Arthroscop¡c Evaluation of the Subtalar Joint: Does Sinus Tarsi

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Copyright O 1999 lry the American Orthopaedic Foot and Ankle Society, lnc
Arthroscop¡c Evaluation of the Subtalar Joint: Does Sinus Tarsi Syndrome
Exist?
Carol Frey, M.D.,- Keith S. Feder,T and Christopher DiGiovanni, [/.D.t
Manhattan Beach, California, and Providence, Rhode lsland
(Fig. 1). Wjth the introduction of small
"r¡13's-e't1-14'16
instruments and precise techniques, arthroscopy of
ABSTRACT
This is a retrospective review of 49 subtalar arthroscopies performed between 1989 and 1996. Patients were
evaluated in the following areas: (1) preoperative diagnosis, (2) preoperative tests and clinical evaluation, (3)
the small joints, including the subtalar joint, has expanded during the last decade. Despite an expansion
of techniques, the number of reports dealing with subtalar joint arthroscopy remains small, and even fewer
reports deal with clinical applications and results.
The purpose of this study was to undertake a retrospective review of 49 subtalar arthroscopies performed by the senior author between 1989 and 1996.
Patients were evaluated in the following areas: ('1)
intraoperative findings, (4) postoperative diagnosis,(5)
complications, and (6) clinical outcome. Particular atten-
tion was paid to the accuracy of the preoperative diagnosis, subtalar instability, intraoperative findings in sinus
tarsi syndrome, and clinical outcome. Overall, this study
demonstrated a success rate of 94o/o good and excellent
results in the treatment of various types of subtalar
pathologic conditions with arthroscopic techniques. The
Workers' Compensation cases reported 907o good and
excellent results. The complication rate was low, with
five minor complications reported. The most common
preoperative diagnosis, (2) preoperative tests and clln-
ical evaluation (including MRI and stress tests),
complication was a trans¡ent neuropraxia involving
branches of the supedicial peroneal nerve.
Of the 14 feet that had a preoperative diagnosis of
agnosis, subtalar instability, intraoperative findings
sinus tarsi syndrome, and clinical outcome.
sinus tarsi syndrome, all the diagnoses were changed at
the time of arthroscopy. The postoperative diagnoses
included 10 interosseous ligament tears, two cases of
arthrofibrosis, and two degenerative joints. Based on
these findings, "sinus tarsi syndrome" seems to be an
inaccurate term that should be replaced with a specific
diagnosis. Arthroscopy is the tool that will allow the
orthopaedic surgeon to make a more accurate diagno-
in
MATERIALS AND METHODS
A retrospective review was performed of all patients
who had undergone subtalar arthroscopy between
1989 and 1996. lnclusion criteria for the study included having had a subtalar arthroscopy by the primary author (C.C.F.) as well as adequate postopera-
sis.
tive follow-up. A total of 45 patients (49 subtalar
arthroscopies) made up the study population. For
each patient, the preoperative diagnoses, operative
INTRODUCTION
findings, postoperative diagnoses, and outcome were
The complex anatomy of the subtalar joint makes
radiographic and arthroscopic examination diffi-
-
(3)
intraoperative findings, (4) postoperative diagnosis, (5)
complrcations, and (6) clinical outcome. Particular attention was paid to the accuracy of preoperative di-
recorded. This information was obtained from a review
reports,
office notes from follow-up visits, and radrographic
studies (plain films, bone scans, magnetic resonance
imaging (MRl), and computed tomography scans). ln
2'1 of 35 ankles that had stress radiographs of the
ankle, the subtalar joint was also visualized. lnstability
of the subtalar joint was assessed from the anterior
drawer view when there was anterior translation of the
of initial histories and physicals, operative
Director, Orlhopaedic Foot and Ankle Center, Manhattan
Beach, California. To whom requests for reprints should be addressed at Orthopaedic Foot and Ankle Center, 1200 Rosecrans,
Suite 208, Manhattan Beach, CA 90266
I Clinical lnstructor, Harbor-UCLA Medical Center, Department
of Orthopaedic Surgery, Los Angeles, California, and Director,
Sports Medicine and Arthroscopy, West Coast Center for Sports
Medicine, Manhaltan Beach, California.
t Clinical lnstructor, Department of Orthopaedic Surgery, Brown
University, Providence, Rhode lsland.
posterior facet of the calcaneus on the talus. On the
varus stress view, subtalar instability was indicated
185
186
Foot & Ankle lnternational/Vol. 20, No. 3/March 1999
FREY ET AL.
A
A
(lntermediate Branch)
msdial r€llnacular rool
llgamont ol târsâl canal
B
B
Med¡al
lnterosseous
Talocâlcaneal
Fig.
1.
