Intraoperative modification of total elbow arthroplasty implants.

BACKGROUND: Modification of total elbow arthroplasty (TEA) implants may be necessary in selected patients with substantial anatomic bone deformity or those undergoing revision surgery. The purpose of this study was to investigate the prevalence and consequences of implant modifications during TEA at our institution. We hypothesized that TEA implant modification would be more common in revisions than in primary replacements, and that it would not be associated with worse clinical outcomes or increased rates of radiographic or surgical complications directly related to the implant modification. METHODS: Elbows that had undergone TEA by any of 3 surgeons at our institution with use of intraoperative implant modification between January 1992 and October 2019 were retrospectively reviewed for the type of modification and complications. Complications were classified as definitely related, probably related, possibly related, or nonrelated to the implant's modification according to the consensus review by the 3 senior surgeons. A survey was sent out to surgeons outside of our institution to investigate whether intraoperative modification to TEA implants is a common clinical practice. RESULTS: A total of 106 implant components were modified during 94 of 731 TEA procedures (13%) in 84 of 560 patients. Implant modifications were performed in 60 of 285 revision cases (21%) compared with 34 of 446 (8%) primary cases (P < .0001). These included shortening the stem in 40 (44%), bending the stem in 16 (15%), notching the stem in 16 (15%), tapering the stem in 9 (9%), and a combination of 2 or more of these modifications in 19 implants (17%). Among the 55 index surgeries available for complication analysis, 40 complications occurred in 28 index surgeries (11 primary and 17 revisions; 25 patients), making the overall complication rate 51%. Of these 40 complications, 23 were considered independent of any implant modification. Of the remaining 17 complications, 9 were considered nonrelated to the implant modification, 6 were possibly related, and 2 were probably related to the implant modification. Therefore, the complication rate possibly related or probably related to implant modification was 15% (8 of 55). No complication was classified as definitely related to the implant modification. No implant breakage or malfunction occurred after any modification. A total of 442 survey responses were received representing 29 countries, of which 144 surgeons (39%) performed modification to implants during TEA procedures. DISCUSSION: This study confirmed our hypothesis that modification of TEA implants is not uncommon at our institution, particularly in revision arthroplasty. Surgeons should keep in mind that complications possibly related or probably related to implant modification were at minimum 15% and could have been as high as 30% if the patients lost to follow-up had all had complications. Implant modification may be necessary in some cases but should be exercised with thoughtful consideration and caution.

AAPM MEDICAL PHYSICS PRACTICE GUIDELINE 2.b.: Commissioning and quality assurance of X-ray-based image-guided radiotherapy systems.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized.

Anatomic total shoulder arthroplasty for primary glenohumeral osteoarthritis is associated with excellent outcomes and low revision rates in the elderly.

BACKGROUND: The relative indications of anatomic total shoulder arthroplasty (TSA) and reverse shoulder arthroplasty (RSA) continue to evolve. Some surgeons favor RSA over TSA for elderly patients with primary glenohumeral osteoarthritis (GHOA) and an intact rotator cuff due to fear of a postoperative (secondary) rotator cuff tear in this age group. However, RSA is associated with unique complications and a worse functional arc of motion compared with TSA. Therefore, it is important to understand the clinical outcomes and rates of revision surgery and secondary rotator cuff tears in elderly patients undergoing TSA. METHODS: Between January 1, 2010, and December 31, 2017, 377 consecutive TSAs were performed for primary GHOA in 340 patients 70 years of age or older. The mean age at surgery was 76.2 years (standard deviation [SD], 4.9). Clinical evaluation included pain, motion, and American Shoulder and Elbow Surgeons score. Radiographs were reviewed for preoperative morphology and postoperative complications. All complications and reoperations were recorded. The average clinical follow-up time was 3.3 years (SD, 2.0). Statistical analyses were performed, and Kaplan-Meier implant survival estimates were calculated. For all analyses, a P value <.05 was considered statistically significant. RESULTS: The mean pain visual analog scale and American Shoulder and Elbow Surgeons score at the final follow-up were 1.6 (SD, 2.2) and 78.0 (SD, 17.8), respectively. Forward elevation and external rotation increased from 96° (SD, 30°) and 26° (SD, 20°) preoperatively to 160° (SD, 32°) and 64° (SD, 26°) postoperatively (P < .001 for each). The percentage of patients who had internal rotation to L5 or greater increased from 24.8% preoperatively to 71.8% postoperatively (P < .001). Revision surgery was performed in 3 shoulders (0.8%), and the 5-year implant survival estimate was 98.9% (95% confidence interval: 97.3%-100%). There were 3 medical (0.8%), 10 minor surgical (2.7%), and 5 major surgical (1.3%) complications. No shoulder had radiographic evidence of humeral component loosening, whereas 7 (2%) had evidence of some degree of glenoid component loosening. In total, there were 5 secondary rotator cuff tears (1.3%), of which 2 (0.5%) required revision surgery. CONCLUSION: Elderly patients with primary GHOA and an intact rotator cuff have excellent clinical and radiographic outcomes after anatomic TSA, with high implant survival rates and a low incidence of secondary rotator cuff tears in the first 5 postoperative years. Age greater than 70 by itself should not be considered an indication for RSA over TSA.

