Palamed G compared with Palacos R with gentamicin in Charnley total hip replacement. A randomised, radiostereometric study of 60 HIPS

Current concepts and outcomes in cemented femoral stem design and cementation techniques: the argument for a new classification system

Cemented implant fixation design principles have evolved since the 1950s, and various femoral stem designs are currently in use to provide a stable construct between the implant–cement and cement–bone interfaces.

Cemented stems have classically been classified into two broad categories: taper slip or force closed, and composite beams or shaped closed designs. While these simplifications are acceptable general categories, there are other important surgical details that need to be taken into consideration such as different broaching techniques, cementing techniques and mantle thickness.

With the evolution of cemented implants, the introduction of newer implants which have hybrid properties, and the use of different broaching techniques, the classification of a very heterogenous group of implants into simple binary categories becomes increasingly difficult. A more comprehensive classification system would aid in comparison of results and better understanding of the implants’ biomechanics.

We review these differing stem designs, their respective cementing techniques and geometries. We then propose a simple four-part classification system and summarize the long-term outcomes and international registry data for each respective type of cemented prosthesis.

Cite this article: EFORT Open Rev 2020;5:241-252. DOI: 10.1302/2058-5241.5.190034

Palacos compared to Palamed bone cement in total hip replacement: a randomized controlled trial

Background and purpose - Stability and survival of cemented total hip prostheses is dependent on a multitude of factors, including the type of cement that is used. Bone cements vary in viscosity, from low to medium and high. There have been few clinical RSA studies comparing the performance of low- and high-viscosity bone cements. We compared the migration behavior of the Stanmore hip stem cemented using novel low-viscosity Palamed bone cement with that of the same stem cemented with conventional high-viscosity Palacos bone cement. Patients and methods - We performed a randomized controlled study involving 39 patients (40 hips) undergoing primary total hip replacement for primary or secondary osteoarthritis. 22 patients (22 hips) were randomized to Palacos and 17 patients (18 hips) were randomized to Palamed. Migration was determined by RSA. Results - None of these 40 hips had been revised at the 10-year follow-up mark. To our knowledge, the patients who died before they reached the 10-year endpoint still had the implant in situ. No statistically significant or clinically significant differences were found between the 2 groups for mean translations, rotations, and maximum total-point motion (MTPM). Interpretation - We found similar migration of the Stanmore stem in the high-viscosity Palacos cement group and the low-viscosity Palamed cement group. We therefore expect that the risk of aseptic loosening with the new Palamed cement would be comparable to that with the conventional Palacos cement. The choice of which type of bone cement to use is therefore up to the surgeon's preference.

Total hip replacement and surface replacement for the treatment of pain and disability resulting from end-stage arthritis of the hip (review of technology appraisal guidance 2 and 44): systematic review and economic evaluation

BACKGROUND

Total hip replacement (THR) involves the replacement of a damaged hip joint with an artificial hip prosthesis. Resurfacing arthroplasty (RS) involves replacement of the joint surface of the femoral head with a metal surface covering.

OBJECTIVES

To undertake clinical effectiveness and cost-effectiveness analysis of different types of THR and RS for the treatment of pain and disability in people with end-stage arthritis of the hip, in particular to compare the clinical effectiveness and cost-effectiveness of (1) different types of primary THR and RS for people in whom both procedures are suitable and (2) different types of primary THR for people who are not suitable for hip RS.

DATA SOURCES

Electronic databases including MEDLINE, EMBASE, The Cochrane Library, Current Controlled Trials and UK Clinical Research Network (UKCRN) Portfolio Database were searched in December 2012, with searches limited to publications from 2008 and sample sizes of ≥ 100 participants. Reference lists and websites of manufacturers and professional organisations were also screened.

REVIEW METHODS

Systematic reviews of the literature were undertaken to appraise the clinical effectiveness and cost-effectiveness of different types of THR and RS for people with end-stage arthritis of the hip. Included randomised controlled trials (RCTs) and systematic reviews were data extracted and risk of bias and methodological quality were independently assessed by two reviewers using the Cochrane Collaboration risk of bias tool and the Assessment of Multiple Systematic Reviews (AMSTAR) tool. A Markov multistate model was developed for the economic evaluation of the technologies. Sensitivity analyses stratified by sex and controlled for age were carried out to assess the robustness of the results.

