anterolateral, posterolateral, anteromedial, and posteromedial (Figure 1). In
the current study, the posterolateral fracture fragment was defined as any separate
posterolateral quadrant–based articular
fracture fragment with extension of the
fracture line to the posterolateral cortex
(ie, a break from the posterolateral wall of
the tibial plateau).
Using this criterion, 36 patients with
tibial plateau fractures had an identifiable
posterolateral fracture fragment. The mechanisms of injury were a fall in 9 patients,
electric scooter injury in 8 patients, motor
vehicle accident in 13 patients, blow by a
heavy object in 2 patients, and other causes
(unknown) in 4 patients. The fracture type
was classified according to the AO/OTA
classification, which is dependent on the appearance of anteroposterior radiographs.10
Patients’ demographic data and fracture
classifications are presented in Table 1.
1
Figure 1: Axial computed tomography scan at the
subchondral level showing a posterolateral (PL) articular fragment. Point O is the center of the knee
(midpoint of 2 tibial spines), point A is the anterior
tibial tuberosity, point B is the posterior sulcus of the
tibial plateau, point C is the most anterior point of
the fibular head (F), and point D is the posteromedial
(PM) ridge of the proximal tibia. Although a fracture
line exists in the posteromedial quadrant (black arrow), the posteromedial cortex remains intact and
a posteromedial fracture was excluded. Abbreviations: AL, anterolateral; AM, anteromedial.
Morphological Assessment
The morphological parameters in the
current study were previously proposed
by Barei et al11 and Higgins et al12 and
were determined using PACS software.
These parameters included the major articular fracture angle, surface area of the
fracture fragment as a percentage of the
whole plateau, posterior sagittal fracture
angle, maximum posterior cortical height,
and amount of displacement.
Axial Images
To better describe the morphology of
the articular fracture line, an axial CT scan
was obtained for further investigation. A
quadrant fracture was considered only if
the fracture line extended to the relevant
quadrant cortex at the subchondral level
(Figure 1). The posterior femoral condylar
axis was used as a reference line to assess
the rotation of the lower extremity on the
CT scan. The posterior femoral condylar
axis was developed by a connecting line
tangential to the most posterior aspects
of the femoral condyles (Figure 2A). The
major articular fracture angle was calcu-
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n Feature Article
lated by the major posterolateral articular
fracture line and the posterior femoral
condylar axis at the subchondral level
(Figure 2B). The major articular fracture
angle was considered positive if it was
internally rotated relative to the posterior femoral condylar axis and negative
if it was externally rotated relative to the
posterior femoral condylar axis. The surface areas of the posterolateral articular
fracture fragment and entire tibial plateau
were determined at the same level on the
axial CT slice, and the posterolateral fragment area was divided by the whole plateau area to obtain a percentage (percent
surface area) (Figure 2C).
Sagittal Images
The sagittal fracture angle was subtended by the major posterolateral sagittal fracture line and a line parallel to the posterolateral articular surface (Figure 2D). The
maximum posterior cortical height was
measured from the articular surface to the
most distal aspect of the posterolateral fracture fragment (Figure 2E). Displacement
was defined as the maximum depth between the posterolateral articular fragment
and the remainder of the lateral joint at the
joint surface on the sagittal images. The
displacement was considered major if it
was greater than 5 mm and minor if it was
less than 5 mm (Figure 2F).
Statistical Analysis
All data analyses were performed using SPSS version 16.0 statistical software (SPSS Inc, Chicago, Illinois). The
1-sample Kolmogorov-Smirnov test was
used to test for normality of the distribution. Descriptive statistics were used to
determine morphologic data. Associated
fibular head fractures were statistically
compared with respect to the degree of
displacement. A P value less than .05 was
considered statistically significant.
Results
Thirty-six of 242 patients with tibial
plateau fractures had an identifiable pos-
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terolateral articular fragment, and posterolateral
fractures accounted for
15% of all tibial plateau
fractures. The fracture
had major displacement in 31 patients and
minor displacement in
5 patients, and average
size of the displacement was 10.565.2 mm
(range, 2 to 19 mm).
The posterolateral articular fragment has a
relatively small articular
surface area, and average size of the fragment
relative to the surface
area of the plateau was
14.3%66.3% (range,
8% to 32%). Average
major articular fracture
angle of the posterolateral fracture fragment
plane was 23°624°
(range, 62° to 243°),
which implied a coronal fracture line (Figure
3). Average height
of the fragment was
2967 mm (range, 18
to 42 mm; 90th percentile538 mm) (Figure 4).
Average sagittal angle
was 77°612° (range,
58° to 97°) (Figure 5).
