Abstract:

Computer-assisted surgery (CAS) for total knee replacement was first approved for use in the U.S. in 2001. Since its introduction, however, there has been a rapid expansion of this technology and several different types of navigation systems have been developed by several different manufacturers. Each new version of the software has incorporated increasingly sophisticated analysis modules to allow not only accurate alignment of the limb and component position, but also to assess ligament balance and knee kinematics. The purpose of this chapter is to review the basic elements of CAS, the author's clinical experience, and improvements currently being developed with this technology.

Authors:

Michael L. Swank, M.D. - Cincinnati Orthopaedic Research Institute, Cincinnati, Ohio

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Abstract:

The purpose of this study was to retrospectively compare the clinical and radiographic results of the Maxim Posterior Stabilized Constrained (PCS) (Biomet Orthopaedics, Inc., Warsaw, IN, USA) knee system using the hybrid fixation versus the fully cemented fixation of stems of the same length. The cohort in this study included 115 knees in 104 patients, with a minimum 2-year follow up postoperatively. All patients were evaluated with the Knee Society clinical rating score and roentgenographic evaluation. Of the 115 revision total knee arthroplasty (TKA) cases, the hybrid-fixation technique was used on both the femoral and tibial components of 75 (Group I–hybrid femur, hybrid tibia); the fully cemented technique was used on both components of 24 (Group II–cemented femur, cemented tibia); the hybrid-fixation technique was used on the femoral component and full cement on the tibial component of 13 (Group III–hybrid femur, cemented tibia); the femoral component was fully cemented, and tibial component had the hybrid-fixation technique used on 3 (Group IV–cemented femur, hybrid tibia). The average follow up was 44 (range: 24-126) months. At the most recent evaluation, the Knee Society score improved from an average preoperative value of 51.7 to 76.7, the pain score improved from 14.0 to 33.3, and the functional score improved from 40.5 to 47.0. The average stem-to-canal fill ratio was 80% in the femur and 85% in the tibia (p<0.05). Stem-to-canal fill ratio did not appear to influence clinical outcome. Radiolucent lines less than 2 cm were observed more frequently in the hybrid-cemented stems (89%) than the fully cemented stems (58%) at an average 8-year follow up postoperatively (p<0.05). A lower, but not statistically significant, failure rate was observed in the hybrid group in comparison with the cemented group.

Authors:

Je Gyun Chon, M.D. - Joint Implant Surgeons, Inc., Columbus, Ohio, Department of Orthopaedics, Sun General Hospital, Daejeon, Republic of Korea; Adolph V. Lombardi, Jr., M.D., F.A.C.S. - Joint Implant Surgeons, Inc., Chairman of The Department of Surgery, New Albany Surgical Hospital, Department of Orthopaedics, The Ohio State University, Columbus, Ohio, Biomedical Engineering, The Ohio State University, Columbus, Ohio; Keith R. Berend, M.D. - Joint Implant Surgeons, Inc., Division of Adult Reconstruction, Department of Orthopaedics, The Ohio State University, Columbus, Ohio

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Abstract:

This chapter describes a technique for reconstruction of the knee extensor mechanism disruption after total knee replacement (TKR). Disruption of the knee extensor mechanism is an infrequent but serious complication. The options for treatment include observation, bracing, fixation with sutures or staples, autologous-tissue augmentation with use of the semitendinosus or gracilis tendon, turndown of the quadriceps tendon and reconstruction with an intercalary allograft. These options have been associated with a high risk of complications and have not addressed the associated problems of contracted devascularized skin flaps or deficient patellar bone stock. The medial gastrocnemius flap has been shown to be suitable for providing soft-tissue coverage of the proximal aspect of the tibia, knee, and distal aspect of the femur. Historically the technique for reconstruction of the extensor mechanism was described for limb salvage after resection of proximal aspect of the tibia for malignant tumors. This described technique is an adaptation of such previously accepted techniques for disruption of the extensor mechanism after total knee arthroplasty (TKA). The use of a medial or an extended medial gastrocnemius flap appears to be a reliable option for reconstruction of a ruptured extensor mechanism after TKA.

