Modular Acetabular Components Research Articles

THE ASSOCIATION OF BEARING SURFACE MATERIALS WITH THE RISK OF REVISION FOLLOWING PRIMARY TOTAL HIP ARTHROPLASTY: A COHORT ANALYSIS OF 1,026,481 HIP ARTHROPLASTIES FROM THE NATIONAL JOINT REGISTRY

We investigated the revision rates of primary total hip replacement (THR) reported in the National Joint Registry (NJR) by types of bearing surfaces used.We analysed THR procedures across all orthopaedic units in England and Wales. Our analyses estimated all-cause and cause-specific revision rates. We identified primary THRs with heads and monobloc cups or modular acetabular component THRs with head and shell/liner combinations. We used flexible parametric survival models to estimate adjusted hazard ratios (HR).A total of 1,026,481 primary THRs performed between 2003–2019 are included in the primary analysis (Monobloc: n=378,979 and Modular: n=647,502) with 20,869 (2%) of these primary THRs subsequently undergoing a revision episode (Monobloc: n=7,381 and Modular: n=13,488).Compared to implants with a cobalt chrome head and highly crosslinked polyethylene (HCLPE) cup, the all-cause risk of revision for monobloc acetabular implant was higher for patients with cobalt chrome or stainless steel head and non-HCLPE cup. The risk of revision was lower for patients with a delta ceramic head and HCLPE cup implant, at any post-operative period.Compared to patients with a cobalt chrome head and HCLPE liner primary THR, the all-cause risk of revision for modular acetabular implant varied non-constantly. THRs with a delta ceramic or oxidised zirconium head and HCLPE liner had a lower risk of revision throughout the entire post-operative period.The all-cause and indication-specific risk of prosthesis revision, at different time points following the initial implantation, is lower for implants with a delta ceramic or oxidised zirconium head and a HCLPE liner/cup than commonly used alternatives such as cobalt chrome heads and HCLPE liner/cup.

BEARING SURFACE MATERIALS AND THE RISK OF REVISION FOLLOWING PRIMARY TOTAL HIP ARTHROPLASTY: A COHORT ANALYSIS OF 1,026,481 HIP ARTHROPLASTIES FROM THE NATIONAL JOINT REGISTRY

Hip bearing surfaces materials are typically broadly reported in national registry (metal-on-polyethylene, ceramic-on-ceramic etc). We investigated the revision rates of primary total hip replacement (THR) reported in the National Joint Registry (NJR) by detailed types of bearing surfaces used.We analysed THR procedures across all orthopaedic units in England and Wales. Our analyses estimated all-cause and cause-specific revision rates. We identified primary THRs with heads and monobloc cups or modular acetabular component THRs with detailed head and shell/liner bearing material combinations. We used flexible parametric survival models to estimate adjusted hazard ratios (HR).A total of 1,026,481 primary THRs performed between 2003–2019 were included in the primary analysis (Monobloc cups: n=378,979 and Modular cups: n=647,502) with 20,869 (2%) of these primary THRs subsequently undergoing a revision episode (Monobloc: n=7,381 and Modular: n=13,488).Compared to implants with a cobalt chrome head and highly crosslinked polyethylene (HCLPE) cup, the overall risk of revision for monobloc acetabular implant was higher for patients with cobalt chrome or stainless steel head and non-HCLPE cup. The risk of revision was lower for patients with a delta ceramic head and HCLPE cup implant, at any post-operative period.Compared to patients with a cobalt chrome head and HCLPE liner primary THR, the overall risk of revision for modular acetabular implant varied non-constantly. THRs with a delta ceramic or oxidised zirconium head and HCLPE liner had a lower risk of revision throughout the entire post-operative period.The overall and indication-specific risk of prosthesis revision, at different time points following the initial implantation, is reduced for implants with a delta ceramic or oxidised zirconium head and a HCLPE liner/cup in reference to THRs with a cobalt chrome head and HCLPE liner/cup.

Are Corrosion and Material Loss a Threat for Titanium-Titanium Tapers in Total Hip Arthroplasty Modular Acetabular Components?

