Wear analysis of retrieved alumina heads and sockets of hip prostheses

Ceramic-on-Ceramic Total Hip Arthroplasty Using a Double Tapered, Proximally Coated Stem: 15 to 24-year Clinical and Radiologic Follow-Up

BACKGROUND

Total hip arthroplasty implant choice profoundly affects survivorship, complications, and failure modes. This study evaluates the long-term (average 18 year) outcomes of ceramic-on-ceramic hip arthroplasty using uncemented shells and stems. Despite an impressive 20-year cumulative percent revision of 5.9%, the hydroxyapatite proximally coated femoral components evaluated in this study have seen declining use since 2003.

METHODS

A review of 349 consecutive total hip arthroplasties from 1999 to 2007 was matched to 272 cases with registry data. A survivorship analysis included 274 hips (Group A) after excluding patients lost to follow-up and navigated cases. Group B comprised 135 patients who had complete datasets spanning a minimum of 15 years.

RESULTS

Kaplan-Meier analysis identified a 95.6% survivorship plateau at 16 to 24 years, with no significant impact from age, sex, component size, or original pathology. In Group B, EuroQol-5 Dimensions-5 Levels (EQ5D5L) scores indicated favorable outcomes in mobility, self-care, activities, pain/discomfort, and anxiety/depression, with an EQ5D visual analog score mean of 79.24. Functional scores, including the Harris Hip Score, Oxford Hip Score, and Forgotten Joint Score, showed positive outcomes. Radiologic assessments revealed no osteolysis or loose components, with a mean Engh score of 21.69. Dorr classification identified bone quality variations. Better Engh scores corresponded to higher levels of patient satisfaction. Age at surgery was correlated with better functional scores, while sex influenced various outcomes.

CONCLUSIONS

This comprehensive study, spanning an average of 18.23 years, combined multiple patient-reported outcome measures with extensive clinical and radiologic follow-up. It reported a notably high survivorship rate for this implant combination but highlighted the declining use of the hydroxyapatite proximally coated femoral stem used in this study, potentially facing withdrawal risks in Australia.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Inflammatory, Oxidative Stress and Small Cellular Particle Response in HUVEC Induced by Debris from Endoprosthesis Processing

We studied inflammatory and oxidative stress-related parameters and cytotoxic response of human umbilical vein endothelial cells (HUVEC) to a 24 h treatment with milled particles simulating debris involved in sandblasting of orthopedic implants (OI). We used different abrasives (corundum-(Al₂O₃), used corundum retrieved from removed OI (u. Al₂O₃), and zirconia/silica composite (ZrO₂/SiO₂)). Morphological changes were observed by scanning electron microscopy (SEM). Concentration of Interleukins IL-6 and IL-1β and Tumor Necrosis Factor α (TNF)-α was assessed by enzyme-linked immunosorbent assay (ELISA). Activity of Cholinesterase (ChE) and Glutathione S-transferase (GST) was measured by spectrophotometry. Reactive oxygen species (ROS), lipid droplets (LD) and apoptosis were measured by flow cytometry (FCM). Detachment of the cells from glass and budding of the cell membrane did not differ in the treated and untreated control cells. Increased concentration of IL-1β and of IL-6 was found after treatment with all tested particle types, indicating inflammatory response of the treated cells. Increased ChE activity was found after treatment with u. Al₂O₃ and ZrO₂/SiO₂. Increased GST activity was found after treatment with ZrO₂/SiO₂. Increased LD quantity but not ROS quantity was found after treatment with u. Al₂O₃. No cytotoxicity was detected after treatment with u. Al₂O₃. The tested materials in concentrations added to in vitro cell lines were found non-toxic but bioactive and therefore prone to induce a response of the human body to OI.

Experimental Investigation of Material Transfer on Bearings for Total Hip Arthroplasty—A Retrieval Study on Ceramic and Metallic Femoral Heads

Metallic deposition is a commonly observed phenomenon on the surface of revised femoral heads in total hip arthroplasty and can lead to increased wear due to third bodies. In order to find out the origin and composition of the transfer material, 98 retrieved femoral heads of different materials were examined with regard to the cause of revision, localization, pattern and composition of the transfer material by energy dispersive X-ray spectroscopy. We found that in 53.1%, the deposition was mostly in the region of the equator and the adjacent pole of the femoral heads. The most common cause for revision of heads with metallic deposition was polyethylene wear (43.9%). Random stripes (44.9%), random patches (41.8%) and solid patches (35.7%) were most prevalent on retrieved femoral heads. Random patches were a typical pattern in ceramic-on-ceramic bearing couples. The solid patch frequently occurred in association with dislocation of the femoral head (55%). The elemental analysis of the depositions showed a variety of different materials. In most cases, titanium was an element of the transferred material (76.5%). In addition to metallic components, several non-metallic components were also detected, such as carbon (49%) or sulfur (4.1%). Many of the determined elements could be assigned with regard to their origin with the help of the associated revision cause. Since the depositions lead to an introduction of third-body particles and thus to increased wear, the depositions on the bearing surfaces should be avoided in any case.

Review of total hip arthroplasty in patients younger than 30 years: mid- to long-term results

BACKGROUND

Data on the outcome of THA in patients under the age of 30 years is sparse. There is a perceived reluctance to offer surgery to young patients on the basis of potential early failure of the implant. The aim of this study was to review clinical and radiological outcomes of THA in patients under the age of 30 years in a high-volume specialist arthroplasty unit.

METHODS

A retrospective review of patients between 1989 and 2009 was undertaken. 95 patients (118 THAs) were identified but 17 patients were excluded for lack of clinical records or for follow-up under 5 years. Clinical records were reviewed for demographics, underlying pathology, details of operation and failures. Radiographs were reviewed for evidence of loosening and wear of the components. Functional assessment was carried out using the modified Hip disability and Osteoarthritis Outcome Score, Oxford Hip Score and EQ-5D-5L.

RESULTS

Mean age was 25 (16-30) years and 65% patients were females. The most common underlying pathologies were development dysplasia of the hip (29%) and juvenile rheumatoid arthritis (25%). Mean follow-up was 12.6 (5-24) years, during which 19 patients (25%) were revised. The majority of the revisions were for aseptic loosening of the acetabular component.

CONCLUSIONS

Surgeons are cautious when considering THA in very young patients despite the significant documented improvement in function and quality of life after THA. This study reports on the mid- to long-term results of THA which will be valuable when advising young patients on the prospects of revision surgery at the time of primary THA.

