Abstract
BackgroundIt is common practice when placing cannulated screws within the femoral head when treating femoral neck fractures to avoid the thread-forms from crossing the fracture line. Despite the widespread use of cannulated screws in internal fixation of femoral neck fractures, there is no study to our knowledge that describes the ideal length of thread-forms. PurposeThe purpose of this study is to determine the thread length that will maximize purchase within the femoral head while minimizing risk of crossing the fracture line. Additional analysis was conducted to identify factors associated with the maximal possible length of treads in minimally and non-displaced femoral neck fractures. MethodsWe performed a retrospective study of all patients treated for a minimally or non-displaced femoral neck fracture from April 1, 2004 through December 31, 2017. Only patients who had received a pre-operative CT or MRI scan were included. Fixation was then templated using radiographs and the distance from the subchondral bone to the fracture line was then measured. ResultsThe study included 127 patients. The average estimated length of lag screw threads was 33.2 ± 6.67 mm, with lower quartile of 29.1 mm and higher quartile of 37.2 mm. The median was 32.0 mm and most frequently encountered estimate was 29 mm. Estimated lag screw size did not differ significantly based on age or BMI, but both height (p < 0.001) and race (0.04) were positively correlated with estimated lag screw size and males had longer measurements compared to females, 37.2 ± 7.0 mm vs 31.4 ± 5.7 mm (p < 0.001), respectively. ConclusionIn conclusion, we propose an additional lag screw thread form with length 26.0 mm to capture 90% of femoral neck fractures.
Highlights
In 2008 there were almost 341,000 emergency department visits in the United States for hip fractures 1
PATIENTS AND METHODS 2.1 Study Design We performed a retrospective study of all patients treated at two ACS level 1 trauma centers between April 1, 2004 and December 31, 2017. 2.2 Study Participants Cases were identified retrospectively by querying the hospital database for patients with femoral neck fracture who received pre-operative computerized tomography (CT) or magnetic resonance imaging (MRI)
Presently, most lag screws are manufactured with two standard thread form lengths, 16mm and 32mm 12 (Table 1)
Summary
The majority of hip fractures are femoral neck fractures that occur in elderly patients as a result of low-energy trauma 3. Cannulated screws are the most commonly used implant for internal fixation of femoral neck fractures 4, especially in those under 60 or have good bone health 5, given the quick recovery, short operative time, and low blood loss 6,7. To optimize purchase within the bone and improve compression across the fracture plane it is important to maximize the amount of screw threads within the femoral head fragment 8,9. To achieve optimal compression between the fracture fragments, it is important for all the tread-forms to be across the fracture site 10. There is no study to our knowledge that describes the ideal length of thread-forms for cannulated screws in the fixation of femoral neck fractures
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