Matched-pair analysis of all-polyethylene versus metal-backed tibial components

Cemented all-poly tibia in resource constrained country, affordable and cost-effective care. Is it applicable at this era? Review article

Osteoarthritis of knee is a progressive disease requiring total knee replacement in advanced stage. TKR is being performed in high numbers in developing countries as well. It carries significant economic burden on health system including high cost of implants. Initially, tibial components were cemented all polyethylene monoblock constructs. Subsequent studies showed excellent long term follow up in terms of durability up to 20 years.Successive studies reported aseptic loosening as the cause of failure but such studies failed to address factors responsible for failure other than implant. Cemented metal-backed non-modular tibial components (MBT) are implants in current use. They provide modularity in terms of polyethylene thickness, stems wedges. A literature reported cost saving of $1.17 million, by operating 16,500 total joints using all poly-tibial tibial component rather than metal backed tibial component. studies have reported no significant difference in terms of survivorship, function and backside wear.

Methods

For this study only English written articles were included. Studies included case reports, case series, RCTs and systemic reviews related to all polyethylene tibial components. Articles reporting all levels of evidence – Level I to IV- were included as part of our research. PubMed, Google Scholar and Cochrane Reviews databases from 2000 to 2016 were searched for studies.

Results

Information was gathered and thoroughly studied from 30 articles with overall result in favor of the APTC implant.

Conclusion

All polyethylene tibial component (APTC) is an appealing and cost effective alternative, and is associated with the excellent survivorship and lower risk of revision. In light of the present-day economic evidence and long-term functional outcome, all-polyethylene should be in more use than metal backed especially in resource-constrained setting.

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Total Knee Arthroplasty revolutionized the management of end-stage arthritis of the knee.

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Tibial components were cemented all polyethylene monoblock with decreased bone resection.

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Cemented metal-backed non-modular tibial components (MBT) were subsequently introduced.

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Incremental cost can be a devastating problem for the patients at resource-constrained settings.

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In this era of competitive implant's industries, cost-effective options should be explored and adapted.

All-polyethylene versus metal-backed tibial component in total knee arthroplasty

PURPOSE

The aim of this systematic review was to evaluate the clinical outcomes, rate of revisions and complications of all-polyethylene tibial and metal-backed tibial components in patients treated with knee arthroplasty for primary or secondary osteoarthritis.

METHODS

A systematic review of the literature according to the PRISMA guidelines was performed. A comprehensive search of PubMed, Medline, CINAHL, Cochrane, Embase, and Google Scholar databases using various combinations of the keywords such as "knee", "arthroplasty", "metal-backed", and "all-polyethylene", since inception of databases to 2016, was performed.

RESULTS

Thirty-two articles, describing patients with all-polyethylene tibial or metal-backed tibial components in the setting of osteoarthritis, were included. A total of 68,202 knees in 58,942 patients were included, with an average age at surgery of 69.3 years, ranging from a mean age of 57.9-82 years. The mean KSS was 82.4 and 81.3 (n.s.), the mean KSS(F) was 73.6 and 74.9 (p = 0.04), the mean ROM was 104.5 and 104.6 (n.s.), and the mean HSS was 87 and 86, each, respectively, for the metal-backed tibial components group and all-polyethylene tibial components group. The overall rate of revisions was 1.90 %. The rate of revision in the metal-backed tibial components group was 1.85 %, whilst the rate of revision in the all-polyethylene tibial components group was 2.02 % (p < 0.00001).

CONCLUSION

Metal-backed tibial and all-polyethylene tibial components did not show any significant difference in most of the included outcome scores, but statistical differences were found in terms of complications and revision rate. These items have a negative impact on the cost-effectiveness of all-polyethylene tibial components. Even if all-polyethylene tibial components show similar clinical outcome score, equivalent range of knee motion, and long-term survival compared to metal-backed tibial components, complications and revision rate seem to lead the surgeon to prefer the last ones. The clinical relevance of this study is that metal-backed tibial components should be preferred in TKA surgery because complications are higher using all-polyethylene tibial components. On the other hand, the quality of evidence, according to GRADE system, is low underling the necessity of more randomised study to clarify these items.

