Replacing a hip joint with a prosthesis requires careful pre-operative planning. In addition, legally mandated planning and related documentation require a true-to-scale radiograph. But many hospitals have abandoned printed radiographs and pencil-and-ruler planning procedures. Modern institutions with specialties like orthopedics, general surgery, and spinal surgery frequently perform hip implants and knee prostheses. Such institutions are increasingly turning to digital planning solutions. mediCAD is an advanced, computerized planning system in use around the world. With this solution, the surgeon uses common digital radiographs to plan prostheses entirely on a computer screen. The benefits of this approach are significantly faster planning, higher planning quality, and improved documentation. As of mid-2013, more than 700 hospitals around the world use this planning system. One of these hospitals is Klinikum Konstanz in Germany and its Department of Trauma Surgery, Orthopedics, and Hand Surgery. This department performs elective hip and knee operations as well as corrective osteotomies. When they switched to a PACS system, traditional films were eliminated and the hospital decided to perform OP planning with digital tools as well.
Since 2010 the mediCAD digital planning system from hectec GmbH of southern Germany has been in use. Approved as a medical product around the world, this certified planning solution gives surgeons highly effective Computer-Aided Design (CAD) tools like those used by designers, architects, and technical draftsmen. In hip endoprosthetic procedures, ligamentary stability is of less concern, so pre-operative planning can be largely standardized and performed effectively on a screen. However, CAD planning is also useful for knee prostheses, particularly revision operations and when planning corrective osteotomies.
Department Head Dr. med. Jörg Tinsel considers time savings to be the lessor of the benefits of digital planning: „Now we can better document our planning, removing a great deal of uncertainty.“ Users like the system for its functionality and because it contains all of the necessary features. One of those features is an extensive database of prosthetic parts that can be retrieved and combined with each other on the screen. Digital planning also enables a variety of options for depicting leg length discrepancies and leg axis positions on the screen. This gives the surgeon the ability to compare various prostheses and ultimately select the most optimal solution. „I'm able to see the cause of a defective position. The digital imagery provides clues about optimization that I wouldn't otherwise have, and then I can easily browse through multiple solutions on the screen,“ according to Dr. Tinsel. The straightforward operation of the solution is a big benefit, since all major functions can be retrieved with a click of the mouse.
Ultimately it is important that measurements are reproducible and therefore valid. For this purpose, mediCAD uses a 25-mm diameter calibration sphere that is shown on every radiograph. The sphere is placed near the joint at the height of the bone before the image is taken, thereby enabling highly precise, error free planning.
Planning is performed in a few simple steps. The first step is to select the patient from a digital image archive. The archive stores radiographs of all patients, giving authorized employees immediate access whenever needed. They then select the desired image and export it to the digital planning software. The next step in the planning utilizes the sphere to perform a true-to-scale calibration of the radiograph. Then, any necessary compensation of the leg length is established directly on the screen. The new femoral head's center of rotation is likewise established directly on the screen. If the hip damage is so far advanced that it becomes impossible to determine the center of rotation, the center of rotation of the other joint will be determined and transferred to the damaged hip. The distance between the tip of the prosthesis and the trochanter minor is measured directly on the screen. This serves as an intra-operative reference and ensures the correct leg length after the operation.
In the next step, the doctor refers to the planning program's implant database to select a suitable implant. hectec continuously updates this database. The current version includes products from 90 global manufacturers and covers more than 80% of all implants used in Europe. In the event that a template is missing, the manufacturer will supply it at no charge. Regular updates are also provided at no additional charge.
Next, the surgeon selects a suitable implant by manufacturer, type (cup, shaft), model, version, and size. The selection step is performed directly on the screen as well. Cup size and position are finely adjusted interactively with arrow keys on the keyboard; each implant can be rotated, enlarged, or reduced in size.
Once all corrections have been completed on the skeleton, mediCAD merges the templates and optimizes how they fit together. The final planning is then saved and documented without losses, ensuring legal security. If the planning is preliminary, it will remain in mediCAD and can be refined at any time.
The hospital in Konstanz currently uses digital planning for approximately three operations per week. The integration of a once physically separate orthopedic clinic will significantly boost this figure.