Alternate bearing surfaces in total joint arthroplasty: biologic considerations

An overview of the tribological and mechanical properties of PEEK and CFR-PEEK for use in total joint replacements

Poly-ether-ether-ketone (PEEK) and PEEK composites are outstanding candidates for biomedical applications, such as orthopedic devices, where biocompatibility and modulus match with surrounding tissue are requisite for long-term success. The mechanical properties can be optimized by incorporating fillers such as continuous and chopped carbon fibers. While much is known about the mechanical and tribological behavior of PEEK composites, there are few articles that summarize the viability of using PEEK reinforced with carbon fibers in orthopedic implants. This paper reviews biocompatibility, tribological, and mechanical studies on PEEK and their composites with carbon fibers, notably PEEK reinforced with polyacrylonitrile (PAN)-based carbon fibers and PEEK reinforced with pitch-based carbon fibers, for application in orthopedics and total joint replacements (TJRs). The main objectives of this review are two-fold. Firstly, this paper aims to assist designers in making informed decisions on the suitability of using PEEK and PEEK composites in orthopedic applications; as it is not well understood how these materials perform on the whole in orthopedics and TJRs. Secondly, this paper aims to serve as a centralized paper in which researchers can gain information on the tribological and mechanical advancements of PEEK and PEEK composites.

Can Patients With Metal Hypersensitivity Requiring TMJ Total Joint Prostheses be Successfully Treated With All-Titanium Alloy Mandibular Components?

PURPOSE

Patients with documented metal hypersensitivity to cobalt-chromium-molybdenum (CoCrMo) alloy with trace nickel requiring TMJ total joint prosthesis (TJP) may have adverse reactions to the metals in the standard TMJ Concepts TJP. This study aimed to determine if these patients can be successfully treated by eliminating CoCrMo alloy and constructing the mandibular components of all-titanium (Ti) alloy.

PATIENTS AND METHODS

This retrospective cohort study evaluated metal hypersensitive patients (MHG) that received the TMJ Concepts TJP modification of all-Ti alloy mandibular components with outcome results compared to a control group (CG) of non-metal-sensitive patients that received the standard TMJ Concepts prostheses. The primary predictor variables were the 2 groups, MHG and CG. Primary variables evaluated using Likert scales included TMJ pain, headache, jaw function, diet, and disability. Maximum incisal opening and quality of life were measured. Secondary variables included: age, gender, effect of the number and type of prior TMJ. Scores for pre- and postsurgery parameters (nonparametric variables) were analyzed using a Mann-Whitney U test (α = 0.05).

RESULTS

The MHG (n = 30) received the Ti alloy TJP and CG (n = 46) received the standard TJP, with statistically significant improvements in all variables in both groups and no statistically significant difference in outcome variables between the 2 groups. Patients with 0 to 1 previous TMJ surgeries had better outcomes in all parameters except maximum incisal opening compared to patients with 2 or more previous TMJ surgeries.

CONCLUSIONS

Patients with documented hypersensitivity to CoCrMo alloy, requiring TMJ Concepts TJP may experience improvement in TMJ pain, headache, jaw function, diet, disability, jaw opening, and quality of life when the mandibular components are manufactured from all-Ti alloy, eliminating the CoCrMo alloy. The larger the number of previous TMJ surgeries and exposure to failed alloplastic implants, the less improvement in treatment outcomes.

BLOOD CHROMIUM-COBALT LEVELS IN PATIENTS AFTER TOTAL KNEE ARTHROPLASTY AND THEIR EFFECT ON THE RETINAL NERVE FIBER LAYER AND MACULAR GANGLION CELL COMPLEX

PURPOSE

To study blood cobalt (Co) and chromium (Cr) levels in patients who have undergone total knee arthroplasty and their effect on the retinal nerve fiber layer and macular ganglion cell complex.

METHODS

One hundred patients who had undergone total knee arthroplasty and 50 healthy individuals who had no implants were included in the study. The patients were separated into two groups based on how long ago the prosthesis had been implanted (Group 1: 1 to 5 years; Group 2: 5 to 10 years). After a complete ophthalmological examination, retinal nerve fiber layer and macular ganglion cell complex of the patients were evaluated with optical coherence tomography, performed on dilated pupils. To assess the metal ion levels of the patients, venous blood samples were drawn from each patient.

RESULTS

The mean age of the patients was 64.72 ± 6.26 years in Group 1, 67.80 ± 8.07 years in Group 2, and 63.42 ± 7.90 years in the control group. In the comparison of age and sex, there were no statistically significant differences between the groups and the control group. Co and Cr levels were statistically higher in Group 1 and Group 2 compared with the control group (P < 0.001). Mean retinal nerve fiber layer thicknesses and mean macular ganglion cell complex thicknesses in Group 1 and Group 2 were statistically lower than in the control group.

CONCLUSION

Levels of Co and Cr are higher in patients who undergone total knee arthroplasty than healthy subjects, and these higher levels were associated with changes in the retinal nerve fiber layer and macular ganglion cell complex.

Periprosthetic Osteolysis in Cervical Total Disc Arthroplasty: A Single Institutional Experience

BACKGROUND

Cervical disc arthroplasty (CDA) affords an excellent alternative to cervical fusion for the treatment of symptomatic patients with degenerative disc disease. As more surgeons perform CDAs, an understanding of the complications associated with this technique is crucial. Periprosthetic osteolysis (PO) is a rare potential complication associated with CDA.

OBJECTIVE

To highlight potential complications associated with CDA.

METHODS

A retrospective chart review of patients who underwent CDA at our institution was performed. Patient outcomes and relevant clinical and radiographical data were analyzed in addition to associated complications. Explanted devices were subjected to macroscopic and microscopic analyses.

