Metal ion levels in ceramic-on-ceramic THR with modular necks: analysis of cobalt and chromium serum levels in 30 healthy hip patients

Prospective clinical study using radiostereometric analysis (RSA) to evaluate fixation of a modular cemented polished femoral stem

BACKGROUND

The long-term clinical success of cemented polished tapered femoral components has been demonstrated in prospective as well as registry studies. This stem design type has also been well studied with radiostereometric analysis (RSA) and provides a standard to evaluate alternative designs of polished tapered cemented femoral components. This prospective study evaluates the subsidence of a polished cemented stem with a modular neck design utilising RSA.

METHODS

26 patients were prospectively enrolled in the study and 23 were available for RSA analysis at 2 years.

RESULTS

The average subsidence of the femoral implant was 1.1 mm (SD 0.4 mm) at 2 years post operation. There were no revisions in this group, specifically no failures of the modular stem-neck design as has been seen with other implants.

CONCLUSIONS

The RSA subsidence pattern at 2 years of this cemented femoral stem is similar to other successful designs with long-term follow-up. The implications over time of stem neck modularity for cemented polished tapered femoral components requires further evaluation.

Catastrophic failure of femoral stem modular junction when combined with metal-on-metal bearing in comparison to ceramic-on-ceramic: A retrospective cohort study

BACKGROUND

Metal ion release from total hip arthroplasty's (THA) metal-on-metal (MoM) bearing surfaces or head-neck modular junction (trunnionosis) has been identified as a major cause of adverse reaction to metal debris (ARMD). No study has compared the effects of these bearing couples when combined with modular neck femoral stems (MNFS) (i.e. did a modular CoCr have a higher effect than large MoM bearings on whole blood ion concentrations and ARMD). Therefore we did a retrospective comparative analysis of prospectively collected data aiming to: (1) assess the difference in metal ion release between a group of MoM and CoC bearings implanted with a non-cemented MNFS; (2) compare the ARMD and the related revision rates between the two bearing types; (3) compare the patients' HOOS and Harris Hip scores.

HYPOTHESIS

Metal ion levels and complications rate will be higher in MoM group.

METHODS

Thirty hips received the same short MNFS with modular CoCr. Seventeen had CoC bearing (16=36mm) and 13 large diameter head (LDH) MoM bearing (mean=50mm, 44-54mm) Both groups had whole blood Cobalt (Co) and Chromium (Cr) concentrations measurements at last follow up or before revision surgery (if any) and were compared to 41 control individuals without implants. ARMD, revision rates and other complications were censed. Functional outcome differences between operative groups were assessed with HOOS and Harris Hip scores.

RESULTS

Mean whole blood Co and Cr were 1.9μg/L (0.1-10.6 min-max) and 1.2μg/L (0.2-4.6 min-max) in the CoC group and 12.7μg/L (2.5-40.7 min-max) and 8.2μg/L (2.8-40.6 min-max) for MoM group. Controls presented whole blood Co and Cr levels of 0.2μg/L (0.04-0.2 min-max) and 0.6μg/L (0.1-0.7 min-max) respectively. CoC had significantly higher whole blood metal ion concentrations than controls, while MoM had significantly higher concentrations than both (p<0.001). MoM had a 9/13 (69%) revision rate due to ARMD (with stem-neck junction corrosion and wear were present in all cases) while the CoC had none. Functional scores at last follow up did not statistically differ between groups (Harris: CoC=94.1±8.4 vs MoM 91.8±14.8 (p=0.22) and CoC HOOS 90.2±10.7 vs 75.6±21.7 (p=0.08)).

CONCLUSION

In our study, MNFS with CoCr modular neck released metal ion systemically, as shown in CoC THAs, but when combined with MoM LDH bearings, that elevation was significantly higher. In MNFS MoM, these high metal ion levels translated into a dramatic ARMD related revision rate where stem-neck junction corrosion and wear were present in all cases. More research is required to understand the effects of MoM bearing on neck-stem junctions, and its mechanisms of corrosion.

LEVEL OF EVIDENCE

III; retrospective comparative study.

Modular junction may be more problematic than bearing wear in metal-on-metal total hip arthroplasty

INTRODUCTION

In total hip arthroplasty (THA), local adverse reaction to metal debris (ARMD) may be caused by abnormal metal ion release from a metal-on-metal (MoM) bearing, or by wear and corrosion of the implant's modular junction. The aim of this study was to compare ion levels and rate of ARMD between patients sharing the same MoM bearing but 1 group having monoblock stems versus another having modular stems.

MATERIALS AND METHODS

Whole blood cobalt (Co) and chromium (Cr) ion concentrations, ARMD rate, revision rate, and function measured by UCLA and WOMAC scores were compared between groups.

