Introduction. Corrosion products from modular taper junctions of hip prostheses have been implicated in adverse local tissue reactions after THR. Numerous factors have been proposed as the root causes of this phenomenon, including implant design and materials, manufacturing variables, intraoperative assembly, and patient lifestyle. As significant taper damage only occurs in a few percent of cases of THR, we have addressed this complication using a “forensic” examination of retrieval specimens to gain insight into the factors initiating the cascade leading to irreversible damage of the modular interface. In this study we report the categorization of over 380 retrievals into groups having shared damage patterns, metallic composition, and interface surface geometries to isolate the genesis of mechanically-assisted corrosion and its relation to intraoperative assembly, manufacturing, and postoperative loading. Methods. A total of 384 femoral components were examined after retrieval at revision THR. The implants were produced by a diverse range of manufacturers, 271 in CoCr, and 113 in TiAlV, with both smooth (253) and machined (131) tapers. Initially, the implants were sorted into groups based on composition and taper roughness. Each trunnion was then cleaned to remove organic deposits and examined by stereomicroscopy at X6-X31. After an initial pilot study, we developed a classification system consisting of 8 basic patterns of damage (Table 1). We then classified all 384 trunnions according to this 8-group system. The prevalence of each pattern was calculated on the basis of both composition and surface texture of the trunnion. Results. Overall, 81% of the trunnions had visible areas of surface damage, which varied as a function of composition (CoCr: 77%; TiAlV: 90%; p=0.002) and finish (smooth: 88%; machined: 67%; p<0.001). The most common pattern of damage was a circumferential ring at the base of the taper (24%) followed by a group with slight fretting or assembly damage distributed over the entire taper (19%). Damage to one quadrant at the bottom third was seen in approximately 18%. When combining material types, 41% of smooth tapers had circumferential patterns of damage corresponding to groups 2, 3, and 5. Conversely, 77% of the machined tapers had damage limited to one side or on two opposite sides (Patterns 4, 6, 7, 8, and 9). Discussion. Our results show that the pattern and location of damage is influenced not only by composition and surface texture, but can also be an indicator of component fit. The damage patterns observed on almost half (45%) of the trunnions were not circumferential (Chart 2), suggesting that misalignment of the head during assembly may be responsible for initiating the corrosion cascade in stems with machined taper surfaces. Summary. We categorized over 380 implant retrievals into groups having shared damage patterns, metallic composition, and interface surface geometries to isolate the genesis of corrosion

The current, most popular recommendation for cup orientation, namely the Lewinnek box, dates back to the 70's, that is to say at the stone age of hip arthroplasty. Although Lewinnek's recommendations have been associated with a reduction of dislocation, some complications, either impingement or edge loading related, have not been eliminated. Early dislocations are becoming very rare and most of them probably occur in “outlier” patients with atypical pelvic/hip kinematics. Because singular problems usually need singular treatments, those patients need a more specific personalised planning of the treatment rather than a basic systematic application of Lewinnek recommendations. We aim in this review to define the potential impacts that the spine-hip relations (SHRs) have on hip arthroplasty. We highlight how recent improvements in hip implants technology and knowledge about SHRs can substantially modify the planning of a THR, and make the «Lewinnek recommendations» not relevant anymore. We propose a new classification of the SHRs with specific treatment recommendations for hip arthroplasty whose goal is to help at establishing a personalized planning of a THR. This new classification (figures 1 and 2) gives a rationale to optimize the short and long-term patient's outcomes by improving stability and reducing edge loading. We believe this new concept could be beneficial for clinical and research purposes