RESULTS

A total of 88 patients were included: 68 patients underwent 1-level CDA and 20 patients had 2-level CDA. Implants used in this series included Mobi-C (Zimmer Biomet), Prestige LP (Medtronic), Secure C (Globus), Advent (Orthofix), and ProDisc C (DePuy). One patient demonstrated symptoms of myeloradiculopathy that correlated with radiographical periprosthetic osteolysis and required surgical intervention in the form of disc explantation, corpectomy, and cervical instrumented fusion. Device retrieval analysis demonstrated evidence of elevated oxidation levels and increased wear in the presence of high concentrations of metal ions and debris in the surrounding tissue. The tissue did not exhibit any immune response, infection, or acute inflammation.

CONCLUSION

PO is a potential complication of CDA that occurs irrespective of the type of implant used. We describe its occurrence and management and highlight the importance of being aware of this understated phenomenon.

Comparative Analysis between Short Stem and Conventional Femoral Stem in Patients with Osteonecrosis of Femoral Head: Metha Stem and Excia Stem

Objective

To compare the intraoperative, radiological, and clinical short‐term outcomes of cementless total hip arthroplasties (THA) using a short stem (SS) and a conventional femoral stem (CS) in a randomized prospective control study.

Methods

From June 2011 to October 2017, patients who underwent cementless THA for idiopathic osteonecrosis of the femoral head were recruited. Patients had a minimum 2 years of follow‐up after the operation. The patients were divided into two groups: those who underwent THA using an SS and those who underwent THA using a CS. SS were used in 34 patients (41 hips) and CS were used in 41 patients (45 hips). In both groups, the same cup was used in all cases, and the mean follow‐up periods were 63 (26–101) months in the SS and 64 (26–101) months in the CS groups. Intraoperative, clinical, and radiological evaluations were performed for the two groups.

Results

There was no difference in the demographics of the two groups. There was one patient with a proximal femoral crack in the SS group and one with a distal femoral crack in the CS group. Clinically, the mean Harris hip score was improved in both groups at 2‐year follow‐up. Radiographically endosteal osseointegrations were found in 40 of 41 cases in the SS group and in 44 of 45 cases in the CS group. There was one case of dislocation in each group. In the SS group, the acetabular cup was changed and repositioned 7 months after the initial operation. Stem loosening, infection, ceramic breakage, and varus/valgus change were not observed. There was a statistically significant lower stress shielding effect in the SS group. There were no differences in vertical/parallel offset and leg length discrepancy.

Conclusion

The intraoperative, radiological, and clinical evaluations in both groups showed good outcomes and there was no statistically significant difference between the two groups.

Revision Total Hip Arthroplasty after Ceramic Bearing Fractures in Patients Under 60-years Old; Mid-term Results

Purpose

Although advances in technology have reduced the risk of ceramic implant fractures in total hip arthroplasty, these injuries do occur and their treatment remains challenging. There is a lack of studies reporting on the effectiveness of ceramic components in revision hip arthroplasty after ceramic bearing fracture. The aim of this study is to evaluate clinical and radiologic outcomes of revision surgery with ceramic-on-ceramic components after ceramic bearing fractures in young (i.e., under 60 years old) and active patients.

Materials and Methods

Eight patients who, from May 2004 to November 2011, underwent ceramic-on-ceramic revision surgery following a ceramic component fracture and had more than 6 years follow up were enrolled in this study. All eight patients were male with mean ages at first and revision surgeries of 39 years (range, 31–50 years) and 43.8 years (range, 33–60 years), respectively. There were 6 and 2 cases of ceramic liner and ceramic head fractures, respectively. The average time from the first operation to revision surgery was 54.3 months (range, 9–120 months), and the average follow up period was 9.7 years (range, 6–13.3 years).

Results

At the last follow up, all patients showed improvement in Harris hip score and pain relief and there were no cases of loosening or osteolysis.

Conclusion

Revision total hip arthroplasty using ceramic-on-ceramic components after ceramic component fracture is a feasible and appropriate surgical option in young and active patients.

3rd generation ceramic-on-ceramic cementless total hip arthroplasty: a minimum 10-year follow-up study

INTRODUCTION

3^rd generation ceramic bearings were introduced in total hip arthroplasty (THA) with the potential to have better mechanical strength and wear properties than their predecessors. At present, there are few studies looking at the long-term results of this latest generation of ceramic bearings. The purpose of our study was to investigate the long-term clinical and radiographic results of 3^rd generation ceramic-on-ceramic THA and the incidence of ceramic specific complications such as squeaking and bearing surface fracture.

METHODS

The database of the senior author (J.D.W.) was reviewed. A total of 126 hip replacements performed in 108 patients (average age 39.6 years) with an average follow-up of 12.1 years (10-16 years) was identified. Clinical notes and plain radiographs were reviewed. To measure function, patients were contacted and an Oxford Hip Questionnaire was completed. Patients were also directly questioned about the presence of squeaking or any other sounds from the hip. Radiographs were evaluated for signs of wear, osteolysis, loosening and heterotopic ossification. The abduction angle of the acetabular component was measured.

RESULTS

The average Oxford Hip Score was 39.8 out of 48. Survivorship at 10 years was 94.6% (95% CI) with revision for any cause as the endpoint. There was 1 femoral head fracture, no osteolysis, no squeaking and no detectable wear.

CONCLUSIONS

The good clinical and radiographic results for this series of patients are similar to other recent long-term studies looking at 3^rd generation ceramic-on-ceramic THA. The results compare favourably with other bearing surfaces. The lack of osteolysis associated with this articulation is encouraging and may also make it a good choice for younger patients requiring total hip replacement.

3rd generation ceramic-on-ceramic cementless total hip arthroplasty: a minimum 10-year follow-up study

INTRODUCTION

3rd generation ceramic bearings were introduced in total hip arthroplasty (THA) with the potential to have better mechanical strength and wear properties than their predecessors. At present, there are few studies looking at the long-term results of this latest generation of ceramic bearings.The purpose of our study was to investigate the long-term clinical and radiographic results of 3rd generation ceramic-on-ceramic THA and the incidence of ceramic specific complications such as squeaking and bearing surface fracture.