BackgroundExtensive research has reported on fretting corrosion and material loss for a variety of metal taper interfaces in orthopedic devices. For modular acetabular shell-liner constructs, the interfaces studied thus far have consisted of mixed-metal pairings, and the risk of fretting corrosion and material loss for the all-titanium (Ti) shell-liner taper junction in one ceramic-on-ceramic (COC) design remains poorly understood. We asked: do Ti shell-liner taper interfaces in COC total hip arthroplasty devices show in vivo evidence of (1) fretting and/or corrosion, and (2) quantifiable potential material loss? MethodsWe examined 22 shell-liner pairs and 22 single liners from retrieved COC components. The taper interface surfaces were assessed for fretting corrosion using a semiquantitative scoring method and imaged with scanning electron microscopy. A subcohort of components was measured with a coordinate measuring machine, and volumetric material loss and maximum wear depth were calculated. ResultsFretting corrosion at the taper interfaces was minimal to mild for 95% of liners and 100% of shells. Imaging revealed fretting marks within a band of corrosion on some implants and evidence of corrosion not in the proximity of mechanical damage. Estimated material loss ranged from 0.2 to 1.3 mm3 for liners, and 0.5 to 1.1 mm3 for shells. Maximum wear depth for all components was 0.03 mm or less. ConclusionsOur results indicate that, compared to other taper junctions in total joint arthroplasty, the risk of corrosion and material loss may be minimal for Ti shell-liner interfaces.

Effect of Bone Coverage on Acetabular Implant Stresses in Standard and Dual-Mobility Total Hip Arthroplasty Constructs: A Finite Element Model.

Although mechanical stress in total hip arthroplasty modular head-neck junctions is thought to contribute to the risk of trunnionosis and related metal ion disease in total hip arthroplasty, little is known about mechanical stress in the modular acetabular components. Recent retrieval analyses of dual-mobility constructs have demonstrated corrosion between liner and shell in some dual-mobility acetabular components. The objective of this study was to evaluate acetabular stress as a function of acetabular bone coverage, component modularity, and femoral head diameter. A parametric finite element model was created. The acetabulum was set at 40° of abduction and 15° of anteversion; superolateral bone loss up to 50° was modeled; and 28-mm, 32-mm, 36-mm, and 40-mm head sizes were simulated in stance phase of gait. Fixed polyethylene-bearing, monoblock and modular dual-mobility (MDM) acetabular components were evaluated. For traditional fixed-bearing components, the largest peak stress, 49.5 MPa, was observed with 50° of bone loss and a 28-mm head. The lowest peak stress, 6.3 MPa, occurred with complete bone coverage and a 36-mm head. Peak stress in the MDM construct, 25.1 MPa, concentrated in the chromium-cobalt portion of the construct. Larger head diameters are associated with decreased stress in the acetabular component when bone loss is present. An MDM construct with a stiff inner liner may decrease overall stress in the acetabular construct, but focally increased stress near the rim of uncovered acetabular components may increase the risk of metal-on-metal corrosion. [Orthopedics. 2021;44(5):280-284.].

Dissociation of Acetabular Polyethylene Liners With a Morse Taper Design

BackgroundPolyethylene liner dissociation is an uncommon complication of hip replacement. Dissociation has been associated with particular acetabular component designs. This study reviewed acetabular liner dissociations in a specific modular cup with a Morse taper locking mechanism that has not been previously reported. MethodsThe senior author performed 655 primary total hip arthroplasties with one particular design of acetabular component using Class A polyethylene liners and metal head articulation. Cases with revision surgery performed for acetabular liner dissociation were reviewed. ResultsSeven of 655 patients with this cup underwent revision surgery for a dissociated liner. Liner dissociation occurred at a mean of 73 months postoperatively. Patients presented with new-onset hip pain or squeaking, 4 of which developed symptoms acutely. Two patients treated with polyethylene liner exchange into the same cup required a second revision surgery for recurrent dissociation. ConclusionPolyethylene liner dissociation is an infrequent but possible complication associated with modular acetabular components using a Morse taper locking. Providers should be vigilant with long-term follow-up of patients with this acetabular system for patient complaints of catching or squeaking. Patients treated for liner dissociation should not have a new liner placed into the same acetabular shell given the risk for further dissociation.

Acetabular Liner Dissociation: A Comparative Study of Two Contemporary Uncemented Acetabular Components.

