The number one reason to consider large heads in total hip arthroplasty (THA) is for increased stability. Large diameter femoral heads substantially increase stability by virtue of increased range of motion and increased jump distance, which is the amount of displacement required to sublux the head out of the socket. Prevention is the best means for reducing dislocation, with requisites for stability being appropriate component position, restoration of leg length, and restoration of offset. In a review from our center studying the frequency of dislocation with small diameter femoral heads (≤32 mm) in 1262 patients (1518 hips) who underwent primary THA performed via a direct lateral approach, we observed a dislocation rate of 0.8% (12 of 1518). In a subsequent study of 1748 patients (2020 hips) who underwent primary THA at our center with large diameter heads (mean 43 mm, range 36–60 mm), we observed a substantially lower 0.04% frequency of dislocation (one of 2010) at a mean followup of 2.6 years. Our findings have been echoed in studies from several other centers. Howie et al. reported a prospective controlled trial of 644 low risk patients undergoing primary or revision THA randomised to receive either a 36 mm or 28 mm metal head articulated on highly crosslinked polyethylene. They observed significantly lower frequency of frequency of dislocation with 36 mm heads both overall (1.3%, 4 of 299 versus 5.4%, 17 of 216 with 28 mm heads, p=0.012) and in primary use (0.8%, 2 of 258 versus 4.4%, 12 of 275 with 28 mm heads, p=0.024), and a similar trend in their smaller groups of revision patients (5%, 2 of 41 versus 12%, 5 of 41 with 28 mm heads, p=0.273). Lachiewicz and Soileau reported on early and late dislocation with 36- and 40 mm heads in 112 patients (122 hips) at presumed high risk for dislocation who underwent primary THA. Risk factors were age >75 for 80 hips, proximal femur fracture for 18, history of contralateral dislocation for 2, history of alcohol abuse in 2, large acetabulum (>60 mm) in 6, and other reasons in 14. Early dislocation (<1 year) occurred in 4% (5 of 122), all with 36 mm heads. Late dislocation (>5 years) did not occur in any of the 74 patients with follow up beyond 5 years. Stroh et al. compared 225 patients (248 hips) treated with THA using small diameter heads (<36 mm) to 501 patients (559 hips) treated with THA using large diameter heads (≥36 mm). There were no dislocations with large diameter heads compared with 1.8% (10 of 559) with small diameter heads. Allen et al. studied whether or not large femoral heads improve functional outcome after primary THA via the posterior approach in 726 patients. There were 399 done with small heads (<36 mm), 254 with medium heads (36 mm), and 73 with large heads (>36 mm), analyzed preoperatively, at 6 months, and at 12 months. The authors could not find a correlation between increasing head size and improved function at one year, but observed that dislocation was reduced with large diameter heads. Optimization of hip biomechanics via proper surgical technique, component position, and restoration of leg length and offset are mandatory in total hip arthroplasty. Large heads enhance stability by increasing range of motion prior to impingement and enhancing jump stability

Introduction & aims. Total hip replacement is an excellent treatment option for people with late stage degenerative hip disease. In addition to marked reduction in pain and improvement in sleep, most people regain range of motion, physical ability and quality of life. This study aimed at the functional outcomes of large diameter heads in THR patients. Method. This study is an analysis of a cohort of patients undergoing total hip replacement performed at our hospital from November 2011 to July 2013. A total of 70 hips, 40 males and 30 females, were operated upon with large diameter femoral heads. The mean age was 50.38 years (range 40–59 years). In our cohort, 32 patients had AVN of femur head, 19 had post traumatic secondary degeneration, 10 had RA, 6 had AS and 3 patients had OA of hip. The follow-up data included local complications, Harris Hip Score, medical complications, readmission, activity status and use of a walking aid. Results. Harris hip score at final follow up was, 33 cases had excellent, 26 cases had good result. None of the patient had fair or poor result. Two cases of superficial infection were observed. One case of dislocation was observed in post operative period which was reduced under GA and patient was given abduction brace. The mean follow up was 16.31 months ranging from 6 to 32 months. During the follow up, we had mortality of two patients. One died at 14 months due to myocardial infarction and the cause of other died due to CVA at 10 months follow up. Conclusions. Lower dislocation rate and better range of motion in majority of cases reinforces the advantage of large diameter head in THR in young and active patients. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction:. Large diameter femoral heads have been used successfully to prevent dislocation after Total Hip Arthroplasty (THA). However, recent studies show that the peripheral region of contemporary femoral heads can directly impinge against the native soft-tissues, particularly the iliopsoas, leading to activity limiting anterior hip pain. This is because the spherical articular surface of contemporary prosthesis overhangs beyond that of the native anatomy (Fig. 1). The goal of this research was to develop an anatomically shaped, soft-tissue friendly large diameter femoral head that retains the benefits of contemporary implants. Methods:. Various Anatomically Contoured femoral Head (ACH) designs were constructed, wherein the articular surface extending from the pole to a theta (θ) angle, matched that of contemporary implants (Fig. 2). However, the articular surface in the peripheral region was moved inward towards the femoral head center, thereby reducing material that could impinge on the soft-tissues (Fig. 1 and Fig. 2). Finite element analysis was used to determine the femoroacetabular contact area under peak in vivo loads during different activities. Dynamic simulations were used to determine jump distance prior to posterior dislocation under different dislocation modes. Published data was used to compare the implant articular geometry to native anatomy (Fig. 3). These analyses were used to optimize the soft-tissue relief, while retaining the load bearing contact area, and the dislocation resistance of conventional implants. Results:. The resulting ACH prosthesis retained the large diameter profile of contemporary implants over an approximately hemispherical portion (Fig. 2). Beyond this, the peripheral articular surface was composed of smaller convex radii. With this design, the jump distance under posterior and anterior dislocation modes, and the femoroacetabular contact area under loads corresponding to walking, deep knee bend and chair sit, remained identical to that of contemporary implants. Additionally, while contemporary prosthesis extended beyond the native articular surface in the distal-medial and proximal-lateral regions (shaded grey), the ACH implant remained within the margins of the native anatomy (Fig. 3). Conclusion:. A novel large diameter anatomically contoured femoral head prosthesis was developed, to mitigate the soft-tissue impingement with contemporary prosthesis. The ACH retained the large diameter profile of contemporary implants over a hemispherical portion. However, in the peripheral region, the ACH had a smaller profile to reduce soft-tissue impingement

