The development of a novel navigation system for reverse shoulder arthroplasty and its accuracy: a phantom and cadaveric study

PURPOSE

Reverse shoulder arthroplasty has demonstrated excellent clinical efficacy for patients with shoulder joint diseases and is increasingly in demand. Traditional surgery faces challenges such as limited exposed surfaces and a narrow field of vision, leading to a shorter prosthesis lifespan and a higher risk of complications. In this study, an optical navigation system was proposed to assist surgeons in real-time tracking of the surgical scene.

METHODS

Our optical navigation system was developed using the NDI Polaris Spectra device and several open-source platforms. The first step involved using the preoperative medical image to plan screw implantation paths. Real-time tracking of the patient phantom or cadaver and the surgical instrument was achieved through registration and calibration algorithms. Surgeons were guided on drilling through visualization methods. Postoperative results were compared with the planned implantation paths, and an algorithm was introduced to correct errors caused by the incorrect beginning points.

RESULTS

Experiments involved three scapula cadavers and their corresponding phantoms with identical anatomy. For each experiment, three holes were completed with drills with diameters of 3.2 mm and 8.0 mm, respectively. Comparisons between the postoperative actual screw implantation paths and the preoperative planned implantation paths revealed an entry error of 1.05 ± 0.15 mm and an angle error of 2.47 ± 0.55° for phantom experiments. For cadaver experiments, the entry error was 1.53 ± 0.22 mm, and the angle error was 4.91 ± 0.78°.

CONCLUSION

Our proposed optical navigation system successfully achieved real-time tracking of the surgical site, encompassing the patient phantom or cadaver and surgical instrument, thereby aiding surgeons in achieving precise surgical outcomes. Future study will explore the integration of robots to further enhance surgical efficiency and effectiveness.

Preoperative 3-dimensional computed tomography bone density measures provide objective bone quality classifications for stemless anatomic total shoulder arthroplasty

BACKGROUND

Reproducible methods for determining adequate bone densities for stemless anatomic total shoulder arthroplasty (aTSA) are currently lacking. The purpose of this study was to evaluate the utility of preoperative computed tomography (CT) imaging for assessing the bone density of the proximal humerus for supportive differentiation in the decision making for stemless humeral component implantation. It was hypothesized that preoperative 3-dimensional (3-D) CT bone density measures provide objective classifications of the bone quality for stemless aTSA.

METHODS

A 3-part study was performed that included the analysis of cadaveric humerus CT scans followed by retrospective application to a clinical cohort and classification with a machine learning model. Thirty cadaveric humeri were evaluated with clinical CT and micro-CT (μCT) imaging. Phantom-calibrated CT data were used to extract 3-D regions of interest and defined radiographic scores. The final image processing script was applied retrospectively to a clinical cohort (n = 150) that had a preoperative CT and intraoperative bone density assessment using the "thumb test," followed by placement of an anatomic stemmed or stemless humeral component. Postscan patient-specific calibration was used to improve the functionality and accuracy of the density analysis. A machine learning model (Support vector machine [SVM]) was utilized to improve the classification of bone densities for a stemless humeral component.

RESULTS

The image processing of clinical CT images demonstrated good to excellent accuracy for cylindrical cancellous bone densities (metaphysis [ICC = 0.986] and epiphysis [ICC = 0.883]). Patient-specific internal calibration significantly reduced biases and unwanted variance compared with standard HU CT scans (P < .0001). The SVM showed optimized prediction accuracy compared with conventional statistics with an accuracy of 73.9% and an AUC of 0.83 based on the intraoperative decision of the surgeon. The SVM model based on density clusters increased the accuracy of the bone quality classification to 87.3% with an AUC of 0.93.

CONCLUSIONS

Preoperative CT imaging allows accurate evaluation of the bone densities in the proximal humerus. Three-dimensional regions of interest, rescaling using patient-specific calibration, and a machine learning model resulted in good to excellent prediction for objective bone quality classification. This approach may provide an objective tool extending preoperative selection criteria for stemless humeral component implantation.

