Abstract. Purpose. Intracanal rib head
Introduction. Failure of total knee replacements due to the generation of polyethylene wear debris remains a crucial issue in orthopedics. Unlike the hip, it is difficult to accurately determine knee implant wear rates from retrieved components. Several studies have relied on thickness measurements to estimate
Aim. A reason for treatment failure, in cases of periprosthetic bone infections and osteomyelitis, may be incomplete or heterogeneous tissue distribution of antimicrobials to the affected bone. Decreased bioavailability has been demonstrated in healthy bones but never in pathological bone tissue. Therefore, the aim was to obtain pharmacokinetic parameters of cefuroxime in infected bone tissue by means of microdialysis in a porcine model of implant associated osteomyelitis. Method. An implant cavity of 4 mm in diameter was drilled 25 mm into the right tibial bone of ten pigs (30 kg/BW). Subsequently, a small steel implant (K-wire 2 × 2 mm) and 10. 4. CFU of Staphylococcus aureus was inserted and injected into the implant cavity. Five days after inoculation, two additional drill holes of 2 × 25 mm were drilled into the trabecular bone tissue adjacent to the implant cavity and into the left uninfected tibia. After intravenous administration of 1500 mg of cefuroxime, the concentration was measured in plasma and in the three tibial drill holes for 8 hours. All measurements were performed with microdialysis. Post mortem, the presence of bone infection was assessed by computed tomography (CT) scans and cultures of swabs. Results. Destruction of bone tissue was seen on CT scans around all implant cavities but not in the adjacent trabecular bone tissue of the right leg or in the left leg. All swabs from the implant cavity and 8/10 swabs from the adjacent trabecular tissue were positive for S. aureus. Conversely, all swabs from the left tibia were negative. The area under the concentration-time curves differed significantly, with the lowest found in the implant cavity (P<0.001). Although not significant, cefuroxime
Introduction. While fixation on the acetabular side in resurfacing implants has been uncemented, the femoral component is usually cemented. The most common causes for early revision in hip resurfacing are femoral head and or neck fractures and aseptic loosening of the femoral component. Later failures appear to be more related to adverse soft-tissue reactions due to metal wear. Little is known about the effect of cementing techniques on the clinical outcome in hip resurfacing, since retrieval analysis of failed hip resurfacing show large variations. Two cementing techniques have dominated. The indirect low viscosity (LV) technique as for the Birmingham Hip resurfacing (BHR) system and the direct high viscosity (HV) technique as for the Articular Surface replacement (ASR) system. The ASR was withdrawn from the market in 2010 due to inferior short and midterm clinical outcome. This study presents an in vitro experiment on the cement mantle parameters and
Introduction. The purpose of this prospective randomized study was to compare the 2-year follow-up
Extensor tendon ruptures have been reported in up to 8.8% of patients after volar plating and long screws have been implicated. The dihedral dorsal surface of the distal radius hinders accurate screw length determination using standard radiographic views (lateral; pronation and supination). A ‘dorsal tangential’ view has recently been described, but has not been validated. To validate this view, we mounted a plate-instrumented sawbone onto a jig. Radiographs at different angles were reviewed independently by 11 individuals. Skyline views clearly demonstrated all screw tips, whereas only 69% of screw tips were identifiable on standard views. With screws 2mm proud of the dorsal surface, skyline views detected 67% of long screws (sensitivity). The best of the standard views achieved only 11% sensitivity. At 4mm long, skyline sensitivity was 85%, compared with 25% for standard views. At 6mm long, 100% of long screws were detected on skylines, but only 50% of 8mm long screws were detected by standard views. Inter and intra-observer variability was 0.97 (p=0.005). For dorsal screw length determination of the distal radius, the skyline view is superior to standard views. It is simple to perform and its introduction should reduce the incidence of volar plate-related extensor tendon rupture.