INTRODUCTION. The risk of dislocation in large diameter metal on metal hip replacement is significantly lower than in standard THR. This is due to the increased primary arc, increased jump distance and possibly a suction effect. Our unit has performed over 1500 of these cases with an overall revision rate of <1%. We report a case series of dislocations in 5 large diameter metal on metal hips undertaken at our unit. METHOD. All cases were reduced closed and investigated for cause of dislocation. Radiological investigation included plain film radiographs and CT to exclude component mal-position and MRI to document soft tissue deficiency. Metal ion levels were measured and microbiological investigation was undertaken. RESULTS. In all cases component positioning was acceptable. Metal ion levels were significantly elevated with levels comparable to published work. MRI showed significant soft tissue defects in all patients. At revision all were found to have necrotic areas associated with a large turbid effusion. Histology confirmed metal related inflammatory change and microbiology specimens confirmed the absence of infection. DISCUSSION. The local detrimental effects of metal debris are well documented. We believe this is the first series with a proven link between these soft tissue problems and dislocation. Every case of large diameter metal on metal hip in our unit that has dislocated has been proven to be associated with metallosis and has required revision

Introduction. Large diameter femoral heads provide increased range-of-motion and reduced dislocation rates compared to smaller diameter femoral heads. However, several recent studies have reported that contemporary large head prostheses can directly impinge against the local soft tissues leading to anterior hip pain. To address this we developed a novel Anatomically Contoured large diameter femoral Head (ACH) that maintains the profile of a large diameter femoral head over a hemispherical portion and then contours inward the distal profile of the head for soft-tissue relief. We hypothesized that the distal contouring of the ACH articular surface would not affect contact area. The impact of component placement, femoral head to acetabular liner radial clearance, and joint loading during different activities was investigated. Methods. A finite element model was used to assess the femoroacetabular contact area of a 36 mm diameter conventional head and a 36 mm ACH (Fig. 1). It included a rigid acetabular shell, plastically deformable UHMWPE acetabular liner, rigid femoral head and rigid femoral stem. The femoral stem was placed at 0°, 10° and 20° of anteversion. The acetabular shell and liner were placed in 20°, 40° and 60° of abduction and 0°, 20° and 40° of anteversion. The femoral head to acetabular liner radial clearances modeled were 0.06 mm, 0.13 mm and 0.5 mm. Three loading cases corresponding to peak in vivo loads during walking, chair sit and deep-knee bend were analyzed (Fig. 2). This allowed a range of component positions and maximum joint loads to be studied. Results. Under all tested conditions there was no difference between the two implants (Fig. 3). The contact area for both prosthesis depended on the radial clearance between the head and liner. The conventional head contact area (standard deviation) in mm. 2. for 0.5 mm, 0.13 mm and 0.06 mm of radial clearance was 230.5 (70.2), 419.8 (48.7) and 575.4 (60.1) respectively. Similarly, for the ACH these were 230.5 (70.4), 420.1 (48.7) and 575.9 (59.4). The average data for a head and radial clearance combination included all component placements and load conditions completed. A student T-Test (p = 0.05) confirmed that the ACH had the same contact area as the conventional head for all radial clearances. Conclusion. This study showed that, as intended, an anatomically contoured large diameter femoral head designed to provide soft-tissue relief maintained the load bearing articular contact area of a conventional implant. The novel ACH prosthesis could mitigate the risk of soft-tissue impingement with contemporary large head implants while retaining their benefits of additional stability and range-of-motion