Players' perspectives on successfully returning to professional baseball after medial ulnar collateral ligament reconstruction.

BACKGROUND: As the incidence of ulnar collateral ligament reconstruction (UCLR) surgery continues to rise, an improved understanding of baseball pitchers' perspectives on the postoperative recovery process and return to pitching is needed. The purpose of this study was to analyze pitchers' perspectives on recovery after UCLR. METHODS: dDuring the 2018 baseball season, an online questionnaire was distributed to the certified athletic trainers of all 30 Major League Baseball (MLB) organizations. These athletic trainers then administered the survey to all players within their organization including MLB and 6 levels of Minor League Baseball. MLB or Minor League Baseball pitchers who had previously undergone UCLR and participated in a rehabilitation program (or were currently participating in one at time of the survey) were included in the study. RESULTS: There were 530 professional pitchers who met inclusion criteria. The majority (81%) of pitchers began rehabilitation within 2 weeks of surgery, with 51% beginning within 1 week. The majority of pitchers began a long-toss throwing program at 5 and 6 months after surgery (27% and 21%), with 52% making their first throw off a mound between 7 and 9 months. The number of pitchers who participated in a weighted ball throwing program decreased significantly after surgery (20%-11%, P < .001). After UCLR, 56% of pitchers reported no changes regarding pitching mechanics or types of pitches thrown, 42% reported changed mechanics, and only 3% either decreased or stopped throwing a certain pitch type. Overall, 54% believed that their current throwing velocity was faster than their velocity before ulnar collateral ligament injury. Twenty percent of pitchers reported experiencing a setback that resulted in temporary stoppage of their rehabilitation program, the most common reason being flexor tightness or tendonitis (53%). Seventy-six percent reported that they were not concerned about sustaining another elbow injury; however, significantly less (61%; P < .001) stated that they would have UCLR again if necessary. CONCLUSIONS: Although UCLR is generally reported to have excellent clinical outcomes, 20% of pitchers experienced a significant setback during their rehabilitation and only 61% of pitchers, having gone through UCLR and the subsequent recovery, would be willing to undergo revision surgery and repeat the rehabilitation process if it were to become necessary. In addition, 42% of pitchers felt that they had to alter their throwing mechanics to return to pitching. Surgeons and athletic trainers should aim to understand the UCLR recovery process from the pitchers' perspective to better counsel future patients recovering from UCLR.

Establishing the learning curve for elbow arthroscopy: surgeon and trainee perspectives on number of cases needed and optimal methods for acquiring skill.

