Discussion to Chap. 52: Patellofemoral Pain After Cruciate Retaining Total Knee Replacement

Fig. 1

Radiographs (anterior-posterior and lateral-a and long leg view-b) of the left knee showed a primary cruciate retaining mobile-bearing TKR. No signs of loosening or infection. The tibial component was well positioned. No over- or undersizing of the TKR components. A patella infera was seen which was attributed to a proximalisation of the joint line. In addition, there was a significantly flexed femoral TKR component

Fig. 2

99mTc-HDP-SPECT/CT images of the left knee showed no increased tracer uptake around the femoral and tibial TKR component indicating a well-fixed TKR and no infection. There was markedly increased bone tracer uptake of the patella indicating an increased loading of the patella due to a patella infera

Fig. 3

Measurements of the TKR component position using a customised and validated software showed – 12° flexion (left) and 5° internal rotation (middle) of the femoral TKR component and 5° posterior slope of the tibial TKR component (left up) and 12° external tibial rotation (left bottom)

Questions

What is your differential diagnosis now?

What are your next steps in diagnostics?

99mTc-HDP-SPECT/CT confirmed that there was no loosening or infection. Hyperflexion of the femoral component of the TKR on the left side (12°) with a consecutive ventral, over-shielding, and patellar stress at the upper pole of the left patella baja (Figs. 2 and 3).

Questions

What is your diagnosis and proposed treatment?

How would you address the femoral component malposition?

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