PMC5448053_01
Plain radiographs of the bilateral knee of the patient with rheumatoid arthritis before and after Miller-Galante II Total Knee Arthroplasty performed 16 years earlier. (a) Preoperative plain radiograph shows bilateral rheumatoid arthritis of the knee categorized as Larsen grade 4. (b) Postoperative plain radiograph shows a femorotibial angle (FTA) of 174  on the right side and 183  on the left side. The left side shows varus malalignment.
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Our patient was a 60-year-old woman who had undergone bilateral MG II (Zimmer) total knee arthroplasty for rheumatoid arthritis of the knee (Larsen grade IV) in our department 16 years earlier (Figure 1).
Follow-up plain radiograph obtained 15 years after surgery shows no change in the alignment of the right side and obvious deterioration of the varus malalignment (FTA of 190 ) of the left side.
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A follow-up plain radiograph taken 15 years after arthroplasty revealed a deterioration of the varus malalignment of the tibia (Figure 2).
Follow-up plain radiograph obtained 16 years after the surgery shows disappearance of the medial joint space, subsidence of the broken baseplate, and osteolysis under the medial compartment (arrow).
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Plain radiographs taken at this time showed further distortion of the tibial component of the left knee with obvious fracture of the tibial baseplate and osteolysis under the broken component (Figure 3).
Gross appearance at revision surgery. (a) Severe metallosis is observed within the knee joint. (b) Polyethylene insert is heavily worn and broken at the posteromedial portion. (c) Coronal baseplate is fractured from the posteromedial corner to the posterior cruciate ligament recess (arrow). Subsidence of the posterior broken fragment of the baseplate is apparent.
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Perioperatively, we observed severe metallosis within the knee joint (Figure 4(a)). The polyethylene insert was obviously worn and broken at the posteromedial site (Figure 4(b)). After the broken polyethylene insert was removed, a coronal fracture was found at the posteromedial portion of the tibial component and there was subsidence of the posterior metal tray fragment (Figure 4(c)). Medial augmentation was required to correct the bony deficiency (Figure 4(d)).
Follow-up plain radiograph obtained 17 years after initial surgery of the right-side implants shows normal alignment is maintained, with no evidence of stress shielding or loosening.
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Remarkably, the MG II prosthesis on the right side was properly aligned, surviving for 17 years after primary surgery (Figure 5).
(a) Gross observation of the retrieved broken tibial baseplate reveals that the fracture line extended in a coronal direction from the medial corner to the posterior cruciate ligament (PCL) recess. (b) Gross observation of the undersurface of the tibial baseplate shows uneven bone attachment surrounding the medial fracture line but even bone attachment at the posterolateral portion. (c) Surface of the break is complex rather than with regular fracture waves. A focal stair-step pattern can be observed grossly at the medial corner of the PCL recess (arrow), indicating a fatigue fracture. Scanning electron micrography shows fatigue striations (circle). (d) Retrieved polyethylene insert has severely worn medial sites that correspond to the posteromedial breakage area of the tibial baseplate. Polyethylene insert is also severely worn at the posterolateral area. (e) Retrieved portion of the fractured screw.
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Gross observation of the retrieved broken tibial baseplate revealed that the fracture line extended in a coronal direction from the medial corner to the posterior cruciate ligament (PCL) recess (Figure 6(a)). There was no evidence of bone ingrowth at the undersurface of the posterior fragment of the tibial tray, although bone ingrowth was noted under the tray anterior to the fracture line (Figure 6(b)). A focal stair-step pattern could be observed on gross examination at the medial corner of the PCL recess, and scanning electron micrography showed fatigue striations at this point (Figure 6(c)). The retrieved polyethylene insert revealed that the heavily worn medial site corresponded to the posteromedial breakage area of the tibial baseplate (Figure 6(d)). The retrieved portion of the fractured screw demonstrated the severe load that had been exerted on the posterior fractured baseplate (Figure 6(e)).