Authors:

Michael L. Gitomirski, M.D., Henry A. Finn, M.D. - Department of Surgery, The University of Chicago, Chicago

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Abstract:

Patella baja, that can be divided into congenital, acquired, or a combination of the two, is commonly encountered in total knee arthroplasty (TKA). Congenital patella baja refers to a patella distal in relationship to the femoral trochlea and present since an early age. Acquired patella baja may occur secondary to distal positioning of the patella relative to the femoral trochlea or shortening of the patellar tendon, as a result of trauma or surgery. Patella baja also can occur postoperatively as a result of scarring and shortening of the patellar tendon, scarring of the patellar tendon to the anterior aspect of the tibia, or both. Another cause of acquired patella baja seen commonly in TKA is elevation of the joint line, referred to as pseudo-patella baja. The patella remains in a normal position relative to the femoral trochlea; however, the distance between the patella and tibia is narrowed. Pseudo-patella baja can be a result of tibial or femoral over-resection, which necessitates a large polyethylene insert. Alterations of the patello-tibial distance can occur during TKA by excessive soft-tissue release that requires elevation of the joint to regain stability and placement of the patellar polyethylene component distally on the patella. Prevention is the easiest way to avoid potential problems with patella baja during TKA; however, the surgeon is often confronted with this situation during total knee revisions. Failure to address patella baja can lead to decreased range of motion (ROM), a decreased lever arm, extensor lag, impingement of the patella against the tibial polyethylene or tibial plate, anterior knee pain, increased energy expenditure, and rupture of the patellar or quadriceps tendons. Treatment of patella baja first depends on determining the cause and distinguishing between patella baja and pseudo-patella baja. Five different methods to measure patella baja are reviewed and include: (1) Blumensaat's line, (2) Insall-Salvati ratio, (3) Modified Insall-Salvati ratio, (4) Blackburne-Peel, and (5) Caton-Deschamps. Corrective measures include reestablishing the joint line by use of distal femoral augments, tibial tubercle osteotomy with proximal displacement, lengthening of the patellar tendon, shaving of the anterior portion of the tibial polyethylene, and placement of the patellar implant in a cephalad position.

Authors:

Douglas J. Chonko, M.S., D.O. - Joint Implant Surgeons, Inc., Columbus, Ohio; Adolph V. Lombardi, Jr., M.D., F.A.C.S., Joint Implant Surgeons, Inc., Department of Surgery, New Albany Surgical Hospital, Department of Orthopaedics, The Ohio State University, Biomedical Engineering, The Ohio State University, Columbus, Ohio; Keith R. Berend, M.D., Joint Implant Surgeons, Inc., Department of Orthopaedics, The Ohio State University, Columbus, Ohio

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Abstract:

Hamstring tendon autografts have, over the past decade, increasingly become the graft of choice for anterior cruciate ligament (ACL) reconstructions. Studies have shown that multiply stranded hamstring grafts have superior biomechanical characteristics when compared to patellar tendon autografts. Harvests of hamstring tendons have been shown to cause less donor-site morbidity than the harvest of patellar bone-tendon-bone grafts. Historically, however, fixation methods for hamstring grafts have limited their successful use. Fixation for both the tibia and femur distant from the intra-articular portions of the graft decreased the stiffness of the construct. The fixation also contributed to tunnel widening and ganglion formation. New methods have been developed to maximize the mechanical strengths of hamstring grafts and optimize biological factors in healing of the graft to the bone tunnels. Femoral cross-pin fixation provides secure fixation close to the knee joint, while also allowing for placement of the graft in the native ACL footprint at the far posterior aspect of the intercondylar notch. Tibial interference screw fixation allows fixation close to the joint as well. Addition of the interlock pin through the interference screw increases pullout strength significantly. Recent advances in material science have led to the development of bioabsorbable implants that afford high initial fixation strengths while limiting subsequent complications from permanent hardware.

