Risk of shortening in operatively treated proximal femur fractures with cephalomedullary nails with dynamically versus statistically locked helical blades.

INTRODUCTION: Cephalomedullary nails (CMN) have proven to be effective for the fixation of unstable pertrochanteric hip fractures, but limited data exists regarding the degree of shortening that occurs with nailing systems that offer "dynamically" versus "statistically" locked helical blades. This study aimed to determine the incidence, timing, and amount of postoperative fracture shortening in patients with pertrochanteric hip fractures treated with "dynamically" versus "statistically" locked helical blades. METHODS: A retrospective review was performed on patients requiring operative fixation of pertrochanteric fractures. Inclusion criteria were patients aged 55 or older, low energy mechanism of injury, primary surgical open reduction and internal fixation of the injury, surgery performed by a fellowship-trained orthopaedic traumatologist, and radiographic follow up until healing or failure (minimum of 3 months). Quantification of fracture shortening was determined using the lateral screw protuberance method. Fracture shortening measurements were calculated from immediate post-operative films and subsequent radiographs at each follow-up visit. RESULTS: 222 patients met inclusion criteria (123 using Depuy Synthes Trochanteric Fixation Nail proximal femoral nailing system (TFN) with static locking; 65 TFN with dynamic locking; 23 using Depuy Synthes Trochanteric Fixation Nail-Advanced proximal nailing system (TFNA) with static locking; and 11 TFNA with dynamic locking). When comparing the final screw protuberance, the TFN dynamic (10.31 mm), TFNA static (9.52 mm), and TFNA dynamic (7.02 mm) groups were found to be significantly less compared to the TFN static cohort (11.67 mm; p < 0.001). The distribution of fracture shortening was found to be significant (p < 0.01). Interval measurements of fracture shortening by repeated measures of ANOVA within groups showed statistically significant increases in screw protuberance for the TFN static (p < 0.001), TFN dynamic (p < 0.001), and TFNA static (p < 0.01) cohorts within the first 60 days postoperatively. The TFNA with dynamic locking group was found to have statistically significant increases until the first 100 days post-operatively (p < 0.02). DISCUSSION: The incidence of fracture shortening remains high even with the use of cephalomedullary nails, regardless of dynamization status. Current pertrochanteric fixation constructs continue to favor fracture healing at the direct expense of fracture shortening.