Recent case reports have described V40 taper failure with clinically relevant adverse reaction to metal debris (ARMD). The real incidence of V40 taper damage and potential consequences are currently unclear, however. Aim of this study is therefore, to evaluate the long-term incidence of pseudotumors in a consecutive series of THA with V40 taper and identify potential influencing factors.

From 2006 to 2007 a total number of 120 patients (127 hips) received either an uncemented (Accolade©) or cemented hip stem (ABGII©), both with V40 taper (Stryker© Mahwah, New Jersey, USA). They all were combined with 36 mm Vitallium (CoCrMo) heads and uncemented cups (Trident©) with XLPE inlays. 11,2 +/− 0,5 years post-op 82 patients with 87 hips (mean age 74 years, 58 % female) underwent clinical (PROMs) and radiographic evaluation. In 71 patients (75 hips) MARS- MRI of the hip was performed. 38 patients were lost to follow-up. In 81 patients (86 hips) chrome and cobalt levels were determined.

MRI-investigation revealed 20 pseudotumors (26%) and 18 of them had a diameter of >2cm. Patients with pseudotumors had significant higher median cobalt ion levels compared to those without (2,85 μg/l vs. 1,32 μg/l; p=0,022) and a significant correlation between pseudotumors and cobalt levels was found. Radiographic osteolysis was associated with pseudotumors as well (p= 0,014). Neither approach, BMI, gender, age, type of stem, head length, inclination nor heterotope ossification showed a significant correlation to pseudotumor occurrence.

Due to the high incidence of local ARMD in in asymptomatic patients with V40 taper and metal heads we recommend regular post-operative follow-up investigations including routine metal ion screening and consecutive MRI investigation upon elevation.

With the introduction of highly crosslinked polyethylene (HXLPE) in total hip arthroplasty (THA), orthopaedic surgeons have moved towards using larger femoral heads at the cost of thinner liners to decrease the risk of instability. Several short and mid-term studies have shown minimal liner wear with the use HXLPE liners, but the safety of using thinner HXPLE liners to maximize femoral head size remains uncertain and concerns that this may lead to premature failure exist. Our objective was to analyze the outcomes for primary THA done with HXLPE liners in patients who have a 36-mm head or larger and a cup of 52-mm or smaller, with a minimum of 10-year follow-up. Additionally, linear and volumetric wear rates of the HXLPE were evaluated in those with a minimum of seven-year follow-up. We hypothesized that there would be minimal wear and good clinical outcome. Between 2000 and 2010, we retrospectively identified 55 patients that underwent a primary THA performed in a high-volume single tertiary referral center using HXLPE liners with 36-mm or larger heads in cups with an outer diameter of or 52-mm or smaller. Patient characteristics, implant details including liner thickness, death, complications, and all cause revisions were recorded. Patients that had a minimum radiographic follow-up of seven years were assessed radiographically for linear and volumetric wear. Wear was calculated using ROMAN, a validated open-source software by two independent researchers on anteroposterior X-rays of the pelvis. A total of 55 patients were identified and included, with a mean age of 74.8 (range 38.67 - 95.9) years and a mean BMI of 28.98 (range 18.87 - 63-68). Fifty-one (94.4%) of patients were female. Twenty-six (47.7%) patients died during the follow-up period. Three patients were revised, none for liner wear, fracture or dissociation. Twenty-two patients had a radiographic follow-up of minimum seven years (mean 9.9 years, min-max 7.5 –13.7) and were included in the long-term radiographic analysis. Liner thickness was 5.5 mm at 45 degrees in all cases but one, who had a liner thickness of 4.7mm, and all patients had a cobalt-chrome head. Cup sizes were 52mm (n=15, 68%) and 50mm (n=7, 32%). Mean linear liner wear was 0.0470 mm/year (range 0 - 0.2628 mm) and mean volumetric wear was 127.69 mm3/year (range 0 - 721.23 mm3/year). Using HXLPE liners with 36-mm heads or bigger in 52-mm cups or smaller is safe, with low rates of linear and volumetric wear in the mid to long-term follow-up. Patients did not require revision surgery for liner complications, including liner fracture, dissociation, or wear. Our results suggest that the advantages of using larger heads should outweigh the potential risks of using thin HXLPE liners