RESULTS

ARMD rate was significantly higher in the modular group (46%) compared with the monoblock group (16%, p = 0.031). Revision for ARMD was performed at 52.8 ± 8.1 months in the modular group versus 98.2 ± 15.5 months after primary THA in the monoblock group. ARMD originated from wear and corrosion of the junction between stem and femoral head adapter sleeve in all monoblock cases, and the junction between stem and modular neck in all the modular ones. Cr and Co ions levels were significantly higher in the modular stem group ( p < 0.001 for both).

CONCLUSIONS

Although both groups had MoM bearings, corrosion at stem/neck or neck/head junctions combining dissimilar metal (Ti and Cr-Co) was seen as the source of excess metal ions release leading to ARMD. Poor performance of the modular junction may be more deleterious than wear of the bearing. To avoid such complications, THA femoral stem modular junctions should be eliminated (return to a full monoblock implant) or have improved junction design.

Withdrawn: A Randomized Controlled Trial Comparing Modular and Nonmodular Neck Versions of a Titanium Stem

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Effect of Femoral Stem Modular Neck's Material on Metal Ion Release

Background:

In recent decades, the popularity of modular necks in total hip arthroplasty (THA) has increased since modular necks offer the potential to restore the patient’s native anatomy, and thus improve stability. Unfortunately, modular necks are associated with higher complication rates, including implant fracture and modular junction corrosion with adverse local tissue reaction to metal debris.

Objective:

The objective of this study was to determine the impact of modular neck material on titanium (Ti), chrome (Cr), and cobalt (Co) metal ion levels in patients who underwent a THA with Ti femoral stem, Ti or CrCo modular neck, and ceramic-on-ceramic (CoC) bearing.

Methods:

Whole blood Ti, Cr, and Co levels were compared at a minimum 1-year follow-up in 36 patients who underwent unilateral, primary CoC large-diameter head THA with Profemur^® Preserve modular femoral stems (MicroPort, Arlington, TX, USA).

Results:

Higher Co concentrations were observed in the CrCo modular neck group (0.46 versus 0.26 µg/l in the Ti neck group, P=0.004) and higher Ti concentrations were observed in the Ti modular neck group (1.98 vs 1.59 µg/l in the CrCo neck group, P=0.007). However, these differences were not clinically meaningful since the absolute values remained within what is considered the safe range of Ti, Cr, and Co ions in whole blood. No patients were re-operated or revised.

Conclusion:

Modular neck materials had an impact on whole blood metal ion levels but the concentrations measured remained within the safe range at 1-year follow-up. There were no indirect signs of modular junction corrosion with either CrCo or Ti femoral necks.

Excellent mid-term results of a new polished tapered modular cemented stem: a study of 113 hip replacements with minimum 5-year follow-up

BACKGROUND

This prospective cohort study reports the medium-term clinical and radiographic results of 113 hips treated with a hybrid total hip replacement (THR) with a new cemented tapered cobalt-chrome (Co-Cr) stem with a titanium (Ti) modular neck (ProfemurXm®).

METHOD

Between October 2008 and December 2010 we performed 115 consecutive hybrid THR with the ProfemurXm® in 105 patients.

RESULTS

Survivorship of the implant (stem and modular neck) at a mean of 6.5 years (min 5-max 8) was 100% with the endpoint revision for any reason. No implant was at risk for revision or showed signs of loosening. The mean Harris Hip Score was 89/100, mean Oxford Hip Score was 43/48, mean WOMAC was 91/100. No patient had thigh pain, no patient reported squeaking. There were no dislocations in this cohort. No implant showed development of radiolucent lines (RLL), either at the stem-cement or cement-bone interface. No hip showed osteolysis or calcar resorption. The mean femoral subsidence of the stem within the cement mantel was 0.31 mm (range 0-0.6 mm) after 6.5 years. With the use of this modular stem, 93% of hips showed no measurable leg length difference after THR, and leg length could be restored within a 5-mm limit in 99% of hips.

CONCLUSIONS

The mid-term results of this new polished stem were excellent, without adverse effects from the use of modularity.

Metal ion levels in ceramic-on-ceramic THR with cobalt-chrome modular necks: analysis of cobalt and chromium serum levels in 23 healthy hip patients

BACKGROUND

Modular necks in total hip replacement (THR) can be a source of metal ion release.

METHODS

We measured the level of cobalt (Co) and chromium (Cr) ions in the serum of 23 healthy volunteers with a well-functioning ceramic-on-ceramic THR of a particular design, containing a cobalt-chrome (Co-Cr) stem and a Co-Cr modular neck.

