The degree of glenoid bone loss associated with primary glenohumeral osteoarthritis can influence the type of glenoid implant selected and its placement in total shoulder arthroplasty (TSA). The literature has demonstrated inaccurate glenoid component placement when using standard instruments and two-dimensional (2D) imaging without templating, particularly as the degree of glenoid deformity or bone loss worsens. Published results have demonstrated improved accuracy of implant placement when using three-dimensional (3D) computed tomography (CT) imaging with implant templating and patient specific instrumentation (PSI). Accurate placement of the glenoid component in TSA is expected to decrease component malposition and better correct pathologic deformity in order to decrease the risk of component loosening and failure over time. Different types of PSI have been described. Some PSI use 3D printed single use disposable instrumentation, while others use adjustable and reusable-patient specific instrumentation (R-PSI). However, no studies have directly compared the accuracy of different types of PSI in shoulder arthroplasty. We combined our clinical experience and compare the accuracy of glenoid implant placement with five different types of instrumentation when using 3D CT imaging, preoperative planning and implant templating in a series of 173 patients undergoing primary TSA. Our hypothesis was that all PSI technologies would demonstrate equivalent accuracy of implant placement and that PSI would show the most benefit with more severe glenoid deformity. We demonstrated no consistent differences in accuracy of 3D CT preoperative planning and templating with any type of PSI used. In Groups 1 and 2, standard instrumentation was used in a patient specific manner defined by the software and in Groups 3, 4, and 5 a patient specific instrument was used. In all groups, the two surgeons were very experienced with use of the 3D CT preoperative planning and templating software and all of the instrumentation prior to starting this study, as well as very experienced with shoulder arthroplasty. This is a strength of the study when defining the efficacy of the technology, but limits the generalizability of the findings when considering the effectiveness of the technology with surgeons that may not have as much experience with shoulder arthroplasty and/or the PSI technology. Conversely, it could be postulated that greater improvements in accuracy may be seen with the studied PSI technology, when compared to no 3D planning or PSI, with less experienced surgeons. There could also be differences between the PSI technologies when used by less experienced surgeons, either across all cases or based upon the severity of pathology. When the surgeon is part of the method, the effectiveness of the technology is equally dependent upon the surgeon using the technology. A broader study using different surgeons is required to test the effectiveness of this technology. Comparing the results of this study with published results in the literature, 3D CT imaging and implant templating with use of PSI results in more accurate placement of the glenoid implant when compared to 2D CT imaging without templating and use of standard instrumentation. In previous studies, this was most evident in patients with more severe bone deformity. We believe that 3D CT planning and templating provides the most value in defining the glenoid pathology, as well as in the selection of the optimal implant and its placement. However, it should be the judgment of the surgeon, based upon their experience, to select the instrumentation to best achieve the desired result.Introduction
Discussion and Conclusions
The number of shoulder arthroplasty procedures performed in the United States continues to rise. Currently, the number of procedures performed per year ranges from 55,000–80,000 and is expected to increase more than 300% in the coming years. Periprosthetic joint infection (PJI) is one of the most serious complications associated with arthroplasty surgery, leading to poor outcomes, increased cost, and technically difficult revision surgery. The incidence of infection following primary shoulder arthroplasty has been reported between 0.7% and 4%, representing 2.9–4.6% of all complications. Prosthetic shoulder joint infections are unlike prosthetic joint infections of the hip and knee. Shoulder PJIs are primarily indolent in nature and difficult to diagnose using traditional methods that have been shown to be accurate for periprosthetic infections of the hip and knee. The majority of infected revision shoulder arthroplasties are associated with growth of Propionibacterium acnes (P. Acnes). This slow-growing, anaerobic organism requires longer than normal incubation times for culture (7–21 days), and typically demonstrates a subtle, non-specific clinical presentation that can make the presence of infection difficult to identify. In the reported literature, P. Acnes accounts for about 70% of cases with positive cultures associated with revision for treatment of a painful shoulder arthroplasty and due to the bacteria's slow growing nature and virulence profile, the rate of infection following shoulder arthroplasty may often be underestimated. A more recent and promising tool for evaluation of periprosthetic infection has been analysis of synovial fluid. Synovial fluid biomarkers have been identified as part of the innate response to pathogens, and include pro-inflammatory cytokines and anti-microbial peptides, and marker levels have shown promise for improved diagnostic efficacy in hip and knee PJI. Currently, no highly predictive clinical test for diagnosis of PJI in the shoulder exists, however, several of these synovial biomarkers have recently been analyzed for their diagnostic capacity in the setting of periprosthetic shoulder infection. Synovial fluid cytokine analysis shows the potential to improve diagnosis of infection in revision shoulder arthroplasty. This information can help to guide decision-making in the management of PJI of the shoulder, including the decision to perform a single- vs. two-stage revision surgery, and the need for post-operative antibiotics following an unexpected positive culture result after revision surgery. However, there are still challenges to broader use of these synovial biomarkers. Synovial α-defensin (Synovsure, CD Diagnostic) is the only marker currently available as a commercial test, and no point-of-care test is currently available for any of the biomarkers to allow for intraoperative decision-making. While a preoperative synovial aspirate is possible to send for α-defensin analysis currently, with results back in approximately 24 hours, dry fluid aspirations are frequent in the shoulder because of the predominance of indolent pathogens and may limit utility of the test. In summary, indolent infection associated with P. acnes is a common cause for the painful total shoulder arthroplasty. Pre-operative diagnosis of infection is difficult as a result of the poor diagnostic accuracy of traditional methods of testing. Synovial biomarker testing may ultimately improve our ability to more accurately diagnosis and treat prosthetic shoulder joint infections.
