RESUMEN
Objective To observe the matching between the straight short femoral cephalomedullary nail (PFNA-Ⅱ) and the femoral anterior bow in Chinese patients with intertrochanteric fracture. Methods A retrospective study was performed to analyze the postoperative lateral X-rays of 158 patients with intertrochanteric fracture who had been treated by PFNA- Ⅱ between August 2009 and December 2010.They were 35 men and 123 women,with a mean age of 77.2 years.The relationships between the distal tip of the medullary nail and the anterior cortex of the femur were observed according to a self-designed 6-grade scale (grade 0:central location of the nail tip in the medullary canal; grade 1:deviated location without contact with the cortex; grade 2:contact＜ 1/3 cortex thickness; grade 3:contact ＞ 1/3, ＜ 2/3 cortex thickness; grade 4:contact ＞ 2/3 cortex thickness; grade 5:perforation; posterior deviations in grades 1 to 5 presented as minus).The theoretical distance was measured as if the anterior protrusive nail tip had been placed back to the central axis.The degree of the curvature and its corresponding radius were calculated by the geometric method. Results Of the 158 patients,the distal tip of PFNA- Ⅱ was located centrally along the axis of femur canal in 30 cases(19.0％ ),posteriorly to the central axis in 10 cases(6.3％ ),and anteriorly to the central axis in 118 cases (grades 1 to 3; 74.7％ ),of which 55 cases experienced irritation caused by the contact between the distal tip and the anterior cortex (grades 2 to 3％ ).The mean theoretical distance needed to put back the nail tip to the canal central axis was 1.42 ± 0.18 mm in the 17 cm nails,1.77 ± 0.39 mm in the 20 cm nails,and 2.46 ±0.20 mm in the 24 cm nails.Their corresponding curvature arcs were 2.51° ±2.40°,2.13° ± 1.65° and 2.09° ± 0.98°,and their curvature radii were 1483 ± 818 mm,2329 ± 1293 mm,and3710 ± 1957 mm,respectively. Conclusions There is a significant mismatch between the current short straight celphalomedullary nail (PFNA- Ⅱ) and the femoral anterior how in Chinese population.A curvature design is needed for the short cephaiomedullary nails to match the femoral anterior how of Chinese population.