Introduction. Aseptic loosening of total knee replacements is a leading cause for revision. It is known that micromotion has an influence on the loosening of cemented implants though it is not yet well understood what the effect of repeated physiological loading has on the micromotion between implants and cement mantle. This study aims to investigate effect of physiological loading on the stability of tibial implants previously subjected to simulated intra-operative
Introduction. Aseptic loosening is one of the highest causes for revision in total knee arthroplasty (TKA). With growing interest in anatomically aligned (AA) TKA, it is important to understand if this surgical technique affects cemented tibial fixation any differently than mechanical alignment (MA). Previous studies have shown that
Since artificial joints are expected to operate for more than decades in human body, animal and clinical studies are not suitable for evaluation of their durability. Instead, in-vitro mechanical tests have been employed, but they cannot fully reproduce complex in-vivo mechanical and biochemical environment. For instance,
The development of more wear resistant biomaterials and better locking mechanisms for the polyethylene into the tibial base has significantly reduced polyethylene wear as a reason for revision TKA. Aseptic loosening is now the primary cause for revision TKA. Loosening can be caused by multifactorial operative issues: 1] patient selection, 2] implant alignment, 3] cementing technique. Furthermore, aseptic loosening occurs at a consistent rate over time. Increased cement penetration is important to counter bone resorption. Increasing penetration also improves cement mantle toughness leading to better mechanical integrity of the bone-cement interface and reduces bone-cement interface stress. It is important to recognise that a cleaner and drier interface does improve bone-cement penetration. Techniques to improve the process include better cement formulations, drilling sclerotic bone, devices and implant features to increase pressurization, using negative pressure suction ports in the tibia. We have extensive experience with CarboJet, a method of CO. 2. gas jet cleaning and drying. This experience was developed during 20 years of performing TKA with NO tourniquet. Schnetler et al found that the “use of a tourniquet in TKA causes a paradoxical increase in total blood loss”. So, NO tourniquet TKA is becoming the new paradigm for knee arthroplasty in reconstructive orthopaedics. Goldstein reported that pressurised carbon dioxide jet lavage resulted in a 35% increase in cement penetration depth when used vs. use of pulsatile saline lavage alone. Meneghini used this pressurised carbon dioxide system to study the influence of NO tourniquet use in TKA. He found a significant lowering of opioid consumption postoperatively. Another important factor in increasing the cement interdigitation is the influence of
The development of more wear resistant biomaterials and better locking mechanisms for the polyethylene into the tibial base has significantly reduced polyethylene wear as a reason for revision TKA. Aseptic loosening is now the primary cause for revision TKA. Loosening can be caused by multifactorial operative issues: 1] patient selection, 2] implant alignment, 3] cementing technique. Furthermore, aseptic loosening occurs at a consistent rate over time. Increased cement penetration is important to counter bone resorption. Increasing penetration also improves cement mantle toughness leading to better mechanical integrity of the bone-cement interface and reduces bone-cement interface stress. It is important to recognise that a cleaner and drier interface does improve bone-cement penetration. Techniques to improve the process include better cement formulations, drilling sclerotic bone, devices and implant features to increase pressurization, using negative pressure suction ports in the tibia. We have extensive experience with CarboJet, a method of CO2 gas jet cleaning and drying. This experience was developed during 20 years of performing TKA with NO tourniquet. Schnetler et al found that the “use of a tourniquet in TKA causes a paradoxical increase in total blood loss”. So, NO tourniquet TKA is becoming the new paradigm for knee arthroplasty in reconstructive orthopaedics. Goldstein reported that pressurised carbon dioxide jet lavage resulted in a 35% increase in cement penetration depth when used versus use of pulsatile saline lavage alone. Another important factor in increasing the cement interdigitation is the influence of
