Patellar ВWhickering.

394
Figure 2. C‘alc[jific.o/ion
in the quadriceps mechanism.
Patellar “Whiskering”
To the Editor:
This communication is written in response to an
article by Turjeque et al. on Patellar “Whiskers” (Arthritis Rheum 20:1409-1412, 1977). Although I do not
disagree with the authors that radiodensity along the
superior surface of the patella on lateral radiographs is a
frequent finding, particularly in elderly patients, one
must be careful not to consider all such deposits as
“calcification.” Several distinct radiographic findings
may be apparent.
Patellar Hyperostosis. Bony thickening or hyperostosis (Figure 1 ) on the anterior surface of the patella
may occur on the superior and/or inferior surfaces of
the bone. These ossific shadows extend into the adjacent tendon with visible bony trabeculae. These outgrowths may occur as an incidental finding in patients
who are asymptomatic or whose symptoms relate to
other findings. We have noted such deposits in one
patient (5% of 21 men with an average age of 65 years)
without any knee symptomatology ( I ) . Figure 1 in the
article by Trujeque et al. indeed demonstrates such a
deposit. I n fact, adjacent hyperostosis on the anteroinferior surface of the patella is just visible in this reproduction.
An increased incidence of patellar hyperostosis is
apparent in ankylosing hyperostosis of the spine (diffuse
idiopathic skeletal hyperostosis-DISH).
We have
noted such ossification in 29% of 21 patients with this
disorder. This finding is representative of a characteristic manifestation of the disease: hyperostosis at sites of
tendon and ligament attachment to bone in both axial
and extraaxial skeleton. Hyperostosis is observed at
other extraspinal sites including the pelvis, calcaneus,
and ulnar olecranon.
Calcification in the Quadriceps Mechanism. Linear calcific radiodensities may be seen within the quad-
395
riceps at or separated from the superior margin of the
patella (Figure 2). These densities are not common in
the general population but are observed in approximately 4% of patients with calcium pyrophosphate deposition disease (2). In this condition, tendon calcification is not limited to the quadriceps mechanism but also
occurs elsewhere, including the rotator cuff region of the
shoulder, triceps, and achilles tendons in association
with calcification of cartilage (chondrocolcinosis), synovium, ligaments, and soft tissue. A report has appeared
that biopsy of a calcified achilles tendon in one such
patient demonstrated calcium pyrophosphate dihydrate
crystals (3).
Patellar Osteophytes. If we reserve the term
osteophyte in the current discussion to b.one formation
occurring at the articular margins of the patella, these
excrescences are seen at the posterior superior and posterior inferior margins of the patella (Figure 3). They are
distinct from anterior hyperostosis and quadriceps calcification. Osteophytes may be seen in patellofemoral
osteoarthritis and as part of the structural joint change
which is characteristic of calcium pyrophosphate deposition disease (2).
Each of these recognizable radiodensities-patellar hyperostosis, quadriceps tendon calcification, and
patellar osteophytes-is associated with different clinical manifestations and may be the radiographic clue to
an underlying disease process such as diffuse idiopathic
skeletal hyperostosis, calcium pyrophosphate deposition
disease, and osteoarthritis.
DONALD
RESNICK,M . D .
Chief. Department of Radiology
Veterans Administration Hospital
3350 La Jolla Village Drive
San Diego, California 92161
REFERENCES
I . Resnick D, Shaul SR, Robins JM: Diffuse idiopathic skeletal hyperostosis (DISH): Forestier’s disease with extraspinal manifestations. Radiology I I5:5 13-524, 1975
2. Resnick D, Niwayama G, Goergen TG, Utsinger PD, Shapiro RF, Haselwood DM. Wiesner K B Clinical, radiographic and pathologic abnormalities in calcium pyrophosphate dihydrate deposition disease (CPPD): pseudogout.
Radiology 122:1-15, 1977
3. Gerster JC, Baud CA, Lagier R, Boussina I, Fallet GH:
Tendon calcifications in chondrocalcinosis: a clinical, radiologic, histologic and crystallographic study. Arthritis
Rheum 20:717-722, 1977
Radiographic Survey of the Knees
Figure 3. Parellar osteophytes.
To the Editor:
The letter to the editor by Mink et al. ( I ) has
much merit in the areas that they mention: abundant
information, reducing cost, and reducing radiation.
However, for approximately 254, the standing
views of both knees are much more useful if done on a
14 X 17 cassette (standard chest size in a vertical position). This will allow the physician to determine more
adequately the amount of varus or valgus deformity,
and more bone is seen with very little additional radiation. The amount of technician time and developing
time is identical and the cost of the film is neglible for
the added information. These will allow the orthopedic
surgeons to see what type of total knees might be more
appropriate, the adequacy of bone stock, and whether
an osteotomy (though rarely indicated in rheumatoid
arthritis) may be considered.