This video presentation serves to illustrate the pertinent aspects of bone preparation and implant insertion in cementless total knee arthroplasty (TKA) utilizing porous tantalum as a fixation surface integral to the success of the procedure.

The patient is typical of the surgical candidate frequently encountered for arthroplasty—a 60-year-old female with three compartment osteoarthritis of the knee, and manifesting a 10-degree varus deformity and 5-degree flexion contracture. She is a limited community ambulator without the use of support.

A standard surgical exposure is utilised and the bone preparation is identical to that used in the fixation of cemented implants—no alignment guides, cutting guides, or referencing instrumentation is used that is unique in the femoral or tibial bone preparation. The principal difference is in the patellar preparation. Instrumentation unique to the cementless porous tantalum patella is utilised in order to achieve three goals: a composite implant/residual bone thickness that replicates the thickness of the native patella, the generation of a planar patellar resection that is parallel to the anterior cut of the femur, and secure initial stability of fixation.

Keys to the initial fixation of the porous tantalum tibial and patellar components include the high surface friction of the material against bone, as well as the interference between the hexagonal pegs of each implant within the fixation holes (which are dimensionally smaller in diameter than the major and minor dimensions of the peg geometry). Care must be instituted to ensure that no bone or soft tissue debris is interposed at the mating surfaces of the implants that would compromise interface contact, and to carefully suction the peg holes to ensure that no debris impedes the complete seating of the pegs and the prosthesis. Lastly, all mating surfaces at the implant/bone interface must approach each other in a parallel fashion to optimise contact between the fixation surfaces and the bone resection surfaces.

The procedure is simply, easily performed, and is time saving. Total elapsed time for insertion of all three TKA implants in this video is 90 seconds.

Over the past 30 years, cemented, cementless, and hybrid fixation options have been utilised with various total knee arthroplasty (TKA) implant systems. While cemented components are widely used and considered the most reliable method of fixation, historical results may not be applicable to contemporary patients, who are increasingly younger than 65 years of age. Moreover, the literature is not definitive on which method of TKA fixation obtains the best clinical, functional, and radiographic results. A recent Cochrane meta-analysis on roentgen stereophotogrammetric analysis (RSA) included five randomised clinical trials (RCTs) in 297 participants. The authors observed that cemented fixation of tibial components demonstrated smaller displacement in relation to cementless fixation. However, the risk of future aseptic loosening with uncemented fixation was approximately half that of cemented fixation (risk ratio = 0.47, 95% CI 0.24 to 0.92) with a 16% absolute risk difference between groups. Almost all included studies recorded functional measures of Knee Society and Hospital for Special Surgery knee scores, but the authors of each study found no significant difference between the groups. Recently, highly porous metals have become an attractive fixation option in TKA due to their biomechanical properties. In a large RCT of 397 patients, Pulido et al found that uncemented highly porous metal tibias provided comparably durable fixation and reliable pain relief and restoration of function when compared with traditional cemented modular tibias. While longer term studies are needed, cementless TKAs may be a durable and reliable alternative with highly porous metals, particularly in younger patients

Over the past 30 years, cemented, cementless, and hybrid fixation options have been utilised with various total knee arthroplasty (TKA) implant systems. While cemented components are widely used and considered the most reliable method of fixation, historical results may not be applicable to contemporary patients, who are increasingly younger than 65 years of age. Moreover, the literature is not definitive on which method of TKA fixation obtains the best clinical, functional, and radiographic results. A recent Cochrane meta-analysis on roentgen stereophotogrammetric analysis (RSA) included five randomised clinical trials (RCTs) in 297 participants. The authors observed that cemented fixation of tibial components demonstrated smaller displacement in relation to cementless fixation. However, the risk of future aseptic loosening with uncemented fixation was approximately half that of cemented fixation (risk ratio = 0.47, 95% CI 0.24 to 0.92) with a 16% absolute risk difference between groups. Almost all included studies recorded functional measures of Knee Society and Hospital for Special Surgery knee scores, but the authors of each study found no significant difference between the groups. Recently, highly porous metals have become an attractive fixation option in TKA due to their biomechanical properties. In a large RCT of 397 patients, Pulido et al found that uncemented highly porous metal tibias provided comparably durable fixation and reliable pain relief and restoration of function when compared with traditional cemented modular tibias. While longer-term studies are needed, cementless TKAs may be a durable and reliable alternative with highly porous metals, particularly in younger patients