RESULTS

Average Co in serum was 1,71 µg/l; median Co was 1.50 µg/l. No patient had Co levels higher than 3.70 µg/l. Average Cr level was 0.49 µg/l; in all but one patient Cr was below the detection limit (<0.50 µg/l). Co was higher for varus necks compared to all other subtypes: 2.14 µg/l vs 1.58 µg/l (p<0.05). The same system with Titanium modular necks shows lower Co serum levels: 1.26 µg/l (p<0.01 ). In conclusion, the hybrid THR Profemur Xm® - Procotyle L® with a Co-Cr modular neck on a Co-Cr stem design shows very low Cr ion serum levels in a randomly selected group of well-functioning hip patients.

CONCLUSIONS

Co ion serum levels are low, but significantly higher for 8° varus necks, and Co levels are significantly higher than values of this system with a Titanium modular neck.

Asymptomatic Pseudotumors in Patients with Taper Corrosion of a Dual-Taper Modular Femoral Stem: MARS-MRI and Metal Ion Study

BACKGROUND

Modularity in total hip arthroplasty facilitates intraoperative restoration of patient anatomy. Although dual-taper modular total hip arthroplasty offers potential advantages for optimizing the hip center of rotation, it has been associated with modular taper corrosion. This corrosion has led to adverse local tissue reactions (pseudotumors) at the neck-stem junction and elevated metal-ion levels. However, the occurrence of taper-corrosion-related pseudotumors in patients who remain asymptomatic following total hip arthroplasty with a dual-taper modular femoral stem remains largely unknown. The aims of this study were (1) to determine the prevalence of asymptomatic pseudotumors by utilizing metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) and (2) compare serum metal-ion levels between symptomatic and asymptomatic patients with a dual-taper modular stem total hip replacement.

METHODS

We performed a retrospective cross-sectional study of 97 consecutive patients who had been treated with a dual-taper modular femoral stem total hip arthroplasty. Eighty-three patients were stratified into symptomatic and asymptomatic groups and evaluated with MARS-MRI, measurement of serum metal-ion levels, and the University of California at Los Angeles (UCLA) functional hip score.

RESULTS

The prevalence of pseudotumors as determined with MARS-MRI was 15% in our asymptomatic patients and 36% in the overall cohort. The median serum cobalt level and cobalt/chromium ratio were significantly higher in patients with a pseudotumor than in those without a pseudotumor (8.0 versus 2.0 μg/L [p = 0.004] and 10.3 versus 2.4 μg/L [p = 0.012], respectively). However, there was no significant difference in the serum cobalt level or cobalt/chromium ratio between symptomatic patients with a pseudotumor and asymptomatic patients with a pseudotumor (7.6 versus 6.2 μg/L [p = 0.37] and 8.3 versus 10.6 μg/L [p = 0.46], respectively). The UCLA scores of asymptomatic patients with a pseudotumor were similar to those of patients without a pseudotumor (6.7 versus 6.6).

CONCLUSIONS

The prevalence of asymptomatic taper-corrosion-related pseudotumors on MARS-MRI in this study demonstrated that the absence of symptoms does not exclude the presence of adverse local tissue reactions. Elevated cobalt levels and cobalt/chromium ratios were associated with the presence of pseudotumors in asymptomatic and symptomatic patients. Cross-sectional imaging such as MARS-MRI is indicated for patients with elevated metal-ion levels. A longitudinal study is required to determine whether asymptomatic patients with taper-corrosion-related pseudotumors will develop symptoms with time.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

High serum ion levels in Conserve Plus big femoral head cemented total hip arthroplasty

AIM

We report the short-term clinical, radiographic and ion level data of the Conserve Plus metal-on-metal (MoM) big femoral head (BFH) total hip arthroplasty (THA), used with a cemented cobalt-chrome (Co-Cr) Profemur Xm stem and a titanium (Ti) modular neck.

RESULTS

In a consecutive series of 40 hips, survivorship at 3 years was 92.5% with revision for any reason. Average Harris Hip Score was 91.3. There were no implant loosenings. No osteolysis was observed. 5 patients had signs of adverse local tissue reaction (ALTR); their clinical scores were not different from the whole cohort. All but 1 patient had their Co serum ion levels measured. The average Co level was 14,1 µg/l (range 0.9-29.0; median 13.0 µg/l). Clinical scores did not correlate with ion level data. A comparative group of 42 hip resurfacing arthroplasties from the same manufacturer had significantly lower serum Co levels: 1.51 µg/l (range 0.9-4.0; median 0.9 µg/l).

CONCLUSIONS

All patients with the MoM BFH THA design should be followed regularly and should have ion level testing.