Retinacula
A, Division of the subtalar joint into anterior and posterior
portions by the sinus tarsi and the tarsal canal. B, Contents of the
tarsal canal include the cervical ligament, talocalcaneal l¡gament,
and medial root of the inferior extensor retinaculum, fat pad and
blood vessels.
when a loss of parallelism was noted of the posterior
facet of the calcaneus and the talus.a All perioperative
complicat¡ons were noted. Any additional procedures
performed at the time of surgery were also recorded.
The arthroscopic technique followed the initial description of Parisien.ll'12 4n anterior, posterior, and
middle portal were used. The middle poftal is essential
for the evaluation of the sinus tarsi and its contents.s
Local, general, spinal, or epidural anesthesia were
used for this procedure. The patient was placed in the
lateral decubitus position with the operative extremity
up (Fig. 2A & B ). ln addition to padding between the
legs, a bolster was placed distally under the operative
extremity to suspend the foot and the leg. A tourniquet
was used for hemostasis.
The three portals were available for visualization and
instrumentation of the subtalar joint. The anterior portal was placed 2 cm anterior and 1cm distal to the tip
Fig.2. A, Anterior, posterior, and middle porlal were used for the
subtalar arthroscopy. B, Patient was placed in the lateral decubitus
position with the operative extremity up.
of the lateral malleolus. The posterior portal
was
placed I cm proximal to the tip of the fibula and ante-
rior to the Achilles tendon. The middle portal was
placed under direct visualization, using an 1B-gauge
needle with outside-in technique. A 2.7-mm 30"
oblique arthroscope and an arthroscopic pump were
used for the procedure.
RESULTS
The overall demographics of this patient group were
as follows. The average age was 35 years (range,
17-66). There were 26 men and 19 women. Twentyeight (57%) of the subtalar joints involved Workers'
Compensation cases, and 21 (43%) did not. The
mechanism of injury was a twisting injury to the foot
and ankle (usually inversion) in 32 feet (62%), direcT
blow or crush injury in 10 feet (21%), overuse injury
(such as climbing or walking on uneven ground) in five
feet (12Yo), and congenital (fibrous coalition) in two
Foot & Ankle lnternational/Vol. 20, No. 3/March 1999
SINUS TARSI SYNDROME
187
feet (5%). The average follow-up was 54 months
(12-BB months). No patient who entered into the study
was lost to follow-up.
Preoperatively, the diagnoses included interosseous ligament injury in 26 feet (53%), sinus tarsi syndrome in 14 feet (25%), fibrous coalition in four feet
(B%), ar|hrofibrosis in three feel (6%), and osteochondral fracture of the posterior subtalar joint in two feet
(4%). Diagnosis of sinus tarsi syndrome was made on
primarily subjective findings that included pain over
the sinus tarsi, feelings of instability in the hindfoot,
and pain relief after injection of local anesthetic into
the sinus tarsi.10 The MRI in sinus tarsi syndrome may
show findings consistent with scar, ganglion cyst, or
interosseous ligament disruption. The diagnosis of interosseous ligament injury was made when the same
subjective findings were present as in sinus tarsi syndrome, but in addition, the MRI showed disruption of
the interosseous ligament. The interosseous ligaments
are seen best on sagittal and coronal views. lt should
be noted that the diagnosis of interosseous ligament
tears were made in later cases after the radiologist and
the surgeon had gained more experience in reading
the MRls and comparing ihem to intraoperative findings. Only one case of interosseous ligament injury
was noted to have instability of the subtalar joint,
preoperatively, as demonstrated by stress views of the
subtalar joint (Fig. 3).
Fibrous coalition was a diagnosis based on the
presence of a subtalar joint with limited range of motion but not after trauma or long term immobilization.
MRI findings were suggestive for a fibrous coalition. ln
addition, x-rays showed either a squaring off of the
borders of the calcaneonavicular articulation on an
oblique view of the foot or an obliquity of the medial
facet of the subtalar joint on Harris vìews. Arthrofibrosis was a diagnosis based on the clinical findings of a
joint with limited range of motion, which usually existed after trauma or immobilization. The patients with
arthrofibrosis dìd not have findings on MRI or x-rays to
suggest a tarsal coalition.
Postoperatively, the following diagnoses were
made: interosseous ligament injury in 36 feet (74%),
arthrofibrosis in seven feet (14%o), degenerative joint
disease in four feet (B%), and fibrous coalition of the
calcaneonavicular joint in two feel (4%). Of the 36 feet
with interosseous ligament tears, 27 feet demonstrated scar formation and gross hyalinization of the
torn ligament ends and subsequent impingement of
this material into the anterior aspect of the posterior
subtalar joint. This is referred to by the authors as the
subtalar impingement lesion (STIL) (Fig. a).
