抄録
Despite performing patellar resurfacing in total knee arthroplasty (TKA), a significant proportion of patients still experience anterior knee pain (AKP). Here, we report a patient with AKP following TKA with patellar resurfacing for whom we successfully treated the lateral part of the patella with resection, in an area that was not covered by the patellar component.
Case: A 78-year-old woman experienced increasingly worse AKP that began three years after undergoing primary TKA with patellar resurfacing. The original surgery had been undertaken for spontaneous osteonecrosis of the medial femoral condyle. On a physical examination, there was tenderness at the lateral side of the patella. Radiographic examination did not demonstrate loosening of the implants, and there were no signs of infection.
The presumed cause of the AKP was thought to be due to impingement between the lateral part of the resurfaced patella and the femoral component from the original implant through malposition. In this case, the femoral component was implanted with 9-degrees of internal rotation in relation to the clinical epicondylar axis.
As a result, the patient underwent reoperation, which was performed through the standard medial parapatellar approach. The lateral part of the patella that was not covered with the patellar component was removed with an oscillating saw. Lateral release was not performed.
Postoperatively, her AKP was significantly improved. The pain visual analog scale (VAS; scale 0-10) improved from 8.5 down to 1.0. Her Knee Society Knee Score improved from 33 to 83, and her Knee Society Function Score improved from 45 to 85, respectively.
Since AKP after TKA can have multiple etiologies, it is difficult to specify all causes and to treat the pain effectively. In this case, we were able to identify the impingement as a cause of AKP in this patient. If malposition of the implanted component is the cause of AKP, revision TKA is a possible solution. However, revision TKA is more invasive than lateral osteotomy of the non-covered component of the patella. We believe that in order to prevent future AKP following TKA, it is important to prevent this aforementioned impingement and, therefore, we perform this lateral osteotomy procedure on all primary TKA patients.