In order to enhance the acceptance of computer assisted surgery in joint replacement, a development-cooperation with BrainLAB, Germany was set up to develop a user-friendly handheld navigation device. A sterile draped Apple® IPod-Touch which is placed into a hardcover cradle, is used as navigation monitor and touchscreen control. Different instruments, such as navigation-pointer are attached to the cradle. In addition the workflows for TKR and THR procedures have been optimised. Therefore the main focus for TKR is navigation of femoral and tibial resection as well as leg alignment control. For the THR the system enables an intraoperative control of leg-length and femoral-offset measurement in comparison with the preoperative situation. Each step of the procedure is supported by video animations of the specific navigation workflow. Between September and December 2010 the first clinical study on the usability in TKR and THR was performed for 20 cases using a prototype system. The study was approved by the local ethic committee and the “German Federal Institute for Drugs and Medical Devices (BfArM)”. Special interest was taken to the aspects of usability and the necessary time periods for specific steps of the procedure. Usability was measured for specific time periods of the procedure assessment of the usability of the surgical team. In addition postoperative x-rays were evaluated for implant position, leg alignment for TKR and hip joint geometry for THR cases. Throughout the study for each assigned patient the procedure could be performed as planned. Several design inputs were identified for further improvement of the final system. Therefore time measurements of the first five cases were excluded. For the TKR cases the registration process of the last 5 cases was less than 3 minutes. The interval for the tibial resection was between 3 and 7 minutes (aligning tibial cutting block – end of tibial verification). The interval for the distal femur resection was between 7 and 11 minutes (aligning femoral cutting block – end of femoral verification). All 10 Patients showed a final leg alignment on the postoperative standing x-ray within the save-zone of +/− 3° from neutral alignment. For the THR cases the preoperative registration period including the femoral head resection and acetabular registration was between 7 and 12 Minutes. Each final measurement of the hip geometry was done in less than 2 minutes. The evaluation of the pelvic ap-x-ray pre- and postoperative showed equivalent measurements of the new hip geometry compared with the intraoperative measured values. No specific complications occurred throughout the study. In conclusion the BrainLAB–DASH-System has shown a high grade of usability and very short learning curve within this first clinical study. The use of a standard Apple® IPod-touch as a user interface seems to enhance the acceptance of the navigation technique. Equivalent precision compared to standard navigation systems have been demonstrated

Introduction. A recent report based on the NARA database (Nordic Arthroplasty Register Association) found that the 10-year survivorship of patients under 50 with traditional total hip arthroplasty was only 83% in 14,600 cases. The purpose of this study was to compare our experience using metal-on-metal hip resurfacing arthroplasty (HRA) to treat these patients. Methods. from May 2001 to Feb 2012, a single surgeon performed 1029 metal-on-metal HRA in 855 patients younger than 50 years old. Three different implants were used in consecutive groups of patients, first the Corin hybrid HRA (182); then the Biomet hybrid HRA (306); and finally the Biomet uncemented HRA (541). The primary diagnoses were OA (707); dysplasia (125); osteonecrosis (98); post-trauma (28); Legg-Calve-Perthes (27) and others (44). The average age was 43±6 years; 74% were men; the average BMI was 27±4; mean femoral component size was 50±4 (range 40–62); the average T-score was 0±1. 37% of our patients reported a UCLA Activity level of 9 or 10 (impact sports). Six died with causes unrelated to their HRAs. The rate of follow-up was 94%. Our patients were not selected by any criteria except the surgeon's technical ability to perform an HRA. Results. There were a total 42 failures: acetabular component loosening in 15 cases (8 before two years) femoral component loosening in 9 cases; femoral neck fracture in 5 cases; adverse wear related failure (AWRF) in 4 cases; deep infection in 3 cases; recurrent dislocation in 1 case; other causes in 5 cases. With revision of any component as the end point, the Kaplan-Meier survivorship rate was 94.9% at 8 years and 92.5% at 10 years for the entire group. We compared survivorship between groups at shorter follow-up intervals to determine if results were improving. The survivorship rate at 8 years for Biomet Hybrid group was 95.8%, which was significantly better than 89.1% for the earlier Corin Hybrid group; the survivorship rate at 5 years for the latest Biomet Uncemented HRA group was 98.7%, also better than 96.5% for the prior Biomet Hybrid group. (P=0.0001). Conclusion. Metal-on-metal hip resurfacing has less than half the 10-year failure rate of THR in young patients. As HRA technology and experience improve, our data suggests that the results further improve. HRA currently meets the NICE criteria for 10-year survivorship of implants while THR doesn't in young patients. Our HRA patients are allowed unrestricted activity, while THR patients are typically restricted. AWRF (0.4%) is a minor problem that has been blown far out of proportion to its significance. Patient selection against HRA in certain subgroups (women, small bearings, history of metal allergy) may not be advisable based on our results

