Lower rates of radiolucency with a hybrid all-polyethylene pegged glenoid component compared to a completely cemented pegged glenoid component

BackgroundThe purpose of this study was to compare the functional outcome and radiographic appearance of total shoulder arthroplasties (TSAs) performed with an entirely cemented all-polyethylene glenoid to a hybrid all-polyethylene glenoid designed for hybrid fixation with peripheral cement and central osseous integration. The hypothesis was that there would be no difference in functional outcome or radiographic appearance between the two components at two year follow-up.MethodsA multicenter retrospective comparative study was conducted on primary TSAs performed with a press-fit humeral stem and an entirely cemented or hybrid all-polyethylene glenoid from 2015–2017. Functional outcomes and radiographic appearance of the glenoid based on the Lazarus and Churchill classifications were reviewed at a minimum of 2 years postoperatively.Results96 patients were included in the study; 62 with a hybrid all-polyethylene glenoid and 34 with an entirely cemented pegged glenoid. The mean Lazarus score was 1.03 in the cemented group compared to 0.60 in the hybrid group (p = 0.032). The mean Churchill score in the hybrid group was 0.47, which was also significantly lower than the cemented group Lazarus score (p = 0.006). There were no statistically significant differences in 2-year functional outcomes, range of motion, complications, or revision between the two groups.ConclusionA hybrid all-polyethylene glenoid for TSA results in lower radiolucencies scores at 2 years postoperatively compared to an entirely cemented, pegged component. There were no differences in functional outcome scores or range of motion between patients with the two glenoid types at 2 years.Level of evidenceLevel III; Retrospective Comparative Study.     

The emerging role of the non-cemented glenoid in total shoulder arthroplasty

In an effort to address the relatively high rate of glenoid component lucent lines, loosening and failure, tantalum/trabecular metal glenoid implant fixation has evolved as it has in hip and knee arthroplasty. Trabecular metal-anchored glenoid implants used in this consecutive patient case series has demonstrated a lower failure rate than traditional all-polyethylene cemented glenoids. Although the radiographs of some patients demonstrated small focal areas of lucency, none have become loose, and only one has actually demonstrated glenoid component failure due to a fracture 6 years after the index procedure. One with glenoid loosening was due to poly wear from a massive cuff tear occurring 8 years after the index procedure. Most patients experienced significant improvements in shoulder range of motion and reduction in pain. Trabecular metal glenoids when carefully implanted do not produce excessive failure rates, but rather result in functional improvements while decreasing operative time.     

Radiographic analysis of polyethylene glenoid components using modern cementing techniques

The purpose of this study was to examine the initial radiographic appearance and changes occurring over time in patients who have undergone total shoulder arthroplasty by modern methods of bone preparation and current cement techniques. Sixty-five patients underwent seventy total shoulder arthroplasties by use of a cemented all-polyethylene, keeled glenoid component. The surface radius was equal to the radius of a one-piece humeral component. The mean clinical follow-up was 4.18 years (range, 2-8.6 years); radiographic follow-up averaged 3.9 years (range, 2-8.6 years). Three observers evaluated radiographs 1 to 2 months postoperatively and at final follow-up. The glenoid component was considered at risk for clinical problems if there was a complete lucent line surrounding the component and some part of the line was 1.5 mm or greater in width or two of three or all three observers identified a shift in component position. Similarly, a humeral component was judged to be at risk if three or more zones had lucent lines 2 mm or greater in width or a shift in component position had occurred. On the early radiographs, 10 glenoid components had incomplete lucencies behind the keel. On the most recent radiographs, 59 glenoid components had incomplete lucent lines and 3 had complete lucent lines. Eight components were judged to have shifted in position. When data for lucent lines and shifting were combined, 10 (14%) of the glenoid components were at risk. At follow-up, no cemented humeral components were at risk whereas 3 (6%) of the 54 tissue ingrowth components were at risk for clinical loosening. Given the number of shoulders in this study, there were no associations between radiographic changes and clinical results. Improvements have occurred in glenoid component fixation. However, additional advances are possible and may occur from improved surgical technique, decreased particle-related osteolysis, enhanced joint kinematics, or novel fixation methods.     