LEVEL OF EVIDENCE

III.

All-Polyethylene Tibial Component Use for Elderly, Low-Demand Total Knee Arthroplasty Patients

BACKGROUND

Potential advantages combined with lower cost have prompted a renewed interest in modern all-polyethylene tibial designs.

METHODS

A total of 317 Natural Knee total knee arthroplasties with an all-polyethylene tibial component that was performed since 1993 were retrospectively reviewed to confirm that cost savings were not associated with inferior clinical results. They were primarily used in elderly, low-demand patients. The average age at the time of surgery was 80.8 years.

RESULTS

227 knees with a minimum of 2-year follow-up were identified. The average follow-up was 5.6 years (range, 2-20 years). Clinical and radiographic outcomes were evaluated. At the latest follow-up, the average Knee Society and functional score was 94.2 and 57.2. The average postoperative range of motion was 1.6°-115.4°. No patient required a revision for aseptic or septic loosening, wear, or instability. Only 5 knees had a partial nonprogressive cement/bone radiolucency. There was an approximate 33% cost savings for the implants when the all-polyethylene component was used.

CONCLUSION

An all-polyethylene tibial component of this design provides excellent results in the elderly population along with a significant cost savings.

A Meta-Analysis Comparing All-Polyethylene Tibial Component to Metal-Backed Tibial Component in Total Knee Arthroplasty: Assessing Survivorship and Functional Outcomes

BACKGROUND

This meta-analysis compares the clinical performance of all-polyethylene tibial (APT) to the metal-backed tibial (MBT) components.

METHODS

We included comparative studies in primary total knee arthroplasty involving APT and MBT implant components. The primary outcomes were function, durability, and reports of adverse events.

RESULTS

Twenty-eight articles with 95 847 knees were available for synthesis. The meta-analysis showed an association of APT with lower revision rates (incidence rate ratio, 0.709; P = .002) and adverse events (incidence rate ratio, 0.785; P = .204). Moderator analyses were performed to determine the effect of posterior cruciate ligament status on outcome, and no statistically significant effect was found for revision risk or adverse events incidence.

CONCLUSION

All-polyethylene tibial components seem to be an equal option, with less financial burden than the MBT.

All-polyethylene tibial components are equal to metal-backed components: systematic review and meta-regression

BACKGROUND

Less than 1% of all primary TKAs are performed with an all-polyethylene tibial component, although recent studies indicate all-polyethylene tibial components are equal to or better than metal-backed ones.

QUESTIONS/PURPOSES

We asked whether the metal-backed tibial component was clinically superior to the all-polyethylene tibial component in primary TKAs regarding revision rates and clinical functioning, and which modifying variables affected the revision rate.

METHODS

We systematically reviewed the literature for clinical studies comparing all-polyethylene and metal-backed tibial components used in primary TKAs in terms of revision rates, clinical scores, and radiologic parameters including radiostereometric analysis (RSA). Meta-regression techniques were used to explore factors modifying the observed effect. Our search yielded 1557 unique references of which 26 articles were included, comprising more than 12,500 TKAs with 231 revisions for any reason.

RESULTS

Meta-analysis showed no differences between the all-polyethylene and metal-backed components except for higher migration of the metal-backed components. Meta-regression showed strong evidence that the all-polyethylene design has improved with time compared with the metal-backed design.

CONCLUSIONS

The all-polyethylene components were equivalent to metal-backed components regarding revision rates and clinical scores. The all-polyethylene components had better fixation (RSA) than the metal-backed components. The belief that metal-backed components are better than all-polyethylene ones seems to be based on studies from earlier TKAs. This might no longer be true for modern TKAs.

LEVEL OF EVIDENCE

Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Tibial component designs in primary total knee arthroplasty: should we reconsider all-polyethylene component?

PURPOSE

Despite the frequency with which total knee arthroplasties (TKAs) are performed, whether they are best performed using all-polyethylene or metal-backed tibial components remains a controversy. The aim of the present study was to determine the advantages and disadvantages of metal-backed compared with all-polyethylene tibial components during TKAs through an evaluation of current literature.