Authors:

Troy L. Berg, M.D. - Chippewa Valley Orthopedics and Sports Medicine, Eau Clair, Wisconsin; Lonnie E. Paulos, M.D. - Advanced Orthopedics and Sports Medicine, Murray, Utah

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Abstract:

Within the minimally invasive-operation techniques, small approaches are desirable in many fields of the surgery to reduce soft-tissue trauma; however, the risk exists that the surgeon will lose the general view of the topographic structures. The remedy lies in computer navigation with the OrthoPilot ®. This navigation system has already been used successfully for knee endoprosthesis. A special software was developed for use of the navigation-system, OrthoPilot®, for ACL reconstruction. This system is capable of determining the exact optimum position of tunnel replacement by computer navigation. This determination is made by a high-precisive infra-red camera and rigid bodies fixed onto the patient. The experience gained in performing 150 ACL reconstructions to date demonstrates the ease of handling, reduction in extra operation time to a minimum of 10-15 minutes, and only minimal trauma by fixing the rigid bodies. In all cases, an optimum position was documented for the tunnel replacement. Furthermore, no expensive preoperation x-rays (CT scan, nuclear spin) are needed. Use of the computer-assisted navigation system demonstrated that femoral and tibial tunnel replacement can be positioned precisely. Thus, a false position of the tunnel replacement, the main cause of' transplant-failure, can be avoided. The OrthoPilot® is an important support system for both less-experienced and experienced surgeons when performing surgical ACL revisions.

Authors:

Markus Degenhart, M.D. - Orthopedics Clinic, Schelztorklinik, Esslingen, Germany

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Abstract:

THR has become one of the most widely performed operations in orthopaedic surgery.. In Germany, more than 180,000 THRs are currently done annually with increasing tendency. We use four different types of endoprostheses: (1) cemented, (2) cement-less, (3) hybrid (cement-free implanted socket and cemented stem), and (4) hemi-endoprosthesis (cemented stem without socket). A total number of 600 patients were included in a prospective follow-up study during 5 to 20 years, with a mean follow-up period of 10 years. The relevant question of whether to use a cemented, hybrid, or cement-free version of THR is, in our opinion, no longer a concern. All the methods have their advantages, disadvantages, indications, and contraindications. After the "Endler-era", significant differences are not noted between the groups of cemented, hybrid, and cement-less implants that impact on the clinical results and loosening rates.

Authors:

Astrid R.M. Krückhans, M.D., Ph.D., Assistant Medical Director, - Department Of Orthopaedic Surgery, Munich, Germany, Hans-Otto Dustmann, M.D., Ph.D., Professor of Orthopaedic Surgery, - Engelskirchen/Cologne, Germany

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Abstract:

All lines of development in Computer Aided Orthopaedic Surgery (CAOS) can be seen as critical steps in a broader effort to innovate the orthopaedic field. CAOS addresses the need to perfect implant placement and joint alignment. Minimally invasive techniques represent equally important new developments in the field of arthroplasty. It seems inevitable that these two fields converge. A navigation system for a minimally invasive approach to the hip would follow these primary design concepts :

Authors:

Michael Nogler, M.D., M.A., Msc. - Medical University of Innsbruck, Innsbruck, Austria

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Abstract:

Every year, approximately 2 million people experience a deep venous thrombosis (DVT). Approximately 600,000 of these people are diagnosed with a pulmonary embolism and about 10% of these die. It has been established that surgery, anesthesia, and bed rest increase the risk of DVT, and therefore, patients who undergo a major lower-extremity procedure should receive prophylaxis. During the past 10 years, the choices of pharmacological and mechanical prophylaxis have increased greatly. Warfarin is probably the most widely used prophylactic method in the U.S., but low-molecular-weight heparin (LMWH) use has increased. Also available is a synthetic pentasaccharide that acts as an anti-Xa inhibitor to decrease DVT without increase in bleeding. All but warfarin are given by subcutaneous injection and require no laboratory management to adjust the medication. Another drug in clinical trials is a direct thrombin inhibitor taken orally in a fixed dose that does not require monitoring. Non-pharmacological prophylaxis and/or stacked modalities, although used, have not shown the efficacy of pharmacological prophylaxis. With the incidence of DVT reported in the range of 41% to 85% without prophylaxis in joint replacement and hip-fracture surgery, prophylaxis is warranted in all lower-extremity joint replacement and hip-fracture patients.