Ceramic heads and highly cross-linked polyethylene (HXLPE) as bearing surface materials have been introduced to reduce the production of polyethylene wear particles. The present study hypothesized that the wear rate of HXLPE could be further reduced when combined with a ceramic head. The purpose of this study was to compare the in vivo wear of Longevity HXLPE against cobalt-chromium and zirconia heads after a minimum 5-year follow-up. A prospective cohort study was performed in 102 cementless total hip arthroplasties (THAs) with the Longevity HXLPE socket (Zimmer) between June 2000 and October 2001. Same prostheses were used in all cases both acetabular cups (Trilogy; Zimmer) and femoral stems (Versys Fiber Metal Taper; Zimmer). 26-mm zirconia heads (NGK) or 26-mm cobalt-chromium heads (Zimmer) were randomly used in 51 hips each. A minimum 5-year follow-up was completed for 47 hips with zirconia heads and 46 hips with cobalt-chromium heads. Two-dimensional linear wear of Longevity HXLPE was measured using computer-assisted methods (PolyWare) on annual x-rays, and total head penetration rates and steady state wear rates were calculated. In addition, periprosthetic osteolysis was evaluated. At a mean 6-year follow-up, the total head penetration rates were 0.034±0.016 mm/year (zirconia) and 0.031±0.015 mm/year (cobalt-chromium). The steady state wear rates were −0.01 mm/year (zirconia) and −0.01 mm/year (cobalt-chromium). No significant difference was seen between the two groups (p=0.4 and p=0.91). Osteolysis was not observed around prostheses in any hips. In conclusion, no advantage was seen for the zirconia head compared with the cobalt-chromium head in this time period

Using a larger diameter femoral head in total hip arthroplasty (THA) has advantages in terms of the increased joint stability and range of motion. And the wear resistance of highly cross-linked polyethylene (HXLPE) even combined with a larger head has already been demonstrated by in vitro studies. The purpose of this study was to compare the in vivo wear of Longevity HXLPE sockets against 32 mm and 26 mm heads at a 5-year follow-up. From November 2000 to November 2001, 51 primary cementless THAs were performed with a 26 mm cobalt-chromium head and a Longevity HXLPE socket (Zimmer). A cohort of 32 mm cobalt-chromium heads was comprised of 51 THAs with the same prosthesis performed from December 2001 to December 2003. No significant differences between the groups were observed in gender, age, and BMI, however, polyethylene liners with 32 mm heads were significantly thinner than those with 26 mm heads. Two-dimensional linear wear was measured using PolyWare software on annual x-rays, and total head penetration rates at postoperative 5-year and steady state wear rates were calculated. In addition, periprosthetic osteolysis was evaluated. At the 5-year follow-up, the total head penetration rates were 0.047±0.022 mm/year with 26 mm heads and 0.048±0.026 mm/year with 32 mm heads. The steady state wear rates were −0.008 mm/year with 26 mm heads and 0.001 mm/year with 32 mm heads. No significant differences were seen between the two groups (p=0.82 and p=0.24). Osteolysis was not observed around pros-theses in any hips. At the 5-year follow-up, the wear rate of Longevity HXLPE was very low. A Longevity HXLPE socket will undergo the same level of wear whether with a 32 mm head or a 26 mm head

Introduction: Increased wear is associated with aseptic loosening and late dislocations. Hard on hard bearings may reduce wear but still have topics of concern such as free metal ions in metal on metal bearings and the risk for fracture in ceramic articulations. Ceramic heads against conventional polyethylene is also used with the intention to reduce wear. But this effect has not been conclusively documented in the literature and is still discussed. 87 patients were operated consecutively by the same surgeon with the same surgical technique. All patients received a cemented all poly cup sterilized with irradiation in inert atmosphere and a cemented stem. Head size was 28 mm in all patients. 40 patients received cobalt-chrome heads and 47 patients aluminiumoxid heads. The patients were followed with RSA for 10 years and analysed for wear. Results: Mean (SEM) wear for the group with cobalt chrome heads was 0.93 mm (0.13) and for the group with aluminiumoxide was 0.43 mm (0.08) (p = 0.001). Discussion: We found significantly less wear with aluminumoxide heads compared to cobalt-chrome heads. The wear results in the cobalt-chrome group correlate well to wear values in the literature for conventional polyethylene. Although the polyethylene in this study is partly cross-linked (3Mrad) it is not clear whether these results can be extrapolated directly to the use of highly cross-linked PE. If longer follow-ups confirm the mechanical stability of highly cross-linked PE, ceramic heads might contribute additionally to the reduction of wear. In conclusion we found significantly reduced wear for aluminumoxide heads compared to cobalt chrome heads which could be beneficial for young and active patients