BACKGROUND: Elbow arthroscopy has increased in frequency as its indications have widened. Despite this growth, a learning curve has not yet been defined. HYPOTHESIS: We hypothesized that there would be significant differences in perspective between trainees and established surgeons for the number of cases needed to reach each skill level and what they felt are the most valuable training tools. METHODS: Orthopedic attending physicians and trainees were asked to complete a questionnaire assessing participant demographics, case volumes required to reach defined skill levels (novice, safe, competent, proficient, and expert), and the efficacy of various learning methodologies for elbow arthroscopy. The value of educational methods was assessed using a 5-point Likert scale (1 = not at all valuable; 5 = extremely valuable). RESULTS: The study population consisted of 323 total participants, of whom 224 (69.3%) were attending surgeons and 99 (30.7%) were trainees (resident or fellow physicians). According to the attending physicians, the mean numbers of cases needed to reach each skill level were 19 to be safe, 42 to be competent, 93 to be proficient, and 230 to be expert. These case numbers were not significantly different from the perspectives of trainees. Across the respondents, there were no significant differences in the number of cases needed to reach each level of skill based on the respondents' level of training, years of experience, type of fellowship, or self-reported skill level.Although both groups highly valued live surgery (4.7 of 5) and cadaveric practice (4.6 of 5) for acquiring skill, attendings placed higher value on reading (4.0 vs. 3.3, P < .001), videos/live demos (4.2 vs. 3.6, P < .001), and formal courses (4.5 vs. 4.1, P < .001) than trainees. Both groups place relatively low value on surgical simulators (2.8-3.6). CONCLUSIONS: There was considerable agreement among attending surgeons and trainees in terms of the number of cases needed to attain various skill levels of elbow arthroscopy, which was consistent regardless of fellowship background, self-reported skill level, career length, and elbow arthroscopy case volume. However, there was some disagreement between attending surgeons and trainees over the most valuable methods for acquiring surgical skill with trainees placing less value on textbooks, surgical videos, and formal courses compared with attending surgeons. An understanding of the elbow arthroscopy learning curve will help trainees and their training programs establish case volume targets before safe, independent practice. Future studies should aim to clinically validate this learning curve.

Adipose-derived Human Perivascular Stem Cells May Improve Achilles Tendon Healing in Rats.

BACKGROUND: Achilles tendon rupture is a common injury and the best treatment option remains uncertain between surgical and nonoperative methods. Biologic approaches using multipotent stem cells such as perivascular stem cells pose a possible treatment option, although there is currently a paucity of evidence regarding their clinical therapeutic use. QUESTIONS/PURPOSES: The purpose of this study was to determine whether injected perivascular stem cells (PSCs) would (1) improve histologic signs of tendon healing (such as percent area of collagen); and (2) improve biomechanical properties (peak load or stiffness) in a rat model of Achilles tendon transection. METHODS: Two subtypes of PSCs were derived from human adipose tissue: pericytes (CD146CD34CD45CD31) and adventitial cells (CD146CD34CD45CD31). Thirty-two athymic rats underwent right Achilles transection and were randomized to receive injection with saline (eight tendons), hydrogel (four tendons), pericytes in hydrogel (four tendons), or adventitial cells in hydrogel (eight tendons) 3 days postoperatively with the left serving as an uninjured control. Additionally, a subset of pericytes was labeled with CM-diI to track cell viability and localization. At 3 weeks, the rats were euthanized, and investigators blinded to treatment group allocation evaluated tendon healing by peak load and stiffness using biomechanical testing and percent area of collagen using histologic analysis with picrosirius red staining. RESULTS: Histologic analysis showed a higher mean percent area collagen for pericytes (30%) and adventitial cells (28%) than hydrogel (21%) or saline (26%). However, a nonparametric statistical analysis yielded no statistical difference. Mechanical testing demonstrated that the pericyte group had a higher peak load than the saline group (41 ± 7 N versus 26 ± 9 N; mean difference 15 N; 95% confidence interval [CI], 4-27 N; p = 0.003) and a higher peak load than the hydrogel group (41 ± 7 N versus 25 ± 3 N; mean difference 16; 95% CI, 8-24 N; p = 0.001). The pericyte group demonstrated higher stiffness than the hydrogel group (36 ± 12 N/mm versus 17 ± 6 N/mm; mean difference 19 N/mm; 95% CI, 5-34 N/mm; p = 0.005). CONCLUSIONS: Our results suggest that injection of PSCs improves mechanical but not the histologic properties of early Achilles tendon healing. CLINICAL RELEVANCE: This is a preliminary study that provides more insight into the use of adipose-derived PSCs as a percutaneous therapy in the setting of Achilles tendon rupture. Further experiments to characterize the function of these cells may serve as a pathway to development of minimally invasive intervention aimed at improving nonoperative management while avoiding the complications associated with surgical treatment down the line.

