The DuPuy Sigma total knee arthroplasty (TKA) is a modification of the well-established Press Fit Condylar (PFC) TKA and is used extensively in the UK and worldwide. This study reports the first 10-year clinical and radiological follow-up data for the Sigma PFC. A total of 235 consecutive Sigma TKAs were performed in 203 patients between October 1998 and October 1999, in our unit. Patients were seen at a specialist nurse-led clinic 1 week before admission and at 6 months, 18 months, 3 years, 5 years and 7-10 years after surgery. Data was recorded prospectively at each clinic visit. Of 235 knees, 171 (147 patients) were alive at 10 years. Twelve were lost to follow up. Eight knees (3.4%) were revised; four for infection and four underwent isolated change of polyethylene insert. Ten-year survival with an end point of revision for any reason was 95.9%, and with an endpoint of revision for aseptic failure was 98.7%. The mean American Knee Society score was 62 at 8-10 years compared with 31 out of 100 pre-operatively. Our results show that the PFC Sigma knee arthroplasty performs well over the first 10 years post-implantation

Introduction. When using press-fit stems in revision total knee arthroplasty (TKA), diaphyseal engagement optimizes stability. Attempts to maximize press fit may lead to periprosthetic fracture; however, the literature offers no guidance regarding the prevalence or management of this complication. The purpose of this study is to report the incidence, risk factors, and outcomes of these fractures. Methods. 634 Stemmed implants (307 femoral and 327 tibial) from 413 consecutive revision TKAs were reviewed. Immediate and 6 week post-operative radiographs were examined. Patient age, gender, stem length, diameter, and offset were evaluated as potential risk factors for fracture occurrence using a paired t-test for continuous and a chi-square analysis for categorical variables. Results. 15 Periprosthetic fractures (2.4%) were identified including two femoral (0.65%) and 13 tibial (4.0%). 10 Fractures were non-displaced, 3 had cortical displacement <2mm, and 2 were displaced >2mm. 1 Femur fracture was recognized and fixed intra-operatively with cables. 11 patients with non or minimally displaced fractures were allowed to bear weight as tolerated and 2 were protected for 2 weeks. 1 Displaced fracture was braced for 3 months, while the other was casted for concomitant extensor allograft reconstruction. All fractures showed radiographic evidence of healing and all patients were able to painlessly bear weight within 6 months. There was no evidence of implant migration at a mean of 15 months (range 3-47 months). 1 Patient developed recurrent infection at 10 months; no other complications were identified. With the sample size available for study, no significant differences in age (p=0.09), implant parameters (p=0.06-0.85) or gender (p=0.37) were detected between the fracture and non-fracture groups. Conclusions. Periprosthetic fractures occurred in approximately 2.4% of press-fit stems in revision TKA, more commonly in the tibia than femur. All fractures were managed non-operatively without complication or loss of prosthetic fixation

We set out to demonstrate the 10-year survivorship of the PFC sigma TKA in a young patient group.

Demographic and clinical outcome data were collected prospectively at 6 months, 18 months, 3 years, 5 years and 8–10 years post surgery.

The data were analysed using Kaplan Meier survival statistics with end point being regarded as death or revision for any reason.

203 patients were found to be < 55 years at the time of surgery. Four patients required revision and four patients died. Another four patients moved away from the region and were excluded from the study.

A total of 224 knees in 199 patients (101 male and 98 females.) 168 patients had a diagnosis of Osteoarthritis and 28 with inflammatory arthritis. Average age 50.6 years range 28–55 years (median 51). Ten-year survivorship in terms of revision 98.2% at ten years 95% confidence interval.

Our results demonstrate that the PFC Sigma knee has an excellent survival rate in young patients over the first 10 years. TKR should not be withheld from patients on the basis of age.

The PFC Sigma Cobalt Chrome Sigma (PFCSCC) was introduced in 2006, an update of the PFC Sigma designed to reduce backside wear. To help identify any significant early failures following its introduction, we prospectively identified all recipients over a one-year period. The patient's clinical, demographic and radiographic data, American Knee Society scores (AKSS), Oxford Knee scores (OKS) and SF-12 scores was recorded pre-operatively and at one, three and five years. 233 patients underwent 249 primary knee arthroplasties with the PFCSCC. Seventeen patients (19 knees) died and 29 patients (30 knees) were also lost to follow up at the five year point. The mean age was 66.6 (34–80) with 47.6% of the cohort being male. The mean five year follow-up was 1836 days (1530–2307). Five knees (2.2%) were revised for infection and three were revised for pain. The 5–year cumulative survival rate was 96.6% for any failure and 98.6% for aseptic failure. AKSS 32.6 (0–86.6) preoperatively, 80.7 (29–95) 5 years P < 0.001. OKS was 39.0 (22–53) preoperatively, 23.5 (4.7–42.3) 5 years P < 0.001. These results demonstrate a good early survivorship when compared to the old design PFC Sigma, however further follow-up to ten years is required.