METHODS

The database of the senior author (J.D.W.) was reviewed. A total of 126 hip replacements performed in 108 patients (average age 39.6 years) with an average follow-up of 12.1 years (10-16 years) was identified. Clinical notes and plain radiographs were reviewed. To measure function, patients were contacted and an Oxford Hip Questionnaire was completed. Patients were also directly questioned about the presence of squeaking or any other sounds from the hip. Radiographs were evaluated for signs of wear, osteolysis, loosening and heterotopic ossification. The abduction angle of the acetabular component was measured.

RESULTS

The average Oxford Hip Score was 39.8 out of 48. Survivorship at 10 years was 94.6% (95% CI) with revision for any cause as the endpoint. There was 1 femoral head fracture, no osteolysis, no squeaking and no detectable wear.

CONCLUSIONS

The good clinical and radiographic results for this series of patients are similar to other recent long-term studies looking at 3rd generation ceramic-on-ceramic THA. The results compare favourably with other bearing surfaces. The lack of osteolysis associated with this articulation is encouraging and may also make it a good choice for younger patients requiring total hip replacement.

Incidence of Ceramic Liner Malseating After Ceramic-on-Ceramic Total Hip Arthroplasty Associated With Osteolysis: A 5- to 15-Year Follow-Up Study

BACKGROUND

The aim of our study was to evaluate the clinical and radiographic outcomes of malseating of the acetabular liner in ceramic-on-ceramic total hip arthroplasty (THA).

METHODS

Outcomes for 160 ceramic-on-ceramic THAs, contributed by 116 women and 39 men, were evaluated. Clinical and radiographic measurements were obtained over a 5- to 15-year follow-up for analysis.

RESULTS

Liner malseating was identified in 20% of cases. Outcomes for 32 cases with liner malseating (group A) were compared to outcomes for 128 joints with correct liner seating (group B). The Harris hip score at the last follow-up was 90.1 for group A and 89.6 for group B. Osteolysis was identified in 5 cases in group A (15.6%), compared to 3 cases in group B (P < .001). No significant between-group differences were identified with regard to ceramic fracture, audible squeaking, loosening of components, and revision THA. The mean annual liner wear rate was comparable between groups, 0.0045 mm/y for group A and 0.0039 mm/y for group B. The 10-year Kaplan-Meier survivorship, based on an end point of revision THA, was 100% for group A and 99.0% for group B.

CONCLUSION

Over a moderate-length follow-up of 5-15 years, malseating of the acetabular liner was not associated with negative clinical outcomes or THA survivorship. Malseating did increase the incidence of osteolysis, a risk factor for adverse effects. Long-term follow-up studies are needed to fully quantify the effects of malseating of the acetabular liner.

Survivorship Between 2 Different Ceramic-on-Ceramic Total Hip Arthroplasty With or Without a Metal-Backed Titanium Sleeve Bearing: A 5- to 14-Year Follow-Up Study

BACKGROUND

The aim of the study was to compare the clinical and radiographic results of consecutive ceramic-on-ceramic bearings with and without a metal-backed titanium sleeve in patients undergoing total hip arthroplasty.

METHODS

Eighty-five patients (64 women and 21 men; average age 55.2 years) were included in the A group without sleeve while 147 patients (116 women and 31 men; average age 54.2 years) were included in the B group with sleeve. Clinical and radiologic measurements at follow-up (range, 5-14 years; average, 8.1 years) were analyzed.

RESULTS

The mean latest postoperative Harris Hip Score was 89.1 for patients from both groups. One joint (1.2%) in the A group displayed ceramic liner fracture, while no incidences of liner fracture occurred in the B group. Audible squeaking was observed in 1 joint (1.2%) in the A group and 1 (0.7%) in the B group. The mean annual liner rate of wear was 0.0049 and 0.0046 mm/y for the A group and B group, respectively. Three joints in the A group (3.5%) required revision total hip arthroplasty because of individual episodes of aseptic cup loosening, ceramic liner fracture, and infection. One joint in the B group (0.7%) required revision because of progressive osteolysis of the proximal femur. Ten-year Kaplan-Meier survivorship, based on an end point of component loosening and bearing failure, was 97.6% for the A group and 99.3% for the B group.

CONCLUSION

There were no clinical, radiographic, or survivorship differences between groups.

Significantly Lower Wear of Ceramic-on-Ceramic Bearings Than Metal-on-Highly Cross-Linked Polyethylene Bearings: A 10- to 14-Year Follow-Up Study

BACKGROUND

This study aimed to retrospectively compare clinical and radiographic results between consecutive total hip arthroplasties (THAs) using ceramic on ceramic (CoC) and metal-on-highly cross-linked polyethylene (MoP), with >10 years of follow-up.

METHODS

Sixty-seven patients (52 women and 15 men) underwent CoC THA, whereas 81 (67 women and 14 men) underwent MoP THA. The average patient age at the time of surgery was 54.0 years in the CoC group and 54.2 years in the MoP group.

RESULTS

The mean postoperative Harris Hip Scores were 88.9 and 86.4 in the CoC and MoP groups, respectively (P = .063), and the mean annual liner rates of wear were 0.0043 and 0.0163 mm/year, respectively (P < .001). Osteolysis was observed on the femoral side of 1 joint (1.5%) in the CoC group and in 1 (1.2%) acetabular and femoral (1.2%) joint each in the MoP group. Three joints (3.7%) in the MoP group showed aseptic cup loosening, one of which (1.2%) required revision THA because of progression of the loosening. Revision THA was also required in 1 joint (1.5%) in the CoC group because of ceramic fracture. The Kaplan-Meier survival rate at 10 years with implant loosening or revision THA as the end point was 98.5% for CoC and 96.3% for MoP (P = .416).

CONCLUSION

The wear rate of CoC implants was significantly lower than that of MoP implants. Kaplan-Meier survival at 10 years with implant loosening and revision THA as end points did not differ significantly between these implants.