Wear debris released by hip prosthesis analysed by microcomputed tomography

Total hip arthroplasty uses commercial devices that combine different types of biomaterials. Among them, metals, ceramics and metal oxides can be used either in the prosthesis itself or in the cement used to anchor them in the bone. Over time, all of these materials can wear out and release particles that accumulate in the periprosthetic tissues or can migrate away. We used histology blocks from 15 patients (5 titanium metallosis, 5 alumina prostheses, 5 with altered methacrylic cement) to perform a microCT study and compare it with conventional histology data. An EDS-SEM analysis was done to characterise the atomic nature of the materials involved. A morphometric analysis was also performed in 3D to count the particles and assess their density and size. The metallic particles appeared to be the largest and the ceramic particles the finest. However, microCT could not reveal the wear particles of radiolucent biomaterials such as polyethylene and the very fine zirconia particles from cement fragmentation. MicroCT analysis can reveal the extent of the accumulation of these debris in the periprosthetic tissues. LAYOUT DESCRIPTION: Hip prostheses progressively degrade in the body by releasing wear debris. They accumulate in the periprosthetic tissues. Microcomputed tomography was used to image three types of radio-opaque wear debris: metal, ceramic and zirconia used in the bone cements.

Influence of Metallic Deposition on Ceramic Femoral Heads on the Wear Behavior of Artificial Hip Joints: A Simulator Study

Several retrieval studies have reported on metallic depositions on ceramic femoral heads, but the effect on the wear behavior of artificial hip joints has not been investigated in wear simulator studies. In the present study, retrieved ceramic heads with metallic depositions as third particles were tested against cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) liners in a hip wear simulator. The amount of liner wear and expansion of metallic depositions on the heads were determined before and after wear testing with digital microscopy. The surface roughness of the heads was investigated in areas with and without metallic depositions by laser scanning microscopy. After five million load cycles, a non-significant reduction in the metallic formation on the retrieved heads was found. The metallic areas showed a higher surface roughness compared to unconcerned areas. The liners showed a higher wear rate of 1.57 ± 1.36 mg/million cycles for 28 mm heads and 2.42 ± 0.82 mg/million cycles for 36 mm heads with metallic depositions, in comparison with new ceramic heads with a 28 mm size ((-0.06 ± 0.89) mg/million cycles) and 36 mm size ((2.04 ± 0.46) mg/million cycles). Metallic transfer on ceramic heads can lead to an increased surface roughness and higher wear rates at the UHMWPE liners. Therefore, metallic contact of the ceramic femoral head should be avoided.

[Research progress of total hip arthroplasty for patients with sequelae of suppurative hip arthritis]

Objective

To summarize the research progress of total hip arthroplasty (THA) in treatment of sequelae of suppurative hip arthritis.

Methods

The relevant literature was systematically searched and the operation timing, treatments of acetabular and femoral sides, and prosthesis selection in THA for sequelae of suppurative hip arthritis were summarized.

Results

THA is an effective way to treat the sequelae of suppurative hip arthritis. In order to avoid the recurrence of infection, THA is recommended to be performed after 10 years of resting period of hip septic infection. These patients may have acetabulum dysplasia and poor coverage of acetabulum. When performing THA, high position acetabulum, osteotomy of the medial acetabular wall, structural bone graft, Cage, tantalum augment, or three-dimensional printing prosthesis can be chosen. The femoral side may has small medullary cavity, increased femoral neck anteversion, increased femoral neck-stem angle, extend trochanter, and poor bone mass. When performing THA, the femoral osteotomy and appropriate prosthesis can be selected for treatment. The patients with sequelae of suppurative hip arthritis are mostly young, cementless THA is preferred for a better long-term survivorship.

Conclusion

THA is an effective method for the sequelae of suppurative hip arthritis, but the operation is difficult and has relative high complication rate. Surgeons should have full understanding.

Materials for Hip Prostheses: A Review of Wear and Loading Considerations

Replacement surgery of hip joint consists of the substitution of the joint with an implant able to recreate the articulation functionality. This article aims to review the current state of the art of the biomaterials used for hip implants. Hip implants can be realized with different combination of materials, such as metals, ceramics and polymers. In this review, we analyze, from international literature, the specific characteristics required for biomaterials used in hip joint arthroplasty, i.e., being biocompatible, resisting heavy stress, opposing low frictional forces to sliding and having a low wear rate. A commentary on the evolution and actual existing hip prostheses is proposed. We analyzed the scientific literature, collecting information on the material behavior and the human-body response to it. Particular attention has been given to the tribological behavior of the biomaterials, as friction and wear have been key aspects to improve as hip implants evolve. After more than 50 years of evolution, in term of designs and materials, the actual wear rate of the most common implants is low, allowing us to sensibly reduce the risk related to the widespread debris distribution in the human body.

Ceramic prosthesis surfaces induce an inflammatory cell response and fibrotic tissue changes

Aims

Early evidence has emerged suggesting that ceramic-on-ceramic articulations induce a different tissue reaction to ceramic-on-polyethylene and metal-on-metal bearings. Therefore, the aim of this study was to investigate the tissue reaction and cellular response to ceramic total hip arthroplasty (THA) materials in vitro, as well as the tissue reaction in capsular tissue after revision surgery of ceramic-on-ceramic THAs.

Patients and Methods

We investigated tissue collected at revision surgery from nine ceramic-on-ceramic articulations. we compared our findings with tissue obtained from five metal-on-metal THA revisions, four ceramic-on-polyethylene THAs, and four primary osteoarthritis synovial membranes. The latter were analyzed to assess the amount of tissue fibrosis that might have been present at the time of implantation to enable evaluation, in relation to implantation time, of any subsequent response in the tissues.

Results

There was a significant increase in tissue fibrosis with implantation time for all implant types tested. Interestingly, the tissue fibrosis in ceramic-on-ceramic THAs was significantly increased compared with metal-on-metal and ceramic-on-polyethylene. Additionally, we found ceramic wear particles in the periprosthetic tissue of ceramic implants. Fibroblasts responded with expression of cytokines when cultured on alumina-toughened zirconia (ATZ) and zirconia-toughened alumina (ZTA) ceramic surfaces. This response was more pronounced on ATZ ceramics compared with ZTA ceramics. The same inflammatory response was observed with peripheral blood mononuclear cells (PBMCs) cultured on ZTA and ATZ.

Conclusion

Our findings therefore, corroborate the previous findings that ceramic-on-ceramic periprosthetic revision tissue is fibrous and offer an explanation for this observation. We detected a long-term inflammatory response of PBMCs and an inflammatory response of fibroblasts to ATZ and ZTA ceramic. These findings partially explain the fibrotic tissue change in periprosthetic tissue of ceramic-on-ceramic bearings. Cite this article: Bone Joint J 2018;100-B:882–90.

Challenges in Total Hip Arthroplasty in the Setting of Developmental Dysplasia of the Hip

BACKGROUND

Developmental dysplasia of the hip (DDH) is a recognized cause of secondary arthritis, which may eventually lead to total hip arthroplasty (THA). An understanding of the common acetabular and femoral morphologic abnormalities will aid the surgeon in preparing for the complexity of the surgical case.

METHODS

We present the challenges associated with acetabular and femoral morphologies that may be present in the dysplastic hip and discuss surgical options to consider when performing THA. In addition, common complications associated with this population are reviewed.