The present clinico-radiographical study evaluated the long term performance of a Ti-Al-V alloy cementless modular press-fit cups (Fitek™) having, on the outer surface, an oriented multilayer titanium mesh (Sulmesh™) with 65% tridimensional porosity and 2 fins applied to the outer surface. Fins were initially designed for anti-rotatory purposes but showed to give an excellent initial mechanical stability. Thus, in the following years, we have designed 2 other cups having 8 fins and ceramic insert. In this paper we compare the design and the results obtained with these 3 cups.

We have reviewed the first 100 consecutive FITEK cups implanted in 92 patients with an average FU of 9,7 years (range 9-11 years). Results were evaluated with the Harris score. We had 86 Excellent, 10 Good, 2 Fair and 2 Poor. In this series we always used 28 mm heads.

Dysplastic patients showed inferior results compared to arthritics patients in different parameters, as pain, limp, ROM (p < 0.05), putting socks and shoes (p < 0.05).

Radiographically, our cups were implanted in a fairly horizontal position (36.5° an average).

At the last FU radiolucent lines were present in 14 % of the cases, never progressive.

In no case we found a change of position of the cup, and in this series no revision was necessary.

Between 2005 and 2008 we have implanted 140 consecutive Delta Fins cups with ceramic-on-ceramic articulation. The fins of this cup have a trapezoidal shape, with HA coating. The cup has an interference of 2 mm. The Delta ceramic insert allows the use of 32 or 36 mm heads.

Clinico-radiographical results were very good. One cup needed to be revised for aseptic loosening consecutive to a surgical error (undersizing)

The H.M.S. cup is made of Porous Titanium with 8 fins having a triangular section, in order to increase their penetration into cortical bone. The ceramic insert allows even larger ceramic insert (32, 36 and 40). Preliminary clinico-radiographical results were excellent, with complete initial mechanical stability and great ROM due to the large ceramic heads.

The presence of fins on the outer surface of cementless cups enhances primary stability and fixation and the use of large ceramic heads improves ROM and subjective patients satisfaction.

Restoration a joint's articular surface following degenerative or traumatic pathology to the osteochondral unit pose a significant challenge. Recent advances have shown the utility of collagen-based scaffolds in the regeneration of osteochondral tissue. To provide these collagen scaffolds with the appropriate superstructure novel techniques in 3D printing have been investigated. This study investigates the use of polyɛ-caprolactone (PCL) collagen scaffolds in a porcine cadaveric model to establish the stability of the biomaterial once implanted. This study was performed in a porcine cadaveric knee model. 8mm defects were created in the medial femoral trochlea and repaired with a PCL collagen scaffold. Scaffolds were secured by one of three designs; Press Fit (PF), Press Fit with Rings (PFR), Press Fit with Fibrin Glue (PFFG). Mobilisation was simulated by mounting the pig legs on a continuous passive motion (CPM) machine for either 50 or 500 cycles. Biomechanical tensile testing was performed to examine the force required to displace the scaffold. 18 legs were used (6 PF, 6 PFR, 6 PFFG). Fixation remained intact in 17 of the cohort (94%). None of the PF or PFFG scaffolds displaced after CPM cycling. Mean peak forces required to displace the scaffold were highest in the PFFG group (3.173 Newtons, Standard deviation = 1.392N). The lowest peak forces were observed in the PFR group (0.871N, SD = 0.412N), while mean peak force observed in the PF group was 2.436N (SD = 0.768). There was a significant difference between PFFG and PFR (p = 0.005). There was no statistical significance in the relationship between the other groups. PCL reinforcement of collagen scaffolds provide an innovative solution for improving stiffness of the construct, allowing easier handling for the surgeon. Increasing the stiffness of the scaffold also allows press fit solutions for reliable fixation. Press fit PCL collagen scaffolds with and without fibrin glue provide dependable stability. Tensile testing provides an objective analysis of scaffold fixation. Further investigation of PCL collagen scaffolds in a live animal model to establish quality of osteochondral tissue regeneration are required