Thirty total hip replacements in twenty-eight patients in which a Zirconia/Polyethylene articulation was utilized were compared to a control group undergoing total hip replacement utilizing Cobalt-Chrome/Polyethylene articulation. These patients were matched for gender, BMI and pre-operative diagnosis. At nine years after implantation there was no difference in the functional outcome between the two groups and no difference in liner wear rate on x-ray (Livermore technique). There was a 27% revision rate in the Zirconia group compared to the 11.5% revision rate in the Cobalt-Chrome group. Bearing surfaces require long- term clinical follow-up to validate in vitro performance. To determine the benefit of Zirconia on polyethylene versus cobalt-chrome on polyethylene in total hip articulation. Zirconia offers no advantage over a cobalt-chrome head in decreasing in vivo polyethylene wear at ten- year follow-up. Newer bearing surfaces require long- term clinical follow-up to validate in vitro laboratory performance. All primary total hip replacements at this institution are entered prospectively in a database and are assessed on an annual basis. All patients in this study were followed for a mean of nine years with a range of six to thirteen years. Thirty cementless total hip arthroplasties were performed in twenty-eight patients utilizing a Zirconia head coupled with a polyethylene acetabular component. Twenty-six hips have been followed for a mean of nine years. These were matched to a control group of twenty-six hips in twenty-six patients utilizing a cobalt-chrome head coupled with an identical polyethylene liner followed for a mean of ten years (range five to fourteen years). There was no functional difference in outcome at nine years between the two groups utilizing the Livermore technique there was no difference in the liner wear rate between the two patient groups. However, seven hips (27%) of the Zirconia group required revision due to loosening and/or extensive osteolysis around the cup and only three hips (11.5%) required revision in the cobalt-chrome group. Our study demonstrates that although changes in component designs and materials may offer theoretical advantages over current components their effect in vivo remains questionable

Trunnionosis in modular hip arthroplasty has recently been recognised to be clinically important. Gaining an understanding of how the material interface at the head-trunnion affects the tribology at the modular junctions has current clinical implications as well as an implication on future implant selection and material choice. This matched-cohort study aims to compare tribocorrosion between ceramic and cobalt-chromium trunnions and to investigate other factors that contribute to the difference in tribocorrosion if present. All hip prostheses retrieved between 1999 and 2015 at one centre were reviewed. Fifty two ceramic heads were retrieved, and these were matched to a cobalt-chromium cohort according to taper design, head size, neck length and implantation time in that order. The two cohorts were similar in male:female ratio (p=0.32) and body mass index (p=0.15) though the ceramic group was younger than the cobalt-chromium group (56.6 (+/−)13.5 years for ceramic group vs 66.3 (+/−14.4) years for cobalt-chromium group; p=0.001). There was no significant difference in the reasons for revision between the two groups (p=0.42). The femoral head trunnions were examined by two independent observers using a previously published 4-point scoring technique. The trunnions were divided into three zones: apex, middle and base. The observers were blinded to clinical and manufacturing data where possible. Ceramic head trunnions demonstrated a lower median fretting and corrosion score at the base zone (p<0.001), middle zone (p<0.001) and in the combined score (p<0.001). In a subgroup analysis by head size, ceramic heads had a lower fretting and corrosion score at 28mm head diameter (p<0.001). Within the ceramic group, taper design had a significant effect on fretting and corrosion in the apex zone (p=0.04). Taper design also had a similar effect in the cobalt-chromium group in the apex zone (p=0.03). For the ceramic trunnions, the largest effect was contributed by the difference between the 11/13 taper and the 12/14 taper. For the cobalt-chromium trunnions, the largest effect was contributed by the difference between the 5 degree 38′ 37″ taper and type 1 taper. Ceramic head trunnions showed a significantly lower fretting and corrosion score as compared to cobalt-chromium trunnions. Ceramic heads had a lower score than cobalt-chromium heads at 28mm head diameter. Taper design had an effect on fretting and corrosion within each cohort