RESULTS

The complexity of THA in the DDH patient is due to a broad range of pathomorphologic changes of the acetabulum and femur, as well as the diverse and often younger age of these patients. As such, THA in the DDH patient may offer a typical primary hip arthroplasty or be a highly complex reconstruction. It is important to be familiar with all the subtleties associated with DDH in the THA population. The surgeon must be prepared for bone deficiency when reconstructing the acetabulum and should place the component low and medial (at the anatomic hip center), and avoid oversizing the acetabular component. Femoral dysplasia is also complex and variable, and the surgeon must be prepared for different stem choices that allow for decoupling of the metaphyseal stem fit from the implanted stem version. In Crowe III and IV dysplasia, femoral derotation/shortening osteotomy may be required. Many complications associated with THA in the DDH patient may be mitigated with careful planning and surgical technique.

CONCLUSION

Performed correctly, THA can yield excellent results in this complex patient population.

Return to Sporting Activity After Total Hip Arthroplasty-A Survey of Members of the British Hip Society

BACKGROUND

Total hip arthroplasty is increasingly performed in younger, more active patients. Thirty-five percent of patients are involved in sports preoperatively, and a desire to return to sporting activity is now a major expectation. Sporting activity potentially risks premature failure of the implant, and there is no consensus or guidelines among British or European surgeons performing total hip arthroplasty in sporting patients.

METHODS

The current practice of British Hip Society members was explored through a Web-based survey. Of the 260 members surveyed, 109 responded.

RESULTS

The majority of respondents (33%) would perform uncemented, 29.1% would perform hybrid, 15.5% would perform fully cemented, and 11.7% would perform a resurfacing hip arthroplasty for sporting patients. The preferred approach is the standard posterior (68.9%) and preferred bearing couples are ceramic-on-ceramic (39.8%) and ceramic-on-polyethylene (36.9%). Half of respondents would opt for a femoral head smaller than 36 mm, whereas 22.3% would use a head 36 mm or larger. A third would allow patients to return to sports between 6 and 12 weeks after surgery, whereas 43.7% advise patients to wait until 3 months postoperatively. All respondents allow patients to return to low-impact activities, but significant caution is exercised with regard to taking part in high-impact activities.

CONCLUSION

We report the practice of a specialist group of hip surgeons, the majority of which consider themselves young adult hip specialists. We believe that these data may be of use to help inform the practice of our colleagues when performing arthroplasty in sporting patients and may serve to inform future consensus guidelines.

Does Metal Transfer Differ on Retrieved Ceramic and CoCr Femoral Heads?

Metal transfer has been observed on retrieved THA femoral heads for both CoCr and ceramic bearing materials. In vitro wear testing has shown increased wear to polyethylene acetabular liners with the presence of metal transfer. This study sought to investigate the extent of metal transfer on the bearing surface of CoCr and ceramic femoral heads and identify prevalent morphologies. Three bearing couple cohorts: M-PE (n = 50), C-PE (n = 35), and C-C (n = 15), were derived from two previously matched collections (n = 50/group) of CoCr and ceramic femoral heads. From the three cohorts, 75% of the femoral heads showed visual evidence of metal transfer. These femoral heads were analyzed using direct measurement, digital photogrammetry, and white light interferometry. Surface area coverage and curved median surface area were similar among the three cohorts. The most prevalent metal transfer patterns observed were random stripes (n = 21/75), longitudinal stripes (n = 17/75), and random patches (n = 13/75). Metal transfer arc length was shorter in the M-PE cohort. Understanding the morphology of metal transfer may be useful for more realistic recreation of metal transfer in in vitro pin-on-disk and joint simulators studies.

Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty

This study reports mid-term results of Delta ceramic on ceramic (COC) in total hip arthroplasty (THA). Subjects received Delta COC THA in a prospective multi-center study with either 28 mm (n=177) or 36 mm (n=168) articulations. Annual clinical and radiographic evaluations were performed, and patients were asked about hip noises. At mean 5.3-year follow-up there were 3 (0.9%) post-operative liner fractures. Nine revisions were performed (2 liner fracture, 4 stem loosening, 3 deep infection). Kaplan-Meier survivorship at 6 years was 96.9% (94.0-98.4). Twenty-six (7.5%) subjects reported squeaking, of whom none were revised. One (0.3%) subject could reproduce a sound in clinic. More patients reported squeaking with a 36 mm bearing (28 mm: 7/177, 36 mm: 19/168, P=0.013).

Systematic review of total hip arthroplasty in patients under 30 years old

We performed a systematic review to assess whether joint replacement in this very 
young patient group provides significant functional improvement and whether these procedures are associated with good implant survivorship. The studies included presented the results of 
450 THA procedures. All patients showed an improvement in functional score and symptom relief. Uncemented stems showed good integration with no signs of loosening. Cemented implants showed high rates of loosening. This study shows that THA in the very young patient can provide good functional improvement and relief of symptoms and that the more modern uncemented implant designs used with hard-on-hard bearings can be associated with improved implant survival. Long-term studies are necessary to confirm the superiority and improved survivorship of these newer 
implants.

Risk of impingement and third-body abrasion with 28-mm metal-on-metal bearings

BACKGROUND

Concerns have been raised about the sequelae of metal-on-metal (MoM) bearings in total hip arthroplasty (THA). However, retrieval studies, which offer the best insight into the clinically relevant mechanisms of MoM wear, have followed predictable trends to date such as indicting cobalt-chromium (CoCr) metallurgy, cup design, high conformity between the head and cup, "steep cups," "microseparation," and "edge wear."

QUESTIONS/PURPOSES

We wished to evaluate a set of retrieved 28-mm MoM THA for signs of (1) cup-to-stem impingement; (2) normal wear pattern and concomitant stripe damage on femoral heads that would signify adverse wear mechanics; and (3) well-defined evidence of third-body scratches on bearings that would indicate large abrasive particles had circulated the joint space.

METHODS

Ten 28-mm MOM retrievals were selected on the basis that femoral stems were included. Revision surgeries at 3 to 8 years were for pain, osteolysis, and cup loosening. CoCr stems and the MoM bearings were produced by one vendor and Ti6Al4V stems by a second vendor. All but two cases had been fixed with bone cement. We looked for patterns of normal wear and impingement signs on femoral necks and cup rims. We looked for adverse wear defined as stripe damage that was visually apparent on each bearing. Wear patterns were examined microscopically to determine the nature of abrasions and signs of metal transfer. Graphical models recreated femoral neck and cup designs to precisely correlate impingement sites on femoral necks to cup positions and head stripe patterns.

RESULTS

The evidence revealed that all CoCr cup liners had impinged on either anterior or posterior facets of femoral necks. Liner impingement at the most proximal neck notch occurred with the head well located and impingement at the distal notch occurred with the head rotated 5 mm out of the cup. The hip gained 20° motion by such a subluxation maneuver with this THA design. All heads had stripe wear, the basal and polar stripes coinciding with cup impingement sites. Analysis of stripe damage revealed 40 to 100-μm wide scratches created by large particles ploughing across bearing surfaces. The association of stripe wear with evidence of neck notching implicated impingement as the root cause, the outcome being the aggressive third-body wear.