BackgroundThere are a number of reports of polyethylene liner dissociation of third-generation modular acetabular components. This study compares our experience with 2 contemporary systems to determine whether this is an implant- or class-specific problem.MethodsThis is a single-center retrospective study of 961 primary total hip arthroplasties using 2 third-generation modular cementless acetabular shells: Pinnacle (535) and R3 (426) with a polyethylene liner. Details of all revisions were obtained from local databases and the New Zealand Joint Registry. Kaplan-Meier survival curves were calculated for all-cause revision, acetabular reoperation (including liner exchange), and liner dissociation.ResultsThere were 17 revisions in group 1 (Pinnacle; DePuy Synthes): 17 for recurrent dislocation, 6 for liner dissociations (1.12%), 3 for femoral loosening, and one for deep infection. In group 2 (R3; Smith and Nephew), there were 4 revision procedures: one for infection, 2 for dislocation, and one femoral revision for periprosthetic fracture. There were significantly higher proportions revised in group 1 for all-cause revision, acetabular reoperation, and dissociation (P = .024 to 0.038). The 7-year survival for all-cause revision was 96.1% for Pinnacle and 99.0% for R3 (P = .022), and that in the acetabular reoperation group was 96.9% for Pinnacle and 99.3% for R3 (P = .035).ConclusionsThere was a higher revision rate for the Pinnacle acetabular component than for the R3 at 7 years. This was mainly due to polyethylene liner dissociation that can occur early or late. It appears to be a problem specific to the Pinnacle cup design rather than a feature of similar third-generation acetabular components.

Highly Porous Tantalum Acetabular Components Without Ancillary Screws Have Similar Migration to Porous Titanium Acetabular Components With Screws at 2 Years: A Randomized Controlled Trial

BackgroundIt is proposed that highly porous coatings on acetabular components, such as a porous tantalum coating, provide adequate fixation without ancillary screw fixation in primary total hip arthroplasty (THA). However, tantalum acetabular components have been associated with higher rates of revision than other uncemented components in national registries. The aim of this randomized controlled trial is to determine whether the early migration of a solid-backed tantalum acetabular component was no greater than that of a titanium acetabular component with ancillary screw fixation that has proven good clinical results. MethodsSixty-six patients aged 40 to 64 years, with osteoarthritis and Charnley grade A or B activity grade and who underwent primary THA, were recruited into the trial. Patients were randomized intraoperatively to receive either the tantalum or titanium acetabular component. All patients received the same cemented polished tapered femoral stem, 28-mm cobalt-chromium femoral head, and highly cross-linked polyethylene liner. Acetabular component migration was measured using radiostereometric analysis at 4-6 days postoperatively and at 6 weeks, 3 months, 1 and 2 years following THA. ResultsThe mean proximal migration at 2 years for the tantalum cohort was 0.17 mm (95% confidence interval, 0.09-0.24) which was no greater than that of the titanium cohort which was 0.19 mm (0.07-0.32). Harris hip scores and functional activity scores were similar between groups. ConclusionThese results demonstrate that early stability can be achieved without ancillary screw fixation through the use of a highly porous high friction coating on a solid-backed modular acetabular component. Level of EvidenceLevel I.

Evaluation and Treatment of Patients With Acetabular Osteolysis After Total Hip Arthroplasty.

As the demand for total hip arthroplasty (THA) continues to increase, the burden of revision THA is also expected to increase. Although the quality of polyethylene has improved markedly, osteolysis continues to be a risk for older designs and younger, active patients. Although progressive but typically asymptomatic in early stages, osteolysis can result in component failure and complicate revision surgery. Serial radiographs are paramount for monitoring progression. Although select cases may be treated with observation, surgery should be considered based on age, activity level, and projected life span. Well-fixed, noncemented modular acetabular components may be treated with curettage and bone grafting, as well as having to bear liner exchange with retention of the acetabular shell. However, in the setting of osteolysis, it is controversial whether bone grafting and component retention is superior to cup revision. This review explores the pathophysiology of osteolysis after THA and provides a comprehensive analysis of the evaluation and treatment of patients with osteolysis.

