Guided Bone Regeneration (GBR) uses biodegradable collagen membranes of animal origin tissues (dermis and pericardium). Their barrier effect prevents soft tissues to interfere with the regeneration of alveolar bone. However, their xenogeneic origin involves heavy chemical treatments which impact their bioactivity. Wharton's Jelly (WJ) from the umbilical cord is a recoverable surgery waste. WJ is mostly made from collagen fibers, proteoglycans, hyaluronic acid, and growth factors. WJ with immunologically privileged status and bioactive properties lends credence to its use as an allograft. Nevertheless, low mechanical properties limit its use in bone regenerative strategies. Herein, our objective is to develop a crosslinked WJ-based membrane to improve its strength and thus its potential use as a GBR membrane. The umbilical cords are collected after delivery and then stored at −20°C until use. The WJ membranes (1 × 5 × 12 mm) were obtained after the removal of blood vessels and amniotic tissue, washed, lyophilized, and stored at −20°C. WJ membranes were incubated in genipin solutions in decreasing concentrations (0.3 g / 100 mL − 0.03 g / 100 mL) for 24 hours at 37°C. The crosslinking degree was estimated by ninhydrin and confirmed by FTIR (Fourier-transform infrared spectroscopy) assays. The swelling rate was obtained after the rehydration of dry crosslinked WJ-membrane for 10 min in D-PBS. The mechanical properties were assessed in hydrated conditions on a tensile bench. The resistance to the degradation was evaluated by collagenase digestion (1 mg/mL for 60 hours) assay. The cytotoxicity of crosslinked WJ-membrane was evaluated in accordance with the standard ISO.10993-5 (i.e. Mitochondrial activity and Lactate Dehydrogenase release) against Mesenchymal Stem Cells (MSCs). Finally, the MSCs colonization and proliferation were followed after 21 days of culture on crosslinked WJ-membranes.Introduction and Objective
Materials and Methods
Found in bone-associated prosthesis, Cutibacterium acnes (C. acnes) is isolated in more than 50% of osteoarticular prosthesis infections, particularly those involving shoulder prostheses. Ongoing controversies exist concerning the origin of C. acnes infection. Few reports construct a reasonable hypothesis about probable contaminant displaced from the superficial skin into the surgical wound. Indeed, despite strict aseptic procedures, transecting the sebaceous glands after incision might result in C. acnes leakage into the surgical wound. More recently, the presence of commensal C. acnes in deep intra-articular tissues was reported. C. acnes was thus detected in the intracellular compartment of macrophages and stromal cells in 62.5% of the tested patients who did not undergo skin penetration. Among bone stromal cells, mesenchymal stem cells (MSCs) are predominantly found in bone marrow and periosteum. MSCs are the source of osteogenic lines of cells capable of forming bone matter. In this study, the pathogenicity of C. acnes in bone repair context was investigated. Human bone marrow derived MSCs were challenged with C. acnes clinical strains harvested from non-infected bone site (Cb). The behaviour of Cb strain was compared to C. acnes took from orthopaedic implant-associated infection (Ci). The infective capabilities of both strains was determined following gentamicin-based antibiotic protection assay. The morphology and ultrastructural analysis of infected MSCs was performed respectively through CLSM pictures of Phalloidin® stained MSCs cytoskeleton and DAPI labelled Cb, and transmission and scanning electron microscopies. The virulence of intracellular Ci and Cb (Ci-MSCs and Cb-MSCs) was investigated by biofilm formation on non-living bone materials; and the immunomodulatory response of infected MSCs was investigated (PGE-2 and IDO secretion detected by ELISA). Bone cells (osteoblasts and PMA differentiated macrophages) were then challenged with Cb-MSCs and Ci-MSCs. Intracellular accumulation of ROS within infected macrophages was assessed by flow cytometry after 2 h of infection and the catalase production by Cb-MSC and Ci-MSC was evaluated. Statistical analyses were performed using Mann & Whitney test.Introduction and Objective
Materials and Methods
Studies have shown that increased implant conformity in total knee arthroplasty (TKA) has been linked to increased constraint and thus rotational torque at the bone/implant interface. Anterior stabilized (AS) tibial inserts were designed to compensate for excessive AP motion in less-conforming cruciate-retaining (CR) tibial inserts. However, increased constraint may affect implant loading. Therefore, the purpose of this study is to model rotational prosthesis constraint based on implant-specific data and to compare rotational torque and 3D contact forces in implants with CR-lipped and AS tibial inserts during normal gait. A previously reported knee joint contact model was updated to include rotational torque due to prosthesis constraint (ASTM F1223(14)). Piecewise multiple linear regression with manually selected cutoff points was used to determine estimates of AP force, ML force, and rotation torque as functions of AP displacement, ML displacement, knee external rotation, respectively, and knee flexion angle from standard data. These functions were used to estimate total moment contribution of the prosthesis from measured knee displacement/rotation angles. Estimates were incorporated into the contact model equilibrium equations as needed by the model. As the model parametrically varies muscle activation coefficients to solve for the range of physiologically possible forces at each time point, the reported force/torque values are the mean across all solutions at each time point. Rotational torque and three dimensional contact forces were calculated for 14 informed-consented subjects, five with AS tibial inserts (1/4 m/f, 67±10 years, 29.2±4.4 BMI, 1/4 right/left) and nine with CR-lipped TKRs (2/7 m/f, 64±6 years, 30.6±5.8 BMI, 4/5 right/left). Rotational torque waveforms were compared using statistical nonparametric mapping; 3D contact forces were compared at mean timing of the flexion/extension moment peaks using independent samples t-tests.Introduction
Methods
Prosthetic Joint Infections (PJIs) are increasing with the use of orthopedic devices on an ageing population.
