Modular Cup Research Articles

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.

An isoelastic monoblock cup versus a modular metal-back cup: a matched-pair analysis of clinical and radiological results using Einzel-Bild-Röntgen-Analyse software

IntroductionBone preservation and long-term survival are the main challenges in cementless total hip arthroplasty (THA). A good bone stock is especially important for adequate anchorage of the cup in revision cases. However, the optimal acetabular cup design for preserving good bone stock is still unclear. We aimed to compare clinical outcome, radiological alterations, migration, and wear at mid-term for two different cup types.Materials and methodsThis retrospective matched-pair study was performed using the data for 98 THA cases treated with a monoblock cup composed of vitamin E-blended highly cross-linked polyethylene (VEPE; monoblock group) or a modular cup composed of a highly cross-linked polyethylene (HXLPE) without an antioxidant (modular group). Clinical results were evaluated using the Harris Hip Score (HHS). The obtained radiographs were analyzed for radiological alterations, migration, and wear using Einzel-Bild-Röntgen-Analyse (EBRA) software.ResultsThe mean follow-up duration was 73.2 ± 19.2 months (range: 32–108 months) and 60.5 ± 12.2 months (range: 20–84 months) in the monoblock and modular groups, respectively. HHS improved to 95.7 points in the monoblock group and 97.6 points in the modular group, without significant differences (p = 0.425). EBRA measurements were obtained in all cases. Acetabular bone alterations were not detected on radiological assessments. Mean cup migration was 1.67 ± 0.92 mm (range: 0.46–3.94 mm) and 1.24 ± 0.87 mm (range: 0.22–3.62 mm) in the monoblock and modular groups. The mean wear rate was 0.21 ± 0.18 mm (range: 0.00–0.70 mm) and 0.20 ± 0.13 mm (range: 0.00–0.50 mm) in the monoblock and modular groups. Both migration and wear pattern showed no significant differences (p = 0.741 and 0.243). None of the cases required revision surgery, yielding an implant survival rate of 100% in both groups.ConclusionThe isoelastic press-fit monoblock VEPE cup and modular metal-back HXLPE cup showed equivalent mid-term wear and cup migration. Long-term studies are required to determine the effects of modularity, isoelasticity, and polyethylene stabilization with vitamin E on cup loosening and survival rates.

Modular Dual Mobility Cup: A Matched Short-Term Study

Purpose: Instability remains one of the main problems after primary complex and revision hip surgery. The introduction of modular Dual Modular Cup (modular DMC) has helped to overcome some of the limitations of standard DMC. The aim of this study was to review the clinical, radiological outcomes and rate of complications with the use of these kind of constructs.

Revision in Ceramic-on-Ceramic and Ceramic-on-Polyethylene Bearing in Primary Total Hip Arthroplasty with Press-fit Cups: A Systematic Review and Meta-analysis of Different Methodological Study Designs.

The influence of bearing on revision, especially in press-fit modular cup total hip arthroplasty (THA), remains underexposed. A systematic literature review was conducted in PubMed, Embase, Cochrane Library, and ClinicalTrials.gov in line with the PRISMA guidelines. The primary outcome was overall revision between ceramic-on-ceramic (CoC) and all sorts of ceramic-on-polyethylene (CoPE) bearings. As secondary outcomes complications and reasons for revision were compared between bearings. Outcomes were presented in subgroups based on study design (randomized controlled trials (RCT), non-randomized comparative, and registry studies). The quality of evidence was assessed using the GRADE. The risk of bias was assessed using the Cochrane collaboration's tool and the MINORS criteria. This meta-analysis included twelve RCTs, three non-randomized comparative studies and two registry studies, including 38,772 THAs (10,909 CoPE and 27,863 CoC). Overall revision showed a lower risk in CoPE compared to CoC in the two registry studies (HR 0.71 (95%CI 0.53; 0.99)) (very low-quality GRADE evidence). In RCTs and non-randomized comparative studies, no difference was observed (low-quality GRADE evidence). Loosening, dislocation, infection, and postoperative periprosthetic fracture showed no significant differences in risk ratio for all designs. The lower risk of overall revision in registry studies of primary THA with a press-fit modular cup using CoPE bearing compared to CoC should be considered preliminary since this outcome was just slightly significant, based on very low-quality GRADE evidence and based on only two studies with several limitations. Since no difference was observed in the other methodological designs and the separate reasons for revision showed no significant difference in all designs either, no preference for CoC or CoPE can be expressed, and therefore both seem suitable options based on the available literature. More comparative long-term studies are needed to confirm the potential advantages of wear-reduction of both bearings since the currently available literature is limited.

