Intra-operative complications vary from extremely benign such as glenoid vault penetration to life and limb threatening for example brachial artery injury. Most intra-operative complications can be avoided with careful pre-operative planning, anticipation, and execution. However, even the best planning and execution including fluoroscopic guided reaming cannot prevent all complications. The following intra-operative complications will be discussed in detail in regards to both prevention and management: Glenoid vault penetration, Glenoid component malposition - reverse and primary, Glenoid fracture - reverse and primary, Humeral component malposition - reverse and primary, and Humeral fracture - reverse and primary

Cement fixation of the glenoid implants in total shoulder arthroplasty has been the norm since the procedure has existed. Yet, an unacceptably high rate of lucent lines, representing prosthetic loosening, and a high rate of resultant failure of fixation of these implants continues to be the single most common cause for revision surgery in total shoulder arthroplasty. Dissatisfaction with a higher than acceptable rate of lucent lines, cement fixation of the glenoid component has led us to evaluate and employ an implant anchored into the glenoid vault with a woven tantalum (trabecular metal) fixation stem. We have employed this implant in patients with healthy bone stock with a minimum 2-year follow-up in well over 100 cases with only one revision performed in a first generation implant due to fatigue fracture. No cases have demonstrated lucency or loosening. The procedure does require meticulous attention to detail to ensure precise surface and glenoid vault preparation providing complete intraosseous seating of the trabecular metal anchor and flush apposition and support of the polyethylene surface upon the face of the glenoid. This process has reduced surgical preparation time as well as time required for cement setting by an average of 20 minutes per case

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 bone-cement interface the glenoid, implant and cement mantle stress levels. The FEA model was then utilized to make measurements while the simulating abduction with the different implant designs. The biomechanical response parameters were compared between the models at comparable retroversion correction. Results. The model prediction of force ratio for the augmented wedge design was 0.56 and for the augmented step design was 0.87. The step design had higher force ratio than the wedge one at similar conformity settings. Micromotion was defined as a combination of three components based on different directions. The distraction measured for the wedge design was 0.05 mm and for the step component, 0.14 mm. Both implants showed a similar pattern translation wise. The greatest difference between the two implants was from the compression standpoint, where the step component showed almost three times more movement than the wedge design implant. Overall, the step design registered greater micromotion than the wedge one during abduction physiologic loading. The level of stress generated during abduction on the glenoid vault was 1.65 MPa for the wedge design and 3.78 MPa for the step one. All stress levels were found below the determined bone failure limit for the bone and polyethylene (10–20 MPa). Concerning implant stress, the results measured on the backside of the wedge and step components were 6.62 MPa and 13.25 MPa, respectively. Both components showed high level of stress level measured on the cement mantle, which exceeded the endurance limit for cement fracture (4 MPa). Discussion. The augmented glenoid is a novel surgical implant for use in with severe glenohumeral osteoarthritis. Unlike standard glenoid prosthetics, the augmented glenoid is better suited for correcting moderate to severe retroversion. Whereas a step design might provide higher glenohumeral stability, the tradeoff is higher glenoid vault, implant and cement mantle stress levels, and micromotion, indicating higher risks of implant loosening, failure or fracture over time, leading to poorer clinical outcomes and higher revision rates

Background. Malposition of the glenoid component in total shoulder arthroplasty (TSA) is associated with higher strain patterns and can result in component loosening. Glenoid hardware placement and optimal size remain challenging due to the difficult joint exposure and visualization of anatomical reference landmarks during the procedure. Therefore, understanding both normal and variant patterns of glenoid anatomy is imperative for success in TSA. To better understand individual variations in glenoid morphology, this study aimed to compare the glenoid anatomy in a cohort of male and female patients from the United States (US) and Australia (AUS). Methods. Computed tomography (CT) data were analyzed from 41 male and 35 female shoulders; 39 of which were from a US population and 37 from an AUS population. These data were used to create statistical shape models (SSM) representing the average and ±1 standard deviations of the first mode of variation of each group (Materialise, Leuven, Belgium). All measurements were performed with 3-matic computer assisted design software (Materialise, Leuven, Belgium). On each model, glenoid height was measured as the distance from the most superior to the most inferior point on the glenoid face. Glenoid width was measured as the distance from the most anterior to the most posterior point on the glenoid face. Surface area was measured as the concave surface of the glenoid face (Figure 1). Glenoid vault depth was measured in the midsection of the glenoid face. Results. The overall glenoid dimensions were similar between AUS and US populations with average SSMs having widths of 24.68 and 25.72mm, heights of 34.63 mm and 34.85 mm, vault depths of 31.81 mm and 30.20 mm, and surface areas of 665.8 mm2 and 659.2 mm2 (Figure 2). All measurements were also similar for sex matched SSMs (Figure 3). We did observe differences between males and females within these populations, with males in general having larger glenoids in all parameters measured but the greatest difference was seen in surface area. Discussion. Our findings indicate that glenoid morphology is similar between these populations. This supports the external validity of previous studies of glenoid anatomy in these populations, and the use of similar implants between these groups. The gender differences observed in this study reflect previously reported differences. Interestingly, the glenoid depths were greater than the length of most commercial glenoid pegs (14–20 mm) or RSA screws (15–30 mm), indicating that implant perforation of the glenoid vault is unlikely if surgeons properly place and select appropriate sized glenoid implants in either population