Durable humeral component fixation in shoulder arthroplasty is necessary to prevent painful aseptic loosening and resultant humeral bone loss. Causes of humeral component loosening include stem design and material, stem length and geometry, ingrowth vs. ongrowth surfaces, quality of bone available for fixation, glenoid polyethylene debris osteolysis, exclusion of articular particulate debris, joint stability, rotator cuff function, and patient activity levels. Fixation of the humeral component may be achieved by cement fixation either partial or complete and press-fit fixation. During the past two decades, uncemented humeral fixation has become more popular, especially with short stems and stemless press fit designs. Cemented humeral component fixation risks difficult and complicated revision surgery, stress shielding of the tuberosities and humeral shaft periprosthetic fractures at the junction of the stiff cemented stem and the remaining humeral shaft. Press fit fixation may minimise these cemented risks but has potential for stem loosening. A randomised clinical trial of 161 patients with cemented vs. press fit anatomic total shoulder replacements found that cemented fixation of the humeral component provided better quality of life, strength, and range of motion than uncemented fixation but longer operative times. Another study found increased humeral osteolysis (43%) associated with glenoid component loosening and polyethylene wear, while stress shielding was seen with well-fixed press fit humeral components. During reverse replacement the biomechanical forces are different on the humeral stem. Stem loosening during reverse replacement may have different factors than anatomic replacement. A systemic review of 41 reverse arthroplasty clinical studies compared the functional outcomes and complications of cemented and uncemented stems in approximately 1800 patients. There was no difference in the risk of stem loosening or revision between cemented and uncemented stems. Uncemented stems have at least equivalent clinical and radiographic outcomes compared with cemented stems during reverse shoulder arthroplasty. Durable humeral component fixation in shoulder arthroplasty is associated with fully cemented stems or well ingrown components that exclude potential synovial debris that may cause osteolysis

Since 1997, a patented rim flared cup has been used for both primary and revision total hip arthroplasty with great success. The concept was based on a “stretched” hemispherical geometry to improve initial contact between cup and bone. This improved geometry provided a 1 mm press fit predominantly at the perimeter of the acetabulum much like the footprint of the native anatomic acetabulum. Thousands of these were implanted. A second version of this concept was introduced in August 2011. This similarly “stretched” geometry provides 1.6 mm of press fit. Building on what was learned from the original design, this updated, stretched geometry was created with a single radius for a smooth transition from the apex to the peripheral press fit. Porous coating is the key to implant durability. With this aggressive “sticky” porous coating, only 0.6 mm of press fit is required. This porous coating has 60% porosity, and 150–400 mm pore size. It has a tensile strength of 5000 psi (The FDA requires a minimum of 2900 psi) and a mean thickness of 0.8 mm. Three thousand cups have been implanted with the author contributing 400. In our own primary subgroup done in 2014–15, 142 had 2–4 year follow up with zero loosening. There was one infection and 2 dislocations. One implant was revised on a patient with psoas tendonitis from an oversized cup. At retrieval it showed excellent ingrowth into the porous coating with 38% ingrowth. This graduated rim fit concept has a proven track record spanning 2 decades and provides a stable and reproducible acetabular construct

Introduction. Primary stability is achieved by the press fit technique, where an oversized component is inserted into an undersized reamed cavity. The major geometric design of an acetabular shell is hemispherical type. On the other one, there are the hemielliptical type acetabular shells for enhanced peripheral contact. In the case of developmental dysplasia of the hip (DDH), the aseptic loosening may be induced by instability due to decreased in the contact area between the acetabular shell and host bone. The aim of this study was to assess the effect of reaming size on the primary stability of two different outer geometry shells in DDH models. Materials and methods. The authors evaluated hemispherical (Continuum Acetabular Shell, Zimmer Biomet G.K.) and hemielliptical (Trabecular Metal Modular Acetabular Shell, Zimmer Biomet G.K.) acetabular shells. Both shells had a 50 mm outer diameter and same tantalum 3D highly porous surface. An acetabular bone model was prepared using a solid rigid polyurethane foam block with 20 pcf density (Sawbones, Pacific Research Laboratories Inc.) as a synthetic bone substrate. Press fit conditions were every 1 mm from 4 mm under reaming to 2 mm over reaming. To simulate the acetabular dysplasia the synthetic bone substrate was cut diagonally at 40°. Where, the acetabular inclination and cup-CE angle were assumed to 40° and 10°, respectively. Acetabular components were installed with 5 kN by a uniaxial universal testing machine (Autograph AGS-X, Shimadzu Corporation). Primary stability was evaluated by lever-out test. The lever-out test was performed in 4 mm undersized to 2 mm oversized reaming conditions. Lever out moment was calculated from the multiplication of the maximum load and the moment arm for primary stability of the shell. The sample size was 6 for each shell type. Results. The hemisphererical acetabular shell had the maximum lever out moment in 3 mm under reaming condition (7.4 ± 0.4 N·m). The hemielliptical acetabular shell had the maximum lever out moment in 1 mm under reaming condition (8.7 ± 0.8 N·m). Furthermore, the lever out moment of the hemielliptical acetabular shell was significantly 1.2 times greater by the t-test than the hemispherical acetabular shell under the maximum primary fixation conditions. Discussion. The risk parameter of the acetabular loosening is indicated the lack of lateral bony support. The hemielliptical shell was not adversely effected more than the hemispherical shell. Furthermore, the reaming condition of the most primary fixation on the hemielliptical shell was 1 mm under reaming, and was a more general operating procedure than the hemispherical shell (3 mm under reaming). From this study, it was suggested that the hemielliptical shell might be expected excellent clinical outcomes in severe acetabular dysplasia hips. For any figures or tables, please contact authors directly

