Total talar dislocation is a rare
injury1-6
that usually occurs as a result of a high-energy continuation of extreme
supination forces causing lateral subtalar dislocation or extreme pronation
forces causing medial subtalar
dislocation7. Most
of these injuries are open and are associated with a high rate of
postreduction complications, such as persistent infection (reported in up to
89% of patients2),
shearing osteochondral fractures
(45%3),
osteonecrosis (33% to
50%1,8,9),
and severe degenerative
arthritis5,6.
Prompt closed or open reduction of the talus, when possible, is the
recommended treatment, in combination with soft-tissue débridement of
open
injuries3,10.
However, the high rate of complications has led many authors to suggest that
primary excision of the talus or tibiocalcaneal
arthrodesis1,2,4,5,11
should be performed instead. Tibiotalar or pantalar arthrodesis has been
recommended for any cases of osteonecrosis or arthritis that develop
later.
Primary open dislocation with loss of the talus ("missing
talus")2,
however, necessitates the performance of either a tibiocalcaneal arthrodesis
or a resection arthroplasty, which is difficult to create and maintain. Both
procedures often produce unwanted effects on the foot, particularly in young
patients, because of loss of function of the peritalar
joints3,12-14.
To avoid the necessity of performing these procedures and to preserve ankle
function, the implantation of a talar body prosthesis has been
proposed15. Because
the long-term survival of such an implant, especially in active individuals,
is not known, a total ankle arthroplasty coupled with a talar prosthesis fixed
to the calcaneus and the navicular may be an alternative solution.
We describe the case of a forty-five-year-old man in whom total ankle
arthroplasty and insertion of a talar body prosthesis were performed in an
effort to preserve ankle mobility. Our patient was informed that data
concerning the case would be submitted for publication.
Aforty-five-year-old expert male skier and rock-climber fell while climbing
and sustained an open total medial dislocation of the left talus and an
associated fracture of the medial malleolus. The body and neck of the talus
along with the medial malleolus (Fig.
1-A) were left at the site of the accident. The patient was
transferred directly to our institution for treatment of this injury as well
as multiple other injuries, including a fracture of the left tibial
intercondylar eminence, a comminuted fracture of the right greater trochanter,
a pelvic fracture with slight widening of the pubic symphysis, and a
dislocation of the proximal interphalangeal joint of the long finger of the
right hand. There were no associated vascular or neurologic lesions.
The ankle injury was treated acutely with soft-tissue débridement,
reconstruction of the tibiocalcaneal portion of the deltoid ligament with a
portion of the posterior tibialis tendon inserted proximally into a hole
drilled into the distal tibial metaphysis, and stabilization of the
tibia-hindfoot axial alignment by means of an external fixator. The gap
between the distal aspect of the tibia and the calcaneus that was caused by
the absence of the talus was maintained while the talar head fragments were
débrided (Figs. 1-B and
1-C).
Bilateral computed tomographic scans of the ankle joint and the hindfoot
were performed on the sixth postoperative day to obtain correct measurements
of the bone dimensions in both the injured and the healthy limb. The external
fixator was removed on the tenth postoperative day to avoid infection and bone
contamination, and the axial alignment was maintained with a cast
(Fig. 2). The patient was
discharged with instructions to continue systemic antibiotic therapy for four
weeks. Weight-bearing was not permitted. Once it had been ascertained that
there were no clinical, laboratory (erythrocyte sedimentation rate and
C-reactive protein level), or radiographic (plain radiographs, computed
tomographic scans, and magnetic resonance images) signs of infection, a
prosthetic replacement of the talar body was planned.
The laboratory procedure for the production of the prosthesis
(Waldemar-Link, Hamburg, Germany) included entry of the
computed-tomography-generated data into a computerized system for image
processing and assisted design. Each computed tomographic scan was analyzed to
determine the exact bone contour. In the case of our patient, it was necessary
to analyze the computed tomographic data of the contralateral, healthy joint
to determine the appropriate size of the component that would replace the
missing talus. The calculated data were sent to a computer-controlled,
five-axis milling machine to guide the manufacture of the talar component from
a block of titanium alloy. The angle and position of the hole for a fixation
screw was planned and drilled. To enhance the integration of the implant with
the bone surfaces of the calcaneus and the navicular, a microporous surface
coating was applied to the parts of the implant that would abut these
sites.
Our aim in using the implant was to preserve the mobility of the ankle
joint. For this purpose, the talar component from a Scandinavian Total Ankle
Replacement (STAR) (Waldemar-Link) total ankle prosthesis was selected, to be
cemented onto the prosthetic talus. A custom-built tibial component that
included a medial-retaining flange to replace the avulsed medial malleolus was
also fabricated.
Five months after the accident, the patient underwent surgical implantation
of the prosthesis through an anteromedial approach. The skin incision was
started 10 cm proximal to the distal aspect of the tibia and passed between
the tendons of the tibialis anterior and extensor hallucis longus. The
anterior aspect of the ankle joint was opened to expose the gap between the
tibia, the navicular, and the calcaneus. The gap contained reactive fibrous
tissue with no evidence of infection or inflammatory reaction. After careful
excision of this tissue, the articular surfaces of the calcaneus and the
navicular were resected to expose subchondral bone. Care was taken to avoid
damaging the ligament reconstruction between the tibia and the navicular on
the medial aspect of the ankle, which had been created during the first
surgical procedure.