Postoperatively, the diagnosis was changed or clarified in 17 feet (35%). The diagnosìs was changed
3.
Fig.
Stress view of the subtalar joírrt demorrstrating instability.
The anterior drawer view will demonstrate anterior translalion of lhe
posterior facet of the calcaneus on the talus wlrerr instability is
present in the subtalar joint. A, [3efore stress, 8, After stress.
postoperatively in all cases of sinus tarsi syndrome, in
all cases of osteochondral fractures, and in two cases
of fibrous coalitiorr.
Of the 14 feet that had a preoperative diagnosis of
sinus tarsi syndrome, the following postoperative diagnoses were made: interosseous ligament tear in 10
feet, arthrofibrosis in two feet, and degenerative joint
disease in two feet.
Of the 36 cases that demonslrated injury to the
interosseous ligaments, only one case demonstrated
instability by stress radiographs, preoperatively. lntraoperatively, seven feet demonstrated subtalar instability; six of these feet had a75%o tear of the interosse-
ous ligament and one had a complete tear. lt should
be noted, again, that althor-rgh seven cases demonstrated subtalar instability, intraoperatively, only one
demonstrated instability on preoperative stress radiographs. l-lowever, of 29 feel wittrout clemonstrable
subtalar instability, the following extent of injury was
documented: three had a 25o/o lear, 17 had a 50'r/o
1BB
FREY ET AL.
Foot & Ankle lnternational/Vol. 20, No. 3/March 1999
Fig. 4. Hyalinization of the torn ends of lhe interosseous ligament ends and subsequent impingemenl of this material into the anterior aspect
of the posterior subtalar joint is referred to as the subtalar impingement lesion (STIL). A, Demonstration of a form of the STIL before much
hyalinìzation. B, Artist's version of that lesion. C, Floor of the sinus tarsi afler a thorough debridement. D- F, Artist's version of the STIL before,
during, and after debrìdement.
Foot & Ankle lnternatìonal/Vol. 20, No. 3/March 1999
SINUS TARSI SYNDROME
189
5.
Fig.
Subtalar instability is demonstrated arthroscopically as the posterior facet of the calcaneus glides laterally out from under the talus
as the subtalar joint is stressed in varus. A, Before stress. B, After stress. C and D, Artist's version oi the arthroscopic
stress test.
tear, and nine had a 75%o tear of the interosseous
ligaments. lt should be noted that the authors found it
difficult to demonstrate subtalar instability by exerting
a varus stress to the hindfoot and measuring the
amount of lateraljoint opening. Rather, it seemed that
the major arthroscopic finding was a medial glide of
the calcaneus out from under the talus (Fig. S).
A subjective scale was designed to evaluate postoperative results. Excellent results indicated no pain
and no lifestyle restrictions. Good results indjcated
improvement but some pain or lifestyle restrjctions.
Poor results indicated that the patient had not improved or was worse. The average follow-up was 4
years and 9 months (range, I year-7 years and g
months). Twenty-three feet (47%) had excellent results, 23 feel (47%) had good results, and three feet
(60/o) had poor results. Of patients with poor results, all
subsequently had a successful subtalar fusion. When
evaluating only those 36 feet with a postoperative
diagnosis of interosseous ligament tear, the following
results were noted: 21 excellent (SB%), 13 good
(36%), and two poor (6%). Twenty-eight of the feet
were Workers' Compensation cases. Of these cases,
there were 10 (36%) excellent results, 1b (54%) good
results and three (11%) poor results.
There were five reported complications, including
three cases of neuritis involving branches of the superficial peroneal nerve, one case of sinus tract formation, and one case of a superficial wound infection
which occurred in the patient with the sinus tract
formation. The three cases of neuritis were treated
successfully with cortisone injections and physical
therapy. The patient with the sinus tract formation and
the superficial wound infection was treated successfully with antibiotics, wound care, and subsequent
total contact casting.
Twenty cases had ankle arthroscopy performed at
the same time as the subtalar arthroscopy. Eleven of
these cases had injury to the lateral collateral ligaments or lateral capsule without ankle instability, but
necessitating debridement of the lateral gutter. Nine
cases had injury to the lateral collateral ligaments with
ankle instability that required reconstruction of the
ligaments. Of these cases, there were 10 (50%) excel-
190
FREY ET AL
lent results, seven (35%) good results, and three
('15%) poor results.
DISCUSSION
This study demonstrated a success rate of 94%o
good and excellent results in treating various types of
subtalar pathologic conditions with arthroscopic techniques. Workers' Compensation cases reported 90%
good and excellent results, but all of the poor results
were in this group. lt was interesting to note that of 20
patients who had concurrent ankle arlhroscopy, 85%
excellent and good results were repoded' However, all
of the poor cases were also in this group. lt may be
that the patients who required both ankle and subtalar
arthroscopy had more severe injuries, which required
more surgery and had a higher risk of poor results
(although the number of poor results still remains relatively small).