RESULTS

A total of 2469 records were screened of which 37 were included, representing 16 RCTs and eight systematic reviews. The mean post-THR Harris Hip Score measured at different follow-up times (from 6 months to 10 years) did not differ between THR groups, including between cross-linked polyethylene and traditional polyethylene cup liners (pooled mean difference 2.29, 95% confidence interval -0.88 to 5.45). Five systematic reviews reported evidence on different types of THR (cemented vs. cementless cup fixation and implant articulation materials) but these reviews were inconclusive. Eleven cost-effectiveness studies were included; four provided relevant cost and utility data for the model. Thirty registry studies were included, with no studies reporting better implant survival for RS than for all types of THR. For all analyses, mean costs for RS were higher than those for THR and mean quality-adjusted life-years (QALYs) were lower. The incremental cost-effectiveness ratio for RS was dominated by THR, that is, THR was cheaper and more effective than RS (for a lifetime horizon in the base-case analysis, the incremental cost of RS was £11,284 and the incremental QALYs were -0.0879). For all age and sex groups RS remained clearly dominated by THR. Cost-effectiveness acceptability curves showed that, for all patients, THR was almost 100% cost-effective at any willingness-to-pay level. There were age and sex differences in the populations with different types of THR and variations in revision rates (from 1.6% to 3.5% at 9 years). For the base-case analysis, for all age and sex groups and a lifetime horizon, mean costs for category E (cemented components with a polyethylene-on-ceramic articulation) were slightly lower and mean QALYs for category E were slightly higher than those for all other THR categories in both deterministic and probabilistic analyses. Hence, category E dominated the other four categories. Sensitivity analysis using an age- and sex-adjusted log-normal model demonstrated that, over a lifetime horizon and at a willingness-to-pay threshold of £20,000 per QALY, categories A and E were equally likely (50%) to be cost-effective.

LIMITATIONS

A large proportion of the included studies were inconclusive because of poor reporting, missing data, inconsistent results and/or great uncertainty in the treatment effect estimates. This warrants cautious interpretation of the findings. The evidence on complications was scarce, which may be because of the absence or rarity of these events or because of under-reporting. The poor reporting meant that it was not possible to explore contextual factors that might have influenced study results and also reduced the applicability of the findings to routine clinical practice in the UK. The scope of the review was limited to evidence published in English in 2008 or later, which could be interpreted as a weakness; however, systematic reviews would provide summary evidence for studies published before 2008.

CONCLUSIONS

Compared with THR, revision rates for RS were higher, mean costs for RS were higher and mean QALYs gained were lower; RS was dominated by THR. Similar results were obtained in the deterministic and probabilistic analyses and for all age and sex groups THR was almost 100% cost-effective at any willingness-to-pay level. Revision rates for all types of THR were low. Category A THR (cemented components with a polyethylene-on-metal articulation) was more cost-effective for older age groups. However, across all age-sex groups combined, the mean cost for category E THR (cemented components with a polyethylene-on-ceramic articulation) was slightly lower and the mean QALYs gained were slightly higher. Category E therefore dominated the other four categories. Certain types of THR appeared to confer some benefit, including larger femoral head sizes, use of a cemented cup, use of a cross-linked polyethylene cup liner and a ceramic-on-ceramic as opposed to a metal-on-polyethylene articulation. Further RCTs with long-term follow-up are needed.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013003924.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

The predictive value of radiostereometric analysis for stem survival in total hip arthroplasty. A systematic review

BACKGROUND

The high precision of radiostereometric analysis (RSA) has enabled us to predict long-term implant survival with a small sample of patients followed for a relatively short period of time. The purpose of our systematic review was to validate the predictive value of two-year RSA results on long-term survival of different types of primary total hip arthroplasty stems.

METHODS

We systematically reviewed literature to determine the maximum total point motion (MTPM), distal migration and rotation of stem designs and correlated these values to survival rates for aseptic loosening of these specific stems in arthroplasty registries.

RESULTS

We included 32 studies describing migration of 15 different stem designs. The mean MTPM for straight polished cemented stems was 1.35 mm, for other cemented stems 0.83 mm and for other uncemented stems 1.50 mm. No data were available for the uncemented collared stem. Mean distal migration for straight polished cemented stems was 1.24 mm, for other cemented stems 0.26 mm, the uncemented collared stem 0.40 mm and for other uncemented stems 0.66 mm. Internal rotation was presented for 13 stems and all stems rotated into retroversion. All stems showed 10-year survival rates of >97% corrected for aseptic loosening.

DISCUSSION

Reporting RSA results in a universal way including interpretation of outliers could improve the predictive value of RSA, allowing this technique to be an important tool during the phased introduction of new implant designs. However, a quality assessment of the data by an experienced reviewer is essential.