Factors to consider in joint prosthesis systems

In joint reconstruction, the techniques and materials that provide the best outcomes for patients have been debated. The main points of controversy relate to the use of hemiarthroplasties versus total joint prostheses with metal-on-metal versus metal-on-polyethylene articulations. This article investigates these areas as well as the applicability of the techniques and materials and the complications that can occur. Hypersensitivity to materials used in joint prostheses is relatively common but often unrecognized. Although the discussion applies to all joints, the temporomandibular joint (TMJ) is emphasized. For TMJ reconstruction, metal-on-polyethylene articulation in total joint prostheses provides better treatment outcomes than metal-on-metal articulation.

The stepwise introduction of innovation into orthopedic surgery: the next level of dilemmas

The optimum method for the appropriate introduction of innovative technologies into orthopedics is a vital but vexing issue. Compromises in the introduction process are driven by (a) the magnitude of the problem addressed (incidence and severity), (b) the advantages and risks of the proposed solution, and (c) the "universal dilemma," meaning the inherent "gap" between all the nonhuman supporting data and the unknowns of both efficacy and long-term safety in large human usage over many years. Drawing on the data generated and the actual decision tree used in the introduction of a new highly cross-linked polyethylene as a case study, this article illustrates these "subsequent dilemmas."

Influence of prosthetic design on squeaking after ceramic-on-ceramic total hip arthroplasty

Squeaky ceramic-on-ceramic (COC) total hips have received much recent publicity, and implant design may be implicated. We reviewed 270 consecutive COC total hip arthroplasties in 233 patients comparing 4 implant combinations representing 4 manufacturers. A cohort (n = 45) of Stryker Trident acetabular cups paired with Stryker Accolade femoral stems showed a dramatically higher incidence of "problem squeaking"--defined as always audible to others and occurring at least once per week--with a 35.6% incidence of squeaking and 11.1% incidence of problem squeaking. The 3 non-Stryker designs (n = 225) revealed 3.6% squeaking (P < .0001) and 0.44% problem squeaking (P = .006). The Stryker system has a unique design and metallurgy. Our results suggest that although the genesis of squeaking in COC total hips is multifactorial, prosthetic design plays a key role.

Study rationale and protocol: prospective randomized comparison of metal ion concentrations in the patient's plasma after implantation of coated and uncoated total knee prostheses

Background

Any metal placed in a biological environment undergoes corrosion. Thus, with their large metallic surfaces, TKA implants are particularly prone to corrosion with subsequent release of metal ions into the human body which may cause local and systemic toxic effects and hypersensitivity reactions, and increase cancer risk. To address this problem, a new 7-layer zirconium coating developed especially for cobalt-chrome orthopaedic implants was tested biomechanically and found to lower metal ion release.

The purpose of the proposed clinical trial is to compare the metal ion concentration in patients' plasma before and after implantation of a coated or uncoated TKA implant.

Methods/Design

In this randomised controlled trial, 120 patients undergoing primary TKA will be recruited at the Department of Orthopaedic Surgery of the University Hospital in Dresden, Germany, and randomised to either the coated or uncoated prosthesis. Outcome assessments will be conducted preoperatively and at 3 months, 12 months and 5 years postoperatively. The primary clinical endpoint will be the chromium ion concentration in the patient's plasma after 1 and 5 years. Secondary outcomes include cobalt, molybdenum and nickel ion concentrations after 1 and 5 years, allergy testing for hypersensitivity against one of these metals, the Knee Society Score to assess clinical and physical function of the knee joint, the self-assessment Oxford Score and the Short Form 36 quality of live questionnaire.

Discussion

The metal ion concentration in the patient's plasma has been shown to increase after TKA, its eventual adverse effects being widely debated. In the light of this discussion, ways to reduce metal ion release from orthopaedic implants should be studied in detail. The results of this investigation may lead to a new method to achieve this goal.

Trials register

Clinicaltrials registry NCT00862511

Does intraoperative cell salvage remove cobalt and chromium from reinfused blood?

In 12 patients undergoing a revision hip arthroplasty after a failed metal-on-metal primary hip arthroplasty, the effectiveness of intraoperative cell salvage (ICS) in removing metal ions was investigated. Samples of blood collected during surgery were filtered using 2 ICS devices. The samples had the concentrations of cobalt (Co) and chromium (Cr) measured before and after filtration. There was an average reduction of 76.3% for Cr concentration and 78.6% for Co concentration after ICS filtering. The Co-to-Cr ratio before and after filtration was similar. At the present time, these salvage systems should be used with caution in the patient undergoing revision of metal-on-metal bearing surfaces.

Cementless total hip arthroplasty with ceramic-on-ceramic bearing in patients younger than 45 years with femoral-head osteonecrosis

Despite improvements in the quality of alumina ceramics, osteolysis has been reported anecdotally after total hip arthroplasty (THA) with use of a contemporary alumina-on-alumina ceramic bearing. The purpose of this study was to evaluate the clinical and radiographic outcomes of THA using alumina-on-alumina ceramic bearing and to determine osteolysis using radiographs and computed tomographic (CT) scans in young patients. Consecutive primary cementless THA using alumina-on-alumina ceramic bearing were performed in 64 patients (93 hips) who were younger than 45 years of age with femoral-head osteonecrosis. There were 55 men (84 hips) and nine women (nine hips). Average age was 38.2 (range 24-45) years. Average follow-up was 11.1 (range 10-13) years. Preoperative Harris Hip Score was 52.9 (range 22-58) points, which improved to 96 (range 85-100) points at the final follow-up examination. Two of 93 hips (2%) had clicking or squeaking sound. No hip had revision or aseptic loosening. Radiographs and CT scans demonstrated that no acetabular or femoral osteolysis was detected in any hip at the latest follow-up. Contemporary cementless acetabular and femoral components with alumina-on-alumina ceramic bearing couples function well with no osteolysis at a ten year minimum and average of 11.1-year follow-up in this series of young patients with femoral-head osteonecrosis.

