Introduction. Large wear rate reductions have been shown for crosslinked PE in simulators and short- to mid-term clinical wear studies. However, concerns persist about long-term in-vivo oxidation (especially with annealed PE), late accelerating wear and the possibly higher osteolytic potential of crosslinked PE particle debris. This is the first long-term study comparing conventional to crosslinked PE investigating whether the wear reduction is maintained in the long-term and if reduced osteolysis becomes evident. Materials & Methods. In a prospective study 48 primary THA patients (Stryker ABG-II, 28mm CoCr heads) were randomized to either receive a first generation crosslinked PE (Stryker Duration: 3MRad gamma irradiation in N2, annealed) or then conventional, now “historic” PE (3MRad gamma irradiation in air). Both groups were statistically non-different (p>0.1) regarding age (63.9 years), gender, BMI, stem and cup size, cup inclination, liner thickness or pre- and post-op HHS leaving the insert material as the only variable. Patients were followed-up annually using the Harris Hip score, AP and lateral radiographs and digital wear measurements using Roman V1.70 [1, 2]. Wear and radiographic signs of osteolysis were analysed at a mean follow-up of 12.9 years (12.0–13.3). Groups were compared using the t-test (means) or the Fisher Exact test (proportions). Results. Thirty-one patients (18 conventional, 13 Duration) were left for analysis (8 deaths, 9 lost to FU). At 13yrs the total linear head penetration was sign. lower with Duration (0.70 ±0.36mm, range: 0.3–1.2mm) than conventional PE (1.56 ±0.83, range: 0.4–3.3mm, p=0.015). Also the annual wear rate was sign. lower (p=0.005) for Duration (0.063 ±0.027mm/yr) than conventional PE (0.122 ±0.065mm/yr). This reduction (−48%) compared well to the original simulator prediction (−45%) and even increased with time (−30% at 5yrs, −38% at 8yrs, −42% at 10yrs). In the Duration group only 1 patient had a wear rate >0.1mm/yr (osteolysis threshold) compared to 10 in the Conventional group (p=0.007). Patients with radiographic signs of acetabular osteolysis (cysts) on the AP x-ray were less frequent in the Duration (4/13=31%) than in conventional group (13/18=72%, p=0.023). This difference became even more pronounced when also the lateral view was evaluated and the affected DeLee-Charnley zones were counted (7 vs 22, p=0.017). Only in the conventional group a revision was performed (cup for wear). Discussion & Conclusions. At long-term FU the absolute wear rate of Duration crosslinked PE did not increase but decrease and the wear relative reduction did not deteriorate but increased. The incidence of osteolysis was sign. less. Thus No clinical evidence of degradation or elevated osteolytic potential for this annealed first generation crosslinked PE debris was found

We present a series of four patients with what we have termed the snapping pes syndrome. This is a painful clicking and catching experienced at the posteromedial corner of the knee when moving from flexion to extension. Clinical examination and real time ultrasound are the most useful diagnostic tools. If medical treatment is unsuccessful surgical excision of both the semitendinous and gracilis tendons is indicated for relief of persistent symptoms