Introduction. The Metasul articulation was introduced in the early 1990's. It comprises a 28mm forged, cobalt-chrome head and a forged metal inlay, set into the polyethylene element of the acetabular component. During the 1990's and early 2000's anatomic sized MoM articulations were re-introduced for hip resurfacing and stemmed implant designs. Adverse tissue reactions to metal debris and corrosion products subsequently led to a decline in MoM usage. Materials & Methods. Between January 1995 and December 1998, 133 hips underwent primary THR using the Metasul 28mm bearing. Patients were routinely sent an annual postal Oxford Hip Score (OHS) and radiographs were obtained from the second post-operative year. We have retrospectively reviewed the clinical and radiographic dataset following the 15 year follow-up time point. Results. At a mean follow-up of 16.6 years (range 15.5–19.2 years), the median OHS score at 15 years was 42 (range 7–48). OHS showed statistically significant improvements at all post-operative time points when compared to pre-operative scores (p= <0.001; CI 4.42–6.69). No significant decline in OHS score was observed following the 15 year follow-up. Nine hips were revised at a mean duration of 6.11 years (range 1.09–17.49). Worst case scenario Kaplan-Meier analysis, when lost patients were presumed revised, demonstrated an 84% (CI 0.77–0.90) survivorship at 15 years when revision for any cause was the endpoint. Aseptic loosening as the end point demonstrated an 88% survivorship (CI 0.81–0.93). One hip demonstrated femoral component migration of 2.7mm's but no component loosening's were observed. Discussion. In contrast to the problems reported for other MoM articulations, our study suggests that the 28mm diameter Metasul bearing provides good survivorship and outcome at a minimum of 15 years. No long-term joint stability issues were identified. We have not assessed serum metal ion levels or quantified metal debris generation. Our patients remain under surveillance

Introduction. Manifestation of high interface stresses coupled with micromotion at the interface can render the taper lock joint in a modular hip replacement prosthesis at risk for failure. Bending can lead to crevice formation between the trunnion and the head and can potentially expose the interface to the biological fluids, generating interface corrosion. Additionally, development of high stresses can cause the material to yield, ultimately leading to irreversible damage to the implant. The objective of this study is to elucidate the mechanical response of taper junction in different material combination assemblies, under the maximum loads applied during everyday activities. Methods. Computer simulations were executed using a verified FE model. A stable hexahedral mesh (33648 elements) was generated for the trunnion (taper size: 12/14mm) and a tetrahedral mesh (51182 elements) for the head (CoCr, size: 32mm). An assembly load of 4000N was applied along the trunnion axis followed by the application of a load of 230–4300N at 25° and 10° angle to the trunnion axis in the frontal and sagittal planes. A linear static solution was set up using Siemens NX Nastran. Two material combinations were tested - cobalt-chrome head with a titanium alloy trunnion and cobalt chrome head with a cobalt-chrome trunnion. Results. Table1 compares the results obtained from the simulation to those observed in experimental simulations performed under similar loading conditions in our lab. Larger vertical interface displacement was observed in the CoCr-CoCr assembly during toggle-inducing loads. The trunnion bending inside the femoral head was higher in the Ti-CoCr assembly (0.056) compared to the CoCr-CoCr assembly (0.027) with the overall bending of the Ti-CoCr assembly also observed to be much higher (Fig.1). Negligible difference between the stress measured in the femoral head and taper was observed (Fig.2). Discussion. Bending could potentially lead to the development of higher stresses especially under multiple cycles of loading. Fatigue and plastic deformation could result in irreparable damage to the interface leading to implant failure. Additionally, bending causes a separation of the interfaces at the trunnion-head junction, leading to crevice formation, triggering corrosion by exposure to the surrounding physiological environment. Thus, it is crucial that we understand the mechanics of the trunnion-head junction especially under conditions of functional loading