Cemented polyethylene versus uncemented metal-backed glenoid components in total shoulder arthroplasty: a prospective,double-blind,randomized study

Thirty-nine patients (forty shoulders) with primary osteoarthritis consented to be randomized to receive either a cemented all-polyethylene glenoid component or a cementless metal-backed component at the time of total shoulder arthroplasty. Their mean age was 69 years. Preoperative and postoperative evaluations were completed at 3, 6, 12, 24, and 36 months by history, physical examination, radiographs, and Constant scoring system. The presence of periprosthetic radiolucent lines was significantly greater with polyethylene than with metal-backed glenoids (85% vs 25%, P <.01). Of 20 radiolucent lines, 12 (60%) around polyethylene glenoids were present on immediate postoperative radiographs and 25% were progressive. No significant correlation was found between the presence of radiolucent lines around polyethylene glenoids and functional results (P =.3). By contrast, periprosthetic radiolucent lines around metal-backed glenoids were rare but progressive when present. The incidence of loosening of metal-backed implants (4 cases, 20%) was significantly higher than that observed with polyethylene glenoids (0%, P <.001) and was associated with component shift and severe osteolysis. Metal-backed glenoid loosening significantly correlated with deteriorating functional results and increasing pain (P <.05). Revision surgery was required for 4 patients in the metal-backed group (P =.02), for a subscapularis tear (1 case) and metal-backed glenoid component loosening (3 cases). Computed tomography scan analysis and revision surgery revealed that preoperative posterior humeral subluxation may recur with time despite glenoid reorientation and may cause asymmetric accelerated polyethylene wear, resulting in metal-on-metal contact and severe osteolysis. Reimplantation of a stable cemented glenoid component was possible in 1 case, whereas the cavitary defect was packed with cancellous bone in the 2 other cases. At a minimum of 3 years' follow-up, the results of this study clearly show that (1) the survival rate of cementless, metal-backed glenoid components is inferior to cemented all-polyethylene components and (2) the incidence of radiolucency at the glenoid-cement interface with all-polyethylene components is high and remains a concern. The high rate of loosening, because of the absence of ingrowth and/or the accelerated polyethylene wear, has led us to abandon the use of metal-backed glenoids. Efforts must continue to improve glenoid component design and fixation.     

Mid-term results of a metal-backed glenoid component in total shoulder replacement

Total shoulder replacement is a successful procedure for degenerative or some inflammatory diseases of the shoulder. However, fixation of the glenoid seems to be the main weakness with a high rate of loosening. The results using all-polyethylene components have been better than those using metal-backed components. We describe our experience with 35 consecutive total shoulder replacements using a new metal-backed glenoid component with a mean follow-up of 75.4 months (48 to 154). Our implant differs from others because of its mechanism of fixation. It has a convex metal-backed bone interface and the main stabilising factor is a large hollow central peg. The patients were evaluated with standard radiographs and with the Constant Score, the Simple Shoulder Test and a visual analogue scale. All the scores improved and there was no loosening, no polyethylene-glenoid disassembly and no other implant-related complications. We conclude that a metal-backed glenoid component is a good option in total shoulder replacement with no worse results than of those using a cemented all-polyethylene prosthesis.     

All-polyethylene vs. metal-backed tibial component in total knee arthroplasty—a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: Part 2. Completely cemented components: MB not superior to AP components

Background?Uncertainty exists as to whether metal backing (MB) of the tibial component is better than an all-polyethylene component (AP). This is valid for both horizontally and completely cemented components. We evaluated completely cemented MB vs. AP (Part 2).

Patients and methods?In a randomized study, 39 patients (40 knees) with knee arthrosis were operated with cemented low-conforming total knee arthroplasty (AGC, Biomet) with a tibial component of uniform thickness (8?mm), cemented both beneath the tibial tray and around the stem. 20 patients had an all-polyethylene (AP) tibial component and 20 patients had an identical but metal-backed (MB) tibial component. We used clinical examination and radiostereometric analysis (RSA) to evaluate the hypothesis that MB improves component fixation. Fixation was evaluated using RSA up to 2 years after surgery. Clinical assessment was performed preoperatively and after 2 years using the Hospital for Special Surgeons (HSS) score.

Results?We found no differences in micromotion, and no differences in clinical scores could be detected between the groups at any time point.

Interpretation?Our findings indicate that there was equal initial fixation of the AP and MB stemmed monobloc components when they were cemented beneath the tibial plateau and around the stem.

?     

