Mechanical Complications Of Intertrochanteric Hip Fractures Treated With The Trochanteric Fixation Nails

Background:Optimal fixation of intertrochanteric hip fracture remains unknown. Cutout has been a persistent problem. The trochanteric fixation nail (TFN) was designed with a helical blade to improve resistance to cutout.The purpose of this study was to identify the mode of mechanical failure of intertrochanteric hip fractures treated with TFN, and to identify predictors of failure.Methods:341patients with intertrochanteric hip fractures were treated with the TFN. Patient demographic information, fracture type (AO/OTA classification) and radiographic data were collected. Quality of reduction and fixation was evaluated using Baumgaertner’s tip-apex distance (TAD) and Parker’s method.Results:223patients fit radiographic and follow-up criteria and were available for evaluation of mechanical complications and predictive factors. Sixty-seven patients were male and156were female. The average age was77.2years (range,50-99years). Average follow up was24.6months (range,4-74months). The overall rate of mechanical complications was20.5%. Twenty-one patients (9.4%) had excessive lateral migration of the helical blade (≥10mm). Fifteen patients (6.7%) had blade migration in the head, included7patients(3.1%) withtypical cut out with the fracture dropping into, and8patients (3.6%) with medial perforaton without loss of reduction. Three patients (1.3%) sustained a femoral shaft fracture at tip of nail. The quality of calcar reduction was significantly predictive of all modes of failure (p<0.05), except femoral shaft fracture at the nail tip. Excessive lateral migration was also associated with unstable fracture patterns (p=0.01). On the AP radiograph the average position of blade as determined by the Parker’s method was at51for patients who did blade migration in the head and44for those who did not (p<0.05, t-test). On the lateral radiograph the average position of blade was at49and50, respectively. The statistical significance of the difference by the t-test was p>0.05. There was a significantly higher (p<0.05) rate of blade migration in the head when the TAD was less thanl5mm. Of the46patients developed a mechanical complication, only11required revision operations, the remaining patients went on to uneventful union, at an average time of4.5months (range3-11months).Conclusions:The most common mechanical complicationof intertrochanteric hip fracture treated with the TFN was excessive lateral migration of the helical blade within the nail; however this rarely led to a clinical problem. We have identified a new complication associated with the TFN, medial perforation without loss of reduction. This was the second most common mode of failure in our series. Blade migration in the head was less frequent when blades were placed inferiorly compared to those placed centrally or superiorly on the AP plane. The central placement of blade on lateral view did not appear to be critical. It appears important to achieve a TAD of at least15mm. The fractures should be reduced as accurately as possible, with specific attention to the reduction of the calcar, to minimize the rate of mechanical failure.