Compartment syndromes after ankle fractures are exceedingly rare, as are
Bosworth fracture-dislocations of the ankle. A high degree of vigilance must
be maintained when managing these fractures in order to avoid complications
and long-term morbidity. We report a case in which a Bosworth
fracture-dislocation resulted in anterior, lateral, and deep posterior
compartment syndrome. The patient was informed that data concerning the case
would be submitted for publication.
A twenty-four-year-old man involved in a recreational soccer match
sustained a severe external rotation injury to the right ankle, resulting in
immediate pain, deformity, and swelling. He sought treatment in the emergency
room, where physical examination revealed a closed injury with a severely
externally rotated foot. He had intact sensation throughout the foot, good
palpable dorsalis pedis and posterior tibial pulses, and active flexion and
extension of the toes that was limited minimally by discomfort.
Initial postinjury radiographs demonstrated a Weber type-B lateral
malleolar fracture with a tibiotalar dislocation (Figs.
1 and
2). Immediate closed reduction
of the tibiotalar joint was performed successfully, but with difficulty, with
the use of intravenous conscious sedation. After reduction, the patient was
comfortable, and the neurovascular function remained intact. A Jones-type
compression dressing with a short leg plaster splint was applied, and
postreduction radiographs showed reduction of the tibiotalar joint. However,
the distal end of the proximal fibular shaft fragment was located
posteromedial to the tibia (Figs.
3,
4, and
5). Because there was already
substantial soft-tissue swelling when the splint was applied, the patient was
discharged to home, with strict instructions to keep the limb elevated, so
that open reduction and internal fixation could be performed following healing
of the soft-tissue injury.
Although the patient was comfortable at the time of discharge, once he was
home he began to experience severe pain in the leg that was not relieved by
oral pain medication. He returned to the emergency room approximately twelve
hours after discharge, at which time he was found to have decreased plantar
sensation and pain with passive stretch of the great toe. The patient was
taken emergently to the operating room, where compartment pressures were
measured with use of an intracompartmental pressure monitor (Stryker
Instruments, Kalamazoo, Michigan). Pressures measured approximately 10 cm
proximal to the ankle joint were found to be 38 mm Hg in the anterior
compartment, 26 mm Hg in the lateral compartment, 10 mm Hg in the superficial
posterior compartment, and 41 mm Hg in the deep posterior compartment. The
patient had a diastolic blood pressure of 55 mm Hg. Given the clinical signs
of compartment syndrome in conjunction with pressure differentials of <30
mm Hg, all four compartments of the leg were released throughout their entire
length with a two-incision technique. Prior to compartment release, the fascia
of the anterior and lateral compartments was noted to be under substantial
tension where it attached distally on the proximal fibular fragment. The
distal part of the fibular fragment was, as expected, incarcerated on the
posterolateral ridge of the distal part of the tibia. Even after compartmental
release, the fibula remained difficult to reduce. With use of a periosteal
elevator and traction, the distal part of the proximal fibular fragment was
finally reduced with an audible snap. After reduction, the lateral malleolus
was stabilized with a 3.5-mm lag screw and a one-third tubular neutralization
plate and screws. The syndesmosis was stressed under fluoroscopy and found to
be unstable, and a 3.5-mm syndesmotic screw was placed across three cortices
(Figs. 6 and
7).
The patient was brought back to the operating room two more times over the
ensuing week for débridement of necrotic muscle from the anterior,
lateral, and deep posterior compartments in the distal third of the leg. There
were viable muscular attachments to all tendons except the extensor hallucis
longus, which was surgically fixed to the extensor digitorum communis. Final
wound closure was accomplished approximately one week after the initial
surgery and required a split-thickness skin graft. Following wound closure,
the lateral malleolar fracture united without incident, and the syndesmotic
screw was removed fourteen weeks after placement.