A well designed constrained liner does not have a “hood” nor a wide poly brim that extends beyond the metal shell because these cause impingement. The failure of a good design is almost always technique. Size the liner so the poly is press fit against the metal rim of the cup. Cement thickness does not matter. Remove any derotation tabs on metal rim with a carbide burr so there is a firm press fit with no toggle. Do NOT angle the poly to change the anteversion. Use the carbide burr to scratch the inner surface of the cup and a soft tissue burr to scratch the backside of the poly. Cement must be liquid enough to fully seat the poly against the metal rim. If cement too doughy it resists full seating. Put metal ring in groove during implantation and cementing to prevent cement into the groove. If this is a primary cup use screws with the cup or cement the poly into the acetabular bone. Dry the head and inner surface of the poly to facilitated reduction. Align the head concentrically into the mouth of the poly and push simultaneously on the knee and over the greater trochanter

The “keel” is the relatively short part of the undersurface of the tibial component that extends into the medullary canal. Most knee replacement systems have the capacity to attach modular stem extensions for enhanced intra-medullary fixation for revision. Diaphyseal length, large diameter stems may also guide positioning of trial components and are ideal for accurate surgical technique, even if fully cemented stems are eventually implanted. Smaller diameter non-modular stem extensions may be used for fully cemented fixation. They do not however guide component position very accurately and do not make sense for uncemented fixation. Revision surgery is different from primary surgery and enhanced fixation with some type of intramedullary fixation is highly appropriate, especially if constrained devices might be required. Options for enhanced intramedullary fixation are: 1. Fully cemented metaphyseal or shorter stems; 2. Diaphyseal engaging press fit stems; and 3. Very short fully cemented stems with trabecular metal cone fixation. Metaphyseal length press fit stems do not provide reliable fixation in revision TKA. Revision with primary components or constrained components without any stem extension is not advised

Introduction. The number of total hip replacements (THR) increased around 3.5% by year in last decade. Osteoarthritis is the most important disease in the hip, with a prevalence of 10% in the older population (>85 years), according to the Swedish THA Register. THR have been increasing in last years, mainly in young patients between 45 to 59 years old. This type of patients needs a long term solution to prevent hip revision. Two commercial solutions for young patients, the resurfacing prosthesis and press fit one, were analysed in the present study by experimental and numerical models. Methods. Two synthetic left models of composite femur (Sawbones. ®. , model 3403), which replicates the cadaveric femur, and two composite pelvic bones were used to introduce two Comercial models of Hip resurfacing (Birmingham model) and Press-fit stem (Laffit Selft –locking stem press-fit model). The commercial hip stems were chosen according to the femurs head size (resurfacing) and the femur size to press-fit Hip stem. Then, they were introduced by an experimented surgeon. The experimental set-up was applied according to a system defined previously by Ramos et al. (2013). Numerical models were implemented by replicating the experimental tests. A 3D scanning was used to identify the stem position in each model. The properties of cortical and cancel bone and hip prosthesis were also taken into account by these models. Contact was established in the interfaces for both press-fit solutions. The femur rotates distally and Pelvic moves up and down according model changes, in order to guarantee models with the same boundary conditions. Results. The numerical models were already validated experimentally using different loading conditions. Results from numerical models, present different distribution in the two commercial solutions in comparison to intact articulation (Figure 1). The medial aspect is the most critical in the femur. The resurfacing hip presents a closer behavior than the intact femur at proximal region. The press-fit hip presents a strain reduction in proximal region, which promotes the bone loss observed in clinical cases. The changes in the contact Hip joint for commercial solutions modify strain distribution distally, in all femur aspects. The press fit solution increase the bending in medial aspect

