Aims. Radiostereometric analysis (RSA) is the most accurate radiological method to measure in vivo wear of highly cross-linked polyethylene (XLPE) acetabular components. We have previously reported very low wear rates for a sequentially irradiated and annealed X3 XLPE liner (Stryker Orthopaedics, USA) when used in conjunction with a 32 mm femoral heads at ten-year follow-up. Only two studies have reported the long-term wear rate of X3 liners used in conjunction with larger heads using plain radiographs which have poor sensitivity. The aim of this study was to measure the ten-year wear of thin X3 XLPE liners against larger 36 or 40 mm articulations with RSA. Methods. We prospectively reviewed 19 patients who underwent primary cementless THA with the XLPE acetabular liner (X3) and a 36 or 40 mm femoral head with a resultant liner thickness of at least 5.8 mm. RSA radiographs at one week, six months, and one, two, five, and ten years postoperatively and femoral head penetration within the acetabular component were measured with UmRSA software. Of the initial 19 patients, 12 were available at the ten-year time point. Results. The median proximal, 2D, and 3D wear rates calculated between one and ten years were all less than 0.005 mm/year, with no patient recording a proximal wear rate of more than 0.021 mm/year. Importantly, there was no increase in the wear rate between five and ten years. Conclusion. The very low wear rate of X3 XLPE liners with larger articulations remains encouraging for the future clinical performance of this material. Cite this article: Bone Jt Open 2023;4(11):839–845

Aims. Adverse spinal motion or balance (spine mobility) and adverse pelvic mobility, in combination, are often referred to as adverse spinopelvic mobility (SPM). A stiff lumbar spine, large posterior standing pelvic tilt, and severe sagittal spinal deformity have been identified as risk factors for increased hip instability. Adverse SPM can create functional malposition of the acetabular components and hence is an instability risk. Adverse pelvic mobility is often, but not always, associated with abnormal spinal motion parameters. Dislocation rates for dual-mobility articulations (DMAs) have been reported to be between 0% and 1.1%. The aim of this study was to determine the early survivorship from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) of patients with adverse SPM who received a DMA. Methods. A multicentre study was performed using data from 227 patients undergoing primary total hip arthroplasty (THA), enrolled consecutively. All the patients who had one or more adverse spine or pelvic mobility parameter had a DMA inserted at the time of their surgery. The mean age was 76 years (22 to 93) and 63% were female (n = 145). At a mean of 14 months (5 to 31) postoperatively, the AOANJRR was analyzed for follow-up information. Reasons for revision and types of revision were identified. Results. The AOANJRR reported two revisions: one due to infection, and the second due to femoral component loosening. No revisions for dislocation were reported. One patient died with the prosthesis in situ. Kaplan-Meier survival rate was 99.1% (95% confidence interval 98.3 to 100) at 14 months (number at risk 104). Conclusion. In our cohort of patients undergoing primary THA with one or more factor associated with adverse SPM, DM bearings conferred stability at two years’ follow-up. Cite this article: Bone Joint J 2022;104-B(7):820–825

Purpose. The results of ceramic-on-ceramic (CoC) bearing surfaces in primary total hip arthroplasty (THA) were well known. However, it was not known in revision THA. The purpose of this study is to report the results of revision THA with ceramic articulation. Materials and Methods. 112 revision THAs with ceramic articulation were evaluated. The mean age at the time of surgery was 58.3 years (28 to 97). The mean duration of the follow-up periods was 6.4 years (2 to 11.8 years). Results. The Harris hip scores improved from an average of 79.0 at the index surgery to an average of 91.1 at the last follow-up. (P<0.001) None of hips showed osteolysis or ceramic head fracture. One hip shows aseptic loosening in the acetabular components with squeaking that caused a re-revision. There were nine cases of dislocation. The overall survival rate of the implants was 85.1% (95% confidence interval, 61.7% to 94.0%) at ten years with revision for any reason as the end point. Conclusion. The ceramic articulation is one of good bearing options for revision THA in patients with a long life expectancy