Several options for high demand/high activity patients for bearings in THA exist. Each of them faces certain known and unknown risks of failure. There is a remarked trend to bigger diameter heads to reduce the incidence of dislocation for such patients. While combinations with hard-on-hard bearings have been used in such incidences, a Polyethylene (PE) option is desirable due to its less sensitivity to edge loading and price. A highly crosslinked sequentially annealed PE of the 3rd generation was prepared by sequentially crosslinking with appropriate annealing steps with a cumulative dose of 90 kGy and subsequent gas plasma sterilization. The structure of this material was determined using TEM, DSC and SAXS. Free radicals and oxidation was determined by ESR and IR spectroscopy. Mechanical evaluation in the unaged and aged condition were performed by quasi-static, dynamic and functional dynamic tests in comparison with negative controls. Wear testing was performed by ball-on-plate tests and hip joint simulators. PE inserts of various internal diameters up to 44mm and thicknesses of 4-8mm in comparison with a historic inert gas irradiation sterilized PE as negative control. These tests have been carried out at 3 institutions using different set-up and protocols. To look at worst case scenarios the simulator testing was done in an impingement mode and fatigue tests of the thinnest components where performed in 2 different fatigue set-ups up to 10 million cycles. The structure and crystallinity of the sequentially crosslinked PE were comparable to the controls. The radical concentration was reduced by more than 95% due to the sequential process employed and consequently the oxidation level after artificially aging remained at the level of untreated PE. 5 year storage data confirmed the stability of this polymer. All mechanical testing revealed the maintenance of the properties at the same level as the controls. The screening wear test revealed that the high sliding stress used in this set-up had no effect on the sequentially crosslinked PE even when aged, while the controls showed fatigue wear after a short time of testing. The decrease in volumetric wear compared to a negative control (28 mm head size) was on average 90% in volumetric independent of the head size and thickness of the PE liner. This result was confirmed by the studies at 2 other institutions with a wear reduction of 86 and 95% respectively. Impingement increased the wear rate marginally, without causing any fractures or failures of the components. The analysis of the wear particles from the simulator studies showed a marked decrease in number with close similarity in appearance and morphology to that from the control tests. Fatigue testing even in a luxation model showed no negative effect on the impact on the rim after 10 million cycles also with the thinnest components. Highly crosslinked, sequentially annealed PE from the perspective of tribological and fatigue testing can be used safely even in impingement and luxation situations. Other factors in the clinical usage of thin liners may play a role and need to be investigated further

Purpose: Since 1962, when Sir John Charnley implanted the first total arthroplasty, long-term studies have demonstrated the excellent survival of these implants with greater than 85% survival at 25 years (John Older, Mike Wroblewski, ACORA group in 1995). Polyethylene wear is the main obstacle to long-term survival of the Charnley total hip arthroplasty. New friction surfaces have been proposed to reduce wear, notable the ceramic/ceramic junction proposed by Pierre Boutin since 1970 with the ceramic/polyethylene derivative. The alumine ceramic head cannot be greater than 22.225 cm due to the risk of fracture, leading to the zircone head. D. Goutallier and his school recently demonstrated (1999) that the use of zircone can increase wear with early development of osteolysis and acetabular loosening. For this reason, we compared wear between two series of prostheses using the 22.2 zircone/polyethylene combination versus the metal/polyethylene combination.

Material and methods: Two series of 37 patients were compared for wear. The first series included 41 hips with a zircone/polyethelene combination using a 22.2 cm head. The second series of 38 hips used a metal/polyethylene combination and 22.2 cm heads. The femoral components were the same in the two series with an 8/10 Morse cone. Mean follow-up in the two series was 38 months. All patients underwent surgery in 1997 for the zircone/polyethylene implants and in 1995 for the metal/polyethylene implants. Mean age in the zircone/polyethylene series was 58 years and in the metal/polyethylene series 66. The Postel Merle d’Aubigné (PMA) score at review was 16.6 for the zircone/polyethylene series and 17.7 for the metal/polyethylene series. Manual measurements of wear were made using the Livermore method with determination of the centre of the head according to Cherrot and Kerboull, doubled with computer-assisted interobserver radiological measurements.

Results: At three years, 31.5% of the metal/polyethylene implants were devoid of any signs of wear compared with 29.2% in the zircone/polyethylene implants. Mean wear was 0.19 per year for the metal/polyethylene implants versus 0.12 per year for the zircone/polyethylene implants. Overall wear on the AP view at last follow-up was 0.62 mm for the metal/polyethylene implants and 0.40 mm for the zircone/polyethylene implants at three years. This difference was significant p < à.005).

Discussion: We did not find any greater wear with the zircone/polyethylene combination compared with metal/polyethylene as was also demonstrated by D. Goutallier. M. Wroblewski (2000) demonstrated in a study with 10 years follow-up that wear was twice as great the first two years with a 22.225 diameter head using the alumine ceramic/polyethylene combination (0.1 mm per year), then stabilised. This was probably due to a stabilisation period. We are probably currently in this stabilisation period with the zircone/polyethylene implants.

