Patient-specific osteotomy guides and robot-assisted fixation for femoral shortening with varus deformity: a case series with technical notes

Femoral shortening with varus deformity can be difficult to treat, especially when correction of the deformity and restoration of limb length are required in the same procedure. Conventional techniques still depend partly on intraoperative judgement, which may affect osteotomy accuracy, alignment correction, and fixation. This study describes our use of patient-specific osteotomy guides together with robot-assisted fixation in patients with femoral shortening and varus deformity and reports the preliminary clinical outcomes. We retrospectively reviewed four consecutive patients with femoral shortening and varus deformity treated between January 2021 and December 2023. Preoperative three-dimensional (3D) reconstruction and virtual planning were performed from computed tomography (CT) data to determine the osteotomy plane and correction parameters. Patient-specific 3D-printed guides were then produced and used during distal femoral lateral closing-wedge osteotomy. Robot-assisted Schanz screw insertion was used for external fixation and subsequent distraction osteogenesis. Limb-length restoration, external fixation index, lower-extremity alignment, knee range of motion, and complications were reviewed. The procedure was completed in all four patients. One mild pin-site reaction resolved with local care and oral antibiotics; no deep infection, neurovascular injury, delayed union, nonunion, refracture, or unplanned reoperation occurred. Varus correction was satisfactory, and regenerate bone formation was observed during distraction. The mean lengthening was 6.25 cm, the mean external fixation time was 20 months, and the mean external fixation index was 3.2 months/cm. The mechanical lateral distal femoral angle (mLDFA) improved from 111.27° to 93.79°, and the mechanical femorotibial angle (mFTA) decreased from 199.24° to 182.94° at the final follow-up. Limb-length discrepancy was largely corrected, and knee range of motion was maintained. The combined use of 3D planning, a patient-specific osteotomy guide, and robot-assisted Schanz screw insertion appeared feasible in this small series of patients with femoral shortening and varus deformity. In our experience, this workflow allowed the osteotomy plane, correction angle, and screw trajectory to be planned before surgery and reproduced intraoperatively with the printed guide and robotic navigation. These findings should be interpreted as preliminary, and larger studies are needed to confirm their reproducibility.