Late aseptic loosening of total hip arthroplasty (THA) components due to wear debris especially sub-micron Polyethylene induced osteolysis has been identified to be the major cause for revision. Therefore, the use of wear resistant designs and materials is imperative for the long-term success of articulating implants. One of the most promising articulations for THA regarding extremely low wear is the hard-on-hard Alumina/Alumina combination with a long history in orthopaedics accumulating to now 30 years of experience. Alumina Ceramic: Aluminum-Oxide Ceramic (Alumina, Al2O3, ISO 6474) is an extremely hard material that can only be scratched and also machined and polished by diamond. It has excellent mechanical properties but is brittle as are most ceramic materials and can, therefore, not be used for highly stressed implants like an artificial hip joint stem. Due to its ionic structure it is hydrophilic allowing liquids to bound to and lubricate its surface. Alumina’s hardness allows a polishing to a low roughness, which is entirely inverse and therefore able to create lubricating “pools.”. Density, purity and grain size in combination with an optimised manufacturing process are crucial for the final properties of Alumina and have been sub-optimal at the early pioneering times. Also the design has to be adapted to the critical properties of this ceramic. The biological activity of Alumina is graded as bio-inert and no direct osteointegration is to be expected, also proven by clinical experience. Alpha Alumina is bio-stable and practically insoluble in the body environment. Therefore, ageing or any systemic reaction in the human body with this ceramic is of no concern. First Generation Alumina Ceramic: Boutin has introduced Alumina ceramic components for articulation with itself for THA in 1970, followed by Mittelmeier and other surgeons. First reports of its combination with UHMWPE cups date back to 1972. More than one million Alumina heads have been worldwide implanted since then. Problems regarding fracture of the head were mostly encountered with collared heads of one design and the cup (especially if placed at > 50 deg abduction position). Run-away wear in case of edge contact have been reported with these first generation implants. A comprehensive retrieval study using a systematic analysis of two different designs confirmed that Alumina/ Alumina couples have a low clinical wear rate and identified the main risk factors that can lead to early failure of such devices. The wear rate of those historic Alumina / Alumina articulations is in the range of less than 5 microns per year. This is one to two orders of magnitude less than for any articulation with Polyethylene cups. Reaction to Alumina wear particles, mostly encountered on catastrophic failure of the historic implant designs is sparse and mostly benign. Third Generation Alumina Ceramic: Significant improvements in material properties and quality have been made since its introduction. The third generation of Alumina has been introduced in 1994 and was a further evolution regarding material properties, manufacturing, quality control and design. Refinement of purity, grain size and manufacturing results in improved fracture and also wear resistance, which decreased from low to almost immeasurable values. With the evolution of this new generation ceramic the problems of the past have been successfully addressed. Following improvements are characteristic for a third generation Alumina:. Improved purity and reduced grain size (Figure 1) for better properties. Improved density, HIP for enhanced toughness and bending strength. Less stress raisers due to laser marking instead of mechanical engraving. Optimised head internal geometry. Rounded and polished rim for risk reduction of runaway wear on sub-luxation. Improved safety due to 100% proof test on heads and inserts. These improvements result in a significant increase in mechanical properties. The risk of head fracture has been reduced for this 3rd generation Alumina ceramic heads from 1 per 500 (0.2%) to 1 per 25 000 (0.025%). The wear resistance of the couple Alumina/Alumina has also been enhanced which was measured in simulator tests to be around 1 micron per year. Tribological investigation involved a series of screening, pendulum and anatomical hip simulator tests with actual Alumina/ Alumina components in respect to the effect of clearance and cup angle (45° & 60°) in a series of tests for up to 5 million cycles. Adverse testing conditions for Alumina e.g. dilution of lubricant, dry and water, high load in swing phase, stop-start, etc in ascending aggressiveness (each at 1 million cycles) have also been investigated. No significant difference in wear volume was found comparing clearance or cup angle for all components tested. A new simulator test set up using a microseparation mode during every single cycle was also run for 5 million cycles combining Alumina from one single manufacturer and also mixing Alumina’s from different manufacturers. The wear in all cases was low and lower than for the first generation Alumina’s. A series of implantations with Alumina/Alumina articulation has been performed since November 1996 according to a prospective multicentric FDA IDE protocol comparing the same implant with CoCr metal heads/PE combinations. Short-term results demonstrate no early complications with this third generation Alumina/Alumina articulation if implanted correctly. The benefit of the dramatically reduced wear rate will show only after longer-term follow-up. Conclusion: Alumina/Alumina articulation demonstrates the lowest wear rate of all available material combinations for THA in the laboratory as well as in clinical praxis. The bulk material as well as its particles is bio-inert, therefore, giving no concern for adverse biological reactions. Problems with earlier designs of Alumina/Alumina articulation have been successfully addressed by taking the identified risk parameters into consideration. Components of the third generation Alumina ceramic and design have been extensively tested. All components pass the mechanical tests. Alumina heads and liners of the third generation in the size and under the conditions tested are safe and efficient. Their wear rate even under the influence of adverse condition is minimal. Further clinical trials parallel the application of this superior articulation couple in an innovative and modern design.Alumina/Alumina is, therefore, the material combination of choice for the active patient with high life expectancy