Nine patients demonstrated an associated
fibular head fracture,
which were significantly associated with
displacement of the
posterolateral fracture
fragment (independent
samples t test, P,.05).
Given the high-energy
nature of associated
fibular head fractures
compared with intact
fibular heads, the ob-
Table
Patient Demographics
and Fracture Classification
Patient No./
Sex/Age, y
Side
AO/OTA
Classification10
Quadrant
Involved
1/F/56
R
C1.2
PL, AL
2/F/58
L
C1.2
PL, AL
3/F/63
R
B1.1
PL, AL
4/M/43
R
B3.1
PL
5/F/70
L
B3.1
PL, AL
6/F/58
R
B3.1
PL
7/F/65
L
B3.1
PL, AL
8/F/49
L
C2.2
PL, AL, AM
9/M/53
R
B3.1
PL, AL
10/F/45
R
B3.1
PL, AL
11/M/33
R
B3.1
PL, AL
12/M/42
L
B3.3
PL, AM
13/F/49
L
C3.1
PL ,AL,AM
14/F/68
L
B3.1
PL
15/M/58
L
B3.1
PL, AL
16/F/21
R
C3.2
PL, AM,PM
17/F/65
L
B3.1
PL, AL
18/F/69
L
B3.1
PL, AL
19/M/37
R
B3.1
PL, AL
20/M/57
L
B3.3
PL, AM
21/M/60
R
C3.1
PL, AL, AM
22/M/46
R
B3.1
PL
23/F/33
R
C1.3
PL, PM
24/M/49
L
C3.1
PL, AL, PM
25/F/54
L
B3.1
PL, AL
26/M/40
R
B3.1
PL
27/M/36
R
B1.1
PL
28/M/65
L
B1.1
PL, AL
29/F/66
R
C2.2
PL, PM
30/F/66
R
B3.1
PL, AL
31/M/44
R
B3.3
PL, AL
32/F/45
L
B3.1
PL, AL
33/F/50
L
B3.1
PL
34/F/53
L
B3.1
PL, AL
35/M/46
R
B3.1
PL, AL
36/M/43
R
C2.2
PL, AM, PM
Abbreviations: AL, anterolateral; AM, anteromedial; L, left;
PL, posterolateral; PM, posteromedial; R, right.
ORTHOPEDICS | Healio.com/Orthopedics
Posterolateral Articular Fragment in Tibial Plateau Fractures | Xiang et al
2A
2D
2B
2E
2C
2F
Figure 2: Axial (A-C) and sagittal (D-F) computed tomography scans showing the methods of measuring the posterior femoral condylar axis (A), major articular
fragment angle (B), articular surface area (C), sagittal fracture angle (D), maximum fracture height (E), and displacement (F). Abbreviations: PFCA, posterior
femoral condylar axis.
served difference in the displacement
rates is unsurprising.
Discussion
The morphological characteristics of
posterolateral tibial plateau fractures have
not been widely reported in the literature.
The findings of the current study may provide new insight into this specific fracture
pattern.
The frequency of the posterolateral articular fracture fragment identified in the
current study was 15% of tibial plateau
fractures (36/242), and most of these fragments had major displacement. Clinicians
should be aware that the posterolateral articular fragment is not uncommon in tibial
plateau fractures. Posterolateral plateau
injuries are difficult to assess radiographically on anteroposterior and lateral views,
and full assessment of the fracture morphology requires a CT scan.2 This fracture
OCTOBER 2013 | Volume 36 • Number 10
pattern results from axial loading with the
knee in flexion, and the tibia has a tendency for anterior subluxation on the femur when posterolateral plateau fractures
occur. Carlson1 reported that posterior
bicondylar tibial plateau fractures have
a high association with lateral meniscal
pathology and anterior cruciate ligament
injuries, whereas Waldrop et al8 noted that
the medial static stabilizing structures of
the knee may also be involved with more
applied forces. Preoperative magnetic resonance imaging evaluation of this fracture
pattern would assist with the diagnosis of
meniscal pathology and the possibility of
ligament instability.13,14
Restoration of articular surface congruity is the goal of treatment for tibial
plateau fractures to minimize the longterm risk of posttraumatic arthritis.15,16
Clinically, not reducing this fracture
would lead to knee instability and dys-
function.8 Because the fragments are often covered by the fibula head and ligamentous structures in the corner region
of the popliteus muscle, the question of
how to surgically address this fracture
remains controversial.1,3-6 The findings
of the current study may be useful in
formulating a preoperative strategy. The
posterolateral fragment is potentially
unsecured with the use of a lateral plate
and screw fixation because of its conical
shape and relatively small articular surface area. Average sagittal fracture angle
in this study was 77°, implying a dislocation trend under shear force. A lateral
plate and screw cannot guarantee neutralization of this osteoarticular fragment
under shear force during knee flexion.