METHODS

A meta-analysis and systematic review of randomized and non-randomized comparative studies comparing metal-backed with all-polyethylene tibial components during TKAs were performed. The focus of the analysis was on the outcomes of knee score, range of motion (ROM), quality of life, implant alignment, tibial migration, radiolucent line, complication, reoperation, and implant survivorship.

RESULTS

A total of 10 randomized/quasi-randomized controlled trials and 13 non-randomized comparative studies assessing 19,767 TKAs were eligible. On the basis of these studies, no significant differences were found between the 2 groups with regard to knee score, ROM, quality of life, complication, and reoperation. The findings indicated that using all-polyethylene tibial components is associated with lower continuous migration rate compared with metal-backed tibial components. Only 13 studies provided adequate data on implant survivorship during intermediate or long-term follow-up. Of these, 9 found that no statistical significance existed between the 2 groups. The other 3 studies found that using all-polyethylene components yielded a higher survival rate than using metal-backed components.

CONCLUSIONS

Metal-backed tibial components had no obvious advantages over all-polyethylene tibial components in TKAs. However, this finding should be interpreted with caution due to publication bias, low methodological quality of the included studies, and different surgical interventions.

LEVEL OF EVIDENCE

Therapeutic study (systematic review and meta-analysis), Level III.

All-polyethylene tibial components in obese patients are associated with low failure at midterm followup

BACKGROUND

In the United States, the obese population has increased markedly over the last four decades, and this trend continues. High patient weight places additional stress on TKA components, which may lead to increased polyethylene wear, osteolysis, radiolucencies, and clinical failure. Metal-backed tibial components and all-polyethylene tibial components in the general population have comparable osteolysis and failure, but it is unclear whether these components yield similar osteolysis and failure in obese patients.

QUESTIONS/PURPOSES

We therefore determined the (1) function, (2) occurrence of osteolysis, and (3) complications in a cohort of obese patients receiving all-polyethylene tibial components.

PATIENTS AND METHODS

Between September 17, 1996, and December 19, 2002, we implanted all-polyethylene tibial components in 90 obese patients (125 knees); 24 patients (33 knees) died and 13 patients (17 knees) were lost to followup, leaving 53 patients (59%) with 75 knees. All surgeries were cruciate-retaining, tricompartmental TKAs. We evaluated patients with Knee Society Scores and serial radiographs. Minimum followup was 7 years (mean, 10.4 years; range, 7-14 years).

RESULTS

At latest followup, mean Knee Society Score was 92 points. There were five tibial radiolucencies, all less than 1 mm and characterized as nonprogressive. We observed minimal, nonprogressive osteolysis in one knee. One patient required reoperation after a traumatic event. There were no implant-related failures and no implants at risk of failure.

CONCLUSIONS

At an average 10-year followup, all-polyethylene tibial components were functioning well in this obese group. These findings confirm the effectiveness of all-polyethylene tibial components in obese patients.

Cemented all-polyethylene and metal-backed polyethylene tibial components used for primary total knee arthroplasty: a systematic review of the literature and meta-analysis of randomized controlled trials involving 1798 primary total knee implants

BACKGROUND

The cost of the implant as part of a total knee arthroplasty accounts for a substantial portion of the costs for the overall procedure: all-polyethylene tibial components cost considerably less than cemented metal-backed tibial components. We performed a systematic review of the literature to determine whether the clinical results of lower-cost all-polyethylene tibial components were comparable with the results of a more expensive metal-backed tibial component.

METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, EBSCO CINAHL, the bibliographies of identified articles, orthopaedic meeting abstracts, health technology assessment web sites, and important orthopaedic journals. This search was performed for the years 1990 to the present. No language restriction was applied. We restricted our search to Level-I studies involving participants who received either an all-polyethylene or a metal-backed tibial implant. The primary outcome measures were durability, function, and adverse events. Two reviewers independently screened the papers for inclusion, assessed trial quality, and extracted data. Effects estimates were pooled with use of fixed and random-effects models of risk ratios, calculated with 95% confidence intervals. Heterogeneity was assessed with the I2 statistic. Forest plots were also generated.