Repeated trauma to the radial head may be one of the causative factors in the genesis of osteochondritis dissecans of the capitellum. We measured the force, contact area and pressure across the radiocapitellar articulation of the elbow before and after radial shortening osteotomy in five fresh-frozen cadaver upper limbs with loads of 45, 90 and 135 N, respectively. Measurements were made on pressure-sensitive film placed in the radiocapitellar articulation with the forearm in the supinated, neutral and pronated positions before and after radial shortening. Radial shortening significantly reduced the mean force and contact area across the radiocapitellar articulation in all positions of the forearm

Early revision is an important risk factor for repeated revision and poor results after primary total hip replacement and instability is a major cause of early revision. Larger articulations with cross-linked polyethylene are proposed as a solution, but these are not without risk, including fracture of the thin polyethylene rim of the liner. The aim of our study was to examine implant-related revisions among primary total hip replacement patients with up to six year follow-up in a randomized controlled trial which compared 28 mm and 36 mm metal on highly cross-linked polyethylene articulations in total hip replacement. 557 patients undergoing primary total hip replacement were included in this study. Risk factors for dislocation and wear were controlled by stratification and patients were then randomized intra-operatively to either a 28 or 36 mm articulation. To date, 10 hips have been revised for implant-related problems following primary total hip replacement. Seven hips with a 28 mm articulation were revised to a larger articulation because of instability. Four of these were for recurrent dislocation, one for an irreduceable first dislocation and two for subluxation. In contrast, only one patient who had undergone total hip replacement with a 36 mm articulation was revised for recurrent dislocation. One hip with a 36 mm articulation in a well-positioned cup was revised to a 32 mm articulation because of elevated lip liner fracture. Another 36 mm articulation hip was revised for acetabular component loosening. This study shows that a 36 mm metal on highly cross-linked polyethylene articulation reduces the need for early revision for instability after primary total hip replacement. However, these benefits need to be weighed against the potential risks associated with these articulations, including rare fracture of the relatively thin poly-ethylene liner

Background: Metal on metal articulation is known to reduce wear and subsequent development of osteolysis. However, long-term results of THA using metal on metal articulation is not well validated, especially in young patients. Methods: Ninety-three THA were performed in 78 patients who were younger than 50 years of age at index surgery. The mean age of the patients was 37 years old. One patient (1 hip) had had a resection arthroplasty due to deep infection, 1 patient (1 hip) had performed stem revision because of periprosthetic fracture and 2 patients died before ten years follow-up and were excluded. Five patients (5 hips) were lost to follow-up before 10 years. Sixty-nine patients (84 hips) were available for complete clinical and radiographic analysis after minimum 10 years follow-up(range, 10 – 14 years). Results: The mean preoperative Harris hip score of 49 points improved to 92 points at the time of last follow-up. Twenty hips(21.5%) showed variable degrees of osteolysis. Three patients underwent revision surgery because of focal pelvic osteolysis in one, aseptic loosening with extensive pelvic osteolysis of acetabular component in two. Three subsidence of femoral stem in other patients were identified. Conclusions: At a minimum 10 years after THA using metal-on-metal articulation, it showed good results with regard to aseptic loosening in this group of young patients. However, relatively high rate of osteolysis in this articulation remains problematic and needs further investigation

