The migration of helical blade and the tip apex distance value in cephalomedullary nail for geriatric intertrochanteric fractures

Abstract

To investigate the association between the tip apex distance (TAD) and migration of helical blade in the femoral head of geriatric intertrochanteric fractures. A retrospective study of intertrochanteric fractures treated with the proximal femoral nail antirotation (PFNA) between June 2015 and June 2018 was performed. There were 32 males and 55 females with an average age of 84.7 years (range, 80-101 years). All of them were unilateral fresh closed intertrochanteric fractures caused by low energy injury. According to AO/Orthopaedic Trauma Association (AO/OTA) classification, 33 cases belonged to type 31-A1, 35 cases to type 31-A2, and 19 cases to type 31-A3. The time interval from injury to operation was 1-16 days (mean, 3.7 days). The TAD was measured according to immediate postoperative X-ray films. The cases were divided into two groups: group A with TAD less than 20 mm and group B with TAD greater than 20 mm. The difference of fracture healing and migration of helical blade between the two groups were observed. According to the TAD value immediately after operation, 49 patients in group A had TAD of 8.9-19.7 mm, with an average of 18.6 mm; 38 patients in group B had TAD of 20.1-41.4 mm, with an average of 27.7 mm. The 87 patients were followed up for an average of 11.7 months, ranging from 4 to 28 months. Three cases (all in group B) underwent screw blade cutting and displacement, which resulted in internal fixation failure, including 1 case with femoral head cut upward and 2 cases with femoral head penetrated inward. The remaining 84 cases had bone healing without internal fixation related complications such as fracture of internal fixator and fracture of femoral shaft. There was significant difference in the incidence of internal fixation failure between group A and group B ( P=0.049). Reducing the TAD value of helical blade appropriately (15-20 mm) in PFNA internal fixation for intertrochanteric fracture patients over 80 years old can increase initial stability without increasing the risk of helical blade migration.