12/18/2018 Kevin A. Kirby, DPM
Arthrogram of the 2nd MPJ for Partial Plantar Tear
Regarding the diagnosis of plantar plate tears,
of course diagnostic ultrasound (US) and MRI are
often helpful in ruling out larger plantar plate
injuries. I believe that here in Northern
California, arthrogram is now rarely used to
diagnose plantar plate tears. However,
podiatrists who are only using US to examine the
symptomatic plantar plate, and are not also
examining the other lesser metatarsophalangeal
joint (MPJ) plantar plates with US, should be
well aware of the research literature regarding
frequency of plantar plate tears in symptomatic
and asymptomatic MPJs.
In an excellent US and MRI study by Gregg and
colleagues from 12 years ago, plantar plate
tears were present in 23 of the 24 MPJs (96%) of
six embalmed cadaver feet that were examined
with direct inspection. Partial tears were even
noted in six of the eight plantar plates
examined in the one young (19-year-old) fresh
cadaver specimen analyzed (Gregg JM, Silberstein
M, Schneider T, Kerr JB, Marks P: Sonography of
plantar plates in cadavers: Correlation with MRI
and histology. Am. J. Roentgenology, 186:948-
955, 2006). This means that plantar plate tears
are extremely common and may present in both
asymptomatic and symptomatic lesser MPJs.
In another study by Gregg and colleagues, using
US and MRI on 40 asymptomatic feet and 40
symptomatic feet (i.e. live subjects),
detectable plantar plate tears were found in the
asymptomatic feet at a rate of 46.8% by US and
34.3% by MRI. In the symptomatic patients,
plantar plate tears were found at a rate of
86.8% by ultrasound and 88.7% by MRI (Gregg JM,
Silberstein M, Schneider T, Marks P:
Sonographic and MRI evaluation of the plantar
plate: A prospective study. Euro Radiology,
16:948-955, 2006).
Clearly, the discovery of a plantar plate tear
by MRI or diagnostic ultrasound does not
necessarily mean that the patient is symptomatic
since plantar plate tears seem to be present in
many asymptomatic feet. However, it is likely
that more recent and larger plantar plate tears
are the ones that present to our offices with
the characteristic pain, swelling and digital
deformity seen in these patients. It is also
likely that many patients may have plantar plate
tears in one or more of their lesser MPJs that
remain asymptomatic throughout their lives. Much
more research is necessary to answer these
clinical questions.
It should also be noted that there are excellent
clinical tests that can be used by the skilled
clinician which may preclude the need to perform
US or MRI scans on patients with suspected
plantar plate tears. The dorsal drawer test,
first described by Thompson and Hamilton in
1987, involves manually trying to dorsally
dislocate the proximal phalanx base relative to
the metatarsal head. More than 2 mm of dorsal
dislocation of the proximal phalanx base
relative to the metatarsal head indicates a
positive dorsal drawer test (Thompson FM,
Hamilton WG: Problems of the second
metatarsophalangeal joint. Orthopedics, 10:83-
89, 1987).
The plantar plate provocation test, first
described by Jose Jose Antônio Veiga Sanhudo in
2014, involves dorsiflexing the digit about 10-
15 degrees while the base of the proximal
phalanx is manually pushed plantarly and
distally to stretch the plantar plate. Pain in
the area of the plantar plate indicates a
positive plantar plate pProvocation test
(Sanhudo JAV: Plantar plate provocation test. A
clinical test a clinical sign for identification
of plantar plate lesions. Foot & Ankle
Specialist, 6:24, 2014).
In addition, over the past decade, I have used a
clinical test, the digital plantarflexion test,
to help diagnose plantar plate tears. The
digital plantarflexion test involved
plantarflexing the digit below the normal
plantar level of the digit at the MPJ. In the
asymptomatic MPJ, this test produces no pain.
However, in patients with significant plantar
plate tears, this test will produce pain and an
increased plantarflexion stiffness and the digit
will demonstrate relative lack of plantarflexion
range of motion at the MPJ.
Whatever test is used, the biomechanical
functions of the plantar plate should be well
understood to make certain that the best
treatment options are chosen for patients with
this painful plantar forefoot pathology (Kirby
KA: Understanding the biomechanics of plantar
plate injuries. Podiatry Today, 30(4):30-39,
2017).
Kevin A. Kirby, DPM, Sacramento, CA