Serum Metal Ions in Contemporary Monoblock and Modular Dual Mobility Articulations.

BackgroundQuestions exist about the release of cobalt and chromium ions from dual mobility (DM) cups. Modular implants, with potential backside wear between the cobalt-chromium liner and titanium cup, are of particular concern. This study compares the metal ion profile of patients with contemporary monoblock and modular DM articulations from two commonly used designs.MethodsCobalt and chromium serum levels were measured one year after surgery in a prospective cohort of patients undergoing total hip arthroplasty with a DM construct. Ion levels were detected above 1 μg/L. Clinical and surgical data were correlated with the ion levels for analysis.ResultsOverall, 29% of the patients had levels above 1 μg/L of either ion. More patients with modular cups had detectable ions than patients with monoblock cups (39% vs 20%, P = .05). Cobalt was more commonly detected in the monoblock group, and chromium was more commonly detected in the modular group (P = .05). There were no differences in the actual ion levels between the groups (1.35 μg/L vs 1.64 μg/L, P = .44, for cobalt and 1.35 μg/L vs 1.31 μg/L, P = .77, for chromium). No patient underwent revision during the follow-up period.ConclusionsWe found similar cobalt and chromium levels in patients with monoblock and modular DM cups. More patients in the modular group had detectable ions. Cobalt was more frequently detected in the monoblock group. These results suggest that both implants are performing well in the short term, but further follow-up is needed to determine whether the differences found are of clinical significance.

Mid-term outcomes of tantalum cup\u2013 a single centre study

IntroductionThe cementless acetabular implants are commonly used in primary and revision hip arthroplasty. Reconstruction of acetabulum in case of bone defects can be challenging. The aims of this single center study are to review the mid-term outcomes of porous tantalum cups (TM) and evaluate complications.MethodsThe midterm outcome of a trabecular metal tantalum modular uncemented cup was evaluated in 59 hips in 58 patients. In our group, we had 23 males and 35 females. The mean age was 70.11 years (range, 30 to 87 years). Four patients were lost to follow-up and 13 died during the period without having further surgeries attributed to the hip arthroplasty. The remaining 41 patients (42 revision hip arthroplasties) had complete data available.ResultsThe mean follow-up was 87 months, ranging from 24 to 144 months. Standard pelvic anteroposterior (AP) radiographs were used to assess and preoperatively classify acetabular defects as per Paprosky classification. The serial radiographs showed excellent stability, bone opposition and graft incorporation. Four patients had further surgeries. Two of these were due to infection (one superficial and one deep infection). One of the patients had washout and then removal of metal work, the other patient only had a washout and symptoms settled. One patient had vascular compromise and went for surgery to stem the bleeding. One patient had re-revision due to stem loosening and hence required surgery but the revision cup remained stable. We noted a 96% survival at an average of 7.2 years follow-up.ConclusionThe mid-term results with the trabecular metal cementless cup appeared to be promising in both primary and revision hip arthroplasty, even in the presence of considerable bone loss which requires bone grafting and augments.Level of evidenceIV.

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.

Survival of monoblock RM vitamys compared with modular PINNACLE cups: mid-term outcomes of 200 hips performed by a single surgeon.