CONCLUSIONS

We found consistent evidence of impingement, abnormal stripe damage, and evidence of third-body abrasive wear in a small sample of one type of 28-mm MoM design. Impingement models demonstrated that 28-mm heads could lever 20° out of the liners. Although other studies continue to show good success with 28-mm MoM bearings, their use has been discontinued at La Pitie Hospital.

Titanium and zirconia particle-induced pro-inflammatory gene expression in cultured macrophages and osteolysis, inflammatory hyperalgesia and edema in vivo

AIMS

The biological reaction to wear debris is critical to the osteolysis underlying aseptic loosening of joint prosthetic implants. In an attempt to reduce aseptic loosening, ceramics have been introduced. This study was designed to evaluate, compare and correlate the expression of Toll-like receptors (TLRs), their intracellular adaptors and proinflammatory cytokines in cultured macrophages challenged with titanium or zirconia particles, as well as particle-induced osteolysis in calvaria and hyperalgesia and edema in hind paw.

MAIN METHODS

TLRs and their adaptors were evaluated at the mRNA level by RT-PCR, and cytokine expression was evaluated at the mRNA and protein levels. Osteolysis and hyperalgesia and edema were evaluated in vivo, in calvaria and hind paw, respectively.

KEY FINDINGS

Cultured macrophages challenged with zirconia or titanium particles expressed increased mRNA for TLRs 2, 3, 4 and 9, and their adaptors MyD88, TRIF and NF-κB and cytokines TNF-α, IL-1β and IL-6, which were also increased at protein level. Quantitative differences are evident and, in general, zirconia particle-induced pro-inflammatory gene expression was lower than that induced by titanium particles. In in vivo experiments, exposition to titanium or zirconia particles induced osteolysis in calvaria and hyperalgesia and edema in hind paw; however those induced by zirconia particles were significantly lower. There is a strong and positive correlation between the expressions of mRNA for TLR4, NF-κB, TNF-α, IL-1β and IL-6.

SIGNIFICANCE

Collectively, our data suggest that zirconia ceramic particles are less bioactive than titanium particles.

Alternative bearings in total hip arthroplasty in the young patient

Total hip arthroplasty is an effective treatment option for advanced hip arthritis in elderly patients. Studies in young patients have traditionally shown less durable results. With current implants, surgical technique, and cementless fixation methods, the durability of total hip arthroplasty may now be related to the wear performance of the bearing surfaces. To improve implant longevity, there are several bearing surface choices currently available for this demanding group of patients. Alternatives must be evaluated in terms of the risks and benefits associated with each articulation, and all new technologies must be carefully monitored over the long term.

Ideal femoral head size in total hip arthroplasty balances stability and volumetric wear

BACKGROUND

Over the last several years, a trend towards increasing femoral head size in total hip arthroplasty to improve stability and impingement free range of motion has been observed.

PURPOSE

The specific questions we sought to answer in our review were: (1) What are the potential advantages and disadvantages of metal-on-metal, ceramic-on-ceramic, and metal-on-polyethylene bearings? (2) What is effect that femoral head size has on joint kinematics? (3) What is the effect that large femoral heads have on bearing surface wear?

METHODS

A PubMed search and a review of 2012 Orthopaedic Research Society abstracts was performed and articles were chosen that directly answered components of the specific aims and that reported outcomes with contemporary implant designs or materials.

RESULTS

A review of the literature suggests that increasing femoral head size decreases the risk of postoperative dislocation and improves impingement free range of motion; however, volumetric wear increases with large femoral heads on polyethylene and increases corrosion of the stem in large metal-on-metal modular total hip arthroplasty (THA); however, the risk of potentially developing osteolysis or adverse reactions to metal debris respectively is still unknown. Further, the effect of large femoral heads with ceramic-on-ceramic THA is unclear, due to limited availability and published data.

CONCLUSIONS

Surgeons must balance the benefits of larger head size with the increased risk of volumetric wear when determining the appropriate head size for a given patient.

Factors affecting modular acetabular ceramic liner insertion: a biomechanical analysis

BACKGROUND

Ceramic liner fracture is a concern in THA. However, it is unclear what factors influence the risk of facture. To study these factors under controlled conditions, we created a laboratory model to avoid fractures in vitro.

QUESTIONS/PURPOSES

We determined (1) whether misaligned liner insertion, acetabular shell deformation, entrapment of soft tissue within the locking taper area, and damage to the taper during engagement of the ceramic liner on the locking taper influenced fracture at light and medium impaction forces; and (2) whether the number and force of impactions affect the locking taper force between the ceramic liner and acetabular shell and fracture of the ceramic liner.

METHODS

Impaction and pushout tests were performed with each of five ceramic inserts in titanium shells per test to simulate clinical intraoperative situations of misaligned inserts (Test 1), deformed shells (Test 2), soft tissue within the locking taper area (Test 3), simulated cup taper damage (Test 4), and a combination of misaligned insert, deformed shells, and simulated taper damage to create an overall worst-case condition (Test 5).

RESULTS

Higher pushout forces occurred with increased impact force and an increased number of strikes. Insert fractures only occurred where inserts were misaligned in the shell. No fractures occurred with deformed shells, soft tissue in the taper, or with simulated taper damage in the absence of misaligned inserts.

CONCLUSION

The data suggest a misaligned ceramic insert in an acetabular increases the potential for insert fracture. Shell deformation, soft tissue in the taper, or simulated taper damage seemed well tolerated even with very forceful impaction. Forceful and repetitive impaction is favorable for engagement of the taper and improving pullout strength.

Ceramic-on-ceramic total hip arthroplasty in patients younger than 20 years

Total hip arthroplasty (THA) in the adolescent patient has historically shown relatively poor survivorship. This study reports the results of THA in young patients using contemporary ceramic bearings. Twenty-four THAs were performed using ceramic bearing surfaces in patients 20 years old or younger (mean, 16.4; range, 12-20). Average follow-up was 52 months (range, 25-123 months). The survival rate was 96%, with 1 revision for a loose acetabular component. Other complications included a peroneal nerve palsy that resolved and 2 dislocations in 1 patient. Postoperatively, the Modified Harris Hip Score mean was 93.4 (range, 66-100). This study shows promising results at short-term to midterm follow-up in very young patients who undergo THA using ceramic-on-ceramic components.

