Operationen an der Hüfte sind längst keine Seltenheit mehr: Rund 180.000 Menschen lassen sich laut dem Institut für angewandte Qualitätsförderung und Forschung im Gesundheitswesen (AQUA) allein in Deutschland jährlich ein künstliches Hüftgelenk einsetzen. Von Jahr zu Jahr werden es mehr Patienten – jene, bei denen erstmals eine Prothese eingesetzt wird, und jene, bei denen die Prothese gegen eine neue ausgetauscht werden muss. Um die Muskeln zu schonen und die Genesung zu beschleunigen, wird bei der Operation in beiden Fällen seit einigen Jahren in erster Linie ein minimal-invasiver Zugang gewählt.

Hip operations have long since become commonplace. According to the Institute for Quality Assurance and Research in Health Care (AQUA), 180,000 patients have a hip joint replacement each year – in Germany alone. And this number is rising from year to year. Some have this prosthesis installed for the first time, while for others the old artificial joint requires replacement. To minimize the impact on the muscles and in the interest of speedy recovery, minimally invasive surgery has been used for the main part, in both situations, for several years now.

Hip replacement surgery is on the agenda at the Frauenfeld Cantonal Hospital in Switzerland, too, with about two hundred such operations scheduled there each year. Dr. Paul-Michael Bodler, Chief of Surgery in the Orthopedics Department, performs  the majority of these interventions with the help of an extension unit. It is attached to the operating table; the patient’s feet and calves are secured comfortably in special. extension boots. The advantages during surgery: The special struts and the MIS-hip-device for the extension unit make it possible to move the legs independent of each other and to rotate, flex, abduct or adduct them – accurate right down to the last degree. Thus the leg is put precisely in the position needed for each step in the surgery. A thickly padded counter-traction post ensures that the patient rests securely on the operating table during every movement of the lower extremities.

Free-floating and space-saving

Another major advantage: The entire extension unit is mounted only on the operating table; it requires no floor supports. That makes it especially flexible and saves space.  At the same time, this configuration provides good access for a mobile C-arm. It is also important that the large majority of the components be radiolucent. Significant in the extension units with the MIS-hip-device made by TRUMPF are carbon-fiber reinforced components and an intelligent arrangement of the joint locations, in some cases with detachable joints. This makes possible 3-D imaging in the pelvic and leg areas. To date, the Frauenfeld has had only one extension unit with an MIS hip unit, but it is soon to be joined by others. “In the final analysis, this unit can be used not only for hip replace-ments, but also for operations to treat fractures of the femur or pelvis – and for hip arthroscopy, too,” Bodler explains.

Standardized procedures minimize errors

Bodler’s objective is to standardize procedures during surgery in order to minimize errors. “This extension unit makes that possible – and simple. All the adjustments can be reproduced exactly.” During minimally invasive hip operations with the extension device, the surgical team always proceeds in exactly the same way. Once the surgeon has made the incision, the assistant uses special hooks, designed to be gentle on the muscles, to expose the operating area. After the hip joint has been separated, the nurse responsible for positioning extends the leg with the help of the extension spindle. The surgeon now gets the head of the femur ready for detachment and uses the oscillating saw to separate it from the femur.

The extension is then relieved completely. In this way the risk of damage to the nerves can be reduced significantly. The surgeon now has unrestricted access to the cetabulum. To create the space required for the artificial socket, he uses a milling unit, working step by step, with ever larger cutting tools, until the appropriate cement-free socket can be driven in place. Once the socket implant is in place, preparations begin for positioning the prosthesis for the femoral head. Here the MIS-hip-device shows what it can really do. The extension spindle is used to rotate the leg ninety degrees to the outside, where it is hyperextended and adducted. This gives the surgeon the best access to the femur. Then the shaft is rasped to the correct size. The trial prosthesis head is positioned and the joint is reset. The extension unit is used to put the leg into its anatomically correct position. Then the hip is X-rayed to verify that all the implants are correctly seated. If the X-ray images look good, then the leg is returned to the surgical position. The surgeon removes the trial components and sets the final implant. The joint can now be reset by applying extension and inward rotation. To close up, it is necessary only to restore the fascia, the subcutaneous fatty tissue and the skin.

Always at the right angle

During these procedures the extension unit keeps the patient’s leg in the ideal position throughout, and for as long as necessary. Just as important: To ensure that there is no improper positioning of the pelvis, even in the extreme positions sometimes required, the extension unit ensures that the healthy leg is held in a compensating position. After the operation, the unit can be removed from the operating table with just a few motions. The patient needs hardly be moved at all for this purpose. It is sufficient to loosen the closure for the extension boot and release the foot. A transport shuttle is then used; the operating table top is transferred from the column and the patient is moved out of the OR on the table top.

Even though reduced tension may make things more comfortable for the surgeon when using the extension unit and the MIS-hip-device, this minimally invasive procedure is rendered no less complex. “The learning curve is about the same. With the extension unit, too, it takes about thirty operations before things become routine.” Only then can a surgeon carry out the procedure alone. “Because of the narrow field of vision during MIS, the surgeon has to have a very precise concept of how the socket will need to be positioned, for instance. Otherwise the risk of improperly oriented components is very high. “But on balance,” according to Bodler, “the operation is far gentler on the patient, the muscle structure is uninjured and the patient can be up and about on the very next day.”