All-polyethylene vs. metal-backed tibial component in total knee arthroplasty-a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: part 2. Completely cemented components: MB not superior to AP components

Background Uncertainty exists as to whether metal backing (MB) of the tibial component is better than an all-polyethylene component (AP). This is valid for both horizontally and completely cemented components. We evaluated completely cemented MB vs. AP (Part 2).

Patients and methods In a randomized study, 39 patients (40 knees) with knee arthrosis were operated with cemented low-conforming total knee arthroplasty (AGC, Biomet) with a tibial component of uniform thickness (8 mm), cemented both beneath the tibial tray and around the stem. 20 patients had an all-polyethylene (AP) tibial component and 20 patients had an identical but metal-backed (MB) tibial component. We used clinical examination and radiostereometric analysis (RSA) to evaluate the hypothesis that MB improves component fixation. Fixation was evaluated using RSA up to 2 years after surgery. Clinical assessment was performed preoperatively and after 2 years using the Hospital for Special Surgeons (HSS) score.

Results We found no differences in micromotion, and no differences in clinical scores could be detected between the groups at any time point.

Interpretation Our findings indicate that there was equal initial fixation of the AP and MB stemmed monobloc components when they were cemented beneath the tibial plateau and around the stem.

  ▪     

Press-fit versus cemented all-polyethylene patellar component: midterm results.

This study compared the midterm results between press-fit and cemented implantation of a highly congruent, all-polyethylene patellar component. We followed prospectively 172 implants (cemented, n = 133; press-fit, n = 39). Average follow up was 6 years (range, 5-8 years). Patellofemoral complications occurred in 4 cemented patellae (2.3%). Two of these patellae required revision. Cemented implants had a significantly higher incidence of patellar maltracking (30% vs 8%; P= .005). No significant differences in the overall Knee Society scores (mean, 165; SD, 27) or any of its components relevant to patellofemoral function were detected between fixation methods. A retrieved specimen showed an intervening fibrous membrane at the implant-bone interface. The potential for macrophage-mediated osteolysis at this site is unknown. No other adverse outcome was associated with press-fit implantation. These results suggest that at midterm follow-up, press-fit implantation of this all-polyethylene patellar component may improve tracking and represents a viable alternative to cement fixation.     

Stress analyses of glenoid components in total shoulder arthroplasty

Finite element analysis was used to characterize the local stresses at the bone-implant interface of 2 different types of glenoid components presently used in unconstrained total shoulder arthroplasty. A series of 2-dimensional finite-element meshes was developed to model the glenoid in 2 mutually perpendicular planes with and without implanted components. One of the implants modeled was a cemented all-polyethylene component, and the second was an uncemented metal-backed component. A variety of parameters were studied including the resultant loading direction (concentric versus eccentric), keel geometry, subchondral bone integrity, and cement mantle size. Results of the analyses show that the cemented all-polyethylene design demonstrated an overall stress pattern that was closer to that of the intact glenoid. When the effects of concentric and eccentric loading conditions were compared, the overall stress magnitudes in the subchondral bone were found to be much lower with the uncemented metal-backed component than with its cemented all-polyethylene counterpart. This finding suggests that some degree of stress shielding may be associated with the metal-backed component. In addition, under both the concentric and eccentric loading conditions, extremely high stress regions were found within the polyethylene near the polyethylene-metal interface of the uncemented metal-backed component.     

An innovative method of fracture reduction in an arthroscopically assisted cannulated screw fixation of an Ideberg type III glenoid fracture

Significantly displaced intra-articular glenoid fractures treated nonoperatively have been found to have poor functional outcomes. For this reason, most are treated with open reduction and internal fixation. Conventional open techniques involve extensive exposure and soft tissue dissection. Moreover, visualization of the fracture and its reduction can also be difficult even with standard open techniques. We present a case of an Ideberg type III glenoid fracture treated with an arthroscopically assisted percutaneous screw fixation, using the coracoid as a reduction aide. This reduction technique is not previously reported in the literature. Arthroscopically assisted percutaneous glenoid fixation has showed promising early results in the literature. In our case, the fracture united and the patient returned to all his normal daily activities by 7 weeks postoperatively. This suggests arthroscopically assisted glenoid fixation provides good functional and radiological outcomes, without the need for extensive soft tissue dissection.     