RESULTS

Data on 1798 primary total knee implants from twelve studies were analyzed. In all studies, the median or mean age of the participants was greater than sixty-seven years, with a majority of the patients being female. There was no difference between patients managed with an all-polyethylene tibial component and those managed with a metal-backed tibial component in terms of adverse events. There was no significant difference between the two groups in terms of the durability of the implants at two, ten, and fifteen years postoperatively, regardless of the year or how durability was defined (revision or radiographic failure). Finally, with use of a variety of validated measures, there was no difference between the two groups in terms of functional status at two, eight, and ten years, regardless of the measure used.

CONCLUSION

A less expensive all-polyethylene component as part of a total knee arthroplasty has results equivalent to those obtained with a cemented metal-backed tibial component. Using a total knee implant with a cemented all-polyethylene tibial component could save the healthcare system substantial money while obtaining equivalent results to more expensive cemented designs and materials.

Metal-backed versus all-polyethylene tibial components in primary total knee arthroplasty

BACKGROUND AND PURPOSE

The choice of either all-polyethylene (AP) tibial components or metal-backed (MB) tibial components in total knee arthroplasty (TKA) remains controversial. We therefore performed a meta-analysis and systematic review of randomized controlled trials that have evaluated MB and AP tibial components in primary TKA.

METHODS

The search strategy included a computerized literature search (Medline, EMBASE, Scopus, and the Cochrane Central Register of Controlled Trials) and a manual search of major orthopedic journals. A meta-analysis and systematic review of randomized or quasi-randomized trials that compared the performance of tibial components in primary TKA was performed using a fixed or random effects model. We assessed the methodological quality of studies using Detsky quality scale.

RESULTS

9 randomized controlled trials (RCTs) published between 2000 and 2009 met the inclusion quality standards for the systematic review. The mean standardized Detsky score was 14 (SD 3). We found that the frequency of radiolucent lines in the MB group was significantly higher than that in the AP group. There were no statistically significant differences between the MB and AP tibial components regarding component positioning, knee score, knee range of motion, quality of life, and postoperative complications.

INTERPRETATION

Based on evidence obtained from this study, the AP tibial component was comparable with or better than the MB tibial component in TKA. However, high-quality RCTs are required to validate the results.

All-polyethylene tibial components in modern total knee arthroplasty

Most total knee arthroplasty prostheses have modular tibial components with metal-backed tibial baseplates. Biomechanical studies have demonstrated mechanical advantages to a metal-backed tibial component in terms of tibial load transfer. In addition, tibial component modularity provides intraoperative flexibility and may provide an advantage in the setting of subsequent revision knee surgery. However, clinical evidence does not support the preferential use of metal-backed tibial components. Modularity introduces the potential for backside wear and associated osteolysis. Also, several recent studies have shown no significant differences in clinical and radiographic outcomes between metal-backed and all-polyethylene tibial components. In addition, all-polyethylene tibial components are less expensive than metal-backed components; increased usage of all-polyethylene components could help decrease the cost of health care.

A FUNCTIONAL AND ROENTGENOGRAPHIC PRELIMINARY COMPARATIVE STUDY USING METAL-BACKED AND ALL-POLYETHYLENE TIBIAL COMPONENTS IN TOTAL KNEE ARTHROPLASTY

OBJECTIVE

To describe and clinically and radiographically compare patients who underwent total knee arthroplasty (TKA) with all-polyethylene (ALP) and metal-backed (MTB) tibial implants.

METHODS

Patients who underwent TKA between January 1988 and December 2004 were grouped according to the type of implant received: all-polyethylene or metal-backed. Sixty patients came for evaluations, totaling 82 operated knees. Among these, 22 patients had undergone TKA only with ALP (12 unilateral and 10 bilateral cases), 33 patients only with MTB (26 unilateral and 7 bilateral cases) and five patients underwent TKA with ALP in one knee and MTB in the other. The knees were divided thus: group 1, 37 knees with ALP; and group 2, 45 knees with MTB.