Critical review of the literature fails to make a convincing case for use of cement in TKA. Many studies demonstrate clinical, mechanical, and biological failure when cement is used for fixation. Work by Ryd et al. has shown that initial migration within the first few months diminished rapidly after the first 6 months with virtually no additional movement for years after. They also suggested that cemented components do not remain rigidly fixed to bone long-term, but loosen enough to move 0.2 to 1 mm at the bone-cement interface with provocative testing. Although bone-ingrowth tibial components migrate slightly more initially than cemented ones do, they stabilise and do not sink progressively. Screw fixation adds rigidity, but does not seem to improve results. Rigidity of initial fixation is the most important feature after alignment to ensure pain-free function after arthroplasty, and can be achieved with press-fit techniques in TKA. Several early reports of bone-ingrowth TKA had inferior results because the tibial component had no stem, peg, or screw fixation, leading to implant migration and loosening. An effective stem has been shown to greatly improve tibial component fixation. The cut upper surface of the prepared tibia has areas that are too weak to withstand the forces that are applied to the surface, and failure in compression is likely unless fixation is augmented. An effective stem also reduces the shear and tensile loads at the bone-prosthesis interface. The effectiveness of compression or compaction of the tibial cancellous bone with an appropriately sized tibial metaphyseal stem has been shown, and probably was a major factor in the long-term success of fixation in our series. Clinical results of TKA with osteointegration techniques for fixation of the femoral and tibial components in our series are comparable with the best series reported with cemented fixation. Many recent studies show significant advantages of osteointegration over cement fixation in TKA. Fixation of implants with PMMA pressed into cancellous bone eventually loosens, and fixation of a metal component to bone cement also is tenuous in most cases. Cement is disappearing rapidly from use in total hip, ankle, and shoulder arthroplasty, and soon will be replaced with osteointegration technique in the knee. Perhaps the most appealing aspect of bone-ingrowth TKA is bone preservation. The ease of revisability because of good bone was encouraging in the components that wore, loosened, or became infected in the current series of TKA. These knees are functioning as well as knees with primary TKA. Should these knees develop additional problems, progressive destruction of bone is unlikely to occur, even if repeated revision is necessary

Introduction. Restoration of a neutral mechanical axis has been a widely held tenet of primary total knee arthroplasty (TKA), however new technologies are recently being marketed which claim correction of alignment deformity is unimportant. This study was undertaken to determine whether the outcome of aseptic loosening was associated with post-operative mal-alignment of the mechanical axis. Methods. A 1:9 matched case-control analysis was conducted within a cohort of 1,030 consecutive cemented posterior stabilized TKAs with 7 to 11.5 yrs follow-up (average 9 yrs). Aseptic loosening had occurred in 10 knees (1.0%). Nine controls were randomly selected for each case within matching criteria for age and minimum time in situ. Post-operative mechanical alignment was determined using retrieved long leg radiographs. Age-adjusted relative risk was estimated using conditional logistic regression. Results. Radiographs revealed 8 of the 10 loosened cases had been placed in 3 or more degrees varus mechanical alignment (range, 2? varus to 7? varus), compared to only 4 of the 90 age-matched controls (range, 4? valgus to 4? varus). A single degree change of mechanical alignment in the varus direction was associated with a more than 4-fold increase of risk of loosening (odds ratio 4.6, 95% confidence interval 1.7–12.7; p=0.0035). The relative risk for mechanical alignment >= 3? varus compared to <= 2? varus (dichotomous) was 69.2 (95% confidence interval 8.1–589; p=.0001). BMI, gender, and pre-op deformity were not significant. Discussion. These results suggest that avoidance of varus postoperative alignment is an extremely important determinant of TKA fixation durability

The initial application of bone ingrowth technology to the fixation of total knee arthroplasty (TKA) components without bone cement was based on the premise that bone cement was “not biologic”, and so over time would undergo fatigue failure with subsequent loosening. It was hoped that this problem could be obviated by cementless fixation by bone ingrowth, which would remodel over time and not fatigue. In addition, it was anticipated that the failed cementless TKA might be easier to revise and leave the surgeon with more bone to work with. Whether or not cementless fixation of TKA components was justified on any of these counts was uncertain through the first 2 decades of their use. Much of the data accumulated during that period poorly supported these contentions, while cemented TKA was increasingly reported as a reliable, consistent and less complicated form of TKA fixation. However, over the past decade, new evidence has accumulated demonstrating greater success with this technology in several well designed studies as well as from registry studies. Most of this evidence involves the use of Porous Tantalum. However, increasing evidence that loosening of well done, well designed cemented TKA is rare along with some evidence that a certain percentage of cementless TKA patients fail to achieve stability remains concerning. In addition, no studies have justified improved longevity to the extent that the increased cost of cementless devices can be justified