From a biomechanical point of view, direct exposure and posterior buttress fixation may be required when managing this
injury pattern.17
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n Feature Article
3
Figure 3: Histogram demonstrating distribution of the major posterolateral
articular fragment angle (MAFA).
Several approaches have been described
for direct exposure and buttress plating fixation of posterolateral fracture patterns, and
authors have deliberated over the merits of
each.1,3-5 However, in all of the described
approaches, the distal limit of dissection is
the location at which the anterior tibial artery perforates the interosseous membrane.
Iatrogenic injury to the anterior tibial artery
can result in ischemic muscle necrosis of
the compartment and skin loss. In a cadaver study, Heidari et al18 reported that the
anterior tibial artery courses through the interosseous membrane at approximately 46
mm distal to the lateral tibial plateau. This
morphologic study showed that the average
height of the posterolateral articular fragment is 2967 mm (range, 18 to 42 mm).18
The current study found that in most cases,
enough distance existed between the fracture and the anterior tibial artery, and iatrogenic injury to the anterior tibial artery
could be avoided by careful manipulation
intraoperatively. However, the anterior tibial artery is usually near the area of exposure, and careful dissection and placement
of retractors is recommended. A good understanding of the surgical anatomy of this
region and the morphology of the fracture
are essential for a successful outcome.
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4
Figure 4: Histogram showing distribution of the maximum fracture height.
Maximum
knee flexion is 60°
and occurs during
the swing phase of
the gait cycle, and
the lateral tibial
plateau bears relatively small compressive
stress
compared
with
the medial plateau.19,20 The lateral femoral condyle
undergoes
significant posterior translation,
including sliding
5
and rolling, during knee flexion, Figure 5: Histogram demonstrating the distribution of the sagittal fracture angle.
and the position
of the tibiofemoral contact area varies with the change in facilitate better modeling of this fragment
the knee flexion angle.21 Therefore, the for future study.
biomechanical role of the posterolateral
The frequency of posterolateral fracfragment differs from that of the media ture patterns may be overestimated in the
plateau, and knowledge of biomechani- current study. Posterolateral articular fraccal changes, such as stress distribution ture fragments will cause posterolateral
and the kinematics behavior at the knee instability of the knee joint if this fracture
following posterolateral fracture, is lack- fragment is not reduced. Therefore, the ining. The data in the current study should clusion criteria in this study included any
ORTHOPEDICS | Healio.com/Orthopedics
Posterolateral Articular Fragment in Tibial Plateau Fractures | Xiang et al
separate posterolateral quadrant–based
articular fracture fragment. Furthermore,
nearly one-quarter of patients (8/36) sustained the fracture in an electric scooter
accident, in which a person’s knee was
flexed at 90° when riding. This mode
of transportation may not be as popular elsewhere. However, the authors do
not believe that this limitation presented
bias during analysis of the morphological
characteristics of this specific fracture.
4. Chang SM, Zheng HP, Li HF, et al. Treatment of isolated posterior coronal fracture of
the lateral tibial plateau through posterolateral approach for direct exposure and buttress
plate fixation. Arch Orthop Trauma Surg.
2009; 129(7):955-962.
13. Stallenberg B, Gevenois PA, Sintzoff SA Jr,
Matos C, Andrianne Y, Struyven J. Fracture
of the posterior aspect of the lateral tibial plateau: radiographic sign of anterior cruciate
ligament tear. Radiology. 1993; 187(3):821825.
5. Frosch KH, Balcarek P, Walde T, Stürmer
KM. A new posterolateral approach without
fibula osteotomy for the treatment of tibial
plateau fractures. J Orthop Trauma. 2010;
24(8):515-520.
14.Lee J, Papakonstantinou O, Brookenthal
KR, Trudell D, Resnick DL. Arcuate sign
of posterolateral knee injuries: anatomic,
radiographic, and MR imaging data related
to patterns of injury. Skeletal Radiol. 2003;
32(11):619-627.
Conclusion
7. Martelli S, Pinskerova V. The shapes of the
tibial and femoral articular surfaces in relation to tibiofemoral movement. J Bone Joint
Surg Br. 2002; 84(4):607-613.
Posterolateral plateau fracture patterns
have morphological features of a conical
shape and relatively small articular surface area and sagittal fracture angle.
Recognizing these morphological features
will help clinicians formulate an effective
surgical plan.
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OCTOBER 2013 | Volume 36 • Number 10
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