Case Report
Isolated "Nutcracker" Fracture of the Anterior Calcaneal Process: Do We Need a More Comprehensive Classification for this Injury Spectrum? A Case Report
Pasquale Sessa1* and Marzia Mascarello2
1Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, BIT. New San Giovanni di Dio Hospital, Florence, Italy
2Department of Anatomical, Histological, The Locomotor-Sapienza Apparatus University of Rome, Rome, Italy
*Corresponding author: Pasquale Sessa, Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Firenze, BIT. New San Giovanni di Dio Hospital, Italy
Published: 18 Sep, 2018
Cite this article as: Sessa P, Mascarello M. Isolated
"Nutcracker" Fracture of the Anterior
Calcaneal Process: Do We Need a
More Comprehensive Classification for
this Injury Spectrum? A Case Report.
Clin Surg. 2018; 3: 2119.
Abstract
Fractures of the anterior calcaneal process are relatively rare accounting for 3% to 15% of all
calcaneal fractures and can occur due to high or low energy trauma. Avulsion fractures are generally
due to forced inversion and plantar flexion of the foot and are associated with ligament tears. More
rare impaction fractures, i.e. nutcracker fractures, are commonly described as due to a forced
eversion and abduction of the foot with compression forcing the anterior process of the calcaneus
against the cuboid. Clinical features are subtle and X-ray examination for the diagnosis of anterior
calcaneal process fracture is challenging. A CT examination can reveal the fracture and should be
performed whenever a doubt exists for correct diagnosis. Here we present the unique clinical case
of a 44ys old female patient who suffered an isolated compression fracture of the anterior calcaneal
process due to a fall from a stair with forced foot eversion and low energy trauma mechanism. The
patient healed uneventfully with a conservative treatment. A more comprehensive classification of
this spectrum injury is sought as many different fracture or combined bone-ligamentous lesions
exist requiring different surgical or non surgical management. Actually, no clear guidelines exist in
literature assisting the treating physician in the management of such challenging lesions.
Keywords: Isolated anterior calcaneal process fracture; Nutcracker fracture; Midtarsal sprain; Chopart fracture-dislocation
Introduction
Anterior calcaneal process fractures are rare, accounting for 15% of all calcaneal fractures [1-3].
Compression, i.e. "nutcracker "fractures of the anterior calcaneal process are described as caused
by a forceful eversion of the foot and are often associated with other fractures or dislocations of the
midfoot [1-3]. They can be due to low energy midtarsal sprain or high energy trauma mechanism
and involve the calcaneo-cuboid articular surface differently from inversion mechanism, where an
intact articular surface is left [4-6]. Isolated nutcracker fractures of the anterior calcaneal process due
to low energy mechanism are exceedingly rare [7,8]. Subtle clinical presentation and difficult X-ray
interpretation due to bone overlap make a high suspicion index necessary for a correct diagnosis
and appropriate management as such fractures are often misdiagnosed in the emergency setting as
ankle sprain [7-9].
Here we present the unique clinical case of a 44ys old female patient who suffered an isolated
compression fracture of the anterior calcaneal process due to a fall from a stair with forced foot
eversion and low energy trauma mechanism.
Case Presentation
A 44ys old female nurse with no sensitive medical history presented to the Emergency Ward of
Our Department due to a fall from stairs at home. The patient referred she had suffered few hours
earlier an ankle sprain; she described an eversion/abduction trauma mechanism of the foot. The
patient revealed that she heard at the moment of the trauma a sudden "clunk" along her lateral foot
side, followed by impossibility to walk. The physical exam revealed ankle swelling and ecchimosis
along the lateral calcaneal side. An elective pain was present over the calcaneo-cuboid joint and
along the course of the fibulotalar ligament. Stress tests did not reveal instability of the subtalar or
midtarsal joint.
The X-ray examination in the lateral view and AP view was
unremarkable for fractures (Figure1). However the lateral 20° view of
the foot revealed a fracture rim along the anterior calcaneal process
(Figure 2). A CT scan was performed and confirmed the diagnosis
of compressive anterior calcaneal process fracture (Figure 3 and 4)
no further bony lesions were assessed at the CT examination. Due to
the preserved length of the lateral column of the foot and the absence
of marked instability or displacement, the patient was managed with
a conservative treatment consisting of below the knee paris plast
without weight bearing for 6 weeks and then progressive weight
bearing assisted with cans for further 4 weeks and range of motion
exercises of the ankle. The patient healed uneventfully without
complaining of foot instability or chronic pain.
Figure 1
Figure 1
a) Antero-posterior and b) lateral X-ray imaging of the left foot.
Facture rim is not visible in conventional views.
Figure 2
Figure 2
a) Dorso-ventral and b) 20° oblique X-ray imaging of the left foot
demonstrate fracture rim involving the anterior process of the calcaneus.
