The suture properties associated with a successful tendon repair are: high tensile strength, little tissue response, good handling characteristics and minimal plastic deformation. Plastic deformation contributes to gap formation at a tendon repair site. Gaps greater than 4mm are prone to failing. This study investigates whether the plastic deformation demonstrated by two commonly used suture materials can be reduced by manual pre-tensioning. Twenty sutures of both Prolene 3/0 (Ethicon, UK) and Ethibond 3/0 (Excel, Johnson and Johnson, UK) were tested. Half of the sutures in each group were manually pre-tensioned prior to knot tying and half were knotted without pre-tensioning. All knots were standard surgical knots with six throws. The suture lengths were measured before and after a standardised cyclical loading regime on an Instron tensile tester. The regime was designed to represent the finger flexion forces produced in a typical rehabilitation programme. All sutures were subsequently tested to their ultimate tensile strength. After cyclical loading the pre-tensioned sutures demonstrated a mean increase in suture length of 0.7% (range 0.1-1.9%). The sutures not pre-tensioned showed a mean increase of 5.4% (range 3.3-7%). This equates to 87% less plastic deformation (p <0.05 Students' T-test) upon pre-tensioning. There were no differences with Ethibond. Pre-tensioning had no effect on ultimate tensile strength for either group. Manual pre-tensioning reduces plastic deformation in Prolene 3/0 sutures without affecting the ultimate tensile strength. This simple technique could theoretically diminish gap formation at the site of a tendon repair

Recent findings about UHMWPE oxidation from in vivo stresses lead to the need of a better understanding of which anti-oxidant additivation method is the best option for the use in orthopaedic field. A GUR 1050 crosslinked Vitamin E - blended UHMWPE has been investigated, to provide an accurate outline of its properties. DSC and FTIR measurements, together with ageing and tensile tests were performed on compression moulded blocks, as well as biocompatibility tests, including implantation on rabbits. Moreover, wear simulations on finished components (Delta acetabular liners) have been completed. All the test procedures have been repeated for a reference material, a GUR 1050 crosslinked and remelted standard UHMWPE (commercial name UHMWPE X-Lima), and the outcomes have been compared to the crosslinked Vitamin E - blended UHMWPE ones. On the additivated UHMWPE, we found a ultimate tensile strength of 43 MPa, a yield strength value of 25 MPa, and an elongation to breakage equal to 320%. The degree of cristallinity was 45 ± 2%, and no signal of creation of oxidation products was detected up to 2000 h of permanence in oxidant ambient after the ageing test. The reference material showed comparable mechanical resistance values (∗ = 40 MPa, y = 20 MPa, 350% elongation), a cristallinity of 46 ± 2%, and the creation of oxidation products starting from 700 h in oxidant ambient. The biocompatibility tests indicate that the additivated material is biocompatible, as the reference X-Lima UHMWPE. Wear tests gave a wear rate of 5,09 mg/million cycles against 6,13 mg/million cycles of the reference material, and no sign of run in wear rate. Our results indicate that there is no change in mechanical properties in respect to the reference material. This is confirmed by DSC measurements, that show no change in cristallinity. The blend between polymer and additive assures an uniform concentration of Vitamin E across the whole thickness of the moulded block, and ageing test results on additivated UHMWPE have shown that the material possess a superior resistance to degradation phenomena. Biocompatibility assess that the presence of Vitamin E is not detrimental for the in vivo use of the material, and wear results indicate a better wear resistance of the material, especially in the first stages of the wear process. From these considerations, it can be concluded that the material, in respect to the standard UHMWPE, is highly resistant to oxidation phenomena, therefore it is expected to have superior in vivo endurance performance

