Minimally invasive (sinus tarsi) approach for calcaneal fractures
Wang et al. Journal of Orthopaedic Surgery and Research
Minimally invasive (sinus tarsi) approach for calcaneal fractures
Zhe Wang 1
Xiu Hui Wang 0
Sheng Long Li 2
Xin Tang 1
Bei Gang Fu 0
Ming Hui Wang 0
Sheng Li Xia 0
0 Department of Orthopedics, Shanghai Zhoupu Hospital , Pudong New Area 1500, Rd Zhouyuan, Zhoupu, Shanghai 201318 , China
1 Department of Orthopedic Trauma, The First Affiliated Hospital of Dalian Medical University , 222, Rd Zhongshan, Xigang District, Dalian, Liaoning Province 201318 , China
2 Department of Orthopedics, Dalian Central Hospital, Dalian Medical University , Dalian , China
Background: According to the anatomic characteristics of the calcaneus and the sinus tarsi approach, we designed a combined plate. The goal of this study was to retrospectively assess the functional outcomes and complications of treatment with our self-designed plate. Methods: From March 2014 to October 2015, 18 patients with closed calcaneal fractures (14 Sanders type II and 4 type III) were treated with our combined locking plate through a minimally invasive sinus tarsi approach. All patients underwent both clinical and radiological evaluations. Results: The follow-up duration for all patients ranged from 6 to 13.5 months. The radiographs demonstrated significant corrections of the calcaneal width, length, height, Böhler angle, and Gissane angle from preoperatively to 3 months postoperatively and the last follow-up. However, there were no significant differences in the variables between 3 months postoperatively and the last follow-up. The mean Maryland foot score was 88.1 ± 8.8, in which excellent outcomes were achieved in 11 patients, good in 4, and fair in 3 (excellent and good rate, 83.3% (15 of 18)). No statistical significances in the mean Maryland foot score (88.1 ± 8.8 vs 87.8 ± 10.1, p = 0.9), and the excellent and good rate (85.7 vs 75.0%, p = 1.0) was found between type II and type III fractures. No complications were observed in all fractured feet. Conclusion: Treatment with our self-designed combined plate through a sinus tarsi approach may be safe and effective for type II and type III calcaneal fractures.
Calcaneal fractures; Sinus tarsi; Combined plate fixation
Fractures of the calcaneus are commonly encountered
clinical injuries resulting from high-energy trauma. They
account for 1 to 2% of all fractures and 60% of all tarsal
fractures. According to the results of the computed
tomography (CT) scanning, the calcaneal fractures can be
classified into four categories, among which the Sanders
types II and III fractures are the most common types .
Thus, the development of effective and safe treatment
strategies for these two fracture types has always been a
hot issue among orthopaedic surgeons .
Currently, open reduction and internal fixation
through the lateral L-shape extensile incision has been
considered as the gold standard surgical therapy for
calcaneal fractures. This approach provides a large
view to expose the fractures, allowing accurate
reduction of the deformed posterior facet and convenient
placement of the plate to achieve a stable fixation.
However, the high incidence (approximately 30%) of
complications associated with this approach, including
wound dehiscence and deep infection, remains a
nonnegligible problem [3, 4].
To lower the wound complications, a minimal incision
approach at the sinus tarsi has been proposed. Several
randomized controlled trials have demonstrated a
similar reduction; however, a significantly decreased risk of
wound complications can be obtained with this procedure
in comparison with the lateral extended approach [5, 6].
Nevertheless, the poor visualization of the lateral wall of
the calcaneus through this small incision makes it difficult
to insert the conventional plate for obtaining a stable
fixation. Thus, the development of a plate that is adaptable
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to the anatomic characteristics of the calcaneus and sinus
tarsi approach is important [6, 7].
In the present study, we self-designed a new,
combined, anatomical plate specifically for Sanders type II
and type III fractures and aimed to retrospectively assess
the functional outcomes and complications of its use
through the sinus tarsi approach.
