Validation of direct CT measurement of malrotation in femoral neck fractures: A bone model study

PLOS ONE RESEARCH ARTICLE Validation of direct CT measurement of malrotation in femoral neck fractures: A bone model study Emmanouil Liodakis1☯, Gesa Helen Pöhler2☯, Lena Sonnow2, Philipp Mommsen1, JanDierk Clausen1, Tilman Graulich1, Alexander Maslaris3, Mohamed Omar1, Timo Stübig1, Stephan Sehmisch1, Tarek Omar Pacha ID1* a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Trauma Department, Hannover Medical School (MHH), Lower Saxony, Germany, 2 Department of Radiology, Hannover Medical School (MHH), Lower Saxony, Germany, 3 Department of Orthopaedics and Trauma Surgery, Alfried Krupp Hospital, Campus Rüttenscheid, Essen, Germany ☯ These authors contributed equally to this work. * Abstract OPEN ACCESS Citation: Liodakis E, Pöhler GH, Sonnow L, Mommsen P, Clausen J-D, Graulich T, et al. (2023) Validation of direct CT measurement of malrotation in femoral neck fractures: A bone model study. PLoS ONE 18(4): e0278850. https://doi.org/ 10.1371/journal.pone.0278850 Editor: Hans-Peter Simmen, University Hospital Zurich, SWITZERLAND Received: June 29, 2022 Accepted: November 27, 2022 Published: April 4, 2023 Copyright: © 2023 Liodakis et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting information files. Funding: None of the authors have any professional or financial affiliations that could have biased this study. Funding awarded by the TraumaStiftung gGmbH (Carl-Neuberg - Str. 1, 30625 Hannover/ Award No 009EFC7A-FB9847A0-81EC-EAF7B812C5ED) was used to construct the femoral neck goniometer and for all Background While postoperative malrotation in the subtrochanteric region is a well-known problem, malrotation after osteosynthesis in proximal femoral fractures has not been extensively studied. In this context, many methods for perioperatively assessment of femoral torsion have been described, but none of them is applicable in the basicervical region of the proximal femur. As an important difference in femoral neck fractures, the discontinuous neck fails to serve as a significant “pointer” for measurements and malfunctions to be placed in relation to the condylar plane. Considering postoperative maltorsion at any location as a substantial negative effect on patients’ outcome and functional expectations, precise and patient-friendly rotation measurement standards in femoral neck fractures are desired in clinical practice. Recently, a novel computed tomography (CT) based geometric technique was described named “direct measurement” with promising results covering this diagnostic disparity, but still requires validation. Thus, we aimed to validate the previously described technique using a controlled range of displacement in a femoral neck fracture Sawbone® model. Methods and findings A goniometer was designed to set retro- and anteversion of the proximal femur in a reproducible manner. Prospectively, all femurs underwent a CT scan and were measured 3D for displacement. The interclass correlation between the CT measurements and the goniometer measurements was calculated and was found to be very high (1.00, 95% confidence interval: 0.99–1.00; p < 0.001). For the mean of all measurements, the Pearson’s correlation was 1.00 (p < 0.001). No significant differences in the measurements of both investigators were observed, with 20˚ of retroversion not significant (-1.20 ± 1.71; 95% confidence interval: -2.43–0.03; p = 0.054). PLOS ONE | https://doi.org/10.1371/journal.pone.0278850 April 4, 2023 1 / 12 PLOS ONE other materials required for performing this experimental study. Competing interests: The authors have declared that no competing interests exist. Validation of measurement of malrotation of femoral neck fractures Conclusion This CT-based 3D measurement technique may allow for perioperative malrotation assessment in basicervical femoral neck fractures and appears to be feasible in femoral neck fractures when it comes to rare cases of osteosynthesis. Further investigations are still needed to define the thresholds of malrotation provoking functional impairment after osteosynthesis in basicervical femoral neck fractures. Introduction Proximal femoral fractures are ranked third of all fracture types [1, 2], hospitalizing approximately 300,000 patients per year in the United States, with an increasing tendency and estimated range of 6–21.3 million patients worldwide by 2050 [3, 4]. Proximal femoral fractures can be stratified by location into: subtrochanteric, intertrochanteric, and femoral neck fractures (FNFs) [4]. FNFs are gaining more importance, being a typical fracture of the elderly patient, with an incidence of 100,000 per year in the German population and affecting about 30% of all women [5]. Regarding FNFs, osteosynthesis, total hip arthroplasty, and hemiarthroplasty have to be considered, depending on the fracture type, patient age, and compliance [4, 6]. Valgus impacted and less-displaced fractures (Garden type I and II) can be treated by osteosynthesis, even in elderly patients [4, 5, 7]. Patients with higher grades of displacement are treated by hemiarthroplasty or total hip arthroplasty in older patients and by osteosynthesis in young patients [4, 6, 7]. In FNFs, subcapital and midcervical fracture types are common, and are mostly treated by arthroplasty, especially in elderly patients. In contrast, basicervical FNFs (1.8–7.6% of all PFFs) [4, 8] and higher displaced fractures in the midcervical area in young patients are treated with cephalomedullary nails, dynamic hip screws, or cancellous screws [4, 5, 8, 9]; thus, the best method is still under discussion [10]. While postoperative malrotation in the subtrochanteric region is a common and well-known problem [11–13], malrotation after osteosynthesis in FNFs, especially in the basicervical region, is less often described [7, 14]. Also, a generally accepted threshold from which one has to perform corrective therapy is still missing. Given the widely accepted practice of providing joint replacement in elderly, this fact may be one explanation for the only few literatures of malrotation after osteosynthesis in patients with fractured femoral necks. The postoperative diagnosis of malrotation in adults is typically a domain of computed tomography (CT) [15, 16], engaging various geometrically based measurement techniques [16–18]. All measurement techniques of femoral shaft malrotation use the femoral neck as a “pointer,” assessing ante- or retroversion compared to the distal femoral joint line. In fractures proximal to the intertrochanteric line, this “pointer function” cannot be applied as the neck is fractured. Therefore, in 2021, a simple geometric and CT based measurement technique was introduced for the assessment of (...truncated)