For any image guided surgery, independently of the technique which is used (navigation, templates, robotics), it is necessary to get a 3D bone surface model from CT or MR images. Such model is used for planning, registration and visualization. We report that graphical representation of patient bony structure and the surgical tools, inter-connectively with the tracking device and patient-to-image registration, are crucial components in such system. For Total Shoulder Arthroplasty (TSA), there are many challenges. The most of cases that we are working with are pathological cases such as rheumatoid arthritis, osteoarthritis disease. The CT images of these cases often show a fusion area between the glenoid cavity and the humeral head. They also show severe deformations of the humeral head surface that result in a loss of contours. These fusion area and image quality problems are also amplified by well-known CT-scan artefacts like beam-hardening or partial volume effects. The state of the art shows that several segmentation techniques, applied to CT-Scans of the shoulder, have already been disclosed. Unfortunately, their performances, when used on pathological data, are quite poor. In severe cases, bone-on-bone arthritis may lead to erosion-wearing away of the bone. Shoulder replacement surgery, also called shoulder arthroplasty, is a successful, pain-relieving option for many people. During the procedure, the humeral head and the glenoid bone are replaced with metal and plastic components to alleviate pain and improve function. This surgical procedure is very difficult and limited to expert centres. The two main problems are the minimal surgical incision and limited access to the operated structures. The success of such procedure is related to optimal prosthesis positioning. For TSA, separating the humeral head in the 3D scanner images would allow enhancing the vision field for the surgeon on the glenoid surface. So far, none of the existing systems or software packages makes it possible to obtain such 3D surface model automatically from CT images and this is probably one of the reasons for very limited success of Computer Assisted Orthopaedic Surgery (CAOS) applications for shoulder surgery. This kind of application often has been limited due to CT-image segmentation for severe pathologic cases and patient to image registration. The aim of this paper is to present a new image guided planning software based on CT scan of the patient and using bony structure recognition, morphological and anatomical analysis for the operated region. Volumetric preoperative CT datasets have been used to derive a surface model shape of the shoulder. The proposed planning software could be used with a conventional localisation system, which locates in 3D and in real time position and orientation for surgical tools using passive markers associated to rigid bodies that will be fixed on the patient bone and on the surgical instruments. 20 series of patients aged from 42 years to 91 years (mean age of 71 years) were analysed. The first step of this planning software is fully automatic segmentation method based on 3D shape recognition algorithms applied to each object detected in the volume. The second step is a specific processing that only treats the region between the humerus and the glenoid surface in order to separate possible contact areas. The third step is a full morphological analysis of anatomical structure of the bone. The glenoid surface and the glenoid vault are detected and a 3D version and inclination angle of the glenoid surface are computed. These parameters are very important to define an optimal path for drilling and reaming glenoid surface. The surgeon can easily modify the position of the implant in 3D aided by 3D and 2D view of the patient anatomy. The glenoid version/inclination angle and the glenoid vault are computed for each postion in real time to help the surgeon to evaluate the implant position and orientation. In summary, preoperative planning, 3D CT modelling and intraoperative tracking produced improved accuracy of glenoid implantation. The current paper has presented new planning software in the world of image guided surgery focused on shoulder arthroplasty. Within our approach, we propose, to use pattern recognition instead of manual picking of landmarks to avoid user intervention, in addition to potentially reducing the procedure time. A very important role is played by 3D data sets to visualise specific anatomical structures of the patient. The automatic segmentation of arthritic joints with bone recognition is intended to form a solid basis for the registration. The results of this methodology were tested on arthritic patients to prove that it is not just easy and fast to perform but also very accurate so it realises all conditions for the clinical use in OR

