Abstract
Introduction
Total hip arthroplaty (THA) using direct anterior minimal invasive (AMI) surgery is an attractive option to achieve a quicker habilitation. However, high complication rates were reported and very often related to technical difficulties at the time of surgery. We hypothesized that 3D preoperative planning may allow to anticipate these difficulties and to decrease the complications rates when using an AMI approach.
Material and methods
A prospective observational study included 191 consecutive patients who underwent a primary cementless THA using an AMI. A 3D CT-scan based pre-operative planning was performed in order to anticipate the potential difficulties that may be encountered especially regarding the hip anatomy reconstruction and the implants stability. The components size and position were planned in order to restore the leg length, the offsets, and the anteversions. Postoperatively, a CT scan was performed in order to compare the final anatomy to the planning.
Results
The real implants were the same than the ones planned in 94% for the cup, 96% for the stem and 100% for the neck. The hip anatomy was restored with a high accuracy: 0.1±3mm for the hip rotation centre, −1.6±3 mm for the leg length and 0.1±2.5mm for the femoral offset.
All the surgical difficulties were anticipated. No false route and no dislocation occurred. A motorized reaming procedure of the femur was required in 6 patients because a very dense bone associated to a narrow femoral diaphysis. A varus neck was used in 60 % of cases mainly in order to compensate a decrease in the acetabular offset generated by the reaming procedure imposed by the acetabular dysplasia. A retroverted neck was used in 8% of patients because of a torsional abnormality and allowed to increase the stability (Figure 1).
A severe femoral dysplasia was treated with a custom stem in 7% of cases in order to avoid a rotational osteotomy of the femur a trochanteromy (Figure 2).
Discussion
No complication happened at the time of surgery and no dislocation occurred afterwards. False routes were avoided probably also thanks to the shape of the anatomic stem which presents an anterior sagittal curvature. This shape allowed an easier rasping procedure despite the limited exposure of the femur.
Conclusion
3D planning anticipates the potential surgical difficulties at the time of THA, and allow to increase the safety and the accuracy of the surgical procedure.