Introduction. The benefits of femoral head-neck modularity in hip surgery have been recognized for decades. However, reports of head/neck taper fretting & corrosion has led to research being conducted, yet the clinical effect of these processes remains unclear. Whilst femoral head size, material and the characteristics of the taper have been a focus of research, potential contributing variables such as in vivo head-neck assembly technique on the performance of these connections is not clear. We performed an observational study to investigate variation in femoral head-neck taper assembly during surgery, with the initial focus being the number of head impactions. Methods. From May 2013 to October 2014, nineteen surgeons who specialized in hip surgery from a wide demographic (North America, Europe and Asia) participated in a video review on current surgical practice in total hip arthroplasty (THA). The surgeons were unaware of any specific parameter, including taper assembly, which would subsequently be analyzed. Twenty-seven THA surgeries were reviewed against a specific set of questions relating to factors in the modular femoral head-neck assembly process. The focus of the current study was the number of impaction blows to seat the modular femoral head on the implanted stem. Results. Variation occurred in the number of observed impactions used to assemble the components with an impaction range from 1 to 11 (Figure 1). The two most favored number of impaction strikes were a single strike (37% of reviewed cases) and three strikes (22% of reviewed cases). Further variability was observed between individual surgeon cases where number of strikes was different in each observed case. This occurred on two occasions with two different surgeons. The impaction number was found to be independent of the side operated on (left or right) and also with the surgeons region of origin. However, a higher proportion of European surgeons favored 1–3 impactions (92% of European cases) compared to their North American (28.5% of North American Cases) and Asian (42.8% of Asian cases) counterparts. The impaction number variation was also independent of the material of the femoral head, with both metal and ceramic heads demonstrating this observed variation (Figure 2). Discussion. This observational review into the current surgical practice of femoral head assembly has shown that there is clear variation in this aspect of the THR surgery. The number of impactions is not correlated to head material, but may be related to the surgeon's training or local practice environment. Conclusion. This observational review into the current surgical practice of femoral head assembly has shown a level of variation in the way the modular junction is assembled through impaction. Further investigation into other aspects involved in femoral head assembly is required to understand the potential impact that these surgical practice variations may have on the functional performance of the modular taper junctions in THR

Introduction:. Total knee replacement (TKR) and total hip replacement (THR) reliably relieve pain, restore function, and ensure mobility in patients with advanced joint arthritis; however these results are not uniform across all patient populations. Moreover, it is well established that knee replacement patients have outcomes inferior to those undergoing hip replacement procedures with lower rates of dissatisfaction with post-operative function and pain relief. We compared baseline demographic and symptom profiles in patients from a US national cohort undergoing primary TKR and THR to determine whether differences in demographic make-up, pre-operative symptoms, or pre-existing co-morbidities might contribute to these differences observed post-operatively. Methods:. A cohort of 2375 patients undergoing primary TKR and THR was identified from the FORCE national research consortium from all surgeries performed between July 1. st. 2011 and March 30. th. 2012. This set of patients was derived from 120 contributing surgeons in 23 US states. Gathered data included patient demographics, comorbidity (Charlson Comorbidity Index), operative joint pain severity (Western Ontario and McMaster Universities Arthritis Index (WOMAC)), physical function (SF-36; Physical Component Score (PCS)), emotional health (SF-36; Mental Component Score (MCS)), and musculoskeletal burden of illness (Hip and Knee Disability and Osteoarthritis Outcome Scores; Oswestry Disability Index). Using descriptive statistics, we compared the baseline demographic characteristics and symptom profiles of patients undergoing TKR (n = 1362) and those undergoing THR (n = 1013). Results:. In this large national sample, patients receiving knee replacements were found to be significantly older (66.5 vs. 64.3 years), more obese (BMI 31.7 vs. 29.3), and less educated (p < 0.005) than those undergoing THR. TKR patients had higher rates of medical comorbidities, specifically diabetes, gastrointestinal ulcers, and cerebrovascular disease (p ≤ 0.006). Conversely, THR patients had significantly worse physical function (PCS 31.6 vs. 33.3), lower back pain (35.6% vs. 30.5% moderate-severe), and operative joint pain, stiffness, and function (p < 0.005) when compared to those undergoing TKR. Conclusions:. US patients undergoing primary TKR are older with more comorbidities, however THR patient baseline functional and musculoskeletal limitations are significantly greater than primary TKR patients. These data may help explain the variability in physical function after primary TKR as compared to primary THR

