Abstract
Patients presenting with arthrosis following high tibial osteotomy (HTO) pose a technical challenge to the surgeon. Slight overcorrection during osteotomy sometimes results in persisting medial unicompartmental arthrosis, but with a valgus knee. A medial UKA is desirable, but will result in further valgus deformity, while a TKA in someone with deformity but intact cruciates may be a disappointment as it is technically challenging. The problem is similar to that of patients with a femoral malunion and arthrosis. The surgeon has to choose where to make the correction. An ‘all inside’ approach is perhaps the simplest. However, this often means extensive release of ligaments to enable ‘balancing’ of the joint, with significant compromise of the soft tissues and reduced range of motion as a consequence.
As patients having HTO in the first place are relatively high demand, we have explored a more conservative option, based upon our experience with patient matched guides.
We have been performing combined deformity correction and conservative arthroplasty for 5 years, using PSI developed in the MSk Lab. We have now adapted this approach to the failed HTO. By reversing the osteotomy, closing the opening wedge, or opening the closing wedge, we can restore the obliquity of the joint, and preserve the cruciate ligaments.
Technique: CT based plans are used, combined with static imaging and on occasion gait data. Planning software is then used to undertake the arthroplasty, and corrective osteotomy.
In the planning software, both tibial and femoral sides of the UKA are performed with minimal bone resection.
The tibial osteotomy is then reversed to restore joint line obliquity. The placing of osteotomy, and the angling and positioning in relation to the tibial component are crucial. This is more important in the opening of a closing wedge, where the bone but is close to the keel cut.
The tibial component is then readjusted to the final ‘Cartier’ angle.
Patient guides are then made. These include a tibial cutting guide which locates both the osteotomy and the arthroplasty.
At operation, the bone cuts for the arthroplasty are made first, so that these cuts are not performed on stressed bone. The cuts are not in the classical alignment as they are based upon deformed bone so the use of patient specific guides is a real help. The corrective osteotomy is then performed. If a closing wedge is being opened, then a further fibular osteotomy is needed, while the closing of an opening wedge is an easier undertaking.
Six cases of corrective osteotomy and partial knee replacement are presented. In all cases, the cruciates have been preserved, together with normal patello-femoral joints.
Patient satisfaction is high, because the deformity has been addressed, restoring body image. Gait characteristics are those of UKA, as the ACL has been preserved and joint line obliquity restored.
