The effect of a metal-back without a stem upon the fixation of a tibial prosthesis

Cementing techniques for the tibial component in primary total knee replacement

The optimum cementing technique for the tibial component in cemented primary total knee replacement (TKR) remains controversial. The technique of cementing, the volume of cement and the penetration are largely dependent on the operator, and hence large variations can occur. Clinical, experimental and computational studies have been performed, with conflicting results. Early implant migration is an indication of loosening. Aseptic loosening is the most common cause of failure in primary TKR and is the product of several factors. Sufficient penetration of cement has been shown to increase implant stability. This review discusses the relevant literature regarding all aspects of the cementing of the tibial component at primary TKR.

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.

[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.

Results at 11.5 years of a series of 376 posterior stabilized HLS1 total knee replacements. Survivorship analysis, and risk factors for failure

Of 376 cemented posterior stabilized HLS1 TKRs inserted in 329 patients (mean age 70) between 1984 and 1988, information was available on 306 (81.4%) at the third follow-up in 1998: 118 patients deceased; 163 followed up clinically (Knee Society score) and radiographically; 25 revised (15 infections; 10 mechanical failures). At a mean follow-up of 11.5 years, the mean pain score was 43/50, and the mean ROM score 21/25 (both unchanged since 1989). The function score had declined linearly, from 70/100 in 1989 to 60/100 in 1998. Forty percent had tibial radiolucencies correlating with the extent of preoperative bone wear. Polyethylene wear (seen in 35% of knees) was always < 3 mm. The implant survival rate (infections included) was 93.7% (+/- 1.4%) after 10 years. All the mechanical failures were in advanced-OA patients with ACL-deficient knees and major bony deficiencies.

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

Forty-eight matched pairs of osteoarthritic knees from patients who underwent primary total knee arthroplasty with a round-on-round, Apollo Knee System were studied to evaluate the outcome between all-polyethylene and metal-backed tibial components. Patients were matched for patient factors, preoperative deformities, cruciate salvage or sacrifice, and surgical technique. At the last follow-up (average, 38.4 months), there was no statistically significant difference in terms of knee scores, patient self-assessment, and radiographic outcomes. No component required revision, and no revisions were pending. Maintenance of these results over time would project into better long-term success for all-polyethylene tibial components because of the amount of wear and osteolysis with current modular metal-backed tibial components. We advocate the use of a more cost-effective all-polyethylene tibial component in elderly patients (>70 years old) who are not likely to need the versatility of exchange of a modular polyethylene insert because of wear.

Does metal backing improve fixation of tibial component in unicondylar knee arthroplasty? A randomized radiostereometric analysis

In a prospective, randomized study, patients with medial gonarthrosis stage I to III according to Ahlbäck were allocated to a unicondylar knee arthroplasty (Miller-Galante, Zimmer, Inc., Warsaw, IN) with an all-polyethylene tibial component or metal-backed tibial component of the same design. The purpose of the study was to evaluate if metal backing enhanced tibial component fixation. A total of 45 knees (42 patients; 23 metal-backed components and 22 all-polyethylene components) were examined. We used radiostereometric analysis to measure micromotion of the tibial component over a period of 2 years after surgery. Hospital for Special Surgery score was used for clinical evaluation. We found no statistically significant differences in clinical results or migration of the tibial component over a 2-year follow-up period. These findings do not support better fixation of metal-backed tibial components. Because of these findings, we advocate all-polyethylene tibial components in unicondylar knee arthroplasties because of optimal biomechanical strength at a given height of tibial component, avoiding potential problems of modularity and minimizing the amount of interfaces, at a lower cost.

Clinical and radiologic survivorship of cementless tibial components fixed with finned polyethylene pegs

One hundred twenty patients (22 men, 98 women; 144 knees) with uncemented Freeman-Samuelson total knee arthroplasty were followed prospectively. Eighty-one patients had rheumatoid arthritis and 39 patients had osteoarthrosis. The mean follow-up period was 6.8 years. Three different types of tibial components were used: a high-density polyethylene component without stem, a metal-backed tibial component without stem, and a metal-backed tibial component with stem. Progressive varus tilting turned out to be an early sign of failure and occurred in 22% of the tibial components. Revision of the tibial component was done in 17 knees. Survival analysis with revision as endpoint revealed a survival rate of 79% at a follow-up period of 10 years. Cementless fixation of this design using macrointerlocking pegs and no other stabilization resulted in poor fixation and a high revision rate and cannot be recommended.