Osteogenesis Imperfecta (OI) is a heritable bone disorder characterized by bone fragility and often caused by mutations in the Type I collagen-encoding genes COL1A1 and COL1A2. The pathophysiology of OI, particularly at the cellular level, is still not well understood. This contributes to the lack of a cure for this disorder as well as an effective preventive or management options of its complications. In the bone environment, mesenchymal stem cells (MSCs) and osteoblasts (Ob) exert their function, at least partially, through the secretion of extracellular vesicles (EV). EV is a heterogeneous group of nanosized membrane-enclosed vesicles that carry/transfer a cargo of proteins,
Background. Rotator cuff tears pose a huge socioeconomic burden. Our study uses Fourier transform infrared spectroscopy (FTIR) as it is a quick, non-manipulative and non-destructive test, which can identify a wide range of chemical targets from small intraoperatively obtained specimens. The aim of this study was (i) to characterise the chemical and structural composition of rotator cuff tendons and (ii) to identify structural differences between anatomically distinct tear sizes. Such information may help to identify specific biomarkers of rotator cuff tear pathologies, which in turn could allow early identification and monitoring of disease progression. FTIR may provide insight into the different healing rates of different tear sizes. Methods. The infrared spectra of 81 torn rotator cuff tendons were measured using a FTIR spectrometer. The rotator cuff tear sizes were classified as partial, small, medium, large and massive, and compared to 14 normal controls. All spectra were classified using standard multivariate analysis; principal component analysis, partial least square and discriminant function analysis. Results. FTIR readily differentiated between normal and torn tendons, and different tear sizes. We identified the key discriminating molecules and spectra altered in torn tendons as: (i) carbohydrates/phospholipids (1030-1200 cm. -1. ), (ii) collagen (1300-1700, 3000-3350 cm. -1. ) and (iii)
Disorders of bone integrity carry a high global disease burden, frequently requiring intervention, but there is a paucity of methods capable of noninvasive real-time assessment. Here we show that miniaturized handheld near-infrared spectroscopy (NIRS) scans, operated via a smartphone, can assess structural human bone properties in under three seconds. A hand-held NIR spectrometer was used to scan bone samples from 20 patients and predict: bone volume fraction (BV/TV); and trabecular (Tb) and cortical (Ct) thickness (Th), porosity (Po), and spacing (Sp).Aims
Methods
Introduction. Implant contamination prior to cement application has the potential to affect the cement-implant bond. the consequences of implant contamination were investigated in vitro using static shear loading with bone cement and titanium dowels of differing surface roughness both with, and without contamination by substances that are likely to be present during surgery. Namely; saline, fat, blood and oil, as a negative control. Methods. Fifty Titanium alloy (Ti-6Al-4V) dowels were prepared with two surface finishes comparable to existing stems. The roughness (Ra and Rq) of the dowel surface was measured before and after the pushout test. Four contaminants (Phosphate Buffered Saline (PBS), ovine marrow, ovine blood, olive oil) were prepared and heated to 37°C. Each contaminant was smeared on the dowel surface completely and uniformly approximately 4 minutes prior to implantation. Samples were separated into ten groups (n=5 per group) based on surface roughness and contaminant. Titanium alloy dowels was placed in the center of Polyvinyl chloride (PVC) tubes with bone cement, and equilibrated at 37°C in PBS for 7 days prior to mechanical testing. The push out test was performed at 1 mm per minute. The dowel surface and cement mantel were analyzed using a Scanning Electron Microscopy (SEM) to determine the distribution and composition of any debris and contaminates on the surface. Results. All contaminants decreased stem-bone cement interfacial shear strength. Saline produced the greatest decrease, followed by blood. The effect of fat was less pronounced and similar to that of oil likely due to the strong
Moderately to highly crosslinked UHMWPEs have functioned for at least a decade with dramatic reduction in wear volumes in THA. This wear reduction has been associated with a markedly reduced incidence of radiographic osteolysis. However, CT studies have demonstrated that osteolysis is not completely eliminated. There, however, are still questions which include: Is cost for further improvements warranted?; Is 10 years long enough to assure that no clinically relevant osteolysis occurs, especially in younger patients?; Do we have any data demonstrating improvement in revision scenarios?; With high levels of crosslinking (requiring more radiation) some fractures have been demonstrated at the region of the locking mechanism of the liner to shell. Will this prevalence increase? These materials are softer and can cause quicker crack propagation than conventional polyethylene.; Do better locking mechanisms need to be developed to prevent fracture problems that have been demonstrated in the present generation cementless designs?; Do we need more information as to the optimal counterface choice (cobalt chrome, ceramic, oxinium)?; Can hip results be extrapolated to the knee where fatigue failure is a major problem both on the bearing surface and with the locking mechanism?; Is the oxidation we are beginning to see on the surface of retrieved liners (thought to be related to
