Review Question - QID 220299

This 56-year-old male underwent a previous high tibial osteotomy (HTO) and now has knee osteoarthritis in the setting of patella baja. Of the listed options, the only technique to improve his baja is to add distal femur augments, thereby lowering the joint line (Answer 5).

Total knee arthroplasty (TKA) following HTO can present challenges for a number of reasons, with the most commonly seen effect from the procedure being patella baja, which is believed to be secondary to either shortening of the patellar tendon during tibial osteotomy or from scarring of the patellar tendon post-operatively. Several techniques have been described to mitigate this side effect, including lowering the joint line. This can be achieved by making a larger cut on the tibia and adding distal femur augments. Other techniques include placing the patellar component superiorly and performing a tibial tubercle transfer to a more cephalad position. In severe cases, a patellectomy can be performed.

Parvizi et al. provided a retrospective review of 166 cemented TKAs (116 patients) who underwent previous HTOs an average of 8.6 years before their TKA. While acknowledging that the procedure reliably improves knee function and range of motion, there is a high revision rate, which was 8% at an average of 5.9 years. Moreover, there were high rates of radiographic loosening. After analysis, the authors concluded that male gender, increased weight, young age, laxity, and limb malalignment served as risk factors for early failure.

Meding et al. reported on 39 patients who underwent bilateral TKAs, one side of which had previously undergone HTO. No significant difference in functional scores we found between the HTO and non-HTO knees, while rates of residual pain, overall alignment, and complications following TKA remained similar. The authors ultimately concluded that outcomes between those with and without previous HTO are similar and that previous HTO likely plays a minimal role in outcomes.

Figures A and B demonstrate an AP and lateral of a left knee exhibiting patella baja in the setting of a previous HTO.

Incorrect Answers:
Answer 1: Placing the patellar component inferiorly would worsen the patient's patella baja.
Answer 2: Increasing the polyethylene size, thereby elevating the joint line, would increase the patient's patella baja.
Answer 3: Downsizing the femoral component would decrease the anterior-posterior diameter, and would not affect patellar alignment.
Answer 4: Performing a tibial tubercle transfer to a more caudad position would worsen the patient's patella baja.