To prevent aseptic loosening resulting from osteolysis induced by polyethylene (PE) wear particles in THA, it is necessary to develop a high wear-resistance bearing material. We have investigated the bearing surface mimicking the articular cartilage; grafting a biocompatible polymer, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), onto the PE surface. High wear-resistance of PMPC-grafted surface has been revealed in the hip simulator wear test of 20 million cycles. Additionaly, in THA, oxidation degradation induced by residual free radicals resulting from gamma-ray irradiation for cross-linking or sterilization is also regarded as serious issue. Recently, gas plasma (GP) sterilization has been used as a less residual radical sterilization method. In this study, we ask a question: the GP sterilization would affect to PMPC surface and/or PE substrate? Hence, we investigated surface chemical, wear, mechanical, physical and oxidation properties of GP sterilized PMPC-grafted highly cross-linked PE (CLPE). GP-sterilized CLPE and PMPC-grafted CLPE (CLPE (GP) and PMPC-CLPE (GP), respectively; GUR 1020 resin, 75 kGy irradiation), and 25 kGy-gamma-sterilized PMPC-grafted CLPE (PMPC-CLPE (g); GUR 1020 resin, 50 kGy irradiation) were evaluated. Surface property of PMPC layer was evaluated by X-ray photoelectron spectroscopy (XPS), fourier-transform infrared (FT-IR) spectroscopy, fluorescence microscope and cross-sectional transmission electron microscope (TEM) observations. Wettability and lubrication of the PMPC-CLPE surface were evaluated by static water contact angle measurement and ball-on-plate friction test, respectively. Wear properties of the acetabular cups were examined by using hip simulator in the combination with Co-Cr-Mo femoral heads. To evaluate the GP sterilization effect to the CLPE substrate, tensile test, izod impact test, small punch test, gel content, residual radical concentration and oxidation degradation were conducted. Oxidation degradation was evaluated as oxidation index by using a FT-IR spectroscopy. By the XPS and FT-IR measurements, phosphorus peak and P-O peak attributed to grafted PMPC were observed, respectively. Uniform PMPC layer (100–200 nm thick) was observed on both surfaces of PMPC-CLPE (g) and PMPC-CLPE (GP) [Fig. 1]. Water contact angle of CLPE (GP) was almost 100 degree, while those for PMPC-CLPE (g) and PMPC-CLPE (GP) decreased dramatically to almost 10 degree. Dynamic coefficient of friction of PMPC-CLPE (g) and PMPC-CLPE (GP) was lower than that for CLPE (GP). In the hip simulator wear test, PMPC-CLPE (g) and PMPC-CLPE (GP) cups showed significantly lower amount of wear than that of CLPE (GP) [Fig. 2]. The number of the wear particles was extremely less in PMPC-CLPE (g) and PMPC-CLPE (GP), though the size was not different of all cases. Water thin film might be formed at the grafted PMPC layer, which acted as significantly efficient lubricant. There was no difference in the mechanical and physical properties among three groups. Oxidation index for PMPC-CLPE (GP) after acceleration of aging was lower than that of PMPC-CLPE (g). The GP sterilization might affect only to the PMPC-grafted surface, whereas gamma irradiation affects also to the PE substrate. From these results, the PMPC-CLPE (GP) is expected to be one of the great bearing materials having not only high-wear resistance but also high-oxidation resistance, which could give further longevity of implantation

Aims: The purpose of this study was to determine the intra-subject repeatability of the motion pattern of the PE inlay in a mobile-bearing total knee replacement (TKR) with respect to the post-op time. Methods: 75 mobile-bearing TKRs in 73 patients were included in this prospective study. Sagittal radiographs at 0°, 30°, 60° and maximum flexion were taken 3, 12, and 24 months post-op. On each X-ray, the AP position and the rotation of the PE inlay with respect to the tibial baseplate were determined based on a 2D algorithm. The accuracy of the method was ± 0.2 mm for the AP position and ± 1.7° for the angle of rotation. To classify the repeatability, the mean AP and rotation motion with respect to the flexion angle for each patient was computed and the overall standard deviation (STD) of all measurements with respect to the mean curves was calculated. The repeatability was defined as ‘excellent’ if the STD in the AP direction was less than 0.5 mm and the STD in rotation was less than 2.5°. It was defined as ‘good’ if the STD in the AP direction was less than 1 mm and the STD in rotation was less than 5°. Results: 19 of 75 knees (25%) showed an excellent repeatability and 33 of 75 knees (44%) displayed a good repeatability of the PE motion. Motion patterns were more repeatable between the 12 and 24 month results than between the 3 and 12 month results. Conclusions: The majority of the mobile-bearing knees exhibited a repeatable, patient specific motion pattern of the PE inlay. The fact that the repeatability was higher between 12 and 24 months may be attributed to a more stable state after rehabilitation. Mobile-bearing knees support patient specific motion in contrary to constrained fixed bearing knees

