3D-printed prothesis combined hinged knee arthroplasty in the treatment of critical-sized osteomyelitis-derived bone defects around the knee joint

Treating peri-knee bone defects caused by osteomyelitis remains a clinical challenge, particularly in accurately repairing critical-sized defects while preserving joint mobility. This study aimed to evaluate the outcomes of an innovative technique combining 3D-printed prostheses with hinged knees to reconstruct bone defects from peri-knee osteomyelitis. We built models of critical-sized bone defects in the distal femur and proximal tibia and used finite element analysis (FEA) to describe the stress characteristics of different components. Additionally, we retrospectively enrolled ten patients, with a mean age of 45.6 years. The defects were located in the distal femur (four cases) and proximal tibia (six cases), with a mean defect volume of 123.4 cm³. Prosthesis stability was assessed through continuous X-rays, and new bone regeneration was synthetically evaluated using X-rays and histological staining. Lower Extremity Functional Scale (LEFS) was used to quantitatively assess limb function. FEA indicated that stress was distributed centrally throughout the models. Components bearing higher stress included intramedullary nails, the lateral flanks of 3D-printed prosthesis, and the grooves of tibial inserts. Among the ten enrolled patients, two experienced osteomyelitis recurrence and underwent transfemoral amputation. The mean follow-up period for the remaining eight patients was 25.9 months. Postoperative X-rays showed that the prostheses remained stable, with new bone gradually growing along the prosthesis surface. Histological staining further confirmed that new bone had grown inside the superficial rough pores of nail. At the last follow-up, these eight patients were able to walk autonomously, with LEFS scores significantly improving compared to pre-surgery (20.1 vs. 8.9, P < 0.001). In terms of surgery-related complications, aside from the mentioned osteomyelitis recurrence, one patient experienced screw breakage and required revision surgery. The combined application of 3D-printed prostheses and hinged knees is an effective technique to reconstruct peri-knee critical-sized bone defects. It can simultaneously repair bone defects and preserve knee joint mobility.