Hybrid Glenoid Designs in Anatomic Total Shoulder Arthroplasty: A Systematic Review

Background:Hybrid glenoid components in total shoulder arthroplasty (TSA) utilize both polyethylene and metal components to provide short-term stability and long-term biologic fixation through bone ingrowth.Questions/Purpose:We sought to systematically review the literature for studies that assessed outcomes of TSA performed using hybrid glenoid components.Methods:PubMed, Medline, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Embase were searched systematically for articles measuring clinical and patient-reported outcomes and rates of complication and revision following TSA using a hybrid glenoid component.Results:Seven studies with 593 shoulders were included in this review. The mean age of patients was 65 ± 1 years, and 46% of the population was male. Mean follow-up was 50 months (4.2 years). The overall complication rate was 7% and rate of revision was 2.5%; glenoid radiolucency was present in 33% of shoulders at mean follow-up of 50 months. Mean improvements in forward elevation, external rotation, internal rotation score, and abduction were 49°, 28°, 2 points, and 42°, respectively. Mean improvements in Constant, American Shoulder and Elbow Surgeons (ASES), and University of California, Los Angeles (UCLA) scores were 36 points, 52 points, and 17 points, respectively.Conclusion:Our review found that TSA using hybrid glenoid components results in low rates of complication and revision at early follow-up. Long-term studies are warranted to understand more fully the role of hybrid glenoid components in TSA.     

The influence of metal backing in unicompartmental tibial component fixation

Summary The fixation of the tibial component in 36 patients with conventionally cemented unicompartmental knee arthroplasties for femorotibial gonarthrosis was studied using roentgen stereophotogrammetric analysis (RSA). Twenty-four tibial components were all-polyethylene while 12 were metal-backed. The follow-up was for 6 years. Significant migration was detected for all cases but two and ranged from 0.3 mm to 5.4 mm. The greater part of the migration occurred during the first 1–2 years, after which two-thirds of the prostheses remained stable. Seven all-polyethylene components were subjected to a stress examination after 1–2 years and displacement, induced by external forces, was found in all seven. A strong correlation was found between the extension of the radiolucent line and the migration. Otherwise, neither demographic, clinical, nor radiographic data correlated with the RSA results. In this study metal backing did not have any influence on prosthetic fixation as measured by RSA.This study was financially supported by Stiftelsen Bistånd åt Vanföra i Skåne, Alfred Österlunds Stiftelse, the Crawford Foundation, Konung Gustav V 80-årsfond, the Medical Faculty of Lund University and Medical Research Council 09509     

All-polyethylene vs. metal-backed tibial component in total knee arthroplasty—a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: Part 1. Horizontally cemented components: AP better fixated than MB

Background?Controversy still exists as to whether to mount the tibial bearing on a metal baseplate or not. Furthermore, the tibial component can be either horizontally or completely cemented. We evaluated metal backing versus all-polyethylene using horizontal cementing technique.

Patients and methods?We randomized 40 patients with knee arthrosis (40 knees) to 2 groups: cemented total knee arthroplasty (AGC, Biomet) using either all-polyethylene (AP) or metal-backed (MB) tibial compo-nents (n = 20 for each group). All tibial implants had a total thickness of 8?mm. We used proximal cement-ing, including only the horizontal part of the tibia with avoidance of the stem-bone interface.

Results?The positioning of the implants, as judged by the HKA angle, showed an average neutral alignment in both groups. Preoperatively and after 2 years, there was no statistically significant difference between the HSS scores in both groups (p = 0.6 and 0.4). After 2 years, the metal-backed components had rotated more around the longitudinal axis, median 0.5° vs. 0.2° (internal or exter-nal rotation, p = 0.002), and showed increased maximum total point motion, median 1.0 vs. 0.4?mm (maximum migration or MTPM, p = 0.003).

Interpretation?Our study indicates that better fixation can be obtained with the all-polyethylene design if proximally cemented thin components are used.

?     

CT scan evaluation of glenoid component fixation: a prospective study of 27 minimally cemented shoulder arthroplasties

Background

Glenoid component failure is the most common complication of total shoulder arthroplasty. It can be correlated with failure of the component itself to resist wear and deformation, failure of fixation or failure of the glenoid bone. Anchor Peg Glenoid component (Depuy^®) seems to have a higher bone fixation in biomechanical canine model: it is a all-polyethylene, concave component with one circumferentially fluted, central, interference-fit peg and three small cemented peripheral pegs.