The squeaking hip: a phenomenon of ceramic-on-ceramic total hip arthroplasty

BACKGROUND

Early reports on modern ceramic-on-ceramic total hip replacements have demonstrated excellent clinical and radiographic results with few cases of catastrophic failure, which, in the case of earlier designs, often had been caused by implant fracture. Several reports, however, have noted the presence of audible squeaking. The purpose of the present study was to determine the incidence of squeaking in association with the use of this bearing couple.

METHODS

During the period from March 2003 to May 2005, three surgeons performed 159 total hip arthroplasties in 143 patients with use of a ceramic-on-ceramic bearing. One hundred and forty-nine hips (131 patients) were available for review after at least one year of follow-up. These patients were followed prospectively with use of the modified Hospital for Special Surgery hip score and a patient-administered questionnaire. Additionally, a control group of sixty hips (forty-eight patients) with a metal-on-polyethylene bearing was matched to the ceramic group on the basis of age, sex, and body mass index to compare the incidence of squeaking and other noises. Radiographic evaluations were performed according to previously established criteria.

RESULTS

Fourteen (10.7%) of 131 patients described an audible squeak during normal activities. However, squeaking was reproducible clinically in only four patients, and only one patient complained of squeaking before being presented with the questionnaire. The average Hospital for Special Surgery score improved from 19.8 preoperatively to 38.4 at the time of the latest follow-up, indicating excellent clinical results. Ninety-five percent of the patients had a satisfaction score of > or =8 of 10. Three hips dislocated. One of those three hips squeaked and was revised because of recurrent dislocations. One patient was considering revision because of squeaking. In the matched metal-on-polyethylene cohort, there were no cases of squeaking.

CONCLUSIONS

The squeaking hip is a phenomenon that is unique to total hip replacements with hard-on-hard bearings. The incidence of squeaking in association with ceramic-on-ceramic bearings may be higher than previously reported as <1% of the patients in the present study reported this finding before being queried. The causes and implications of squeaking are yet to be determined. The use of hard-on-hard bearings offers many advantages in terms of wear reduction, especially for young and active patients. Nonetheless, patients considering ceramic-on-ceramic bearings should be counseled with regard to this phenomenon.

Serum ion levels after ceramic-on-ceramic and metal-on-metal total hip arthroplasty: 8-year minimum follow-up

Alternative bearing surfaces for total hip arthroplasty, such as metal-on-metal and ceramic-on-ceramic, offer the potential to reduce mechanical wear and osteolysis. In the short and medium term, the second generation of metal-on-metal bearings demonstrated high systemic metal ion levels, whereas ceramic-on-ceramic bearings showed the lowest ones. We aimed to verify whether the long-term ion release in metal-on-metal subjects was still relevant at a median 10-year follow-up, and whether a fretting process at the modular junctions occurred in ceramic-on-ceramic patients and induced an ion dissemination. Serum levels were measured in 32 patients with alumina-on-alumina implants (group A), in 16 subjects with metal-on-metal implants (group B), and in 47 healthy subjects (group C). Group B results were compared with medium-term findings. Cobalt and chromium levels were significantly higher in metal-on-metal implants than in ceramic-on-ceramic ones and controls. Nevertheless, ion levels showed a tendency to decrease in comparison with medium-term content. In ceramic-on-ceramic implants, ion values were not significantly different from controls. Both in groups A and B, aluminum and titanium release were not significantly different from controls. In conclusion, negligible serum metal ion content was revealed in ceramic-on-ceramic patients. On the contrary, due to the higher ion release, metal-on-metal coupling must be prudently considered, especially in young patients, in order to obtain definitive conclusions.

Osteolysis in third-generation alumina ceramic-on-ceramic hip bearings with severe impingement and titanium metallosis

The most common cause of long-term failure of total hip arthroplasty is osteolysis and aseptic loosening secondary to wear debris. Combinations of hard materials such as ceramic-on-ceramic generate smaller volumes of particulate wear debris than traditional combinations such as metal-on-polyethylene. We describe 2 cases where osteolysis arose in hips with third-generation alumina ceramic-on-ceramic couplings. Periarticular tissue in both cases contained titanium wear debris due to impingement of the neck of the titanium femoral component against the rim of the titanium shell and ceramic debris from edge loading wear (stripe wear) of the ceramic. It is not clear whether the titanium debris, the ceramic debris, or both caused the osteolysis. These cases illustrate that the risk of osteolysis persists, even with third-generation alumina ceramics.

Characterization of a highly cross-linked ultrahigh molecular-weight polyethylene in clinical use in total hip arthroplasty

This article reports on a commercially available extensively cross-linked ultrahigh molecular-weight polyethylene (HXPE) produced by subjecting molded GUR 1050 ultrahigh molecular-weight polyethylene (UHMWPE) to 100 +/- 10 kGy of electron beam radiation followed by melt annealing and sterilization by gas plasma. When compared to contemporary conventional molded GUR 1050 UHMWPE sterilized by 37 kGy of gamma radiation, the HXPE material has enhanced wear properties, has no detectable free radicals, and is resistant to oxidation and oxidative-related material property changes. The relative wear improvement of the HXPE is maintained in the presence of bone cement or alumina particles. The HXPE produced greater than 90% fewer wear particles in all size ranges and statistically significantly (P < .0001) smaller average-size particles than did the conventional UHMWPE.

An in vivo murine model of continuous intramedullary infusion of polyethylene particles

Wear debris affects both initial osseointegration and subsequent bone remodeling of total joint replacements (TJRs). To study the complex cascade associated with the continuous generation of particles, a robust animal model is essential. To date, an animal model that incorporates continuously delivered particles to an intramedullary orthopaedic implant has not been available. In this study, we successfully infused clinically relevant ultra high molecular weight polyethylene particles, previously isolated from joint simulator tests, to the intramedullary space of the mouse femur for 4 weeks using a subcutaneous osmotic pump. Reduction of bone volume following the 4-week infusion of UHMWPE was detected by microCT. UHMWPE particles also changed the level of Alkaline Phosphatase expression in the infused femurs. Continuous infusion of particles to the murine bone-implant interface simulated the clinical scenario of local polymer wear particle generation and delivery in humans and can be used to further study the biological processes associated with wear debris particles.