At the time of writing, one year after the injury, the patient had returned
to participating in recreational sports, albeit with some functional
impairment. Clinically, he had a mildly antalgic gait with approximately
5° of dorsiflexion and 20° of plantar flexion of the ankle, continuing
weakness of the toe flexors and extensors, and residual mild paresthesias on
the plantar surface of the foot.
Including Bosworth's initial 1947 description, there have been
approximately thirty reported cases of Bosworth fracture-dislocation of the
ankle1-14.
This unique fracture pattern involves a fixed posterior fracture-dislocation
of the ankle, in which the proximal fibular shaft fragment becomes
incarcerated on the osseous posterolateral ridge of the distal part of the
tibia. The fracture and associated tibiotalar dislocation are typically
irreducible by closed means; closed reduction was successful in only two of
the reported cases. Although the mechanism of this injury has been debated,
the consequences of overlooking the severe tibiofibular diastasis were all too
apparent in Bosworth's 1947 article, which stated that two of the five
patients required ankle arthrodesis after the injury went
unrecognized1,6,9,12,14.
As rare as Bosworth fracture-dislocations are, compartment syndromes
secondary to ankle fractures have been noted even less frequently. We are
aware of only one reported case of a compartment syndrome associated with a
Bosworth fracture-dislocation, described by Szalay and Roberts; in that case,
an extensor hallucis longus contracture developed after an anterior
compartment
syndrome13.
Previously reported compartment syndromes associated with ankle fractures in
general have typically involved only the deep posterior
compartment13,15-18.
To our knowledge, there have been no previous reports of compartment syndrome
affecting the anterior, lateral, and deep posterior compartments in
association with an ankle fracture.
Routine ankle fracture care at our institution typically involves an
immediate closed reduction; application of a splint; and, depending on the
condition of the soft tissues, either immediate or delayed internal fixation.
Konrath et al. found no increase in the rate of infection or in the difficulty
of obtaining an anatomic reduction when routine ankle fractures were fixed in
a delayed
fashion19. However,
Bosworth ankle fracture-dislocations are not routine; typically, they present
with a gross external rotation deformity as well as dislocated tibiotalar and
distal tibiofibular joints. As can be seen on the initial postreduction
radiographs of our patient, the talus was replaced under the tibia, but the
distal tibiofibular joint remained unreduced. With delayed treatment of an
ankle fracture, it is often the case that the distal tibiofibular joint cannot
be anatomically reduced in the preoperative splint; however, the substantial
posterior displacement of the proximal fibular fragment in our patient should
have been a sign that the fracture-dislocation was unusual.
In addition to the difficult reduction, other factors may have contributed
to the morbidity in this case. The time interval between the onset of the
symptoms and the definitive treatment was unacceptably
long20. At
presentation, twelve hours after the initial reduction, the clinical picture
was already that of a prolonged compartment syndrome. Although absolute tissue
pressures were relatively low, pressure differentials were <30 mm Hg. A
number of studies have shown that intracompartmental pressures of 20 mm Hg
below the diastolic blood pressure substantially decrease perfusion to injured
tissues21,22.
In addition, Heckman et al. demonstrated that compartment pressures are often
highest at the site of
injury23. Being
that the measurements in our patient were obtained away from the site of the
injury, the pressures in the distal part of the leg were probably higher. The
relatively low diastolic blood pressure of 55 mm Hg may also have played a
role, resulting in the patient being more sensitive to elevated tissue
pressures. Various experimental studies have shown that subjects with higher
diastolic pressures are able to withstand higher tissue
pressures21.
Both ankle-fracture-associated compartment syndromes and Bosworth fractures
are rare entities, but as we have illustrated they can and do occur together.
Closed reduction, outpatient observation, and delayed surgery continue to be
appropriate for most ankle fractures, but careful clinical judgment must be
utilized. Vigilance must be exercised when treating injuries associated with
prolonged dislocation, excessive soft-tissue injury, or high energy. Patients
must be given explicit instructions, and complaints of pain must not be
ignored. Otherwise, seemingly innocuous injuries may result in serious
consequences.