The Assessment of Quality, Accuracy, and Readability of Online Educational Resources for Platelet-Rich Plasma.

PURPOSE: To critically evaluate the quality, accuracy, and readability of readily available Internet patient resources for platelet-rich plasma (PRP) as a treatment modality for musculoskeletal injuries. METHODS: Using the 3 most commonly used Internet search engines (Google, Bing, Yahoo), the search term "platelet rich plasma" was entered, and the first 50 websites from each search were reviewed. The website's affiliation was identified. Quality was evaluated using 25-point criteria based on guidelines published by the American Academy of Orthopaedic Surgeons, and accuracy was assessed with a previously described 12-point grading system by 3 reviewers independently. Readability was evaluated using the Flesch-Kincaid (FK) grade score. RESULTS: A total of 46 unique websites were identified and evaluated. The average quality and accuracy was 9.4 ± 3.4 (maximum 25) and 7.9 ± 2.3 (maximum 12), respectively. The average FK grade level was 12.6 ± 2.4, which is several grades higher than the recommended eighth-grade level for patient education material. Ninety-one percent (42/46) of websites were authored by physicians, and 9% (4/46) contained commercial bias. Mean quality was significantly greater in websites authored by health care providers (9.8 ± 3.1 vs 5.9 ± 4.7, P = .029) and in websites without commercial bias (9.9 ± 3.1 vs 4.5 ± 3.2, P = .002). Mean accuracy was significantly lower in websites authored by health care providers (7.6 ± 2.2 vs 11.0 ± 1.2, P = .004). Only 24% (11/46) reported that PRP remains an investigational treatment. CONCLUSIONS: The accuracy and quality of online patient resources for PRP are poor, and the information overestimates the reading ability of the general population. Websites authored by health care providers had higher quality but lower accuracy. Additionally, the majority of websites do not identify PRP as an experimental treatment, which may fail to provide appropriate patient understanding and expectations. CLINICAL RELEVANCE: Physicians should educate patients that many online patient resources have poor quality and accuracy and can be difficult to read.

Neer Award 2018: Platelet-derived growth factor receptor α co-expression typifies a subset of platelet-derived growth factor receptor ß-positive progenitor cells that contribute to fatty degeneration and fibrosis of the murine rotator cuff.

BACKGROUND AND HYPOTHESIS: After massive tears, rotator cuff muscle often undergoes atrophy, fibrosis, and fatty degeneration. These changes can lead to high surgical failure rates and poor patient outcomes. The identity of the progenitor cells involved in these processes has not been fully elucidated. Platelet-derived growth factor receptor ß (PDGFRß) and platelet-derived growth factor receptor α (PDGFRα) have previously been recognized as markers of cells involved in muscle fibroadipogenesis. We hypothesized that PDGFRα expression identifies a fibroadipogenic subset of PDGFRß+ progenitor cells that contribute to fibroadipogenesis of the rotator cuff. METHODS: We created massive rotator cuff tears in a transgenic strain of mice that allows PDGFRß+ cells to be tracked via green fluorescent protein (GFP) fluorescence. We then harvested rotator cuff muscle tissues at multiple time points postoperatively and analyzed them for the presence and localization of GFP+ PDGFRß+ PDGFRα+ cells. We cultured, induced, and treated these cells with the molecular inhibitor CWHM-12 to assess fibrosis inhibition. RESULTS: GFP+ PDGFRß+ PDGFRα+ cells were present in rotator cuff muscle tissue and, after massive tears, localized to fibrotic and adipogenic tissues. The frequency of PDGFRß+ PDGFRα+ cells increased at 5 days after massive cuff tears and decreased to basal levels within 2 weeks. PDGFRß+ PDGFRα+ cells were highly adipogenic and significantly more fibrogenic than PDGFRß+ PDGFRα- cells in vitro and localized to adipogenic and fibrotic tissues in vivo. Treatment with CWHM-12 significantly decreased fibrogenesis from PDGFRß+ PDGFRα+ cells. CONCLUSION: PDGFRß+ PDGFRα+ cells directly contribute to fibrosis and fatty degeneration after massive rotator cuff tears in the mouse model. In addition, CWHM-12 treatment inhibits fibrogenesis from PDGFRß+ PDGFRα+ cells in vitro. Clinically, perioperative PDGFRß+ PDGFRα+ cell inhibition may limit rotator cuff tissue degeneration and, ultimately, improve surgical outcomes for massive rotator cuff tears.