This study was approved by the Institutional Review
Board of the First Affiliated Hospital of Dalian Medical
University, and all patients provided written informed
consent for the surgery and for this study. We
retrospectively reviewed the clinical data of patients with
calcaneal fractures who were treated by using a minimally
invasive sinus tarsi approach in the First Affiliated
Hospital of Dalian Medical University between March
2014 and October 2015. The eligible patients met the
following inclusion criteria: (1) age >18 years; (2) with
closed fracture of the calcaneus; (3) with Sanders types
II or III fractures ; (4) with fractures fixed by using
our newly self-designed combined locking plate; and (5)
with a minimum of 6 months of clinical follow-up.
Patients with history of calcaneal, ankle, or other foot
fractures were excluded.
Our self-designed combined plate
The plate (GJPS(I)67; 1.5 mm in thickness and 13 mm
in width; made of titanium alloy owing to the better
biocompatibility, flexibility, and a lower resonance of this
material ; Puwei Medical Instrument Co., Ltd, Shanghai,
China; patent no. ZL 2014 2 0269654.X) consisted of two
sheets, mutually independent fixed arms (forearm, 42 mm
in length; rear arm, 39 mm in length), a coupling screw,
and six locking screws (Fig. 1). There are three screw holes
in the forearm/rear arm to lockingly fix the anterior process
of the calcaneus, calcaneal body, and bones behind
the calcaneal body, respectively. The head end of the
forearm/rear arm is of streamlined shape, whereas the
tail end can be linked by the coupling screw through
their chimeric structure.
Analysis of the biomechanical properties of our combined
The biomechanical characteristics of our self-designed
combined plate were tested by Biomechanics Laboratory
of Changzhou Waston Medical Appliance Company
(Changzhou, China) by using the standard
electro-mechanical testing machine (Instron ElectroPuls E10000;
Instron Systems, Norwood, MA, USA) equipped with a
10-kN Instron load cell. The vertical load-bearing capacity
of the combined plate was tested under static (in which
the loading rate was 2 mm/min and the maximum load
was recorded by monitoring the force-displacement
curves) and dynamic (performed in load-controlled mode
Fig. 1 Structure of our self-designed combined plate
Fig. 2 The biomechanical testing for the plate. a, b Vertical load-bearing
test. c, d Resistance to bending load test
with sinusoidal wave at a frequency of 5 Hz and maximum
load of 500 N) conditions (Fig. 2a, b). For the resistance to
bending loads, the force-displacement curve was also
monitored and the load to failure was recorded at the
loading velocity of 2 mm/min and with the span of
30 mm (Fig. 2c, d).
All procedures were performed by the same surgeon
(Zhe Wang) as previously described [6, 7, 9]. After
admission, the affected feet of the patients were fixed by
using a plaster or provisional brace and elevated to
prevent the exacerbation of injuries in the soft tissues that
can be induced by activity. For patients with slight
damages to the soft tissue, the surgery was scheduled within
48–72 h; however, for patients with severe tissue
damages (accompanied by obvious swelling and tension
blisters), the surgery was arranged after 7–10 days to
confirm the reduction of swelling, improvement of soft
tissue condition, and a positive wrinkle test. This led to
a mean interval from injury to surgery of 4.7 ± 2.4 days
(range, 2–9 days).
Surgery was performed with the patients placed in a
lateral decubitus position under epidural or
subarachnoid anaesthesia (Additional file 1). An electric
pneumatic tourniquet (pressure, 45 KPa) was used on the
affected limb to reduce blood loss and improve the
operative field visually. One or two Steinmann pins were
first drilled from the calcaneus to the head of the talus
to correct the Böhler angle and restore the Gissane
angle, which was confirmed under C-arm fluoroscopy.
Then, a 3–4-cm incision was made over the sinus tarsi
(beginning from the tip of the lateral malleolus to the
proximal cuboid) to expose the lateral cortex of the
anterior process of the calcaneus (carefully, to avoid
injuring the lateral sural cutaneous nerve, peroneus
longus, and brevis tendon) (Fig. 3a, b). Subsequently, a
subcutaneous tunnel was created by using a small
periosteal elevator in the above incision, and our
selfdesigned plate was inserted to the corresponding
position of the lateral wall of the calcaneus, which was
temporarily held in place with two Kirschner wires
(Fig. 3c, d). After a satisfactory reduction was achieved
under C-arm fluoroscopy, six locking screws and a
coupling screw were screwed followed by the removal of the
Steinmann pin and closure of the incision in layers.
