cadera / hip - Active Congress.......

VIERNES / FRIDAY
282
the femoral component and the posterior femoral
cortex as a consequence of unremoved
oseophytes or inadequate posterior capping
may be responsible for painful limited motion.
Plain x-rays or CT scans may detect most of
the mechanically related factors.
A painful stiff knee without identifi able mechanical
reason has its origin in a biological
process which induces inflammation and
scarring of the synovium and adjacent
connective tissue such as the collateral
ligaments, the patellar tendon, the fat pad
and ultimately the subcutaneous layer and
the skin. Arthrofi brosis8 of the knee is the
end stage, in the severest case it results in
patella baja9.
Six biological origins of a painful stiff knee
have to be considered if mechanical factors
have been ruled out:
(1) Recurrent hemarthrosis
(2) Infection
(3) Herotopic ossifi cation
(4) Allergy
(5) Complex regional pain syndrome.
Recurrent hemarthrosis is a clinical diagnosis
in the early postoperative periode. Aspiration
is the fi rst diagnostic and therapeutic method
of choice, but if recurrency persist arthrotomy
is occasionally required. Aspiration is also
mandatory if pain and swelling increase in the
early postoperative days, accompanied by
temperature elevation and increase of white
blood count (WBC). Elevation of C-reactive
protein (CRP) is normal in the fi rst 3 postoperative
weeks and is therefore useless in the
early postoperative period.
However, if it does not drop constantly or rises
even further, infection must be suspected. If
WBC and CRP rise after months or years
hematogenous infection is suspected. Satisfactory
diagnosis can only be made if culture
of synovial fl uid reveals a germ. If no germ is
identifi ed, diagnosis may remain uncertain.
Particularly a low-grade infection, where the
postoperative course is unsatisfactory and
the knee remains warm, swollen, painful,
and with reduced arc of motion, is diffi cult to
manage. The knee may not be differentiated
from a condition with has been known by several
terms: algodystrophy, refl ex sympathetic
dystrophy, M. Sudeck, causalgia and others.
Complex regional pain syndrome (CRPS) is a
description created by the IASP (International
Association for the Study of Pain) for an infl
ammatory disease after surgery or trauma
which summarizes these terms. CRPS I is
associated with skin nerve damage during
surgery, and CRPS II is not. Ethiopathology
is not well understood, but in both cases the
sympathetic (autonomous), sensory and motor
nerve system is disturbed. The symptoms
of acute arthrofi brosis as a consequence
of CRPS consist of pain at rest, which can
range between moderate and severe, hyperalgia,
dysaesthesia and skin temperature
dysregulation. The skin of the index knee can
be colder (in 20% of the cases) or warmer
(in 80% of the cases) than the contralateral
knee. Skin color turns into red because of increased
vascularisation, or it can be pale and
cyanotic if skin vascularisation is decreased.
Hyperhydrosis may predominate (50% of the
cases) over hypohydrosis (20% of the cases).
CRPS I may have a less severe course and
patients suffer often only of pain during knee
motion. Attemts do differentiate CRPS from
low-grade infection using modern diagnostic
tools such as positron emission tomography
are frustrating10. Arthroscopy is indicated to
obtain synovium biopsy for tissue culture and
histological examination may occasionally
help to rule out either CRPS or infection.
Heterotopic ossifi cation is easy to detect
on x-rays in the advanced stage, the early
stage may best be evaluated with technetium
scans.
Allergy to orthopedic implants is a controversial
tissue11. Fact is that patients may be
allergic to kalium dichromate, nickel sulfate,
and cobalt chloride, as well to methyl methacrylate
and antibiotics used with bone cement,
all materials used with orthopaedic implants.
There is no evidence so far to support the
hypothesis that these materials induce tissue
reactions that may result in infl ammation and
cell proliferation resulting in swelling, arthro-