Influence of patient's physiologic factors and immobilization choice with stereotactic body radiotherapy for upper lung tumors.

The purpose of the present study was to compare the impact of pulmonary function, body habitus, and stereotactic body radiation therapy (SBRT) immobilization on setup and reproducibility for upper lung tumor. From 2008 through 2011, our institution's prospective SBRT database was searched for patients with upper lung tumors. Two SBRT immobilization strategies were used: full-length BodyFIX and thermoplastic S-frame. At simulation, free-breathing, four-dimensional computed tomography was performed. For each treatment, patients were set up to isocenter with in-room lasers and skin tattoos. Shifts from initial and subsequent couch positions with cone-beam computed tomography (CBCT) were analyzed. Accounting for setup uncertainties, institutional tolerance of CBCT-based shifts for treatment was 2, 2, and 4 mm in left-right, anterior-posterior, and cranial-caudal directions, respectively; shifts exceeding these limits required reimaging. Each patient's pretreatment pulmonary function test was recorded. A multistep, multivariate linear regression model was performed to elucidate intervariable dependency for three-dimensional calculated couch shift parameters. BodyFIX was applied to 76 tumors and S-frame to 17 tumors. Of these tumors, 41 were non-small cell lung cancer and 15 were metastatic from other sites. Lesions measured < 1 (15%), 1.1 to 2 (50%), 2.1 to 3 (25%), and > 3 (11%) cm. Errors from first shifts of first fractions were significantly less with S-frame than BodyFIX (p < 0.001). No difference in local control (LC) was found between S-frame and BodyFIX (p = 0.35); two-year LC rate was 94%. Multivariate modeling confirmed that the ratio of forced expiratory volume in the first second of expiration to forced vital capacity, body habitus, and the immobilization device significantly impacted couch shift errors. For upper lung tumors, initial setup was more consistent with S-frame than BodyFIX, resulting in fewer CBCT scans. Patients with obese habitus and poor lung function had more SBRT setup uncertainty; however, outcome and probability for LC remained excellent.

Arthroscopic debridement for acute hemorrhagic subacromial bursitis following COVID-19 vaccine administration: A case report.

The rapid rollout of vaccinations in response to the COVID-19 pandemic has led to their widespread distribution and administration throughout the world. The benefit of these vaccinations in preventing the spread of the disease and diminishing symptoms in patients who contract COVID-19 has been fervently studied and reported. While vaccinations remain an effective and generally safe method of limiting disease transmission and virus-related mortality, vaccine administration is not completely without risk. Shoulder injuries related to vaccine administration (SIRVA) have been described with previously available vaccines but have yet to be widely reported in the COVID-19 vaccination population. We present a case report of a young, high-functioning patient who presented with acute subacromial bursitis after COVID-19 vaccine administration due to improper vaccination technique. The patient was treated with arthroscopic shoulder surgery and had near immediate relief of shoulder symptoms.

On the length used for CT ionization chambers to determine CTDI.

Objective.Computed tomography dose index (CTDI) calculations based on measurements made with CT ionization chambers require characterization of two chamber properties: radiation sensitivity and effective length. The sensitivity of a CT ionization chamber is currently determined in some countries by calibration in an x-ray field that irradiates the entire chamber. Determination of the effective length is left to the user, and this value is frequently assumed to be equivalent to the nominal length-typically 100 mm-stated by the manufacturer. This assumption undermines the intention and usefulness of CTDI calculation. Thus, a slit-based calibration,NKL, of the CT ionization chambers was proposed by collimating the x-ray beam to a well-defined aperture width. The aim of this work is to compare the two methods.Approach.Four different CT ionization chambers (Standard Imaging Exradin A101, Radcal 10x5-3CT, Victoreen 500-100, and Capintec PC-4P) are investigated in this work. Sensitivity profiles were measured for all four chambers and effective/rated chamber lengths were calculated. A novel Monte-Carlo based correction was proposed to account for the presence of the aperture. CTDI was calculated and compared for two calibration beams as well as for a commercial CT scanner using Exradin A101 and Radcal 10x5-3CT chambers.Main results.The nominal chamber length was found to deviate up to 21% compared to the effective length. Correction for the aperture depended on the aperture opening size. CTDI calculation results illustrate the potential 17% error in CTDI calculation that can be caused by assuming the effective chamber length is equivalent to the manufacturer's stated nominal length. CTDI calculations with CT ionization chambers calibrated with an air-kerma length calibration method yield the smallest variation in the CTDI regardless of the chamber model.Significance.To avoid an erroneous CTDI, information regarding the chamber's effective length must be included in the calibration or stated by the manufacturer. Alternatively, a slit-based calibration can be performed.