Straight tapered titanium stem with alumina bearing in cementless primary total hip arthroplasty: a minimum 5-year follow-up

The aim of this study was to assess the midterm results of primary cementless total hip arthroplasty using a tapered stem and alumina bearing couple in active patients. After a minimum of 5 years of follow-up, 78 arthroplasties in 72 patients were reviewed retrospectively. The mean Harris hip score was 94 points, and 2 hips had thigh pain. All components radiographically demonstrated stable fixation by bone ingrowth and mild stress shielding of the proximal femur were noted in 14% of hips. There was no significant osteolysis or aseptic loosening. There was a ceramic head fracture in 1 hip and audible sounds in 2 hips. The results of total hip arthroplasty with a straight, tapered, proximally porous-coated stem and alumina-on-alumina bearing were encouraging for active patients.

State of the art in hard-on-hard bearings: how did we get here and what have we achieved?

Total hip arthroplasty has shown excellent results in decreasing pain and improving function in patients with degenerative disease of the hip. Improvements in prosthetic materials, designs and implant fixation have now resulted in wear of the bearing surface being the limitation of this technology, and a number of hard-on-hard couples have been introduced to address this concern. The purpose of this article is to review the origins, development, survival rates and potential advantages and disadvantages of the following hard-on-hard bearings for total hip arthroplasty: metal-on-metal standard total hip arthroplasty; metal-on-metal hip resurfacing arthroplasty, ceramic-on-ceramic total hip arthroplasty; and ceramic-on-metal bearings. Improvements in the manufacturing of metal-on-metal bearings over the past 50 years have resulted in implants that provide low wear rates and allow for the use of large femoral heads. However, concerns remain regarding elevated serum metal ion levels, potential teratogenic effects and potentially devastating adverse local tissue reactions, whose incidence and pathogenesis remains unclear. Modern total hip resurfacing has shown excellent outcomes over 10 years in the hands of experienced surgeons. Current ceramic-on-ceramic bearings have demonstrated excellent survival with exceptionally low wear rates and virtually no local adverse effects. Concerns remain for insertional chipping, in vivo fracture and the variable incidence of squeaking. Contemporary ceramic-on-metal interfaces are in the early stages of clinical use, with little data reported to date. Hard-on-hard bearings for total hip arthroplasty have improved dramatically over the past 50 years. As bearing designs continue to improve with new and modified materials and improved manufacturing techniques, it is likely that the use of hard-on-hard bearings will continue to increase, especially in young and active patients.

Mediators of the inflammatory response to joint replacement devices

Joint replacement surgery is one of the success stories of modern medicine, restoring mobility, diminishing pain and improving the overall quality of life for millions of people. Unfortunately, wear of these prostheses over time generates debris, which activates an innate immune response that can ultimately lead to periprosthetic resorption of bone (osteolysis) and failure of the implant. Over the past decade, the biological interactions between the particulate debris from various implant materials and the immune system have begun to be better understood. The wear debris induces a multifaceted immune response encompassing the generation of reactive oxygen species and damage-associated molecular patterns, Toll-like receptor signaling and NALP3 inflammasome activation. Acting alone or in concert, these events generate chronic inflammation, periprosthetic bone loss and decreased osteointegration that ultimately leads to implant failure.

Hip replacement in the athlete: is there a role?

Sport and total hip arthroplasty (THA) have been regarded by many as being mutually exclusive. The primary indication for hip arthroplasty has always been pain. With advances in the technology surrounding hip replacement surgery and increasing patient expectations of what THA can offer, there is a growing demand for hip replacement with the aim of returning to sporting activity. The aim of this review article is to report the advances in hip replacement surgery that aim to make the procedure more suitable for the sporting individual and to summarise the literature on the subject of returning to sports after THA.

A squeaky reputation: the problem may be design-dependent

BACKGROUND

Squeaking is reportedly a complication in patients having ceramic-on-ceramic total hip implants. The etiology remains unknown and multifactorial with recent studies suggesting a relationship between the audible squeak and implant design. When we evaluated our ceramic-on-ceramic cohort, we noticed squeaking primarily in patients receiving an acetabular system designed with an elevated titanium rim.

OBJECTIVES/PURPOSES

We therefore (1) determined the incidence of squeaking among four different ceramic-on-ceramic bearing surfaces used for THA at our institution; (2) evaluated the association between different acetabular designs and the incidence of squeaking; and (3) assessed other potential variables associated with squeaking.

METHODS

We retrospectively reviewed 1507 patients having a ceramic-on-ceramic THA between 2002 and 2009; we separately analyzed those receiving an acetabular system with and without an elevated titanium rim. Data were collected through phone-administered questionnaires and retrospective reviews of patient charts for intraoperative findings, followup reports, demographic information, and radiographic findings.

RESULTS

Squeaking occurred in 92 of the 1507 patients (6%). All 92 patients with squeaking received an elevated rim design (1291 patients) or an incidence of 7% with that design. We found no association between squeaking and any other examined factors.

CONCLUSION

Our findings complement the theory from in vitro studies suggesting that neck impingement on the elevated titanium rim is the probable cause of the increased frequency of squeaking with this design.

THA with Delta ceramic on ceramic: results of a multicenter investigational device exemption trial

Although the published studies on the outcomes of total hip arthroplasty (THA) performed with currently available ceramic components show high survivorship and low bearing wear at midterm followup, concern over ceramic fracture and squeaking persist. For these reasons, the use of ceramic is limited. Recently, a new alumina matrix composite material (Delta ceramic) with improved material properties was developed to address these concerns. We report the early outcomes and complications of a prospective, randomized, multicenter trial of 263 patients (264 hips) at eight centers, comparing a Delta ceramic-on-ceramic (COC) articulation with a Delta ceramic head-crosslinked polyethylene bearing combination (COP). There were 177 COC hips and 87 COP hips. Complications were reported for all patients, whereas clinical and radiographic results were provided for the 233 patients with minimum 2-year followup (average, 31.2 months; range, 21-49 months). The Harris hip scores and clinical, radiographic, and survivorship outcomes were similar in both groups. There were four (2%) revisions in the COC group and two (2%) in the COP group. We encountered three intraoperative ceramic liner-related events. In addition, one patient receiving the COC underwent revision for chipping of the ceramic liner, and a second had ceramic fragmentation on followup radiographs but has not undergone revision. These liner related complications remain a concern. No patient reported squeaking in either group; this leaves us hopeful the new material will lessen the frequency of squeaking. In the short term, the Delta COC articulation provided similar functional scores and survivorship and complication rates with the ceramic head mated with crosslinked polyethylene.

LEVEL OF EVIDENCE

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

The 2009 Frank Stinchfield Award: "Hip squeaking": a biomechanical study of ceramic-on-ceramic bearing surfaces

We designed and implemented an in vitro bench test to simulate and identify potential biomechanical causes for hip squeaking with alumina ceramic-on-ceramic bearing surfaces. All bearings were third-generation alumina ceramic with a 32-mm head coupled with a 56-mm acetabular component with a 32-mm ceramic insert. Conditions for testing were normal gait, high load, stripe wear, stripe wear in extreme load, metal transfer, edge wear with extreme load, and microfracture. Each condition was tested two times in dry conditions and two times in a lubricated condition with 25% bovine serum. Squeaking was reproduced in all dry conditions. It occurred quickly with high load, stripe wear, or metal transfer. Once squeaking occurred, it did not stop. Squeaking disappeared for all conditions when a small amount of lubricant was introduced. In lubricated conditions, squeaking was only reproduced for the material transfer condition. Our observations suggest squeaking is a problem of ceramic-ceramic lubrication and that this noise occurs when the film fluid between two surfaces is disrupted. Material (metal) transfer was the only condition that led to squeaking in a lubricated situation.

