Notas / Notes - Active Congress.......

JUEVES / THURSDAY
122
12.15 - 14.15 h
RODILLA / KNEE
Unicompartimentales / Unicompartimentals
Modereador: Peter McLardy-Smith
UNICOMPARTMENTALS: OSTEOTOMY,
INTERPOSITIONAL DEVICE OR
UNICOMPARTMENTAL?
Thomas S. Thornhill M.D., John B. and
Buckminster Brown
Professor of Orthopedic Surgery, Harvard Medical School
Orthopedist-in-Chief, Brigham and Women’s Hospital
Boston Massachusetts
California (USA)
In the 1970’s and early 1980’s, unicompartmental knee replacement
(UKA) in our institution was utilized in 30-50% of
patient’s undergoing arthroplasty for osteoarthritis. With improvements
in total knee replacements (TKA), difficulties in
patient selection of UKA and concerns over long-term success
of UKA this procedure fell out of favor. In the 1990’s only 5-
8% of osteoarthritic patients in our institution underwent UKA,
while in other institutions the procedure was abandoned. In
the past few years, UKA has had a rebirth based primarily
on the “mantra” of minimal invasive surgery. It is heralded
as a “interval arthroplasty” or “prelude to a total knee”. While
the pattern of osteoarthritis has not changed the incidence
of UKA has risen sharply leading to concerns of patient selection
and, with minimal exposure, difficulties in interoperative
joint assessment and component implantation.
These concerns are validated by a review of the literature
in the 1970’s and 1980’s, which indicated that the most common
causes of failure included poor patient selection, difficulty in
intraoperative decision making when considering UKA vs.
TKR and technical error during surgery. UKA is contraindicated
in cases of inflammatory arthritis; significant involvement of
2 or more compartments, subluxation, significant extra articular
deformity, or the presence of active or untreated infection.
UKA is relatively contraindicated in obese patients,
those with significant chondrocalcinosis and in anterior
cruciate deficient knees. With these criteria applied only 5-
8% of osteoarthritic patients should undergo UKA. Have we
stretched the indications for this procedure? While many
patients previously considered for tibial osteotomy now may
be considered for UKA this may explain a portion of the
increased numbers. The increase utilization of both marrow
based and cell based therapies for cartilage repair however
should offset this increase.
Joint inspection at the time of arthroplasty has always been
an important factor in considering UKA vs. TKA. The status
of the uninvolved patella femoral compartments, the presence
or absence of significant osteophytes, the presence or absence
of the anterior cruciate ligament, the wear pattern of the involved
compartment and the extent of inflammation have all
been considered as important determinants. Another potential
concern in minimally invasive UKA is the inability to carefully
inspect the remaining joint.
Finally, technical issues are a major factor in determining
the success or failure of UKA. In one series from our institution,
we found a 17% incidence of technical issues that lead to
early failure. These included under-correction, over correction,
component mal-rotation, residual incongruity, non-parallelism,
instability and wear of the unresurfaced compartments. UKA
in fact is a technically more demanding procedure than TKA.
If 70% of the total knees done in the US are done by people
who do less than 30 a year and if UKA patients represent
only a fraction of the knee arthroplasties performed, there
is a question of the critical number necessary to maintain
proficiency with this procedure. Moreover, UKA through
minimally invasive techniques often has less instrumentation
than either TKA or UKA through standard incisions. As component
systems are driven towards minimally invasive surgery,
the precision of the instrumentation may necessarily be
compromised.
UKA remains a useful procedure for treatment of patients
with osteoarthritis and minimally invasive techniques certainly
have an advantage. It is hoped that the problems recognized
in the 70’s and 80’s are not revisited in this era of minimally
invasive surgery. Below is an outline of the options available
to treat Unicompartmental Arthritis.
Current indications for specific treatment in
non-inflammatory osteoarthritis
Arthroscopy- evidence of internal derangement, normal
alignment, preservation of joint space
Arthroscopic debridement
-impinging osteophytes (intercondylar, patellofemoral)
-sealing techniques (not validated)
Open debridement-limited