Introduction. Detailed analysis of retrieved total hip replacements (THRs) is valuable for assessing implant and material successes and failures. Reduction of bearing wear and corrosion and fretting of the head-neck trunnion is essential to implant durability and patient health. This research quantifies and characterizes taper and bearing surface damage on retrieved oxidized zirconium THRs. Methods. Initially, 11 retrieved oxidized zirconium femoral heads were examined along with their associated femoral stems. Relevant patient and retrieval data was collected from clinical charts and radiographs. Taper corrosion (Figure 1) and fretting damage (Figure 2) scoring was performed following the Dyrkacz [1] method. A coordinate measuring machine was used to obtain a detailed surface map of the male and female taper surfaces. Taper surface maps were best-fit with an idealized cone followed by volume subtraction to quantify the amount of material removed as a result of fretting and corrosion processes. Scanning electron microscopy was performed on select samples to identify specific damage modes. Unique surface bumps were noted on the articular surface of select femoral heads (Figure 3). Seventeen femoral heads were added to the analysis specifically for identification of these bumps. Articular surfaces were searched under SEM magnification and bumps were identified and counted. Parametric statistical correlations were performed with SAS v9.3. Results. Mean patient age was 61 years (Range: 35–95) with mean implantation period being 2.0 years (Range: 0.1–11.4) and mean body mass index of 29 kg/m. 2. (Range: 22–46). Revision for infection (n=11), peri-prosthetic fracture (n=5) and dislocation (n=5) were the main reasons for revision. Mean corrosion damage scores were 2.0 and 3.6 (head, neck) while mean fretting damage scores were 8.5 and 5.8 (head, neck). Fretting damage score was weakly correlated with implantation period (p=0.07) while corrosion damage score was not. Mean corrosion and fretting volume measured 0.40 mm. 3. and 0.87 mm. 3. (head, neck). Volume of corrosion and fretting damage did not correlate with implantation period; however neck volume correlated with inclination angle of the acetabular cup (p<0.01). Bearing diameter was not found to correlate with corrosion and fretting damage score or volume. The unique surface bumps were identified in 12 of 28 samples, with 3 samples having <10 bumps. Presence of these bumps did not appear to be related to bearing diameter, implantation period, or any damage metrics. Conclusion. Fretting damage was found to correlate with implantation period, suggesting that is a continuous in vivo process; however, this was not found for corrosion damage. Fretting damage volume correlated with acetabular cup angle; however, this may be coincidence as only 8 samples were included in the analysis. Overall, our corrosion damage scores (2.0–3.6) were lower than previously published values for 28mm & 36mm cobalt-chrome heads (4.5–13.1) [1]. However, our fretting damage scores (5.8–8.5) were higher than previously published (2.8–4.4) [1]. Greater fretting damage on the oxidized zirconium heads may be explained by the softer zirconium alloy compared to that of cobalt-chromium. Further subsurface investigation of the surface bumps is underway using a focused ion beam mill

Aims

The aim of this study was to evaluate the suitability of the tapered cone stem in total hip arthroplasty (THA) in patients with excessive femoral anteversion and after femoral osteotomy.

Introduction: The bearing surface of total hip arthroplasty (THA) is a key factor in implant survivorship. Ceramic bearings have enhanced wear properties though are prone to fracture and thus Oxinium has been developed as an alternative. The aim of our study was to compare the its wear properties against cobalt-chrome which is currently the most widely used femoral head bearing surface in THA. Methods: We prospectively randomized 270 consecutive patients undergoing THA at one institution into three groups: Groups I, II and III. Group I received a cobalt-chrome femoral head and cross-linked poly-ethylene (XLPE) liner; Group II received an oxinium femoral head and ultrahigh molecular weight polyeth-ylene (UHMWPE) liner; Group III received an oxinium femoral head and cross-linked polyethylene liner. 32 mm heads were used in all the cases. Patients were longitidunally followed up with clinical evaluation and standardised radiographs of the pelvis and hip. Using DICOMeasure software, we calculated the linear and volumetric wear rate for each group to determine if a difference existed. Results: The demographics and comorbid conditions were similar between the groups. The survivorship of all components was 100% in all groups at 2 years. No patients were lost to follow-up. After the first 6 months of creep, the rate of linear wear over 2 years was 0.16mm for Group I, 0.10mm for Group II, and 0.06mm for Group III. ANOVA testing demonstrates statistical significance between the groups (P < 0.05). Discussion and Conclusion: Our results demonstrate that the wear rate using 32mm Oxinium heads is significantly lower than that for cobalt-chrome heads and this effect is dramatically enhanced when used in combination with highly cross linked polyethylene

