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INTRODUCTION
The use of unicondylar knee arthroplasty
(UKA) as a treatment option for degenerative
arthritis of the knee has been a contentious
issue since its introduction in the early 1970s.
Initial prostheses yielded variable results, and
this unpredictability resulted in broadly low
levels of usage. Instead total knee arthroplasty
(TKA) emerged as the treatment of choice in
this patient group; frequently utilized in place
of UKA for the management of unicompart-
mental disease.
Over the last two decades advances in UKA
implant design and surgical technique have
generated promising survivorship statistics
(84-100% at 10 years and 93% at 15 years) [1],
reduced duration of hospital stays and rehabi-
litation, and good post-operative function. A
classic study of individuals with UKA in one
knee and TKA in the other for example, found
that although most patients were not able to
detect a difference between their UKA and
TKA knees, 31% preferred their UKA knee;
more than twice the number that felt their TKA
knee was the better knee [2]. The physical
basis for this preference, although open to
interpretation, may relate to an improved range
of motion (ROM) [2, 3] and general preserva-
tion of joint kinematics in these knees. In
contrast with TKA, the cruciate ligaments are
conserved in UKA; with normal cruciate func-
tion maintained up to ten years post-surgery
[4, 5]. These biomechanical advantages of
UKA are reflected in comparatively high rates
of return to activity (67-95% for UKA [6-9]
versus 34-88% for TKA [10-12]); with direct
comparisons indicating that UKA provides a
significantly greater return to sports, although
over a broadly equivalent time-scale [9].
As a consequence of these and other similar
statistics UKA is steadily increasing in appli-
cation; at a rate of increase of around 30% year
on year in the USA for example [13]. Despite
this general trend, total usage of UKA remains
low relative to TKA, which has historically
been perceived as the more reliable procedure.
A recent survey of UKA and TKA implant
usage in the USA indicated that UKA accounts
for less than 8% of all knee arthroplasty pro-
cedures [13], and similar statistics have been
obtained several other countries including the
UK (8%) [14], as well as Canada (8%) [15],
Australia (11.8-15.1%) [16] and Sweden (9.4-
11.7%) [17].
Survivorship data now suggest that the longi-
tudinal durability of UKA is good, and that at
least when appropriately monitored, revision
of UKA to TKA can be successful, ultimately
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ROBOT ASSISTED UNICONDYLAR KNEE
ARTHROPLASTY IS COST-EFFECTIVE
J.P. COBB, CH.A. WILLIS-OWEN, K. BRUST, H. ALSOP