Introduction

The proximal femoral nail antirotation (PFNA) was introduced by the Arbeitsgemeinschaft fur Osteosynthesefragen (AO)/Association for the Study of Internal Fixation group in 2004^1,2 and the PFNA-II (Asian version) was introduced in 2008.³ Since the introduction of PFNA and PFNA-II, the cephalomedullary nail with a single head-neck helical blade has commonly been used to treat osteoporotic geriatric patients with unstable pertrochanteric and/or intertrochanteric fractures. Good results and functional outcomes have been reported globally by many authors.^4,5,6,7,8 However, complications, such as lateral cortex impingement, medial head perforation or “cut-through” of the helical blade, abutment of the distal nail tip to the anterior femur cortex, and over prominence of the proximal nail end outside of the greater trochanter, have also been reported.^9,10,11

The treatment of unstable proximal femoral fractures,⁴ can be either by side-plate screw system represented by dynamic hip screw (DHS) or the intramedullary nail system. Cephalomedullary nails, including Gamma nail, InterTan, proximal femoral nail (PFN) and PFNA, are now favoured in the treatment of unstable proximal femur fractures for their unique characteristics in insertion mode and morphological design. The PFNA is also preferred for its distinctive features like one single helical blade perforated into the femoral head, wrench-in, large axial contact area and squeeze cancellous bone, while PFNA II was modified to avoid lateral cortex impingement during the insertion of nail.

The PFNA-II design has three modifications to the PFNA to accommodate Asian anatomic characteristics: (1) The proximal nail diameter was reduced from 17 mm to 16.5 mm, (2) the mediolateral angle was reduced from 6° to 5°, and (3) a flat proximal lateral surface was adapted to avoid impingement of the femoral lateral cortex. The PFNA-II is available in four lengths (170 mm, 200 mm, 240 mm, and long). There are four distal diameters available (9 mm, 10 mm, 11 mm, and 12 mm), all measuring 105 mm in proximal segment length. The long types of PFNA-II are designed with an anterior curvature (radius, 1500 mm) to meet the bow of the femur.

During our clinical use of PFNA II, we found that the proximal nail frequently protruded over the greater trochanter area [Figure 1]. The purpose of this study was to clarify whether the proximal segment length (105 mm) is suitable for the height of the greater trochanter in the Asian population.