Bone preserving hip arthroplasty devices are appealingfor use in young patients because their high-demand activities and extended lifetimes makes the prospect of multiple revisions a reality. Therefore prostheses which ensure a straightforward revision with a low complication rate and good clinical outcome are favourable for young and active patients. Modern hip resurfacing serves these conditions and shows very good mid-term and now longer term (10 and 13 years) results especially in osteoarthritis. With other diagnoses like avascular necrosis, deformities of the femoral head in m. Perthes or slipped femoral epiphysis (SUFE), or in large bone cysts and erosive arthritis the bone stock of the femoral head gives insufficient support to the femoral component. In these conditions the alternative to a resurfacing procedure had been a stemmed total hip arthroplasty (THA). The Birmingham Mid Head Resection device (BMHR; Smith&Nephew Orthopaedics) is an alternative to resurfacing and to a stemmed THA. The BMHR device consists of an uncemented short stem made of titanium alloy and a large diameter cobalt-chrome head. The stem does not enter the femoral canal thus facilitating future revisions. The metal-on-metal bearing is the same as in resurfacing. The instrumentation allows switching from a planned BHR to the BMHR. The BMHR uses the unique anatomy of the head neck junction to prepare internally a cone that matches the frustoconical section of the BMHR stem. Thus a cement free press fit can be achieved. This maintains anatomical load transmission and avoids osteopenia of the proximal fenur. Since 2006 we have performed 662 BMHR implantations. The indications were osteoarthritis in about 70%, dysplasia in 20%, AVN 5,5%, posttraumatic OA in 3%, SUFE and m. Perthes in 1%. Complications occured in 3,2%. Fractures of the femoral neck occured in 8 patients, 4 of them caused by technical errors in the beginning, 3 because of higher risk indication. All revisions were performed successfully and the cup was retained. Low grade infections in 2 cases with one stage revision and 3 unstable cups needed to be reinserted. All revisions were successful. One early dislocation was treated by closed reduction, another remained unstable and was treated by THA. In conclusion we continue to use the BMHR to bridge the gap between resurfacing and stemmed THA because the complications we experienced are not inevitable and had become very rare with our growing experience

Summary. The required torque leading to an abrasion of the passive layer in the stem-head interface positively correlates to the assembly force. In order to limit the risk of fretting and corrosion a strong hammer blow seems to be necessary. Introduction. Modular hip prostheses are commonly used in orthopaedic surgery and offer a taper connection between stem and ball head. Taper connections are exposed to high bending loads and bear the risk of fretting and corrosion, as observed in clinical applications. This is particularly a problem for large diameter metal bearings as the negative effects may be enhanced due to the higher moments within the taper connection. Currently, it is not known how much torque is required to initiate a removal of the passive layer, which might lead to corrosion over a longer period and limits the lifetime of prostheses. Therefore, the purpose of this study was to identify the amount of torque required to start an abrasion of the passive layer within the interface dependent on the assembly force and the axial load. Materials and Methods. Titanium hip stems (Furlong H-AC, JRI, UK) and cobalt-chromium heads (⊘ 28mm, size L, JRI, UK) were assembled using a drop rig with peak forces of 4.5 kN (F. P,1. , n = 4) or 6.0 kN (F. P,2. , n = 4). The prostheses were inverted and then mounted with the head rigidly fixed to the base of a materials testing machine using a non-conducting (nylon) jig while submerged in Ringer's solution. The stems were attached to the machine actuator via non-conductive plates. An axial load (F. A,1. = 1 kN, F. A,2. = 3 kN, n = 4 each) was applied to the stems along the taper axis. After a period of equilibration a torque, increasing from 0 up to 15Nm, was manually applied. The galvanic potential at the taper interface was continuously recorded using a titanium electrode. The torque required to cause a drop in the potential of 5% was identified. For statistical analyses non-parametric tests were performed (α = 0.05). Results. Four different phases of the potential could be clearly differentiated during testing: equilibrium, removal of the passive layer leading to a drop of the potential, repassivation and then a second equilibrium. Prostheses assembled with a force of 6 kN required a significantly higher torque to start a removal of the passive layer compared to those with 4.5 kN (7.2 ± 0.5 Nm vs. 3.9 ± 1.0 Nm for F. A,1. , p = 0.029). In contrast, no influence of the axial load on the fretting behaviour of the prostheses could be found (8.0 ± 1.6 Nm for F. P,2. , p = 0.486). Discussion. Changes in the galvanic potential were observed at low torque levels for a small head diameter. With increasing head diameter the tangential force leading to a removal of the passive layer in the stem-head interface decrease resulting in a higher risk for corrosion. Component assembly with a high force reduces the risk of fretting and corrosion in the taper interface; however, it is feasible that the determined torque levels can still be reached, particularly in situations of large weight and high activity of the patient or malpositioning of the prosthesis in the body