Background. Surgical site infection following spine surgery is associated with increased morbidity, mortality and increased cost for the health care system. The reported pooled incidence is 3%. Perioperative antibiotic prophylaxis is a key factor in lowering the risk of acquiring an infection. Previous studies have assessed perioperative cefuroxime concentrations in the anterior column of the cervical spine with an anterior surgical approach. However, the majority of surgeries are performed in the posterior column and often involve the lumbar spine. Accordingly, the objective was to compare the perioperative tissue concentrations of cefuroxime in the anterior and posterior column of the same lumbar vertebra using microdialysis in an experimental porcine model. Method. The lumbar vertebral column was exposed in 8 female pigs. Microdialysis catheters were placed for sampling in the anterior column (vertebral body) and posterior column (posterior arch) within the same vertebra (L5). Cefuroxime (1.5 g) was administered intravenously over 10 min. Microdialysates and plasma samples were continuously obtained over 8 hours. Cefuroxime concentrations were quantified by Ultra High Performance Liquid Chromatography Tandem Mass Spectrometry. Microdialysis is a catheter-based pharmacokinetic tool, that allows dynamic sampling of unbound and pharmacologic active fraction of drugs e.g., cefuroxime. The primary endpoint was the time with cefuroxime above the clinical breakpoint minimal inhibitory concentration (T>MIC) for Staphylococcus aureus of 4 µg/mL as this has been suggested as the best predictor of efficacy for cefuroxime. The secondary endpoint was tissue
During total knee arthroplasty (TKA), a tourniquet is often used intraoperatively. There are proposed benefits of tourniquet use including shorter duration of surgery, improved surgical field visualization and increased cement
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
The avascular nature of articular cartilage relies on diffusion pathways to obtain essential nutrients and molecules for cellular activity. Understanding these transport pathways is essential to maintaining and improving the health of articular cartilage and ultimately synovial joints. Several studies have shown that joint articulation is associated with fluid and solute uptake although it remains unclear what role sliding motion independently plays. This study investigates the role of sliding with a non-stationary contact area on the uptake of small molecular weight tracers into articular cartilage. Ten-millimeter diameter cartilage-bone plugs were obtained from porcine knee joints and sealed into purpose made diffusion chambers. The chambers were designed to eliminate diffusion from the radial edge and only allow diffusion through the articular surface. The bone side of the chamber was filled with PBS to maintain tissue hydration while the cartilage side was filled with 0.01mg/ml fluorescein sodium salt (FNa) prepared using PBS. Sliding loads with a non-stationary contact area were applied across the articular surface by a custom apparatus using a 4.5 mm diameter spherical indenter. A moving contact area was chosen to represent physiological joint motions. Reciprocal sliding was maintained at a rate of 5 mm/s for 2 and 4 hours. Control samples were subject to passive diffusion for 0, 4, and 88 hours. After diffusion tests, samples were snap frozen and 20 µm cross-sectional cuts were taken perpendicular to the sliding direction. Samples were imaged using a Zeiss AxioImager M2 epifluorescent microscope under 5× magnification with a filter for FNa. Intensity profiles were mapped from the articular surface to the subchondral bone. Unloaded control samples demonstrated minimal solute uptake at 4 hours penetrating less than 5% of the total cartilage depth. By 88 hours solute
Aim. The increasing incidence of orthopaedic methicillin-resistant Staphylococcus aureus (MRSA) infections represents a significant therapeutic challenge. Being effective against MRSA, the role of vancomycin may become more important in the orthopaedic setting in the years to come. Nonetheless, vancomycin bone and soft tissue
The dual mobility design concept for acetabular components is intended to reduce the risk of dislocation and increase range of motion, but the wear pattern of this design is unclear and may have implications in implant fixation. Additionally, the solid back cups do not have the option for supplementary screw fixation, providing an additional smooth articulating surface for the liner to move against. The objective of this study was to assess cup fixation by measuring implant migration as well as proximal femoral head
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
Introduction. Total Hip Arthroplasty (THA) devices are now increasingly subjected to a progressively greater range of kinematic and loading regimes from substantially younger and more active patients. In the interest of ensuring adequate THA solutions for all patient groups, THA polyethylene acetabular liner (PE Liner) wear representative of younger, heavier, and more active patients (referred to as HA in this study) warrants further understanding. Previous studies have investigated HA joint related morbidity [1]. Current or past rugby players are more likely to report osteoarthritis, osteoporosis, and joint replacement than a general population. This investigation aimed to provide a preliminary understanding of HA patient specific PE liner tribological performance during Standard Walking (SW) gait in comparison to IS0:14242-1:2014 standardized testing. Materials and Methods. Nine healthy male subjects volunteered for a gait lab-based study to collect kinematics and loading profiles. Owing to limitations in subject