Introduction. Mechanically-assisted corrosion of the head-neck junction present a dilemma to surgeons at revision THR whenever the femoral component is rigidly fixed to the femur. Many remove the damaged femoral head, clean the femoral taper and fix a new head in place to spare the patient the risks associated with extraction and replacement of the well-functioning femoral stem. This study was performed to answer these research questions:. Will new metal heads restore the mechanical integrity of the original modular junction after impaction on corroded tapers?. Which variables affect the stability of the new interface created at revision THR?. Materials and Methods. Twenty-two tapers (CoCr, n=12; TiAlV, n=10) were obtained for use in this study. Ten stems were in pristine condition, while 12 stems had been retrieved at revision THR and with corrosion damage to the trunnion (Goldberg scale 4). Twenty-two new metal heads were obtained for use in the study, each matching the taper and manufacturer of the original component. The following test states were performed using a MTS Machine: 1. Assembly, 2. Disassembly, 3. Assembly, 4. Toggling and 5. Disassembly. All head assemblies were performed wet using 50% calf serum in accordance to ISO 7206-10. During toggling, each specimen's loading axis was aligned 25° to the trunnion axis in the frontal plane and 10° in the sagittal plane (Figure 1). Toggling was performed at 1Hz for 2,000 cycles with a sinusoidal loading function (230N–4300N). During loading, 3D motion of the head-trunnion junction was measured using a custom jig rigidly attached to the head and the neck of each prosthesis. Relative displacement of the head with respect to the neck was continuously monitored using 6 high resolution displacement transducers with an accuracy of ±0.6µm. Displacement data was independently validated using FEA models of selected constructs. Results. The average micromotion of the head vs trunnion interface was greatest at the start of loading and stabilized after approximately 50 loading cycles at an average of 30.6±3.2µm (Figure 2). For CoCr couples, interface motion dropped by 17% when a pristine head was mounted on a corroded stem compared to a new stem (25.7±2.7µm (pristine stem), vs. 30.1±4.6µm (corroded stem), p= 0.4023) (Figure 3). However, addition of a new CoCr head with a corroded titanium stem led to an 73% increase in interface motion after assembly with a new CoCr head (Corroded: 43.4±9.8µm, Pristine: 25.2±7.0µm, p=0.1661). The resistance to head-neck disruption was 15% higher in TIALV/CoCr couples compared to CoCr/CoCr (TiAlV: 2558 ±63N, CoCr: 2226±99N, p=0.0111) and was not affected by the presence of corrosion of the trunnion (1% loss of strength in each case). Discussion. Corrosion at the trunnion does not disrupt the mechanical integrity of the junction when a CoCr head is replaced on a CoCr taper. We are less sure about the mechanical integrity of a TiAlV taper demonstrated by a trend towards increased micromotion at this junction. Further work is required to better elucidate the role of dissimilar metals in the mechanical integrity of the head-neck junction

Hypothesis. The Synergy femoral component was introduced in 1996 as a second generation titanium proximally porous-coated tapered stem with dual offsets to help better restore femoral offset at THR. The purpose of this prospective study was to evaluate the long-term (minimum 10 year) clinical and radiographic results and survivorship of this femoral component at our institution. Methods & Analysis. From 1996 to 1999, 256 cementless Synergy femoral components were inserted and followed prospectively in 254 patients requiring THR. 185 were standard offset stems (72.3%) while 71 stems (27.7%) were high offset. The average follow-up was 11.2 years (range 10.0 to 12.9 years). Average age at index THR was 58.9 year. Two hundred and eight stems had standard porous coating while 48 had additional HA coating. Fifty-two cases were either lost to follow-up or had died prior to 10 years follow-up. Patients were followed prospectively using validated clinical outcome scores and radiographs. Kaplan-Meier survival analysis was performed. Results. All health-related outcomes were significantly improved from pre-operative with a mean Harris Hip score and WOMAC at last follow-up of 91.6 and 81.8, respectively. From the initial 256 femoral stems inserted, only 5 stems have been revised. Two stems have been revised for infection. Only one stem has been revised due to subsidence at nine months, likely as a result of a calcar fracture at the index THR. Two stems were revised for peri-prosthetic fracture as a result of patient falls. Radiographic review of remaining stems in situ identified no cases of loosening. Kaplan-Meier survivorship analysis of the femoral component, with revision for aseptic loosening, was 99.2% at 12 years. Conclusion. The Synergy femoral component, a second generation titanium proximally porous-coated tapered stem design with dual offsets, has demonstrated excellent clinical and radiographic results and long-term survivorship (99% at 10 years) at our institution