Five Years In: The AAOS Resident Assembly, "Bidirectional Communication," and Early Career Involvement in Orthopaedic Leadership.

Established in 2014, the American Academy of Orthopaedic Surgeons (AAOS) Resident Assembly (RA) has served as a mode of "bidirectional communication" between AAOS and a combined resident body. Training and education initiatives relevant to the current issues facing residency training can be passed up to and directly addressed by the leadership of AAOS, whereas AAOS recruitment and membership initiatives can be disseminated to the full resident body through the RA. Since its inception in 2014, the RA has grown markedly, with representation from most MD and DO residency programs in the United States and Canada. It also has included an increasing number of medical students from Orthopaedic Surgery Interest Groups to directly take part in RA activities. For the past half decade, the RA has served as a partner for the AAOS in addition to a valuable recruitment tool to engage the broadest diversity of potential orthopaedic leaders at their earliest stages of training. This work is a review of the development of the RA over its first half decade, as well as a discussion of its future goals in line with AAOS priorities.

Development of a Machine Learning Algorithm for Prediction of Complications and Unplanned Readmission Following Primary Anatomic Total Shoulder Replacements.

Background: The demand and incidence of anatomic total shoulder arthroplasty (aTSA) procedures is projected to increase substantially over the next decade. There is a paucity of accurate risk prediction models which would be of great utility in minimizing morbidity and costs associated with major post-operative complications. Machine learning is a powerful predictive modeling tool and has become increasingly popular, especially in orthopedics. We aimed to build a ML model for prediction of major complications and readmission following primary aTSA. Methods: A large California administrative database was retrospectively reviewed for all adults undergoing primary aTSA between 2015 to 2017. The primary outcome was any major complication or readmission following aTSA. A wide scope of standard ML benchmarks, including Logistic regression (LR), XGBoost, Gradient boosting, AdaBoost and Random Forest were employed to determine their power to predict outcomes. Additionally, important patient features to the prediction models were indentified. Results: There were a total of 10,302 aTSAs with 598 (5.8%) having at least one major post-operative complication or readmission. XGBoost had the highest discriminative power (area under receiver operating curve AUROC of 0.689) of the 5 ML benchmarks with an area under precision recall curve AURPC of 0.207. History of implant complication, severe chronic kidney disease, teaching hospital status, coronary artery disease and male sex were the most important features for the performance of XGBoost. In addition, XGBoost identified teaching hospital status and male sex as markedly more important predictors of outcomes compared to LR models. Conclusion: We report a well calibrated XGBoost ML algorithm for predicting major complications and 30-day readmission following aTSA. History of prior implant complication was the most important patient feature for XGBoost performance, a novel patient feature that surgeons should consider when counseling patients.

Updates on mesenchymal stem cell therapies for articular cartilage regeneration in large animal models.

There is an unmet need for novel and efficacious therapeutics for regenerating injured articular cartilage in progressive osteoarthritis (OA) and/or trauma. Mesenchymal stem cells (MSCs) are particularly promising for their chondrogenic differentiation, local healing environment modulation, and tissue- and organism-specific activity; however, despite early in vivo success, MSCs require further investigation in highly-translatable models prior to disseminated clinical usage. Large animal models, such as canine, porcine, ruminant, and equine models, are particularly valuable for studying allogenic and xenogenic human MSCs in a human-like osteochondral microenvironment, and thus play a critical role in identifying promising approaches for subsequent clinical investigation. In this mini-review, we focus on [1] considerations for MSC-harnessing studies in each large animal model, [2] source tissues and organisms of MSCs for large animal studies, and [3] tissue engineering strategies for optimizing MSC-based cartilage regeneration in large animal models, with a focus on research published within the last 5 years. We also highlight the dearth of standard assessments and protocols regarding several crucial aspects of MSC-harnessing cartilage regeneration in large animal models, and call for further research to maximize the translatability of future MSC findings.