Alumina inlay failure in cemented polyethylene-backed total hip arthroplasty

Alumina-on-alumina bearings for THA have markedly improved in mechanical properties through advances in technology; however, alumina fracture is still a concern. We retrospectively reviewed 77 patients (82 hips) with cemented alumina-on-alumina THAs to identify factors relating to alumina failure. The mean age of the patients at surgery was 63 years. The prostheses had a cemented polyethylene-backed acetabular component with an alumina inlay and a 28-mm alumina head. Revision surgery was performed because of alumina inlay failure in four hips (three fractures and one dissociation; 5.6%), deep infection in two, and recurrent dislocation in one. The 8-year survival rate was 90.7% with revision for any reason and 94.4% with revision for alumina failure as the end point. There were no differences in age, body mass index, gender, mobility, function, abduction angle, or size of component among the four hips with alumina failure and the remaining 68 hips without it; however, radiolucent lines in the sockets were more apparent in four cases with alumina inlay failure. This alumina-on-alumina THA thus yielded unsatisfactory medium-term results because we observed a high rate of catastrophic alumina inlay failure.

Randomised controlled trial comparing two methods of acetabular cup positioning during total hip arthroplasty

BACKGROUND

Acetabular cup positioning is an important technical aspect in total hip arthroplasty. Most surgeons estimate cup abduction angle during surgery with the insertion rod position according to the patient's body anatomical landmarks or other reference points in the operating room. High acetabular component abduction angle is associated with an increased risk of dislocation, premature polyethylene wear and osteolysis.

METHOD

To evaluate the potential benefits of a new technique for vertical acetabular cup positioning, 100 acetabular cups were randomised to be inserted with or without an inclinometer. Abduction angles were measured on postoperative radiographs by 2 evaluators blind to the treatment group.

RESULTS

Of the cups, 57% (27/47) were positioned within the desirable abduction angle range of 40-49 with the inclinometer, compared with 50% (27/53) by visuospatial perception (p=0.454). The proportion of cups positioned outside a safe angle range of 30-55 was low in both groups: 6% (3/47) for the inclinometer group versus 4% (2/53) for the visuospatial perception group (p=0.536).

CONCLUSION

The use of an inclinometer did not significantly improve the acetabular cup abduction angle obtained by our group of surgeons when compared with visuospatial perception. Newer techniques such as navigation may be useful in further optimising cup positioning and reducing the outliers.

Laboratory studies on the tribology of hard bearing hip prostheses: Ceramic on ceramic and metal on metal

Total hip replacements offer relief to a great many patients every year around the world. With an expected service life of around 25 years on most devices, and with younger and younger patients undergoing this surgery, it is of great importance to understand the mechanisms of their function. Tribological testing of both conventional and hard bearing joint combinations have been conducted in many centres throughout the world, and, after being initially abandoned owing to premature failures, hard bearing combinations have been revisited as viable options for joint replacements. Improved design, manufacturing procedures, and material compositions have led to improved performance over first-generation designs in both metal-on-metal and ceramic-on-ceramic hip prostheses. This paper offers a review of the work conducted in an attempt to highlight the most important factors affecting joint performance and tribology of hard bearing combinations. The tribological performance of these joints is superior to that of conventional metal- or ceramic-on-polymer designs.

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.

Two- to 9-year clinical results of alumina ceramic-on-ceramic THA

From June 1997 to June 2003 we performed 194 total hip arthroplasties on 173 patients using alumina ceramic-on-ceramic bearings as part of a prospective United States Food and Drug Administration/Investigational Device Exemption study. The average patient age at surgery was 49.9 years. Minimum followup time was 2 years (mean 4.3 years, range 2-9 years). We evaluated survival rate, implant- and nonimplant-related complications. Clinical outcomes included the Merle d'Aubigné score. We assessed radiographs for signs of osteolysis, component loosening, and implant wear. No patients had osteolysis and there were no hip dislocations. Implant survivorship for all hips with aseptic revision of any component was 96% (CI, 91-100) at 9 year; survivorship for hips without prior surgery was 99.3%, (CI, 98-100). There was a 1.7% incidence of implant-related complications. Our data help confirm two United States FDA/IDE studies on alumina ceramic-on-ceramic total hip arthroplasty that reported low aseptic revision rates and low revision rates for instability. Total hip arthroplasty using alumina ceramic-on-ceramic implants is a safe and reliable procedure in the comparably young and active patient.

Effect of bisphosphonates on the stimulation of macrophages by alumina ceramic particles: a comparison with ultra-high-molecular-weight polyethylene

Wear particle-induced osteolysis and loosening is a critical process that limits the longevity of total hip arthroplasty. Despite their potential value in the management of aseptic loosening, little is known about the cellular response to bisphosphonates (BPs) in the presence of particulate debris. In the present study, we compared the effect of pamidronate and clodronate, two structurally different bisphosphonates, on the induction of TNF-alpha release by alumina ceramic (Al(2)O(3)) and ultra-high-molecular-weight-polyethylene (UHMWPE) particles. We also looked, by Trypan blue exclusion, at the viability of J774 mouse macrophages incubated with Al(2)O(3) and UHMWPE particles in combination with pamidronate or clodronate. Results showed that pamidronate and clodronate can inhibit UHMWPE particle-induced TNF-alpha release while they had no effect on Al(2)O(3)-stimulated TNF-alpha release. The co-incubation of pamidronate or clodronate and Al(2)O(3) had no effect on the induction by Al(2)O(3) of poly(ADP-ribose)polymerase (PARP) proteolysis and DNA fragmentation. On the other hand, UHMWPE particles had no effect on these apoptotic markers. However, the co-incubation of pamidronate or clodronate with UHMWPE particles led to the appearance of these markers of apoptosis. Al(2)O(3) and UHMWPE particles had no effect on macrophage cell death or the number of macrophages at the end of experiments. Co-incubation of UHMWPE particles with pamidronate and clodronate led to a significant increase in cell death. Interestingly, the number of macrophages co-incubated with particles and pamidronate or clodronate significantly decreased. In conclusion, our results suggest that the effect of BPs on particle-stimulated macrophages is, at least in part, particle composition dependent.