Purpose. The purpose of the study was to determine the rate of conversion from RSA to THR in a number of Canadian centers performing resurfacings. Method. Retrospective review was undertaken in 12 Canadian Centers to determine the rate of revision and reason for conversion from RSA to THR. Averages and cross-tabulation with Chi-Squared analysis was performed. kaplan Meier survivorship was calculated. Results. A total of 2810 resurfacings were performed up to December 2008. 770 hips had a minimum of 5 year follow-up. The overall survivorship of this group was 97.8%. 80 patients underwent conversion to THR. Five resurfacing systems were used. The reason for failure is reported: 21 were for femoral neck fracture, 25 were for loosening, 9 were for deep infection, 3 foravn, 4 pseudotumors, 2 for impingement, 6 for groin pain and 10 for other reasons. The cumulative conversion rate is 2.8%. The survivorship was significantly different analyzed by gender. The 5 year female survivorship was 95.4% and for males was 97.7%. Surgeon experience proved to be a significant factor in conversion rates. Conclusion. The revision rate to date with this new technology suggests that with increasing experience hip resurfacing arthroplasty remains an acceptable option for the treatment of hip arthritis

Introduction:. Femoral head surface roughness has been recognized as an important determinant of linear and volumetric polyethylene (UHMWPE) wear in total hip replacement (THR), particularly for metal heads. Fisher et al. 1. found that a 2- μm scratch with a 1- μm buildup of metal debris produced a 70-fold increase in the wear rate. Ceramic materials and hard-on-hard bearing couples have been introduced to provide more scratch resistance. However, THR bearing surfaces of all materials can become damaged during in vivo function, potentially impacting wettability. The purpose of this study is to quantify surface roughness as related to distinct damage types on retrieved femoral heads and to assess wettability of common bearing materials. Materials and Methods:. An IRB-approved archive of retrieved THR bearing components was queried, identifying 29 metal (CoCr) and ceramic (alumina, zirconia) femoral heads that had articulated with UHMWPE and ceramic acetabular liners, respectively. Mean in vivo functional duration was 5.5 ± 4.5 years (range, 1 month to 27 yrs), and patient age and weight averaged 68 ± 12 years (range, 36–81) and 72 ± 21 kilograms (range, 52–123), respectively. Retrieval reasons were dislocation (18), loosening (4), polyethylene wear (2), infection (1), squeaking (1) and unknown (3). Damage appearance and surface roughness were evaluated in a grid pattern of 49 zones distributed across the bearing surface of each head using optical microscopy to identify Mode-1 or Mode-2 wear and a non-contact interferometer (NT2000 & NPFLEX, Bruker Corp.) Wettability of smooth and rough CoCr and alumina materials was assessed using contact angle measurements (DSA30, Krüss USA). Results:. Among the metal heads, scratching was the most common damage (Mode-1) and was visualized on over 90% of all heads. Metal transfer and discoloration (Mode-2) damage, confirmed as titanium deposits, was visualized on 79% of dislocated heads. Zones with metal transfer had significantly higher surface roughness compared to zones without this damage (Table 1, p < 0.001). Among the ceramic heads, Mode-1 wear was visualized as a long, narrow wear region consistent with stripe wear. 2. and metal transfer (Mode-2) was visualized as dark smears similar to previous studies. 3. Areas of roughening (Mode-1 & Mode-2) exhibited significantly higher surface roughness than areas without such damage (Table 2). When comparing wettability, the contact angle for alumina (32.8°) was lower than CoCr (54.5°) and both materials had significantly higher contact angles with increased surface roughness. Conclusions:. Damage mechanisms leading to Mode-1 and Mode-2 wear were visualized on both metal and ceramic heads, leading to significant increases in surface roughness. However, the surface morphology of each damage mode differed between material types (Figure 3). These results, along with the empirical evidence relating surface roughness and wettability, have implications for wear and the ability to maintain suitable fluid films between bearing surfaces. Continued investigation into clinical phenomena possibly related to these parameters, such as squeaking in ceramic-on-ceramic bearings. 4. or accelerated wear in metal-on-metal bearings,. 5. is warranted

