Introduction: The precision of coronal plane alignment in distal femoral osteotomy (DFO) surgeries often falls short of expectations due to multi-plane deformities requiring adjustments in all three planes. Current conventional techniques frequently deviate significantly from preoperative templates. Recently, the application of 3D planning and patient-specific instrument (PSI) in DFO surgery has proven to be a reliable and accurate method for correcting complex Valgus knee deformities. The objective of this article is to describe the technique we employed using PSI in DFO surgery for a case involving multiplanar deformity.

Case Presentation: We present the case of a 14-year-old female patient with no personal or family history of illness, presenting with pain and deformity in the right knee. The deformed knee worsened over time. Imaging diagnosis, including X-ray, CT-scans and MRI of the lower extremities, the patient was diagnosed with a valgus deformity of the knee due to traumatic premature closure of the femoral growth plate. The patient underwent derotational osteotomy of the Distal Femur using PSI. No complications after surgery. Postoperatively, mLDFA and FTA were corrected from 78.2 and 155 degrees to 87 and 174.5 degrees, respectively. Femoral anteversion decreased from 25.1 to 15 degrees (deviation of 0.5 degrees with pre- op planning), and the patient's Lysholm score improved from 51 to 96 one year postoperatively.

Clinical Discussion: The use of PSI in correcting complex distal femoral deformities is an effective method that achieves high accuracy and safety for patients. The application of PSI helps shorten surgical time and reduce the frequency of C-arm usage during surgery.

Conclusion: The utilization of PSI in DFO surgery is an effective, safe, and highly accurate method for correcting complex distal femoral deformities.

Keywords: 3D printed, Distal Femoral Osteotomy (DFO), multi-planar deformities, case report