This study examined the regional variations of cortical and cancellous bone density present in superiorly eroded glenoids. It is hypothesized that eroded regions will contain denser bone in response to localized stress. The shift in natural joint articulation may also cause bone resorption in areas opposite the erosion site. Clinical CT scans were obtained for 32 shoulders (10m/22f, mean age 72.9yrs, 56–88yrs) classified as having E2-type glenoid erosion. The glenoid was divided into four measurement regions - anterior, inferior, posterior, and superior - as well as five depth regions. Depth regions were segmented in two-millimeter increments from zero to 10 millimeters, beginning at the center of the glenoid surface. A repeated-measures multiple analysis of variance (RM-MANOVA) was performed using SPSS statistical software to look for differences and interactions between mean densities in each depth, quadrant, and between genders. A second RM-MANOVA was performed to examine effects of gender and quadrant on cortical to cancellous bone volume ratios. Significance was set at p < 0 .05. Quadrant and depth variables showed significant multivariate main effects (p 0.147 respectively). Quadrant, depth, and their interaction showed significant univariate main effects for cortical bone (p≤0.001) and cancellous bone (p < 0 .001). The lowest bone density was found to be in the inferior quadrant for cancellous bone (307±50 HU, p < 0 .001). The superior quadrant contained the highest mean density for cortical bone (895±97 HU), however it was only significantly different than in the posterior quadrant (865±97 HU, p=0.022). As for depth, it was found that cortical bone is most dense at the glenoid surface (zero to two millimeters, 892±91 HU) when compared to bone at two to eight millimeters in depth (p < 0 .02). Cancellous bone was also most dense at the surface (352±51 HU), but only compared to the eight to 10 millimeters depth (p=0.005). Cancellous bone density was found to decrease with increasing depth. For cortical-to-cancellous bone volume ratios, the inferior quadrant (0.37±0.28) had a significantly lower ratio than all other quadrants (p < 0 .001). The superoposterior region of the glenoid was found to have denser cancellous bone and a high ratio of cortical to cancellous bone, likely due to decreased formation of cancellous bone and increased formation of cortical bone, in response to localized stresses. The inferior quadrant was found to have the least dense cortical and cancellous bone, and the lowest volume of cortical bone relative to cancellous bone. Once again, this is likely due to reduction in microstrain responsible for bone adaptation via Wolff's law. The density values found in this study generally agree with the range of values found in previous studies of normal and arthritic glenoids. An important limitation of this study is the sizing of measurement regions. For a patient with a smaller glenoid, a depth measurement of two millimeters may represent a larger portion of the overall glenoid vault. Segments could be scaled for each patient based on a percentage of each individual's glenoid size

Humeral head size is defined by the radius of curvature and the thickness of the articular segment. This ratio of radius to thickness is within a narrow range with an average of 0.71. The articular surface of the normal humeral head measured within the AP plane is defined by three landmarks on the non-articular surface of the proximal humerus. The perfect circle concept can be applied for assessment of the anatomic reconstruction of the post-operative x-rays and more importantly can be used intra-operatively as a guide when choosing the proper prosthetic humeral head component. The humeral head is an elliptical shape with its AP dimension being approximately 2 mm less than the SI dimension. This shape contributes to the roll and translation of the normal shoulder but is not replicated by the spherical shape of the prosthetic humeral head. The glenoid vault has a consistent 3D shape and use of the vault model within 3D planning software can define the patient's pre-morbid anatomy, specifically the location of the joint line and patient specific version and inclination. Use of this tool can assist the surgeon in defining the optimal implant and its location. In patients with little or no bone loss, a symmetric glenoid implant is often ideal for resurfacing. When there is asymmetric bone loss, often seen posteriorly with osteoarthritis, an asymmetric posteriorly augmented component can improve the ability to correct the deformity while maintaining the native joint line. It is suggested that these augmented implants in selected patients will help restore and maintain humeral alignment and lessen the risk for residual posterior humeral head subluxation and eccentric loading of the glenoid component