Introduction. Acetabular revision surgery is challenging due to severe bone defects. Burch-Schneider anti-protrusion cages (BS cage: Zimmer-Biomet) is one of the options for acetabular revision, however higher dislocation rate was reported. A computed tomography (CT)-based navigation system indicates us the planned direction for implantation of a cemented acetabular cup during surgery. A large diameter femoral head is also expected to reduce the dislocation rate. The purpose of this study is to investigate short-term results of BS cage in acetabular revision surgery combined with the CT-based navigation system and the use of large diameter femoral head. Methods. Sixteen hips of fifteen patients who underwent revision THA using allografts and BS cage between September 2013 and December 2017 were included in this study with the follow-up of 2.7 (0.1–5.0) years. There were 12 women and three men with a mean age of 78.6 years (range, 59–61 years). The cause of acetabular revision was aseptic loosening in all hips. The failed acetabular cup was carefully removed, and acetabular bone defect was graded using the Paprosky classification. Structural allografts were morselized and packed for all medial or contained defects. In some cases, solid allograft was implanted for segmental defects. BS cage was molded to optimize stability and congruity to the acetabulum and fixed with 6.5 mm titanium screws to the iliac bone. The inferior flange was slotted into the ischium. The upside-down trial cup was attached to a straight handle cup positioner with instrumental tracker (Figure 1) and placed on the rim of the BS cage to confirm the direction of the target angle for cement cup implantation under the CT-based navigation system (Stryker). After removing the cement spacer around the X3 RimFit cup (Stryker) onto the BS cage for available maximum large femoral head, the cement cup was implanted with confirming the direction of targeting angle. Japanese Orthopedic Association score (JOA score) of the hip was used for clinical assessment. Implant position, loosening, and consolidation of allograft were assessed using anterior and lateral radiographies of the pelvis. Results. Fifteen hips had a Paprosky IIIB defect, and one hip had a pelvic discontinuity. JOA score significantly improved postoperatively. No radiolucent lines and no displacement of BS cage could be found in 9 of 15 hips. Consolidation of allografts above the protrusion cage was observed in these patients. Displacement of BS cage (>5mm) was observed in 6 hips and displacement was stopped with allograft consolidation in 5 of 6 hips. The other patient showed lateral displacement of BS cage and underwent revision surgery. Average cup inclination and anteversion angles were 37.7±5.0 degree and 24.6±7.2 degree, respectively. 12 of 16 patients were included in Lewinnek's safe zone. One patient with 32 mm diameter of the femoral head had dislocation at 17 days postoperatively. All patients who received ≥36mm diameter of femoral head showed no dislocation. Conclusions. CT-based navigation system and the use of large femoral head may influence the prevention of dislocation in the acetabular revision surgery with BS cage for severe acetabular bone defects

Introduction. Current literature supports the use of total hip replacement (THR) for the treatment of displaced intra-capsular proximal femoral fractures (DIPFF). Case series of patients receiving this treatment show dislocation rates higher than that of patients who have THR to treat osteoarthritis. Large diameter THR have mechanical advantages in terms of dislocation and their role in PFF has yet to be assessed. Objectives. To assess the role of large-diameter total hip replacements on the rate of dislocation when used to treat displaced intra-capsular proximal femoral fractures. Design: Single surgeon, case series. Setting: Level I trauma centre. Inclusion criteria:. Displaced intra-capsular proximal femoral fracture (Garden III & IV). Independently mobile pre-operatively for distances greater than a mile, with no more than 1 stick as a mobility aid. Abbreviated mental test score of 9/10 or greater. Exclusion criteria:. Patient under 60. Pathological fractures. Additional fractures of the femur. Outcomes. Mortality. Morbidity (Including dislocation). Oxford Hip Score. SF12. Patients/Participants: Retrospective study to assess patients who presented between May 2006 and December 2008 and met the requirements had a CPTÒ (Zimmer) cemented femoral stem, using 3. rd. generation cementation techniques, and large diameter Duronò (Zimmer) head and cup (uncemented) inserted as a primary procedure via a modified Hardinge technique. Follow up was via routine clinic appointments, letter to GP and phone conversation with patient. Results. 67 patients were selected (49 female) average age was 74.6 (67–87). Follow-up was for an average of 14 months (3–39 months). No dislocations or deaths were recorded for this period of time. Conclusions. This study suggests that the high rates of dislocation associated with THR for PPF can be limited by the use of large diameter components. This study should be followed up by a multi-centre multi-surgeon study