Image-derived instrumentation vs. conventional instrumentation with 3D planning for glenoid component placement in reverse total shoulder replacements: a randomized controlled trial

Hypothesis

Glenoid baseplate positioning for reverse total shoulder arthroplasty (rTSA) is important for stability and longevity, with techniques such as image-derived instrumentation (IDI) developed for improving implant placement accuracy. We performed a single-blinded randomized controlled trial comparing glenoid baseplate insertion accuracy with 3D preoperative planning and IDI jigs vs. 3D preoperative planning and conventional instrumentation.

Methods

All patients had a preoperative 3D computed tomography to create an IDI; then underwent rTSA according to their randomized method. Repeat computed tomography scans performed at six weeks postoperatively were compared to the preoperative plan to assess for accuracy of implantation. Patient-reported outcome measures and plain radiographs were collected with 2-year follow-up.

Results

Forty-seven rTSA patients were included (IDI n = 24, conventional instrumentation n = 23). The IDI group was more likely to have a guidewire placement within 2mm of the preoperative plan in the superior/inferior plane (P = .01); and exhibited a smaller degree of error when the native glenoid retroversion was >10° (P = .047). There was no difference in patient-reported outcome measures or other radiographic parameters between the two groups.

Conclusion

IDI is an accurate method for glenoid guidewire and component placement in rTSA, particularly in the superior/inferior plane and in glenoids with native retroversion >10°, when compared to conventional instrumentation.

Feasibility study for the automatic surgical planning method based on statistical model

PURPOSE

In this study, we proposed establishing an automatic computer-assisted surgical planning approach based on average population models.

METHODS

We built the average population models from humerus datasets using the Advanced Normalization Toolkits (ANTs) and Shapeworks. Experiments include (1) evaluation of the average population models before surgical planning and (2) validation of the average population models in the context of predicting clinical landmarks on the humerus from the new dataset that was not involved in the process of building the average population model. The evaluation experiment consists of explained variation and distance model. The validation experiment calculated the root-mean-square error (RMSE) between the expert-determined clinical ground truths and the landmarks transferred from the average population model to the new dataset. The evaluation results and validation results when using the templates built from ANTs were compared to when using the mean shape generated from Shapeworks.

RESULTS

The average population models predicted clinical locations on the new dataset with acceptable errors when compared to the ground truth determined by an expert. However, the templates built from ANTs present better accuracy in landmark prediction when compared to the mean shape built from the Shapeworks.

CONCLUSION

The average population model could be utilized to assist anatomical landmarks checking automatically and following surgical decisions for new patients who are not involved in the dataset used to generate the average population model.

Description and Validation of the Anterior Glenoid Angle: A Novel MRI-Based Measure of Glenoid Morphologic Features and Version

The goal of this study was to establish a normal value for, and evaluate the reliability of, a new measurement of glenoid morphologic features using magnetic resonance imaging: the anterior glenoid angle. A total of 90 magnetic resonance imaging scans of patients without shoulder arthritis were reviewed. The anterior glenoid angle of each glenoid was measured by 4 blinded physicians. The images were randomized and measured again. Finally, the Friedman angle was measured on the same images for reference. Descriptive statistics and inter- and intraclass correlation coefficients were calculated. The mean anterior glenoid angle was 60.4°±3.6°. Of the measured values, 77% were between 56° and 64°. Intraobserver reliability was very good to excellent in single measure (range, 0.763-0.901) and mean measure (range, 0.865-0.948) comparisons. Interobserver reliability was very good to excellent in both single measure (0.769) and mean measure (0.964) comparisons. The mean Friedman angle was 10.2°. Correlation between the anterior glenoid angle and Friedman angle ranged from a moderate negative (-0.496) to a strong negative correlation (-0.711) among the observers. The mean anterior glenoid angle measured via magnetic resonance imaging scan was 60.4° in normal shoulders, and more than 75% of the values were within 4° of the mean. The anterior glenoid angle has excellent inter- and intrarater reliability without using computed tomography scan or including the entire scapula in the field of view. The anterior glenoid angle has a good to very good negative correlation with the Friedman angle because decreasing anterior glenoid angles indicate increasing retroversion. [Orthopedics. 2022;45(6):361-366.].