Radiolucent lines in total shoulder arthroplasty around the glenoid component are not uncommon in post-operative x-rays and the incidence varies. A certain percentage progress and as the lines enlarge can lead to component loosening. One study reported a 9% incidence at 2 years and 27% incidence at 5 years. A recent long term study (15 to 20 years) reported a 73% incidence. Radiolucent lines can be caused by anatomy (posterior glenoid wear) or pathology (inflammatory arthritis) as well as technical factors such as glenoid implant design (metal back) and improper implantation techniques where the prosthesis is not fully seated or cement is used to fill a defect. Every attempt should be made to avoid lucent lines. Minimal bone should be removed from the glenoid vault and a pressure injection type of insertion is helpful in getting the cement into the cancellous bone. Furthermore a peg type of glenoid implant rather than a keel type is preferred as this has been associated with a lower incidence of radiolucent lines

Retroversion, also referred to as posterior wear of the glenoid, can make resurfacing the glenoid challenging. However, careful pre-operative planning with three dimensional CT scanning can allow central placement of the glenoid component through removal of some of the anterior bone to allow contained placement and secure fixation within the glenoid vault. Since the scapula is not a fixed skeletal structure and moves substantially on the chest wall, the actual degree of posterior wear (retroversion) frequently is the result of extraneous biomechanical forces and structures. For example, the degree of kyphosis and shape of the rib cage can have a substantial impact on the relative position of the glenoid surface as it articulates with the humerus. Attempts to totally equalise this through implant augmentation have not, to date, been shown to be effective, and in some cases can be destabilising. Restoration of enough alignment to place the implant centrally can be achieved without need for augmentation even in some very hypoplastic glenoids. The technique for this straight-forward approach will be presented, including pre-surgical planning, in some cases, patient specific instrumentation, with demonstration of functional outcomes

Assessing glenoid version is important for a successful total shoulder arthroplasty. Glenoid version is defined as the orientation of the glenoid cavity in relation to a plane perpendicular to the scapula body. Glenoid revision averages between 1 to 2 degrees of retroversion and varies between race and sex. In general glenoid retroversion is overestimated by 6.5 degrees on plain radiographs. Furthermore standard axial 2D CT is aligned to the patient's body and not aligned to the scapula. Therefore 3D reconstructions generated from standard CT allows for analysis of the scapula as a free body and correct version measurements can be made unaffected by positioning. If you add a computer modeling coordinate system in which implants can be added, then computer simulation surgery can be performed. This is important because implanting a glenoid component in excessive retroversion leads to increased stress at the glenoid component and cement mantle and decreased contact with the humeral component. Also excessive reaming of the glenoid surface to neutral retroversion can lead to excessive bone loss and penetration of the glenoid vault by either the pegs or the keel of the glenoid component

Anatomic and accurate placement of components is a primary goal in all arthroplasty procedures. Unique to total shoulder arthroplasty, challenging glenoid exposure and osteoarthritic glenoid deformity offer significant challenges and impediments to this goal. Despite thorough pre-operative planning strategies and contemporary cannulated pin-based shoulder systems, it is often times still difficult to accurately aim the guide pin to the medial border of the scapula when the deformity is substantial or exposure is difficult. Even small errors in guide pin position can result in problems with final component version, inclination and glenoid vault perforation. In addition, a malpositioned glenoid component has been shown to have a negative impact on implant longevity and clinical performance. Image-based patient specific instrumentation has been available in the lower extremity for nearly a decade with reliable results. The application of similar technology in the shoulder has demonstrated reliable positioning of the guide pin to a pre-operative plan with subsequent accurate placement of the glenoid component. This surgical demonstration will feature one of the currently available CT-based patient specific glenoid guides using a standard deltopectoral approach

