Introduction. This study was undertaken to evaluate the early results of a new implant system - the
Aim. One of the most challenging problems in total knee arthroplasty (TKA) is periprosthetic infection. A major problem that arises in septic revision TKA (RTKA) are extended bone defects. In case of extended bone defects revision prostheses with
There is no mathematical relationship between the internal diameter of the femoral metaphysis and diaphysis. Unless an infinite number of monolithic stems are available with variable metaphyseal and diaphyseal diameters, which is not economically possible, even in virgin cases, the surgeon has to decide if the stem is going to fit in the metaphysis or the diaphysis. It is not possible to match both. In revision cases with a hollowed out metaphysis, the situation is much worse. As it is obviously easier to fit the diaphysis, this is what stems such as the AML and Wagner stem have done. They completely ignore the metaphysis and obtain fixation in the diaphysis. This is all well and good, but it means that the proximal femur is unloaded, like an astronaut in space. While, there will be some recovery due to removal of the toxins and local muscle pull, it will be incomplete. Furthermore, should sepsis occur, one is faced with the horror of removing a distally fixed implant. Clearly, if proximal fixation, i.e. above the level of lesser trochanter could reliably be achieved, this would be preferable in terms of proximal loading leading to bone recovery and ease of removal should it be required. The only way that proximal loading can be achieved is if the metaphyseal and diaphyseal parts of the component can be varied infinitely. This clearly can only be achieved by using a modular stem. The concern with modularity always has been fretting at the sleeve-stem locking mechanism with release of metal ions. The stem, which I have been using for the last 25 years, is the SROM stem. Fretting and ion release had never been an issue. As the components are made of a relatively soft titanium alloy, it is likely that the sleeve and the stem cold weld, thus, eliminating any movement and eliminating friction. I have a follow-up of roughly 120 revision cases with a minimum follow-up of 5 years and a maximum follow-up of 22 years. I have no loosening in easy revision cases where a primary stem was used. I have had some loosenings in extremely difficult revision situations where a long bowed stem was required, but even then, the loosening rate is less than 3%. I use this stem in primary situations, i.e. in about 80% of all the primaries I have done. This means I have done roughly 1500 cases or more. Other than some late infections, I have never, ever had any stem loosening in a simple case. Obviously, I have had loosenings in some cases, where we have been doing fancy shortening or de-rotation osteotomies, but none in simple primary cases. I would, therefore, suggest that the surgeon, if he wishes to use this stem, please try it out on some simple primary cases. The ability to vary distal and proximal internal diameters and proximal geometry makes for easy surgery. I have been using this stem for 25 years and continue to use it in all my primary noncemented cases. I believe in the adage of “train hard and fight easy.” I think that surgeons should not get themselves into a situation where they are forced in a difficult case to use something they have never seen before.
The femur begins to bow anteriorly at the 200 mm level, but may bow earlier in smaller people. If the stem to be used is less than 200 mm, a straight stem can be used. If the stem is longer than 200 mm, it will perforate the anterior femoral cortex. I know this because I did this on a few occasions more than 20 years ago. To use a long straight stem, there are two techniques. One can either do a diaphyseal osteotomy or one can do a Wagner split (extended trochanteric osteotomy). Both of these will put the knee in some degree of hyperextension, probably insignificant in the elderly, but it may be of significance in the young. In very young people, therefore, it may be preferable to use a bowed stem to avoid this degree of recurvatum. There are two different concepts of loading. Diaphyseal osteotomy implies a proximal loading has been sought. The Wagner split ignores the proximal femur and seeks conical fixation in the diaphysis. There will be very little bone-bone contact between what remains of the attached femur and the detached anterior cortex so that it is important to ensure that the blood supply to the anterior cortex remains intact, preferably by using Wagner's technique, using a quarter-inch osteotome inserted through the vastus to crack the medial cortex. Current modularity is of two types. Distal modularity was attempted many years ago and was never successful. Proximal modularity, as for example, the S-ROM stem, implies various sizes of sleeves fit onto the stem to get a proximal canal fill. In mid-stem modularity, the distal stem wedges into the cone. It has to be driven into where it jams and this can be somewhat unpredictable. For this reason, the solid Wagner stem has been replaced by the mid-stem modular. Once the distal femur is solidly embedded, the proximal body is then selected for height and version. The proximal body is unsupported in the mid-stem modular and initially, few fractures were noted at the taper junction. Cold rolling, shot peening and taper strengthening seem to have solved these problems. There are a variety of types of osteotomy, which can be used for different deformities. With a mid-stem modular system, generally, all that needs to be done is a Wagner-type split and fixation is sought in the mid-diaphysis by conical reaming. No matter what stem is used, distal stability is necessary. This is achieved by flutes, which engage the endosteal cortex. The flutes alone must have sufficient rotational stability to overcome the service loads on the hip of 22 Nm. I divide revision into three categories. In type one, the isthmus is intact, i.e. the bone below the lesser trochanter so that a primary stem can be used. In type two, the isthmus is damaged, i.e. the bone below the lesser trochanter, so a long revision stem is required. In a type three, there is more than 70 mm of missing proximal femur. The Wagner stem may be able to handle this on its own, but most other stems are better supported with a structural allograft cemented to the stem. The reported long term results of mid-stem modular revision implants are good as in most, over 90% survivorship. The introduction of modularity appears to have overcome initial disadvantage of the Wagner stem, i.e. its unpredictability in terms of leg length.