Polyethylene (PE) wear affects survivorship in the long term while dislocation remains a significant factor in the short term. Increasing head size can reduce impingement and dislocation. However, this increases wear rates and reduces the net thickness of the liner. Several reports have demonstrated significant reduction in wear in cross-linked PE. This study reports wear rates in crosslinked PE liners with increased head size. Four groups of PE liners were tested against cobalt-chrome heads in a hip wear simulator: highly crosslinked liners with head size 28mm (28XPE) and 32mm (32XPE), and minimally crosslinked liners with head size 28mm (28PE) and 32mm (32PE). Additional liners were used as load-soak controls to monitor weight gain due to fluid absorption. Gravimetric analysis was performed every 500,000 cycles for a total of 5,000,000 cycles. 28PE and 32PE liners had mean wear rates of 12.5(±1.0) and 17.45 (±2.6) mg/million cycles. Both highly crosslinked PE liners (28XPE and 32XPE) had significant less wear rates that regular polyethylene 1.49 (±0.72) and 2.55 (±0.19) mg/million cycles respectively. Increasing head size resulted in increased wear, which is consistent with previous reports. Highly crosslinked PE significantly reduced wear rates in both head sizes. Although there was a small increase in wear in the 32XPE group compared to the 28XPE group, wear was significantly less than both 32PE and 28PE groups. These encouraging results suggest that a dual benefit (reduced wear and reduced dislocation rate) might be achieved using 32XPE liners. Further studies that evaluate fatigue damage, crack propagation and impingement are necessary

Introduction: The annual wear rate in polyethylene articulations should be 0.1 mm or less to avoid future osteolysis. Highly Crosslinked polyethylene demonstrates 80–90% wear reduction in hip simulator testing, but the clinical documentation of this new polyethylene is still inadequate. We evaluated the highly crosslink PE in two prospective randomised clinical studies. Patients and Methods: Thirty two patients (12 male, 20 female, 64 hips) with a median age of 48 years (range, 29–70 years) with bilateral primary or secondary arthrosis of the hip received hybrid THA. With liners made of highly cross-link on one side and conventional PE on the other one. Twenty-seven patients in this study have passed 2 years follow up. Further Sixty patients (61 hips) with a median age of 55 years (range, 35–70 years) were randomized to receive either highly crosslink or conventional cemented all PE of the same design. Forty-nine patients have been followed for 3 years. In both studies all patients received Spectron stems with 28mm cobalt-chromium head. Radiostereometric examinations with the patient supine or standing were done at regular intervals. Wear was measured in the supine position from the postoperative week, whereas standing examinations were initiated three months after the operation. Results: The penetration rate was almost identical in the study and control groups in 6 months after the operation. Thereafter the penetration rate levelled out in the 2 groups with highly crosslink PE. At two years the highly crosslink PE liner showed 62% lower proximal penetration and 31% lower total (three-dimensional) penetration when the patients were examined in supine position. The highly crosslink all PE cemented cups showed significantly lower proximal penetration in both position. Discussion: The better wear performance of highly crosslink PE could increase the implant longevity. Longer follow up is needed to evaluate if this new material is associated with less occurrence of osteolysis