The anatomy of the first metatarsophalangeal (MTP) joint and, in particular, the metatarsosesamoid articulation remains poorly understood. Its effect on sesamoid function and the pathomechanics of this joint have not been described. Fresh frozen cadaveric specimens without evidence of forefoot deformity were dissected to assess the articulating surfaces throughout a normal range of motion. The dissections were digitally reconstructed in various positions of dorsiflexion and plantarflexion using a MicroScribe, enabling quantitative analyses in a virtual 3D environment. In 75% of specimens, there was some degree of chondral loss within the metatarsosesamoid articulation. The metatarsal surface was more commonly affected. These changes most frequently involved the tibial metatarsosesamoid joint. The tibial sesamoid had an average excursion of 14.2 mm in the sagittal plane when the 1st MTP joint was moved from 10 degrees of plantarflexion to 60 degrees of dorsiflexion; the average excursion of the fibular sesamoid was 8.7 mm. The sesamoids also move in a medial to lateral fashion when the joint was dorsiflexed. The excursion of the tibial sesamoid was 2.8 mm when the joint was maximally dorsiflexed while that of the fibular sesamoid was 3.2 mm. There appears to be differential tracking of the hallucal sesamoids. The tibial sesamoid has comparatively increased longitudinal excursion whilst the fibular sesamoid has comparatively greater lateral excursion. This greater excursion of the tibial sesamoid could explain the higher incidence of sesamoiditis in this bone. The differential excursion of the 2 metatarsosesamoid articulations is also a factor that should be considered in the design and mechanics of an effective hallux MTP joint arthroplasty

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: Total hip replacements (THR) with the first generation metal-on-metal articulation were abandoned in 1970s in favour of metal-on-polyethylene articulation. Osteolysis due to polyethylene wear particles renewed the interest in metal-on-metal articulations. The second generation had improved clearance, metal hardness and reproducible surfaces. We describe the 10-year outcome of 63 THR with Metasul metal-on-metal articulation. Methods: From 1995 to 1996, 86 patients (90 hips) underwent THR with Metasul articulation and cemented CF-30 femoral stem. Of these, 55 hips had a cemented Stuhmer-Weber-Allopro cup and 35 hips had an uncemented Allofit cup. Eleven patients (12 hips) died and five patients (6 hips) were not available for clinical evaluation. However all had been contacted and it was known that the hip was not painful and had not been revised. Nine patients were lost to follow up. Thirty nine hips in cemented group and 24 hips in uncemented group had clinical, radiological and Oxford hip score (OHS) at minimum of 10-years follow-up after the operation. Results: The minimum length of follow up was 10-years with an average of 10.8 years. The average OHS at 10 years for the cemented group was 23 (range 12 – 42) and for the hybrid group was 20.3 (range 12 – 37). Five out of 63 (8%) hips had revision surgery. Two revisions (3%) were performed because of infection, 1 was revised (1.5%) because of unexplained pain and suspected metallosis and 2 were revised (3%) for suspected aseptic acetabular cup loosening. Conclusion: In comparison with the outcome of first generation metal-on-metal bearing, the hips in our study had lower rate of revision due to acetabular wear and loosening. This is the first study to show that the Metasul articulation has good outcome over a 10-year period. The survivorship is 97% with aseptic loosening as the endpoint for revision surgery