RESULTS

There were no differences in clinical or functional evaluations between the groups. The mean radiolucency in the femur was 0.838 mm for the patients in group 1 and 0.356 mm for the patients in group 2 (p = 0.049). For the tibia, in the AP view, there was a mean value of 2.703 mm for group 1 and 0.733 mm for group 2 (p = 0.000). In the lateral view, the mean values for osteolysis was 0.405 mm for group 1 and 0.200 mm for group 2 (p = 0.074).

CONCLUSIONS

There were no differences between the groups in the functional and clinical evaluations. However, greater radiolucency was observed in the arthroplasties with ALP, both in the femur in the lateral view and in the tibia in the AP view. Level of evidence IV - case series study.

The all-polyethylene tibial component in primary total knee arthroplasty

Outcomes of total knee arthroplasties performed with modern all-polyethylene tibial components have been found to be comparable with or better than those of arthroplasties done with metal-backed modular components in numerous mid-to-long-term follow-up studies, radiostereometric analyses, and the few prospective randomized trials available. Advantages of an all-polyethylene tibial component over a metal-backed modular component include lower cost, avoidance of locking-mechanism issues and backside wear, and increased polyethylene thickness after identical bone resections. Disadvantages of an all-polyethylene tibial component compared with a metal-backed modular component include a lack of modularity, limiting intraoperative options; no option for liner removal in the setting of acute irrigation and débridement; and no option for late liner exchange. Primary total knee arthroplasty with a modern all-polyethylene design can be done in many patients, with substantial cost savings across the health-care system.

Mobile and fixed-bearing (all-polyethylene tibial component) total knee arthroplasty designs. A prospective randomized trial

BACKGROUND

Proponents of mobile-bearing total knee arthroplasty believe that it has potential advantages over a fixed-bearing design in terms of diminished wear and improved motion and/or function, but these advantages have not been demonstrated in a randomized clinical comparison to our knowledge. We conducted a patient-blinded, prospective, randomized clinical trial to compare mobile-bearing and fixed-bearing cruciate-substituting total knee arthroplasties of the same design.

METHODS

Patients between the ages of sixty and eighty-five years were prospectively randomized to receive a cruciate-substituting rotating-platform design or a fixed-bearing design with an all-polyethylene tibial component. There were no significant differences in the demographic characteristics (mean age, 72.2 years; mean American Society of Anesthesiologists score, 2.7; mean body mass index, 31.8 kg/m(2)) or preoperative clinical or radiographic measures between the groups. Routine clinical and radiographic follow-up measures included the Knee Society score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Short Form-36 (SF-36) outcome measures.

RESULTS

The results of 312 arthroplasties (136 with an all-polyethylene tibial component and 176 rotating-platform designs) in 273 patients were analyzed at a minimum of two years (mean, forty-two months) postoperatively. Although there was significant improvement in both groups, there was no significant difference between the groups with regard to the mean postoperative range of motion (110.9 degrees and 109.1 degrees, respectively; p = 0.21), the mean KSS clinical score (90.4 and 88.2 points; p = 0.168), or the mean KSS pain score (44.9 and 43.1 points; p = 0.108) at this follow-up point. There were ten revisions: seven because of infection, one because of patellar fracture, one because of instability, and one because of aseptic loosening.

CONCLUSIONS

The two designs functioned equivalently at the time of early follow-up in this low-to-moderate-demand patient group. The rotating-platform design had no significant clinical advantage over the design with the all-polyethylene tibial component.

All-polyethylene compared with metal-backed tibial components in total knee arthroplasty at ten years. A prospective, randomized controlled trial

BACKGROUND

Several studies have described equivalent performance on radiostereometric analysis at two years for metal-backed compared with all-polyethylene stemmed tibial implants. The purpose of this study was to determine the ten-year survivorship results of these two designs from a large randomized controlled trial.

METHODS

Patients who were fifty years old or more, with no history of infection, and were undergoing primary total knee arthroplasty were randomized at the time of surgery to receive either an all-polyethylene or a metal-backed tibial component. Patients were assessed preoperatively and at one, three, five, eight, and ten years postoperatively. All assessments included a clinical history, a physical examination, and a radiographic evaluation. A total of 510 consecutive patients (566 knees) were recruited from August 1993 to January 1997. The mean age of the patients at the time of the index arthroplasty was 69.3 years, and 299 (59%) were women. The primary diagnosis was osteoarthritis for 458 knees (80.9%) and rheumatoid arthritis for 108 knees (19.1%).