Comparison of Refobacin bone cement and palacos with gentamicin in total hip arthroplasty: an RSA study with two years follow-up

Previous experience has demonstrated the importance of testing new bone cement in vivo before widespread clinical use. We performed a consecutive, radiostereometric (RSA) study comparing Refobacin Bone Cement (RBC) to the well proven Palacos with Gentamicin (PWG). According to the manufacturer of RBC it has the equivalent characteristics as PWG, and in vitro tests show good results. The purpose of this study was to evaluate whether RBC is safe to use in clinical practice for total hip arthroplasty (THA). Two consecutive series of patients with primary osteoarthritis received a THA using a highly polished, collarless, tapered stem with a hollow centralizer. The study comprises 21 hips with RBC and 30 with PWG. The patients were followed up for two years with repeated RSA examinations and clinical outcome questionnaires SF-12 and WOMAC. There were no statistically significant migratory differences between the groups. The mean subsidence after two years was 1.28 mm and 1.40 mm, and the mean retroversion was 1.03° and 0.99°, for the RBC and the PWG groups respectively. Almost all migration occurred in the interface between the stem and the cement. The WOMAC and SF12 clinical scores did not reveal any clinical differences between the groups. We conclude that, as previous in vitro tests indicate, RBC performs as well as PWG and seems to be safe to use in clinical practice for THA.

Adherence of hip and knee arthroplasty studies to RSA standardization guidelines. A systematic review

BACKGROUND AND PURPOSE

Guidelines for standardization of radiostereometry (RSA) of implants were published in 2005 to facilitate comparison of outcomes between various research groups. In this systematic review, we determined how well studies have adhered to these guidelines.

METHODS

We carried out a literature search to identify all articles published between January 2000 and December 2011 that used RSA in the evaluation of hip or knee prosthesis migration. 2 investigators independently evaluated each of the studies for adherence to the 13 individual guideline items. Since some of the 13 points included more than 1 criterion, studies were assessed on whether each point was fully met, partially met, or not met.

RESULTS

153 studies that met our inclusion criteria were identified. 61 of these were published before the guidelines were introduced (2000-2005) and 92 after the guidelines were introduced (2006-2011). The methodological quality of RSA studies clearly improved from 2000 to 2011. None of the studies fully met all 13 guidelines. Nearly half (43) of the studies published after the guidelines demonstrated a high methodological quality and adhered at least partially to 10 of the 13 guidelines, whereas less than one-fifth (11) of the studies published before the guidelines had the same methodological quality. Commonly unaddressed guideline items were related to imaging methodology, determination of precision from double examinations, and also mean error of rigid-body fitting and condition number cutoff levels.

INTERPRETATION

The guidelines have improved methodological reporting in RSA studies, but adherence to these guidelines is still relatively low. There is a need to update and clarify the guidelines for clinical hip and knee arthroplasty RSA studies.

Influence of cooling on curing temperature distribution during cementing of modular cobalt-chromium and monoblock polyethylene acetabular cups

Total hip replacements for older patients are usually cemented to ensure high postoperative primary stability. Curing temperatures vary with implant material and cement thickness (30°C to 70°C), whereas limits for the initiation of thermal bone damage are reported at 45°C to 55°C. Thus, optimizing surgical treatment and the implant material are possible approaches to lower the temperature. The aim of this study was to investigate the influence of water cooling on the temperature magnitude at the acetabulum cement interface during curing of a modular cobalt-chromium cup and a monoblock polyethylene acetabular cup. The curing temperature was measured for SAWBONE and human acetabuli at the cement-bone interface using thermocouples. Peak temperature for the uncooled condition reached 70°C for both cup materials but was reduced to below 50°C in the cooled condition for the cobalt-chromium cup (P = .027). Cooling is an effective method to reduce curing temperature with metal implants, thereby avoiding the risk of thermal bone damage.

Precision and accuracy measurement of radiostereometric analysis applied to movement of the sacroiliac joint

BACKGROUND

Different techniques have been used to quantify the movement of sacroiliac (SI) joints. These include radiostereometric analysis (RSA), but the accuracy and precision of this method have not been properly evaluated and it is unclear how many markers are required and where they should be placed to achieve proper accuracy and precision.

PURPOSE

The purpose of this study was to test accuracy and precision of RSA, applied to the SI joint, in a phantom model and in patients.

METHODS

We used a plastic phantom attached to a micrometer to obtain a true value of the movement of the SI joint and compared this value with the measured value obtained by RSA; the difference represented the accuracy. The precision of the system was measured by double examination in the phantom and in six patients, and was expressed by a limit of significance (LOS). We analyzed different marker distributions to find optimal marker placement and number of markers needed.