Background. The anatomy of the human knee is very different than the tibiofemoral surface geometry of most modern total knee replacements (TKRs). Many TKRs are designed with simplified articulating surfaces that are mediolaterally symmetrical, resulting in non-natural patterns of motion of the knee joint [1]. Recent orthopaedic trends portray a shift away from basic tibiofemoral geometry towards designs which better replicate natural knee kinematics by adding constraint to the medial condyle and decreasing constraint on the lateral condyle [2]. A recent design concept has paired this theory with the concept of guided kinematic motion throughout the flexion range [3]. The purpose of this study was to validate the kinematic pattern of motion of the surface-guided knee concept through in vitro, mechanical testing. Methods. Prototypes of the surface-guided knee implant were manufactured using cobalt chromium alloy (femoral component) and ultra-high molecular weight polyethylene (tibial component). The prototypes were installed in a force-controlled knee wear simulator (AMTI, Watertown, MA) to assess kinematic behavior of the tibiofemoral articulation (Figure 1). Axial joint load and knee flexion experienced during lunging and squatting exercises were extracted from literature and used as the primary inputs for the test. Anteroposterior and internal-external rotation of the implant components were left unconstrained so as to be passively driven by the tibiofemoral surface geometry. One hundred cycles of each exercise were performed on the simulator at 0.33 Hz using diluted bovine calf serum as the articular surface lubricant. Component motion and reaction force outputs were collected from the knee simulator and compared against the kinematic targets of the design in order to validate the surface-guided knee concept. Results. Under deep flexion conditions of up to 140° of squatting the surface-guided knee implants were found to undergo a maximum of 22.2° of tibial internal rotation and 20.4 mm of posterior rollback on the lateral condyle. Pivoting of the knee joint was centered about the highly congruent medial condyle which experienced only 1.6 mm of posterior rollback. Experimental results were within 2° (internal-external rotation) and 1 mm (anteroposterior translation) agreement with the design target throughout the applied exercises (Figure 2). Conclusion. The results of this test confirm that by combining a constrained medial condyle with guiding geometry on the lateral condyle, deep knee flexion activities of up to 140° can be performed while maintaining near-natural kinematics of the knee joint. The authors believe that the tested surface-guided implant concept is a significant step toward the development of novel TKR which allows a greater range of motion and could improve the quality of life for active patients undergoing knee replacement. For any figures or tables, please contact the authors directly

Introduction. Mobility at insert-tray articulations in mobile bearing knee implant accommodates lower cross-shear at polyethylene (PE) insert, which in turn reduces wear and delamination as well as decreasing constraint forces at implant-bone interfaces. Though, clinical studies disclosed damage due to wear has occurred at these mobile bearing articulations. The primary goal of this study is to investigate the effect of second articulations bearing mobility and surface friction at insert-tray interfaces to stress states at tibial post during deep flexion motion. Method & Analysis. Figure 1 shows the 3-D computational aided drawing model and finite element model of implant used in this study. LS-DYNA software was employed to develop the dynamic model. Four conditions of models were tested including fixed bearing, as well as models with coefficients of friction of 0.04, 0.10 and 0.15 at tibial-tray interfaces to represent healthy and with debris appearance. A pair of nonlinear springs was positioned both anteriorly and posteriorly to represent ligamentous constraint. The dynamic model was developed to perform position driven motion from 0° to 135° of flexion angle with 0°, 10° and 15° of tibial rotation. The prosthesis components were subjected with a deep squatting force. Results. Peak values of maximum shear stress for different coefficients of friction and fixed bearing, respectively, are shown in Figure 2. Peak value of maximum shear stress at tibial post of fixed bearing is significantly larger than mobile bearing with tibial rotation. The peak values are 63MPa and 46.7MPa with 10° and 15° tibial rotation respectively for fixed bearing while for mobile bearing the values range from 32MPa to 36.6MPa and from 35.3MPa to 40.6MPa with 10° and 15° tibial rotation respectively. It was found that peak value of maximum shear stress increases with coefficient of friction and tibial rotation. In contrast, with normal rotation, bearing mobility and surface friction do not give any significant effect on the shear stress at tibial post. Discussion & Conclusions. Appearance of second articulations in mobile bearing TKA provides an attribute in reducing force transmission via implant-bone interface which leads to lower shear stress induced in tibial post due to transmitted moment. However, higher surface friction will result in larger frictional force, which in turn induce larger moment at tibial post. Higher conformity will attribute to higher cross-shear level during knee motion. As a result, wear damage at tibiofemoral articular surface of mobile insert become worse

