Purpose. The purpose of this study is to compare using a novel cementing technique with hydroxyapatite granules at
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
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
Aim. The aim of this study is to evaluate if the gentamycin elution from bone cement is influenced by the timing of application of the antibiotic powder. Method. This was an experimental in vitro study that compared the elution properties of different formulation of gentamycin from a commercially available hip, knee and shoulder cement spacers. Four different experimental models were prepared. Five different spacers were prepared for each experimental mode and for each joint. We compared four different formulation of cement spacers: spacer #1, in which the spacer was prepared with a premixed
Introduction. Total hip replacement is an established surgical procedure done to alleviate hip pain due to joint diseases. However, this procedure is avoided in yonger patients with higher functional demands due to the potential for early failure. An ideal prosthesis will have have a high endurance against impact loading, with minimal micromotion at the bone cement interface, and a reduced risk of fatigue failure, with a favourable stress distribution pattern in the femur. We study the effect of varying the material properties and design element in a standard cemented total hip using Finite Element Analysis. Methods. A patient-specific 3D model of femur will be constructed from CT scan data, while a Summit® Cemented Hip System (DePuy Orthopedic) will be used to as a control for comparative evaluation. We vary the material stiffness of different parts of the prosthesis(see Fig.1) to formulate a design concept for a new total hip prosthesis design; and use Finite Element Method to predict the micromotion of the hip prosthesis at the bone cement interface, as well as the stress distribution in the the femur. Result. Validation of computational protocol was being done by comparing the principal maximum strain of the femoral cortex along the diaphysis, and the amount of deflection, with published literature, similarly, contact modelling validation was also done. Model 1–4 induced lower peak Von Mises stress in the cement, which takes a much lower value than any of the cement mechanical limits postulated. Therefore, the risk of cement failure is greatly reduced in Model 1–4. However, the effect of varying stiffness in different regions is not significant in terms of load transmission to the cement. Micromotion at the
Total knee replacements are being more commonly performed in active younger and obese patients. Fifteen-year survivorship studies demonstrate that cemented total knee replacements have excellent survivorship, with reports of 85 to 97%. Cemented knee arthroplasties are doomed to failure due to loss of cement-bone interlock over time. Inferior survivorship occurs in younger patients and obese patients who would be expected to place increased stress on the
Introduction. Damage development in cemented acetabular replacements has been studied in bovine pelvic bones under long-term physiological. 1. loading, albeit dry, conditions, using a specially designed hip simulator. 2. In this work we report further experimental results from testing in wet condition in a new custom designed environmental chamber. Damage was detected and monitored using mCT scanning at regular intervals of the experiments. Two dimensional projections in the axial, sagittal and coronal planes were extracted from the 3D data for fatigue damage identification. The simulated mechanical and biological effects on the initiation and evolution of the damage of cemented acetabular reconstructs were examined and compared with those under dry condition. Materials and methods. Bovine bones were treated and reamed to receive a cemented polyethylene cup (Charnley ogee, Depuy Int) in the standard position. Standard cementing technique was utilised to apply the cement (CMW1, DePuy CMW) into the socket, with an average cement mantle thickness of 2–3 mm. The combined loading block included four routine activities, as measured by Bergmann et al. 1. , was programmed into a specially designed 4-station hip simulator for endurance testing of cement fixation. 2. A body weight of 125 kg was assumed to represent an upper bound load case and to accelerate the tests. A custom made environmental chamber (Fig. 1) was designed and built to accommodate saline solution (0.9% NaCl), where the temperature was kept constantly at 37°C. The implanted bone samples were removed from the test rig at regular intervals (100,000 and 200,000 cycles) and examined using a mCT scanner. Results and discussion. For the tests under dry condition. 2. , μCT images showed progressive development of radiolucent lines, usually in the superior-posterior quadrant near the dome region which led to gross failure; and the number of cycles to failure seems to be related to the type of physiological loadings in that the worst case was found to be descending stairs, followed by combined loading and normal walking. For the tests conducted under wet condition, debonding was detected at the