Periprosthetic fractures in total hip arthroplasty lead to considerable morbidity in terms of loss of component fixation, bone loss and subsequent function. The prevention, early recognition and appropriate management of such fractures are therefore critical. The pathogenesis of periprosthetic factors is multi-factorial. There are a number of intrinsic patient influences such as bone stock, biomechanics and compliance. There are also a host of extrinsic factors over which the surgeon has more control. The prevention of periprosthetic fractures requires careful pre-operative planning and templating, the availability of the necessary expertise and equipment, and knowledge of the potential pitfalls so that these can be avoided both intra-operatively and in follow-up. The key issues here are around identifying the risk, choosing the correct implant, understanding the anatomy, understanding the possible risks and avoiding them and using appropriate technique. There are a number of recognized risk factors for periprosthetic hip fractures. The prevalence of intra-operative fractures during total hip arthroplasty is higher in the patient with osteopenia/osteoporosis. Other conditions causing increased bone fragility, such as osteomalacia, Paget's disease, osteopetrosis, and osteogenesis imperfecta are also at a higher risk of intra-operative fracture. The use of more and more press fit cementless components has also increased the number of periprosthetic femoral fractures because of the force required to obtain such a fit. Complex deformities of the proximal femur, particularly when associated with a narrow medullary canal, as seen in secondary degenerative joint disease following developmental dysplasia of the hip may also increase the risk of intra-operative fractures. Revision surgery is associated with a higher risk of intra-operative fracture than primary hip replacement surgery. These fractures typically occur during hip dislocation, cement extraction, or reaming through old cement. Other risk factors for post-operative femoral fractures include loosening of the prosthesis with cortical bone loss, local osteolysis, stress risers within the cortex, such as old screw holes, the ends of plates, or impingement of a loose stem against the lateral femoral cortex. Periprosthetic acetabular fractures are increasingly recognized. This is in part due to the popularity of press fit components, which increase fracture risk both at the time of insertion and later due to medial wall stress shielding and pelvic osteolysis, and partly due to the increasing frequency of severe defects encountered at the time of revision surgery. Both over- and under-reaming are significant risk factors for acetabular fractures during total hip replacement. It is imperative to deal with the osteopenic patient gently and appropriately, being aware of the rim on the acetabular side and having the capacity for screw fixation where needed, having an understanding of where you wish to place your components and creating the appropriate runways for them, thinking about the stability of an implant as it is inserted and understanding that an implant that is less stable than expected probably is associated with either a size mismatch, a fracture or an implant that will not sit properly probably requires more or a different direction of reaming rather than harder blows with a hammer. A typical example where extra care is required is the scenario of a fractured neck of femur that requires total hip arthroplasty. The virgin native acetabulum in a patient likely to have some bony deficiency may be more difficult to deal with as it has a higher fracture risk. Pre-operative templating helps to identify the correct entry point for preparation of the lateral runway for linear insertion of a femoral stem. If resistance is met during insertion, the situation should be re-appraised to ensure that the direction and level of the rasp and prosthesis are the same. This reduces the risk of varus/valgus positioning which increases the risk of intra- and post-operative fractures. It is also important to avoid a change of version during insertion of the prosthesis as this can lead to high stresses

INTRODUCTION. Precise determination of material loss is essential for failure analysis of retrieved hip cups. To determine wear, the measured geometry of the retrieval hast to be compared to its pristine geometry, which usually is not available. There are different approaches to generate reference geometries to approximate the pristine geometry that is commonly assumed as sphere. However, the geometry of press fit cup retrievals might not be spherical due to deformation caused by excessive press-fitting. The effect of three different reference geometries on the determined wear patterns and material loss of pristine and worn uncemented metal-on-metal hip cups was determined. METHODS. The surfaces of two cups (ASR, DePuy, Leeds; one pristine, one a worn retrieval) were digitized using a coordinate measurement machine (CRYSTA-Apex S574, Mitutoyo; 3 µm accuracy). Both cups were measured undeformed and while being deformed between a clamp. Three different methods for generating reference geometries were investigated (PolyWorks|Inspector 2018, InnovMetric). Method 1: A sphere with the nominal internal cup dimensions was generated. Method 2: A sphere was fitted to the measured data points after removing those from worn areas (deviation > 3 µm is defined as wear) to eliminate the influence of manufacturing tolerances on the nominal diameter. Method 3: Measurements, which displayed visual deformation in the computed wear pattern based on the best fit sphere, were fitted with an ellipsoid. The direction of the deformation axes and the amount of deformation were used to scale the best fit ellipsoid. Linear wear was calculated from the distance of the respective reference geometry to the measured point cloud. Finally, material loss is defined as the difference in volume of the reference geometry and the measured geometry. RESULTS. The method used for generating the reference geometry affected the determined wear greatly. Using the nominal manufacturing radius (larger than the best fit radius) for the worn cup falsely indicates deposit. This leads to approx. 39 % less wear volume compared to the best fit sphere analysis. Using an ellipsoid as reference geometry for both deformed cups improves the determination of the wear pattern and indicates areas of material loss better than a reference sphere. Additionally, the mistake in material loss determination is decreased, especially for the worn cup almost exactly to the wear volume analyzed with the best fit sphere before deformation. DISCUSSION. For correct determination of material loss best fit geometries instead of nominal sizes have to be used to compensate the differences due to manufacturing tolerances. Furthermore, deformation always has to be eliminated to generate correct wear patterns and volumes. Using an ellipsoid as reference geometry improves the outcome. For generating an even more accurate reference geometry, the exact behavior of the cup during deformation must be understood. Limitations to this method are cups that do not provide pristine areas in order to generate an appropriate best fit geometry. For any figures or tables, please contact authors directly

