Age / Sex : 74 / F

Chief complaint :

Left knee pain. What happens in left patella?

Discussion

Answer: 

Patella osteonecrosis after TKA

Findings:

Collapse and diffuse sclerotic change in left patella

Differential Diagnosis:

Diagnosis: 

Patella osteonecrosis after TKA

Discussion:

Patella complications after TKA remain a major cause of disability. Complications included patellar fracture, osteonecrosis, patellar polyethylene (PE) wear, aseptic loosening, instability, dislocation, overstuffing, rupture of the extensor mechanism and patellar clunk syndrome

Patellar resurfacing during total knee arthroplasty remains controversial. Several patellar complications such as fracture, avascular necrosis, and instability are related to resurfacing. On the other hand, some authors report lower re-operation rates and postoperative pain when the patella is resurfaced. Attention should be directed to the ultimate patellar thick‐ ness. Whether or not to resurface should be determined based on the exact initial thickness. A thicker patella is prone to instability, whereas a thinner patella is associated with higher complication rates. Patellar fragmentation and sclerosis of the fragments are presumed to represent osteonecrosis. The osteonecrosis may be due to disruption of the vascular network of the patella during total knee replacement surgery. Medial parapatellar arthrotomy, fat pad removal, and lateral release all contribute to patellar devascularization. Evolutional osteonecrosis may lead to patellar fracture.

References:

Imaging Patellar Complications After Knee Arthroplasty. http://dx.doi.org/10.5772/53666

Patellar resurfacing complications in total knee arthroplasty. International orthopaedics 2014; 38 (2): 313-317