Monoblock cups have theoretical advantages over modular cups; however, their superiority in terms of survival has not been confirmed in comparative studies. We compared the mid-term survivorship of 107 RM Pressfit vitamys monoblock cups (Mathys Ltd., Bettlach, Switzerland) with 93 modular pressfit Pinnacle cups (DePuy Synthes, Warsaw, IN, USA). All cases were registered in the Arthroplasty Registry Thessaloniki and performed by a senior surgeon through the same approach between 2013 and 2014. The groups were comparable in sex distribution, preoperative diagnosis, follow-up, cup diameter, head diameter, type and use of screws, HOOS and HSS preop scores; the recipients of RM cup were significantly younger. 3 sockets were revised. The 6-year survival for any reason was 99.1% for the RM and 97.8 % for the PINNACLE group. There was no difference in survival for aseptic loosening and any reason between groups (log-rank test p = 0.921 and p = 0.483, respectively). The age (95% CI, 0.79-1.1), sex (95% CI, 0.2-45.0), cup diameter (95% CI, 0.18-1.1), head diameter (95% CI, 0.004-6.2), preoperative diagnosis and use of screws (95% CI, 0.02-4.3), did not influence hazard ratio for revision between groups. HHS and HOOS were comparable at the last follow-up. Our study demonstrated that both cup designs had similar revision rates at mid-term follow-up, regardless the fact that the RM vitamys was used in a cohort of younger patients; which according to the literature would have led to earlier failures. Further long-term data are needed to evaluate the superiority of RM vitamys in the clinical setting, especially in the young.

Biomechanical behavior of modular acetabular cups made of poly-ether-ether-ketone: A finite element study.

After total hip arthroplasty, stress-shielding is a potential risk factor for aseptic loosening of acetabular cups made of metals. This might be avoided by the use of acetabular cups made of implant materials with lower stiffness. The purpose of this numerical study was to determine whether a modular acetabular cup with a shell made of poly-ether-ether-ketone or poly-ether-ether-ketone reinforced with carbon fibers might be an alternative to conventional metallic shells. Therefore, the press-fit implantation of modular cups with shells made of different materials (Ti6Al4V, poly-ether-ether-ketone, and poly-ether-ether-ketone reinforced with carbon fibers) and varying liner materials (ceramics and ultra-high-molecular-weight polyethylene) into an artificial bone cavity was simulated using finite element analysis. The shell material had a major impact on the radial shell deformation determined at the rim of the shell, ranging from 17.9 µm for titanium over 92.2 µm for poly-ether-ether-ketone reinforced with carbon fibers up to 475.9 µm for poly-ether-ether-ketone. Larger radial liner deformations (up to 618.4 µm) occurred in combination with the shells made of poly-ether-ether-ketone compared to titanium and poly-ether-ether-ketone reinforced with carbon fibers. Hence, it can be stated that conventional poly-ether-ether-ketone is not a suitable shell material for modular acetabular cups. However, the radial shell deformation can be reduced if the poly-ether-ether-ketone reinforced with carbon fiber material is used, while deformation of ceramic liners is similar to the deformation in combination with titanium shells.

Total hip arthroplasty to treat acetabular protrusions secondary to rheumatoid arthritis

BackgroundThe treatment of acetabular protrusions during total hip arthroplasty of patients with rheumatoid arthritis is difficult. A lack of bone stock, deficient medial cup support, and medialization of the joint center in those with protrusio acetabuli must be addressed during acetabular reconstruction. The purpose of this study was to assess the short-term clinical results of total hip arthroplasty in patients with severe acetabular protrusions secondary to rheumatoid arthritis.MethodsFrom January 2011 to November 2014, 18 patients (20 hips) with severe acetabular protrusions secondary to rheumatoid arthritis underwent total hip arthroplasties using a non-cement impaction and auto-bone-grafting method with resection of the femoral head to treat the acetabular protrusion. The Harris hip scoring system was used to evaluate hip function during follow-up; X-rays were taken to assess the extent of prosthesis loosening and bone graft healing.ResultsThe operation time ranged from 55 to 131 min, averaging 89.5 ± 8.1 min. The blood loss was 165–480 mL (295 ± 10.9 mL). No blood vessel or nerve damage and no acetabular or femoral fracture occurred. The follow-up duration was 4.5 ± 1.7 years. Postoperative X-rays revealed autologous bone graft/acetabular fusion at 4.5 months post-surgery. The Harris hip scores increased significantly, from 55.3 ± 9.5 to 92.2 ± 12.7, after the operation (P < 0.01). The distance from the center of the femoral head to Kohler’s line increased from 19.87 ± 3.9 mm to 21.5 ± 3.5 mm after the operation (P < 0.01). During follow-up, no hip acetabular prosthesis loosening was evident.ConclusionsFor patients with protrusio acetabuli secondary to rheumatoid arthritis, the use of a cementless, trabecular, metal modular cup allowing peripheral press fitting and restoration of bone stock via impacted autologous bone grafting are both technically straightforward and appear to yield satisfactory short-term results.