Metal-on-Metal Total Hip Arthroplasty at Five to Twelve Years Follow-Up: A Concise Follow-Up of a Previous Report

BackgroundConcern has arisen regarding potential complications with modular metal-on-metal (MoM) acetabular components in total hip arthroplasty. The purpose of this study was to analyze longitudinally the longer term results of a previously reported cohort of patients utilizing a cementless modular acetabular component with a MoM bearing. MethodsOne hundred sixty-nine consecutive but selected total hip arthroplasties were performed in 148 patients at 2 institutions using a modular acetabular MoM component. One hundred thirty-nine patients (158 hips) were living at minimum 5 years, 1 patient (1 hip) was lost to follow-up and 8 patients (10 hips) were deceased. Patients were evaluated clinically in terms of revision as well as radiographically. Additional testing (metal ion levels, advanced imaging) was performed when concerns for adverse local tissue reaction (ALTR) arose. ResultsThere were 6 (3.8%) additional hips revised since the prior report for a total of 7 hips (4.4%) revised at 5-12 year follow-up. All newly revised hips (3.8%) demonstrated ALTR. There were 7 (4.7%) additional cases of radiographically detected acetabular osteolysis and 7 (4.7%) cases of femoral osteolysis. ConclusionLongitudinal evaluation of a modular MoM bearing surface acetabular component demonstrated increased rates of ALTR and osteolysis at longer duration follow-up. Although greater than 95% of hips in this study performed well at 5-12 years, when comparing the results to metal-on-polyethylene bearings using the same acetabular component, the results were inferior. Longitudinal surveillance is warranted with this design and this bearing surface couple as cases of ALTR and osteolysis increased with longer follow-up.

Adverse Reactions to Metal on Metal Are Not Exclusive to Large Heads in Total Hip Arthroplasty

There is some suggestion that smaller diameter heads in metal-on-metal total hip arthroplasty (MoM THA) may be less prone to the adverse reactions to metal debris (ARMD) seen with large-diameter heads. We reviewed our population of patients with small head (≤ 32 mm) MoM THA to determine (1) the frequency of ARMD; (2) potential risk factors for ARMD in this population; and (3) the etiology of revision and Kaplan-Meier survivorship with revision for all causes. Small-diameter head MoM devices were used in 9% (347 of 3753) of primary THAs during the study period (January 1996 to March 2005). We generally used these implants in younger, more active, higher-demand patients. Three hundred hips (258 patients) had MoM THA using a titanium modular acetabular component with a cobalt-chromium tapered insert and were available for review with minimum 2-year followup (mean, 10 years; range, 2-19 years). Complete followup was available in 86% of hips (300 of 347). Clinical records and radiographs were reviewed to determine the frequency and etiology of revision. Kaplan-Meier survivorship analysis was performed. ARMD frequency was 5% (14 of 300 hips) and represented 70% (14 of 20) of revisions performed. Using multivariate analysis, no variable tested, including height, weight, body mass index, age, cup diameter, cup angle, use of screws, stem diameter, stem type, head diameter, preoperative clinical score, diagnosis, activity level, or sex, was significant as a risk factor for revision. Twenty hips have been revised: two for infection, four for aseptic loosening, and 14 for ARMD. Kaplan-Meier analysis revealed survival free of component revision for all causes was 95% at 10 years (95% confidence interval [CI], 91%-97%), 92% at 15 years (95% CI, 87%-95%), and 72% at 19 years (95% CI, 43%-90%), and survival free of component revision for aseptic causes was 96% at 10 years (95% CI, 92%-98%), 92% at 15 years (95% CI, 88%-95%), and 73% at 19 years (95% CI, 43%-90%). The late onset and devastating nature of metal-related failures is concerning with this small-diameter MoM device. Although the liner is modular, it cannot be exchanged and full acetabular revision is required. Patients with all MoM THA devices should be encouraged to return for clinical and radiographic followup, and clinicians should maintain a low threshold to perform a systematic evaluation. Symptomatic patients should undergo thorough investigation and vigilant observation for ARMD. Level IV, therapeutic study.

The influence of the strength of bone on the deformation of acetabular shells: a laboratory experiment in cadavers.