In North America, cementless femoral replacement has all but replaced cementing and cement technique is at risk for becoming a lost art. Published results of cemented femoral components with a well-designed femoral component and good surgical technique are excellent and equivalent to cementless technology. With an increasing focus on cost as part of value-based care, consideration for returning to cement for a select population is appropriate. Furthermore, there are patient populations that may benefit from a cemented femur with registries demonstrating superior short term outcomes. These include the elderly and patients with osteoporotic femurs. The goal of femoral cementing is to maximise the interdigitation of bone cement with metaphyseal trabecular bone and the irregular surface of the endosteum while at the same time minimizing the risk of embolization. The steps for femoral cementing include:cFemoral broaching – understand the relationship between the broach and stem as it relates to cement mantle thickness; Canal preparation; Gentle curetting to remove loose cancellous bone; Pressurised lavage to remove fat and marrow elements – this decreases the risk of embolization and enhances the strength of the
After over 4 decades of experience with total knee arthroplasty, many lessons have been learned regarding surgical technique. These include exposure issues, alignment methods, bone preparation, correction of deformity, implantation techniques and wound closure. Where is the proper placement of the skin incision relative to the tibial tubercle? How does one safely evert the patella in the obese or ankylosed knee? Can a tibial tubercle osteotomy be avoided in the ankylosed knee? How does one protect the patellar tendon insertion from avulsing? How do you protect the soft tissues from debris and contamination and minimise the potential for infection? Can exposure be maintained if there are few surgical assistants? How do you find the lateral inferior genicular vessels and minimise postoperative bleeding? How do you know where to enter the intramedullary femoral canal for placement of the distal femoral alignment device? How can you avoid notching the anterior femoral cortex when in-between sizes or there is a pre-existing dysplastic trochlea? How can you correct a varus deformity without performing a formal MCL release? An inverted cruciform lateral retinacular release effectively corrects a severe valgus deformity and avoids the need for an LCL release. Trimming the posterior femoral condyles and removing posterior osteophytes is best accomplished using a trial femoral component as a template. Zone 4 femoral
The interest in osteolysis has waned largely due to the impact of crosslinked polyethylene and the “rarity” of this phenomenon. However, the basic process still remains: particles, motion observed with unstable implants and host specific factors all play a role in bone loss around implants. There are 2 predominant patterns of lysis: Linear versus Expansile. Linear Lysis: is focal bone loss at the interface as seen in the bone cement interface in when using acrylic or at the implant-host interface with porous ingrowth/ongrowth implants. Expansile Lysis: is observed in less contained regions such as the retro- and supra-acetabular regions around the socket. These lesions can also be quite extensive yet may be subtle in appearance. Imaging is essential in identifying the extent and magnitude of osteolysis. Available modalities include plain radiographs although they can be of limited value in that even with oblique views, they often underestimate the degree of bone loss. CT scans are useful but can be limited by artifact. Several centers have explored the role of MRI in assessing lysis. It can be useful for bone loss and provides excellent assessment for soft tissue: abductors, neurovascular structures. Metal artifact reduction sequencing is required to maximise information obtainable. Management of osteolysis: Identification and monitoring periprosthetic osteolysis is a crucial element of patient care. Progressive bone loss leading to loss of fixation and the potential risk for periprosthetic fracture is a real possibility and early recognition and intervention is a priority. The basic Guiding Principles of management are centered around several key elements including the source of osteolysis and degree, the fixation of implant, the location of lysis, the track record of implant system, the presence of patient symptoms (if any), and finally the patient age, activity level, and general health. Specifics of treatment of osteolysis around the acetabulum: With cemented sockets, lysis is typically seen late and frequently at the