Total hip arthroplasty in treating acetabular protrusion secondary to rheumatoid arthritis

Objective To investigate the clinical outcomes of total hip arthroplasty in treatment of severe acetabular protrusion secondary to rheumatoid arthritis. Methods From January 2011 to November 2014, eighteen patients (20 hips) with severe acetabular protrusion secondary to rheumatoid arthritis were treated with total hip arthroplasty (THA), including 6 males (6 hips) and 12 females (14 hips). The age ranged from 37 to 68 years (average, 45.8±8.3 year). According to the classification of Sotelo-Garza and Charnley, there were 15 cases (17 hips) of type II (acetabular protrusion 6-15 mm) and 3 cases (3 hips) of type III (acetabular protrusion >15 mm). During the surgery, the femoral heads were moved out through retrograde method after the osteotomy of femoral neck by posterolateral approach. All patients underwent THA with autogenous bone graft by impacting technique for reconstruction of acetabula, and the cementless cups were planted with press-fit skills (Tantalum trabecular metal cup in 16 cases and Titanium porous coating cup in 4 cases). The hip function was evaluated by using Harris hip score. Radiographic measurement was performed with X-ray films to assess the restoration of the hip rotation center, graft incorporation and sign of prostheses loosening in follow-up duration. Results The mean operation duration and intraoperative blood loss were 89.5±8.1 min (range 55-131 min) and 295±10.9 ml (range 165-480 ml) respectively. The average amount of bone graft was 33.7±6.8 cm3 (range 32.5-61.2 cm3) in reconstruction of protrusion acetabulum. The mean follow up duration was 4.5±1.7 years (range 2.5-6.0 years). The horizontal distance between the center of femoral head and the Kohler's line was increased from preoperative 8.87±3.9 mm (range -11.11 -12.78 mm) to 23.55±2.5 mm (range 21.23-25.57 mm) postoperatively, and the vertical distance between the center of femoral head and the line joining the bilateral ischial tuberosities was decreased from preoperative 87.45±3.5 mm (range 74.75-96.97mm) to postoperative 77.83±4.1 mm (range 68.22-90.40 mm) with statistically significant difference. The bone incorporation was achieved at 6 months postoperatively in radiological film. No loosening of acetabular components was found in final fellow-up. At last follow-up, Harris hip score was significantly improved from 55.3±9.5 points preoperatively to 92.2±12.7 postoperatively (t=51.569, P=0.000). The range of flexion of the hip significantly improved from 41.5°±6.7° preoperatively to 102.3°±14.5° at finial follow-up (t=64.865, P=0.000), and the range of extension of the hip improved from 8.2°±3.5° preoperatively to 29.8°±6.6° at finial follow-up (t=51.161, P=0.000). The discrepancy was significantly decreased from 23.7±0.82 mm preoperatively to 4.7±0.39 mm postoperatively (t=19.761, P=0.000). Mild thigh pain was reported in two hips, which typically occurred only with prolonged activity without disabling and not requiring medication. Conclusion Total hip arthroplasty with impaction bone grafting and cementless modular cup can recover the acetabular center of rotation and achieve satisfactory short-term outcomes in treating patients severe protrusion acetabula secondary to rheumatoid arthritis. Key words: Arthroplasty, replacement, hip; Arthritis, rheumatoid; Acetabulum; Bone transplantation; Transplantation, autologous

Outcome of Revision Total Hip Arthroplasty in Management of Failed Metal-on-Metal Hip Arthroplasty