Concerns have been raised that deformation of acetabular shells may disrupt the assembly process of modular prostheses. In this study we aimed to examine the effect that the strength of bone has on the amount of deformation of the acetabular shell. The hypothesis was that stronger bone would result in greater deformation. A total of 17 acetabular shells were inserted into the acetabula of eight cadavers, and deformation was measured using an optical measuring system. Cores of bone from the femoral head were taken from each cadaver and compressed using a materials testing machine. The highest peak modulus and yield stress for each cadaver were used to represent the strength of the bone and compared with the values for the deformation and the surgeon's subjective assessment of the hardness of the bone. The mean deformation of the shell was 129 µm (3 to 340). No correlation was found between deformation and either the maximum peak modulus (r² = 0.011, t = 0.426, p = 0.676) or the yield stress (r² = 0.024, t = 0.614, p = 0.549) of the bone. Although no correlation was found between the strength of the bone and deformation, the values for the deformation observed could be sufficient to disrupt the assembly process of modular acetabular components.

Mid-Term Clinical and Radiographic Outcomes of Porous Tantalum Modular Acetabular Components for Hip Dysplasia

It is still challenging to perform successful cementless cup fixation during total hip arthroplasty for hip dysplasia. In this multicenter study we evaluated the clinical results of porous tantalum modular acetabular cups (TM cups) in 45 dysplastic hips with a mean follow-up period of 9.8 years. The mean Japanese Orthopaedic Association hip score improved from 48.2 preoperatively to 92.1 at the most recent follow-up. All of the cups were radiographically stable with no evidence of progressive radiolucencies or osteolysis regardless of bone grafting. Sixteen hips with bone grafts showed the integration of grafted bone without any radiolucencies. There were no revisions of TM cups. The use of TM cups for dysplastic hips provided satisfactory 10-year clinical and radiographic results.

Comparison Between Preassembled and Modular Cups in Primary Cementless Total Hip Arthroplasty: A Two-Year Minimum Follow-up Study

We prospectively analyzed 83 patients who underwent ceramic-on-ceramic THA using preassembled (n=22) or modular acetabular components (n=61) between June 2010 and June 2012. There were no significant differences in mean postoperative radiographic outcomes, functional outcomes, or complications between the two groups. Both groups showed satisfactory performance at the 2year follow up. Only the gender of the patients was significantly different between the two groups. Half of the women had smaller acetabular diameters accommodating a cup size of only 48-50-mm. Although a preassembled cup with a 36-mm ceramic liner is proven to be safe in the short term, future research should focus on evaluating the long-term risks.

Do Monoblock Cups Improve Survivorship, Decrease Wear, or Reduce Osteolysis in Uncemented Total Hip Arthroplasty?

Monoblock acetabular components used in uncemented total hip arthroplasty (THA) have certain mechanical characteristics that potentially reduce acetabular osteolysis and polyethylene wear. However, the degree to which they achieve this goal is not well documented. The purpose of this study was to use a systematic review of controlled trials to test the hypothesis that monoblock cups have superior (1) polyethylene wear rate; (2) frequency of cup migration; (3) frequency of acetabular osteolysis; and (4) frequency of aseptic loosening compared with modular components used in uncemented THA. A systematic search was conducted in the Medline, Embase, and Cochrane electronic databases to assemble all controlled trials comparing monoblock with modular uncemented acetabular components in primary THA. Included studies were considered "best evidence" if the quality score was either ≥ 50% on the Cochrane Back Review Group checklist or ≥ 75% the Newcastle-Ottawa quality assessment scale. A total of seven publications met our inclusion criteria. Best evidence analysis showed no difference in polyethylene wear rate, the frequency of cup migration, and aseptic loosening between monoblock and modular acetabular components. No convincing evidence was found for the claim that lower frequencies of acetabular osteolysis are observed with the use of monoblock cups compared with modular uncemented cups. The purported benefits of monoblock cups were not substantiated by this systematic review of controlled studies in that polyethylene wear rates and frequencies of cup failure and acetabular osteolysis were similar to those observed with modular implants. Other factors should therefore drive implant selection in cementless THA.