Postoperative management and evaluation
Postoperatively, prophylactic antibiotics were given to
prevent surgical site infection and plaster immobilization was
performed to protect the wound. The patients were
encouraged to do toe flexion and dorsiflexion exercises 24 h
after the operation. Stitches were removed after 2 weeks
of surgery, and weight bearing was gradually advanced to
regain full range of motion and strength at 4 weeks after
surgery, during which the plaster cast was removed.
The operative data were recorded, including operative
time (min; measured from the cut to the suture of the
incision), hospital stay (days), cumulative intraoperative
radiation time (min; provided by the fluoroscopic
Fig. 3 Intraoperative pictures of the sinus tarsi approach. a Marking for the sinus tarsi approach (solid line). b Incision over the sinus tarsi and
subcutaneous tunnel created by using a small periosteal elevator. c Schematic diagram of plate placement. d Placement of our self-designed
combined plate through the sinus tarsi approach
apparatus), fracture healing time (days), and the
incidence of complications. Fracture healing was defined as
the bridging of the trabecular bone and the
disappearance of the trabecular fracture line on the radiograph.
The lateral and axial radiographs were also obtained
preoperatively, postoperatively, and at the last follow-up to
judge the reduction of the calcaneus, including the
Böhler angle (i.e. the angle between the line drawn from
the highest point of the anterior process to the highest
point of the posterior facet and the line tangent to the
tuberosity); Gissane angle (i.e. the angle between the line
tangent to the articular surface of the medial posterior
facet and the line of the anterior end of the posterior
facet to the dorsal edge of the calcaneocuboid facet);
calcaneal height (i.e. the perpendicular distance from the
inferior cortex of the calcaneus to the top of the medial
posterior facet); calcaneal width (i.e. the distance
between the external cortex of the medial malleolus and
the lateral cortex of the most lateral calcaneal fracture
fragment); and calcaneal length (i.e. the orthogonal
distance from the most posterior aspect of the calcaneus to
the most distal edge of the calcaneocuboid joint) [10, 11].
The clinical functional outcomes were assessed by using
the Maryland foot score (MFS), which is a 100-point
scoring system with 40 points for function, 45 points for pain,
10 points for cosmesis, and 5 points for movement of the
ankle, subtalar, midfoot, and metatarsophalangeal joints.
The scores were defined as follows: 90–100 excellent,
75–89 good, 50–74 fair, and <50 poor . All data
collection and measurement procedures were performed by Zhe
Wang and checked by Sheng Long Li. Measurement
of reduction parameters was accomplished with the
All data are expressed as n (%) or mean ± standard
deviation (SD) and analysed by using SPSS 18.0 statistical
software (SPSS Inc., Chicago, IL, USA). The preoperative
and postoperative radiological results were compared by
using paired Fisher’s exact test (because of an expected
frequency of <5), and an independent t test was used to
compare the functional outcomes between the different
Sanders classifications. A value of p < 0.05 was
considered to indicate a significant difference.
Patient demographic and fracture characteristics
From March 2014 to October 2015, 18 patients (14 men,
4 women) with calcaneal fractures were enrolled in this
study. Their average age at the time of the calcaneal
fracture was 50.4 ± 10.1 years (range, 32–66 years). The
mechanism of injury was falling from a height in 14
cases, traffic accidents in 2 cases, strike injury in 1 case,
and others in 1 case. All fractures were unilateral, with
the left side involved in 7 cases and the right side in 11
cases. In addition, the lumbar vertebral, clavicular, and
ankle fractures were complicated in 1 case. Six patients
had a >5 years smoking history and one patient had a
history of excessive consumption of alcohol, and they
were advised to stop smoking and abstain from alcohol
until wound healing; on the other hand, two patients
had diabetes, and their blood glucose was controlled
to prevent complications [13, 14]. According to the
Sanders CT scan classification system, there were 14
feet with type II fractures (8 type IIA, 4 type IIB, and
2 type IIC) and 4 feet with type III fractures (2 type
IIIAB, 1 type IIIAC, and 1 type IIIBC) (Table 1,
Additional file 2: Table S1) .