BackgroundThis is a retrospective review of the functional outcomes and complications of revision total hip arthroplasty (THA) of failed metal-on-metal (MoM) hip arthroplasty. MethodsA total of 20 revision THAs were performed in 19 patients. Of them, 2 cases were failed hip resurfacing, and 18 cases were failed (MoM) THA. The mean age at revision (THA) was 59.35 years (standard deviation [SD] 9.83). ResultsThe mean follow-up was 45 months (SD 13.98). The indications of revision were aseptic loosening of acetabular component without adverse local tissue reaction (ALTR; 10 hips), aseptic loosening of the acetabular and femoral components without ALTR (1 hip), painful hip associated with ALTR (6 hips), iliopsoas impingement associated with a large-diameter femoral head or malpositioned acetabular component (3 hips). The acetabular components were revised in 18 hips using Trabecular Metal Modular cups. The femoral components were revised in 3 hips. A constrained acetabular liner was used in 5 hips. The Harris hip score significantly improved from 48.4 (SD 12.98) to 83.25 (SD 10.08). There were 2 complications (1 foot drop and 1 superficial infection) and 1 failure (recurrent dislocation) that required revision to a constrained liner. ConclusionEarly results of revision THA of failed MoM hip arthroplasty showed improvement in pain and functional outcome. No case of failed bone ingrowth was noted with the use of Trabecular Metal Modular cups. Extensive soft tissue and abductor muscles dysfunctions were common. A constrained acetabular component with repair of the hip abductors might be beneficial.

Corrosion of Metal Modular Cup Liners

Numerous studies have reported on corrosion at the modular head taper, however less is known about the interface between the metal shell and liner of modular cups. This study examined the backside of a series of metal modular cup liners of two designs (DePuy Pinnacle and Smith & Nephew R3), retrieved from 67 patients. Visual inspection found evidence of corrosion in virtually all liners, with the engaging rim surface significantly more corroded than the polar regions (P<0.001). EDX confirmed that black surface deposits were chromium rich corrosion debris, while SEM analysis revealed considerable pitting in the vicinity of the black debris. The R3 liners were significantly more corroded that the Pinnacles (P<0.001); this may help to explain the higher revision rates of this design.

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.

A fatigue assessment technique for modular and pre-stressed orthopaedic implants

Orthopaedic implants experience large cyclic loads, and pre-clinical analysis is conducted to ensure they can withstand millions of loading cycles. Acetabular cup developments aim to reduce wall thickness to conserve bone, and this produces high pre-stress in modular implants. As part of an implant development process, we propose a technique for preclinical fatigue strength assessment of modular implants which accounts for this mean stress, stress concentrating features and material processing.A modular cup's stress distributions were predicted computationally, under assembly and in vivo loads, and its cyclic residual stress and stress amplitude were calculated. For verification against damage initiation in low-cycle-fatigue (LCF), the peak stress was compared to the material's yield strength. For verification against failure in high-cycle-fatigue (HCF) each element's reserve factor was calculated using the conservative Soderberg infinite life criterion.Results demonstrated the importance of accounting for mean stress. The cup was predicted to experience high cyclic mean stress with low magnitude stress amplitude: a low cyclic load ratio (Rl=0.1) produced a high cyclic stress ratio (Rs=0.80). Furthermore the locations of highest cyclic mean stress and stress amplitude did not coincide. The minimum predicted reserve factor Nf was 1.96 (HCF) and 2.08 (LCF). If mean stress were neglected or if the stress ratio were assumed to equal the load ratio, the reserve factor would be considerably lower, potentially leading to over-engineering, reducing bone conservation.Fatigue strength evaluation is only one step in a broader development process, which should involve a series of verifications with the full range of normal and traumatic physiological loading scenarios, with representative boundary conditions and a representative environment. This study presents and justifies a fatigue analysis methodology which could be applied in early stage development to a variety of modular and pre-stressed prosthesis concepts, and is particularly relevant as implant development aims to maximise modularity and bone conservation.