Aim. The purpose of this study was to perform a randomised controlled trial (RCT) to compare the >20 year outcomes of cemented versus cementless Mallory Head total hip replacements (THRs). Methods. Two hundred and fifty patients with unilateral osteoarthritis of their hip, a mean age of 64 years and 48% of whom were female were randomised to receive either a cemented (n=124) or cementless (n=126) THR. Results. At >20 years follow-up, the cementless Mallory Head THR outperformed its cemented counterpart in terms of overall Kaplan Meier survivorship (p=0.01), socket survivorship (p=0.009) and stem survivorship (p< 0.0001). Age significantly affected acetabular socket revision rates for both cementless (>65 - 12% versus < 65 - 36%, p=0.003) and cemented (>65 - 19% versus < 65 - 55%, p< 0.0001) sockets. Male gender adversely affected cementless (males - 31% versus females - 12%, p=0.01), but not cemented (males - 35% versus females - 36%, p=1.000) socket survivorships. For the femoral stems, age did not affect cementless stem survivorship (>65 - 0% versus < 65 - 2%, p=0.465), but did so with cemented stems (>65 - 16% versus < 65 - 33%, p=0.001). Gender did not influence cementless or cemented stem survivorships. Conclusion. This RCT has demonstrated that cementless THRs offer significantly better overall, socket and stem survivorships at 20 or more years. The cementless tapered femoral stem performed particularly well with 100% survivorship at 20 years, excluding infections. Caution should be taken in generalising these results to other cemented and cementless THRs

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

Introduction. The first highly crosslinked and melted polyethylene acetabular component for use in total hip arthroplasty was implanted in 1998. Numerous publications have reported reduced wear rates and a reduction in particle induced peri-prosthetic osteolysis at short to mid-term follow-up. 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 32mm femoral heads or less at a minimum of 13 years follow-up. Methods. Inclusion criteria for patients was a primary THR with femoral heads 32mm or less and a minimum 13 year follow-up. 139 hips have been enrolled with an average follow-up of 13.7 years (13–16), 80 females (57%). 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 0.006±0.033mm/yr. Using the early to latest film method, the wear rate was 0.003±0.056mm/yr. Radiographic analysis: Acetabular side: the greatest incidence of radiolucency occurred in zone 1 at 21%; sclerotic lines had a less than 2% incidence in any of the 3 zones; there was no identified osteolysis. Femoral side: the incidence of radiolucencies was limited to zone 1, 2%; 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 13 year follow-up and there was no identified osteolysis

Manual postoperative CT calculation of anteversion and inclination of the acetabular cup can be inaccurate and depends on the observer's experience. The aim of this study is to describe and present a validation of a new CT-image-based dedicate software (EGIT) for calculation of the acetabular component placement. The software principle is based on a three-dimensional reconstruction of a patient's bones from anatomical data collected postoperatively on the patient's CT scan. 15 Patient to be operated for THR were enrolled in this study. All patients were evaluated with post operative CT-scan. Measurement of Cup positioning were performed with two different methods: a manual method, performed by an expert radiologist, and a software CT image based method. Statistical analysis was performed with Intraclass Correlation Coefficent to asses interobserver and intraobserver reliability. A paired T-test was used to detect differences between manual and software methods. The Intraclass Correlation Coefficient was excellent for both the intraobserver and interobserver reliability. As expected the ICC is higher in the interobserver case. A mean cup anteversion of 14.2 (S.D. ±6.9), mean inclination of 44.2 (S.D.± 5.8) are detected with EGIT by the expert surgeon; Mean Cup anteversion of 13.6 (S.D. ± 5.11), mean inclination of 43.3 (S.D.± 5.1) are detected with manual method by expert radiologist. No statistical difference have been found (P> 0.05). The EGIT software seems to be an easy, accurate and reproducible method to calculate acetabular cup positioning using standard post-operative CT scan in THA