RESULTS

Two hundred and ninety-three patients returned for the ten-year follow-up evaluation. A total of twenty-eight knees had been revised. Ten-year survivorship, with revision for any reason (or the time at which patients were documented as requiring revision but were unfit for surgery) as the end point, was 94.5% (95% confidence interval, 90.4% to 96.8%) for the all-polyethylene design and 96% (95% confidence interval, 92.6% to 97.8%) for the metal-backed design. Ten-year survivorship, with aseptic failure as the end point, was 97% (95% confidence interval, 93.3% to 98.7%) for the all-polyethylene design and 96.8% (95% confidence interval, 93.6% to 98.4%) for the metal-backed design. On the basis of the numbers available at ten years, there was no significant difference in survivorship between the two designs (p > 0.05).

CONCLUSIONS

The long-term results demonstrate excellent survivorship, with revision as the end point, for both the metal-backed and the all-polyethylene tibial component designs with no differences noted between the two.

Excellent survival of all-polyethylene tibial components in a community joint registry

The advantages of the monoblock design and lower cost have prompted renewed interest in the all-polyethylene tibia in total knee arthroplasty. We prospectively followed patients with all-polyethylene tibial total knee arthroplasties over a 14-year period. Since 1991, 443 total knee arthroplasties using an all-polyethylene tibia component were implanted by 12 surgeons in four hospitals associated with a community registry. One of three designs was used in over 98% of cases. The mean age of the patient population was 77 years and 78% were female. Ninety-three patients died with their prosthesis intact. Three revisions were performed on this population with mean followup of 66.3 months (range, 0-158 months). Kaplan-Meier survival analysis revealed 99.4% survival at 14.3 years with revision for any reason as the end point. With aseptic loosening or wear as the revision reason, survival is 99.7% at 14.3 years. Total knee arthroplasty with one of the three contemporary congruent all-polyethylene tibia designs used in this registry performed extremely well in this population; savings for this group (compared to those with a metal-backed component) was estimated at $729 per case. If all patients older than 75 years of age in our registry had received an all-polyethylene tibia, the estimated savings for the implant alone would have been $1.28 million.

LEVEL OF EVIDENCE

Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

[A comparison of all-polyethylene and metal-backed tibial components in total knee arthroplasty]

PURPOSE OF THE STUDY

The purpose of our study was to compare the clinical, functional and radiological results of two types of tibial components for the same total knee prosthesis (posterior stabilized HLS), all-polyethylene (group A) and metal-backed (group B), in order to answer the following question: does use of an all-polyethylene piece affect mid-term outcome of total knee arthroplasty (TKA)?

MATERIAL AND METHODS

This was a retrospective comparative analysis of a single-center non-randomized consecutive series of 169 patients with an all-polyethylene posterior stabilized cemented gliding TKA. This series was matched with another retrospective series of 169 posterior stabilized cemented TKA with a metal-backed tibial piece. Matching factors were age, gender, etiology, and follow-up. The two series were extracted from our database which included all patients who underwent surgery for a TKA in the same institution (Lyon Civil Hospices) performed by one of the authors (PN) or under his responsibility between 1987 and 1996 for group A (all-poly) and between 1987 and 1997 for group B (metal-backed). Mean follow-up was 66 months. The IKS scores and radiological findings were recorded.

RESULTS

In group A, 96% of patients were satisfied, 93% in group B. The IKS knee score for group A was 89 +/- 10.8 and 88.3 +/- 11.9 for group B. The function score was 68 +/- 23.7 in group A and 71 +/- 24 in group B. Mean flexion was 113 degrees for both groups. Non-progressive lucent lines were noted in 27 cases in group A and 23 in group B. Revision TKA was performed for 18 knees in group A, including six with implant replacement (three of them for infection). In group B, there were ten revisions, seven with implant replacement including one with infection and three without implant replacement. The 10-year survival was 94.5% in group A and 93.64% in group B. There was no significant difference in the function and knee scores, the presence of lucent lines, and the number of implant replacements between group A and group B (p>0.05).

