LIVRE JDG 2014

What are the limits for Unicompartimental Knee Arthroplasty?

197

Correction of flexion

deformity

Many surgeons consider flexum deformity as

an absolute contraindication for UKR. Before

evaluate flexum as irreducible and consider

TKR as the unique solution, some tips should

be performed.

First of all, evaluate it under anesthesia. Often

flexum is only a consequence of knee pain.

After that, give space to the ACL! Removing

any osteophyte from the notch will free the

ACL. Then, remove any posterior osteophyte.

This should be done after tibial and femoral cut

to obtain enough space for working posteriorly.

After component trial position, range of motion

should be tested. If some degrees of flexum are

still present, a dosed elongation of the knee

flexors should be done. To do this, no surgical

acts should be done. Agentle manual stretching

is enough. This procedure takes time because

theknee shouldbemaintained inhyperextension

for some minutes, but it is very effective.

Undercorrection of

the deformity

Tibio-femoral wear in knee osteoarthritis (OA)

often causes varus or valgus deformity. The

location of tibio-femoral wear (medial or lateral

compartment) is often a consequence of the

morphotype [12].

A native valgus knee can develop lateral OA,

a native varus knee can develop medial OA.

Osteoarthritis worsens the amount of the

deformity, and this fact should be considered

in UKR. The tibial and femoral cuts should

be done in order to correct the deformity

caused by cartilage wear, not the one

determined by the morphotype. The aim is to

respect the joint line. Postoperative

mechanical axis should be hypo-corrected,

proportionally to preoperative deformity and

constitutional varus-valgus (fig. 3). This

shrewdness will not alter the native knee

biomechanic and will not cause overstress on

the opposite compartment.

Fig. 3: 83 years old man with right knee lateral OA and left knee medial OA. He had simultaneous

bilateral UKR. Postoperative X-rays showed undercorrection of the coronal deformity to respect

the native morphotype.