High failure rates have been associated with large diameter metal-on-metal total hip replacements (MoM THR). However there is limited literature describing the outcomes following the revision of MoM THR for adverse local tissue reaction (ALTR). A total of 98 large diameter MoM THRs underwent revision for ALTR at our institution. The data was obtained from the clinical records and included the demographics, intra-operative findings of ALTR and post-operative complications. Any subsequent procedures and re-revision for any reason was analysed in detail. The clinical outcome was measured using functional outcome scores using the Oxford hip score (OHS), Western Ontario and McMaster Universities osteo-arthritis index (WOMAC) score and Short Form (SF12). The mean age of the patients at the time of revision was 58.2 yrs. At a mean follow-up of 3.9 years (1.0 to 8.6) from revision for ALTR, there were 15 hips (15.3 %) with post-operative complications and 8 hips (8 %) requiring re-revision. The Kaplan–Meier five-year survival rate for ALTR revision was 91 % (95% confidence interval 78.9 to 98.0). There were no statistically significant predictors of re-revision. The rate of postoperative dislocation following revision was 9.2% (9 hips). The post-operative functional outcome depends on the intra-operative findings of tissue destruction secondary to ALTR. The short term results following revision of large diameter MoM THR for ALTR are comparable with other reports in the literature. The use of constrained liners reduces the incidence of post-operative dislocation. There is an increased risk of postoperative instability following revision THR for ALTR. Early identification and intervention seems to be the logical approach in the management of patients with ALTR

Introduction. Fatigue and wear at the head/stem modular junction of large diameter total hip replacements can be exacerbated as a result of the increase in frictional torque. In vivo, a “toggling,” anterior-posterior (A-P) movement of the head taper on the trunnion may facilitate corrosion in the presence of physiological fluids, leading to increased metal ion release. Clinically, metal ion release has been linked to the formation of pseudo tumours and tissue necrosis [1]. Aims. In this investigation, a large diameter metal on metal THR was tested on a rig designed to recreate the toggling motion at the head/stem junction. Post-test analyses are conducted to look for evidence of mechanical and corrosive damage. Methods and Materials. A 58 mm diameter metal head (12/14 taper) was assembled onto a sectioned Freeman stem affixed to custom designed rig that enabled both, axial loads and a frictional torque (for the AP toggle load) about the rotation of the femoral head to be applied as shown in Figure 1. A linear variable differential transformer (LVDT), which had a minimum resolution of 0.5 microns, was positioned in contact with the neck directly under the modular head to track A-P movements at the junction. An axial load of 150N with toggle loads varying between 100 (± 50N) and 200N (± 50N) at 1 Hz were run on 4 taper assemblies, 2 dry and 2 wet (incorporating a physiological fluid at the junction) between 400,000 and 600,000 cycles. Movement at the junction was recorded, followed by visual inspection and RedLux® surface profile analysis of the taper and trunnion. Results and Conclusion. The LVDT could successfully record movement at the junction. Initially (∼1000 cycles), the movement at the junction was found to be variable and between 5–10 microns, which can be attributed to the taper “bedding-in” on to the trunnion. The movement was then found to steadily increase before stabilising. The dry tapers recorded motion ranging between 5–15 microns, and between 10–20 microns for the wet taper. Visual inspection post testing showed minimal or no damage on the trunnion or taper surfaces on the dry tests. However, the trunnion and taper on the wet samples displayed marks and scratches on the surface (Figure 2). In addition, there was visible surface discolouration on both wet taper assemblies but none observed on the dry assemblies. This was further corroborated by Redlux topography measurements that also showed that material had been removed from both surfaces. The pilot study showed that A-P toggle movements at the junction could be produced by incorporating torque about the rotation of the head. Damage was evident on both the trunnion and taper surfaces, and discoloration was observed at the junction when fluid was introduced

