Intramedullary bone pedestal formation contributing to femoral shaft fracture nonunion: A case report and review of the literature

Abstract

Background: Femoral shaft fracture is a commonly encountered orthopedic injury that can be treated operatively with a low overall delayed/nonunion rate. In the case of delayed union after antegrade or retrograde intramedullary nail fixation, fracture dynamization is often attempted first. Nonunion after dynamization has been shown to occur due to infection and other aseptic etiologies. We present a unique case of diaphyseal femoral shaft fracture nonunion after dynamization due to intramedullary cortical bone pedestal formation at the distal tip of the nail.

Case summary: A 37-year-old male experienced a high-energy trauma to his left thigh after coming down hard during a motocross jump. Evaluation was consistent with an isolated, closed, left mid-shaft femur fracture. He was initially managed with reamed antegrade intramedullary nail fixation but had continued thigh pain. Radiographs at four months demonstrated no evidence of fracture union and failure of the distal locking screw, and dynamization by distal locking screw removal was performed. The patient continued to have pain eight months after the initial procedure and 4 mo after dynamization with serial radiographs continuing to demonstrate no evidence of fracture healing. The decision was made to proceed with exchange nailing for aseptic fracture nonunion. During the exchange procedure, an obstruction was encountered at the distal tip of the failed nail and was confirmed on magnified fluoroscopy to be a pedestal of cortical bone in the canal. The obstruction required further distal reaming. A longer and larger diameter exchange nail was placed without difficulty and without a distal locking screw to allow for dynamization at the fracture site. Post-operative radiographs showed proper fracture and hardware alignment. There was subsequently radiographic evidence of callus formation at one year with subsequent fracture consolidation and resolution of thigh pain at eighteen months.

Conclusion: The risk of fracture nonunion caused by intramedullary bone pedestal formation can be mitigated with the use of maximum length and diameter nails and close follow up.

Keywords: Antegrade intramedullary nail; Case report; Diaphysis; Femoral shaft fracture; Fracture fixation; Nonunion.

Figure 1

Post-operative radiographs of the left femur from outside hospital. A: Anterior-posterior radiograph showing transverse mid-shaft femur fracture with some comminution and Russell-Taylor Delta II 9 x 380 mm antegrade nail with single distal interlocking screw; B: Lateral radiograph showing the same.

Figure 2

Radiographs of the left femur from outside hospital obtained 4 mo post-operatively. A: Anterior-posterior radiograph showing broken distal interlocking screw and poor fracture healing; B: Lateral radiograph showing the same.

Figure 3

Radiographs of the left femur obtained 8 mo post-operatively. A: Anterior-posterior radiograph showing continued poor evidence of fracture healing despite prior distal interlocking screw removal; B: Lateral radiograph showing the same.

Figure 4

Illustration and radiograph of left femur obtained intra-operatively. A: Illustration of bone pedestal at tip of intramedullary nail blocking guide rod passage; B: Radiograph showing guide rod tip (inside intramedullary nail) unable to pass intramedullary bone pedestal (outlined).

Figure 5

Illustration of left femur intra-operatively. A: Showing femur after intramedullary nail removal. Guide rod tip still unable to pass distally in canal due to intramedullary bone pedestal; B: Showing starting reamer used to breach intramedullary bone pedestal; C: Showing new nail (solid lines) at area of wider, more distal meta-diaphyseal bone compared to old nail (dotted lines) at area of more proximal, narrow diaphyseal bone.

Figure 6

Illustration and fluoroscopic radiographs of left femur obtained intra-operatively. A: Illustration showing intramedullary nail placed past bone pedestal; B: Anterior-posterior radiograph showing new, larger diameter intramedullary nail placed past bone pedestal; C: Lateral radiograph showing the same.

Figure 7

Fluoroscopic radiographs of left femur obtained intra-operatively. A: Anterior-posterior radiograph one year post-operatively showing early callous formation but incomplete fracture healing; B: Lateral radiograph showing the same but at increased magnification.

Figure 8

Radiographs of the left femur obtained 18 mo post-operatively. A: Anterior-posterior radiograph showing evidence of good fracture healing; B: Lateral radiograph showing the same.