Purpose: Ceramic/ceramic bearing surfaces have the advantage of significantly decreased wear and high biocompatibility compared to CoCr/PE or ceramic/PE. The purpose of this randomized, controlled, multi-center, prospective study was to evaluate the clinical and roentgenographic results of 469 ceramic/ceramic versus 321 ceramic/PE THA at a 2 to 7 year follow-up. Methods: The ceramic/ceramic THA had a polished alumina femoral head articulating with a polished alumina acetabular liner seated into the metal acetabular shell designed to avoid any impingement of the ceramic liner on the femoral component. Evaluations were completed preoperatively, at 6 months and yearly postoperatively. Results: Mean age of the 790 patients was 59 years, with slightly more females. There were no significant demographic differences between the two groups. The main diagnoses were OA in 74% and osteonecrosis in 19%. Preoperatively the mean Harris Hip Score (HHS) and WOMAC scores were 44 and 41, respectively, and did not differ significantly between the two groups. At follow-up, the mean HHS was 93 for the ceramic/ ceramic THA and 93 for the ceramic/PE THA. The mean WOMAC scores showed no differences at follow-up. Roentgenographic analysis revealed one acetabular cup migration with a PE liner. One ceramic liner fractured upon insertion that was not properly positioned prior to impaction. Otherwise, there were no revisions or complications related to either bearing surface. Conclusions: This short-term study has demonstrated efficacy and safety of a ceramic/ceramic bearing surface compared to the standard ceramic/PE surface currently used in clinical practice, with no failures or complications related to the bearing surface. Further follow-up is indicated to determine the long-term outcome. Funding: Commerical funding. Funding Parties: Encore Orthopaedics

Congenital convex pes valgus (congenital vertical talus) is a rare condition. We reviewed ten feet in seven patients who had had surgical correction. All had been operated on by the senior author (JF) and the same surgical technique was used throughout, incorporating transfer of the tibialis anterior to the neck of the talus. The mean age at surgery was 31 months and the mean follow-up was nine years (6 to 14). All patients completed a questionnaire and had clinical, radiological and photographic evaluation performed by an independent examiner. None had required further surgery. All but one were satisfied with the result, and had no functional limitations. They all wore normal shoes. The mean ankle dorsiflexion was 17° and plantar flexion 21°. The mean arc of subtalar motion was 27°. All radiological parameters measured were within the normal range, although irregularity of the talonavicular joint was common. No avascular necrosis of the body of the talus was seen. We conclude that the medium-term results of this procedure are very satisfactory

Femoral head roughening is a clinically observed phenomenon that is suspected to cause increased wear of acetabular inserts. Two approaches have been taken to reduce hip bearing wear. Improved femoral head materials may decrease the impact of roughening and reduce the effect of abrasion. Additionally, improved polyethylene materials may be utilized to reduce wear against smooth or roughened femoral heads. This study looks at these two approaches in the form of a toughened alumina femoral head (Biolox Delta) and a sequentially crosslinked and annealed polyethylene (X3). A wear study was performed with new and artificially scratched ceramic femoral heads (28mm Biolox Delta) as compared to new and artificially scratched Cobalt Chromium femoral heads. These femoral heads were articulated against both conventional (N2\Vac) and highly crosslinked (X3) polyethylene acetabular cups. Artificial scratching utilized a Rockwell C indentor loaded at 30N to scratch a multidirectional scratch pattern on the articulating surface of the femoral head to simulate in vivo roughening. Delta femoral heads exhibited superior resistance to scratching. Peak to valley roughness for CoCr heads was 7.1um while Delta heads only roughened to 0.4um. Head material under standard conditions (no scratch) had no effect on PE wear (p=0.31 and p=0.53). Under abrasive conditions, the Delta femoral head exhibited a clear advantage over CoCr heads (65–97% reduction in wear rate; p< 0.007). X3 polyethylene also showed a clear advantage over conventional PE against either CoCr or Delta heads and under both conditions (all p < 0.012). This study clearly demonstrates that X3 polyethylene has a clear wear advantage over conventional polyethylene despite head material or abrasive conditions. Secondary to the polyethylene choice, the use of a ceramic femoral head leads to superior performance under abrasive conditions

