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Ninety-one knees (47.6%) fell into the three
patterns that were deemed potential candidates
for UKA. A further 60 knees (31.4%) were
classified as M, MMP, MLP or ALP; knees in
this group would be debatable candidates for
UKA. Twenty knees (10.5%) were patterns
MP and LP with isolated patello-femoral
disease, which could be considered for isola-
ted PFJ replacement. Twenty knees (10.5%)
had radiographic signs of bi compartmental
tibio-femoral, tri-compartmental or post trau-
matic (Other) loss of joint space irrefutably
necessitating TKA. Reproducibility of the
classification was high, with and intra-obser-
ver kappa statistic of 0.947 and an inter-obser-
ver score of 0.899.
Financial costs
Surgery
The cost of the components:
- A PFC TKA including patellar resurfacing
was £2,322 plus (VAT).
- The cost of a 2 mixes of Palacos cement is £50.
- The total cost for comparison was £2,372.
- An Oxford Phase III UKAwas £1,222 plus VAT.
- A single mix of cement brings the cost for
comparison to £1,247.
- The device cost of a RUKAis quoted at £1,100.
Based on these calculations a typical UKA
saves approximately £1,125 over a typical
TKA, and a RUKA saves almost £150 on a
conventional UKA.
The cost of sterile instrumentation sets
The cost of sterile instrumentation sets was
hard to assess, as they were put in ‘free’, but
the sterilization costs alone for the TKA were
£300, while for the UKA were £200. The ste-
rilization costs of the small single tray of ins-
truments for the acrobot was £40.
The cost of the acrobot
The device is sold for £90,000, with a mainte-
nance contract of £10,000 per year. When
amortised over a 3 year period, based upon
300 cases performed, the cost per case was
estimated at £330.
The hospital episode
Mean hospital LOS as reported in the NJR was
5.9 days following a primary UKA compared
with 8.3 days following a cemented TKA pro-
cedure; a difference of 2.4 days. This publi-
shed figure was corrected for age, gender, ASA
grade, and provider type by the authors of the
NJR to 2.1 days. Management figures from
our 20 bedded unit showed running costs of
£200 per bed per day. Hence the costs saving of
UKA over TKA are estimated at £420 per case.
DISCUSSION
Currently UKA accounts for only around 7-
15% of all knee arthroplasty procedures [13-
17], and TKA remains the predominant surgi-
cal treatment offered for unicompartmental
knee osteoarthritis in the UK today. Here we
have shown that candidacy for UKA is much
wider; accounting for 47.6% of knee arthro-
plasties in a series of 200 consecutive knees.
Consistent with previously published data [2,
30, 31] we have also shown that self-perceived
functional outcome of UKA is superior to that
of TKA, based on a robust and well validated
measurement instrument; the Total Knee
Questionnaire (TKQ). Finally we also calcula-
te that UKA offers a substantial cost saving
over TKA, totaling £1,545 per knee (£1,125
for the surgery and £420 for the hospital stay).
Together these data suggest that UKA is an
underutilized procedure, offering significant
functional and financial advantages over TKA.
If our findings can be extrapolated, then of the
57,597 knee arthroplasties carried out in the
UK per year, 47.6% of cases (27,416) may
potentially be suitable for UKA. With a cost
saving of £1,545 per case, annual savings
could amount to in excess of £42 million; a
saving also likely to be reflected in patient-
perceived functional outcome. Whilst a num-
ber of assumptions have been made in the cal-
culation of these costs, the estimates derived in
this study are comparable with those of
Shakespeare et al. where cost savings were
calculated to be £1,435 per knee in the NHS,
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229