PMC9532597_01
(A) Anterior-posterior and (B) lateral X-ray images show a large radiolucent area in the epiphyseal part of the left distal femur. (C) Anterior-posterior and (D) lateral X-ray images after intralesional curettage combined autografting and internal fixation. (E) Anterior-posterior and (F) lateral X-ray images. (G) sagittal and (H) transverse planes on CT images after cement packing at 11 months. Sclerotic rim occurs around cement (red arrow). (G,H) Distal femur articular cartilage defects mainly lie in the patello-femoral joint (yellow arrow).
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F1
X-ray images showed a large radiolucent area of bone caused by osteolytic deconstruction in the epiphyseal part of the left distal femur (Figures 1A,B). II GCT. In August 2018, the patient underwent intralesional curettage combined with autografting and internal fixation (Figures 1C,D). Afterwards, the pain persisted in the affected knee for 11 months (Figures 1E-H), and bone cement removal plus 3D-printed modular prosthesis reconstruction for patello-femoral large osteochondral defects was performed at our hospital on 15 August 2019.
(A) Anterior view of the bone and articular cartilage defects and the circular 3D-printed guided plate. (B) Anterior view of the back components with four screw holes in three directions. (C) Anterior view of the front component connecting smoothly with the adjacent articular surface and two horizontal screws directed by guided plate. (D) Posterior view of bone defects. (E) Anterior and (F) lateral view of the 3D-printed modular prosthesis.
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F2
The front and back components were combined using a press-fit structure (Figure 2).
(A) The back components (left) combine with the front component (right) through a press-fit structure. (B) Anterior and (C) posterior and (D) lateral view of the assembled 3D-printed modular prosthesis with four screws. The prosthesis is tested on the femur model before surgery: (E) the back components fill in the bone cavity, and (F) the front component is fixed on the back components and connected to the adjacent articular surface.
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F3
A model of the prosthesis was printed and tested before the final production to verify our plan (Figure 3).
(A) The circular 3D-printed guided plate is fixed on the bone margin of the tumour. (B) The back components are inserted into the bone cavity and firmly fixed to the surrounding bone with four screws. (C) The front component is firmly fixed on the back components through a press-fit structure and conforms to the surrounding articular surface.
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F4
After bone cement removal, the bony cortex around the tumour 1-2 mm was excised using a circular 3D-printed guided plate (Figure 4A). The back components were inserted into the cavity and fixed to the surrounding bone with four screws (Figure 4B). The front modular component was firmly fixed on the back components through a press-fit structure (Figure 4C).
Knee flexion is (A) 88  and (B) 130  2 months and 27 months after surgery, respectively.
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F5
The surgery took 325 min, the intraoperative blood loss was 400 ml, and postoperative X-ray images showed that the implant was in a good position (Figures 5A,B). Knee flexion was 130 , which was better than the initial 88  after surgery for 2 months (Figure 5), and knee extension was normal after surgery.
(A) Anterior-posterior and (B) lateral X-ray images after surgery. (C) Anterior-posterior and (D) lateral X-ray images 22 months after surgery: the prosthesis and screws are stable, and callus formation is found at the prosthesis-bone interface (red arrow).
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F6
The X-ray images showed that the prosthesis and screws were stable, and no recurrence was observed in the affected knee 22 months after surgery (Figure 6).