Aim. Bone loss is a severe problem in septic revision total knee arthroplasty (RTKA). The use of porous coated
Introduction. Revision TKA can be a difficult and complex procedure. Bone quality is commonly compromised and stem fixation is required in many cases to provide stability of the prosthetic construct. However, utilization of diaphyseal engaging stems adds complexity to the case and can present technical challenges to the surgeon. Press fit
Introduction. Fixation remains a challenge in Revision TKR. Irregular and cavitary bone loss may precludeproper metaphyseal cementation and pressurization.
Introduction:. Non-cemented, porous-coated
Three basic design concepts of cementless femoral fixation have emerged. They include: anatomic designs, straight stem designs, and tapered designs. In addition, there have been modular designs. The most successful have been designs that have a
The management of bone loss in revision total knee replacement (TKA) remains a challenge. To accomplish the goals of revision TKA, the surgeon needs to choose the appropriate implant design to “fix the problem,” achieve proper component placement and alignment, and obtain robust short- and long-term fixation. Proper identification and classification of the extent of bone loss and deformity will aid in preoperative planning. Extensive bone loss may be due to progressive osteolysis (a mechanism of failure), or as a result of intraoperative component removal. The Anderson Orthopaedic Research Institute (AORI) is a useful classification system that individually describes femoral and tibial defects by the appearance, severity, and location of bone defects. This system provides a guideline to treatment and enables preoperative planning on radiographs. In Type 1 defects, femoral and tibial defects are characterised by minor contained deficiencies at the bone-implant interface. Metaphyseal bone is intact and the integrity of the joint line is not compromised. In this scenario, the best reconstruction option is to increase the thickness of bone resection and to fill the defect with cancellous bone graft or cement. Type 2 defects are characterised by deficient metaphyseal bone involving one or more femoral condyle(s) or tibial plateau(s). The peripheral rim of cortical bone may be intact or partially compromised, and the joint line is abnormal. Reconstruction options for a Type 2A defect include impaction bone grafting, cement, or more commonly, prosthetic augmentation (e.g. sleeves, augments or wedges). In Type 2B defects, metaphyseal bone of both femoral condyles or both tibial plateaus is deficient. The peripheral rim of cortical bone may be intact or partially compromised, and the joint line is abnormal. Options for a Type 2B defect include impaction grafting, bulk structural allograft, prosthetic augmentation,
Purpose. Traditional total knee arthoplasty techniques have involved implantation of diaphyseal stems to aid in fixation expecially when using constrained polyethylene inserts. While the debate over cemented vs uncemented stems continues, the actual use of stems is considered routine. The authors' experience with cemented stemmed knee revisions in older patients with osteoporotic bone has been favorable. Our younger patients with press-fit stems from varying manufacturers have been plagued with a relatively high incidence of component loosening and stem tip pain in the tibia and occasionally thigh. We report the early results of the first 20 total knee revisions using press-fit
Introduction. Bone loss in the distal femur and proximal tibia is frequently encountered with both complex primary and revision knee replacement surgery.
INTRODUCTION:. Modular femoral stems of Total Hip Arthroplasty (THA) have been designed to fit the metaphysis and diaphysis separately. Clinical results with modular femoral stems are reported to be satisfactory, but there exists several concerns with modular implant connections, including fretting corrosion, fracture of implant, and dissociation the stem from the proximal sleeve. Recently, we have become aware of another potential consequence of the modular design: sleeve deformation secondary to forces encountered during insertion. In our patients, we noted that the stems would not fully seat in the machined taper of the sleeve, indicating that some type deformation to the sleeve had occurred. We began an in vivo study to characterize this phenomenon. The objectives of this study were (1) Does deformation occur by impacting the sleeve into the metaphysis? (2) If so, quantify the sleeve deformation in hip arthroplasty patients. MATERIALS AND METHODS:. One man and 7 women undergoing primary THA were enrolled. This project was approved by IRB. This modular system (4-U CLS; Nakashima Medical Co., Japan) consists of a