Total Knee Replacement in the Varus Knee
– this is obviously the more common scenario than the valgus knee – should have a unified approach to the release!
– start medially, and release everything along the medial side – meniscotibial ligament, medial meniscus, deep MCL, and all posteromedial capsule back to and including the PCL. May also need to release some of semimembranosus off the posteromedial tibia. Then subperiosteally lift off the proximal 3-5 cm of the proximal medial tibia, elevating (not releasing) the superficial MCL and the pes anserinus.
– then cut the ACL and patellofemoral ligaments, undercut the fat pad and subperiosteally strip along the superolateral side to mid-plateau
– try everting the patella – watch the patellar insertion! If too tight, continue the lateral dissection abit more, and try again. If still too tight, do a rectus snip. DO NOT PEEL THE PATELLAR TENDON INSERTION!
– do your tibial and distal femoral and AP femoral cuts, then balance the ligaments with laminar spreaders or blocks.
If the patella subluxes laterally:
1. Check your components!
– Did you internally rotate the tibial component (Harry Rubash thinks that this is very common) and thus lateralize the tubercle.
– Did you internally rotate the femoral component (or fail to externally rotate it sufficiently). This increases the Q angle and medializes the trochlear groove.
– Did you lateralize the patellar component – remember, the anatomic median ridge of the patella actually sits 3-4 mm MEDIAL to the anatomic midline of the patella – if you put it in the anatomic midline, you will be too far lateral!
2. Do the lateral release +/- preservation of the superior lateral geniculate artery
3. Consider advancing the VMO – (ie. a proximal realignment); ask yourself if this is technically possible.
4. Consider doing a distal realignment – osteotomizing the tubercle and moving it medially.