F. Gelaude

A custom-made guide-wire positioning device for Hip Surface Replacement Arthroplasty: description and first results

BackgroundHip surface replacement arthroplasty (SRA) can be an alternative for total hip arthroplasty. The short and long-term outcome of hip surface replacement arthroplasty mainly relies on the optimal size and position of the femoral component. This can be defined before surgery with pre-operative templating. Reproducing the optimal, templated femoral implant position during surgery relies on guide wire positioning devices in combination with visual inspection and experience of the surgeon. Another method of transferring the templated position into surgery is by navigation or Computer Assisted Surgery (CAS). Though CAS is documented to increase accurate placement particularly in case of normal hip anatomy, it requires bulky equipment that is not readily available in each centre.MethodsA custom made neck jig device is presented as well as the results of a pilot study.The device is produced based on data pre-operatively acquired with CT-scan. The position of the guide wire is chosen as the anatomical axis of the femoral neck. Adjustments to the design of the jig are made based on the orthopedic surgeons recommendations for the drill direction. The SRA jig is designed as a slightly more-than-hemispherical cage to fit the anterior part of the femoral head. The cage is connected to an anterior neck support. Four knifes are attached on the central arch of the cage. A drill guide cylinder is attached to the cage, thus allowing guide wire positioning as pre-operatively planned.Custom made devices were tested in 5 patients scheduled for total hip arthroplasty. The orthopedic surgeons reported the practical aspects of the use of the neck-jig device. The retrieved femoral heads were analyzed to assess the achieved drill place in mm deviation from the predefined location and orientation compared to the predefined orientation.ResultsThe orthopedic surgeons rated the passive stability, full contact with neck portion of the jig and knife contact with femoral head, positive. There were no guide failures. The jig unique position and the number of steps required to put the guide in place were rated 1, while the complexity to put the guide into place was rated 1-2. In all five cases the guide wire was accurately positioned. Maximum angular deviation was 2.9° and maximum distance between insertion points was 2.1 mm.ConclusionsPilot testing of a custom made jig for use during SRA indicated that the device was (1) successfully applied and user friendly and (2) allowed for accurate guide wire placement according to the preoperative plan.

Computer-aided planning of reconstructive surgery of the innominate bone: Automated correction proposals

Objective: In cases of complex reconstructive surgery of the innominate bone, it is difficult to draw up a good surgical plan; manual planning of a 3D reconstruction is highly demanding and time-consuming. This paper presents and validates methodology to automatically generate 3D correction proposals for reconstructive surgery of the innominate bone, and illustrates its use with clinical applications. Materials and Methods: The developed Matlab® methodology starts from CT-based outer surface representations of the patients bone, which allow straightforward mirror and matching implementations for automated reconstruction procedures. The validation on 9 cadavers was two-fold: the geometrical deviations of the intact original with respect to the reconstructed surface meshes were assessed, and the characteristics of both original and reconstructed acetabular cup regions were determined. Results: Eighteen healthy and thus, it was assumed, spherical acetabula were automatically reconstructed with mean accuracies of 3.2 ± 2.2 mm, 0.1 ± 1.0 mm and 3.8 ± 2.9° for the hip joint centerpoint, joint radius and cup orientation, respectively. As a demonstration, a triflange cup acetabular implant was rapidly designed, starting from the correction proposal. Conclusions: A highly automated, computer-aided approach to surgical planning for pelvic bone defects was developed and sample applications demonstrated. Validation results for healthy acetabula were superior to those obtained in real surgery. The generated virtual correction proposals can be used as targets in surgical planning and cup navigation applications, or in the design of customized implants with complex shapes.

Virtual anatomical reconstruction of large acetabular bone defects using a statistical shape model

Custom implants are used to treat patients with large acetabular bone defects. To quantify the bone defect and to initialize the implant design, a virtual anatomical reconstruction of the bone needs to be performed. Our SSM-based reconstruction approach was used to overcome the limitations of the mirrored contralateral method and improves upon other SSM reconstruction techniques. The reconstruction errors for the acetabular direction, the hip joint center and the acetabular radius were, respectively: , 2.6 mm and 0.7 mm. We believe that our method can be an essential tool in the planning and the design of custom implants.

Patient-Specific Reconstruction of Large Bone Defects: Clinical Success Due to an Integrated Bioengineering Workflow

Surgical reconstruction of major acetabular defects (Paprosky type IIIb) in view of total hip replacement is a challenge. Existing systems have a documented failure rate between 20% and 50% at five years post-operatively. Our first hypothesis is that this limited success is due to the fact that standard components have to be adapted and assembled intraoperatively to provide a patient solution. Hence our second hypothesis is that a fully personalized solution for acetabular reconstruction will provide an added value for the patient’s outcome.