98. Viseur externe pour le verrouillage distal du Clou Gamma® long. Etude comparative - Distal targeting device for distal locking of long Gamma nail ®. Comparative study

M Ehlinger, G Taglang, D Brinkert, P Adam, F Bonnomet (Strasbourg)

We to bring to you this work from the Trauma Unit of Strasbourg University Hospital about our experience of using the distal targeting device when performing long gamma nails.
For long time, performing a short gamma nails to treat trochanteric fractures is very popular in our team, the distal locking being an easy step of the procedure owing to the distal locking being built in the nail holder.
With the long gamma nail, as it is the case with most diaphyseal nails, distal locking has mostly relied upon the combined skills of the x-ray manipulator and the surgeon through the obtention of « round holes ». Lafforgue’s frame is no longer in use and distal locking, coming at the end of the procedure should be easy, quick and the least irradiating as possible, and be performed once the proximal screw has been set and secured.
Can a distal targeting device, derived from other aiming devices, and pre-clinically tested in the anatomy lab, promote safe setting of the distal locking screws and decrease irradiation for that specific part of the procedure?
To answer this question a consecutive series of 100 long gamma nails, operated by one experienced surgeon from 8/2007 to 12/2008 were allocated to either freehand technique of distal locking or the use of the distal targeting device. Irradiation time for distal locking was recorded. Statistical analysis used Wilcoxon’s test for quantitative datas with R software.
In addition, our local experience using this device, which is under a continuous survey, through 170 cases of multioperator long gamma nails using this distal targeting device. There were 128 orthinox nails and 42 titanium nails. In all cases the femur is over reamed by 3 mm.
When using the distal targeting device, positionning of the patient is as usual performed on the traction table to achieve reduction on both frontal and sagittal plane.
Once the proper length of the nail has been chosen by mesurement on the intramedullary guide wire, the targeting device is premounted on the nail holder and at the appropriate length and distal calibration is performed outside the patient.
The nail is inserted and once the neck screw has been set, the distal targeting device is mounted again.
The principle of this device is to obtain an aligement of the drilling sleeve with the distal part of the nail and the optimal positionning of the Carm is to form a 60° angle with the femur.
Rotation of the C-arm in the appropriate direction allows good alignement of the sleeve with the nail.
Once the alignement is obtained the height of the sleeve can be fine tuned without having the hands of the surgeon within the irradiation field. It is important to release the soft tissues around the sleeve in order to avoid any bending at that stage.
The most distal hole is drilled first, the screw is inserted and the screwdriver is kept on the screw to stabilize the construct and allow the most proximal hole to be drilled.
following these principles, the following results were obtained in the single operator comparative series.
The two populations look clearly different with a median irradiation time of 26′ for the freehand technique and 84 for the distal targeting device group. The difference is also highly statistically different.
In the multiple operator survey, two miss-drillings were observed, at the beginning of the experience, and both cases were preventive nailings on metastatic lesions, using titanium nails.
A fine tuned correction was necessary in 10% of orthinox nails and in two thirds of titanium nails, with a maximal correction of 14 mm in two titanium nails.

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