Dislocation remains among the most common complications of, and reasons for, revision of both primary and revision total hip arthroplasties in the United States. Hence, there is great interest in maximising stability to prevent this complication. Highly cross-linked polyethylene has allowed us to increase femoral head size, without a clinically important increase in wear. Head size has long been recognised to have a strong influence on the risk of dislocation postoperatively. As femoral head size increases, stability is augmented, secondary to a decrease in component-to-component impingement, which is theoretically eliminated at head sizes greater than 36mm in diameter (however osseous impingement can still occur). Larger head sizes also greatly increase the “jump distance” required for the head to dislocate (in an appropriately positioned cup) and eliminate the need for skirts. Level one studies support the use of larger diameter heads as decreasing the risk of dislocation following primary and revision THA. Larger diameter heads do, however, have negatives with the most recent concern being larger forces imparted upon the trunnion, which may contribute to adverse local tissue reactions (ALTR) which have recently been reported in patients with a metal on polyethylene bearing. However, in the series by Cooper et al, 32mm was the most common head size identified with no head sizes >36mm in this series. This suggests that the cause of ALTR is probably multifactorial and while femoral head size may be a contributor, the trunnion itself may be more important including its diameter, length and modulus of elasticity as well as the specific finish of the taper. Finally, when larger femoral head sizes are used in smaller acetabular components, the result is a thinner polyethylene liner, which may increase the risk of liner breakage. Larger diameter bearings may also increase the risk of squeaking in ceramic on ceramic bearing couples. Hence, the decision on femoral head size probably should include a balance between patient risk factors for instability and the risks of increased head size. Hence for revision procedures, and in primary cases where the risk of dislocation is known to be high, the risk of a larger femoral head is probably outweighed by the benefits of enhanced stability if a larger femoral head is utilised

Introduction. We conducted independent wear analysis of retrieved metal on metal (MoM) hip components from around the world. All patients with resurfaced hips who developed adverse reactions to metal debris (ARMD) were found to have increased wear of the bearing surfaces. This was untrue in patients with large diameter (?36mm) MoM total hip replacements. This led us to search for other factors leading to ARMD. Methods. MoM THR explants retrieved from 78 patients suffering ARMD underwent full volumetric wear analysis of bearing surface and taper-junctions using coordinate measuring machine. Scanning electron microscopy (SEM) used to characterise material composition of specific areas. Results. 34 MoM THRs were found to have relatively low bearing surface wear (< 3mm. 3. /year). In each of these cases, material loss up to 60 microns wear depth was identified on the internal taper-junctions of femoral components. However, volumetric loss was rarely >5mm. 3. Similarly only 65% of metal ion levels of these patients were found to be greater than the MHRA guidance figure (7µg/L). Patterns of material loss at the tapers were consistent with antero-posterior force splaying open the taper-junction. This characteristic pattern was identified in number of commercially available devices (titanium and cobalt chromium stems). Soft tissue lesions were severe in patients found to have taper damage. Histology confirmed severe ALVAL with lymphoid neogenesis in majority cases, suggesting that wear debris from taper junctions may have greater potential to stimulate adverse immune response. Discussion. The results suggest that forces transmitted from large diameter hard-on-hard bearing surfaces are sufficient to cause mechanical damage to modular junctions with secondary localised corrosion. We urge caution in the use of these designs and recommend a re-evaluation of the stem head interface

Introduction:. High failure rates with large diameter, metal on metal hip replacements have highlighted a potential issue with the head/stem taper junction as one of the significant sources of metal ion release. Postulated reasons as to why this may be such a problem with large head metal on metal hip replacements is due to the increased torque achieved by the larger head size. This may be responsible for applying greater micromotion between the head and stem taper and consequently greater amounts of fretting corrosion. The aim of this study was to perform short term in vitro electrochemical tests to assess the effect of increasing head diameter and torque on the fretting corrosion susceptibility of the head/stem taper interface and to investigate its effect on different material combinations. Methods:. 36 mm Cobalt Chrome (CoCr) femoral heads were coupled with either a CoCr or Titanium (Ti) stem with 12/14 tapers, all with a smooth surface finish. Increasing perpendicular horizontal offsets in the sagittal plane created incremental increases in torque. Offset increments of 0 mm, 5.4 mm and 7.5 mm were selected (Figure 1) to simulate the torque force equivalent to 9 Nm, 12 Nm and 17 Nm. An inverted hip replacement setup was used (ASTM F1875-98) (Figure 2). Components were statically loaded at 0 kN and 2.3 kN prior to sinusoidal cyclic loading and electrochemical testing. Mean & fretting currents were calculated every 50 cycles up to a maximum of 1000 cycles of sinusoidal cyclic loading at 3 Hz along with the Overall Mean Current (OMC), Overall Mean Fretting Current (OMFC) and Overall Current change (OCC). Results:. There was a significant increase in the mean current (R = 0.992, p = 0.008) and fretting current (R = 0.929, p = 0.071) for CoCr-CoCr and in the mean current (R = 0.780, p = 0.005) and fretting current (R = 0.810, p = 0.006) for CoCr-Ti material combinations, with increasing femoral offsets. The highest currents (mean and fretting) were produced at 7.5 mm and the lowest at 0 mm offsets. The proportional relationship between torque and corrosion was observed for both CoCr-CoCr and CoCr-Ti material combinations. With low torques we saw higher OMC and OMFC with the Co-Ti material combination however with higher torques we saw higher OMC and OMFC with the CoCr-CoCr combination (Figure 3). Conclusion:. Increasing torque leads to increased susceptibility to fretting corrosion at the modular head/stem taper interface of total hip replacements for both head stem material combinations. This study highlights the risk of high frictional torque, independent of material combination, on the head/ stem with the use of large heads. This is particularly relevant with the increasing use of larger diameter femoral heads across all bearing material combinations, in current hip arthroplasty practice