Materials and methods

We realized a prospective study of Anchor Peg total shoulder arthroplasty, included 27 patients suffering from primary arthrosis or arthritis, without rotator cuff tear. A clinical and radiographic evaluation was performed at 3 months, 1 and 2 years; a CT scan was made in postoperative and analyzed central peg’s bone integration 1 year later.

Results

Improvement of postoperative Constant score and radiographic good results were correlated with satisfactory subjective results reported by patients. We observed radiolucent lines under glenoid component in 3 cases. Twenty-six CT scans were available at 1 year: it showed complete bone integration around the central peg in 21 cases and partial peripheral bone integration in four cases. Only one patient had any tissue integration around the peg, probably because of his implantation near cortical bone of scapular spine.

Discussion/conclusion

Long-term result of arthroplasty is correlated with glenoid durable fixation to underlying bone: this study shows higher fixation of glenoid component with bone integration of central peg. However, these results will have to be confirmed in a later revision.     

Total shoulder arthroplasty — current problems and possible solutions

The concept and design of a cemented unconstrained total shoulder arthroplasty (TSA), introduced by Charles Neer II 25 years ago, has been successful in the management of degenerative and inflammatory conditions of the shoulder, controlling pain and, in many patients, significantly improving function. The clinical outcome is very much determined by the nature and severity of the pathology, as well as by the surgeon's experience and ability to correctly locate and fix the components. Total shoulder arthroplasty is a technically difficult procedure with perhaps a greater potential for technical errors and complications compared with other commonly performed arthroplasties. Current systems are modular on the humeral side, with varying head diameters and neck lengths, allowing more accurate coverage of the cut surface of the humeral neck and improved ability to establish the position of the joint line within the requirements of correct soft tissue tension and balance. Cemented all-polyethylene glenoid components remain the most favored, but the majority now have an increased radius of curvature compared with their corresponding humeral head, to allow translation during movement. Aseptic glenoid component loosening is the most frequently encountered long-term complication and is hastened by conforming prostheses, incorrect positioning, rotator cuff tears, and capsular contractures, but is protected by secure glenoid fixation. Cemented one-piece metal-backed glenoids have been disappointing, but non-cemented glenoids are being trialed with promising early results, although they have introduced their own particular problems of rapid polyethylene wear and component dissociation. Although cemented humeral components have a very low incidence of symptomatic loosening, most surgeons currently use press-fit designs supplemented with metaphyseal porous coating for osseous integration. Based on increased understanding of the morphology of the upper humerus, current designs are evolving with increased modularity, allowing the surgeon to choose the appropriate size, inclination, offset and version of the humeral component. These changes will, it is hoped, result in improved functional recovery and increased survivorship of the glenoid component. Received for publication on April 15, 1998; accepted on July 31, 1998     

All-polyethylene vs. metal-backed tibial component in total knee arthroplasty-a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: part 1. Horizontally cemented components: AP better fixated than MB

Background Controversy still exists as to whether to mount the tibial bearing on a metal baseplate or not. Furthermore, the tibial component can be either horizontally or completely cemented. We evaluated metal backing versus all-polyethylene using horizontal cementing technique.

Patients and methods We randomized 40 patients with knee arthrosis (40 knees) to 2 groups: cemented total knee arthroplasty (AGC, Biomet) using either all-polyethylene (AP) or metal-backed (MB) tibial compo-nents (n = 20 for each group). All tibial implants had a total thickness of 8 mm. We used proximal cement-ing, including only the horizontal part of the tibia with avoidance of the stem-bone interface.

Results The positioning of the implants, as judged by the HKA angle, showed an average neutral alignment in both groups. Preoperatively and after 2 years, there was no statistically significant difference between the HSS scores in both groups (p = 0.6 and 0.4). After 2 years, the metal-backed components had rotated more around the longitudinal axis, median 0.5° vs. 0.2° (internal or exter-nal rotation, p = 0.002), and showed increased maximum total point motion, median 1.0 vs. 0.4 mm (maximum migration or MTPM, p = 0.003).

Interpretation Our study indicates that better fixation can be obtained with the all-polyethylene design if proximally cemented thin components are used.