Cystic lesion of the groin due to metallosis: a rare long-term complication of metal-on-metal total hip arthroplasty

We present 2 patients with swelling of the groin after metal-on-metal total hip arthroplasty without radiological signs of component loosening. Magnetic resonance imaging in both patients showed a round intrapelvic lesion ventral to the femoral head. During surgery, we found cystic structures filled with fluid and necrotic masses. After resection of the cyst, the metal head and insert were replaced by a new ceramic head and a polyethylene liner. Although 2 different kinds of alloy were used (Sikomet, low carbon content; Metasul, high carbon content), histopathological analysis in both cases showed typical morphological signs of a hypersensitively determined inflammation. Despite the distinct soft tissue reaction, bony component integration was unaffected. In our opinion, open resection of the cystic lesion and changing of the metal-on-metal articulation is the treatment of choice.

Serum metal ion exposure after total knee arthroplasty

All metal implants release metal ions because of corrosion. This has been studied and debated, especially in metal-on-metal total hip arthroplasties. Total knee arthroplasty implants have large metal surface areas and therefore substantial potential for corrosion. We determined changes in serum levels of metal ions in 41 patients after cemented unconstrained total knee arthroplasty without patellar resurfacing, 18 with unilateral total knee arthroplasty (median, 66 months after surgery) and 23 patients with bilateral total knee arthroplasties (75 and 50 months after first and second surgeries, respectively). Serum concentrations of chromium, cobalt, and molybdenum were analyzed and related to the number of total knee arthroplasties and compared with those of 130 control patients without implants. The median chromium, cobalt, and molybdenum concentrations were 0.92, 3.28, and 2.55 microg/L, respectively, in the unilateral total knee arthroplasty sample and 0.98, 4.28, and 2.40 microg/L, respectively, in the bilateral total knee arthroplasty sample. We observed no difference between the serum levels in patients with unilateral and bilateral arthroplasties, but the serum levels of chromium and cobalt of both study groups were greater than those of the control group (less than 0.25 microg/L). The patients who had total knee arthroplasty had molybdenum profiles that were similar to those of the control group (median, 2.11 microg/L).

A review of ceramic bearing materials in total joint arthroplasty

Bearings made of ceramics have ultra-low wear properties that make them suitable for total hip arthroplasty (THA) and total knee arthroplasty (TKA). When compared to cobalt chrome (CoCr)-on-polyethylene (PE) articulations, ceramics offer drastic reductions in bearing wear rates. Lower wear rates result in fewer wear particles produced by the articulating surfaces. In theory, this should reduce the risk of periprosthetic osteolysis and premature implant loosening, thereby contributing to the longevity of total joints. In addition to ceramics, other alternative bearing couples, such as highly cross-linked PE (XLPE) and metal-on-metal also offer less wear than CoCr-on-PE articulations in total joint arthroplasty. Alumina and zirconia ceramics are familiar to orthopaedic surgeons since both materials have been used in total joints for several decades. While not new in Europe, alumina-on-alumina ceramic total hips have only recently become available for widespread use in the United States from various orthopaedic implant manufacturers. As the search for the ideal total joint bearing material continues, composite materials of existing ceramics, metal-on-ceramic articulations, and new ceramic technologies will offer more choices to the arthroplasty surgeon. The objective of this paper is to present an overview of material properties, clinical applications, evolution, and limitations of ceramic materials that are of interest to the arthroplasty surgeon.

Clinical and radiological outcome of total hip replacement five years after pamidronate therapy

Bisphosphonates reduce peri-prosthetic bone loss in the short term after total hip replacement but the mid- and longer term effects are not known. The aims of this randomised trial were to examine the effect of a single dose of 90 mg of pamidronate on the clinical and radiological outcome and peri-prosthetic bone mineral density in 50 patients (56 hips) over a five-year period, following total hip replacement.

At five years, 37 patients (42 hips) returned for assessment. The Harris hip scores were similar in the pamidronate and placebo groups throughout the study. Also at five years, four patients, two from each group had osteolytic lesions on plain radiography. These were located around the acetabular component in three patients and in the femoral calcar in one. The femoral and acetabular peri-prosthetic bone mineral density in the pamidronate group and the control group was similar at five years.

Pamidronate given as a single post-operative dose does not appear to influence the clinical outcome or prevent the development of osteolytic lesions at five years after total hip replacement.

Differences in ion release after ceramic-on-ceramic and metal-on-metal total hip replacement. Medium-term follow-up

Modern metal-on-metal bearings produce less wear debris and osteolysis, but have the potential adverse effect of release of ions. Improved ceramic-on-ceramic bearings have the lowest wear of all, but the corrosion process has not been analysed. Our aim was to measure the serum ion release (ng/ml) in 23 patients having stable hip prostheses with a ceramic-on-ceramic coupling (group A) and to compare it with the release in 42 patients with a metal-on-metal bearing (group B) in the medium term. Reference values were obtained from a population of 47 healthy subjects (group C). The concentrations of chromium, cobalt, aluminium and titanium were measured. There was a significant increase of cobalt, chromium and aluminium levels (p < 0.05) in group B compared with groups A and C. Group A did not differ significantly from the control group. Despite the apparent advantage of a metal-on-metal coupling, especially in younger patients with a long life expectancy, a major concern arises regarding the extent and duration of ion exposure. For this reason, the low corrosion level in a ceramic-on-ceramic coupling could be advantageous.