Introduction. Trabecular bone transmits loads to the cortical shell and is therefore most active in bone remodeling. This remodeling alters trabecular material strength thereby changing the bending stiffness. Accounting for trabecular material heterogeneity has been shown to improve empirical-µFEM correlations by allowing for more realistic trabecular bending stiffness. In µFEMs to reduce computation time, region averaging is often used to scale image resolution. However, region averaging not only alters trabecular architecture, but inherently alters the CT-intensity of each trabeculae. The effect of CT-intensity variations on computationally derived apparent modulus (E. app. ) in heterogenous µFEMs has not been discussed. The objectives of this study were to compare trabecular E. app. among i) hexahedral and tetrahedral µFEMs, ii) µFEMs generated from 32 µm, 64 µm, and 64 µm down-sampled from 32 µm µ-CT scans, and iii) µFEMs with homogeneous and heterogeneous tissue moduli. Methods. Fourteen cadaveric scapulae (7 male; 7 female) were micro-CT scanned at two spatial resolutions (32 µm & 64 µm). Virtual bone cores were extracted from the glenoid vault, maintaining a 2:1 aspect ratio, to create µFEMs from the 32 µm, 64 µm, and down-sampled 64 µm scans. Custom code was used to generate µFEMs with 8-node hexahedral elements (HEX8), while maintaining the bone volume fraction (BV/TV) of each HEX8 32 µm model (BV/TV=0.24±0.10). Each virtual core was also generated as a 10-node tetrahedral (TET10) µFEM. All µFEMs were given either a homogeneous tissue modulus of 20 GPa, or a heterogeneous tissue modulus scaled by CT-intensity. All FEMs were constrained with identical boundary conditions and compressed to 0.5% apparent strain. The apparent modulus of each model was compared. Results. Comparing error in mean E. app. , TET10 32 µm µFEMs with a homogeneous tissue modulus had an error of 7%, and a heterogeneous tissue modulus an error of 1%. Larger errors occurred for both down-sampled and scanned 64 µm µFEMs with both homogeneous and heterogeneous tissue moduli. The error in E. app. as a function of trabecular thickness (Tb.Th*) was larger for µFEMs generated from 64 µm scans, than the down-sampled 64 µm µFEMs. The errors were lowest for Tb.Th* greater than 0.225 mm and for µFEMs generated with heterogeneous tissue moduli. The error in E. app. as a function of volume fraction (BV/TV) was lowest above 0.225 for µFEMs with both homogeneous and heterogeneous tissue moduli and hexahedral and tetrahedral elements. Error was lower for the down-sampled 64 µm µFEMs versus scanned 64 µm µFEMs. DISCUSSION. This study compared the E. app. of linear isotropic µFEMs generated with hexahedral or tetrahedral elements from 32 µm, 64 µm, or down-sampled 64 µm µ-CT scans, with a homogeneous or heterogeneous tissue modulus. It was found that except at the highest spatial resolution, tetrahedral elements underestimate E. app. Down-sampling to half the original scan spatial resolution is not equivalent in E. app. to FEMs generated from scans at that spatial resolution, and both models underestimate the E. app. of the highest spatial resolution models. In general, accounting for trabecular material heterogeneity decreased errors in E. app.

Contracture of the anterior musculature causes posterior humeral head subluxation and results in a posterior load concentration on the glenoid. This reduced contact area causes glenoid wear, humeral medialisation and eventually posterior instability. After arthroplasty that does not correct for this, posterior wear stress increases in the implant, across the cement mantle and bone thus increasing the risk of aseptic loosening over time. Correction of the posterior wear pattern at the time of arthroplasty of the shoulder is recommended. Asymmetric reaming of the glenoid has been recommended as a means to correct this deformity but leads to producing a smaller glenoid which is medialised. This shortening of the glenoid causes the stabilising muscle envelope to shorten and the glenoid vault to become much smaller in volume. These potential changes may have a destabilising effect on the implant leading to early loosening and secondary failure of the prosthetic implant. Other options include using an implant to make the correction of the deformity such as augmented glenoid components. Early uses of these implants were not successful mainly due to the design flaws of the early implants. Newer implants have made design changes to overcome these early failures. CT scan evaluation is important to determine the degree of correction that is needed to balance the glenohumeral joint. Correcting the deformity and keeping the muscle envelope at the appropriate tension may lead to better long term outcomes. These implants are currently in use but long term outcome studies are not yet available to determine their ultimate values to the patients