Squeaking ceramics bearing surfaces have been recently recognised as a problem in total hip arthroplasty. The position of the acetabular cup has been alluded to as a potential cause of the squeaking, along with particular combinations of primary stems and acetabular cups. This study has used the finite element method to investigate the propensity of a new large diameter preassembled ceramic acetabular cup to squeaking due to malpositioning. A verified three-dimensional FE model of a cadaveric human pelvis was developed which had been CT scanned, and the geometry reconstructed; this was to be used to determine the behaviour of large diameter acetabular cup system with a thin delta ceramic liner in the acetabulum. The model was generated using ABAQUS CAE pre-processing software. The bone model incorporated both the geometry and the materials properties of the bone throughout based on the CT scan. Finite element analysis and bone material assignment was performed using ABAQUS software and a FORTRAN user subroutine. The loading applied simulated edge loading for rising from a chair, heel-strike, toe off and stumbling. All results of the analysis were used to determine if the liner separated from the shell and if the liner was toggling out of the shell. The results were also examined to see if there was a propensity for the liner to demobilise and vibrate causing a squeaking sound under the prescribed loading regime. This study indicates that there is a reduction in contact area between the ceramic liner and titanium shell if a patient happens to trip or stumble. However, since the contact between the liner and the shell is not completely lost the propensity for it to squeak is highly unlikely

Edge loading commonly occurs in all bearings in hip arthroplasty. The aim of this study compares metal bearings with edge loading to alumina bearings with edge loading and to metal bearings without edge loading. Seventeen failed large diameter metal-on-metal hip bearings (8 total hips, 9 resurfacings) were compared to 55 failed alumina-on-alumina bearings collected from 1998 to 2010. The surface topography of the femoral heads was measured using a chromatically encoded confocal measurement machine (Artificial Hip Profiler, RedLux Ltd.). The median time to revision for the metal hip bearings and the alumina hip bearings was 2.7 years. Forty-six out of 55 (84%) alumina bearings and 9 out 17 (53%) metal bearings had edge loading wear (p<0.01). The average volumetric wear rate for metal femoral heads was 7.87 mm3/yr (median 0.25 mm3/yr) and for alumina heads was 0.78 mm3/yr (median 0.18 mm3/yr) (p=0.02). The average volumetric wear rate for metal heads with edge loading was 16.51 mm3/yr (median 1.77 mm3/yr) and for metal heads without edge loading was 0.19 mm3/yr (median 0 mm3/yr) (p=0.1). There was a significant difference in gender, with a higher ratio of females in the alumina group than the metal group (p=0.02). Large diameter metal femoral heads with edge loading have a higher wear rate than smaller alumina heads with edge loading. Metal-on-metal bearings have low wear when edge loading does not occur

Introduction. Metal on metal hip arthroplasty continues to be controversial. Emerging evidence suggests that there are multiple modes of failure, and that the results of revision surgery are influenced by host and implant factors. Methods. This study compares a single surgeon series of hip resurfacings (Birmingham Hip Resurfacing {BHR}) and large diameter metal on metal total hip replacements (LDMOMTHR). Primary outcome measures included survival rates, failure secondary to histologically identified Adverse Reaction to Metal Debris (ARMD), and patient reported outcome measures (Oxford Hip Score {OHS}) following revision. Between 1999 and 2005, 458 BHR and 175 LDMOMTHR were performed. At latest review 43 BHR's (9.4%) and 28 LDMOMTHR's (14%) have been revised. Results. Failure secondary to ARMD was significantly greater in LDMOMTHR compared to BHR failures (89% and 16% respectively). Histology demonstrated a higher Aseptic Lymphocytic Vascular and Associated Lesions (ALVAL) score in the LDMOMTHR failures than the BHR failures (8.6 LDMOMTHR, 6.3 BHR). Patient reported outcomes were better following revision for failed BHR compared to LDMOMTHR. There was no difference between the revision cohorts for cup inclination, metal ion levels and gender. Failure of the BHR has predominantly been due to those causes unique to resurfacing such as avascular necrosis and fracture. In our series, aggressive ALVAL was unusual and clinical outcome following revision was superior compared to LDMOMTHR failures. The likely mechanisms that are responsible for the differences in outcome and the clinical implications will be discussed