A ceramic is currently considered as the most ideal articulation in primary THA. The authors evaluated clinicoradiographic results and complications of cementless THA with 3rd generation of ceramic bearing. From April 2001 to January 2008, 310 primary THAs were performed in 300 patients using 3rd generation of ceramic bearing. In results, Harris hip score at last follow up was improved to an average of 95.4 points from 51.6 points preoperatively. In all cases, fixations around implants were stable and there was no osteolysis. Complications were dislocations, squeaking, ceramic femoral head and liner fracture. Our outcomes using cementless THA with 3rd generation of ceramic articulation were satisfactory, but more clinical study and investigation will be necessary to reduce complications

Osteolysis caused by polyethylene wear particles leads to loosening or bone destruction. Attempts to minimise wear rely largely on selection of the most suitable materials for the purpose. This is typically stainless steel, cobalt chromium or ceramic for the femoral head and primarily polyethylene on the acetabular side. However, there is increased use of both ceramic-on-ceramic and metal-on-metal articulations, particularly in younger patients, and of cross-linked polyethylene in the hip articulation. Emphasising material selection and development, this paper discusses possible future technical direction of the hip articulation

Aims: A polyethylene free, metal on metal acetabular system (Hofer-Imhof cup; Lubrimet metal on metal articulation made of CoCr-forge alloy) was designed in an effort to improve total hip arthroplasty longevity. This study was undertaken to review the clinical performance of this implant and to determine if acetabular loosening or revision and wear and osteolysis were prevalent. The long term results (mean follow up period 110 months) are presented in this study. Methods: In this prospective, randomized study a minimum of 90 months follow up results involving the first 100 implanted metal liner total hip arthroplasties are presented. The mean follow up was 110 months. Between April 1995 and November 1996 ninety-eight patients (100 hips) had a total hip replacement consisting of a titanium cementless self reaming, parabolic cup, a cementless titanium stem and the Lubrimet® metal on metal articulation. Two acetabular and one femoral component had to be revised due to aseptic loosening without showing macroscopic evidence of metallosis and no histological evidence of excessive metal wear. One patient hat to be revised by a complete change of the total hip (acetabular component and stem) showing histologic evidence of a metal induced hyperergic immunologic reaction. One patient presented with a broken neck of the stem and had to be revised by stem exchange. As a none device related orthopedic complication one acetabular component required revision surgery due to a periprosthetic fracture. Conclusions: The long term results of the Hofer-Imhof Lubrimet®Metal-on-metal articulation are satisfying and so the system represented a viable alternative for total hip arthroplasty in younger higher demand patients in the past. Due to the possible development of a hyperergic immunologic reaction to the metal on metal articulation and the availibility of a ceramic on ceramic articulation we do not implant this liner anymore

Aims: A polyethylene free, metal on metal acetabular system (Hofer-Imhof cup; Lubrimet¨ metal on metal articulation made of CoCr-forge alloy) was designed in an effort to improve total hip arthroplasty longevity. This study was undertaken to review the clinical performance of this implant and to determine if early ace-tabular loosening or revision and wear and osteolysis were prevalent. The mid term results (mean follow up period 62,7 months) are presented in this study. Methods: In this prospective, randomized study a minimum of 55 months follow up results involving the þrst 100 implanted metal liner total hip arthroplasties are presented. The mean follow up was 62,7 months. Between April 1995 and November 1996 ninety-eight patients (100 hips) had a total hip replacement consisting of a titanium cementless self reaming, parabolic cup, a cementless titanium stem and the Lubrimet¨ metal on metal articulation. 98 patients (100 hips) had complete clinical and radiographic data 55 to 89 months after the operation. One acetabular and one femoral component had to be revised due to aseptic loosening without showing macroscopic evidence of metallosis and no histological evidence of excessive metal wear. As a none device related orthopedic complication one acetabular component required revision surgery due to a peri-prosthetic fracture. Conclusions: The mid-term results of the Hofer-Imhof Lubrimet¨Metal-on-metal articulation are encouraging and so the system may represent a viable alternative for total hip arthroplasty in younger higher demand patients