selection, five subjects wore a weighted jacket to increase Body Mass Index ≥30 (BMI). An induced increase in Bodyweight was capped (<30%BW) to avoid significantly effecting gait [3] (mean=11%BW). Six subjects identified as HA per BMI≥30, but with anthropometric ratios indicative of lower body fat as previously detailed by the author [2] (Waist-to-hip circumference ratio and waist circumference-to-height ratio). Three subjects identified as Normal (BMI<25). Instrumented force plate loading profiles were scaled (≈270%BW) in agreement with instrumented hip force data [4]. A previously verified THA (Pinnacle® Marathon® 36×56mm, DePuy Synthes) Finite Element Analysis wear model based on Archard's law and modified time hardening model [5] was used to predict geometrical changes due to wear and deformation, respectively (Figure 1). Subject dependent kinematic and loading conditions were sampled to generate, for both legs, 19 SW simulation runs using a central composite design of response surface method. Results. HA group demonstrated comparable SW gait characteristics and Range of Motion (RoM) to the Normal group (p>0.1) (Figure 2) but statistically greater SW peak loads, PE liner wear rates, deformation, and
Aims. Vancomycin may be an important drug for intravenous perioperative antimicrobial prophylaxis in spine surgery. We assessed single-dose vancomycin intervertebral disc, vertebral cancellous bone, and subcutaneous adipose tissue concentrations using microdialysis in a pig model. Methods. 8 female pigs received 1,000 mg of vancomycin intravenously as a single dose over 100 minutes. Microdialysis probes were placed in the C3-C4 intervertebral disc, C3 vertebral cancellous bone, and subcutaneous adipose tissue, and vancomycin concentrations were obtained over 8 hours. Venous blood samples were obtained as reference. Results. Ranging from 0.24 to 0.60, vancomycin tissue
Background and aim. A significant reduction in wear using Durasul highly cross-linked polyethylene (PE) versus Sulene polyethylene (sterilized with nitrogen) at 5 and 10 years have been reported previously. We ask if the improvement observed at the earlier follow-up continues at 15 years. Methods. Between 1999 and 2001, 90 hips underwent surgery using the same cementless cup and stem: 45 received Allofit cups with a Sulene-PE liner and 45 Allofit cups with a Durasul-PE liner, both associated with an Alloclassic stem (28 mm metallic femoral head). 66 hips of this prospective comparative study were available over a minimum follow-up of 15 years. Linear femoral head
Do we need new polyethylene? Is there a clinical problem with first generation crosslinked polyethylene (XLPE)? Are we being duped into believing that doped polyethylene will solve a problem?. Clinical failures of polyethylene bearing total hip replacements are related to wear and the mechanical properties of the polyethylene. Wear is primarily related to crosslinking. Wear failures are secondary to periprosthetic osteolysis while mechanical failure causes cracking of thin polyethylene. Use of large femoral heads that reduce dislocation may increase wear and mechanical failure in the second decade of XLPE use. There is no question that XLPE has reduced 2-dimensional (2D) head
Introduction. Osteolysis caused by wear of the ultrahigh molecular weight polyethylene (UHMWPE) often leads to failure. Cross-linking improves wear, but also produces residual free radicals that decrease oxidative stability. In vitro studies have shown that the anti-oxidative properties of vitamin E UHMWPE stabilize free radicals while retaining the physical and chemical properties of UHMWPE. The porous surface of the Regenerex™ shell was developed for improved bone in-growth fixation. The increased porosity of the Regenerex™ shell promotes early bony in-growth with the goal of greater long-term stability. The purpose of this study was to evaluate vitamin E infused polyethylene (VEPE) wear and stability of acetabular and femoral components using RSA. Methods. 58 patients (64 observed hips), all with osteoarthritis, gave informed consent to participate in a 5 year RSA study. Each patient received a VEPE liner, a Regenerex™ acetabular shell, and an uncemented stem with either a 32mm or 36 mm cobalt chrome femoral head. Tantalum beads were inserted into the VEPE, the pelvic and the femoral bone to measure head
The direction of
Introduction:. Highly cross-linked polyethylene (XLPE) was introduced into clinical practice to decrease acetabular cup wear in total hip arthroplasty (THA) based upon extremely low wear rates in vitro. Numerous short-term clinical studies using XLPE cups have shown promising improvements in wear performance. In this study we evaluated in vivo wear performance of XLPE cups compared to conventional PE (CPE) cups in primary THA at a minimum five years follow-up. Materials and Methods:. Between October 2003 and March 2005, 114 hips were randomized to receive either a CPE cup or a XLPE cup with primary THA. A single experienced surgeon performed all cases at the same hospital. All hips received a CoCr femoral head and a cementless acetabular shell (Trilogy, Zimmer, Warsaw). One-hundred three cases received cementless femoral stems and eleven stems were cemented. Forty-six hips received a 26 mm head size CPE cup (gamma sterilized at 25 kGy), and 68 hips received XLPE cups (10 Mrad e-beam irradiation, EtO sterilized) in 26 mm (47 hips), 28 mm (11 hips) and 32 mm (10 hips) head sizes. The mean age in the XLPE and CPE groups was 57 ± 8 and 62 ± 8, respectively (p < 0.05). Mean follow up was 70 months (range, 60 to 91 months). Supine AP radiographs were obtained postoperatively at 2, 6, 9, 12, 18, 24, 36, 48, and 60 months, and at final follow-up. Each radiograph was assessed for femoral head