Introduction. The first highly crosslinked and melted polyethylene acetabular component for use in total hip arthroplasty was implanted in 1998 and femoral heads larger than 32mm in diameter introduced 2004. The purpose of this study was to re-assemble a previous multi-center patient cohort in order to evaluate the radiographic and wear analysis of patients receiving this form of highly crosslinked polyethylene articulating against large diameter femoral heads at a minimum of 10 years follow-up. Methods. Two centers contributed patients to this ongoing clinical study. Inclusion criteria for patients was: primary THR; femoral heads greater than 32mm; minimum 10 year follow-up. 69 hips have been enrolled with an average follow-up of 11.2 years (10–15), 32 females (50%). Wear analysis was performed using the Martell Hip Analysis software. Radiographic grading was performed on the longest follow-up AP hip films. The extent of radiolucency in each zone greater than 0.5mm in thickness was recorded along with the presence of sclerotic lines and osteolysis. Results. Wear analysis: Using the average of the slopes of the individual regression lines, the wear rate was 0.004±0.094mm/yr. Using the early to latest film method, the wear rate was 0.035±0.076mm/yr. Radiographic analysis: Acetabular side: the greatest incidence of radiolucency occurred in zone 1 at 27%; sclerotic lines had a less than 2% incidence in any of the 3 zones; there was no identified osteolysis. Femoral side: the highest incidence of radiolucencies was in zones 1 and 3, 7% and 4%; sclerotic lines were rare in any zone, maximum in zone 3, 4%; there was no identified osteolysis. Conclusion. The wear of this form of irradiated and melted highly crosslinked polyethylene remained at levels lower than the detection limit of the software at minimum 10 year follow-up and there was no identified osteolysis

To report the clinical, functional and radiological outcome of consecutive primary hip arthroplasties using large diameter (36mm and above) ceramic bearing couples. We believe this to be one of the first independent series. We prospectively reviewed 519 consecutive primary THA using fully HAC coated acetabular shell and fully HAC coated stem (JRI Ltd) in 502 patients, with minimum follow-up of 32 months. A Biolox-Delta ceramic liner with an 18 deg taper and Biolox-Delta ceramic head (36mm and 40mm) were used in all cases, by 3 surgeons. None were lost to follow-up. Clinical outcome was measured using Harris, Charnley Oxford, EuroQol EQ-5D scores. Radiographs were systematically analysed for implant position, loosening, migration, osteolysis. Return to sports and hobbies were recorded. Mean age was 64.9 yrs (11–82yrs). There were no dislocations. 50–62mm acetabular shells were used. 36 mm head was used in 92% of cases. No acetabular revisions were performed for aseptic loosening. Other re-operations were for infection (1), peri-prosthetic fractures (1). The mean Harris and Oxford scores were 95 (88–97) and 14.1 (12–33) respectively. Harris and Oxford scores were 95 (88–97) and 14.1 (12–33) respectively. The Charnley score was 5.7 (5–6) for pain, 5.8 (4–6) for movement and 5.9 (4–6) for mobility. There was a significant improvement in the range of movement of the hip. There was no migration of acetabular component. Acetabular radiolucencies were present around one shell. No acetabular liner wear was demonstrated in CT Scans. Mean inclination was 7.4deg(37–65). Mean EQ-5D description scores and health thermometer scores were 0.84 (0.71–0.92) and 88 (66–96). With an end point of definite or probable loosening, the probability of survival was 100%. Overall survival with removal or repeat revision of either component for any reason as the end point was 99.1%. The results of this study show an excellent clinical and functional outcome and support the use of a fully coated prosthesis with ceramic bearing couples. We envisage monitoring and prospectively reporting the long-term outcome of this series of patients

Purpose of the study. to verify, after a period of 5 years, that no particular complication overshadows the benefits of a large diameter metal-on-metal articulation in combination with a conventional femoral stem with regard to stability and functional result. Patients and methods. Between October 2003 and May 2005, 100 hips in 99 patients were treated with an uncemented Emeraude stem and a Durom Resurfacing Cup made from cobalt-chrome with high carbon content. Mean age at time of surgery was 60 years. 80 of the operated patients were reviewed after a follow-up of 5 years and two months: the results are expressed according to Merle d'Aubigné and Harris, by means of the UCLA and the WOMAC scores. The radiographs were reviewed by independent observers. The patients underwent a chrome and cobalt test in whole blood. Of the 20 patients lost to follow-up, 13 had died, 1 could no longer be located, 1 had been revised because of a peri-prosthetic fracture and the remaining 5 were unable to show up for the follow-up examination. A telephone interview and the WOMAC did not reveal any complication in their cases. Results. The mean Merle d'Aubigné and Harris scores increase from 9.8 to 16.3 and from 37.4 to 79.9, respectively. The UCLA score improves from 4.2 to 6.5. The corrected WOMAC is 77.2%. But the results after 1 year show a distinct difference between the first 30 patients (Harris score of 58.2) and the subsequent patients (Harris score of 82.4). The radiographic analysis does not show any migration; the observed radiolucencies, whether around the fixation wings or at the level of the surface coating, are not progressive; mean cup inclination is 52°. The mean values for chrome are 1.95 μg/l and for cobalt 2 μg/l. Discussion and conclusion. This study confirms the relevance of this concept with regard to stability (no dislocations) and functional result, and reveals no particular complication. The less good clinical results are to be attributed to the pain previously noted in the first 30 cases, before our technical experience led us to impact an undersized cup in respect to the last used rasp. This technique enables a better centering of the cup, ensures that the latter does not protrude nor expose it to excessive equatorial compression, which seems to cause pain. We have no doubt that it is this technical modification that has spared us the complications that have led some of our colleagues to abandon this type of implant