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.
CT-based three-dimensional (3D) pre-operative imaging along with 2D orthogonal sections defined by the plane of the scapula (axial, sagittal and coronal planes) has been demonstrated by many research groups to be a very accurate way to define the bone pathology and alignment/subluxation of the humeral head in relationship to the center line of the scapula or the center of the glenoid fossa. When 3D CT imaging is combined with 3D implant templating the surgeon is best able to define the optimal implant and its location for the desired correction of the bone abnormalities. The use and value of 3D imaging is best when the there is more severe bone pathology and deformity. Transferring the computer-based information of implant location to the surgical site can involve multiple methods. The three methods discussed in the literature to date including use of standard instrumentation in a manner specified by the pre-operative planning, use of single-use patient specific instrumentation and use of reusable patient specific instrumentation. Several cadaver and sawbone studies have demonstrated significant improvement in placement of the glenoid implant with both single use and reusable patient specific instrumentation when compared to use of 2D imaging and standard instrumentation. Randomised clinical trials have also shown that 3D planning and implant templating is very effective in accurate placement of the implant in the desired location using all three types of instrumentation. The optimal use of this technology is dependent upon the severity of the pathology and the experience and preference of the surgeon. With more severe pathology and less surgeon experience 3D pre-operative imaging and templating and use of some level of patient specific instrumentation provides more accurate placement of the glenoid implant.
Peri-prosthetic joint infection (PJI) can be both a diagnostic and therapeutic challenge in shoulder arthroplasty, due to the indolent nature of the common infecting organisms. Proprionobacterium acnes (P. acnes) is the most common pathogen cultured in revision shoulder arthroplasty. It is a slow growing, anaerobic organism – requires longer incubation period (7–21 days). Coagulase-negative Staphylococcus species (CNSS) is also a common organism responsible for PJI. Established diagnostic tests for hip and knee PJI are often negative in the shoulder despite post-operative growth of intra-operative cultures. Pre-operative synovial aspiration often low volume due to indolent pathogens and successful aspiration is often reported to be 50% or less with Dilisio et al, JBJS 2014: reporting 16.7% sensitivity, 100% specificity. Variable culture length for P. acnes culture protocols are reported from 7–28 days with most groups recommending 14 days. From our research, we demonstrated time to culture growth was significantly shorter in probable true positive culture group (median, 5 vs. 9 days, p=0.002). Frozen section analysis may help intra-operative decision-making (one- vs. two-stage reimplantation) yet the reported sensitivity and specificity in shoulder arthroplasty is far less than in hip and knee arthroplasty. Synovial fluid biomarkers have been identified as part of the innate response to pathogens include pro-inflammatory cytokines and antimicrobial peptides. In a series of prospective studies of revision shoulder arthroplasty, synovial fluid analysis reported by Frangiamore et al, JBJS 2015: IL-6, Frangiamore et al, JSES 2015: α-defensin (SynovasureTM), Frangiamore et al, AAOS 2015: Broader cytokine analysis it was demonstrated that these markers are much more predictive of infection than synovial fluid cultures, frozen section or serum markers.