DISCUSSION

This study was unable to demonstrate any superiority in clinical and radiological results for TKA between the all-polyethylene and metal-backed options at five years follow-up.

All-polyethylene and metal-backed tibias have similar outcomes at 10 years: a randomized level I [corrected] evidence study

The advantages of a monoblock design and lower cost have generated renewed interest in all-polyethylene tibial components for total knee arthroplasty (TKA). We hypothesized an all-polyethylene design would function equivalently to a metal-backed modular design at lower cost and at long-term followup. We report the 8- to 12-year followup of our earlier reported prospective randomized comparison of a modern congruent all-polyethylene tibial component with a modular metal-backed tibial component of the same design. The mean age of the patients was 69 years and 92% were diagnosed with osteoarthritis. Of 290 patients (316 total knee arthroplasties) enrolled, 120 patients died, 22 had revision surgery, and one was lost to followup. We followed the remaining 147 patients (167 TKAs: 97 all-polyethylene/70 metal-backed) clinically and radiographically. There were no differences in knee function (Knee Society clinical score, range of motion, stability) or radiographic parameters between the groups. Of the 22 revisions, only three were performed for tibial aseptic loosening (three metal-backed). Ten-year survivorship of the all-polyethylene tibial component was 91.6% with revision for any reason and 100% for aseptic loosening. The metal-backed tibial component survivorship was 88.9% with revision for any reason and 94.3% for aseptic loosening. The contemporary all-polyethylene tibial component functioned equivalently to its monoblock counterpart and was less costly.

Wear and osteolysis around total knee arthroplasty

Osteolysis induced by wear debris of ultra-high-molecular-weight polyethylene has emerged as a significant problem after total knee arthroplasty. The generation of polyethylene wear and the development of osteolysis around total knee arthroplasty are caused by a combination of patient, implant, and surgical factors. Activity level over time may be the most important patient factor affecting the loads placed on a total knee replacement, but it is the most difficult to manage. Multiple factors related to the manufacturing of the polyethylene implant influence the extent of wear, and surgeons should be cautious in considering enhanced polyethylenes pending results of further investigations. The optimal design of the articular bearing surface remains controversial but needs to be considered with respect to the stresses imparted on component-bone and modular tibial backside interfaces. Surgical factors, including restoration of alignment and ligament balance, are important for long-term durability of the implant. Methods of measuring the wear of total knee implants are still evolving. Thus, when confronted with a worn total knee implant and developing osteolysis, the surgeon should consider each of these factors in selecting the best management option to eliminate the source of debris and minimize the potential for wear and osteolysis following revision.

Comparison of the 2-incision and mini-incision posterior total hip arthroplasty technique: a retrospective match-pair controlled study

We compared the outcomes of the mini-posterior and 2-incision total hip arthroplasty approaches by analyzing 43 matched pairs of patients. The following outcomes were evaluated: (1) Harris Hip Score, (2) Medical Outcomes Study 36-Item Short-Form Health Survey, (3) the Medical Outcomes Study Sleep Scale, and (4) the Western Ontario and McMaster Osteoarthritis Index. Function was regained earlier by patients having the 2-incision total hip arthroplasty as determined by length of hospitalization (P = .002) and multiple return to function parameters, although this may be the result of hip precautions placed on the posterior group. Posterior mini-incision patients had less operating time (P < .0001) and blood loss (P = .001). Complications did not differ between surgical techniques. No patients were revised. The 2-incision operation was better for function and length of stay, and the posterior mini-incision was easier to perform, although these groups used different selection criteria.

Osteolysis after total knee arthroplasty: influence of tibial baseplate surface finish and sterilization of polyethylene insert. Findings at five to ten years postoperatively

BACKGROUND

Debris displaced from the articular and backside surfaces of the polyethylene inserts of modular tibial components is considered a chief cause of osteolysis at the sites of total knee arthroplasties. One design of total knee replacement featured changes, over time, in the proximal surface roughness of the tibial baseplate and the method of sterilization of the polyethylene insert. We hypothesized that polishing the baseplate surface and sterilizing the insert with means other than gamma radiation in air had reduced the prevalence of osteolysis.

