The EOS system is based on a newly invented type of gas detector,
which in 1992 earned the Nobel Prize for physics to its inventor.
Thanks to this new device,
it is possible to obtain radiological images of superior quality to the standard ones,
with a strong reduction of the radiation dose absorbed by the patient.
The system is used above all for the study of diseases that affect the spine.
This examination is performed in orthostatism giving the possibility to the radiologist to check for any differences in level between the femoral heads with consequent surgical planning and related follow-up distributed over time.
It is also possible to check the positioning of the orthopedic corsets and perform the study of the lower limbs.
Through the software and with dedicated Tools you can perform measurements on 3D images such as:
detections between two anatomic landmarks,
corners
diameters.
The approach of the tube and its collimation also result in a 1: 1 scale X-ray image avoiding in this way two drawbacks typical of traditional radiography,
such as:
the removal of the tube with consequent increase in the dose;
the possible geometric deformation,
above all in the upper and lower part of the image.
EOS uses a new type of gas detector,
based on the multiplication effect of charge in a rare gas.
This electronic avalanche effect generates a measurable electrical signal directly,
which is then digitized.
The system has been designed to minimize diffuse radiation,
improve the signal-to-noise ratio and dynamic range,
making it possible to obtain high quality images with a lower dose of radiation.
Between november 2016 and february 2017 54 consecutive patients (23 males,
31 females, average age 58,9 years (range 44-78) underwent total hip arthroplasty (THA).
Inclusion criteria were: primary coxarthrosis,
secondary coxarthrosis due to mild hip dysplasia,
Perthes o epiphysiolysis or avascular necrosis of the femoral head.
Exclusion criteria were: partial revision or total revision of THA,
THA associated with other procedures,
previous pelvic or femoral osteotomy,
fracture,
severe hip dysplasia,
congenital hip dislocation,
primary or secondary tumors with involvement of the coxofemoral joint,
previous spinal or sacroiliac stabilization,
previous or current infection at coxofemoral level.
Preoperative diagnosis was consistent with primary coxartrosis in 41 patients,
coxartrosis secondary to mild hip dysplasia in 10 patients,
coxarthrosis secondary to avascular necrosis of the femoral head in 1 patient and coxarthrosis secondary to epiphysiolysis in 2 patients.
Average,
standard deviation and range of dose area products,
together with the average of the equivalent dose have been assessed with a dedicated in-house software of dose management (DoseWatch™) in anteroposterior and lateral lateral projections before and after THA.
Percentage change of the dose administered before and after THA has been calculated.