Chronic foot and ankle pain is a common clinical problem in which it is often difficult to locate the anatomic source of pain. The conditions associated with, or causal of, foot and ankle pain include inflammatory arthropathy, degenerative osteoarthropathy, posttraumatic arthrosis, entrapment neuropathy, tendinopathy, joint instability, soft-tissue pathology, and sequelae of congenital/develop-mental abnormalities. Less frequently, tumorous conditions, chronic infection, and vasculopathy produce symptoms in the foot and ankle.
Chronic foot and ankle pain is a common clinical problem in
which it is often difficult to locate the anatomic source of pain.
The conditions associated with, or causal of, foot and ankle pain
include inflammatory arthropathy, degenerative osteoarthropathy,
posttraumatic arthrosis, entrapment neuropathy, tendinopathy, joint
instability, soft-tissue pathology, and sequelae of
congenital/developmental abnormalities. Less frequently, tumorous
conditions, chronic infection, and vasculopathy produce symptoms in
the foot and ankle.
The difficulty in locating the source of pain is often due to
the compact nature of the foot anatomy: the close proximity of
different spaces and structures, such as articulations and soft
tissue insertions, challenge the clinician. Plain radiographs are
poor indicators of the sources of foot pain1 and physical exam is
of limited value in differentiating between two structures only
millimeters apart. It is very important for the surgeon to locate
the source of foot pain precisely in order to initiate
treatment.2,3
The role of diagnostic imaging studies has a heightened impact
on clinical practice when the source of foot pain is unknown or
uncertain. The treating physician must know the diagnostic accuracy
of imaging tests and recognize the efficacy of treatment based on
that diagnostic accuracy. Arthrography and tenography of the foot
and ankle have been applied routinely as diagnostic studies to
determine anatomic abnormalities within joint or peritendinous
space. Some authors have tried to predict disease activity and
physical impairment based on arthrographic findings.4 Magnetic
resonance imaging (MRI), computed tomography (CT), and ultrasound
(US) have supplanted arthrography and tenography in rendering a
visual diagnosis of anatomic abnormality. Therapeutic injection of
joints and soft-tissue structures with local anesthetic and
corticosteroids, performed by an orthopedist in an office, has
important diagnostic significance. The ability of local anesthetic
to reduce pain is often a diagnostic procedure that locates the
source of foot or ankle pain. One of the limited factors in the
accuracy of such "blind" injections is the inability to recognize
exactly where the medication was injected.3,5,6 Another source of
diagnostic error is the possibility of a field block or regional
nerve block by an un-guided injection, thereby masking the true
site of pain origin.
Fluoroscopically guided injections using contrast material to
confirm the position of the needle allows documentation of the
exact site of injection, demonstrates communication between joints,
or between tendons and joints, and outlines space-limiting lesions
such as tendon sheath stenosis or limited joint volume. Precise
documentation of where the anesthetic is inserted is clinically
very important, since any injection lacks specificity without
knowledge of location. This has been well illustrated with
injections in the peroneal tendon sheath and joints in the foot and
ankle: anesthetic placed in the peroneal sheath may enter the ankle
or subtalar joint thereby confusing the diagnosis.5
Diagnostic injections within joint spaces, surrounding tendons,
and within bursae are useful localizers for planning surgical
treatment. Several recent studies suggest that image-guided
anesthetic injections increase the accuracy of diagnosis and have a
positive influence on patient management, including decision-making
by the clinician and the resulting patient outcomes.1,3,5,7 This
paper describes short-term outcomes in three different foot
conditions that have been studied with fluoroscopically guided
injections-small joint arthritis, retrocalcaneal bursitis, and
plantar fasciitis. The purpose of this review is to establish
awareness among radiologists and orthopedists that image-guided
injection has several patient-care benefits, is a reliable
diagnostic tool, and is an efficient use of imaging resources. In
the outpatient clinic, there is an increasing role for the
interventional musculoskeletal radiologist and modern imaging
techniques.1,8,9
Materials and methods
Three groups of adult patients with foot pain were identified
from the orthopedic foot clinic. All patients had foot and/or ankle
pain and were evaluated by an orthopedist. The evaluation consisted
of a problem-focused history, physical examination, weight-bearing
foot radiographs, and follow-up examinations for a minimum of 3
months. All patients with Achilles tendon/bursitis symptoms had a
magnetic resonance imaging (MRI) study. Three diagnostic groups
were created: joint pain, plantar fascia pain, and Achilles tendon
insertion pain. Symptomatic and suspected painful small joints of
the foot were further evaluated by arthrogram, including local
anesthetic with contrast. Plantar fascia patients were evaluated by
a perifascial injection, again, using fluoroscopic guidance and
contrast solution in addition to the anesthetic. The Achilles
tendon insertion group had fluoroscopic-guided injection of the
retrocalcaneal bursa if the MRI showed signs of bursal
inflammation.