Introduction. Cobalt chrome on polyethylene remains a widely used bearing combination in total joint replacement. However wear induced osteolysis, bulk material property degradation of highly cross-linked polyethylene (HXLPE) [1], and oxidation after implantation (thought to be as a result of lipid absorption or cyclic loading [2]) remains a concern. ECIMA is a cold-irradiated, mechanically annealed, vitamin E blended next generation HXLPE developed to maintain mechanical properties, minimise wear and to improve the oxidation resistance in the long-term. The aim of this study was to compare the in-vitro wear rate and mechanical properties of three different acetabular liners; conventional UHMWPE, HXLPE and ECIMA. Methods. Twelve liners (Corin, UK) underwent a 3 million cycle (mc) hip simulation. Three conventional UHMWPE liners (GUR1050, Ø32 mm, 30 kGy sterilised in Nitrogen), three HXLPE liners (GUR1020, Ø40 mm, 75 kGy cross-linking and EtO sterilised) and six ECIMA liners (0.1 wt% vitamin E GUR1020, Ø40 mm, 120 kGy cross-linking, mechanically deformed and annealed, and EtO sterilised) articulated against CoCrMo alloy femoral heads to ASTM F75 (Corin, UK). Wear testing was performed in accordance with ISO 14242 parts 1 and 2, with a maximum force of 3.0 kN and at a frequency of 1 Hz. The test lubricant used was calf serum with a protein content of 30 g/l and 1% (v/v) patricin added as an antibacterial agent. Volumetric wear rate was determined gravimetrically after the first 0.5 mc and every 1 mc thereafter. ASTM D638 type V specimens (3.2 mm thick) were machined from ECIMA material for uniaxial tension testing to ASTM D638. Ultimate tensile strength (UTS), yield strength and elongation values were measured. These values were compared to mechanical data available for the other material types. Results. There was a 94% and a 68% reduction in the wear rate for the ECIMA liners compared to the conventional UHMWPE and HXLPE liners respectively. There was an increase in UTS, yield strength and elongation of 11%, 11% and 15% respectively, for ECIMA compared to HXLPE. Discussion. The wear results reported in this study indicate that ECIMA is a very low wearing material which has the potential to reduce wear related osteolysis in-vivo. Importantly, the mechanical properties were generally maintained unlike the degradation found in many modified polyethylene materials and were more comparable to conventional UHMWPE than HXLPE. The reduced wear rate during in-vitro hip simulation of ECIMA compared to conventional UHMWPE, coupled with improved mechanical properties in comparison to HXLPE, makes ECIMA a promising next generation, advanced bearing material

INTRODUCTION. The lifetime of UHMWPE implants may be limited by wear and oxidative degeneration. Wear produced particles are in general biologically active, and may induce osteolysis. As threshold of PE wear rate below which osteolysis is rarely observed is postulated to be less tahn 0.1 mm per year. Moreover, PE delamination and breakage are consequences of the embrittlement of the PE due to oxidation. Both demonstrate, that improving the clinical behaviour of UHMWPE means reduction of wear particles. The first can be achieved by cross-linking the second by the anti-oxidative stabiliser vitamin E. The highly cross-linked PE vitamys ® used for the isoelastic monobloc cup RM Pressfit (Mathys AG Bettlach, Bettlach, Switzerland) is mixed with 0.1% of synthetic vitamin E and is the first and only highly cross-linked PE used in total hip replacement that meets all requirements for the best grade UHMWPE in yield strength, ultimate tensile strength and elongation at break. METHODS AND MATERIAL. With the first implantation of RM Pressfit vitamys® a prospective multicentre study was started. So far 256 cases in 7 clinics from Europe and New Zealand are included. This report presents the first clinical experiences of one Swiss clinic from the multicentre study. Prospective data collection includes Harris Hip score (HHS), patient satisfaction and radiographic analysis. Clinical and radiographic follow-up is done after 6 weeks, 6, 12 and 24 months, and thereafter for long-term results. Standardized documentation of surgery and postoperative course is performed. RESULTS. 81 patients were included in the study. Mean age at implantation is 69 years. The indication was primary OA in 57% and secondary OA in 36%, the others were treated either for necrosis, fracture or hip dysplasia. 68% of the patients received a 36mm femoral head, 31% a 32mm and 1% a 28mm. Intraoperatively two minor complications occurred, one femur and one trochanter fissure. No complications occurred during implantation of the cup. Most of the cups (59%) were implanted with an inclination of 40°-50°, 30% with 35°-40°. There were no signs of early loosening and a good Harris Hip Score was achieved. DISCUSSION. The principals of this monobloc cup with its isoelastic property and the thin titanium coating is a proven concept. Ihle et al. (JBJS 2008) reported 91% survival rate with revision for aseptic loosening as endpoint after 20 years. They found an increase of cup revisions after 14 to 16 years after implantation due to osteolysis probably due to PE wear. At short term, we haven't encountered any problems related to the implantation of this cup. So far one patient in the entire multicentre study needed a stem revision after periprosthetic femur fracture. To prove the durability of this novel material a follow-up of 14 years and more will be required

We reviewed 59 bone graft substitutes marketed by 17 companies currently available for implantation in the United Kingdom, with the aim of assessing the peer-reviewed literature to facilitate informed decision-making regarding their use in clinical practice. After critical analysis of the literature, only 22 products (37%) had any clinical data. Norian SRS (Synthes), Vitoss (Orthovita), Cortoss (Orthovita) and Alpha-BSM (Etex) had Level I evidence. We question the need for so many different products, especially with limited published clinical evidence for their efficacy, and conclude that there is a considerable need for further prospective randomised trials to facilitate informed decision-making with regard to the use of current and future bone graft substitutes in clinical practice.

Cite this article: Bone Joint J 2013;95-B:583–97.