Early results of serum metal ions change and its impact on host immunity after metal-on-metal total hip arthroplasty

Objective To compare the serum metal ion levels and host immunologic response of patients received non-modular,large-head metal-on-metal total hip arthroplasty (THA,Durom) with those received modular titanium acetabular component (Trilogy) using conventional head sizes and metal-on-highly cross-linked polyethylene articulations at mean 2-year follow-up interval.Methods A continuous series of 32 consecutive patients (32 hips) accepted THA with a Durom large head metal-on-metal articulation between January 2008 and December 2010 was as study group (Durom Group).From all the patients who received THA with Trilogy prosthesis at the same period,32 patients matched the Durom group in age,gender and body mass index (BMI) were chosen to form the Trilogy group.Another 32 healthy volunteers also matched the Durom group were chosen to form the control group.At the final follow-up,the serum metal ion levels,host immunologic response were evaluated.Results The mean follow-up time for Durom group was 24.9 months (range,15-34 months) compared to 25.53 months (range,15-48 months) for Trilogy group.Co and Cr levels in Durom group were 4.33 and 1.95 times as high as those in Trilogy group.There was no statistically significant difference in serum C3,C4,IgA,IgG,IgM value in three groups.CD3+,CD4+ and CD8+cells in Durom group decreased significantly compared with Trilogy and control groups.The interferon-γ(IFN-γ) level in Durom group was significantly higher than that in Trilogy and control groups.Conclusion The serum cobalt and chromium levels in patients received Durom metal-on-metal THA elevated significantly in early period.Meanwhile,some amount of impact on host cell mediated immunity occurred. Key words: Arthroplasty, replacement, hip; Serum; Metals; Ions; Immunity, celluler; Antibody formation

Failure analysis of sandwich-type ceramic-on-ceramic hip joints: A spectroscopic investigation into the role of the polyethylene shell component

The mechanisms leading to systematic failure in modular acetabular components with a sandwich insertion (alumina/polyethylene/titanium) have been reconsidered in light of the newly collected Raman spectroscopic results. Raman assessments were conducted on the polyethylene shells, which belonged to a series of six failed sandwich implants with in vivo lifetimes ranging between 2 and 9yr. With only one exception, all implants commonly showed dislodgment of the polyethylene shell during radiographic analyses prior to revision surgery. The polyethylene shell slipped out of the backing titanium shell, while always remaining integer to the ceramic liner. Four implants fractured at the ceramic liners, but their fractures occurred according to distinctly different patterns, which could be rationalized and classified. The insertion of the polyethylene layer, originally conceived to reduce the rigidity of the ceramic-on-ceramic bearing and to prevent impingement between the ceramic liner rim and the femoral neck, played a role in implant failure with its initial (asymmetric) thickness reduction due to creep deformation (eventually followed by cup rotation and backside wear). The results of the present spectroscopic investigation suggest that a simplistic failure classification of the sandwich-type implant as a “ceramic fracture failure” could be misleading and might represent a confounding factor in judging about the reliability of modern ceramic implants.

Clinical and radiographic evaluation of total hip arthroplasties using porous tantalum modular acetabular components: 5-year follow-up of clinical trial

Objectives: Porous tantalum is a biomaterial newly applied for artificial joints. We present here 5-years follow-up report of a multicenter clinical trial of total hip arthroplasties (THA) with porous tantalum modular acetabular component (modular PTC).Methods: Study participants received 82 hips in 79 cases, with 61.2 months follow-up on average. Age at operation was 60.9 years. Clinical results were evaluated using Merle d’Aubigne Postel score. Presence of implant loosening, periacetabular radiolucency, osteolysis, and gap filling were examined for radiographic results.Results: Merle d’Aubigne Postel score improved from 10.0 to 16.4 points. All PTC were radiographically stable, with no evidence of progressive radiolucencies. Average polyethylene wear rate was 0.004 mm/year, with no periacetabular osteolysis. Fifteen hips (18.3%) showed a gap >1 mm; however, all showed bone filling within 12 months. PTC with oversized reaming was significantly less likely to have a gap. No implant failure was noted related to modularity. Resulting survival rate of modular PTC was 100% at 5 years.Conclusions: Modular PTC showed excellent results at 5-years of follow-up. Some hips showed periacetabular gaps, which were filled with bone within 1 year. Further follow-up was needed to determine long-term efficacy.