Return to Sports After Primary Reverse Shoulder Arthroplasty: Outcomes at Mean 4-Year Follow-up.

BACKGROUND: With the expanding use of reverse shoulder arthroplasty (RSA) to treat various shoulder conditions, there has been a rise in the number of RSAs performed, especially in physically active patients. Limited information regarding sports after RSA is available to properly counsel patients on postoperative expectations. PURPOSE: To assess the rate of return to sports as well as the ability to return to the same level of preoperative intensity, frequency, and duration of sport after primary RSA. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: This was a retrospective review of patients who underwent primary RSA at our institution between 2014 and 2016. Shoulder motion, Subjective Shoulder Value score, American Shoulder and Elbow Surgeons score, pre- and postoperative sports activities, and barriers to return to sport were assessed in 109 patients after RSA (93 patients with unilateral RSA and 16 patients with bilateral RSA). The mean age at the time of surgery was 70 years (range, 34-86 years), with a mean follow-up of 3.9 years (range, 2-12 years). RESULTS: The mean rate of return to sports was 70.1% (range, 0%-100%). There was no difference in return to sports between those with uni- and bilateral RSA (P = .64). Fishing, swimming, elliptical/treadmill, and hunting were the most common sports after RSA with return rates of 91%, 73%, 86%, and 82% respectively. A majority of patients returned to the same level of preoperative intensity, frequency, and duration for all sports except for climbing and swimming. There was a lower mean rate of return for high-demand sports (62.9%) compared with low- and medium-demand sports (76.7%) (P = .005). The most common reasons for inability to return to sports included limited motion, fear of injury, and weakness. CONCLUSION: Patients who had undergone primary uni- or bilateral RSA reported a 70.1% rate of return to sports with maintenance of the same level of intensity, duration, and frequency of preoperative sport participation. Rates of return to high-demand sports were lower than low- and medium-demand sports. Patients also had difficulty returning to overhead sports.

Lateral to medial fibro-adipogenic degeneration are greater in infraspinatus than supraspinatus following nerve and tendon injury of murine rotator cuff.

Small animal models of massive tears of the rotator cuff (RC) were introduced a decade ago and have been extensively used to study the pathophysiology of chronically injured RC. Transection of rodent suprascapular nerve and RC tendon results in progressive muscle atrophy, fibrosis and fat accumulation and affect the infraspinatus and supraspinatus muscles similarly to that seen in the setting of massive RC tears in humans. The purpose of this study was to perform a comprehensive and detailed analysis of the kinetics of fibrotic scar and adipose tissue development comparing phenotypic differences between chronically injured infraspinatus and supraspinatus. Automatic mosaic imaging was used to create large image of whole infraspinatus or supraspinatus sectioned area for quantification of spatial heterogeneity of muscle damage. Pathologic changes advanced from the lateral site of transection to the medial region far from the transection site. A prominent, accelerated muscle fibrosis and fat accumulation was measured in injured infraspinatus compared to supraspinatus. Furthermore, adipose tissue occupied significantly larger area than that of fibrotic tissue in both muscles but was greater in infraspinatus within 6 weeks post induction of injury. Our findings confirm that infraspinatus is more susceptible to accelerated chronic degeneration and can be used to identify the physiological functions that distinguish between the response of infraspinatus and supraspinatus in the setting of massive tears. Whether these pathologic differences observed in mice are reflected in humans is one key aspect that awaits clarification.

Development of a Machine Learning Algorithm for Prediction of Complications and Unplanned Readmission Following Reverse Total Shoulder Arthroplasty.

