Presence of a Nail in the Medullary Canal; Is It Enough to Prevent Femoral Neck Shortening in Trochanteric Fracture?

PURPOSE Presence of a cephalomedullary nail (CMN) in the medullary canal has been thought as advantageous in the control of femoral neck shortening (FNS) and lag screw sliding in trochanteric fracture compared to extramedullary fixation system. However, researches on the factors that influence the degree of FNS after cephalomedullary nailing are lacking. MATERIALS AND METHODS We observed 95 patients (mean age, 75±2.8 years) with trochanteric fractures who were treated with a CMN, and evaluated the relationship between FNS and patient factors including age, gender, fracture type (AO/OTA), bone mineral density, medullary canal diameter, canal occupancy ratio (COR=nail size/canal diameter), and tip-apex distance using initial, immediate postoperative, and follow-up radiography. RESULTS Univariate regression analyses revealed that the degree of FNS was significantly correlated with fracture type (A1 versus A3, p<0.001), medullary canal diameter (p<0.001), and COR (p<0.001). Multiple regression analyses revealed that FNS was strongly correlated with fracture type (p<0.001) and COR (p<0.001). CONCLUSION Presence of a CMN in the medullary canal could not effectively prevent FNS in patients with low COR and in A3 type fracture.