METHODS

Three hundred and sixty-five posterior cruciate ligament-retaining Anatomic Modular Knee primary total knee arthroplasties were performed in 300 patients from 1987 to 1998. Anteroposterior and lateral radiographs of the knees were made within a five to ten-year postoperative interval. Two arthroplasty specialists independently examined the radiographs for evidence of osteolysis (defined as any nonlinear region of cancellous bone loss with delineable margins).

RESULTS

Osteolysis was identified in 34% (eighty-two) of 242 knees treated with an insert that had been gamma-irradiated in air and affixed to a rough baseplate surface, and it was identified in 9% (nine) of ninety-eight knees treated with an insert that had been gamma-irradiated in an inert gas, or had not been irradiated, and joined to a polished surface. Osteolysis was associated with six factors, including one related to the patient (male gender), one related to the tibial baseplate (the proximal surface finish), three related to the polyethylene insert (the material from which it was machined, the sterilization method, and the shelf age), and one related to the technique (hyperextension of the femoral component relative to the tibial component).

CONCLUSIONS

In this design of a total knee prosthesis, polishing the tibial baseplate counterface and implementing a more contemporary sterilization practice (as opposed to gamma radiation in air) noticeably diminished but did not eliminate osteolysis.

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 components (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 degrees vs. 0.2 degrees (internal or external 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.

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.

Experience with an all-polyethylene total knee arthroplasty in younger, active patients with follow-up from 2 to 11 years

There are few modern reports that document the results of all-polyethylene (all-poly) tibial components in younger, active patients. The potential benefits of this design are the elimination of backside wear and lower implant cost than modular, metal-backed components. Nonetheless, since the mid 1980s, modular, metal-backed tibial trays have dominated the total knee arthroplasty market based on finite-element analysis studies that demonstrated superior force distribution compared with conventional all-poly components. As a result, backside wear has become an emerging problem and refocused design efforts on unitized components. Our clinical experience indicates that an all-poly tibial component fixed with cement can provide excellent performance and survivorship even in younger, active patients at intermediate follow-up.

Long-term results of total condylar knee arthroplasty

From 1979 to 1984, 126 consecutive Total Condylar (Howmedica, Rutherford, NJ) knee arthroplasties were performed at a hospital in Taiwan, of which 64 knees were available for evaluation. The patients' average weight was 58 kg. The average Hospital for Special Surgery knee score at the latest follow-up was 86 points. Using revision for mechanical failure as an end point, the 20-year overall survival was 91.9%. The survival for the all-polyethylene tibial component was 96.4% and for the metal-backed tibial component was 88.4%. The difference was statistically significant (P < .001). We recommend the use of the more cost-effective and durable all-polyethylene tibial component for a primary cemented total knee arthroplasty, particularly in Asians with a relatively low weight and who are relatively inactive, especially in elderly people.

Properties of the tibial component regarding impact load

Load transmission through knee prostheses was examined to clarify how the tibial component behaves under dynamic loading conditions. We did Genesis II total knee arthroplasty using sawbones and measured impact load transmission ratios using the split-Hopkinson pressure bar technique. We also measured the polyethylene strain when an impact load was applied using a strain gauge bonded to the anterior surface of the polyethylene. The impact load transmission ratios of metal-backed and all-polyethylene tibial components were less than 4%. Greater load transmission was observed with metal-backed components, which suggests that some of the applied dynamic load is transferred directly to the tibial cortical bone. Increasing polyethylene thickness decreased impact load transmission ratios in both components, which might lower the cancellous bone stresses beneath tibial implants. Greater strain in the tibial component was observed in all-polyethylene components. Increased polyethylene thickness did not significantly decrease the polyethylene strain, probably because of the nonlinear elastic behavior of the polyethylene material. The distant positioning of the strain gauge may, however, have prevented the detection of local contact strains. Recent clinical studies did not confirm our theoretical predictions, suggesting that other factors contribute more significantly to the clinical outcome in current total knee arthroplasty.

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.