Wear analysis of retrieved ceramic-on-ceramic articulations in total hip arthroplasty: Femoral head makes contact with the rim of the socket outside of the bearing surface

We investigated articular bearing surfaces retrieved from three patients with ceramic-on-ceramic total hip arthroplasties using high-quality alumina. The duration of implantation was 3.5, 3.0, and 2.5 years, respectively. Dislocation of the hip joint after implantation did not occur in any patients. The retrieved prostheses were examined by stereomicroscopy and scanning electron microscopy (SEM). In the main load-bearing area, no wear marks were seen in any sockets. However, in all three cases, stripe scars were observed at the rim of the alumina inlay under stereomicroscopy, despite the lack of indentation in the socket and the stem, which suggests impingement. Such scars were not observed on the load-bearing surface. Under SEM, the scars showed excessive wear, including material excavation, that has not been observed in conventional hip simulator experiments. These findings are similar to those of experiments in which a simulator was programmed to distract the femoral head from the socket. The present results suggest that the femoral head can separate from the socket without neck-socket impingement in vivo.

Appropriate radial clearance of ceramic-on-ceramic total hip prostheses to realize squeeze-film lubrication

OBJECTIVE

Estimation of appropriate radial clearance of ceramic-on-ceramic total hip prostheses to realize squeeze-film lubrication.

BACKGROUND

Some clinical results show that severe wear occurs at ceramic-on-ceramic interfaces of total hip prostheses if the design parameters are improper. Appropriate design is required to realize the optimum lubrication of joint prostheses.

DESIGN

Squeeze-film thickness of total hip prostheses with different radial clearances was numerically estimated under the physiological conditions of normal walking.

METHODS

The changes in the fluid film thickness between ceramic balls and a ceramic cups with radial clearances of various values from 10 to 80 microm were numerically estimated under the assumption of normal walking conditions by means of elastohydrodynamic squeeze-film lubrication theory including the three-dimensional theory of elasticity.

RESULTS

The minimum film thickness remained over 0.02 microm during a few walking steps with a radial clearance under 20 microm and a head diameter of 28 mm. On the other hand, the fluid film was squeezed out during a few steps when the radial clearance was greater than 30 microm.

CONCLUSIONS

Squeeze-film lubrication can be realized in a ceramic-on-ceramic total hip prosthesis if the radial clearance is smaller than 20 microm on a head of 28 mm diameter.

RELEVANCE

Fluid film lubrication is necessary to prevent the severe wear of ceramic joint prostheses. The present investigation shows which radial clearance of ceramic-on-ceramic hip prostheses is appropriate for squeeze-film lubrication under physiological conditions in daily action.

Mechanisms of failure of total hip replacements: lessons learned from retrieval studies

The value of implant retrieval analysis in orthopaedic surgery has been well recognized. Prosthetic devices retrieved for cause at revision surgery (for implant failure) or devices retrieved postmortem from patients with clinically successful reconstructions provide a unique set of specimens that can be studied to evaluate the effect of the implant on the host environment and the effect of the host environment on the implant. A systematic analysis of retrieved components, in combination with histologic, radiographic, and clinical data can provide valuable insights into the mechanisms of failure of the biomaterials used in joint replacement applications. From the hip implant retrieval studies reported to date, it has been established that the local reaction to particulate wear debris initiates the formation of a granulomatous tissue that ultimately invades the bone-implant interface and results in aseptic loosening. Cement mantle defects, noncircumferential porous coatings, and screw holes can serve as preferential access pathways for the progression of this granulomatous process yielding distinctive patterns of implant loosening and osteolysis. Continued surveillance of retrieved devices is strongly recommended to deepen our understanding of implant failure mechanisms and to evaluate the impact of newer designs and materials on the performance of joint replacement devices.

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.

Clinical and simulator wear study of alumina ceramic THR to 17 years and beyond

Three THAs with cementless monolithic alumina ceramic sockets and cementless Co-alloy stems were retrieved because of aseptic loosening after 17 and 24 years. At revision heads and cups were marked for orientation. Maps were drawn of wear patterns with the use of light microscopy and surveyed by SEM. In a simulator experiment 28-mm-diameter alumina heads and liners were used. The cups were mounted inverted in a hip simulator and run with calf serum as the lubricant. The hip loads were 2 kN maximum and a 1-Hz frequency for 20 million cycles. Wear severity was classified into five grades. In retrieved implants, SEM analysis showed that the main wear zones (MWZ) had Grade 4 wear. The peripheral wear zones (PWZ) showed grain pull-out regions (Grade 5 wear). These corresponded to neck-socket impingement and head-acetabular cup separation. Gray was due to transferred CoCr particles from the stem. In the simulator study, the MWZ had only localized areas of grain pull out surrounded by polished surface regions (Grade 4 wear) at 20 million cycles; stripe wear was not seen. The alumina ceramic bearings proved excellent up to 22 years in simulator studies and clinical studies. However, microseparation kinematics would be necessary in the simulator to duplicate the more peripheral wear zones.

Biological reaction to alumina, zirconia, titanium and polyethylene particles implanted onto murine calvaria

Periprosthetic osteolysis is a serious problem that limits long-term survival of total hip arthroplasty. Ceramics have been introduced as a joint surface material to reduce osteolysis due to wear particles. The aim of this study is to investigate the biological reaction of ceramic particles on murine calvarial bone, in comparison with polyethylene and titanium particles. Sixty CL/BL6 mice were divided into five groups according to the materials implanted onto the murine calvariae: control, Al(2)O(3), ZrO(2), high-density polyethylene (HDP) and Ti6Al4V. One week after the implantation, each calvarial tissue was dissected and the release of proinflammatory mediators (IL-1beta, IL-6, TNF-alpha) and bone resorption were assessed. The particles of HDP and Ti6Al4V induced three and two times larger osteolytic lesions than the control, respectively. The levels of IL-1beta and IL-6 were significantly elevated in the medium subcultured with the calvariae of HDP and Ti6Al4V groups. Any particle type did not increase the levels of TNF-alpha. There were no significant differences observed in the levels of proinflammatory mediators or osteolytic area among Al(2)O(3), ZrO(2) and control groups. The inflammatory response and bone resorption induced by ceramic particles were much smaller than those induced by HDP and Ti6Al4V. These biological features suggest the biocompatibility of ceramics as a joint surface material for artificial joints.