Introduction. There is interest in minimally invasive solutions that reduce osteoarthritic symptoms and restore joint mobility in the early stages of cartilage degeneration or damage. The aim of the present study was to evaluate the Biolox®delta alumina-zirconia composite as a counterface for articulation against live cartilage in comparison to the clinically relevant CoCrMo alloy using a highly controlled in vitro ball-on-flat articulation bioreactor that has been shown to rank materials in accord with clinical experience. Methods. The four-station bioreactor was housed in an incubator. The dual axis concept of this simulator approximates the rolling-gliding kinematics of the joint. Twelve 32 mm alumina-zirconia composite femoral heads (Biolox®delta, CeramTec GmbH, Germany) and twelve 32 mm CoCrMo femoral heads (Peter Brehm GmbH, Germany) made up the testing groups. Each head articulated against a cartilage disk of 14 mm diam., harvested from six months old steers. Free-swelling control disks were obtained as well. Testing was conducted in Mini ITS medium for three hours daily over 10 days applying a load of 40 N (∼2 MPa). PG/GAG was determined using the dimethylmethylene blue (DMMB) assay. Hydroxyproline was analyzed by high performance liquid chromatography coupled to a mass spectrometer. Additionally, at test conclusion, chondrocyte survival was determined using Live/Dead assay. Histological analysis was performed using a modified Mankin score. The effect of articulating material (ceramic, CoCrMo) on the various outputs of interest was evaluated using ANOVA. Blocking was performed with respect to the animals. The Mankin scores were compared using the Kruskal–Wallis test. Results. Cells stayed alive during the course of the 3-week experiment with cell survival values close to or at 80% at test completion. There was no difference between ceramic and free swelling control tissue. However, cell count values were inferior for CoCrMo in the superficial zone (p= 0.003). Tested tissue suffered mostly structural abnormalities. In many samples, the superficial layer was disturbed (and sometimes absent), but deeper layers were little affected. The average Mankin scores were in the range of 2 (out of 14) for both materials (p=0.772; Fig. 1). PG/GAG content in medium was highest for CoCrMo (Fig. 2). Though despite a 10% difference between CoCrMo and ceramic, this did not manifest in statistical significance (p=0.315). Similarly, hydroxyproline release into medium was higher for CoCrMo than ceramic (Fig. 3). This difference (28%) was statistically significant (p=0.024). Discussion. Overall, the results indicate that ceramic-on-cartilage induces less tissue and cell damage than metal-on-cartilage. However, only the hydroxyproline measurements reached statistical significance, partially due to a large variation within both material groups. Current understanding of cartilage wear is still incomplete. While studies have utilized the coefficient of friction against artificial materials as a surrogate wear marker, the best way to determine wear in in-vitro experiments is not well-established. Here, we used the matrix components proteoglycan and hydroxyproline to predict cartilage damage, but further work is necessary to elucidate the mechanobiological reasons for damage. In summary, from this study, Biolox®delta ceramic is generally superior to CoCrMo in the articulation against hyaline cartilage. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction: Ceramic/ceramic articulation has a long history and is accepted as a low wear couple for total hip joint application. Due to the requirements for strength of the ball-head it may be necessary to combine products from different Alumina manufacturers. Material and methods: Alumina components according to ISO 6474 for commercial hip joint prosthesis were obtained from 3 sources and subjected to a series of simulator tests up to 5 million cycles. Variations were the type of testing and the quality and type of the Alumina. Wear tests were performed with two different types of simulators and different protocols also including micro-separation testing. Wear was characterised by weight loss, change in surface appearance and particle analysis. Results: Standard wear testing yielded very low wear rates below 0.5 mm3 per million cycles for the Alumina combinations of the third generation with a running in period and a steady state wear after 1 million cycles. Increasing the inclination of the cup up to 60° did not increase the wear rate. Mixing the components from various sources did not affect the wear rate significantly. Micro-separation testing increased the overall wear rate significantly and showed clinical relevant patterns with grain pullout and grain relieve. After a running in period a steady state without “avalanche” effect was observed again. The particle analysis compared favourably with retrieval studies. Although the wear rate was lower for the mixed couples it was statistically not significant. Conclusion: An improved test method for ceramics demonstrates clinically relevant wear in respect of amount, appearance and particle size. The new generation Alumina is more wear resistant and less sensitive to cup position and to micro-separation. Mixing of Alumina components from a single implant manufacturer does not change the low wear rates of ceramic/ceramic articulation and can, therefore, be applied