Introduction. Large diameter metal-on-metal hip arthroplasty (LDMMTHA) provides benefits of reduced dislocation rates and low wear. The use of modular systems allows better restoration of hip biomechanics. There have been reports of modular LDMMTHAs with tapered sleeves generating excessively high metal ions, due to possible mismatch between the titanium stem and the cobalt-chrome sleeve and the dual Morse tapers involved. We evaluated metal ion levels in LDMMTHA patients with and without a cobalt-chrome (CoCr) tapered sleeve. Methods. A cross-sectional series of 91 patients with proximal porous titanium alloy stem LDMMTHA with identical design CoCr bearings, attending a 1 to 2-year review were assessed with routine clinical and radiographic examinations, hip scores and metal ion analysis. Of these 65 had a single Morse taper between monoblock CoCr heads and the stems. Twentysix had a tapered cobalt-chrome sleeve in addition, with the resultant dual taper. Mean bearing diameter was 46 mm in both groups and mean age was 58 years in the monoblocks and 66 years in the tapered sleeve group. Results. Mean Oxford Hip score is worse in the tapered group (14.7) than in the monoblocks (12.6). All patients had well-functioning hips clinically and radiologically. Median blood cobalt and chromium are higher in the tapered sleeve (2.3μg/L and 1.8 μg/L) compared to the monoblocks (1.8 μg/L and 1.1 μg/L). Urine cobalt and chromium levels in the tapered sleeve (13.8 μg/24 hr and 5.3 μg/24 hr) also are higher than those in the monoblocks (12.2 μg/24 hr and 4.5 μg/24 hr respectively). Discussion and Conclusion. The limitation of this study is that it is a cross-sectional study. The results indicate that the use of a tapered sleeve in total hip arthroplasty does lead elevation of cobalt and chromium levels and the difference is statistically significant. However these levels are not as high as the levels reported with some other hip systems which have been withdrawn and the clinical significance of the elevated levels in the present study is unknown

Corrosion at the taper interface between the femoral head and the femoral stem is well described in metal-on-polyethylene (MoP) hips but previously was undetermined in large diameter head metal-on-metal (LHMoM) hips. The high failure rate of the articulating surface replacement (ASR) XL hip system has been partly attributed to susceptibility to corrosive damage at the taper interface. It was not known if other hip manufacturers are liable to taper corrosion. Therefore the aim of this study was to quantify the prevalence and severity of taper corrosion in LHMoM hips and compare corrosion across five different current generation manufacturers. Taper corrosion was analysed in a consecutive series of the five most common hip types at our retrieval centre: ASR XL, DePuy (n=49); Birmingham hip resurfacing, Smith & Nephew (n=33), Durom, Zimmer (n=31), M2a Magnum, Biomet (n=14) and Cormet, Stryker (n=10). A four-scale peer-reviewed qualitative corrosion scoring system was used to quantify corrosion (none, mild, moderate and severe). Evidence of corrosion was observed in 86% of components, with at least moderate corrosion observed in 61%. No difference in corrosion was observed between the ASR XL and the other manufacturers (p=0.202). There was still no difference seen when all manufacturers were compared individually (p=0.363). A positive correlation was observed between corrosion and femoral head diameter (r=0.224, p=0.021). However no relationship was observed with implantation time (r=0.163, p=0.118). Our study indicates that taper corrosion is common in LHMoM hips and affects all hip types equally. The clinical significance of this finding is that all hip types will be susceptible to the complications of corrosion, such as third body wear and osteolysis. Furthermore recent reports indicate that corrosive debris released from the taper interface may play a role in the formation of pseudotumours and adverse soft-tissue reactions. We found that larger femoral head sizes showed greater corrosion, which suggests that high torque increases fretting corrosion of the taper interface. Future work must determine the optimum femoral head size and investigate the chemical composition of the corrosive debris