NaF PET assessment of bone metabolic changes around the femoral canal by intramedullary femoral alignment technique in total knee arthroplasty

Abstract

We used the NaF PET scan to assess osteometabolic changes around the distal half of the femoral canal by intramedullary (IM) drill for femoral IM guiding rod insertion in total knee arthroplasty. Gentle IM rod insertion and focused attention can minimize surgical stress-induced biological reaction of the femoral IM canal.

Keywords: NaF; PET; extramedullary; intramedullary; total knee arthroplasty.

Figure 1

A 76‐year‐old woman was treated with a left TKA for osteoarthritis of the knee. Femoral and tibial cuts were achieved with preoperative planning using intramedullary femur jig and extramedullary tibial jig, respectively. (A) ¹⁸F‐sodium fluoride ([¹⁸F] NaF) bone positron emission tomography images, performed 2 wk after implantation, showed high bone metabolic activity at the distal half of the left femur in addition to the bone‐prosthesis interface called “hammer sign” (arrow). (B and C) X‐ray examination before and after joint arthroplasty

Figure 2

An 86‐year‐old woman was treated with simultaneous bilateral TKA for knee osteoarthritis. For bilateral replacement, femoral and tibial cuts were achieved with intramedullary femur jig and extramedullary tibial jig, respectively. Femoral intramedullary rods were slowly inserted with scrupulous care. (A) Postoperative ¹⁸F‐sodium fluoride ([¹⁸F] NaF) bone positron emission tomography showed that upregulation of the tracer uptake at the distal half of the right femur almost completely disappeared, although a slight bone metabolic activity at middle third of the left femur (arrow) was detected. (B and C) X‐ray examination before and after joint arthroplasty

Figure 3

An 81‐year‐old woman, who suffered from right femoral intertrochanteric fracture 5 mo earlier, was treated with simultaneous bilateral TKA for knee osteoarthritis. (A) Bilateral TKA was performed with the extramedullary guide for the right and the IM alignment system for the left femur. The “hammer sign” was not observed in not only the right femur but also the left, indicating that slow insertion of an intramedullary rod with scrupulous care can reduce the damage to the femoral canal to the same level as that in extramedullary femoral alignment guide system. (B and C) X‐ray examination before and after joint arthroplasty