Since its introduction in total hip replacements in the 1960's, Ultra High Molecular Weight Polyethylene (UHMWPE) has played a major role as a bearing component material for joint arthroplasty. Concerns were raised when issues of wear resistance became apparent, and therefore Highly Crosslinked Polyethylenes were introduced. Such materials undergo a thermal treatment to quench the free radicals and reduce progressive oxidation. However, said thermal treatment weakens the material mechanical properties and hence the use of antioxidants has been proposed and implemented in clinical use, mainly Vitamin-E. This can be added to the material before or after irradiation. If it is done before, part of the anti-oxydant is consumed during irradiation and so will not be available for its main purpose, and part reacts before irradiation with the free radicals thus reducing the crosslinking effect. If it is added after irradiation, high temperatures are required in order to diffuse it in the bulk material, and anyway the surface will be mainly rich in antioxidant. However, Vitamin-E tends to neutralize the free radicals on the oxidized
Perhaps the most significant developments in joint replacement surgery in the past decade have been in the area of multimodal pain management. This has reduced length of stay and opened the opportunity for cost savings and even outpatient joint replacement surgery for appropriately selected patients. The hallmark of this program is preemptive pain control with oral anti-inflammatory agents, gabapentin, regional anesthetic blocks that preserve quad function for TKA (adductor canal block) and long acting local anesthetics with the addition of injectable ketorolac and acetaminophen. Over the past two years utilising this type of program over 60% of our partial knee replacement patients are now returning home the day of surgery. We currently utilise a long acting local anesthetic delivery medication consisting of microscopic, spherical, lipid-based particles composed of a honeycomb-like structure of numerous nonconcentric internal aqueous chambers containing encapsulated bupivacaine separated from adjacent chambers by
Perhaps the most significant developments in joint replacement surgery in the past decade have been in the area of multimodal pain management. This has reduced length of stay in the inpatient hospital environment opening the opportunity for cost savings and even outpatient joint replacement surgery for appropriately selected patients. The hallmark of this program is pre-emptive pain control with oral anti-inflammatory agents, gabapentin, regional anesthetic blocks that preserve quad function for TKA (adductor canal block) and pericapsular long acting time release local anesthetics with the addition of injectable ketorolac and IV acetaminophen. Over the past two years utilising this type of program over 60% of our partial knee replacement patients are now returning home the day of surgery. We currently utilise a long acting local anesthetic delivery medication consisting of microscopic, spherical, lipid-based particles composed of a honeycomb-like structure of numerous nonconcentric internal aqueous chambers containing encapsulated bupivacaine separated from adjacent chambers by
Introduction. The wear performances of polyethylene in THA are influenced at a great extent by the manufacturing process. During the past decade, highly cross-linked materials have been developed with encouraging results in terms of wear, whereas another body of the literature has indicated potential catastrophic failures related to reduced fatigue properties and oxidation due to
Radiation cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is the bearing of choice in joint arthroplasty. The demands on the longevity of this polymer are likely to increase with the recently advancing deterioration of the performance of alternative metal-on-metal implants. Vitamin E-stabilized, cross-linked UHMWPEs are considered the next generation of improved UHMWPE bearing surfaces for improving the oxidation resistance of the polymer. It was recently discovered that in the absence of radiation-induced free radicals,