Reverse Total Shoulder Arthroplasty for Treatment of Massive, Irreparable Rotator Cuff Tear

Massive tears of the rotator cuff can result in severe functional deficits due to loss of the axial force couple and effective fulcrum that the intact cuff normally provides. For massive, irreparable rotator cuff tears, especially in the setting of early to moderate degenerative changes, reverse total shoulder arthroplasty functions to modify the center of joint rotation, allowing the deltoid and intact components of the cuff to carry out shoulder function more effectively. Our preferred technique uses a standard open deltopectoral shoulder approach with a 3-dimensional glenoid baseplate model and a 135° prosthesis in an onlay configuration to reduce the risk of scapular notching and increase lateralization of the humerus.

Is Advanced Imaging to Assess Rotator Cuff Integrity Before Shoulder Arthroplasty Cost-effective? A Decision Modeling Study

BACKGROUND

Shoulder arthroplasty is increasingly performed for patients with symptoms of glenohumeral arthritis. Advanced imaging may be used to assess the integrity of the rotator cuff preoperatively because a deficient rotator cuff may be an indication for reverse shoulder arthroplasty (RSA) rather than anatomic total shoulder arthroplasty (TSA). However, the cost-effectiveness of advanced imaging in this setting has not been analyzed.

QUESTIONS/PURPOSES

In this cost-effectiveness modeling study of TSA, all patients underwent history and physical examination, radiography, and CT, and we compared (1) no further advanced imaging, (2) selective MRI, (3) MRI for all, (4) selective ultrasound, and (5) ultrasound for all.

METHODS

A simple chain decision model was constructed with a base-case 65-year-old patient with a 7% probability of a large-to-massive rotator cuff tear and a follow-up of 5 years. Strategies were compared using the incremental cost-effectiveness ratio (ICER) with a willingness to pay of both USD 50,000 and 100,000 per quality-adjusted life year (QALY) used, in accordance with the Second Panel on Cost-Effectiveness in Health and Medicine. Diagnostic test sensitivity and specificity were extracted from published systematic reviews and meta-analyses, and patient utilities were obtained using the Cost-Effectiveness Analysis Registry from the Center for the Evaluation of Value and Risk in Health. Final patient states were categorized as either inappropriate or appropriate based on the actual rotator cuff integrity and type of arthroplasty performed. Additionally, to evaluate the real-world impact of intraoperative determination of rotator cuff status, a secondary analysis was performed where all patients indicated for TSA underwent intraoperative rotator cuff examination to determine appropriate implant selection.

RESULTS

Selective MRI (ICER of USD 40,964) and MRI for all (ICER of USD 79,182/QALY) were the most cost-effective advanced imaging strategies at a willingness to pay (WTP) of USD 50,000/QALY gained and 100,000/QALY gained, respectively. Overall, quality-adjusted life years gained by advanced soft tissue imaging were minimal: 0.04 quality-adjusted life years gained for MRI for all. Secondary analysis accounting for the ability of the surgeon to alter the treatment plan based on intraoperative rotator cuff evaluation resulted in the no further advanced imaging strategy as the dominant strategy as it was the least costly (USD 23,038 ± 2259) and achieved the greatest health utility (0.99 ± 0.05). The sensitivity analysis found the original model was the most sensitive to the probability of a rotator cuff tear in the population, with the value of advanced imaging increasing as the prevalence increased (rotator cuff tear prevalence greater than 12% makes MRI for all cost-effective at a WTP of USD 50,000/QALY).

CONCLUSION

In the case of diagnostic ambiguity based on physical exam, radiographs, and CT alone, having both TSA and RSA available in the operating room appears more cost-effective than obtaining advanced soft tissue imaging preoperatively. However, performing selective MRI to assess rotator cuff integrity to indicate RSA or TSA is cost-effective if surgical preparedness, patient expectations, and implant availability preclude the ability to switch implants intraoperatively.

LEVEL OF EVIDENCE

Level III, economic and decision analysis.

Automatic surgical planning based on bone density assessment and path integral in cone space for reverse shoulder arthroplasty

PURPOSE

Reverse shoulder arthroplasty (RSA) is an effective surgery for severe shoulder joint diseases. Traditionally, the preoperative planning procedure of RSA is manually conducted by experienced surgeons, resulting in prolonged operating time and unreliable drilling paths of the prosthetic fixation screws. In this study, an automatic surgical planning algorithm for RSA was proposed to compute the optimal path of screw implantation.