Introduction: The debris of standard Polyethylene in Total Hip Arthroplasty (THA) has been responsible for aseptic loosing and osteolysis in many patients. Wear rates for Polyethylene-Ceramic are analysed around 10 to 20 mm3 per year, those of PE-metal even 5 times more. Dislocation of primary THA is also common and problematic. Using a PE insert with a dorsal rim lowers the risk of dislocation but could be a potential risk for impingement if not correctly placed. Aim of this study was to value of reduced risk for dislocation in terms of increased risk for impingements. Study design: Between 1989 and 2003, 1107 non-cemented SL cups with Polyethylene on Ceramic were implanted in 953 patients, 422 (44%) implanted in women. All PE inserts were with dorsal rim. Average age at implantation was 69.9 years (range 39 to 90). In all cases, a cemented stem was implanted. Of those 1107 primary THA, 100 were revised for aseptic loosening. In 11 cases both components were revised, 7 times only the cup was replaced and for the 82 revisions remaining, only the stem was revised. In all cases the PE insert was removed and replaced. All inserts were analysed macroscopically for impingement and the volume worn off was calculated. Dislocation risk of PE couplings with rim was compared to standard PE couplings without rim. Results: In 18 PE inserts of 100 with rim, signs of impingement were found, ranging from slight (considered as creep not wear) to massive. An average yearly wear rate of 43 mm^3 (range 7 to 119) was calculated. Median survival time of the inserts without impingement was 5.2 years (range 0.7 to 11.4) of those with impingement it was reduced to 4.5 years (range 1.1 to 13.8). No statistical difference calculated (Mann-Whitney-U test, p=0.28) . In 2 of all 1107 cases (0.2%) operative revision of dislocation was performed whereas in 6 of the 598 cases (1%) with PE cups without rim, operative intervention was performed. Discussion: The use of a PE insert with dislocation protection rim holds a potential danger if not correctly placed. Though an earlier failing of THA with PE impingement was found, it was not significant and overpowered by the fact that most loosenings were due to cemented titanium stems with their great potential for early loosening

The introduction of ceramics in total hip arthroplasty contributed significantly to the wear reduction of poly-ethylene and in consequence reduced osteolysis and loosening. This great benefit has been demonstrated in several clinical observations. In a recent study from Norway, the wear of a 28mm alumina and a CrCo ball head against Ultra High Molecular Weight Polyethylene (UHMWPE) after 10 years is compared using the RSA method of wear measurement. It was concluded that the considerable reduced wear for ceramic ball heads in comparison to CrCo ball heads is a great advantage in hip arthroplasty. A first prospective, randomized study with a 15 years follow up has been presented recently in the EFORT 2009. The comparison of wear of polyethylene between alumina and metal ball head shows a reduction of 44% penetration (linear wear) with the alumina-polyethylene bearing surface. In order to offer improved mechanical resistance and tribological qualities than alumina whilst maintaining structural stability, a new generation of alumina matrix composite (BIOLOX. ®. delta) has been used in orthopedics since 2001. The topic of this study is to demonstrate the excellent wear performance of the alumina ceramic composite against polyethylene, compared to alumina/PE in vivo. Methods: The BIOLOX. ®. delta-PE bearing has been tested on a six station hip simulator (Endolob, Rosenheim) according to ISO/DIS 14242. The newborn calf serum was replaced every 0.5 million cycles and the test was stopped after 5 million cycles. Weight was measured using a high precision balance (Sartorius BP 211D). Results and Discussion: After 5 million cycles, the insert surface appeared polished with fine scratching on the whole contact area. The wear rates calculated by linear interpolation were 13,52 mg per million cycles. (Standard deviation 0,60). The wear rate measured for BIOLOX. ®. delta against UHMWPE was 13,52 mg per million cycles. In general, the wear rate can be regarded as small compared to other hip simulator tests using ceramic against polyethylene couplings. When comparing the results for BIOLOX. ®. forte on polyethylene with the same 28mm diameter and same testing parameter, we observed 26,57 +/− 3,55mg/million and 16,08+/−2,31 mg/million, respectively. The BIOLOX. ®. delta on UHMWPE bearing shows improved wear behavior with a much lower wear rate. Conclusion: This study demonstrates the very low in vitro wear of the Alumina ceramic composite on UHMPE compared to ball heads made of pure alumina. Based on this results and the clinical performance of the alumina-UHMPE bearing from the literature, we can expect a further reduction of wear for the BIOLOX. ®. delta on UHMWPE in vivo that will increase the survival rate of the total hip arthroplasty