The analysis of biomechanical properties demonstrated
that the plate could bear 1396.03 N in maximum vertical
Table 1 Demographic data of 18 patients with calcaneal fractures
Falling from a height
Complicated other fractures
Excessive consumption of alcohol
Fig. 4 Representative curve for biomechanical testing of our combined plate. A gradual increase in stress with a sudden decrease in displacement
indicated structural failure. a Curve for the vertical load-bearing test. c Curve for the resistance to bending load test. b, d Plate breakage
load-bearing capacity and 427.15 N in maximum
resistance to bending loads (Fig. 4). Under a cyclic loading of
500 N, plate breakage was observed after 93,003 cycles.
The surgery was successful in all patients, with a mean
operative time of 64.4 ± 8.0 min (range, 50–80 min),
mean radiation time of 13.0 ± 3.5 s (range, 8–21 s), and
mean hospital stay of 8.9 ± 2.2 days (range, 5–13 days).
The radiographs showed that all fractures healed
uneventfully, with a mean time to bone union of 89.3 ±
11.0 days (range, 75–113 days). The radiographs also
demonstrated adequate reduction of the fracture
(Table 2, Additional file 2: Table S1), with the calcaneal
width, length, height, Böhler angle, and Gissane angle
significantly corrected from preoperatively to 3 months
postoperatively and the last follow-up (range, 6–13.5 months;
mean, 9.3 ± 3.7 months). However, there were no significant
differences when comparing the calcaneal width, length,
height, Böhler angle, and Gissane angle between 3 months
Table 2 Radiological results before and after operation
Böhler angle (o) Gissane angle (o)
Three months postoperative
after the operation and at the last follow-up,
indicating that this reduction effect can be maintained but
not lost during follow-up. The overall mean MFS was
88.1 ± 8.8, in which excellent outcomes were achieved
in 11 patients, good in 4, and fair in 3 (excellent and
good rate, 83.3% (15 of 18)). Further comparison
between type II and type III fractures showed no
statistical significances in the mean MFS (88.1 ± 8.8 vs
87.8 ± 10.1, p = 0.9) and in the excellent and good rate
(85.7 vs 75.0%, p = 1.0), suggesting that our
selfdesigned plate may be equally effective for these two
types of fractures (Table 3, Additional file 2: Table S1).
Moreover, no screw loosening and screw or plate
breakage was observed, and none of the patients
developed incision infection, poor wound healing, and
other complications during the follow-up, proving the
favourable safety profile of the plate. Radiographs of three
typical cases (case 1, Fig. 5a–f; case 2, Fig. 6a–h; case 12,
Fig. 7a–h) were provided to illustrate the preoperative and
There was no statistical difference between the 3-month postoperative group and the last follow-up group
*p < 0.01, compared with the preoperative group
Table 3 Function outcome scores
Mean ± SD Excellent (%) Good (%) Fair (%) Poor (<50)
(90–100) (75–89) (50–74)
Sanders II 88.1 ± 8.8
Sanders III 87.8 ± 10.1 3 (75.0)
The use of open reduction through a minimally invasive
sinus tarsi approach and stabilization with a locking
plate is now a widely accepted treatment for calcaneal
fractures [5–7, 15, 16]. However, all the currently used
locking plates are in one piece, which requires a large
working space for placement, leading to the necessity of
sufficient exposure of the lateral wall of the calcaneus
and even establishment of assisted incision . This may
increase the injuries to the soft tissues and the risk of
wound complications. In addition, simultaneous fixation
of multiple fracture blocks also induces difficulty in
operation, easily causing poor anatomic reduction [5, 17].