RESULTS

The accuracy was high and we identified no systematic errors. The precision of the phantom was high with a LOS less than 0.25° and 0.16 mm for all directions, and in patients, the precision was less than 0.71° for rotations and 0.47 mm translations. No markers were needed in the pubic symphysis to obtain good precision.

CONCLUSIONS

The accuracy and precision are high when RSA is used to measure movement in the SI joint and support the use of RSA in research of SI joint motion.

The migration pattern of the Charnley femoral stem: a five-year follow-up RSA study in a well-functioning patient group

BACKGROUND

Implant stability is considered vital to long-time implant survival in total hip arthroplasty (THA), since loose implants are reported to be a major cause of hip revision. There is an association between early implant micromotion and increased risk of revision. More implant-specific data are needed to establish acceptable levels of early implant movement.

MATERIALS AND METHODS

Thirty-five patients (36 hips) undergoing Charnley THA were followed with repeated clinical, radiographic, and radiostereometric analysis (RSA) over 5 years. Twenty-three patients attended 5 years postoperatively.

RESULTS

The patient group was well functioning based on the radiological and clinical evaluations. The stems constantly moved up to 5 years postoperatively, with subsidence, retroversion, and varus tilt, based on the RSA.

CONCLUSION

Continuous movement of the Charnley stem was observed up to 5 years postoperatively in a well-functioning patient group. The migration data presented herein could be useful when defining acceptable migration limits for certain types of cemented femoral stems.

The effect of adding tobramycin to Simplex P cement on femoral stem micromotion as measured by radiostereometric analysis: a 2-year randomized controlled trial

BACKGROUND

Previous in vitro research on addition of antibiotics to bone cement has found no statistically significant deterioration in mechanical properties. However, no clinical studies have compared the performance of tobramycin-laden bone cement with that of standard bone cement (Simplex P).

PATIENTS AND METHODS

23 patients (25 hips) were randomized to receive an Exeter (Stryker Orthopaedics) femoral stem cemented with either Simplex P (standard) or Simplex T (tobramycin-laden) cement. There were 2 years of follow-up, with scheduled radiostereometric (RSA) examinations.

RESULTS

All stems migrated distally and showed some degree of retroversion. No clinically significant differences in stem subsidence or retroversion were found between the Simplex T and Simplex P cement groups after 2 years. Overall subsidence was less than in previous studies, probably due to a postponed initial post-surgical examination. Rates of subsidence in both cement groups were consistent with those from previous studies of Exeter stems.

INTERPRETATION

Subsidence of the femoral stem after 2 years was similar in the Simplex T (tobramycin-laden) and Simplex P (standard) groups.

A randomized study on migration of the Spectron EF and the Charnley flanged 40 cemented femoral components using radiostereometric analysis at 2 years

BACKGROUND AND PURPOSE

We performed a randomized study to determine the migration patterns of the Spectron EF femoral stem and to compare them with those of the Charnley stem, which is regarded by many as the gold standard for comparison of implants due to its extensive documentation.

PATIENTS AND METHODS

150 patients with a mean age of 70 years were randomized, single-blinded, to receive either a cemented Charnley flanged 40 monoblock, stainless steel, vaquasheen surface femoral stem with a 22.2-mm head (n = 30) or a cemented Spectron EF modular, matte, straight, collared, cobalt-chrome femoral stem with a 28-mm femoral head and a roughened proximal third of the stem (n = 120). The patients were followed with repeated radiostereometric analysis for 2 years to assess migration.

RESULTS

At 2 years, stem retroversion was 2.3° and 0.7° (p < 0.001) and posterior translation was 0.44 mm and 0.17 mm (p = 0.002) for the Charnley group (n = 26) and the Spectron EF group (n = 74), respectively. Subsidence was 0.26 mm for the Charnley and 0.20 mm for the Spectron EF (p = 0.5).

INTERPRETATION

The Spectron EF femoral stem was more stable than the Charnley flanged 40 stem in our study when evaluated at 2 years. In a report from the Norwegian arthroplasty register, the Spectron EF stem had a higher revision rate due to aseptic loosening beyond 5 years than the Charnley. Initial stability is not invariably related to good long-term results. Our results emphasize the importance of prospective long-term follow-up of prosthetic implants in clinical trials and national registries and a stepwise introduction of implants.

Functioning and disability in patients with hip osteoarthritis with mild to moderate pain

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To compare functioning and disability in patients with hip osteoarthritis (OA) not candidates for surgery, to a matched control group, and thereby to examine the relationship between the functioning and disability components used in this study in patients with hip OA.

BACKGROUND

It is well known that patients with severe hip OA have deficits in functioning and disability. However, in patients with hip OA not candidates for surgery, the knowledge regarding functioning and disability is sparse.