The New Jersey Low Contact Stress prosthesis was introduced in 1977. LCS mobile bearing prostheses have been implanted in patients in the United States since 1985. The PCL-sacrificing rotating platform design of the LCS® prosthesis was designed to minimally constrain knee kinematics while minimising bone-cement-prosthesis interface stresses and polyethylene wear. The purpose of the current study was to assess the in vivo rotating platform PE wear of the LCS-RP® and to check if the PE tray mobility is preserved over time. We investigated 120 total knee replacements in 108 patients (38 men, 70 women) treated by the LCS-RP® prosthesis for osteoarthritis or rheumatoid arthritis. Average age of the patients was 70.4 years (range: 36–81). Average follow-up was 15.3 years (range: 10–18). PE wear assessment was performed using a specific analysis model created in the Imagika® software on AP radiographs. Rotating platform mobility was assessed thanks to another analysis model. We used prosthetic landmarks (tip of the prosthetic stem, tibial tray and tantalum markers embedded into the PE) visible on lateral radiographs. Linear wear rates were 0.012+/−0.007 mm (tibial plate/ PE interface), 0.026+/−0.034 mm (PE/internal condyle interface) and 0.017+/−0.041 mm (PE/external condyle interface). There were no significant differences between wear values of both internal and external sides of the upper surface of the PE insert (P = 0.000054) and of tibial plate PE/external condyle PE interfaces (P = 0.0012), but a P value of 0.063 was observed between the tibial plate PE interface and the internal condyle PE interface. The PE range of motion was 5.3 +/− 1.2° (range: −2.5 (external) to +3.2 (internal)) at last follow-up as compared to the first radiograph (3 months after operation). All trays preserved there mobility in rotation. Annual PE wear rates were extremely low as well as at the lower and the upper surfaces of the mobile bearing. Our results suggest that the long term mobility conservation contributed to low PE wear rates despite a high anatomic congruency due to the prosthetic design

Lateral instability of the patella was found after recurrent, habitual and permanent dislocations. Contracture of soft tissues lateral to the patella only occurred with habitual and permanent dislocations, but medial laxity was present in all cases. After adequate release of the lateral contracture, the medial stability was improved by transposition of the lower three-quarters of the pes anserinus to the medial border of the patella, and the patellar ligament. This created a relatively unstretchable physiological sling which ensured dynamic stability of the patella. Six recurrent, 21 habitual and nine permanent dislocations of the patella were treated by this method. Results were excellent in 21 patients, good in 13 and fair in two. The follow-up period varied from 21 to 84 months. There have been no recurrences to date

A cavovarus foot deformity was simulated in cadaver specimens by inserting metallic wedges of 15° and 30° dorsally into the first tarsometatarsal joint. Sensors in the ankle joint recorded static tibiotalar pressure distribution at physiological load.

The peak pressure increased significantly from neutral alignment to the 30° cavus deformity, and the centre of force migrated medially. The anterior migration of the centre of force was significant for both the 15° (repeated measures analysis of variance (ANOVA), p = 0.021) and the 30° (repeated measures ANOVA, p = 0.007) cavus deformity. Differences in ligament laxity did not influence the peak pressure.

These findings support the hypothesis that the cavovarus foot deformity causes an increase in anteromedial ankle joint pressure leading to anteromedial arthrosis in the long term, even in the absence of lateral hindfoot instability.