Background: Cemented and cementless fixations of acetabular components in total hip arthroplasty are routine practice with inherent advantages and disadvantages. The aim of our prospective randomized study was to compare the clinical and radiographic results of cementless porous-coated cobalt chromium acetabular component with cemented all-polyethylene acetabular component in total hip arthroplasty. Methods: Three hundred patients were randomized to receive a cementless hemispherical cobalt chromium porous-coated no-hole acetabular component (group 1) or cemented all-polyethylene acetabular component (group 2) with an identical cemented femoral stem and 28mm cobalt-chromium head. Patients were evaluated clinically with Harris Hip Scores (HHS) and radiographically. Analysis of both intention-to-treat groups was performed. Results: Group 1 had 128 patients (55 male, 73 female) with average age of 70.3 years. Group 2 had 147 patients (63 male, 84 female) with average age of 71.2 years. Average follow-up was 9.5 years (1.03–13.23). The median follow-up was 10 years. 25 patients were excluded from analysis for reasons including unfit for surgery (2), operation cancelled (2), missing data (8) and non-study device (10). Average preoperative HHS improved from 34.4 and 34.5 to 80 and 82.5 postoperatively in group 1 and 2 respectively. There was no statistically significant difference between the average HHS of the two groups (p=0.449) at last follow-up. There were 7 revisions in group 1 [infection (2), cup migration (2), aseptic loosening (1), slipped cup (1) and fractured liner (1)]. 11 patients had revision in group 2 [aseptic loosening (8) and recurrent dislocations (3)]. Revision rate between the two groups was not statistically significant (p=0.465). 10-year survivorship was 93.8%; and 86.6%; for group 1 and 2 respectively. No statistically significant difference was noted for prognostic factors like gender (p=0.006), body mass index (p=0.433), age (p=0.657) and surgical approach (p=0.004) for the two groups. Prognostic factors like gender (male, p=0.006) and surgical approach (posterior, p=0.004) were noted to be significant but body mass index (p=0.433) and age (p=0.657) had no statistical significance. Bootstrapping analysis for the two groups (p-value calculations N=3000) showed a significant p-value for 19 and not significant p-value for 2981 calculations. 4 porous coated cups and 29 all-polyethylene cups had radiolucencies. None of the porous-coated cups had expansile osteolysis. Conclusions: The results from our study indicate that patients with a cemented all-polyethylene cup and cementless porous coated cup have similar long term outcomes. In patients over 75 years cemented cups have excellent results (100% survivorship at 10 years)

Introduction: In a pioneer study Oonishi et al (1988) found reduced socket wear with the use of polyethylene subjected to high radiation doses. This observation has stimulated the development of a new generation polyethylene. In addition to high radiation doses the plastic is also subjected to various types of heat treatment to reduce the amount of free radicals. The purpose of the present study is to evaluate one of the new highly cross-linked polyethylenes in a randomized controlled study of cemented THA. The hypothesis is that the improved wear resistance will reduce the prevalence of osteolytic lesions with long-term follow-up. Methods and materials: Patients in clinical and radiographic need of a THR with non-inflammatory osteoarthritis of the hip were randomized in two groups. Group 1 received a cemented Weber cup (Sulzer®, Switzerland) made of highly cross-linked (WIAM) polyethylene, group 2 got a conventional cup. All patients received a cemented Spectron (Smith & Nephew, USA) with a 28mm cobalt-chromium head. So far 15 patients, (6 male and 9 females) with a median age of 55 years (range 42–62) have been evaluated in group 1 and 14 (9 male and 5 females) with a median age of 55 years (range 45–70) in group 2. The penetration of the femoral heads has so far been measured postoperatively (all hips supine), after 3 month (17 hips supine and standing) and after 6 month (11 hips supine and standing) using radiostereometry. Results: The median proximal and three-dimensional (3-D) penetration (total wear) 0–6 month (supine position) was almost equal in the two groups. Group 1 had a proximal penetration of 0.08 mm (range 0.00–0.17) and a total penetration of 0.11 mm (range 0.06–0.14). The corresponding values for group 2 were 0,10 mm (0.05–0.21) for proximal penetration and 0.13 mm (0.10–0.16) for total penetration. Between 3 and 6 month the penetration (median values) was 0.04 mm/0.10 mm (proximal/3-D) for group 1 and 0.07 mm/0.12 mm for group 2. With the patients standing we found a proximally migration of the socket (0–6 month) in group 1 of 0,08 mm (−0.07 – 0.21) and 0.12 mm (0.1–0.13) in group 2. Discussion: Use of a highly cross-linked polyethylene in the socket did not influence the early penetration rate after THR. Early creep of the material is possible explanation. 1-year follow-up on approximately 50% of the patients will be presented at the meeting

Aims

The optimum clearance between the bearing surfaces of hip arthroplasties is unknown. Theoretically, to minimize wear, it is understood that clearances must be low enough to maintain optimal contact pressure and fluid film lubrication, while being large enough to allow lubricant recovery and reduce contact patch size. This study aimed to identify the relationship between diametrical clearance and volumetric wear, through the analysis of retrieved components.

Aims

To investigate the effect of polyethylene manufacturing characteristics and irradiation dose on the survival of cemented and reverse hybrid total hip arthroplasties (THAs).