The radiographic relationship between the cortical overlap view (COV) and the tip of the greater trochanter

Bjorn-Christian Link,Hans H De Boer,Chittawee Jiamton,Matthias Knobe,Piyabuth Kittithamvongs,Katja Boernert,Sven Nebelung,Nicole M Van Veelen,Steffen Ruchholtz,Reto Babst,Frank J.P Beeres,Filippo Migliorini

doi:10.1038/s41598-021-97951-8

Abstract

For proximal femoral nailing, choosing the proper entry point with the aid of C-arm imaging is crucial. Therefore, obtaining accurate radiological views that facilitate sound identification of the tip of the greater trochanter (GT) is of utmost importance. The aim of this study was to define a radiological view characterised by reproducible radiographic landmarks which will allow the reliable identification of the tip of the GT in the anteroposterior view. Anatomical and radiographic features of 16 cadaveric femurs were analysed. The cortical overlap view (COV), characterised by the radiological overlap of the density line of the piriform fossa and the intertrochanteric crest, was identified. It marks the rotation of the proximal femur at which the GT can be accurately identified and used to determine the desired entry point for a proximal femoral nail. Trainees and fully qualified orthopedic trauma surgeons were asked to identify the correct COV in radiological imaging series. Mean internal rotation of the femur to achieve a COV was 17.5° (range 12.8°–21.8°). In the COV the tip of the GT is the highest visible point and the mean distance from the cortical overlap line to the tip of the GT is 4.45 mm. Intra- and inter-rater reliability was high with ICC(2,k) = 0.932 and ICC(2,k) = 0.987 respectively. Trainees achieved higher rates of correct COV identification than specialists. There was no significant correlation between the internal rotation of the femur to achieve the COV and femoral antetorsion. In conclusion, the COV is a highly reproducible radiological view that is characterised by radiographic landmarks easy to recognise. It allows for accurate identification of the tip of the GT, which can be used by the surgeon as a reference to determine the desired entry point for an intramedullary nail.

Highlights

For proximal femoral nailing, choosing the proper entry point with the aid of C-arm imaging is crucial
Several studies have described the tip of the greater trochanter (GT) as the standard entry point for trochanteric nails[9]
A Kirschner wire was inserted into the tip of the GT, which we defined as the intersection between the line connecting the centre of the femoral head to the centre of the femoral neck on an axial view and the most proximal aspect along the greater trochanteric crest on the ap view (Fig. 1)

Summary

Introduction

For proximal femoral nailing, choosing the proper entry point with the aid of C-arm imaging is crucial. The aim of this study was to define a radiological view characterised by reproducible radiographic landmarks which will allow the reliable identification of the tip of the GT in the anteroposterior view. The cortical overlap view (COV), characterised by the radiological overlap of the density line of the piriform fossa and the intertrochanteric crest, was identified It marks the rotation of the proximal femur at which the GT can be accurately identified and used to determine the desired entry point for a proximal femoral nail. The COV is a highly reproducible radiological view that is characterised by radiographic landmarks easy to recognise It allows for accurate identification of the tip of the GT, which can be used by the surgeon as a reference to determine the desired entry point for an intramedullary nail. Knowledge of the radiological anatomy of the proximal femur is imperative

Objectives

Methods

Results

Conclusion