METHODS

Firstly, a cone-shaped space containing alternative paths for each screw is generated using geometric parameters. Then, the volume constraint is applied to automatically remove inappropriate paths outside the bone boundary. Subsequently, the integral of grayscale value of the CT is used to evaluate the bone density and to compute the optimal solution. An automatic surgical planning software for RSA was also developed with the aforementioned algorithms.

RESULTS

Twenty-four clinical cases were used for preoperative planning to evaluate the accuracy and efficiency of the system. Results demonstrated that the angles among the prosthetic fixation screws were all within constraint angle(45°), and the stability rate of the planned prosthesis was 94.92%. The average time for the automatic planning algorithm was 4.39 s, and 83.96 s for the whole procedure. Repetitive experiments were also conducted to demonstrate the robustness of our system, and the variance of the stability coefficient was 0.027%.

CONCLUSIONS

In contrast to the cumbersome manual planning of the existing methods for RSA, our method requires only simple interaction operations. It enables efficient and precise automatic preoperative planning to simulate the ideal placement of the long prosthetic screws for the long-term stability of the prosthesis. In the future, it will have great clinical application prospects in RSA.

CT versus MRI planning for reverse geometry total shoulder arthroplasty

Introduction

Preoperative planning for Reverse Total Shoulder Arthroplasty (RTSA) using CT or MRI is well described.1, 2, 3, 4, 5, 6, 7 We aimed to compare pre-operative CT versus MRI measurement accuracy for predicting intra-operative glenoid implant sizing.

Methods

All patients with a preoperative CT or MRI undergoing RTSA at our tertiary referral center from October 2017 to February 2020 were included. Data was collected from theatre and implant registers. Glenosphere Width (GW) and Baseplate Central Screw Length (BCSL) were independently predicted from pre-operative CT or MRI imaging by 2 blinded senior authors. A sub-group analysis was also performed between trauma and non-trauma CT cases. SPSS v26 was used for statistical comparison between predicted and actual implants.

Results

71 data sets from 69 patients were included for analysis: 31 CT predictions and 40 MRI predictions. 61.3% of CT measured GW predictions were accurate compared to 82.5% of MRI predictions (p = 0.045). BCSL predictions were 77.4% and 70% accurate for CT and MRI respectively, without significant difference. There was no significant difference in sub-group analysis for trauma vs elective CT accuracy of BCSL or GW measurements.

Conclusion

MRI imaging may be superior to CT for predicting GW and no less accurate than CT for predicting BCSL in the elective setting. No difference in CT measurement accuracy was seen between trauma and elective settings. While simultaneously clearly defining shoulder soft tissue anatomy, MRI may also be the preferred modality for bony measurements during pre-operative planning for elective RTSA.

How to Measure Glenoid Bone Stock and Version and Why It Is Important: A Practical Guide

Shoulder osteoarthritis (OA) is a common and debilitating condition and a source of high morbidity and medical expenditures across the world among individuals older than 60 years. Shoulder OA results in the gradual destruction of articular cartilage of the humeral head and glenoid component, causing inflammation, pain, and a restricted range of motion. Most patients are diagnosed with shoulder OA after experiencing shoulder pain and stiffness, and the diagnosis is often made after medical and physical histories are obtained and physical and imaging examinations are performed. Use of various surgical techniques such as total anatomic or reverse shoulder arthroplasty and hemiarthroplasty has increased in recent years, resulting in reduced morbidity and improved functional status of patients. However, the rate of surgical complications such as premature loosening of components is significant, reducing the effectiveness of such procedures. Data in the literature indicate that high-grade fatty infiltration of the rotator cuff muscle before surgery is associated with postoperative glenoid component loosening. High-grade rotator cuff fatty infiltration and atrophy have been found to be associated with more severe Walch classification-based glenoid morphology subtypes, increased joint line medialization, glenoid bone loss, and increased pathologic glenoid version. The authors describe how advanced imaging techniques are used for preoperative evaluation of the shoulder and discuss how to measure glenoid version and bone stock and classify glenoid morphology types on the basis of Walch classification, as these parameters are commonly used in surgical planning. Methods involving the use of Friedman and paleoglenoid lines for respective measurements are illustrated by using three-dimensional CT and MRI case examples. ^©RSNA, 2020.