Discussion
The anterior portion of the calcaneus body is a distinct, well
recognized and clinically important part of this bone; despite the
lack of an official anatomic term, it is reported in literature as the
anterior process of the calcaneus [10]. It is a saddle shaped osseous
process that participates to the calcaneo-cuboid joint and forms the
anterior subtalar joint superiorly. A ligamentous network consisting
of the bifurcate ligament and interosseous ligament joins the anterior
calcaneal process with both the navicular and cuboid. Fractures of the
anterior calaneal process are relatively rare accounting for 3-15% of
all calcaneal fractures [1-3] and can occur due to high or low energy
trauma. Avulsion fractures are generally due to forced inversion and
plantarflexion of the foot and are associated with ligamentous tear of
dorsal talonavicular, dorsal calcaneocuboid and bifurcate ligaments
[1-3,7-9]. More rare impaction fractures, i.e. nutcracker fractures,
are commonly described as due to a forced eversion and abduction
of the foot with concomitant axial compression forcing the anterior
process of the calcaneus against the cuboid [7]. The impaction force
propagates through the medial side of the foot generally involving the
navicular bone or other bones and midtarsal ligaments, presenting
mainly as an associated fracture [11-12]. Degan et al. [13] classified
the anterior calcaneal process into three types according to the
fragment extension and dislocation and this classification is often
cited to decide whether a conservative (type I and II) or surgical (type
III) management has to be considered.
Due to similar causative mechanisms and comparable clinical
symptoms with ankle sprain, anterior calcaneus process fracture
with midtarsal sprains are often missed at diagnosis in the emergency
setting. Besides, anterior calcaneal fractures are particularly
challenging to diagnose on plain radiographs [14-15] due to bone
overlap obscuring the midfoot bones. The reported incidence of
missed fractures at the Chopart joint on radiographs ranges from 6%
to 41% in the literature [16-18]. However, the distinction between the
two conditions is of paramount importance because of the different
biomechanics of the joints and an improper management of midtarsal
sprain with associated anterior calcaneal process fractures could lead
to persistent pain and chronic instability with the development of the
cuboid syndrome [19-21].
Clue elements for an appropriate diagnosis, apart a high
suspicious index due to injury pattern, are an elective tenderness
over the calcaneocuboid joint located 1 cm inferior and 3 cm to 4 cm
anterior to the lateral malleolus and a plantar or lateral ecchimosis.
X-ray examination for the diagnosis of anterior calcaneal process
fracture is challenging: oblique X-ray of the foot or a lateral foot
view can reveal the fracture although directing the beam 20 degrees
superior and posterior to the mid portion of the foot can project the
APC away from the talar neck, thus improving fracture visualization
[1-3,7,19-21]. A CT examination can reveal the fracture and should
be performed whenever a doubt exists for correct diagnosis [1-3-
,7,19-21].
The unicity of our case is that a "nutcracker" fracture of the
anterior process of the calcaneus occurred with no associated
lesions of other midtarsal bones and with a low energy mechanism,
differently from other cases reported in literature [18]. The lack of the
navicular avulsion fracture, described as a fracture pattern associated
with calcaneal "nutcracker" fractures, reveals a wide spectrum of
different patterns of lesions involving the anterior calcaneal process
during forced abduction and eversion of the foot according to the
magnitude of involved forces. A more comprehensive classification of
such lesions should be sought as a deeper knowledge of the different
existing fracture pattern may affect the clinical management and final
outcome of such lesions.
The low energy trauma (fall from stairs), supports the hypothesis
that an insufficient trauma force is unable to cause additional fractures
or ligament fracture avulsions through a medial propagation towards
the navicular bone. Medial or capsular lesions could be expected.
According to Hirschmann et al. [7], a MRI in the acute setting seems
to be inappropriate when an accurate diagnosis based on X-ray and
CT is done. Such exam should be performed when unclear clinical
symptoms or non conclusive previous imaging are present.
Although no clear guidelines exist in literature for the treatment
of midtarsal sprain and associated fractures, Open Reduction And
Internal Fixation (ORIF) is usually reserved for displaced (>2 mm)
large fragments (>1 cm) involving the calcaneo-cuboid joint [22] or in
cases of associated non reducible midtarsal dislocation. A conservative
treatment consisting in a below the knee cast immobilization with no
weight bearing for 6 to 8 weeks and then a progressive weight bearing
and range of motion exercises seems to afford good clinical results
[22-23] in the treatment of non displaced or minimally displaced
fractures. Failure to diagnose and properly treat calcaneal fractures
caused by lateral column compression in a timely manner can lead
to severe chronic disability due to lateral column shortening, valgus
deformity, and malalignment of the foot.
Figure 3
Figure 4
Figure 4
Axial and 3D reconstructions showing depression of the articular
surface of the calcaneo-cubiodeal joint.
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