Arthroplasty implant modularity enables the surgeon to adapt the joint replacement construct to the patient's requirements, and often facilitates revision procedures. Total shoulder arthroplasty humeral modularity exists for many implant systems. Glenoid modularity with convertibility between anatomic and reverse shoulder arthroplasty is a recent development. Glenoid modularity is very useful when reconstructing glenoid bone deficiencies, or in providing a method for reverse shoulder arthroplasty joint lateralization. The live surgery will demonstrate a bio-reverse total shoulder arthroplasty (bRTSA). The humeral component is a modular press fit stem that can accommodate either reverse or anatomic metaphyseal components. The metaphyseal components can be exchanged without removing the stem or changing the humeral height. The glenoid base has three components. The trabecular titanium peg is available in two diameters, and four lengths for each diameter. The peg is fixed to a metal base plate via Morse taper. In revision settings, these components can be easily dissociated in situ, and a coring drill inserted over a well-fixed peg allows removal with minimal bone loss. Either a polyethylene component, or glenosphere can be attached to the baseplate to complete the glenoid construct. An innovative set of instruments have been developed to reliably prepare the glenoid and humeral bone graft. While the live surgery will demonstrate the grafting technique in a bRTSA, it can also be used to reconstruct glenoid deficiencies (eg, Walch B2). Implants have been developed to solve these issues, but often do so at the expense of very limited glenoid bone stock. Bone grafting actually creates a net increase in glenoid bone stock that may improve implant durability, and decrease revision complexity. The technique is quite simple and adds approximately ten minutes to operative time. I have used this technique for 5 years with no cases of graft failure

Periprosthetic fractures around the femur during and after total hip arthroplasty (THA) remain a common mode of failure. It is important therefore to recognise those factors that place patients at increased risk for development of this complication. Prevention of this complication, always trumps treatment. Risk factors can be stratified into: 1. Patient related factors; 2. Host bone and anatomical considerations; 3. Procedural related factors; and 4. Implant related factors. Patient Factors. There are several patient related factors that place patients at risk for development of a periprosthetic fracture during and after total hip arthroplasty. Metabolic bone disease, particularly osteoporosis increases the risk of periprosthetic fracture. In addition, patients that smoke, have long term steroid use or disuse, osteopenia due to inactivity should be identified. A metabolic bone work up and evaluation of bone mineralization with a bone densitometry test can be helpful in identifying and implementing treatment prior to THA. Pre-operative Host Bone and Anatomic Considerations. In addition to metabolic bone disease the “shape of the bone” should be taken into consideration as well. Dorr has described three different types of bone morphology (Dorr A, B, C), each with unique characteristics of size and shape. It is important to recognise that not one single cementless implant may fit all bone types. The importance of templating a THA prior to surgery cannot be overstated. Stem morphology must be appropriately matched to patient anatomy. Today, several types of cementless stem designs exist with differing shape and areas of fixation. It is important to understand via pre-operative templating which stem works best in what situation. Procedural Related Factors. There has been a resurgence in interest in the varying surgical approaches to THA. While the validity and benefits of each surgical approach remains a point of debate, each approach carries with it its own set of risks. Several studies have demonstrated increased risk of periprosthetic fractures during THA with the use of the direct anterior approach. Risk factors for increased risk of periprosthetic fracture may include obesity, bone quality and stem design. Implant Related Factors. As mentioned there are several varying cementless implant shapes and sizes that can be utilised. There is no question that cementless fixation remains the most common mode of fixation in THA. However, one must not forget the role of cemented fixation in THA. Published results on long term fixation with cemented stems are comparable if not exceeding those of press fit fixation. In addition, the literature is clear that cemented fixation in the elderly hip fracture patient population is associated with a lower risk of periprosthetic fracture and lower risk of revision. The indication and principles of cemented stem fixation in THA should not be forgotten