Most glenoid implants rely on centrally located large fixation features to avoid perforation of the glenoid vault in its peripheral regions [1]. Upon revision of such components there may not be enough bone left for the reinsertion of an anatomical prosthesis, resulting in a large cavity that resembles a sink hole. Multiple press-fit small pegs would allow for less bone resection and strong anchoring in the stiffer and denser peripheral subchondral bone [2], whilst producing a more uniform stress distribution and increased shear resistance per unit volume [3] and avoiding the complications from the use of bone cement. This study assessed the best combination of anchoring strength, assessed as the ratio between push in and pull out forces (Pin/Pout), and spring-back, measured as the elastic displacement immediately after insertion, for five different small press-fitted peg configurations (Figure 1, left) manufactured out of UHMWPE cylinders (5 mm diameter and length). 16 specimens for each configuration were tested in two types of Sawbones solid bone substitute: hard (40 PCF, 0.64 g/cm3, worst-case scenario of Pin) and soft (15 PCF, 0.24 g/cm3, worst-case scenario of spring-back and Pout). Two different interference-fits, Ø, were studied by drilling holes with 4.7 mm and 4.5 mm diameter (Ø 0.3 and Ø 0.5, respectively). A maximum Pin per peg of 50 N was defined, in order to avoid fracture of the glenoid bone during insertion of multiple pegs. The peg specimens were mounted into the single-axis screw-driven Instron through a threaded fixture. A schematic of the experimental set up is made available (Figure 1, centre). The peg was pushed in vertically for a maximum of 5 mm at a 1 mm/s rate, under displacement control, recording Pin. The spring-back effect was assessed by switching to load control and reducing the load to zero. The peg was then pulled out at a rate of 1 mm/s, recording Pout. The test profile is depicted in Figure 1 (right). Average Pout/Pin, spring back (in mm) and force-displacement curves for all 80 specimens tested are shown in Figure 2. These were split into groups according to the type of bone substitute and interference-fit, with the right column showing the average values for the Pin. High repeatability among samples of the same configuration tested is noted. Configurations #1, #3 and #5 all exceed the maximum Pin per peg for at least one type of bone. Configuration #2 has the lowest Pin of all (best thread aspect ratio), followed by configuration #4 (thinner threads). The peg configurations #4 and #2 had the highest Pin/Pout. The peg configurations with lowest spring-back after insertion were configuration #2 and #4. Interference fit of Ø 0.3 mm was shown to reduce Pin below maximum limit of 50 N without great influence in spring-back

Severe glenoid bone loss in patients with osteoarthritis with intact rotator cuff is associated with posterior glenoid bone loss and posterior humeral subluxation. Management of severe glenoid bone loss during shoulder arthroplasty is controversial and technically challenging and options range from humeral hemiarthroplasty, anatomic shoulder replacement with glenoid bone grafting or augmented glenoid component implantation, to reverse replacement with reaming to correct version or structural bone grafting or metallic augmentation of the bone deficiency. Shoulder replacement with severe glenoid bone loss is technically challenging and characterised by higher rates of complications and revisions. Hemiarthroplasty has limited benefit for pain relief and function especially if eccentric glenoid wear exists. Bone loss with >15 degrees of retroversion likely requires version correction include bone-grafting, augmented glenoid components, or reverse total shoulder replacement. Asymmetric reaming may improve version but is limited to 15 degrees of version correction in order to preserve subchondral bone and glenoid bone vault depth. Bone-grafting of glenoid wear and defects has had mixed results with graft-related complications, periprosthetic radiolucent lines, and glenoid component failure of fixation. Implantation of an augmented wedge or step polyethylene glenoid component improves joint version while preserving subchondral bone, but is technically demanding and with minimal short term clinical follow-up. A Mayo study demonstrated roughly 50% of patients with posteriorly augmented polyethylene had radiolucent lines and 1/3 had posterior subluxation. Another wedge polyethylene design had 66% with bone ingrowth around polyethylene fins at 3 years. Long term outcomes are unknown for these new wedge augmented glenoid components. Reverse shoulder arthroplasty avoids many risks of anatomic replacement glenoid component fixation and stability but is associated with a high complication rate (15%) including neurologic and baseplate loosening and often requires structural bone grafting behind the baseplate with suboptimal outcomes or metallic augmented baseplates with limited evidence and short term outcomes. Reverse replacement with baseplate bone grafting or metal augmentation is technically challenging due to limited native glenoid bone stock available for baseplate component ingrowth and long term fixation. Failure to correct glenoid superior inclination and restore neutral version within 10 degrees increases the risks of reverse baseplate failure of fixation, pull out, and failure of reverse replacement. Reverse baseplate failure rates in patients with severe glenoid bone loss and concomitant glenoid bone grafting range from 5–11%. The minimum native glenoid bony contact with the baseplate is unknown but likely is approximately 1cm of native bone contacting a central ingrowth post and a minority (∼15–25%) of native glenoid contacting the backside of the baseplate. Failure to correct posterior bone loss can lead to retroversion of the baseplate, reduced external rotation, posterior scapular notching, and posteromedial polyethylene wear. In summary, shoulder replacement with severe glenoid bone loss is technically challenging and characterised by higher rates of complication and revision