Safety and Effectiveness of Proximal Femoral Nail Antirotation for the Treatment of Intertrochanteric Femoral Fracture: Study Protocol for a Prospective Case Series

History and current status of related studies Intertrochanteric femoral fracture frequently occurs in the elderly that is often complicated by different levels of osteoporosis, and mostly belongs to unstable fractures. This disorder is also frequently complicated by various chronic diseases, which make patients have poorer surgical tolerance. Surgical treatment is the widely accepted treatment method of intertrochanteric femoral fracture because it can accelerate the recovery and reduce the complications caused by long-term bed time. Intertrochanteric femoral fracture is unstable and occurs mostly in the elderly, so surgical treatment should meet the requirements including less risk of wound infection, less intraoperative blood loss, great holding potential and strong stability of the implants, which contribute to early hip joint function exercise and facilitate recovery after surgery.

According to the design principle of orthopedic implants, intramedullary and extramedullary fixations are commonly used. Compared to extramedullary fixation, intramedullary fixation places fixators closer to the affected region, produces shorter moment arm of force, better shares the compression forces on the medial cortex of the femoral neck, exhibits higher shear resistance, and provides greater stabilization for complex fractures in the elderly.

Compared to Garmma nail, an AO (Association for Osteosynthesis) proximal femoral nail has an antirotation screw in the proximal end which ensures an elastic fixation of the fracture and reduces the complications such as femoral shaft fractures. Nevertheless, 2 screws should be installed in the femoral neck, which restricts the slippage between the main screw and the compression screw, thus partial loading will be delivered through antirotation screws, leading to occurrence of complications such as antirotation screw cutting and compression screw withdrawal.

Conventional internal fixation methods including implantations of dynamic hip screws, Gamma nails, and proximal femoral intramedullary nail exhibit unfavorable effects in the treatment of intertrochanteric femoral fracture, in particular those complicated by severe osteoporosis because these methods cannot achieve firm and reliable fixation with occasional nail head cutting and nail withdrawal. Therefore, AO/ASIF (Association for Osteosynthesis/Association for the Study of Internal Fixation) designed a novel antirotation intramedullary nail, which better reduces the abovementioned complications.

Proximal femoral nail antirotation (PFNA) is a device designed based on proximal femoral intramedullary nail and other intramedullary nails. This device is equipped with a spiral wide blade which exhibits obvious antirotation and angular shear stress abilities, greatly reducing complications and decreasing the possibility of surgical delay. Compared to conventional screw systems, PFNA provides stronger antirotation and anti-inversion abilities. For tapping of a spiral blade in the femoral neck, only lateral femoral cortex should be opened without a need to remove bone matrix. The spiral blade tapped in the femoral neck will produce compression to the bone in the femoral neck. Even though for patients with severe osteoporosis, the spiral blade in the femoral neck can produce firm anchoring force with the femoral neck. Compared with screw fixation, a spiral blade exhibits a larger rotational torque, requires a smaller strength to be pulled out, and does not need additional screws tapped in the femoral neck, so the latter is easier to be operated. The PFNA has a medial-lateral angle of 6°, this allows insertion at the tip of the greater trochanter. The distal diameter of the PFNA is relatively small, and its eccentricity is reduced compared to that of intramedullary nails, which is more suitable to the anatomical morphology of proximal femoral medullary cavity. The locking pores of the PFNA at its distal tip include round static and oval-shaped dynamic types. Vertical installation of screws is considered dynamic interlocking and oblique installation of screws static interlocking. From the perspective of design, PFNA exhibits better biomechanical stability and shows advantages in duration of surgery, intraoperative blood loss, failure rate of surgery and overall complications over than internal fixation methods.