Total Knee Replacement with Flexion Contracture
– this is common particularly in the inflammatory arthritides – rheumatoid, psoriatic, hemophilic – because they hold their knee flexed as that is the least painful for them.
– they may also have concomitant varus or valgus deformities
– do the approach and do the medial/lateral soft tissue balancing first.
– then decide how to deal with the flexion contracture. The basic approach is to start with soft tissue releases, then move on to bony changes if absolutely necessary.
– start with releasing the PCL – even though this opens up the flexion space more than the extension space, these severe deformities are a lot easier to deal with by starting with the obliteration of the PCL (how would you balance the PCL in a 25o valgus knee with a 30o flexion deformity anyways?)
– make sure all the medial and lateral osteophytes are resected so that the medial/lateral soft tissues aren’t draped over them.
– start dealing with the flexion contracture by flexing the knee up fully, and removing the osteophytes off the posterior condyles – then check the extension space again.
– if still tight, flex up the knee again, and use an elevator to elevate the capsule off the posterior condyles and femur; keep checking as you release, but you may have to go all the way and release the entire capsule and proximal heads of the medial and lateral gastrocs.
– if still tight in extension after this (rare) you have to think about doing bony work. The way to increase the extension gap is to cut more of the distal femur back – unfortunately, you will raise the joint line if you do this, so don’t be too aggressive. Raising the joint line 8 mm apparently really fucks up the extensor mechanism.
– the vast majority are manageable by getting rid of the posterior osteophytes first, then stripping the posterior capsule off next, then stripping the gastrocs off the distal femur. (ie – soft tissue procedures usually work!) Only after then should you consider resecting more off the distal femoral cut.
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