Over the past 30 years, cemented, cementless, and hybrid fixation options have been utilised with various total knee arthroplasty (TKA) implant systems. While cemented components are widely used and considered the most reliable method of fixation, historical results may not be applicable to contemporary patients, who are increasingly younger than 65 years of age. Moreover, the literature is not definitive on which method of TKA fixation obtains the best clinical, functional, and radiographic results. A recent Cochrane meta-analysis on roentgen stereophotogrammetric analysis (RSA) included five randomised clinical trials (RCTs) in 297 participants. The authors observed that cemented fixation of tibial components demonstrated smaller displacement in relation to cementless fixation. However, the risk of future aseptic loosening with uncemented fixation was approximately half that of cemented fixation (risk ratio = 0.47, 95% CI 0.24 to 0.92) with a 16% absolute risk difference between groups. Almost all included studies recorded functional measures of Knee Society and Hospital for Special Surgery knee scores, but the authors of each study found no significant difference between the groups. Recently, highly porous metals have become an attractive fixation option in TKA due to their biomechanical properties. In a large RCT of 397 patients, Pulido et al. found that uncemented highly porous metal tibias provided comparably durable fixation and reliable pain relief and restoration of function when compared with traditional cemented modular tibias. While longer-term studies are needed, cementless TKAs may be a durable and reliable alternative with highly porous metals, particularly in younger patients

Two big problems exist with the all-polyethylene cemented tibial component—the polyethylene and the cement. The polyethylene is too weak and flexible to bear tibial load, so it deforms and loosens. Isoelastic material has never worked, and it never will. The interface stresses are too high when two flexible structures are poorly bonded and heavily loaded. Critical review of the literature fails to make a convincing case for use of cement in TKA. Many studies demonstrate clinical, mechanical, and biological failure when cement is used for fixation. Work by Ryd et al. has shown that initial migration within the first few months diminished rapidly after the first 6 months with virtually no additional movement for years after. They also found that cemented components do not remain rigidly fixed to bone long-term, but loosen enough to move 0.2 to 2.1 mm at the bone-cement interface with provocative testing. Although bone-ingrowth tibial components migrate slightly more initially than cemented ones do, they stabilise and do not sink progressively. Screw fixation adds rigidity, but does not seem to improve results. Rigidity of initial fixation is the most important feature after alignment to ensure pain-free function after arthroplasty, and can be achieved with press-fit techniques in TKA. Several early reports of bone-ingrowth TKA had inferior results because the tibial component had no stem, peg, or screw fixation, leading to implant migration and loosening. An effective stem has been shown to greatly improve tibial component fixation. The cut upper surface of the prepared tibia has areas that are too weak to withstand the forces that are applied to the surface, and failure in compression is likely unless fixation is augmented. An effective stem also reduces the shear and tensile loads at the bone-prosthesis interface. The effectiveness of compression or compaction of the tibial cancellous bone with an appropriately sized tibial metaphyseal stem has been shown, and probably was a major factor in the long-term success of fixation in our series. Clinical results of TKA with osteointegration techniques for fixation of the femoral and tibial components in our series are comparable with the best series reported with cemented fixation. Many recent studies show significant advantages of osteointegration over cement fixation in TKA. Fixation of implants with PMMA pressed into cancellous bone eventually loosens, and fixation of a metal component to bone cement also is tenuous in most cases. Cement is disappearing rapidly from use in total hip, ankle, and shoulder arthroplasty, and soon will be replaced with osteointegration technique in the knee. Perhaps the most appealing aspect of bone-ingrowth TKA is bone preservation. The ease of revisability because of good bone was encouraging in the components that wore, loosened, or became infected in the current series of TKA. These knees are functioning as well as knees with primary TKA. Should these knees develop additional problems, progressive destruction of bone is unlikely to occur, even if repeated revision is necessary