Patient medical comorbidities are well-established risk modifiers of THA patient outcomes. Patient's mental state preoperatively may influence postoperative functional outcomes though just like any medical comorbidity. This study sought to determine if patient confidence in attaining post-operative functional goals was associated with objective and subjective outcomes following THA. Patients undergoing primary or revision THA at a single institution between 2008 and 2010 were administered a questionnaire consisting of demographics, body mass index, Hip Dysfunction Osteoarthritis and Outcomes Score (HOOS), SF-12 scores, the level of functionality they hoped to gain postoperatively and their confidence in attaining that goal (0–10 scale) preoperatively and postoperatively at last follow-up (minimum 12 months). Measured outcomes included length of stay, 30-day readmission, HOOS, and SF-12 physical component scores. Correlation of patient confidence in attaining treatment goals and the outcomes collected was established using multiple linear and logistic regression models that were adjusted for all variables, including baseline mental and functional scores.Introduction:
Methods:
Glenoid component loosening remains as an unsolved clinical problem in total shoulder arthroplasty. Current clinical assessment relies on subjective quantification using a two-dimensional plane X-ray image with arbitrarily defined criteria. There is a need to develop a readily usable clinical tool to accurately and reliably quantify the glenoid component motion over time after surgery. A high-resolution clinical CT has the potential to quantify the glenoid motion, but is challenged by metal artifact from the prosthetic humeral components. The objective of this study is to demonstrate the feasibility of using a clinical CT reconstruction to quantify the glenoid implant motion with the aid of tantalum markers. Three spherical tantalum markers of 1.0 mm in diameter were inserted into three peripheral pegs of an all polyethylene glenoid component. The glenoid component was implanted in a sawbone scapula. To determine the effect of metal artifact on quantification of glenoid implant motion, two sawbone humerii were used: one without the prosthetic humeral components and the other with the prosthetic humeral head and stem. Three custom-made translucent spacers with the uniform thickness were placed between the glenoid component and the scapula to produce a gradual translation of the glenoid component from 1 mm to 3 mm. Before and after inserting each spacer, the surface of the glenoid component was digitized by a MicroScribe. The surface points were used to fit a sphere and the corresponding center of the sphere was calculated. The actual translation of the glenoid component was measured as the three-dimensional (3D) distance between the center of the sphere before and after insertion of each spacer. Then, the shoulder model was scanned by a clinical CT with and without the spacers for both humerii conditions. Velcro straps were used to secure the humerus to the glenoid component between the trials. All CT scans were reconstructed in VolNinja software to superimpose the scapula positions (Figure 1). The three tantalum markers were visualized and the center coordinates of the markers were used to measure the 3D distance before and after insertion of each spacer. The accuracy was defined by the difference between the averaged 3D distance measured by CT reconstruction and that measured by the MicroScribe. The standard deviation of the 3D distance measured by each tantalum marker was calculated to evaluate the reliability of the tantalum marker visualization.Background:
Methods:
Total knee arthroplasty (TKA) outcomes drive assessment of quality and reinvestment; therefore a risk stratified assessment is paramount for fair evaluation. Stratification can be affected by multiple factors including patient motivation. This study attempted to identify the correlation of patient's preoperative confidence in their ability to return to desired activity level after TKA and improved function and outcomes. A continuous series of TKA procedures from 2008 to 2010 in a healthcare system was reviewed retrospectively. Patients included reported pre- and postoperative knee injury and osteoarthritis outcomes scores (KOOS), SF-12 scores, and responded a question regarding the desired activity level, including the level of confidence (0–10 scale) in attaining such goals, after surgery. Gender, age, body mass index, education level, smoking status, length of stay (LOS), 30-day readmission and reoperation, and 1-year infection rates were collected. Correlation of patient confidence in attaining treatment goals and the outcomes collected was established using multiple linear and logistic regression models adjusted for baseline mental and functional scores.Introduction:
Methods:
Accurate implant placement is important to the success of joint replacement surgery. Three dimensional pre-operative planning optimizing the ability to define the anatomy and select the desired implant and its location. Linking this information into implant and patient specific instrumentation has been termed smart instrumentation. Single use instruments contain the patient's topographical boney anatomy and implant information. This same information can be placed within a bone model and a reusable instrument placed onto the bone model can be adjusted to capture the information originally in the planning software. This instrument can then be placed into the surgical site, registered to the bone surfaces and used to modify the bone surfaces to replicate the surgical plan. These concepts, technology and devices have been developed and clinically tested in randomized clinical trials for shoulder arthroplasty.
Advanced 3D CT imaging of the shoulder using metal artifact reduction techniques have been developed and validated in pre-clinical and patient population using microscribe and RSA techniques. These studies demonstrate these methods to be highly accurate and reproducible in the measurement of implant position and implant migrations. 3D CT imaging is being used to study the anatomic and clinical factors associated with glenoid implant loosening. This imaging modality does not require marker based image registration and utilizes imaging equipment that is readily available in the clinical setting.
Acetabular component malpositioning in total hip arthroplasty increases the risk of dislocations, impingement, and long-term component wear. The purpose of this Sawbones study was to define the efficacy of a novel acetabular imprinting device (AID) with 3D preoperative planning in accurately placing the acetabular component. Four surgeons performed the study on osteoarthritic and dysplastic Sawbone models using 3 different methods for placing the acetabular component (total n = 24). The 3 methods included (1) standard preoperative planning and instrumentation (i.e., standard method), (2) 3D computed tomographic (CT) scan planning and standard instrumentation (i.e., 3D planning method), and (3) 3D CT scan planning combined with an acetabular imprinting device (i.e., AID method). In the AID method, 3D planning software was used to virtually place the acetabular component at 40° of inclination and 22° of anteversion and create a parallel guide pin trajectory. A patient-specific surrogate bone model with a built-in guide pin trajectory was then manufactured as a stereoltihography device (Fig. 1A). The surgeon molded bone cement into the acetabulum imprinting the acetabular features while maintaining the guide pin trajectory (Fig. 1B). Afterward, the AID was removed from the surrogate bone model and placed onto the Sawbone, ensuring a secure fit (Fig. 1C). A guide pin was drilled into the Sawbone along the prescribed trajectory. With the guide pin in place, the surgeon could ream the acetabulum and impact the acetabular component using the guide pin as a visual aid (Fig. 1D). Postoperatively, a CT scan was used to define and compare the actual implant location with the preoperative plan. Statistical analysis was performed as 3 group comparisons using the chi-squared test for categorical data and analysis of variance (ANOVA) for continuous measurements.Background:
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