Review Question - QID 219819

The patient has an atrophic nonunion as evidenced by the lack of callous formation and broken hardware (Answer 4).

Fracture healing involves a complex and sequential set of events that relies on adequate stability and biology to accomplish union. Many factors can hamper this process and lead to the arrest of the repair process. Nonunion is typically classified into septic, hypertrophic, atrophic, or oligotrophic depending on the underlying process. Septic nonunion is caused by infection and is most reliably diagnosed with elevated serum CRP. In hypertrophic nonunion there is adequate blood supply and biology, but insufficient stability leads to callous formation without union. Conversely, atrophic nonunion has minimal callous formation and is typically secondary to limited blood supply and inadequate immobilization. Lastly, oligotrophic nonunion involves inadequate fracture reduction in the setting of fracture displacement.

Naclerio et al. reviewed humeral shaft nonunions with an emphasis on presentation after both conservative and surgical management. They recommend a thorough preoperative evaluation to identify infectious or metabolic causes. Surgery typically involves compression plating with or without bone graft but specialized techniques such as cortical struts or vascularized fibular grafts are occasionally indicated. The authors conclude that successful treatment of humeral shaft nonunion improves function, reduces disability, and improves the quality of life for patients.

Wiss et al. report their series of 152 femoral nonunions treated with either a plate or intramedullary nail at a single institution. In their series, 84% of patients eventually achieved union, but only two-thirds did so after the initial revision surgery, and nearly 20% required additional surgery to reach union. Risk factors for failure included deep infection, active smokers, metabolic bone disease, and patients who had undergone 3 or more prior surgeries.

Figure A: Displaced midshaft humerus Fracture. Figure B: Minimal callous formation at 6-week follow-up. Figure C: Several months after ORIF the patient continues to have limited callous formation on repeat radiographs with evidence of broken hardware.

Incorrect answers:
Answer 1: This patient's CRP is not elevated making septic nonunion unlikely
Answer 2: Pseudarthrosis is characterized by the inability to form a normal bony callus with subsequent fibrous nonunion, leading to pseudarthrosis (or "false joint").
Answer 3: There is limited callous formation seen on the radiographs
Answer 5: Oligotrophic nonunion has limited callous in the setting of incomplete reduction.