The clinical significance of metal ion release from cobalt-chromium metal-on-metal hip joint arthroplasty

Metal-on-metal (MOM) bearings offer extremely low wear and the avoidance of polyethylene but generate metallic wear particles. Although their total volume is dramatically smaller than polyethylene debris, these particles are in the nanometre size range and are many times more numerous. Metallic particles are ingested by macrophages or may be disseminated via lymphatics to the reticuloendothelial system. They corrode, and metal ions are present in the circulation and concentrated in erythrocytes. Excretion of metal ions via the kidneys seems to balance their generation in patients with MOM implants. However, highly sensitive detection methods can be used to show that levels of circulating cobalt and chromium ions are several times the normal level. These concentrations are well within the limits identified as dangerous to health in workers exposed to industrial chemicals, and also considerably lower than the levels found to cause cell toxicity in vitro. The local concentrations of particles and metal ions in the synovial tissue may occasionally exceed these limits and cause tissue necrosis. Clinical experience of lysis is rare in association with MOM bearings, as are hypersensitivity reactions and MOM bearings have had an excellent record over four decades and have a favourable benefit to risk ratio. Further reduction in risk will be achieved by improvement of materials, engineering, and accuracy of insertion.

Cancer incidence and causes of death among total hip replacement patients: A review based on Nordic cohorts with a special emphasis on metal-on-metal bearings

All patients with total hip arthroplasty (THA) are exposed to soluble or particulate forms of Co and Cr. Adverse effects of these wear products are not known. Data from Nordic registries is used to estimate adverse effects on a large scale, based mostly on metal-on-polyethylene bearings. Cancer incidence was in line with the general population when the patients were operated on for all indications and significantly decreased when the indication was primary osteoarthritis. Stomach cancer and colorectal cancers were significantly reduced and prostate cancer and skin melanoma significantly increased. There was no significant excess of cancer in target organs, i.e. liver, kidney, or haematopoietic cancers. THA patients had reduced mortality and extended life expectancy compared with standard Nordic populations.

All-site cancer incidence of the first-generation metal-on-metal McKee-Farrar patients operated on for primary osteoarthritis was in line with the general population after follow-up for up to 28 years. General mortality of these patients was also reduced and they also had an extended life expectancy.

Temporary increases in haematopoietic cancers at different follow-up periods were seen in some cohorts. This malignancy deserves a special record linkage monitoring while large numbers of young patients are provided with the second generation of metal-on-metal prostheses.

Metal-on-metal total hip replacement

Metal-on-metal bearings have wear rates that are 20 to 100 times lower than metal-on-conventional polyethylene. The amount of wear generally is the same order of magnitude for the head and the cup. There is an initial run-in period of higher wear followed by lower, steady-state wear. Wear rate is a function of the interplay of material(s), macrogeometry, microgeometry, and the resultant type and amount of lubrication. The wear resistance and clinical performance of a metal-on-metal bearing are more sensitive to macrogeometry and lubrication than a metal-on-polyethylene bearing. Metal wear particles are nanometers in linear dimension. They are much smaller and more numerous than the submicron polyethylene wear particles, but the volume of periprosthetic inflammatory tissue is less. Osteolysis seems to be relatively rare. Little is known about the systemic distribution of metal particles and ions. The significance of systemic distribution also is not known. The levels of serum and urine Co and Cr ions are elevated in patients with metal-on-metal bearings, but the long-term, steady-state levels are not much higher than those from corrosion of modular femoral components. Because of the elevated levels of Co and Cr ions, there is a greater risk of delayed type hypersensitivity. There also is concern about the potential for malignant degeneration secondary to prolonged exposure to these elements. The available data are insufficient to address this concern. Rigorous long-term studies are needed. It will take decades of close clinical observation to determine if the benefits of metal-on-metal bearings outweigh the associated risks.

Cup inclination and serum concentration of cobalt and chromium after metal-on-metal total hip arthroplasty

We investigated whether cup inclination influences serum levels of cobalt and chromium after metal-on-metal total hip arthroplasty. Out of a consecutive series, 3 groups of 20 patients each were established according to their cup inclination: greatest inclination (55 degrees -63 degrees, mean 58 degrees), intermediate inclination (44 degrees -46 degrees, mean 45 degrees), and smallest inclination (23 degrees -37 degrees, mean 33 degrees). We did not detect any statistically significant difference of serum cobalt (P = .23) or serum chromium (P = .13) levels between the 3 groups applying the Kruskal Wallis test. However, 3 patients with cup inclinations of 58 degrees , 63 degrees , and 61 degrees exhibited 9.8-53.6-fold elevated cobalt and 9.5-30.5-fold elevated chromium levels when compared with the median concentrations of this trial. We therefore recommend accurate cup placement also for metal-on-metal articulations.

Metal-on-metal total hip arthroplasty: the concerns

The metal-on-metal bearing couple is having a resurgence in clinical applications seen in total hip and hip resurfacing technologies. The most noteworthy advantage of a metal-on-metal implant is the improved wear characteristics seen in vitro on wear simulators and in vivo with retrieved implants. All bearings have disadvantages, and a metal-on-metal bearing is no exception. Concerns exist regarding the generation of metal ions seen in the blood and urine of patients with metal-on-metal implants. These elevated metal ions have theoretical, although not proven, risks related to carcinogenic and biologic concerns. Additionally, concerns exist regarding hypersensitivity, increased incidence of instability and increased costs. Specific patient selection issues arise with metal-on-metal implants. The current generation of implants has only early and mid-term results available, with no long-term series yet published. Therefore, although a metal-on-metal bearing may be considered a viable alternative to either polyethylene or ceramic implants, outstanding and unresolved issues continue to exist with this bearing, as they do with the alternatives.

