Review Question - QID 220574

This patient has an oligotrophic distal femoral nonunion and fatigue failure of her plate construct, likely due to an overly stiff locking plate construct (Answer 2).

This patient was initially treated with lateral locked plate fixation of a comminuted intra-articular distal femur fracture. However, the initial construct had a short working length and high screw density, leading to a high stiffness and low strain on the fracture site. This led to an oligotrophic nonunion and eventual fatigue failure of the construct at the fracture site after cyclic micromotion at the nonunion site. This outcome could have been prevented with a stronger construct with lower stiffness. This is demonstrated with the revision construct, which has a high construct strength but a long working length, spanning the majority of the femur.

Ricci et al. aimed to identify risk factors for complications in the treatment of distal femur fractures using locked plate fixation. A retrospective review of 335 fractures in 326 patients treated at three trauma centers was conducted. Locked plating was used for open reduction internal fixation, with various configurations of locked and nonlocked screws. Their findings indicated that risk factors for proximal implant failure included open fracture, smoking, increased body mass index, and shorter plate length. The study concluded that while many risk factors are beyond the surgeon's control and useful for prognosis, technical choices such as using longer plates can reduce the risk of fixation failure, due to longer working length.

Giannoudis et al. emphasize the importance of mechanical stability in fracture healing, alongside the previously recognized triangular concept of osteogenic cells, osteoinductive growth factors, and osteoconductive scaffolds. The authors argue that mechanical stability is a crucial fourth element that should be equally acknowledged for optimal bone regeneration. They propose the 'diamond concept' for bone restoration, which integrates the mechanical environment with the biological factors, highlighting that both play a vital role in the complex physiological process of bone healing without scar formation. This concept underscores the necessity of considering the mechanical aspects in conjunction with biological interventions to enhance the efficacy of orthopedic trauma therapies.

Wilson et al. provide a narrative review of fixation options in the treatment of geriatric distal femur fractures, including the biomechanical considerations of two primary fixation options: retrograde intramedullary nailing and plate-and-screw constructs. These modalities are evaluated in the context of providing stability, promoting fracture healing, and accommodating the unique anatomy and bone quality of the geriatric femur. They suggest that a hybrid nail-plate approach might offer superior mechanical stability in certain scenarios.

Figure A is the AP and lateral radiographs of an oligotrophic distal femoral nonunion with catastrophic failure of the lateral locked plate construct. Figure B is the AP radiograph of a healed distal femur fracture treated with a nail-plate combination construct.

Incorrect Answers:
Answer 1: The initial construct went on to fatigue failure, indicating inadequate construct ultimate strength.
Answer 3: The initial construct has a short working length, leading to increased stiffness and oligotrophic nonunion.
Answer 4: The patient went on to union without bone grafting, indicating adequate fracture biology for healing.
Answer 5: The initial construct utilized a thick distal femur anatomic locking plate, which is necessary in the plate fixation of distal femur fractures to allow for adequate construct strength to tolerate the forces imparted on the femur.