Introduction. Varying degrees of posterior glenoid bone loss occurs in patients with end stage osteoarthritis and can result in increased glenoid retroversion. The excessive retroversion can affect implant stability, eccentric glenoid loading, and fixation stresses. Ultimately, the goal is to correct retroversion to restore normal biomechanics of the glenohumeral joint. The objective of this study was to identify the optimal augmented glenoid design based on finite element analysis (FEA) modeling which will provide key insights into implant loosening mechanisms and stability. Materials and Methods. Two different augmented glenoid designs, posterior wedge and posterior step- were created as a computer model by a computer aided design software (CAD). These implant CAD models were created per precise manufacturers dimensions and sizes of the augmented implant designs. These implants were virtually implanted to correct 20° glenoid retroversion and the different mechanical parameters were calculated including: the glenohumeral subluxation force, relative micromotion at the
Critical review of the literature fails to make a convincing case for use of cement in TKA. Many studies demonstrate clinical, mechanical, and biological failure when cement is used for fixation. Work by Ryd et al. has shown that initial migration within the first few months diminished rapidly after the first 6 months with virtually no additional movement for years after. They also suggested that cemented components do not remain rigidly fixed to bone long-term, but loosen enough to move 0.2 to 1 mm at the
Introduction. Although total hip arthroplasty (THA) has been one of the most successful, reliable and common prosthetic techniques since the introduction of cemented low-friction arthroplasty by Charnley in the early 1960s, aseptic loosening due to stem-cement and cement-bone interface failures as well as cement fractures have been known to occur. To overcome this loosening, the stem should be mechanically retentive and stable for long term repetitive loading. Migration studies have shown that all stems migrate within their cement mantle, sometimes leading to the stem being debonded from the cement [1]. If we adopt the hypothesis that the stems debond from the cement mantle, the stem surface should be polished. For the polished stem, the concept of a double taper design, which is tapered in the anteroposterior (AP) and mediolateral (ML) planes, and a triple-tapered design, which has trapezoidal cross-section with the double tapered, have been popularized. Both concepts performed equally well clinically [2]. In this study, we aimed to analyze stress patterns for both models in detail using the finite element (FE) method. Methods. An ideal cemented stem with bone was made using three dimensional FE analyses (ANSYS 13). The cortical bone was 105 mm long and 7 mm thick and the PMMA cement mantle was 5 mm in thickness surrounding the stem. Young's modulus was set at 200 GPa for the bone and 2.2 GPa for the cement. Poisson's ratio was 0.3 for both materials. The
Cement-induced thermal osteonecrosis is well documented, as is the potential for nerve injury from thermal energy. Cement is often used to augment fixation following excision of humeral metastases. Porcine femurs were used as a model. We sought to find out the maximum temperatures that would be reached in various parts of the bone during the cement setting process, to explore what negative effects this might have on neighbouring bone and nerve. A 12mm by 12mm window was cut from 12 porcine femoral shafts, and Palacos R+D cement injected into the defect. As cement set, bone surface temperature was measured using infra-red thermal imaging and thermocouples used to measure temperatures at the
Introduction. The use of antibiotic-loaded polymethylmethacrylate
For as long as surgeons have been performing total and partial knee arthroplasty, surgeons have debated the efficacy, safety, and requirement of a pneumatic tourniquet. Advocates claim that blood loss is less, visualization is improved, and the cement technique is better with the use of a tourniquet. Others would argue that the use of the tourniquet or limited tourniquet use is safer, does not increase blood loss, and does not compromise visualization and cementing technique. Multiple meta-analyses have been performed that provide very little true evidence of superiority. One such study from Yi et al, concludes that the use of the tourniquet reduces surgical time, intraoperative and total blood loss, but increases postoperative total blood loss. They also conclude that DVT and SSI are “relatively augmented” with use. There may be issues with the timing of tourniquet release in these pooled studies, with others stating that releasing the tourniquet prior to wound closure, supposedly for hemostasis, significantly increases the total and calculated blood loss. Huang et al