To minimize the above problems, we newly designed
and patented a combined plate in 2014. Our plate can
be inserted through the sinus tarsi incision by using only
appropriate dissection of subcutaneous tissues and the
periosteum, without the need for the creation of a
complete subcutaneous tunnel . The streamlined
shape of the head end can reduce the injuries to the
surrounding soft tissues, whereas the chimeric structure of
the tail end with a coupling screw can form a triangle
support with the anterior and posterior calcaneus, which
are respectively fixed with three locking screws, thus
providing a rigid fixation and avoiding reduction loss.
Furthermore, the angle between the forearm and the
rear arm was set to 130°, with reference to the normal
ranges of the Böhler angle (20–40°) and Gissane angle
(110–140°), as well as the biomechanical characteristics
of the calcaneus, by which the maximum area can be
fixed under sufficient axial stress resistance and the risk
of plate breakage can be decreased. We hypothesized
that our combined plate may be effective and safe for
the management of calcaneal fractures.
The present study aimed to preliminarily confirm the
treatment outcomes of the plate for calcaneal fractures,
by retrospectively collecting our clinical data, which, to
our knowledge, have not been reported. As expected,
our results demonstrated that the Böhler angle, Gissane
angle, calcaneal height, width, and length were all
significantly corrected postoperatively, without any
accompanying postoperative wound complications and implant
loosening during the follow-up. Our results seemed to
be superior to those of the study by Kikuchi et al. ,
Fig. 5 A 52-year-old male patient was admitted to our hospital because of pain and swelling on the right foot after falling from a height. Preoperative
lateral (a) and axial (b) radiographs showing the right calcaneal fracture, with reduced Böhler angle (16.75°), Gissane angle (91.39°), calcaneal length
(58.23 mm), and calcaneal height (38.59 mm) but increased calcaneal width (38.59 mm). Preoperative horizontal (c) and coronal (d) computed
tomography images showing a Sanders IIC fracture. Postoperative lateral (e) and axial (f) radiographs showing obvious corrections of the Böhler angle
(23.17°) and Gissane angle (124.4°) and improvements in calcaneal length (70.28 mm), height (35.6 mm), and width (35.54 mm)
Fig. 6 A 45-year-old male patient was admitted to our hospital because of pain and swelling on the left foot after falling from a height. Preoperative
lateral (a) and axial (b) radiographs showing the left calcaneal fracture, with reduced calcaneal height (34.5 mm) and length (62.3 mm) but increased
calcaneal width (39.4 mm). Preoperative horizontal (c) and coronal (d) computed tomography images showing a Sanders IIA fracture with a bulked
lateral wall. Postoperative lateral (e) and axial (f) radiographs showing obvious corrections of the calcaneal height (38.6 mm), length (67.5 mm), and
width (39.3 mm). Postoperative lateral (g) and axial (h) radiographs showing excellent fracture union, with a Maryland foot score of 88
Fig. 7 A 41-year-old male patient was admitted to our hospital because of pain and swelling on the right foot after falling from a height. Preoperative
lateral (a) and axial (b) radiographs showing the right calcaneal fracture, with reduced Böhler angle (17.37°) and Gissane angle (97°). Preoperative
horizontal (c) and coronal (d) computed tomography images showing a Sanders IIA fracture with a bulked lateral wall. Postoperative lateral (e) and axial
(f) radiographs showing obvious corrections of the Böhler angle (23.17°) and Gissane angle (124.4°). Postoperative lateral (g) and axial (h) radiographs showing
excellent fracture union, with a Maryland foot score of 87
in which the sinus tarsi approach was also used: three of
their cases (13.6%) had superficial wound infections, and
no statistical differences were present in the Gissane
angle, calcaneal height, and calcaneal length between
preoperatively and postoperatively. Moreover, in the
study of Basile et al., three patients (7.9%) who
underwent the sinus tarsi approach failed to achieve anatomic
reduction . These findings indicated the effectiveness
and safety of our plate for calcaneal fractures.