Introduction. Silicon nitride (SiN) is a recently introduced bearing material for THR that has shown potential in its bulk form and as a coating material on cobalt-chromium (CoCr) substrates. Previous studies have shown that SiN has low friction characteristics, low wear rates and high mechanical strength. Moreover, it has been shown to have osseointegration properties. However, there is limited evidence to support its biocompatibility as an implant material. The aim of this study was to investigate the responses of peripheral blood mononuclear cells (PBMNCs) isolated from healthy human volunteers and U937 human histiocytes (U937s) to SiN nanoparticles and CoCr wear particles. Methods. SiN nanopowder (<50nm, Sigma UK) and CoCr wear particles (nanoscale, generated in a multidirectional pin-on-plate reciprocator) were heat-treated for 4 h at 180°C and dispersed by sonication for 10 min prior to their use in cell culture experiments. Whole peripheral blood was collected from healthy donors (ethics approval BIOSCI 10–108, University of Leeds). The PBMNCs were isolated using Lymphoprep® as a density gradient medium and incubated for 24 h in 5% (v/v) CO2at 37°C to allow attachment of mononuclear phagocytes. SiN and CoCr particles were then added to the phagocytes at a volume concentration of 50 µm3 particles per cell and cultured for 24 h in RPMI-1640 culture medium in 5% (v/v) CO2 at 37°C. Cells alone were used as a negative control and lipopolysaccharide (LPS; 200ng/ml) was used as a positive control. Cell viability was measured after 24 h by ATPLite assay and tumour necrosis factor alpha (TNF-α) release was measured by sandwich ELISA. U937s were co-cultured with SiN and CoCr particles at doses of 0.05, 0.5, 5 and 50 µm3 particles per cell for 24h in 5% (v/v) CO2 at 37 C. Cells alone were used as a negative control and camptothecin (2 µg/ml) was used as a positive control. Cell viability was measured after 0, 1, 3, 6 and 9 days. Results from cell viability assays and TNF-α response were expressed as mean ±95% confidence limits and the data was analysed using one-way ANOVA and Tukey-Kramer post-hoc analysis. Results and Discussion. At a high volume concentration of particles (50µm3 per cell), SiN did not affect the viability of PBMNCs, while CoCr significantly reduced the viability over a 24 h period [Figure 1A]. Similarly, SiN particles had no effect on the viability of U937s up to 9 days with a range of particle doses (0.05–50 µm3 per cell) [Figure 2A]. In contrast, CoCr particles significantly reduced the viability of U937s after 6 days [Figure 2B]. Additionally, CoCr particles caused significantly elevated levels of pro-inflammatory cytokine TNF-α, whereas no inflammation was associated with SiN particles [Figure 1B]. Conclusion. This study has demonstrated the in-vitro biocompatibility of SiN nanoparticles. Therefore, SiN is a promising orthopaedic bearing material not only due to its suitable mechanical and tribological properties, but also due to its biocompatibility. Acknowledgements. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. GA-310477 LifeLongJoints

This is a minimum 15 year follow up of a cohort of 58 patients (30 men and 28 women) who underwent 62 non-cemented THR between 1998–2000 (54 unilateral, 4 bilateral), in whom an off-the-shelf “lateral flare” femoral component was implanted. These surgeries were performed by a single surgeon and have been followed continuously by that same surgeon. The mean age at the time of surgery was 60.4 yrs (52–74). There were no exclusions for osteoporosis or type “C” femoral geometry. Although some patients have deceased during these 15 years, there have been no stem failures, revisions or impending stem revisions at the time of follow up or at the time of death in those who have passed. Two patients have undergone revision of their acetabular liner for poly wear. There have been no complaints of thigh pain; and like the results seen in other series employing this stem design, there has been no evidence of bone loss due to stress shielding or subsidence of the femoral component in any of these patients. This mid-term follow up re-affirms the dynamic tension band model of hip biomechanics, upon which the “lateral flare” design is predicated. This model predicts that the proximal lateral femur can experience compression during the gait cycle and as such can be utilized as an additional base of support upon which the femoral component can rest. Rather than relying upon a traditional “press fit” technique to achieve initial implant stability, a technique which is highly dependent upon femoral geometry, bone quality and may risk fracture on implant seating, the “lateral flare” design permits a gentler, safer and more physiologic means of achieving initial implant stability necessary for osseous integration to occur. This alterantive terchnique has been termed a “rest fit”

Introduction:. Total Hip Replacement (THR) is a proven and effective surgical procedure. One of the main limiting factors of the longevity of THR is the performance of the bearing surface. The optimum bearing surface choice, however, remains controversial. We wanted to understand what influenced the choice of bearing surfaces amongst South African orthopaedic surgeons. We also wanted to know if there was any consensus between surgeons and the orthopaedic trade. Aims, material and methods:. There is no epidemiological registry-based data available in South Africa in respect of bearing surfaces used in hip replacements. We sent out an electronic survey to all members of the South African Orthopaedic Association as well as to trade representatives. Patient parameters influencing the choice of bearing surfaces were surveyed and these included age, gender, level of activity and diagnosis. We used a regressional and tree analysis methodology to interpret the results. Results:. We received 133 responses from orthopaedic surgeons. There were no differences in decision making and bearing surface choices according to the surgeon's experience, type of practice or fellowship training. It was statistically significant that age was the first and most important factor when deciding upon a bearing surface. The patient's activity level then played a secondary role in the final choice. We show that gender and clinical diagnosis played no significant part in decision-making. Ceramic-on-ceramic combinations were used most commonly in younger patients and metal-on-polyethylene in older patients. 73% of surgeons chose metal-on-polyethylene in patients older than 70 years. There were no surgeons who selected metal-on-metal or ceramic-on-metal combinations for any patients. Metal-on-polyethylene was the first choice in 51% of patients with a low-activity level and 23% of those patients with a high level of activity. Ceramic-on-ceramic and ceramic-on-polyethylene was the first choice in patients with a high level of activity by 32% and 34% of surgeons respectively. We received 51 responses from the trade representatives surveyed. There was no difference between the surgeons and the trade representatives in respect of their decision making when advising on bearing surfaces to be used in specific patients. Conclusion:. While each bearing surface combination has advantages and disadvantages we have demonstrated the rationale behind the decision making and the current trends in choices of bearing surfaces by South African orthopaedic surgeons. We note that our surgeon's choices are in line with international trends, especially in respect of metal containing bearing surfaces. We have also shown that the orthopaedic trade representative's guidelines are in keeping with those of the profession