Survival of uncemented acetabular monoblock cups

Background and purpose Monoblock acetabular cups represent a subtype of uncemented cups with the polyethylene liner molded into a metal shell, thus eliminating—or at least minimizing—potential backside wear. We hypothesized that the use of mono​block cups could reduce the incidence of osteolysis and aseptic loosening, and thus improve survival compared to modular designs.Patients and methods We identified all 210 primary total hip arthroplasty (THA) procedures in the Swedish Hip Arthroplasty Register that used uncemented monoblock cups during the period 1999–2010. Kaplan-Meier and Cox regression analyses with adjustment for age, sex, and other variables were used to calculate survival rates and adjusted hazard ratios (HRs) of the revision risk for any reason. 1,130 modular cups, inserted during the same time period, were used as a control group.Results There was a nearly equal sex distribution in both groups. Median age at the index operation was 47 years in the monoblock group and 56 years in the control group (p < 0.001). The cumulative 5-year survival with any revision as the endpoint was 95% (95% CI: 91–98) for monoblock cups and 97% (CI: 96–98) for modular cups (p = 0.6). The adjusted HR for revision of monoblock cups compared to modular cups was 2 (CI: 0.8–6; p = 0.1). The use of 28-mm prosthesis heads rather than 22-mm heads reduced the risk of cup revision (HR = 0.2, CI: 0.1–0.5; p = 0.001).Interpretation Both cups showed good medium-term survival rates. There was no statistically significant difference in revision risk between the cup designs. Further review of the current patient population is warranted to determine the long-term durability and risk of revision of monoblock cup designs.

Modular cementless cup for total hip arthroplasty: results at 4-year follow-up

The aim is to perform the assessment of a modular cementless acetabular cup with a tapered internal design for all bearing couplings. In 190 unselected consecutive patients, 207 total hip arthroplasties were implanted. The implants were clinically and radiographically evaluated. Follow-up was 49.7 ± 8.1 months. The average Harris hip score improved from 55.5 ± 5.7 to 94.7 ± 3.4 (P < 0.05). All cups were well-positioned and stable. The Kaplan-Maier cumulative survivorship was 98.5 ± 0.8%. No significant differences have been noted in dividing patients according to the different liner materials (P < 0.005). The study, whose rationale is the novelty of this kind of implant, suggests the efficacy of the Delta-PF acetabular cup.

Pseudotumor With Dominant B-Lymphocyte Infiltration After Metal-On-Metal Total Hip Arthroplasty With a Modular Cup

We report a case of a patient who underwent metal-on-metal total hip arthroplasty with a modular cup and developed a pseudotumor 5 years postoperatively. Immunohistochemistry showed dominant B-lymphocyte infiltration in the periprosthetic tissue.

Grafting with hydroxyapatite granules for defects of acetabular bone at revision total hip replacement

The long-term results of grafting with hydroxyapatite granules for acetabular deficiency in revision total hip replacement are not well known. We have evaluated the results of revision using a modular cup with hydroxyapatite grafting for Paprosky type 2 and 3 acetabular defects at a minimum of ten years' follow-up. We retrospectively reviewed 49 acetabular revisions at a mean of 135 months (120 to 178). There was one type 2B, ten 2C, 28 3A and ten 3B hips. With loosening as the endpoint, the survival rate was 74.2% (95% confidence interval 58.3 to 90.1). Radiologically, four of the type 3A hips (14%) and six of the type 3B hips (60%) showed aseptic loosening with collapse of the hydroxyapatite layer, whereas no loosening occurred in type 2 hips. There was consolidation of the hydroxyapatite layer in 33 hips (66%). Loosening was detected in nine of 29 hips (31%) without cement and in one of 20 hips (5%) with cement (p = 0.03, Fisher's exact probability test). The linear wear and annual wear rate did not correlate with loosening. These results suggest that the long-term results of hydroxyapatite grafting with cement for type 2 and 3A hips are encouraging.

Deformation of metal-backed acetabular components and the impact of liner thickness in a cadaveric model

Shell deformation of resurfacing and all-metal modular cups following press-fit implantation has been reported, but not for conventional metal-backed cups with polyethylene liners. The deformation of acetabular components with historical and thin polyethylene inserts after press-fit insertion was evaluated using a cadaveric model. All shells and liners deformed upon implantation. Following joint loading, shell pinch decreased from 0.32 to 0.22 mm (p = 0.019) and from 0.29 to 0.13 mm (p = 0.003) for the thin and thick liner groups, respectively. Liner pinch also decreased from 0.17 to 0.04 mm (p = 0.031) and from 0.06 to 0 mm (p = 0.103) for the thin and thick liner groups, respectively. There were no significant differences between the thin and thick liners. Liner deformation was influenced by the initial shell deformation and donor bone quality. Shell and liner pinch decreased following joint loading, suggesting a settling in effect.