Re: Vertically Oriented Femoral Neck Fractures
We read the recently accepted Journal of Orthopaedic Trauma (JOT) paper titled “Vertically oriented femoral neck fractures: a biomechanical comparison of 3 fixation constructs” by Joey P. Johnson, MD; Todd R. Borenstein, MD; Gregory R. Waryasz, MD; Stephen A. Klinge, MD; Philip K. McClure, MD; Alison Biercevicz Chambers, PhD; Roman A. Hayda, MD; and Christopher T. Born, MD and had a few thoughts to share based on an earlier study published titled “The effect of moment arm length on high angled femoral neck fractures (Pauwels' JII)” by Matthew S. Lepine, BS; William R. Barfield, PhD; John Desjardins, PhD; and Langdon A. Hartsock, MD published in the Journal of Biomedical Science and Engineering (JBiSE), Volume 3, 448–453, 2010.
The JBiSE paper from 2010 used 3 moment arm lengths for Pauwels' Type Ill fracture to biomechanically test for failure subcapital, transcervical, and basicervical fracture types in 75 third Generation Composite left femoral sawbones with 5 different fixation types; dynamic hip screws with and without derotational screws, dynamic helical hip screws with and without derotational screws, and 3 cannulated screws in an inverted triangle configuration. Our findings, with 5 specimens/group, based on a priori power analyses were that the only moment arm length that was statistically different between the fixation types was in the basicervical high-angle fracture type in which the 4 hip screw fixation types were statistically superior and better fixation choices compared with 3 cannulated screws.
In the recently accepted JOT paper, the authors used 3 groups with a vertically oriented osteotomy, however, whether subcapital, transcervical or basicervical was not noted. Their fixation configuration was not the same as in the JBiSE paper and they used a fatiguing protocol which we did not use. The cannulated screw load at failure in the JOT study was between 3756 and 3870 N. In the JBiSE paper from 2010, the cannulated triangular configuration was 3709–4423 N. The compression hip screw from the JOT study was 5653 N. In the JBiSE, the DHS and DHHS screw fixation across the 3 moment arm distances ranged from 4247 to 5655 N, therefore our load to failure values were similar.
The current JOT article has the same final conclusion and clinical recommendation that we made in 2010. Both studies found that the use of a compression screw and side plate along with a derotation screw is superior to cannulated screws in a Pauwels Ill fracture.
We encourage Johnson et al as well as the readers of JOT to view our previously published work on the topic of biomechanics of fixation of Pauwels Ill fractures.