Outcomes of Open Reduction and Internal Fixation in Intra-articular Distal Femur Fractures with Incarcerated Patella: A Case Series of a Rare Injury Pattern.

Introduction: Distal femur fractures associated with patellar incarceration are rare, complex injuries that pose significant diagnostic and surgical challenges. The patella, an essential component of the knee extensor mechanism, may become entrapped within distal femoral fracture fragments following high-energy trauma, creating a mechanical block to reduction. Failure to recognize this uncommon injury pattern can result in repeated unsuccessful attempts at closed reduction, leading to chondral injury, knee stiffness, and suboptimal functional outcomes. Early diagnosis using computed tomography (CT) imaging and prompt open reduction are crucial to restore articular congruity and extensor mechanism integrity. Due to the rarity of this condition, existing literature is limited primarily to isolated case reports. This study evaluates the functional and radiological outcomes of open reduction and internal fixation in patients with distal femur fractures associated with patellar incarceration. Materials and Methods: This case series was conducted at a tertiary health-care center between February 2024 and January 2026 after institutional ethical approval. Five patients aged 12-35 years with intra-articular distal femur fractures (AO types 33B and 33C) associated with incarcerated patella were included. One patient had a Salter-Harris Type IV physeal injury. Patients with additional ipsilateral limb fractures, prior knee surgery, or severe open fractures (Gustilo-Anderson IIIB/C) were excluded. Pre-operative assessment included radiographs and CT with three-dimensional reconstruction to confirm patellar incarceration and fracture configuration. All patients underwent open reduction, retrieval of the incarcerated patella, anatomical fracture reduction, retinacular repair, and fixation using cannulated cancellous screws and distal femur locking compression plates. A physeal-sparing technique was employed in the skeletally immature patient. Functional outcomes were assessed using the International Knee Documentation Committee (IKDC) score at 1-year follow-up. Results: We included five patients (four males and one female) with a mean age of 22.2 years (standard deviation 8.9). Four patients had AO type 33C fractures, and one had type 33B. Retinacular injury was present in all cases. The mean time to union was 10 weeks (range 8-12 weeks). At 1-year follow-up, the mean knee flexion was 118°, and the mean IKDC score was 88, indicating good to excellent functional outcomes. One patient developed post-operative stiffness requiring mobilization under anesthesia. No cases of implant failure, non-union, infection, patellar maltracking, or extensor mechanism dysfunction were observed. Conclusion: Distal femur fractures with patellar incarceration are rare and often irreducible by closed methods. Early CT-based diagnosis followed by prompt open reduction, meticulous retinacular repair, and stable internal fixation results in reliable fracture union and favorable functional outcomes. Timely recognition and intervention are essential to prevent complications and optimize recovery.