Introduction. Many tests have been published which measure frictional torque [1–4] in THR. However, different test procedures were used in those studies. The purpose of this study was to determine the effect of test setup on the measured friction torque values. Methods. Specimen Description Table 1 lists tested study groups (n≥3). Metal-on-Metal specimens were custom designed and manufactured, and are not approved for clinical use. The remaining groups consisted of commercially available products (Stryker Orthopaedics, NJ). Test Model – A. A 50 mm outer diameter (OD), Solid-Back Trident PSL shell (Stryker Orthopaedics, NJ) was assembled into a test block and the Ti6Al4V trunnion was oriented parallel to the central axis of the articulating surface [Fig. 1]. A 2450N axial load was applied. The head underwent angular displacement of ± 20° about the central axis of the shell. Test Model – B. The same shell and block as in Test Model A were used but positioned to simulate a 50° abduction angle [Fig. 1]. A Ti6Al4V trunnion was oriented to simulate a 130° neck angle. A 2450N side load was applied and the head underwent angular displacement of ± 20° about the central axis of the shell. Test Model – C. A 54 mm OD, Solid-Back Trident PSL shell was assembled into a hip simulator and oriented with a 50° abduction angle [Fig. 1]. The head was assembled onto a stainless steel trunnion and oriented with a 130° neck angle. The load was held at 2450N and the shell underwent a ± 23° biaxial rocking motion. All tests were conducted in a lubricated environment, using 25% bovine serum. Test Models A & B yielded a maximum static torque that was defined as the peak torque observed when the velocity of the femoral head approaches zero and the head changes direction. Test Model C exhibits continuous motion and yielded a maximum dynamic torque value. Test models were statistically compared using a single-factor ANOVA test and a Tukey post-hoc test at 95% confidence level. Results. Sample group results, see Table 2, were compared between test models and it was found each model yielded significantly different (p < 0.05) values. Except for the 28 mm-SXL group where there was no significant difference between test models A & C. Discussion. Each test method yielded unique results, as highlighted by the large difference seen between static and dynamic torque values given by test models B and C. Although, test model B yielded significantly greater static torque, further analysis of raw data indicated equivalent dynamic torque values when compared to model C. Additionally, the test methods did not consistently rank test groups. Two of the three tests showed similar torques when comparing the conventional and SXL materials, while the third model found a significant difference between the two groups. Results demonstrate that careful attention must be applied when selecting a test model

Blood donation in England is voluntary and a limited resource. Blood transfusion is essential and beneficial in some postoperative hip replacements, however is not without inherent risks. Royal College of Physician audit in 2007 has shown wide variation in transfusion with an average rate of 25% (22% – 97%).

Patient blood management is an established approach to optimising need for post- operative transfusion. The Surgical Blood Conservation Service (SBCS) was set up in 2009 to enable a reduction in the demand for blood transfusion during and postoperatively in many orthopaedic procedures.

We aimed to achieve preoperative haemoglobin of 12g/dl (males) and 11g/dl (females). Low levels were treated with iron therapy. Surgery was deferred till satisfactory Hb levels were reached. During surgery cell salvage was routinely used. Transfusion was recommended at postoperative Hb < 8g/dl.

The transfusion rate was estimated at 47% in 2002. Following the introduction of SCBS, the transfusion rate reduced considerably to 7.9% in 2009 with a further reduction to 7.29% in 2011 and 3.16% in 2012. In 2013, 10 out of 442 hip replacements received transfusion (2.21%).

Our results demonstrate successful Patient blood management, minimising the need for post- operative transfusion.