Comparison of the cytotoxicity of clinically relevant cobalt-chromium and alumina ceramic wear particles in vitro

Concern over polyethylene wear particle induced aseptic loosening of metal-on-polyethylene hip prostheses has led to renewed interest in alternative materials such as metal-on-metal and alumina ceramic-on-alumina ceramic for total hip replacement. This study compared the effects of clinically relevant cobalt-chromium and alumina ceramic wear particles on the viability of U937 histiocytes and L929 fibroblasts in vitro. Clinically relevant cobalt-chromium wear particles were generated using a flat pin-on-plate tribometer. The mean size of the clinically relevant metal particles was 29.5+/-6.3 nm (range 5-200 nm). Clinically relevant alumina ceramic particles were generated in the Leeds MkII anatomical hip simulator from a Mittelmieier prosthesis using micro-separation motion. This produced particles with a bimodal size distribution. The majority (98%) of the clinically relevant alumina ceramic wear debris was 5-20 nm in size. The cytotoxicity of the clinically relevant wear particles was compared to commercially available cobalt-chromium (9.87 microm+/-5.67) and alumina ceramic (0.503+/-0.19 microm) particles. The effects of the particles on the cells over a 5 day period at different particle volume (microm(3)) to cell number ratios were tested and viability determined using ATP-Lite(TM). Clinically relevant cobalt-chromium particles 50 and 5 microm(3) per cell reduced the viability of U937 cells by 97% and 42% and reduced the viability of L929 cells by 95% and 73%, respectively. At 50 microm(3) per cell, the clinically relevant ceramic particles reduced U937 cell viability by 18%. None of the other concentrations of the clinically relevant particles were toxic. The commercial cobalt-chromium and alumina particles did not affect the viability of either the U937 histiocytes or the L929 fibroblasts.Thus at equivalent particle volumes the clinically relevant cobalt-chromium particles were more toxic then the alumina ceramic particles. This study has emphasised the fact that the nature, size and volume of particles are important in assessing biological effects of wear debris on cells in vitro.

Hydroxyapatite coated stems in younger and older patients with hip arthritis

A primary aim of research in total hip arthroplasty is to extend longevity through improved fixation and decreased wear and osteolysis. Age range of patients receiving hip implants is ever increasing as technology improves and average life span increases. The current report focuses on minimum 10-year results of a proximally hydroxyapatite-coated stem in patients with degenerative joint disease, comparing those 45 years and older (n = 229 hips) with younger patients (n = 41 hips). Clinically, the average Harris hip score is 91 points and 88 points in the older and younger groups, respectively. Mechanical failure rates for the stem are 0.4% and 2.4%, with one stem revision for aseptic loosening and no radiographically loose stems in each age group. Proximal femoral osteolysis is seen more often in younger patients (48% versus 38%), and younger patients (six hip arthroplasties) had reoperation for wear or osteolysis. Therefore, this stem has performed well at a 10-year minimum followup. However, polyethylene wear and osteolysis have led the authors to begin a United States Food and Drug Administration study of an alumina ceramic-on-alumina ceramic bearing surface in conjunction with the same stem. At 2 years minimum followup, there have been no complications related to the ceramic bearing surfaces, no cortical erosions, and no stem revisions for aseptic loosening.

Ceramic-on-ceramic bearings in total hip arthroplasty

The ideal bearing surface for total hip arthroplasty still is being sought. This bearing would be durable, cost-effective, easy to implant, inert, and produce minimal wear debris. Ceramic-on-ceramic bearings have continued to evolve and have enjoyed success in many European centers throughout the past 3 decades. A limited number of early reports from the United States discouraged widespread acceptance and use of ceramic-on-ceramic total hip arthroplasty. Once critically analyzed most of the failures from the early reports are attributable to design and material specific flaws. Vast improvements have been made in ceramic manufacturing leading to even more superior wear characteristics and higher burst strengths. The case for alumina-on-alumina ceramic bearings is becoming stronger as data accumulate clinically and in vitro. In a multicenter, prospective and randomized study, an alumina-on-alumina ceramic bearing is compared with a cobalt chrome-on-polyethylene bearing. After as many as 48 months there has been no significant difference in clinical performance between the two study groups. No ceramic head fracture or ceramic bearing failure has occurred. Therefore, this new alumina-on-alumina ceramic bearing is a safe option for total hip arthroplasty and may provide a more durable prosthesis especially in young and active patients.

Vertical acetabular positioning with an inclinometer in total hip arthroplasty

Vertical acetabular implant positioning is an important technical aspect in total hip arthroplasty. To evaluate the potential benefit of an inclinometer, 50 cup insertions were done on a cadaver pelvis. Acetabular cup vertical angles averaged 44.4 degrees +/- 11.4 degrees by visuospatial perception and 42.2 degrees +/- 3.8 degrees with the inclinometer. All cups were within the safe angle range of 40 degrees to 49 degrees with the inclinometer compared with 64% of cups by visuospatial perception. Use of the inclinometer reduced variability by a factor of 2.0 to 4.5. The addition of an inclinometer for acetabular cup insertion increases the probability of positioning the cup within a vertical safe range during total hip arthroplasty on a cadaver pelvis, suggesting that it could be a useful adjunct in clinical practice.

Alumina-alumina artificial hip joints. Part I: a histological analysis and characterisation of wear debris by laser capture microdissection of tissues retrieved at revision

The aims of this study were to investigate the tissues from uncemented Mittelmeier alumina ceramic-on-ceramic total hip replacements using histological methods and to isolate and characterise the ceramic wear debris using laser capture microdissection and electron microscopy. Tissues from around 10 non-cemented Mittelmeier alumina ceramic on ceramic THRs were obtained from patients undergoing revision surgery. Tissues were also obtained from six patients who were undergoing revisions for aseptic loosening of Charnley, metal-on-polyethylene prostheses. Tissue sections were analysed using light microscopy to determine histological reactions and also the location and content of alumina ceramic wear debris. Tissue samples were extracted from sections using laser capture microdissection and the characteristics of the particles subsequently analysed by TEM and SEM. The tissues from around the ceramic-on-ceramic prostheses all demonstrated the presence of particles, which could be seen as agglomerates inside cells or in distinct channels in the tissues. The tissues from the ceramic-on-ceramic retrievals had a mixed pathology with areas that had no obvious pathology, areas that were relatively rich in macrophages and over half of the tissues had in the region of 60% necrosis/necrobiosis. In comparison, the Charnley tissues showed a granulomatous cellular reaction involving a dense macrophage infiltrate and the presence of giant cells and < 30% necrosis/necrobiosis. The tissues from the ceramic prostheses also showed the presence of neutrophils and lymphocytes, which were not evident in the tissues from the Charnley retrievals. There were significantly more macrophages (p < 0.05), and giant cells (p < 0.01) in the Charnley tissues and significantly more neutrophils (p < 0.01) in the ceramic-on-ceramic tissues. TEM of the laser captured tissue revealed the presence of very small alumina wear debris in the size range 5-90 nm, mean size + SD of 24 +/- 19nm whereas SEM (lower resolution) revealed particles in the 0.05-3.2 microm size range. This is the first description of nanometre sized ceramic wear particles in retrieval tissues. The bi-modal size range of alumina ceramic wear debris overlapped with the size ranges commonly observed with metal particles (10-30 nm) and particles of ultra-high molecular weight polyethylene (0.1-1,000 microm). It is possible that the two size ranges of contributed to the mixed tissue pathology observed. It is speculated that the two types of ceramic wear debris are generated by two different wear mechanisms in vivo, under normal articulating conditions, relief polishing wear and very small wear debris is produced. while under conditions of microseparation of the head and cup and rim contact, intergranular and intragranular fracture and larger wear particles are generated.