Better reduction of the calcaneus may result in better
recovery of foot function. As anticipated, our findings
indicated that the mean MFS reached 88.1 ± 8.8, with an
excellent and good rate of 83.3% (15 of 18). This result
seemed to be comparable with, but not higher than, that
of previous studies [6, 7]. We believe that this may be
attributed to the small sample size (18 vs 33) and shorter
follow-up (9.3 ± 3.7 vs 21 ± 8.9 months) .
In line with the simple and convenient procedure for
placing our plate, the operative time was obviously
reduced in our study when compared with previous
studies (64.4 ± 8.0 vs 69 ± 14.6 min ; 64.4 ± 8.0 vs 122.15 ±
8.32 ), which may possibly further decrease the
infection rate and promote fracture healing, resulting in a
shorter hospital stay. Furthermore, it had also been
demonstrated that the radiation exposure time in our study
was dramatically shorter than that in the study by Cao
et al.  (13.0 ± 3.5 s vs 3.6 ± 0.5 min). Thus, the use of
our plate may prevent radiation-associated toxicity in
surgeons and patients, further indirectly demonstrating
the safety of our procedure.
The severity of closed calcaneal fractures is known to
be negatively correlated to the subsequent foot function
reduction and the quality of life after open reduction
and internal plate fixation . Thus, we also compared
the MFS between Sanders types II and III calcaneal
fractures. However, the results indicated a similar outcome,
demonstrating that our self-designed plate may be
equally suitable for these two types of fractures.
However, further studies are still needed to prove our
conclusion because of the small number of included patients
with Sanders type III calcaneal fractures.
By summarizing our clinical experience, we consider
that the indications for our plate treatment are as
follows: (1) Sanders type II or simple type III fracture; (2)
uneven articular surface, with displacement ≥1 mm; (3)
loss of calcaneal height >1.5 cm and increase of
calcaneal width >1 cm; (4) Böhler angle ≤20°, Gissane angle
≤100° or ≥130°; or (5) calcaneal varus angle ≥50° and
eversion ≥10°. However, there are still some limitations
in our technique. For example, percutaneous cannulated
screw fixation is still needed as an assisted reduction for
the treatment of Sanders type III calcaneal fractures with
involvement of the sustentaculum tali or extra-articular
calcaneal fractures (e.g. beak/avulsion fracture of the
calcaneal tuberosity). Further optimization of our
combined plate is still necessary.
Our study has some limitations. First, this was a
retrospective review and the patients were not randomized to
receive our surgery. Thus, the choice of surgery might
be biased by surgeon preference and patient factors.
Second, we did not have a control group, which made
our comparison inconclusive. Third, our sample size of
18 was relatively small and the follow-up was short,
which may have led to the underestimation of the
complication rate and long-term reduction effect. Fourth, we
preliminarily assessed the biomechanical properties of
our combined plate but did not conduct a confirmation
with a cadaver study or with bone models. Therefore,
further investigation is still essential to obtain a more
precise efficacy evaluation, by conducting a biomechanical
study in human cadavers or bone models, or by means of
a clinical study with a large sample size, longer follow-up
time, and a randomized control (with other plates).
Our present study suggests that the minimally invasive
sinus tarsi approach with our combined plate may be a safe
and effective alternative for the operative treatment of type
II and simple type III calcaneal fractures, with rare
postoperative complications and excellent reduction capacity.
Additional file 1: Additional movie file. (MEP 2 kb)
Additional file 2: Table S1. Case serials. (DOCX 71 kb)
This work was supported by the Shanghai Municipal Key Specialty
Construction Fund of Shanghai Municipal Health Bureau (grant no.
ZK2015A14), Shanghai Municipal Planning Commission Fund (grant no.
20134394), and Shanghai Pudong New Area Science and Technology
Development Fund (grant no. PKJ2013-Y40).
ZW conceived and designed this research. SL acquired the data. XW
obtained the funding. ZW drafted the manuscript. XT, BGF, MHW, and SLX
revised the manuscript for important intellectual content. All authors read
and approved the final manuscript.
Ethics approval and consent to participate
This study was approved by the Ethics Committee of the First Affiliated
Hospital of Dalian Medical University, and written informed consents were
obtained from all patients.
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