Relief of pain was scored by the patient on a 0-to-10 visual
analogue pain scale, with 0 indicating "no pain" and 10 "the worst
pain imaginable." Clinical significance of the injection was
determined by the immediate pain improvement >50% on the pain
scale. Failure to improve or worsening of the pain was considered a
negative result. Pain improvement between 0% and 50% was
indeterminate, and for this study was not considered clinically
significant in predicting surgical outcome. Statistical power and
significance were not applicable to this first group of
patients.
Results
In 96 patients evaluated for arthritis pain, 218 joints were
injected (figure 1). All joints were injected successfully. Based
upon the degree of pain relief from injection, 22 patients were
offered surgical treatment and 18 people chose surgical treatment.
There were 7 painful ankles and 11 painful feet in 18 patients that
had surgical treatment. All of the painful small joints of the foot
had arthrodesis, 3 of the painful ankles had arthrodesis, 2 ankles
had synovectomy and 2 had replacement arthroplasty. Ten of 11
patients with foot arthrodesis had pain relief similar to that of
the injection and 1 patient had approximately 50% pain relief. The
ability to limit the number of joints fused by assessing pain
relief from a series of preoperative image-guided arthrograms was
also important. All patients have a minimum of 9 months follow-up
since surgery. Five of 7 ankle pain patients had relief similar to
the injection; one ankle arthroplasty and one arthrodesis patient
had 50% improvement, none were worse following surgery. All
surgical pathology specimens from the arthrodesis sites
demonstrated the pathologic tissue changes of chronic synovitis,
degenerative joint disease (i.e., bone and cartilage degeneration),
or both.
In 54 patients identified with pain at the origin of the plantar
fascia, 47 had relief >50% of their pain by a single perifascial
injection (figure 2). There were no complications from injection,
though three patients reported temporary worsening of the plantar
heel pain. Surgery was recommended to eight patients with recurrent
pain and successful pain relief from an injection. Five patients
underwent excision of the origin of the plantar fascia and have
been followed a minimum of 1 year. There were no complications from
the surgery and all patients reported functional improvement,
though none had pain relief equal to the maximum improvement from
an injection. All five surgical pathology specimens demonstrated
abnormality of the fascial tissue.
In 15 patients evaluated for Achilles tendon insertion pain,
four patients had symptoms and findings of isolated retrocalcaneal
bursitis with normal tendon. These four patients all had relief of
symptoms following an injection to the retrocalcaneal bursa. Two
patients had prolonged relief from the injection plus oral
non-steroidal medication, two patients had recurrent symptoms and
underwent surgery to excise the bursa and remove the underlying
prominence of the calcaneus. Both operative patients reported
improvement in pain and function at 9 months post-procedure that
was very close to the level of comfort following injection. Review
of the surgical pathology revealed acute and chronic inflammation
of the bursa and no pathologic bone change in each case.
Discussion
Earlier published reports of image-guided small joint injection
disclosed improvement in the surgeon's confidence in the diagnosis,
a positive effect on clinical decision making, and a beneficial
effect on treatment outcome.3,5 The three diagnoses included in
this manuscript suggest the efficacy of image-guided injection in
the management of soft-tissue pain in the foot and joint pain in
the foot or ankle. Other painful foot and ankle conditions are
amenable to advanced imaging with MRI, CT, or ultrasound, followed
by confirmatory injection. Building on the improved accuracy of the
clinical diagnosis of several different painful conditions, the
surgeon may use the subjective improvement from an anesthetic
injection to characterize the anticipated result from successful
surgery. More study is certainly needed to determine the treatment
efficacy of image-guided injections with corticosteroid or
hya-luronic acid and to correlate patient outcome with pain relief
from a guided injection.
Preliminary results suggest that the use of modern diagnostic
imaging techniques have expanded from demonstrating a locatable
abnormality to planning an interventional procedure that has
treatment implications. Fluoroscopic-, US-, or CT-guided injection
allows administration of an anesthetic as well as a therapeutic
agent.8 If permanent pain relief is not achieved from image-guided
injection of medication into a joint or bursa, the temporary pain
relief caused by the anesthetic agent may be a prognostic
indication of patient outcome with conventional orthopedic
procedures.4,8,9 Since one source of uncertainty in failed surgery
of the foot or ankle is the correctness of the diagnosis,7,8
image-guided injection should decrease the likelihood of poor
surgical outcome due to inaccurate identification of the clinical
source of preoperative pain.
With resources for health care and treatment innovation
decreasing, orthopedic surgery for the management of painful foot
conditions may provide significantly better outcomes with the
inexpensive addition of image-guided injection. Future research
into the efficacy of image-guided injections is needed to determine
both the accuracy of diagnosis and the cost-effective prediction of
surgical outcome. These prospective studies should investigate if
fluoroscopy-guided or ultrasound-guided injections are more
accurate, whether they are reasonable treatment modalities, and
examine the relative cost of the two procedures. There is now a
growing body of evidence that the surgical care of painful foot and
ankle conditions is yielding better patient outcomes due to better
clinical information from advanced imaging techniques combined with
the patient's response to a guided injection of local anesthetic.
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