Clinical and radiographic evaluation of total hip arthroplasties using porous tantalum modular acetabular components: 5-year follow-up of clinical trial

Porous tantalum is a biomaterial newly applied for artificial joints. We present here 5-years follow-up report of a multicenter clinical trial of total hip arthroplasties (THA) with porous tantalum modular acetabular component (modular PTC). Study participants received 82 hips in 79 cases, with 61.2months follow-up on average. Age at operation was 60.9years. Clinical results were evaluated using Merle d'Aubigne Postel score. Presence of implant loosening, periacetabular radiolucency, osteolysis, and gap filling were examined for radiographic results. Merle d'Aubigne Postel score improved from 10.0 to 16.4 points. All PTC were radiographically stable, with no evidence of progressive radiolucencies. Average polyethylene wear rate was 0.004mm/year, with no periacetabular osteolysis. Fifteen hips (18.3%) showed a gap >1mm; however, all showed bone filling within 12months. PTC with oversized reaming was significantly less likely to have a gap. No implant failure was noted related to modularity. Resulting survival rate of modular PTC was 100% at 5years. Modular PTC showed excellent results at 5-years of follow-up. Some hips showed periacetabular gaps, which were filled with bone within 1year. Further follow-up was needed to determine long-term efficacy.

Second-generation Modular Acetabular Components Provide Fixation at 10 to 16 Years

First-generation modular titanium fiber-metal-coated acetabular components had high rates of wear, pelvic osteolysis, and liner dissociation. Second-generation components were designed to reduce the incidence of these problems but it is unclear whether the changes achieved these goals. We asked the following questions: (1) Is the risk of revision surgery for loosening, wear, or liner dissociation low with the second-generation acetabular component? (2) Is the rate of pelvic osteolysis low? (3) Can the liner be exchanged without bone cement? We retrospectively reviewed prospectively collected data from 99 patients (118 hips) undergoing THAs with one second-generation modular titanium acetabular component with routine screw fixation and conventional polyethylene. The minimum followup was 10 years (mean, 12 years; range, 10-16 years). We obtained Harris hip scores and examined radiographs for loosening and osteolysis. At last followup, all acetabular components were well fixed and no titanium shell had been revised or removed. No liner had dissociation. At most recent followup, the mean Harris hip score was 89. We observed pelvic osteolysis in eight hips (7%). There were three reoperations for dislocation (head-liner exchange only) and three loose femoral components revised. Two liners (at 11 and 14 years) were exchanged for wear-pelvic osteolysis. This second-generation modular titanium fiber-metal-coated acetabular component with screw fixation had no loosening, no liner dissociation, and a low rate of pelvic osteolysis at 10 to 16 years. Liner exchange is practical without use of cement. We continue to use this component with highly crosslinked polyethylene liners. Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Liner Exchange and Bone Grafting: Rare Option to Treat Wear & Lysis of Stable TKAs

Liner exchange and bone grafting are commonly performed for wear and osteolysis around well-fixed modular acetabular components that otherwise would require structural allografting and revision THA. However, liner exchange in the face of substantial lysis around TKA has been performed rarely with reports of failure rates of up to 25% at 3 year followup. We therefore evaluated the technique of liner exchange and bone grafting for cases of wear and extensive osteolysis around TKAs in which the components were well-fixed and well-aligned to determine (1) rerevision rates; (2) fate of the bone graft; (3) radiographic loosening rates; and (4) functional scores. We retrospectively reviewed 22 patients (25 knees) who underwent revision TKA with exchange of the modular polyethylene insert and bone grafting in cases with well-fixed components and large areas of osteolysis (up to 54 cm(2) on a single projection) at the time of revision. The average area of osteolysis was 21 cm(2) and 10 cm(2) on the AP projection of the femur and tibia, respectively. On the lateral projection, the average area of osteolysis for the femur and tibia was 22 cm(2) and 9.3 cm(2). Minimum clinical and radiographic followup was 22 and 22 months (average, 61 and 59; range, 22-142 and 22-130, respectively). One of the 25 knees was revised for aseptic loosening or recurrence of osteolysis. On radiographs, 84.6% and 70% of femoral and tibial osteolytic lesions, respectively, showed evidence of complete or near complete graft incorporation. The remaining lesions showed evidence of partial graft incorporation with the exception of one tibial lesion, which was in the revised case. All other components were well fixed with no evidence of radiographic loosening. In this selected series of cases with extensive osteolysis around well-fixed and well-aligned TKAs, liner exchange and bone grafting provided durable midterm results with extensive graft incorporation. Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.