Limb deformity is common in patients presenting for knee arthroplasty, either related to asymmetrical wear patterns from the underlying arthritic process (intra-articular malalignment) or less often major extra-articular deformity due to prior fracture malunion, childhood physical injury, old osteotomy, or developmental or metabolic disorders such as Blount's disease or hypophosphatemic rickets. Angular deformity that is above the epicondyles or below the fibular neck may not be easily correctable by adjusted bone cuts as the amount of bone resection may make soft tissue balancing impossible or may disrupt completely the collateral ligament attachments. Development of a treatment plan begins with careful assessment of the malalignment which may be mainly coronal, sagittal, rotational or some combination. Translation can also complicate the reconstruction as this has effects directly on location of the mechanical axis. Most intra-articular deformities are due to the arthritic process alone, but may occasionally be the result of intra-articular fracture, periarticular osteotomy or from prior revision surgery effects. While intra-articular deformity can almost always be managed with adjusted bone cuts it is important to have available revision type implants to enhance fixation (stems) or increase constraint when ligament balancing or ligament laxity is a problem. Extra-articular deformities may be correctable with adjusted bone cuts and altered implant positioning when the deformity is smaller, or located a longer distance from the joint. The effect of a deformity is proportional to its distance from the joint. The closer the deformity is to the joint, the greater the impact the same degree angular deformity will have. In general deformities in the plane of knee are better tolerated than sagittal plane (varus/valgus) deformity. Careful pre-operative planning is required for cases with significant extra-articular deformity with a focus on location and plane of the apex of the deformity, identification of the mechanical axis location relative to the deformed limb, distance of the deformity from the joint, and determination of the intra-articular effect on bone cuts and implant position absent osteotomy. In the course of pre-operative planning, osteotomy is suggested when there is inability to correct the mechanical axis to neutral without excessive bone cuts which compromise ligament or patellar tendon attachment sites, or alternatively when adequate adjustment of cuts will likely lead to excessive joint line obliquity which can compromise ability to balance the soft tissues. When chosen, adjunctive osteotomy can be done in one-stage at the time of TKA or the procedures can be done separately in two stages. When simultaneous with TKA, osteotomy fixation options include long stems added to the femoral (or tibial) component for intramedullary fixation, adjunctive plate and screw fixation, and antegrade (usually locked) nailing for some femoral osteotomies. Choice of fixation method is often influenced by specific deformity size location, bone quality and amount, and surgeon preference. Surgical navigation, or intra-operative x-ray imaging methods (or both) have both been used to facilitate accurate correction of deformity in these complex cases. When faced with major deformity of the femur or tibia, with careful planning combined osteotomy and TKA can result in excellent outcomes and durable implant fixation with less constraint, less bone loss, and better joint kinematics than is possible with modified TKA alone

INTRODUCTION:. Aseptic loosening continues to be a short and long-term complication for patients with cemented knee replacements. Changes in cemented total knee replacement (TKR) fixation have been limited to assessment of radiographic changes at the implant-bone interface and quantification of component migration. The goal of this study was to determine the interlock morphology between cement and trabecular bone using en bloc postmortem retrieved TKR. Note that these retrievals were not obtained from revision surgery for a loose implant, but rather after death. Thus the implants can be considered successful for the lifetime of the patient. We hypothesized that constructs with greater time in service have less interlock between cement and bone and constructs with more estimated initial interlock sustain more interlock with in-vivo service. METHODS:. Twelve retrieved tibial components and two lab-prepared constructs with time in service from 0 to 20 years were sectioned in the transverse plane in 10 mm increments, imaged at high resolution, and the current contact fraction (curCF), estimated initial interdigation depth (inID), current interdigitation depth (curID), and loss of interdigitation depth (lossID) were quantified at the cement-bone interface. Contact fraction was determined using a stereology method using random ray projections (Figure 1A). The trabecular shape cast into the cement layer upon curing was used to document the initial penetration of bone into the cement. A line tracing algorithm was used to determine interdigiation depth (Figure 1B). RESULTS:. There was no biological resorption for the lab prepared constructs (Figure 2A-B). In contrast, a postmortem retrieval (5 years in service) illustrates trabecular resorption with some areas of bone remaining in the cement layer (Figure 2C-D). The curCF (r. 2. = 0.54, p = 0.0027) and curID (r. 2. = 0.33, p = 0.033) were lower for constructs with longer time in service (Figure 3). The lossID had a strong positive relationship with time in service (r. 2. = 0.74, p < 0.0001). Using a two-parameter regression model, constructs with more inID had higher curID (p = 0.011), but constructs with more time in service also had lower curID (p = 0.008). DISCUSSION:. The cement-trabecular bone interlock that is obtained initially appears to diminish with in-vivo service by resorption of the trabeculae within the cement interlock region. The resulting fixation for longer term constructs (>10 years) was limited, with cement-bone contact fractions of ∼7% and interdigitation depths of ∼0.4 mm. This appears to be sufficient to support load transfer between the metal tray and proximal tibia, as these retrievals were from radiographically well fixed components. The work here supports the surgical concept of obtaining sufficient initial cement interlock (∼3 mm), with the acknowledgement that there will be loss of interlock with in-vivo service. It is possible that loss of interlock contributes to the loosening process of cemented TKR. Further work is needed to understand how loss of interlock affects interface strength