case_images: PMC7364197_01
case_images: Preoperative plain radiography and computed tomography (CT). (a) Anteroposterior and (b) lateral views. No remarkable findings. (c) Axial and (d) three-dimensional CT images show the nidus (white arrowhead) in the distal humerus and reactive bone at the olecranon fossa.
case_images: CRIOR2020-4034989.001.jpg
case_images: PMC7364197_01_CRIOR2020-4034989.001.jpg
case_images: fig1
case_images: Plain radiography of the right elbow showed no remarkable finding (Figures 1(a) and 1(b)). Plain CT showed a radiolucent round lesion of 4 mm diameter at the distal humerus and reactive bone in the olecranon fossa (Figures 1(c) and 1(d)).
case_images: Preoperative photograph. (a) Elbow flexion and (b) extension.
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case_images: PMC7364197_01_CRIOR2020-4034989.002.jpg
case_images: fig2
case_images: The respective range of motion for the right and left extremities was as follows: elbow flexion, 115  and 145 ; elbow extension, -35  and 5 ; forearm pronation, 90  and 90 ; and forearm supination, 90  and 90  (Figures 2(a) and 2(b)).
case_images: Photographs during arthroscopy. (a) Synovectomy. S: synovitis. (b) Resection of the reactive bone (R). (c) The nidus (N) under the reactive bone. (d) The nidus. (e) Resection of the nidus using a bone chisel (C). (f) Postresection of the nidus.
case_images: CRIOR2020-4034989.003.jpg
case_images: PMC7364197_01_CRIOR2020-4034989.003.jpg
case_images: fig3
case_images: Synovitis was filled in the joint, and it was resected for an appropriate surgical field using a shaver (Figure 3(a)). At the lateral side of the olecranon fossa, a red solitary lesion considered a tumor was noted after the resection of white reactive bony lesion (Figures 3(b)-3(d)). A bony chisel of 8 mm width was used to excise the tumor en bloc (Figure 3(e)). After excision, the cortical and cancellous bone around the lesion was resected until normal tissue was observed (Figure 3(f)).
case_images: Histopathologic photograph. (a, b) Histological sections stained with hematoxylin and eosin show irregular osteoid and lining osteoblasts with scattered osteoclasts and significant vascular stromal tissue. Scale bar: 200 mum (a) and 50 mum (b).
case_images: CRIOR2020-4034989.004.jpg
case_images: PMC7364197_01_CRIOR2020-4034989.004.jpg
case_images: fig4
case_images: Histological examination showed OO (Figures 4(a) and 4(b)).
case_images: Postoperative computed tomography (CT). (a) Axial and (b) three-dimensional CT images show appropriate resection of the nidus.
case_images: CRIOR2020-4034989.005.jpg
case_images: PMC7364197_01_CRIOR2020-4034989.005.jpg
case_images: fig5
case_images: Postoperative plain CT showed an appropriate resection of the nidus (Figures 5(a) and 5(b)).
case_images: Postoperative photograph. (a) Elbow flexion and (b) extension 2 years postoperatively.
case_images: CRIOR2020-4034989.006.jpg
case_images: PMC7364197_01_CRIOR2020-4034989.006.jpg
case_images: fig6
case_images: Range of motion of the right elbow was as follows: flexion, 135 ; extension, -15  (Figures 6(a) and 6(b)).