Progress towards intra-operative measurement of femoral antetorsion

Important tips and numbers on using the cortical step and diameter difference sign in assessing femoral rotation--should we abandon the technique?

Rotational malalignment during femoral nailing is common despite having various intraoperative assessment methods. The cortical step sign and diameter difference sign (CSSDDS) is commonly used because of convenience, yet it lack proper scientific scrutiny and is thought to be error prone. Using a software algorithm, cross-sectional dimensions were obtained from CT scans of 22 intact adult femurs at the proximal, mid and distal diaphysis. With multiple simulated scenarios the sensitivity of CSSDDS was comprehensively determined at all possible C-arm positions. At rotation, cortical width changed most significantly around the thick linea aspera and femoral diameter changed most significantly at the sagittal plane. At 15 degrees of rotation and with the linea aspera in view, CSSDDS thresholds of 0.3mm, 0.6mm and 1mm had sensitivities of 98.8%, 93.1% and 73.8%. With the linea aspera masked behind the femur and out of view, the sensitivities significantly deteriorated to 96.4%, 77.1% and 44.1% respectively. CSSDDS is sufficiently sensitive only when strict rules are followed. It is imperative that the operator position the image intensifier in lateral view under proper magnification so that steps of less than 0.6mm around the linea aspera may be appreciated.

A preliminary clinical evaluation of the "greater trochanter-head contact point" method for the intraoperative torsional control of femoral fractures

PURPOSE

In a previous study, our group introduced a simple non-invasive method for the intraoperative control of femoral torsion during closed nailing of femoral fractures using the shape of the greater trochanter and its relation to the femoral head. The aim of this study was to verify the results of our cadaveric study and transfer them into a clinical setup. We answered the questions: How much time is needed to perform the greater trochanter-head contact point method (GT-HCP)? How long is the radiation time?

METHODS

We examined 15 patients with femoral shaft fractures, to evaluate the GT-HCP method in a clinical setup. Using a standard fluoroscopic image intensifier (Ziehm, Erlangen, Germany), the greater trochanter-head contact angle was measured for both sides. All patients received a postoperative computer tomography (CT) to check the rotational malalignment. The mean of the CT results was then compared to the measurements of the GT-HCP method. The examiners performing the CT measurements were not aware of the GT-HCP results and vice versa.

RESULTS

No statistical significance could be detected between the CT and the GT-HCP method (p = 0.853). Eleven patients had very good results (≤5°), three had good results (6-10°) and one had poor results (>10°). The mean difference between CT and GT-HCP method was 3.7 ± 3.3°, which is acceptable. The radiation dose needed for the method was not large (0.2 ± 0.1 min), and could be lowered with the gaining experience of the examiners. Similarly, the overall time needed (12.1 ± 4.9 min) for the GT-HCP method could be reduced with the experience of the team.

CONCLUSION

Our study showed that the GT-HCP method is a precise and not particularly time consuming method for controlling anteversion during closed femoral nailing. Further clinical trials including a larger number of patients are required to establish this method in clinical practice.