Highlights
- •Current thread-lengths available for femoral neck fractures are not ideal to maximize purchase without crossing the fracture.
- •The most common thread-lengths available for larger size lag screws are 16mm, 32mm, and 40mm.
- •The average optimal length of lag screw threads is 33.2 ± 6.7 mm in femoral neck fracture patients to maximize purchase.
- •Men typically have larger femoral heads and can accommodate larger thread-lengths than women (p < 0.001).
- •Lag screws with 26mm thread lengths could improve the overall fixation without crossing the fracture line in 90% of patients.
Abstract
Background
It 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.
Purpose
The 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.
Methods
We 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.
Results
The 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.
Conclusion
In conclusion, we propose an additional lag screw thread form with length 26.0 mm
to capture 90% of femoral neck fractures.
Keywords
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Article info
Publication history
Published online: January 31, 2019
Accepted:
January 30,
2019
Identification
Copyright
© 2019 Elsevier Ltd. All rights reserved.
