183 / 242
183
Introduction
ThefunctionalbenefitsoftheUnicompartmental
Knee Arthroplasty (UKA) have been firmly
established [22, 25, 33] and excellent long term
results have promoted increased interest for
this form of treatment [23, 31]. However, UKA
failure often requires revision to TKR, which
may include revision implants, and this does
not give results comparable to a TKR performed
as a primary procedure [11, 35]. It is important
that the UKA is neither perceived nor proposed
as a temporary prosthesis, nor as a conservative
treatment option. The UKA must be envisaged
as a treatment rivalling TKR for durability. Pre-
operative work up is vital to reduce the potential
causes of failure associated with improper
indications. Technical errors and failures due to
implant or material failure are dealt with in a
separate chapter.
The classic indication for UKA is isolated
unicompartmental osteoarthritis (OA), in the
absence of severe patellofemoral wear, and
with an intact ACL [18, 20]. Equally age,
weight, mobility status, level of sporting
activity and lower limb alignment should be
taken into account, in addition to indication for
the prosthesis. For teaching purposes, we will
deal with knee-related factors and patient-
related factors separately.
Knee-related factors
The Femoro-Tibial Compartment
The most frequently encountered pathology
affecting the femoro-tibial compartment is OA,
in particular early OA, before the neighbouring
compartment have been affected.Aunicondylar
prosthesis is appropriate for Stage II or Stage
III changes, according to the Ahlback
Classification, i.e. it is suitable for complete
narrowing of the femoro-tibial joint line, or a
wear-induced bony cupping of up to, both no
than 5mm [23, 30, 36]. Conversely, the patient
with only partial narrowing should be steered
towards useful adjunct treatments, as a higher
rate of failure has been reported in the absence
of documented complete joint line narrowing
[29]. There is no difference whether the arthritis
is primary or secondary to a meniscetomy.
The diagnosis of isolated unicompartmental OA
is based primarily on standard AP and lateral
x-ray weight bearing views (fig. 1). Additional
axial views of the patella allows the elimination
of radiographic patello-femoral wear (fig. 2).
Clinical examination in association with stress
views should demonstrate a reducibility of the
deformity in the frontal plane, with radiographic
early and isolated arthritis without loss of the
central pivot (fig. 3).
Preoperative Planning.
What I do Before a UKA
T. Ait si selmi, C. Murphy, M. Bonnin