A biomechanical comparison of proximal femoral nails and locking proximal anatomic femoral plates in femoral fracture fixation: A study on synthetic bones

Abstract

Background: The incidence of fractures in the trochanteric area has risen with the increasing numbers of elderly people with osteoporosis. Although dynamic hip screw fixation is the gold standard for the treatment of stable intertrochanteric femur fractures, treatment of unstable intertrochanteric femur fractures still remains controversial. Intramedullary devices such as Gamma nail or proximal femoral nail and proximal anatomic femur plates are in use for the treatment of intertrochanteric femur fractures. There are still many investigations to find the optimal implant to treat these fractures with minimum complications. For this reason, we aimed to perform a biomechanical comparison of the proximal femoral nail and the locking proximal anatomic femoral plate in the treatment of unstable intertrochanteric fractures.

Materials and methods: Twenty synthetic, third generation human femur models, obtained for this purpose, were divided into two groups of 10 bones each. Femurs were provided as a standard representation of AO/Orthopedic Trauma Associationtype 31-A2 unstable fractures. Two types of implantations were inserted: the proximal femoral intramedullary nail in the first group and the locking anatomic femoral plate in the second group. Axial load was applied to the fracture models through the femoral head using a material testing machine, and the biomechanical properties of the implant types were compared.

Result: Nail and plate models were locked distally at the same level. Axial steady load with a 5 mm/m velocity was applied through the mechanical axis of femur bone models. Axial loading in the proximal femoral intramedullary nail group was 1.78-fold greater compared to the plate group. All bones that had the plate applied were fractured in the portion containing the distal locking screw.

Conclusion: The proximal femoral intramedullary nail provides more stability and allows for earlier weight bearing than the locking plate when used for the treatment of unstable intertrochanteric fractures of the femur. Clinicians should be cautious for early weight bearing with locking plate for unstable intertrochanteric femur fractures.

Keywords: Biomechanical comparison; Femur; femoral neck fractures; fracture fixation; intertrochanteric femur fractures; intramedullary; intramedullary nail; proximal anatomic femoral plate.

Figure 1

X-ray images of bone-implant construct models: (a and b) anteroposterior and lateral views of the intramedullary nail applied on fractured femur model. (c and d) Anteroposterior and lateral view of the plate applied on fractured femur model

Figure 2

Pictures of bone-implant construct models: (a and b) Anteroposterior and lateral view of the plate applied on fractured femur model. (c and d) Anteroposterior and lateral view of the intramedullary nail applied fractured femur model

Figure 3

Positioning of bone-implant construct and biomechanical loading test with Shimadzu Autograph AGS testing device

Figure 4

Fracture patterns for two groups after loading test. (a) Fracture occurred just below the plate in plate applied bone model. (b) Fracture occurred at the tip of the nail in the intramedullary nail applied bone model. (c) Displaced butterfly fragment occurred distally in the intramedullary nail applied bone model

Figure 5

Force-time curves for the bone models numbered 2-5-7 with plates applied

Figure 6

Force-time curves for the proximal femoral nail bone models numbered 3-4-5-6