Preservation of the anterior cruciate ligament (ACL), along with the posterior cruciate ligament, is believed to improve functional outcomes in total knee replacement (TKR). The purpose of this study was to examine gait differences and muscle activation levels between ACL sacrificing (ACL-S) and bicruciate retaining (BCR) TKR subjects during level walking, downhill walking, and stair climbing. Ten ACL-S (Vanguard CR) (69±8 yrs, 28.7±4.7 kg/m2) and eleven BCR (Vanguard XP, Zimmer-Biomet) (63±11 yrs, 31.0±7.6 kg/m2) subjects participated in this IRB approved study. Except for the condition of the ACL, both TKR designs were similar. Subjects were tested 8–14 months post-op in a motion analysis lab using a point cluster marker set and surface electrodes applied to the Vastus Medialis Oblique (VMO), Rectus Femoris (RF), Biceps Femoris (BF) and Semitendinosus (ST). 3D motion and force data and electromyography (EMG) data were collected simultaneously. Subjects were instructed to walk at a comfortable walking speed across a walkway, down a 12.5% downhill slope, and up a staircase. Five trials per activity were collected. Knee kinematics and kinetics were analyzed using BioMove (Stanford, Stanford, CA). The EMG dataset underwent full-wave rectification and was smoothed using a 300ms RMS window. Gait cycle was time normalized to 100%; relative voluntary contraction (RVC) was calculated by dividing the average activation during downhill walking by the maximum EMG value during level walking and multiplying by 100%.Introduction
Methods
The 3D interplay between femoral component placement on contact stresses and range of motion of hip resurfacing was investigated with a hip model. Pre- and post-operative contours of the bone geometry and the gluteus medius were obtained from grey-value CT-segmentations. The joint contact forces and stresses were simulated for variations in component placement during a normal gait. The effect of component placement on range of motion was determined with a collision model. The contact forces were not increased with optimal component placement due to the compensatory effect of the medialisation of the center of rotation. However, the total range of motion decreased by 33%. Accumulative displacements of the femoral and acetabular center of rotation could increase the contact stresses between 5–24%. Inclining and anteverting the socket further increased the contact stresses between 6–11%. Increased socket inclination and anteversion in combination with shortening of the neck were associated with extremely high contact stresses. The effect of femoral offset restoration on range of motion was significantly higher than the effect of socket positioning. In conclusion, displacement of the femoral center of rotation in the lateral direction is at least as important for failure of hip resurfacings as socket malpositioning.
The bowing of the femur defines a curvature plane to which the proximal and distal femoral anatomic landmarks have a predictable interrelationship. This plane can be a helpful adjunct for computer navigation to define the pre-operative, non-diseased anatomy of the femur and more particularly the rotational alignment of the femoral component in total knee arthroplasty (TKA). There is very limited knowledge with regards to the sagittal curvature -or bowing- of the femur. It was our aim (1) to determine the most accurate assessment technique to define the femoral bowing, (2) to define the relationships of the curvature plane relative to proximal and distal anatomic landmarks and (3) to assess the position of femoral components of a TKA relative to the femoral bowing.Summary sentence
Background and aims
We report the outcome at a minimum of 10 years follow-up for 80 polished tapered stems performed in 53 patients less than 35-years-old with a high risk profile for aseptic loosening. Forty-six prosthesis were inserted for inflammatory hip arthritis and 34 for avascular necrosis. The mean age at surgery was 28 years in the inflammatory arthritis (17–35) and 27 years in the avascular necrosis (15–35) patients. At a mean follow-up of 14.5 years in the inflammatory arthritis group and 14 years in the avascular necrosis group respectively, survivorship of the 80 stems with revision of the femoral component for any reason as an endpoint was 100 % (95 % CI). Re-operation was because of failure of four metal-backed cups, 3 all polyethylene cups and one cementless cup. None of the stems were radiographically loose. All but two femoral components subsided within the cement mantle to a mean of 1.2 mm (0 tot 2.5) at final follow-up. Periarticular osteolysis was noted in 4 femurs in zone 7. This finding was associated with polyethylene wear and was only seen in those hips that needed revision for a metal backed cup loosening. Our findings show that the polished tapered stem has excellent medium-term results when implanted in young patients with high risk factors for aseptic loosening.