Surgeon acceptance of an initial 3D glenoid preoperative plan: rates and risk factors

BACKGROUND

Although the effect of 3-dimensional (3D) planning for total shoulder arthroplasty (TSA) on component positioning and patient outcomes has been increasingly studied, the effect of 3D planning on surgeon decision making has not been well studied.

METHODS

A retrospective review was performed of a database containing TSA cases for which the glenoid component was planned with a commercially available 3D computed tomography software program (Virtual Implant Positioning; Arthrex, Inc.) from 2016 to 2019. A total of 6483 cases planned by 417 surgeons were included. The glenoid version (V_tech) and inclination (I_tech) of the Virtual Implant Positioning technician plan as well as the surgeon's final plan for version (V_surg) and inclination (I_surg) were extracted. When the version and/or inclination of the surgeon plan matched that of the technician, that variable was defined as "accepted." The rates of acceptance of V_tech and I_tech were calculated and analyzed for association with implant type, native version and inclination, and running case count. A subgroup analysis of high-volume users (n > 30 cases) was analyzed to determine if any of the variables independently was associated with surgeon acceptance.

RESULTS

There was a very high rate of matching of version (66%), inclination (72%), or both (55%) and a low rate (18%) where neither parameter of the glenoid plan matched that of the technician. In univariate analysis, as the case count and retroversion increased the rate of accepting of version dropped noticeably (70%-50% and 47%, respectively [ P< .0001]). The rate of accepting the plan for inclination did not vary much as case count changed. In the multivariate analysis, 23 of 56 high-volume surgeons had at least 1 independent factor associated with accepting the technician-planned glenoid version, and 5 surgeons had 2 independent factors. In the multivariate analysis of matching glenoid inclination, 27 of 56 high-volume surgeons had at least 1 independent factor associated with accepting the technician-planned glenoid version, and 9 surgeons had 2 or more independent factors.

CONCLUSIONS

In a large database of TSAs with 3D-planned glenoids, there were high rates of cases with surgeon agreement with an initial plan provided by an industry technician: 66% in version, 72% in inclination, 55% for both version and inclination. Surgeon acceptance of the initial plan decreased as pathoanatomy increased and case count increased. Shoulder surgeons should be aware that an initial 3D preoperative plan provided by industry represents a potential source of cognitive bias in shoulder arthroplasty planning.

Finite Element Analysis of Custom Shoulder Implants Provides Accurate Prediction of Initial Stability

Custom reverse shoulder implants represent a valuable solution for patients with large bone defects. Since each implant has unique patient-specific features, finite element (FE) analysis has the potential to guide the design process by virtually comparing the stability of multiple configurations without the need of a mechanical test. The aim of this study was to develop an automated virtual bench test to evaluate the initial stability of custom shoulder implants during the design phase, by simulating a fixation experiment as defined by ASTM F2028-14. Three-dimensional (3D) FE models were generated to simulate the stability test and the predictions were compared to experimental measurements. Good agreement was found between the baseplate displacement measured experimentally and determined from the FE analysis (Spearman’s rank test, p < 0.05, correlation coefficient ρs = 0.81). Interface micromotion analysis predicted good initial fixation (micromotion <150 µm, commonly used as bone ingrowth threshold). In conclusion, the finite element model presented in this study was able to replicate the mechanical condition of a standard test for a custom shoulder implants.

The evolution of virtual reality in shoulder and elbow surgery

Virtual Reality (VR) in orthopedic surgery has significantly increased in popularity in the areas of preoperative planning, intraoperative usage, and for education and training; however, its utilization lags behind other surgical disciplines and industries. The use of VR in orthopedics is largely focused on education and is currently endorsed by North American and European training committees. The use of VR in shoulder and elbow surgery has varying levels of evidence, from I to IV, and typically involves educational randomized controlled trials. To date, however, the terms and definitions surrounding VR technology used in the literature are often redundant, confusing, or outdated. The purpose of this review, therefore, was to characterize previous uses of VR in shoulder and elbow surgery in preoperative, intraoperative, and educational domains including trauma and elective surgery. Secondary objectives were to provide recommendations for updated terminology of immersive VR (iVR) as well as provide a framework for standardized reporting of research surrounding iVR in shoulder and elbow surgery.