The complication rate was low and was represented
by five minor complications, which resolved with nonsurgical treatment. As seen in ankle arthroscopy, the
most common complication was a transient neuropraxia involving branches of the superficial peroneal
nerve.
ln this study, sinus tarsi syndrome was a common
preoperative diagnosis. However, sinus tarsi syndrome remains a vague term in the orlhopaedìc literature. lt has been defined as pain in the sinus tarsi
region of the subtalar joint that responds to injection
and is associated with a feeling of instability in the
hindfoot.2'15'18 Despite years of clinical attention, however, its cause remains poorly understood. To date,
there exists no pathognomonic history, physical examination findings, or set of tests that can be relied on
in making the diagnosis. lt is interesting that some of
these patients often improve with various forms of
surgical debridement of the sinus tarsi.
Sinus tarsi syndrome is an inaccurate term which
should be dropped and replaced wìth a more accurate
diagnosis, when possible. Arthroscopy is a tool that
will allow the orthopaedic surgeon to make a more
accurate diagnosis. The authors noted in this study
that, of '14 feet that had a preoperatìve diagnosis of
sinus tarsi syndrome, all diagnoses were changed at
the time of arthroscopy. The postoperative diagnoses
included 10 interosseous ligament tears, two cases of
arthrofibrosis, and two degenerative joints' With the
more accurate diagnosis that can be made arthroscopically, the general term, sinus tarsi syndrome, can
be dropped in most cases. As a result, treatment plans
can become more exact and outcomes will hopefully
improve.
Subtalar instability was also evaluated in this study.
Foot & Ankle lnternational/Vol, 20, No 3/March 1999
Although subtalar instability is most commonly assocìated with ankle instability, it can exist on its own.
There have been multiple techniques reported for
evaluating subtalar instability, including stress tomograms, specific subtalar stress radiographs, fluorosðopy, ano subtalar arthrograms .Íxr'a'7'1a'18 Subtalar
arthroscopy and direct visualization of the joint may be
the most accurate way of evaluating the unstable joint'
Because motion occurs in a screw-like fashione about
an axis of rotation that forms an angle of 10" to 15" with
the sagittal plane and an angle of 45" with the horizonlal plane of the foot,17 it may be that evaluating the
joint with varus stress, as done in the above radiographic tests, is not accurate. What was seen at arthroscopy was a glide of the posterior calcaneal facet,
medially, from under the talus. This may represent one
part of the screw-like motion of the subtalar joint.13
Although only one preoperative radiographic technique was used for evaluating instability of the subtalar joìnt in this study, it is the technique which is most
available to orthopaedic surgeons. Regardless, instability of the subtalar joint was noted in only one foot,
preoperatively, but was thought to exist in seven feet
at the time of arthroscopic evaluation. Further experience with observing normal motion of the subtalar
joint during arthroscopy may lead to greater confidence in recommending arthroscopic stress tests in
the evaluation of subtalar instability in the future.
Possible indications for arthroscopy of the subtalar
joint and sinus tarsi include the following: (1) removal
of loose bodies, (2) evaluation of chondral and osteochondral fractures, (3) excision of intra-articular adhesions, (4) appraisal of articular cartilage damage after
calcaneal or talar body fractures, and (5) possible
arthrodesis. Subtalar arthroscopy is also useful in the
diagnosis and treatment of chronic hindfoot pain, sub-
talar instability, chronic pain in the sinus tarsi, interosseous ligament iniuries, synovitis, osteoarthritis,
and possìbly for removal of fibrous or cadilagenous
talar coalitions.
The major advantages of arthroscopic versus open
surgery for pathologic conditions in the subtalar joint
and sinus tarsi include decreased morbidity and a
rapid rehabilitation. Open approaches to the subtalar
joint can involve excision of the fat pad, detachment of
the extensor digitorum brevis from the sinus tarsi, and
transection of the lìgaments in the sinus tarsi and
tarsal canal. Although the exact morbidity of this dissection is unknown, there are obvious theoretical advantages to preserving normal anatomy'
Subtalar arthroscopy fills the gap that exists in the
treatment of subtalar disease between treatment of
pathologic conditions with a UCBL (University of California, Biomechanical Laboratories) orthotic device
Foot & Ankle lnternational/Vol. 20, No. 3/March 1999
and a subtalar fusion. Arthroscopy of the subtalar joint
and sinus tarsi is a valuable tool in the investigation of
hindfoot pathologic conditions when nonsurgical
treatment fails, and a subtalar fusion is not indicated.
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SINUS TARSI
SYNDROME
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