The Exeter stem is a polished cemented stem that has been associated with an excellent survivorship. However, this wedge shaped stem has also been associated with a relative higher risk for a peri-periprosthetic fracture due to the wedge-shaped configuration that can lead to a Vancouver type B2 fracture when the stem is being driven downwards inside the femoral canal by a traumatic blast. Traditionally, these fractures should be treated with a revision stem because the stem has become loosened in the fractured cement mantle. We present a case series of 5 cases where our treatment algorithm was to first let the non-displaced fracture to consolidate by 6 weeks of limited weight bearing as tolerated in order to conduct a second stage in-cement revision. This would simplify the revision procedure dramatically. However, all patients are currently pain free and do not require revision surgery although they are being monitored very closely. We conclude that non-displaced Vancouver type B2 fractures can be approached by a 2 stage treatment algorithm where the initial step is to let the fracture consolidate with limited weight bearing.
It was the purpose to evaluate the biomechanical changes that occur after optimal and non-optimal component placement of a hip resurfacing (SRA) by using a subject specific musculoskeletal model based on CT-scan data. Nineteen hips from 11 cadavers were resurfaced with a BHR using a femoral navigation system. CT images were acquired before and after surgery. Grey-value segmentation in Mimics produced contours representing the bone geometry and identifying the outlines of the 3 parts of the gluteus medius. The anatomical changes induced by the procedure were characterised by the translation of the hip joint center (HJCR) with respect to the pelvic and femoral bone. The contact forces during normal gait with ‘optimal’ component placement were calculated for a cement mantle of 3 mm, a socket inclination of 45° and anteversion of 15°. The biomechanical effect of ‘non-optimal placement’ was simulated by varying the positioning of the components.Introduction
Materials and Methods
The difference in the mean values regarding inclination was greater than would be expected by chance; there was a statistically significant difference (P = 0,010).
Navigation technique was discussed to equalize the drawback of MIS. However, tools like imageless navigation may further improve the cup position even in traditional approach.
The use of plate-and-cable constructs to treat periprosthetic fractures around a well-fixed femoral component in total hip replacements has been reported to have high rates of failure. Our aim was to evaluate the results of a surgical treatment algorithm to use these lateral constructs reliably in Vancouver type-B1 and type-C fractures. The joint was dislocated and the stability of the femoral component was meticulously evaluated in 45 type-B1 fractures. This led to the identification of nine (20%) unstable components. The fracture was considered to be suitable for single plate-and-cable fixation by a direct reduction technique if the integrity of the medial cortex could be restored. Union was achieved in 29 of 30 fractures (97%) at a mean of 6.4 months (3 to 30) in 29 type-B1 and five type-C fractures. Three patients developed an infection and one construct failed. Using this algorithm plate-and-cable constructs can be used safely, but indirect reduction with minimal soft-tissue damage could lead to shorter times to union and lower rates of complications.
Highly cross-linked polyethylene (XLPE) has been introduced in total hip arthroplasty in an effort to reduce polyethylene wear and the associated periprohetic osteolysis. Cross-linking is a procedure in which irradiation and subsequent heating stabilize the internal structure of PE. Most of the conventional PE’s used, are gamma irradiated in air or an inert environment with a dose level of no more than 25 to 50 kGy. By irradiating PE at a higher dose, optimally around 95–100 kGy, a definite reduction in wear rate has been achieved. History already provided us some mixed in vivo results regarding altered PE. Therefore, present time surgeons are cautious when it comes down to using a new PE. Some short follow up in vivo studies already suggested reduced wear rates with XLPE in comparison to conventional PE. Our aim was to demonstrate these reduced wear rates in a 2-dimensional head penetration model using the DICOMeasure™ computerized edge detection method (GreyStone, France) and to perform a clinical comparison of both groups using the Harris Hip Score and SF-36 questionnaire. Sixty hips with a Trilogy XLPE liner (Zimmer Co.) were age and BMI matched with a control group of twenty conventional Trilogy PE liners (Zimmer Co.). No differences in clinical performance were seen, but a statistically significant reduction of 67% in steady state wear rate was observed in the XLPE group. It is clear that, due to the reduction and stabilization of free radicals in polyethylene, a reduction in annual wear can be achieved.
We report the results of using impacted cancellous allografts and cement for fixation of the femoral component when revision arthroplasty is required in the face of lost bone stock. In 56 hips reviewed after 18 to 49 months there were few complications and a majority of satisfactory results with evidence of incorporation of the graft. Further study and review are necessary, but the use of the method appears to be justified.