Successful osseointegration requires the production of a mechanically competent collagenous matrix, by osteoblasts, at the implant site. Lysophosphatidic acid (LPA) is a bioactive
Introduction. Vitamin-E (VE, dl-α-tocopherol) is a powerful antioxidant for highly cross-linked polyethylene (XLPE). It was previously reported that VE-stabilized XLPE succeeded in retaining no measurable oxidation even after accelerated aging tests combined with cyclic loading or
Introduction. Highly crosslinked polyethylene (HXLPE) was clinically introduced approximately a decade and a half ago to reduce polyethylene wear rates and subsequent osteolysis. Clinical and radiographic studies have repeatedly shown increased wear resistance, however concerns of rim oxidation and fatigue fracture remain. Although short to intermediate term retrieval studies of these materials are available, the long-term behavior of these materials remains unclear. Methods. Between 2000 and 2015, 115 1st generation HXLPE acetabular liners implanted for 5 or more years were collected and analyzed as part of an ongoing, multi-institutional orthopaedic implant retrieval program. There were two material cohorts based on thermal processing (annealed (n=45) and remelted (n=70)). Each cohort was stratified into two more cohorts based on implantation time (5 – 10 years and >10 years). For annealed components, the intermediate-term liners (n=30) were implanted on average (±SD) for 7.3 ± 1.7 years while the long-term liners (n=15) were implanted for 11.3 ± 1.8 years. For remelted components, the intermediate-term liners (n=59) were implanted on average (±SD) for 7.2 ± 1.3 years while the long-term liners (n=11) were implanted for 11.3 ± 1.2 years. For each cohort, the predominant revision reasons were loosening, instability, and infection (Figure 1). Short-term liners (in-vivo <5ys) from previous studies were analyzed using the same protocol for use as a reference. For oxidation analysis, thin slices (∼200 μm) were taken from the superior/inferior axis and subsequently boiled in heptane for 6 hours to remove absorbed
Introduction. Thermally treated 1st generation highly crosslinked polyethylenes (HXLPE) have demonstrated reduced penetration and osteolysis rates, however, concerns still remain with respect to oxidative stability and mechanical properties of these materials. To address these concerns, manufacturers have introduced the use of antioxidants to quench free radicals while maintaining the mechanical properties of the HXLPE. Two common antioxidants are α-tocopherol (Vitamin-E) and pentaerythritol tetrakis (PBHP). These may be either mixed prior to consolidation, or diffused throughout the polymer after consolidation and irradiation. In vitrostudies have shown that these materials are oxidatively stable and have improved mechanical properties compared to 1st generation HXLPEs; however, few studies have investigated the in vivo performance of anti-oxidant stabilized HXLPE. The purpose of this study was to investigate the revision reasons, oxidation, and mechanical properties of retrieved short-term anti-oxidant HXLPE. Methods. Between 2010 and 2015, 73 anti-oxidant HXLPE components were collected as a part of an IRB approved, multi-institutional retrieval analysis program during routine revision surgery. Of the seventy-three components, 30 (41%) were acetabular liners, whereas, 43 were tibial inserts. The components were fabricated from three different materials: Vitamin-E Diffused HXLPE (n=30; E1, Biomet), Vitamin-E Blended (n = 41; Vivacit-E, Zimmer) and PBHP blended (n = 2, AOX, DePuy). The hip and knee components were implanted for 0.7 ± 0.8 years (Range: 0.0–2.25 years) and 0.8 ± 1.1 years (Range: 0.0–4.5 years), respectively. Implantation time, patient weight, age, gender, and activity levels were similar between hip and knee components (Table 1). For oxidation analysis, thin slices (∼200μm) were taken from medial condyle and central eminence of the tibial inserts or the superior/inferior axis from hip components. The slices were boiled in heptane for six hours to extract
Introduction. Radiation cross-linked UHMWPEs were developed to address osteolysis-induced joint arthroplasty failure by improving wear resistance and reducing associated particulate debris. Introduced clinically fifteen years ago, they are the primary bearing surface in use with excellent clinical outcomes and wear resistance. First generation materials sought to maintain oxidative stability by reducing or eliminating free radicals through thermal treatments, while second generation aimed to further balance oxidation resistance and improve mechanical properties through sequential irradiation and annealing or the incorporation of an antioxidant. Recent reports have identified