METHODS

Twenty-six patients (12 men, 14 women; mean age, 60 years) with radiographic and symptomatic hip OA were matched to 26 controls without hip pain. The following variables were measured: muscle strength using isokinetic peak force, hip passive range of motion, submaximal aerobic capacity using a cycling test, walking ability using the 6-minute walk test, self-reported pain, stiffness, and physical function using the Western Ontario and McMaster University Osteoarthritis Index, and health-related quality of life using the SF-36.

RESULTS

The patients with hip OA had mild to moderate pain, as indicated by the Western Ontario and McMaster University Osteoarthritis Index, and significantly lower knee extension strength (mean difference [95% confidence interval {CI}]: -19.5 [-34.3, -4.7] Nm). Hip range of motion was significantly less in the patients with hip OA, with mean (95% CI) differences of -10° (-14°, -6°) for extension, -18° (-26°, -11°) for flexion, -9° (-14°, -4°) for abduction, -2° (-5°, 0°) for adduction, -16° (-23°, -9°) for internal rotation, and -21° (-28°, -14°) for external rotation. The patients with hip OA walked a significantly shorter distance in 6 minutes (mean difference, -75 m; 95% CI: -131, -20 m). There were no significant differences in hip extension/flexion, knee flexion, ankle dorsiflexion/plantar flexion muscle strength, or aerobic capacity between the 2 groups. There were significant associations between body function and activity components.

CONCLUSION

Physical therapists should consider including quadriceps-strengthening and hip range-of-motion exercises when developing rehabilitation programs for patients with hip OA, with mild to moderate pain, aiming to improve functioning and reduce disability.

A prospective randomised radiostereometric analysis trial of SmartSet HV and Palacos R bone cements in primary total hip arthroplasty

Background

Introduction of new bone cements into clinical practice should include radiostereometric studies.

Materials and methods

A prospective randomised radiostereometric study was performed, comparing SmartSet HV and Palacos R acrylic bone cements (without antibiotics) using third-generation cementing techniques in primary total hip arthroplasty. Thirty-five patients (36 hips) undergoing Charnley total hip arthroplasty were randomised to receive either of the two cements and were followed with repeated clinical, radiographic and radiostereometric examinations over 24 months. Twenty-seven patients (28 hips) attended 2 years postoperatively.

Results

The mean distal translation observed was −0.15 mm for SmartSet HV and −0.16 mm for Palacos R. The mean rotation around the longitudinal axis was 0.9° for SmartSet HV and 1.2° for Palacos R. The Merle d’Aubigne Postel score was the maximum of 18 points for all patients in both groups.

Conclusions

No statistically significant difference in stem fixation with use of SmartSet HV and Palacos R was found at 2-year follow-up.

Orthopaedic bone cement: do we know what we are using?

Bone cements produced by different manufacturers vary in their mechanical properties and antibiotic elution characteristics. Small changes in the formulation of a bone cement, which may not be apparent to surgeons, can also affect these properties. The supplier of Palacos bone cement with added gentamicin changed in 2005. We carried out a study to examine the mechanical characteristics and antibiotic elution of Schering-Plough Palacos, Heraeus Palacos and Depuy CMW Smartset bone cements. Both Heraeus Palacos and Smartset bone cements performed significantly better than Schering-Plough Palacos in terms of mechanical characteristics, with and without additional vancomycin (p < 0.001). All cements show a deterioration in flexural strength with increasing addition of vancomycin, albeit staying above ISO minimum levels. Both Heraeus Palacos and Smartset elute significantly more gentamicin cumulatively than Schering-Plough Palacos. Smartset elutes significantly more vancomycin cumulatively than Heraeus Palacos. The improved antibiotic elution characteristics of Smartset and Heraeus Palacos are not associated with a deterioration in mechanical properties. Although marketed as the 'original' Palacos, Heraeus Palacos has significantly altered mechanical and antibiotic elution characteristics compared with the most commonly-used previous version.

Selfprotective smart orthopedic implants

In this review, we discuss current advances leading to an exciting change in implant design for orthopedic surgery. The initial biomaterial approaches in implant design are being replaced by cellular-molecular interactions and nanoscale chemistry. New designs address implant complications, particularly loosening and infection. For infection, local delivery systems are an important first step in the process. Selfprotective 'smart' devices are an example of the next generation of orthopedic implants. If proven to be effective, antibiotics or other active molecules that are tethered to the implant surface through a permanent covalent bond and tethering of antibiotics or other biofactors are likely to transform the practice of orthopedic surgery and other medical specialties. This new technology has the potential to eliminate periprosthetic infection, a major and growing problem in orthopedic practice.