PMC8007382_01
Radiographs of both femurs. The initial right femoral plain radiograph shows an atypical subtrochanteric fracture (a). On the contralateral side, no fracture is detected at the subtrochanteric site (b). The intramedullary nail is inserted during primary surgery with osteosynthesis (c). The intertrochanteric screw is broken (white arrow) (d), and the fracture site is more displaced than that shown in (c). Revision surgery is then performed. The intramedullary nail is reinserted, and the lag screw is inserted in the femoral neck and head (e).
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A radiograph showed a right atypical femoral subtrochanteric fracture (Figure 1(a)), which fulfilled the criteria for AFF, established by the American Society for Bone and Mineral Research (ASBMR) task force. No fracture was found on the lateral cortex of the contralateral side (left) of the femur (Figure 1(b)). A primary surgery was then performed, and an intramedullary femoral nail was used (Figure 1(c)). However, implant breakage was detected at postoperative 8 weeks (Figure 1(d)), and a revision surgery was subsequently performed. The entry point for the revised intramedullary hole was created to prevent varus position, and good anatomical reduction was achieved (Figure 1(e)).
Time course of radiographs after the revision surgery. Three months after the revision surgery, callus formation is detected at the fracture site (a). At 13 months after the revision surgery, the fracture site has healed (b).
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At 12 weeks after the revision surgery, full weight-bearing was advised because callus formation was detected on follow-up radiographs (Figure 2(a)). Finally, the fracture healed by 13 months after the revision surgery (Figure 2(b)), and the patient could walk without support and independently perform activities of daily life.
Bone staining (Villanueva bone staining) of the biopsied iliac bone. Trabecular bone (a) x100, osteoid tissue (b) x200, and osteoclasts (black arrow) (c) x 200 are detected. Bar: (a) 100 mum; (b) and (c) 50 mum.
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Osteoclasts were detected around the trabecular bone (Figure 3).
Microcracks are identified using basic fuchsin staining. Fuchsin-positive microcracks are detected (black arrowheads in (a, b) in the cortex).
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Seven microcracks were found in the cortex of the fracture site (Figure 4), with a crack density of 0.79 N/mm2 (Table 4).