The unacceptable failure rate of cemented femoral revisions led to many different cementless femoral designs employing fixation in the damaged proximal femur with biological coatings limited to this area. The results of these devices were uniformly poor and were abandoned for the most part by the mid-1990's. Fully porous coated devices employing distal fixation in the diaphysis emerged as the gold standard for revisions with several authors reporting greater than 90% success rate 8–10 years of follow-up. Surgical techniques and ease of insertion improved with the introduction of the extended trochanteric osteotomy as well as curved, long, fully porous coated stems with diameters up to 23mm. The limits of these stems were stretched to include any stem diameter in which even 1–2cm of diaphyseal contact could be achieved. When diaphyseal fixation was not possible (Type IV), the alternatives were either impaction grafting or allograft prosthetic composite (APC). As the results of fully porous coated stems were very carefully scrutinised, it became apparent that certain types of bone loss did not yield the most satisfactory results both clinically and radiographically. When less than 4cm of diaphyseal press fit (Type IIIB) was achieved, the mechanical failure rate (MFR) was over 25%. It also became apparent that even when there was 4–6cm diaphyseal contact (Type IIIA), and the stem diameter was 18mm or greater, post-operative pain and function scores were significantly less than those with smaller diameter stems. This was probably due to poorer quality bone. Many of these Type IIIA and Type IIIB femurs had severe proximal torsional remodeling leading to marked distortion of anteversion. This made judging the amount of anteversion to apply to the stem at the time of insertion very difficult, leading to higher rates of dislocation. These distortions were not present in Type I and Type II femurs. This chain of events which was a combination of minimal diaphyseal fixation, excessively stiff stems and higher dislocation rates led to the conversion to modular type stems when these conditions existed. For the past 13 years, low modulus taper stems of the Wagner design have been used for almost all Type IIIA and Type IIIB bone defects. The taper design with fluted splines allows for fixation when there is less than 2cm of diaphysis. The results in these femurs even with diameters of up to 26mm have led to very low MFRs and significantly less thigh pain. Independent anteversion adjustment is also a huge advantage in these modular stems. Similar success rates, albeit with less follow-up, have been noted in Type IV femurs

Introduction. Cementless total knee arthroplasty (TKA) designs are clinically successful and allow for long term biological fixation. Utilizing morselized bone to promote biological fixation is a strategy in cementless implantation. However, it is unknown how bone debris influences the initial placement of the tray. Recent findings show that unseated tibia trays without good contact with the tibial resection experience increased motion. This current study focuses on the effect of technique and instrument design on the initial implantation of a cementless porous tibia. Specifically, can technique or instrument design influence generation of bone debris, and thereby change the forces required to fully seat a cementless tray with pegs?. Methods. This bench top test measured the force-displacement curve during controlled insertion of a modern cementless tibia plate with two fixation pegs. A total of nine pairs of stripped human cadaver tibias were prepared according to the surgical technique. However, the holes for the fixation pegs were drilled intentionally shallow to isolate changes in insertion force due to the hole preparation. A first generation instrument set (Instrument 1.0) and new instrument set design (Instrument 2.0), including a new drill bit designed to remove debris from the peg hole, were used. The tibias prepared with Instrument 1.0 were either cleaned to remove bone debris from the holes or not cleaned. The tibias prepared with the Instrument 2.0 instruments were not cleaned, resulting in three groups: Instrument 1.0 (n=7), Instrument 1.0 Cleaned (n=5), and Instrument 2.0 (n=6). Following tibia resection and preparation of holes for the fixation pegs, the tibias were cut and potted in bone cement ensuring the osteotomy was horizontal. The tibial tray was mounted in a load frame (Enduratec) and the trays were inserted at a constant rate (0.169mm/sec) while recording the force. The test was concluded when the pegs were clearly past the bottom of the intentionally shallow holes. Results. The force-displacement curves from this method were dependent on the instrument used and cleaning of the holes. Instrument 2.0 specimens were inserted about 2 mm past the maximum peg depth before experiencing a significant increased resistance. The Instrument 1.0 Cleaned holes saw an increase in force slightly past the maximum peg depth, while the Instrument 1.0 group saw increase in force around 1 mm before reaching the maximum peg depth. The average insertion force required to reach maximum peg depth was significantly higher (p<0.05) for the Instrument 1.0 group (790.7 N, sd=185.9) than both the Instrument 1.0 Cleaned (429.7 N, sd=116.8) and the Instrument 2.0 group (580.4 N, sd=89.3). The insertion forces at a ‘mid-tunnel’ location, before the increase in resistance, were not affected by drill design as the drill diameters were the same, resulting in the same press fit. Conclusions. Bone debris in fixation feature holes increases the force to fully seat a cementless tibia plate. This suggests there is a cost to leaving morselized bone in place. Removing bone debris through instrument design or surgical technique can ensure that a tibial plate is fully seated at time of implantation, maximizing initial fixation