Biologic and tribologic considerations of alternative bearing surfaces

Patients who are young or active or both who require total joint replacement pose a unique challenge; their high activity demands wear-resistant bearings that will perform for decades, without suffering from the adverse effects of accumulated wear products. We discuss the tribologic and biologic properties of newly introduced bearing materials for hip prostheses. The new PEs are intended to address the aseptic loosening problem by reducing the volume of submicron PE particles to a level well below that historically associated with osteolysis. However, choosing among the several variations of the cross-linked thermally-stabilized PEs is confounded by conflicting opinions regarding the optimum balance between long-term wear resistance and mechanical strength, and regarding potential effects of differences in morphologic features of the submicron-sized wear particles on their relative osteolytic potential. Metal-on-metal bearings have clinically proven wear resistance and the advantage of self-polishing, but the long-term biologic effects of metallic ions remain unknown. Ceramic-on-ceramic bearings have the advantage of high biocompatibility and usually very low wear, but fracture remains a rare but catastrophic complication. The choice of an appropriate bearing couple should be made after a thorough consideration of the relative risks and potential benefits of each of these materials.

Fractures of ceramic bearings: history and present status

During a period of 25 years (1977 to 2001), 13 fractures of an alumina component were recorded retrospectively. During the same period, approximately 5500 alumina components were implanted (3300 with all-alumina bearings and 1200 with alumina-on-polyethylene). These events occurred in seven women and six men, with a mean age of 59 years and a mean weight of 71 kg. There were eight fractures of the femoral head and five fractures of the socket component. Three fractures clearly were related to trauma (two fractures of the socket and one fracture of the head) and two were related to an abnormal design (one 22-mm head and one extra-long neck). Five fractures occurred without any rational explanation, but two fractures that occurred in the early phase could have been caused by a weaker alumina material. Finally three recent fractures of the liner were related to a change in the design of the material. This has been corrected and no additional fractures were observed. Although this dramatic event is of concern, it is infrequent and easy to solve by a limited revision procedure if done emergently. This rare complication should be balanced with the other complications of THR, including mechanical failures and osteolysis, often described with metal-on-polyethylene prostheses.

Ion release in stable hip arthroplasties using metal-on-metal articulating surfaces: a comparison between short- and medium-term results

The use of metallic heads articulating with metallic cups could solve the problem of polyethylene (PE) wear in total hip replacement (THR) with metal-on-PE bearings. A conspicuous release of metal ions from new models of metal-on-metal bearings has been found in the short-term, but it is yet unclear whether the medium-term corrosion rate is high or, on the contrary, it becomes negligible, because of the continuous surface finishing. Our purpose was to compare the serum ion values (nanograms per milliliter) in 15 patients with metal-on-metal stable prosthesis (Group A), in the short-term (subgroup A(1); mean follow-up: 24 mo) and medium-term (subgroup A(2); mean follow-up: 52 mo), in order to determine whether the ion release decreased with time of implant. Chromium (Cr), cobalt (Co), molybdenum (Mo) and aluminum (Al) were analyzed. Twenty-two presurgical patients were used for comparison (Group B). The reference range was obtained from a population of 27 healthy subjects (Group C). Co and Cr levels in the medium-term (subgroup A(2)) were not decreased in comparison with the short-term values (subgroup A(1)) and were significantly higher (p < 0.001) than presurgical and reference values. Otherwise, Mo and Al concentrations were not significantly increased in comparison with reference values. In conclusion, despite the apparent advantage of metal-on-metal coupling, especially in younger patient populations, there is a major concern about the extent and duration of the relevant "internal" exposure to Cr and Co ions. This exposure should be carefully monitored, in order to clarify the biologic effects of ion dissemination and, consequently, to identify risks concerning long-term toxicity of metals.

Ion release in patients with metal-on-metal hip bearings in total joint replacement: a comparison with metal-on-polyethylene bearings

Polyethylene (PE) wear has been shown to be a problem in long-term joint replacement using metal-on-PE bearing. The use of metallic heads articulating with metallic cups could solve this problem: success will be enhanced if wear and corrosion of the articulating surfaces are maintained at a low level. New models with metal-on-metal bearing have been proposed, to be used mainly for young subjects: such coupling seems to have a reduced release, but it is unclear yet if the medium-term corrosion rate is really negligible or, on the contrary, it is significantly higher than in the metal-on-PE bearing. Aim of our study was the comparison of ion release in the serum of two groups of patients who had the same type of stable cementless prosthesis, but different bearing: twenty-six patients with metal-on-metal (Group A) and fifteen patients with metal-on-PE bearing (Group B) were examined. The follow-up was 14-38 months for group A and 18-34 months for group B. The serum concentration of chromium (Cr), cobalt (Co) and molybdenum (Mo) was measured. Twenty-two patients before surgery were used for comparison (Group C). The reference values were obtained from a population of twenty-two healthy subjects (Group D). Our findings indicate that metal-on-metal bearings produce a significantly higher systemic release of cobalt and chromium (ng/ml) when compared with levels found in metal-on-PE, pre-surgery and reference groups. Such a high release should induce to improve the bearing materials or, at least, to study the biologic fate of metal ions and consequently their long-term effects. In such a way a risk-to-benefit ratio for the patient could be established.

Retrieval study of uncemented metal-metal hip prostheses revised for early loosening

A tribologic assessment was performed on 22 metal-metal hip prostheses from a single manufacturer, following removal for early aseptic loosening after a mean service life of 32 months (range, 12-59 months). The mean linear wear rate was 7.6 microm/year (range, 2.9-12.8 microm/year). This was below the rates previously observed in other modern metal-metal combinations. A novel contour analysis technique using a coordinate measuring machine showed the mean volumetric wear rate to be 2.02 mm(3)/year (range, 0.55-3.74 mm(3)/year), which corresponds to a mean gravimetric wear rate of 16.9 mg/year (range, 4.6-31.4 mg/year). The mean clearance of 39.8 microm (range, 30-50 microm) was within the optimal range for hard-hard bearing combinations. Evidence of abrasive, adhesive, and third-body wear was found on all bearing surfaces. The tribologic assessment did not indicate manufacturing defects as a cause of early loosening. Equally, third-body wear was too low to be considered a causative factor for early loosening.