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case_images: (a) Radiograph after trauma showing a Delbet Type III femoral neck fracture; (b) radiograph after open reduction and internal fixation surgery; (c) radiograph at one-month follow-up showing signs of mild SCFE (white arrow); (d) radiograph at three-month follow-up showing worsening SCFE (white arrow).
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case_images: Type III basicervical femoral neck fracture (Figure 1a). The patient's medical history revealed no previous fractures, surgeries, or chronic medication use. Treatment involved closed reduction and internal fixation using a Dynamic Hip Screw (DHS) plate and an additional free cannulated screw (Figure 1b). The reduction was deemed satisfactory, and at a one-month follow-up, progressive fracture healing was noted (Figure 1c). However, three months later, radiographs revealed worsening slippage (Figure 1d).
case_images: (a) Overlap of the healthy contralateral femur (shown in green with an orange outline); (b) Identification of a plane tangent to the base of the slipped epiphysis and of the position of the screw for ISF (outlined in orange).
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case_images: A mirrored model of the healthy contralateral hip was used to facilitate the analysis of the deformity (Figure 2a). This process determined the precise entry point, direction, and length of the screw, which was 65 mm (Figure 2b).
case_images: (a) The first step was to determine the final position of the proximal femur after an intertrochanteric closing wedge and derotative osteotomy in order to improve the range of motion of the hip; (b) final positioning of the 90  blade plate; (c) the plate (highlighted in orange) was positioned in order to avoid the holes of the previous hardware (in dark gray) as much as possible; (d) restoring the femur to its deformed state maintaining the plate in its position relative to the proximal femur reveals the initial position of the blade and the shape of the bone wedge that needs to be removed (in red).
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case_images: This began with a detailed analysis of the deformity, followed by determining the desired angular and rotational corrections to improve hip range of motion (Figure 3a). The osteotomy site and the final plate position were then meticulously defined in order to prevent intersecting the holes left by previous hardware (Figure 3b,c). Subsequently, maintaining the plate in its position relative to the proximal femur, the femur was reverted to its original deformed state (Figure 3d).
case_images: (a) Anterior view of the proximal femur with the initial plate positioning and the bone wedge to remove; (b) positioning of the guidewire for the cannulated screw (the more anterior wire) and two lateral wires for the placement of the blade plate; (c) design of the first 3D-printed PSI (highlighted in light blue).
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case_images: The first PSI was designed to guide the insertion of three guidewires (Figure 4).
case_images: (a) The position of the chisel along the proximal 1.5 mm guidewire and of the distal 1.5 mm guidewire; (b) the second PSI(highlighted in light blue), designed to fit onto the distal guidewire, precisely indicates the directions for chisel insertion and for the distal cut; (c) design of the third PSI (highlighted in light blue), featuring similar characteristics to the second, but specifically guiding the proximal cut; (d) simulated correction in valgus, flexion, and internal rotation of the distal femur.
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case_images: Subsequently, we developed second and third PSIs to facilitate the cutting process and ensure the precise alignment of the blade plate during insertion (Figure 5).
case_images: The final 3D-printed samples of the PSIs. From the left to the right: the first PSI for wire positioning, the second PSI for the distal cut, and the third PSI for the proximal cut.
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case_images: Next, the second guide was designed with the same features, but its saw support was specifically aligned for the more proximal cut (Figure 6).
case_images: (a) Anatomical landmarks and fluoroscopy check; (b) L-incision along the proximal inferior border of the vastus lateralis; (c) removal of the DHS plate and of the proximal anti-rotation screw.
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case_images: The DHS plate was subsequently identified and removed, along with the free screw (Figure 7).
case_images: The intraoperative application of the first PSI. (a) Intraoperative picture of the first PSI in place; (b) intraoperative imaging of guidewire positioning; (c) position of guidewires for the free screw for ISF (highlighted in yellow) and for the blade plate (highlighted in orange) in the VSP for comparison with the intraoperative imaging.
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case_images: At this point, the hip was slightly externally rotated to facilitate the positioning of the first patient-specific template (Figure 8).
case_images: The intraoperative application of the second PSI. (a) The distal 1.5 mm guidewire was leveraged to precisely fit the second PSI; (b) a longitudinal line was marked to monitor rotational alignment.
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case_images: The second PSI was positioned on the femur, leveraging the distal 1.5 mm guidewire as a reference to accurately identify the distal osteotomy site (Figure 9).
case_images: The intraoperative application of the third PSI. (a) Application of the third cutting guide on the previously inserted guidewire; (b) application of the third guide to set the correct angulation of the chisel.
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case_images: The third PSI was then applied to identify the proximal osteotomy and to achieve the correct angulation of the chisel in the sagittal plane, allowing for the placement of the blade plate at 20  of flexion (Figure 10).
case_images: (a) Intraoperative fluoroscopy showing the anterior bump; (b) intraoperative fluoroscopy showing the bump removal after the OChP (fine needle marks the area of the resected bump).
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case_images: A final fluoroscopic check confirmed the satisfactory removal of the intra-articular bump (Figure 11).
case_images: Radiographs at 6 months follow-up. (a) Anteroposterior view; (b) frog-leg view.
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case_images: Radiographs showed good consolidation with no signs of AVN of the femoral head (Figure 12).