LIVRE JDG 2010

yielding similar levels of functioning to prima-

ry TKA [18, 19]. Although a learning curve has

been reported in the acquisition of the UKA

technique, this curve appears to be short, and

results achieved during this period are compa-

rable with TKA [20]. Since surgical inexpe-

rience will persist as long as UKA remains an

infrequent procedure, the limitations associated

with this obstacle can be considered highly cir-

cular. There are peverse incentives that serve to

keep it that way, with higher fees paid to sur-

geons who perform TKA, and greater income

to hospitals who have the more extensive sur-

gery performed on their sites.

Robot assisted unicompartmental knee arthro-

plasty (RUKA) has not gained wide acceptan-

ce to date. However there are reports confir-

ming that the accuracy of robotic surgery deli-

vers superior function in the short and even

medium term [21, 22]. This superiority is cur-

rently limited by the devices which are still

designed for insertion using conventional

intrumentation, and by the cost of some of the

robots which are reputedly very high. By deve-

loping a novel suite of devices that only remo-

ve the bone that is necessary, and use rapid

customized manufacturing techniques, an enti-

rely new approach to knee arthroplasty may

become possible.

Accepting that a proportion of UKA cases will

require further surgery, we assert that for

UKA to attain acceptance as a viable, if not

preferable management option for unicom-

partmental osteoarthritis, several conditions

must be met:

- candidacy for RUKA must be prevalent

(allowing the accruement of surgical expe-

rience and amortizing of the cost),

- RUKA must offer significant advantages in

terms of functional outcome (in order to jus-

tify its use as a temporizing procedure in

some patients),

- RUKA must be available at a relative cost

saving (allowing ultimate conversion to

TKA where necessary).

In this study we set out to quantify the propor-

tion of knee arthroplasty cases that are suitable

for RUKA, to compare both post-operative

function and costs associated with RUKA and

TKA procedures in the same hospital, and look

at the costs and benefits

MATERIALS AND

METHODS

Applicability of UKA

We retrospectively evaluated pre-operative

radiographs from a consecutive series of 200

knees booked for arthroplasty of any sort at

Charing Cross Hospital (England). Patients

undergoing revision surgery or arthroplasty for

rheumatoid arthritis were excluded. All eva-

luations were blinded as to the type of surgery

performed (i.e. UKA or TKA). Each knee was

assessed using antero-posterior weight bearing

(AP), lateral in 45° of flexion and ‘Skyline’

patella views. The staging system of Ahlback

was applied [23] and Ahlback grade 1 or more

was considered to represent disease in a com-

partment (i.e. joint space of less than 3mm).

Osteophytes were not taken into consideration

since osteophyte formation is not localized to

the diseased compartment. Reproducibility of

classification was assessed both in terms of

intra- and inter-observer error using 20 ran-

domly selected cases.

On the AP radiographs joint space in the

medial and lateral compartments was measu-

red. On the lateral radiographs medial and late-

ral tibio-femoral compartments were again

assessed and antero-medial disease was diffe-

rentiated from medial disease. On the Skyline

view both medial and lateral patello-femoral

articulations were assessed. On this basis

12 patterns of disease were defined (Table 1)

Knees with anteromedial or lateral wear were

considered candidates for simple RUKA.

Where medial compartment wear had exten-

ded posterior to the midpoint of the medial

compartment on the lateral radiograph (the

medial group) these knees were not considered

ideal candidates as this has been taken to be a

sign of functional ACL insufficiency [24]. In

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