A pin-on-disc tribometer test with a rotating disc and a sector-wise loaded pin was used to determine friction coefficients for different material pairings. The four pin materials porcine cartilage, subchondral bone of the porcine cartilage, UHMWPE, vitamin E enhanced, crosslinked UHMWPE (VEPE) in combination with the three-disc materials zirconia toughened alumina ceramic (ZTA), CoCr, carbon-fibre-reinforced carbon (CrC) were tested. Stepwise loading was employed with the forces 10 N, 5 N, 2 N and 1 N. Test duration was 1 h. Diluted calf serum according ISO 14242-1 was used to determine the friction coefficients. The surface topography of all pins was examined using optical profilometry before and after the rotation tribometer tests. - No wear related modifications of the surface roughness parameters could be found. The coefficients of friction (COF) were lowest for the cartilage pins against all three-disc materials, with steady-state values between 0.01 and 0.02 for the highest applied load (10 N). Friction of subchondral bone yielded COF in the range 0.2 … 0.6, depending on the counterpart material. The two polyethylene materials behaved similar in this friction test with COF of about 0.1. The Ra roughness values of the different pins reflect the COF results: Ra of subchondral bone was one order of magnitude higher than Ra of the cartilage. This is in-line with the COF-values of bone being one order of magnitude higher than those of cartilage. These results will be discussed in view of the use of the disc materials as orthopaedic hemi-prostheses.

We performed a systematic review and meta-analysis to compare the efficacy of intermittent mechanical compression combined with pharmacological thromboprophylaxis, against either mechanical compression or pharmacological prophylaxis in preventing deep-vein thrombosis (DVT) and pulmonary embolism in patients undergoing hip or knee replacement. A total of six randomised controlled trials, evaluating a total of 1399 patients, were identified. In knee arthroplasty, the rate of DVT was reduced from 18.7% with anticoagulation alone to 3.7% with combined modalities (risk ratio (RR) 0.27, p = 0.03; number needed to treat: seven). There was moderate, albeit non-significant, heterogeneity (I² = 42%). In hip replacement, there was a non-significant reduction in DVT from 8.7% with mechanical compression alone to 7.2% with additional pharmacological prophylaxis (RR 0.84) and a significant reduction in DVT from 9.7% with anticoagulation alone to 0.9% with additional mechanical compression (RR 0.17, p < 0.001; number needed to treat: 12), with no heterogeneity (I² = 0%). The included studies had insufficient power to demonstrate an effect on pulmonary embolism.

We conclude that the addition of intermittent mechanical leg compression augments the efficacy of anticoagulation in preventing DVT in patients undergoing both knee and hip replacement. Further research on the role of combined modalities in thromboprophylaxis in joint replacement and in other high-risk situations, such as fracture of the hip, is warranted.

Aims. Micromotion of the polyethylene (PE) inlay may contribute to backside PE wear in addition to articulate wear of total knee arthroplasty (TKA). Using radiostereometric analysis (RSA) with tantalum beads in the PE inlay, we evaluated PE micromotion and its relationship to PE wear. Methods. A total of 23 patients with a mean age of 83 years (77 to 91), were available from a RSA study on cemented TKA with Maxim tibial components (Zimmer Biomet). PE inlay migration, PE wear, tibial component migration, and the anatomical knee axis were evaluated on weightbearing stereoradiographs. PE inlay wear was measured as the deepest penetration of the femoral component into the PE inlay. Results. At mean six years’ follow-up, the PE wear rate was 0.08 mm/year (95% confidence interval 0.06 to 0.09 mm/year). PE inlay external rotation was below the precision limit and did not influence PE wear. Varus knee alignment did not influence PE wear (p = 0.874), but increased tibial component total translation (p = 0.041). Conclusion. The PE inlay was well fixed and there was no relationship between PE stability and PE wear. The PE wear rate was low and similar in the medial and lateral compartments. Varus knee alignment did not influence PE wear. Cite this article: Bone Joint Res 2024;13(5):226–236