  ▪     

A multicentre study of the long-term results of using a flat-back polyethylene glenoid component in shoulder replacement for primary osteoarthritis

We report the long-term clinical and radiological outcomes of the Aequalis total shoulder replacement with a cemented all-polyethylene flat-back keeled glenoid component implanted for primary osteoarthritis between 1991 and 2003 in nine European centres. A total of 226 shoulders in 210 patients were retrospectively reviewed at a mean of 122.7 months (61 to 219) or at revision. Clinical outcome was assessed using the Constant score, patient satisfaction score and range of movement. Kaplan-Meier survivorship analysis was performed with glenoid revision for loosening and radiological glenoid loosening (SD) as endpoints. The Constant score was found to improve from a mean of 26.8 (SD 10.3) pre-operatively to 57.6 (SD 20.0) post-operatively (p < 0.001). Active forward flexion improved from a mean of 85.3° (SD 27.4) pre-operatively to 125° (SD 37.3) postoperatively (p < 0.001). External rotation improved from a mean of 7° (SD 6.5) pre-operatively to 30.3° (SD 21.8°) post-operatively (p < 0.001). Survivorship with revision of the glenoid component as the endpoint was 99.1% at five years, 94.5% at ten years and 79.4% at 15 years. Survivorship with radiological loosening as the endpoint was 99.1% at five years, 80.3% at ten years and 33.6% at 15 years. Younger patient age and the curettage technique for glenoid preparation correlated with loosening. The rate of glenoid revision and radiological loosening increased with duration of follow-up, but not until a follow-up of five years. Therefore, we recommend that future studies reporting radiological outcomes of new glenoid designs should report follow-up of at least five to ten years.     

Low-conforming all-polyethylene tibial component not inferior to metal-backed component in cemented total knee arthroplasty: prospective, randomized radiostereometric analysis study of the AGC total knee prosthesis

In a prospective, randomized study of 40 patients, the quality of fixation of cemented metal-backed versus all-polyethylene tibial components of the unconstrained anatomic graduated component total knee arthroplasty design was studied during 2 years using radiostereometric analysis (RSA). The shape, as well as the articulating geometry, of the implants was identical, as was the operative technique and the postoperative regimen. In this study, no negative consequences regarding the quality of fixation using an all-polyethylene tibial component with unconstrained articulating surfaces could be identified. In all aspects, the all-polyethylene tibial components displayed migration on par with, or sometimes lower than, their metal-backed counterparts. The rotations of the all-polyethylene components were equally low as for the metal-backed components, and maximum lift-off was significantly lower than for the metal-backed implants. We could not identify any collapse of the bone at the medial condyle or increased subsidence at the medial part of the tibia or increased rates of radiolucent lines in the knees with all-polyethylene components. All all-polyethylene implants seemed to be stable within the resolution of RSA between 1 and 2 years, a finding known to be of positive prognostic significance regarding future aseptic loosening.     

Metal-backed and all-polyethylene tibial components in total knee replacement.

One hundred seventy-five patients with 243 consecutive primary Press Fit Condylar cruciate-substituting total knee replacements were evaluated at a mean of 5.5 years. One hundred thirteen knees had modular metal-backed tibial components and 130 had all-polyethylene tibial components. The mean knee score and functional score for the patients with unrevised components was not significantly different. The incidence of osteolysis and synovitis was higher in patients in the modular metal-backed tibia group (5%; five patients, six knees). No patients in the all-polyethylene tibia group had osteolysis or synovitis. Five revision operations were necessary: four for osteolytic defects and one for synovitis, all in patients in the modular metal-backed tibia group. All of the retrieved polyethylene inserts had evident backside wear. The best case rate of survival of the all-polyethylene tibial components was 96%+/-0.8% at 7 years and for the modular metal-backed components it was 75%+/-10% at 7 years. Metal backing and modularity were added to the Press Fit Condylar total knee replacement design to improve fixation durability. However, the superiority of the modular metal-backed implants remains in question.     

Survival analysis of primary cemented total knee arthroplasty: which designs last?

Both posterior stabilization and metal backing of the tibial component are design changes that could alter the longevity of total knee arthroplasties (TKAs). Survival analysis data from 16 articles (5,950 knees) were combined to compare design features. No difference was found in survival between posterior stabilized implants and implants that were not stabilized or between metal-backed and all-polyethylene tibial components. Those all-polyethylene tibial components that were not stabilized showed significantly better survival than metal-backed, nonstabilized tibial components and posterior stabilized, metal-backed components (P<.05) but not posterior stabilized, all-polyethylene components. According to the currently available literature, posterior stabilization or metal backing of the tibial component does not improve the longevity of primary cemented fixed bearing condylar-type TKAs.