Introduction: There has been a renewed interest in metal-on-metal articulation in hip joint Arthroplasty. The reason for having metal-on-metal articulation is to reduce the volume of wear particles that are produced with THR. The outcome of reduced particle formation will hopefully be reduced osteolysis. Methods: We reviewed the results of 139 primary hip arthroplasties (130 patients) performed using Metasul articulation and cemented Weber cup. Six patients were lost to follow-up leaving 133 hips (124 patients) for review with at least 5-year follow-up. The acetabular socket was the cemented Weber cup and Bone grafting of the acetabulum and application of a reinforcement ring was done where necessary. Cemented CF-30 femoral stem was used in all patients but one (PFMR). The study was conducted retrospectively based on the information collected from hospital notes and Orthocom database. Immediate post-operative films were seen to measure the cup and stem inclination and quality of cementing using the Barracks grading system. Results: There were 102 females and 22 males in the cohort. Mean age was 73 years (SD-7.46, range 58–86). Left to right hip ratio was 52:81. Most common Pre-operative diagnosis was Osteoarthritis (103) followed by Intracapsular fracture neck of femur (20). The average follow-up was 7.23 years (range 5–10.9). Mean pre-operative Harris hip score was 42.09 and mean post-operative hip scores were 90.01, 86.84, 87.42 and 84.63 at 1-year, 3-year, 5-year and final follow-up with the corresponding pain scores were 42.9, 41.84, 41.56 and 41.56 respectively. Only two hips were revised for aseptic loosening of the cup with a 93.4% implant survivorship at 12 years. There was no case of aseptic stem loosening. No untoward systemic effects were noted in the cohort. Discussion: We believe that in our study Metasul metal-on-metal articulation has shown satisfactory results with regards to aseptic loosening and reduction in osteolysis in medium-term

Purpose. This study was undertaken to assess the result of total hip arthroplasty (THA) performed for fused hips. Patients and Methods. Twenty nine patients (31 hips), aged 21 to 70 years (average 46 years), underwent THA conversion surgery and were followed for an average of 4.6 years (2.4-12.0 years). There were 23 cases of spontaneous fusion and 8 case of surgical fusion. The causes of joint fusion were tuberculosis in 6 hips, childhood coxitis in 13, ankylosing spondylitis in 6 and childhood trauma in 4. Modified two incision technique was used in 9 hips and in 22 hips, the surgery was performed through a posterolateral approach combined with anterior capsulotomy through gluteus medius and tensor fasica lata interval. In 1 case, greater trochanter osteotomy was done. All acetabular components were inserted at the true acetabulum and the articulations were metal on metal in 7 cases and ceramic on ceramic in 24 cases. Postoperatively, range of motion exercises were encouraged after 2 to 3 weeks of bed rest and subsequent weight bearing crutch ambulation. Then active exercises were strongly encouraged to stretch abductors. We evaluated the clinical and radiological results. Results. Mean duration of surgery was 178.6 minutes, and mean perioperative blood loss was 1420.1 ml. Post-operative dislocation occurred in 1 case and partial femoral nerve palsy developed in 1 case. Mean Harris Hip Score improved from 42.4 to 84.2 and mean leg lengthening of 36.6 mm was achieved. Sitting cross legged was possible in 15 patients and except 2 patients, all patients were satisfied with the surgery. On the radiologic evaluation, there was no changes in cup position and there was one case with acetabular focal osteolysis. Postoperative dislocation occurred in one case and there was no revision surgery or infection. Conclusion. Our study suggest that THA performed for fused hips with hard bearing articulation can provide good clinical and radiological results in mid-term follow up