Aims. The aim of this study was to investigate whether wear and backside deformation of polyethylene (PE) tibial inserts may influence the cement cover of tibial trays of explanted total knee arthroplasties (TKAs). Methods. At our retrieval centre, we measured changes in the wear and deformation of PE inserts using coordinate measuring machines and light microscopy. The amount of cement cover on the backside of tibial trays was quantified as a percentage of the total surface. The study involved data from the explanted fixed-bearing components of four widely used contemporary designs of TKA (Attune, NexGen, Press Fit Condylar (PFC), and Triathlon), revised for any indication, and we compared them with components that used previous generations of PE. Regression modelling was used to identify variables related to the amount of cement cover on the retrieved trays. Results. A total of 114 explanted fixed-bearing TKAs were examined. This included 76 used with contemporary PE inserts which were compared with 15 used with older generation PEs. The Attune and NexGen (central locking) trays were found to have significantly less cement cover than Triathlon and PFC trays (peripheral locking group) (p = 0.001). The median planicity values of the PE inserts used with central locking trays were significantly greater than of those with peripheral locking inserts (205 vs 85 microns; p < 0.001). Attune and NexGen inserts had a characteristic pattern of backside deformation, with the outer edges of the PE deviating inferiorly, leaving the PE margins as the primary areas of articulation. Conclusion. Explanted TKAs with central locking mechanisms were significantly more likely to debond from the cement mantle. The PE inserts of these designs showed characteristic patterns of deformation, which appeared to relate to the manufacturing process and may be exacerbated in vivo. This pattern of deformation was associated with PE wear occurring at the outer edges of the articulation, potentially increasing the frictional torque generated at this interface. Cite this article: Bone Joint J 2021;103-B(12):1791–1801

Aims. The primary objective of this study was to compare the five-year tibial component migration and wear between highly crosslinked polyethylene (HXLPE) inserts and conventional polyethylene (PE) inserts of the uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary objectives included clinical outcomes and patient-reported outcome measures (PROMs). Methods. A double-blinded, randomized study was conducted including 96 TKAs. Tibial component migration and insert wear were measured with radiostereometric analysis (RSA) at three, six, 12, 24, and 60 months postoperatively. PROMS were collected preoperatively and at all follow-up timepoints. Results. There was no clinically relevant difference in terms of tibial component migration, insert wear, and PROMs between the HXLPE and PE groups. The mean difference in tibial component migration (maximal total point migration (MTPM)) was 0.02 mm (95% confidence interval (CI) -0.07 to 0.11), which is below the value of 0.2 mm considered to be clinically relevant. Wear after five years for HXLPE was 0.16 mm (95% CI 0.05 to 0.27), and for PE was 0.23 mm (95% CI 0.12 to 0.35). The mean difference in wear rate was 0.01 mm/year (95% CI -0.02 to 0.05) in favour of the HXLPE group. Wear is mainly present on the medial side of the insert. Conclusion. There is no clinically relevant difference in tibial component migration and insert wear for up to five years between the HXLPE conventional PE inserts. For the implant studied, the potential advantages of a HXLPE insert remain to be proven under clinical conditions at longer-term follow-up. Cite this article: Bone Joint J 2023;105-B(5):518–525

Aims. Patients with soft-tissue sarcoma (STS) who undergo unplanned excision (UE) are reported to have worse outcomes than those who undergo planned excision (PE). However, others have reported that patients who undergo UE may have similar or improved outcomes. These discrepancies are likely to be due to differences in characteristics between the two groups of patients. The aim of the study is to compare patients who underwent UE and PE using propensity score matching, by analyzing data from the Japanese Bone and Soft Tissue Tumor (BSTT) registry. Methods. Data from 2006 to 2016 was obtained from the BSTT registry. Only patients with STS of the limb were included in the study. Patients with distant metastasis at the initial presentation and patients with dermatofibrosarcoma protuberans and well-differentiated liposarcoma were excluded from the study. Results. A total of 4,483 patients with STS of the limb were identified before propensity score matching. There were 355 patients who underwent UE and 4,128 patients who underwent PE. The five-year disease-specific survival (DSS) rate was significantly better in the patients who received additional excision after UE than in those who underwent PE. There was no significant difference in local recurrence-free survival (LRFS) between the two groups. After propensity score matching, a new cohort of 355 patients was created for both PE and UE groups, in which baseline covariates were appropriately balanced. Reconstruction after tumour excision was frequently performed in patients who underwent additional excision after UE. There were no significant differences in DSS and LRFS between the patients who underwent PE and those who had an additional excision after UE. Conclusion. Using propensity score matching, patients with STS of the limb who underwent additional excision after UE did not experience higher mortality and local failure than those who underwent PE. Reconstruction may be necessary when additional excision is performed. Cite this article: Bone Joint J 2021;103-B(12):1809–1814