Intra-operative fractures of the femur are on the rise mainly due to the increased use of cementless implants and the desire to get a tight press fit. The prevalence has been reported to be between 1–5% in cementless THAs. The key to preventing these fractures is to identify patients at high risk and careful surgical technique. Surgical risk factors include the use of cementless devices, revision hip surgery, the use of flat tapered wedges and MIS surgery. Patient factors that increased risk include increasing age, female gender, osteopenia and rheumatoid arthritis. These risk factors tend to be additive and certainly when more than one is present extra caution needs to be taken. Surgical technique is critical to avoid these intra-operative fractures. Fractures can occur during exposure and dislocation, during implant removal (in revision THA), during canal preparation and most commonly during stem insertion. In both primary, and especially in revision, THA be wary of the stiff hip in association with osteopenia or osteolysis. These patients require a very gentle dislocation. If this cannot be achieved, then alteration of the standard approach and dislocation may be needed. Examples of these include protrusion with an osteopenic femur and revision THA with a very stiff hip with lysis in the femur. Lastly, in cases with retained hardware, dislocate prior to removing plates and screws. After dislocation, the next challenge is gentle preparation of the femoral canal. A reasonable exposure is required to access the femoral canal safely. MIS procedures do not offer good access to femoral canal and this probably results in increased risk of fracture during broaching or implant insertion. When broaching, stop when broach will not advance further. When inserting a tapered wedge stem, be worried if stem goes further in than broach. In revision surgery, when taking the stem out from above, make sure the area of the greater trochanter does not overhang the canal. A high speed burr can clear the shoulder for easier access for removal. In revision THA with an ETO, place a cerclage wire prior to reaming and retighten prior to stem insertion. Even with careful surgical technique intra-operative femoral fractures will still occur. When inserting the stem, a sudden change in resistance is highly suggestive of fracture. Wide exposure of the entire proximal femur is necessary to confirm the diagnosis. The distal extent of the fracture must be seen. Only on occasion is an intra-operative radiograph needed. Management is directed to ensuring component stability and good fracture fixation. In primary total hip arthroplasty, calcar fractures are by far the most common. If using proximal fixation and you are certain the stem is stable, then all that is needed is cerclage wiring. As already mentioned, you must follow the fracture line distally so you are aware of how far down it goes. Often what appears to be a calcar split actually propagates distal to the lesser trochanter. In these cases, one would probably go for distal fixation plus wiring. In conclusion, intra-operative femoral fractures are on the rise. Prevention is the key

Purpose. Current methods for inserting a press fit hemispherical metal-backed acetabular component within the acetabula are uncontrolled, relying on the surgeon to generate the necessary forces required for sufficient introduction. While previous studies have recorded impact forces of 2–3 kN necessary to seat an acetabular cup using visual observation[1], some researchers have observed users imparting as high as 8.9 kN of force[2]. The aim of this study is to quantify the forces required to generate optimal implant primary stability, as well as compare force delivery methods. Method. The experiments were carried out using prepared bone substitute. A high frequency force sensor was rigidly mounted under the substitute to measure impact force and duration. An acetabular cup was inserted using successive reproducible impacts of varying magnitude (2.5 kg falling 17, 34, 43, 51, 68, or 85 mm). Impacts were repeated until the cup was no longer advancing. Each test recorded the number of impacts, maximum impact force, impact duration, and extraction force of the cup after insertion. The results were then compared against manual insertion (tapping) and high frequency vibratory insertion (50–500 Hz). Results. As shown in figure 1, an exponential relationship was found between the maximum impact force and cup extraction force (R. 2. = 0.97), with a mean impact force of 4200 N at full insertion. By contrast, manual insertion resulted in maximum impacts 30% greater on average, with no discernible increase in extraction force. High frequency vibratory insertion resulted in a linear relationship (R. 2. = 0.86) with a maximum extraction force of 335 N. Conclusion. Manual insertion has been shown to result in excessive force being used. This may result in additional stress to the acetabula, although additional study is needed to determine the clinical relevance. High frequency vibratory insertion has shown promise of reducing the impact forces required, with ongoing study of the effect at higher impact forces