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Revision of failed unicompartmental knee arthroplasty


One of the principal advantages of unicompartmental knee arthroplasty (UKA) is its conservative nature. Ideally, after a UKA, any future revision can be carried out with the use of primary total knee arthroplasty (TKA) components and the result can be comparable to a primary arthroplasty. Initial experience from the 1980s indicated that this might not be the case. As experience with primary UKA was gained, however, subsequent reports confirmed its conservative nature.

Tibial revision

For a UKA to be conservative, it is important that surgeons follow the basic principle of performing a minimal initial tibial resection (see Chapter 6 ). By doing so, tibial augmentation methods such as modular wedges will rarely be required ( Fig. 10.1 ). When initial tibial resection has been excessive ( Fig. 10.2 ), augmentation methods and extended tibial stems will be required.

Fig. 10.1, (A) An anteroposterior (AP) radiograph prior to a unicompartmental knee arthroplasty showing a planned medial tibial resection based on a conservative lateral resection for a total knee arthroplasty. (B) A postoperative radiograph in the same patient showing the proper execution of the conservative preoperative plan. (C) An AP radiograph in the same patient 3 years later after revision for femoral component loosening. Standard components were utilized without the need for any augmentation method.

Fig. 10.2, A postoperative anteroposterior radiograph of a unicompartmental knee arthroplasty exhibiting excessive tibial resection that will compromise any future revision.

Loss of tibial bone stock following a medial UKA can also be due to subsidence of the tibial component, although osteolysis compromising tibial bone stock is rare. An example of this is shown in Fig. 10.3 . In this case, the tibial component had slowly subsided over a 20-year period. The resultant defect was significant, but was mostly contained by cortical bone and could be treated with a tibial component with a 30-mm stem extension and the use of local autogenous bone graft harvested from standard total knee bone resections.

Fig. 10.3, (A and B) An anteroposterior (AP) and lateral radiograph showing a loose subsided tibial component 20 years after the index unicompartmental knee arthroplasty. (C and D) An immediate postoperative AP and lateral radiograph following revision with a standard femoral component, an extended-stemmed tibial component, and the use of autologous bone graft to fill the contained defect (harvested from the femoral and tibial bone resections). (E and F) A 1-year follow-up AP and lateral radiograph showing apparent incorporation of the bone graft without component subsidence. The patient was asymptomatic at 9-year follow-up.

After failed lateral UKA, loss of tibial bone stock is also rarely a problem ( Fig. 10.4 ). This is most likely because tibial bone preparation for lateral UKA is intrinsically conservative (see Chapter 8 ).

Fig. 10.4, (A) An anteroposterior radiograph showing a failed lateral unicompartmental knee arthroplasty. (B) A postoperative radiograph of the same patient following revision using standard components.

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