Authors:

Mary E. Hardwick, R.N., M.S.N. - Research Publications; Clifford W. Colwell, Jr., M.D., Scripps Clinic Center for Orthopaedic Research and Education, La Jolla, California

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Abstract:

The operative treatment of bone fractures using plates and screws is a standard successful technique. Internal fixation with plates and screws leads to additional trauma and disturbance of the bone blood supply, which increases the risk of delayed union and infection. However, problems also are encountered in the fixation of osteoporotic bone. The locked internal fixator technique is an approach to optimize internal fixation. It aims at flexible elastic fixation to imitate spontaneous healing, including induction of callus formation. The technology supports what is currently called "minimally invasive plate osteosynthesis" (MIPO), which provides priority to biology over mechanics. An implant system called "Locking Compression Plate (LCP)" was developed, based on many years of experience with compression plating and good clinical results obtained with internal fixators, such as the Less Invasive Stabilization Systems (LISS). It combines the two treatment methods (ie, the compression plating and locked internal fixation methods) into one system. This chapter describes the basic principles of locked internal fixators and some clinical results with the LISS and LCP systems to illustrate the potential of these new systems.

Authors:

Professor Michael Wagner - Clinic for Trauma and Sportmedicine, Wilhelminenspital, Vienna, Austria; Andre Frenk, Ph.D. - Business Unit Trauma, Mathys Medical, Ltd., Bettlach, Switzerland; Röbi Frigg - Mathys Medical, Ltd., Bettlach, Switzerland

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Abstract:

Viscosupplementation is a therapeutic modality based on the replacement of synovial fluid or exudates with an elastoviscous hyaluronan solution. The first clinical trials were carried out on race horses with painful osteoarthritis of traumatic origin. In the early 1970s, the clinical trials were extended to painful osteoarthritis in humans. Analgesic effects lasting longer than the residence time of the injected hyaluronan in joints were reported both in horses and humans. The hyaluronan used was a noninflammatory fraction of the molecule with an average molecular weight of 2-3 million at a 1% concentration. The analgesic effect of this elastoviscous hyaluronan solution was demonstrated in behavioral animal pain models. Later it was shown that the elastoviscous properties of hyaluronan solutions are the determining factors in reducing pain-elicited nerve activity in both normal and inflamed cat and rat joints. It also was demonstrated in animal arthritis models that elastoviscous hyaluronan solutions promote the healing of traumatic intra-articular wounds. From the mid-1980s, several hyaluronan preparations of greatly varying average molecular weight but with the same concentration were introduced as viscosupplementation-based therapeutic agents. The elastoviscous properties of these solutions varied also, because of the greatly varying average molecular weights (0.5-6.0 million), imitating the rheological properties of either healthy or pathological synovial fluid. Currently, viscosupplementation products available worldwide vary greatly in their elastoviscous properties, and their dosage is not standardized in terms of frequency of injections required or in regard to the removal of exudates before injection. The question of which patient at what stage of the disease responds best with long-lasting pain relief to the many therapeutic products marketed with greatly varying elastoviscous properties has not yet been answered. At the same time, viscosupplementation was introduced, the same highly elastoviscous hyaluronan solutions also were applied in ophthalmic surgery as viscosurgical tools to protect sensitive tissues in the eye during surgery and to be used as soft instruments for tissue manipulation. Modified hyaluronan products (gels) also were introduced for augmentation of the intercellular matrix in tissues (viscoaugmentation) and for separating tissues to prevent adhesions and excessive scar formation (viscoseparation). Hyaluronan and its derivatives (gels) also have been used for drug delivery. The therapeutic use of highly elastoviscous solutions and gels of hyaluronan and its derivatives to build intercellular matrices for supplementation, regeneration, and developing new tissues introduced the concept of matrix engineering into medical practice.

Authors:

Endre A. Balazs, M.D. - College of Physicians and Surgeons, Columbia University, New York, Matrix Biology Institute, Ridgefield, New Jersey

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