Failure of PFNA: helical blade perforation and tip-apex distance.

Since the clinical introduction of proximal femoral nail antirotation (PFNA) by AO group in 2004 and PFNA-II (Asian version) in 2008, this type of cephalomedullary nail with single head-neck helical blade were commonly used in unstable pertrochanteric and intertrochanteric fractures in geriatric patients. Recently, severe complications of helical blade perforation through the femoral head, into the hip joint or even the pelvis, were reported in several case reports. After review of the PFNA literature in English, we found a total of 12 cases helical blade protrusion in 6 papers (Table 1). From the provided data and radiographs, we can summarise that most patients were old women, the fracture reduction and caput-collum-diaphyseal angle were acceptable, and most patients took full weight bearing immediately after operation. Four perforations occurred after a fall on the affected hip, one with subclinical low-grade infection, one with helical blade tail abutting the lateral cortex, and six had none aetiology. Most perforations occurred within 6 weeks. Furthermore, blade tip-apex distance (TAD) in four available patients was less than 20 mm or even 15 mm. Contrast to femoral head lag screws (blunt head, wrench-in, large axial contact area and move cancellous bone), the helical blade has its own unique characteristics in insertion mode and morphological design (relative sharp head, hammer-in, large circumference contact area and compact cancellous bone). These