The tibial saw-guide of the STAR total ankle instrumentation was positioned
and was secured with three pins, thus obtaining the correct alignment between
the guide and the tibial axis. The resection cuts were made horizontally and
tangentially along the distal surface of the cutting guide. The preparation of
the tibia was then completed by the drilling of two holes for the cylindrical
anchors of the tibial component of the prosthesis.
The talar prosthesis was easily inserted into the ankle mortise. Care was
taken so that the inferior facet of the implant rested snugly on the posterior
osseous facet of the calcaneus and so that the anterior aspect of the implant
mated properly with the posterior facet of the navicular. One fixation screw
was then positioned in the calcaneus, perpendicular to its articular surface,
and the anterior flange of the implant was secured to the navicular with two
screws. The STAR prosthetic talar component was then cemented onto the
substitute talus, and the tibial component was driven carefully into the holes
that had been previously drilled into the distal aspect of the tibia. The
required thickness of the polyethylene sliding core was determined, and a
standard component was inserted to achieve adequate tension of the medial and
lateral ligaments while preserving mobility of the ankle to 50°
(Figs. 3-A and 3-B).
Weight-bearing was started one week after the operation, and the patient
wore a below-the-knee brace for five weeks. During the next three months,
passive mobilization with the leg out of the brace, squatting exercises, and
strengthening exercises of the muscles in the distal part of the leg were
performed. Prophylaxis against deep venous thrombosis was provided with daily
systemic administration of low-molecular-weight heparin for four weeks.
A clinical examination was performed and plain radiographs were made every
four months, and the patient was reassessed at twelve, twenty-four, and
twenty-eight months after the operation. Twenty-eight months after the
implantation, the patient had no pain or limp during his normal activities,
and he was able to walk without impediment but was unable to run. He could ski
for three consecutive hours and could also walk over rough surfaces. He had
difficulty descending stairs and had occasional slight pain after prolonged
weight-bearing.
Clinically, there was a slight varus deviation of the hind-foot
(Fig. 4-A) due to the alignment
of the talar prosthesis on the calcaneus. The ankle range of motion was from
5° of dorsiflexion to 30° of plantar flexion, as documented by
fluoroscopy. The ankle-hindfoot score, according to the modified scale of the
American Orthopaedic Foot and Ankle
Society16, was 92
points of 100 points; the subscores for pain, function, and alignment were 40
of 40 points, 47 of 50 points, and 5 of 10 points, respectively. Plain
radiographs showed good alignment of both the tibial and the talar prosthetic
component, with no evidence of loosening or periprosthetic radiolucent lines
(Figs. 4-B and 4-C).
Our patient presented with a rare combination of complex injuries and
reconstructive challenges. The open talar dislocation was associated with loss
of the medial malleolus and complete disruption of the deltoid ligament, which
limited the options for
treatment2,3.
Prompt débridement of the soft tissues, temporary stabilization of the
hindfoot with an external fixator, and reconstruction of a portion of the
deltoid ligament with use of a portion of the tibialis posterior tendon
prevented infection and made it possible to perform the prosthetic total ankle
replacement. During the five-month observation period, critical steps were
taken to check for any clinical, laboratory, or radiographic signs of
infection as well as to secure the stability of the ankle ligaments, which
were important prerequisites to the performance of total ankle
arthroplasty17-19.
Total ankle arthroplasty has been
reported1,2,11,12,14,19
to be a useful treatment for
degenerative19 as
well as
posttraumatic20
arthritis of the ankle, although the surgery is considered to be more
demanding and challenging with posttraumatic arthritis, particularly in
younger
patients19,21-24.
However, there have been isolated reports in the literature concerning the use
of a talar
prosthesis15. In
one small series, the duration of followup ranged from five to fifteen years,
with satisfactory
results15.
The follow-up radiographs of our patient showed no periprosthetic bone loss
or signs of loosening of the implant. Perhaps the surrounding joints were
effective in transmitting forces away from the prosthetic talus, thereby
reducing the concentration of stresses around the
implant3,15,25.
Nevertheless, the long-term durability of this implant is unknown. Mechanical
failure of a total ankle prosthesis does not always lead to dramatic loosening
that requires revision; it can also induce ankylosis of the ankle that can be
well tolerated by the
patient20,21,23,26.
Our patient was a forty-five-year-old professional sportsman who wished to
remain physically active in his work as a mountain guide and ski instructor.
We believed that this goal could best be achieved by preserving the maximum
possible functional capability of the tibiocalcaneal articulation. An
arthrodesis would not have allowed our patient to achieve the same level of
functional recovery, although that procedure ultimately may be required in the
future.
The fabrication of the prosthesis used in our patient required the
resources of an industrial laboratory and a special computerized system to
process the computed tomography data. The case of our patient may stimulate
the development of a modular total ankle arthroplasty system that includes
complementary talar and tibial components that can be used in patients with
severe trauma-induced or tumor-induced bone loss as well as for the more
standard indications, such as revision total ankle arthroplasty.
We believe that the combination of a total ankle arthroplasty and a
custom-built talar prosthesis secured to both the calcaneus and the navicular
may be useful in the treatment of rare cases of large, trauma-induced bone
defects. In the case of our patient, this solution provided good medium-term
functional results that enabled the surgeon to avoid, or at least to delay,
the performance of a conventional arthrodesis.