report that with proper control in the amount of pressure, a debatable topic in and of itself, and shorter duration of inflation, release after closure can reduce blood loss without increased complications. One additional issue is patellar tracking, and the need to lateral release. The tourniquet significantly affects assessment of tracking and the need for lateral release, potentially causing the surgeon to unnecessarily perform a lateral release with the tourniquet inflated. Lastly, research has suggested that using a tourniquet may affect recovery of lower extremity strength and function. Dennis et al compared quadriceps strength and found that use of the tourniquet resulted in “slightly” lower strength postoperatively out to 3 months. The fatal flaw in this study and others is that there is no accepted minimal clinically important difference for quad function, and thus they powered their study to detect a difference of 12 Nm, and the actual difference, while statistically significant, did not even meet their arbitrary power set point. Thus, while strength may be slightly impaired by the use of a tourniquet, it was not different enough to meet their criteria. Additionally, in their study, 64% of the “no-tourniquet” knees actually had a tourniquet used for cementation to “minimise blood at the
Over a four year period of time, 142 consecutive hip revisions were performed with the use of an extended proximal femoral osteotomy. Twenty patients had insufficient follow-up or were followed elsewhere and were excluded from the review. The remaining 122 revisions included 83 women and 39 men. Average age at time of revision was 63.8 (26–84) years. Indications for revision were aseptic loosening (114), component failure (4), recurrent dislocation (2), femoral fracture (1) and second stage re-implantation for infection (1). The extended proximal femoral osteotomy gave easy access to the distal
The use of stems in revision TKA enhances implant stability and thus improves the survival rate. Stemmed components obtain initial mechanical stability when there is deficient metaphyseal bone. However the optimal method of stem fixation remains controversial, which includes selection of stem size, length or the use of cemented vs. cementless stems. Although postulated by many surgeons, there is no sufficient evidence, that cementless or hybrid fixation does perform better in the long term outcome, than cemented stems. In addition a number of studies, even from the U.S., suggested that there might be a benefit for the long term survival for cemented stems in revision TKA. Obviously cemented stems have some few advantages in revision set up as: topic antibiotic delivery and initial strong fixation. While main disadvantages arise during limited/poor bone quality for initial cancellous
Wear testing of THR has chaperoned generations of improved UHMWPE bearings into wide clinical use. However, previous in vitro testing failed to screen many metal-on-metal hips which failed. This talk tours hip wear testing and associated standards, giving an assortment of THR wear test results from the author's laboratory as examples. Two international hip wear-simulator standards are used: ISO-14242-1 (anatomic configuration) and ISO-14242-3 (orbital-bearing). Both prescribe 5 million (MC) force-motion cycles involving cross-shear synchronized with compression simulating walking gate of ideally aligned THRs. ISO-14242-1 imposes flexion (flex), abduction-adduction (ad-ab) and internal-external (IE) rotations independently and simultaneously. An orbital-bearing simulator more simply rotates either a tilted femoral head or acetabular component, switching from flexion-dominated to ad-ab-dominated phases in each cycle with some IE. In the latter, the acetabular component is typically placed below the femoral head to accentuate abrasive conditions, trapping third-body-wear debris. Wear is measured (ISO-14242-2) gravimetrically (or volumetrically in some hard-on-hard bearings). Wear-rate ranges from negligible to >80mg/MC beyond what causes osteolysis. This mode-1 adhesive wear can therefore “discriminate” to screen hip designs-materials in average conditions. Stair-climbing, sitting, squatting and other activities may cause THR edge-loading and even impingement with smaller head-to-neck ratios or coverage angle, naturally worse in metal-on metal hips. Deformation of thin acetabular components during surgical impaction may cause elevated friction or metal-metal contact, shedding more metal-ions and accelerating failure. Surgical misalignments in inclination angle, version and tilt can make this worse, even during modest activities in hard-on-hard bearings. Abrasive particulate debris from bone or
Bone cement reaches high temperatures while polymerising. Bone has been shown to be sensitive to thermal injury with osteonecrosis reported after one minute at 47°C. Necrosis during cementing might compromise the