Background: Reverse total shoulder arthroplasty (rTSA) offers tremendous promise for the treatment of complex pathologies beyond the scope of anatomic total shoulder arthroplasty but is associated with a higher rate of major postoperative complications. We aimed to design and validate a machine learning (ML) model to predict major postoperative complications or readmission following rTSA. Methods: We retrospectively reviewed California's Office of Statewide Health Planning and Development database for patients who underwent rTSA between 2015 and 2017. We implemented logistic regression (LR), extreme gradient boosting (XGBoost), gradient boosting machines, adaptive boosting, and random forest classifiers in Python and trained these models using 64 binary, continuous, and discrete variables to predict the occurrence of at least one major postoperative complication or readmission following primary rTSA. Models were validated using the standard metrics of area under the receiver operating characteristic (AUROC) curve, area under the precision-recall curve (AUPRC), and Brier scores. The key factors for the top-performing model were determined. Results: Of 2799 rTSAs performed during the study period, 152 patients (5%) had at least 1 major postoperative complication or 30-day readmission. XGBoost had the highest AUROC and AUPRC of 0.681 and 0.129, respectively. The key predictive features in this model were patients with a history of implant complications, protein-calorie malnutrition, and a higher number of comorbidities. Conclusion: Our study reports an ML model for the prediction of major complications or 30-day readmission following rTSA. XGBoost outperformed traditional LR models and also identified key predictive features of complications and readmission.

Factors Influencing the Reparability and Healing Rates of Rotator Cuff Tears.

PURPOSE OF THE REVIEW: To discuss tear- and patient-related factors that influence the healing potential of rotator cuff tears and to clarify the terminology surrounding this topic. RECENT FINDINGS: Over the last few years, further insight has been gained regarding rotator cuff tear features that are associated with poor healing rates after rotator cuff repair. Some of these features have been incorporated in prediction models developed to accurately predict rotator cuff healing rates utilizing preoperative risk factors weighted by importance. Rotator cuff tears may be considered functionally irreparable based on their size, chronicity, absence of adequate tendon length, atrophy, and fatty infiltration. Furthermore, advanced age, use of tobacco products, diabetes, and other patient-related factors may impair tendon healing. Careful analysis and discussion of all these factors with patients is essential to determine if surgical repair of a rotator cuff tear should be recommended, or if it is best to proceed with one of the several salvage procedures reviewed in this topical collection, including augmentation of the repair, superior capsular reconstruction, tendon transfers, and other.

Dose Gradient Index for Stereotactic Radiosurgery/Radiation Therapy.

PURPOSE: Steep dose falloff outside of tumors is a hallmark of stereotactic radiosurgery (SRS) and radiation therapy (SRT). Dose gradient index (DGI) quantifies the dose drop off. Tables of DGIs versus target volumes have been published for body sites, but none is available for brain. This study recommends guidelines for DGIs for brain SRS/SRT treatments based on clinical CyberKnife (CK) cases. METHODS AND MATERIALS: Four hundred ninety-five plans for patients with central nervous system tumors treated with CK at our institution between March 2015 and May 2018 were analyzed. The CK treatment planning system MultiPlan was used for planning. SRS/SRT plans were stratified into 6 groups by tumor size (Group I [0-1 cm3], II [1.0-3.0 cm3], III [3.0-5.0 cm3], IV [5.0-10.0 cm3], V [10.0-15.0 cm3], and VI [15.0-40.0 cm3]). Ideal and minimally acceptable DGIs were determined for each size group. To evaluate the effect of target shape on DGI criteria, the plans were divided into 4 target shape groups: (1) homogeneous shape (circular), (2) adjacent to radiosensitive organs at risk (adjacent), (3) irregularly shaped (irregular), and (4) multiple target plans (multilesion). The mean for each target size group was defined as the ideal DGI. Minimally acceptable DGI criteria are specified to reject the lowest 10% of cases. RESULTS: The minimal acceptable DGIs were 83 (Group I), 72 (II), 65 (III), 58 (IV), 52 (V), and 35 (VI). The ideal DGI is designated to evaluate SRS/SRT plans for homogeneous circular lesions, whereas minimal DGI is chosen to assess the plans for irregular, adjacent to organs at risk, and multilesions. SRS/SRT plans with higher DGI values are correlated with lower irradiated normal tissue volumes. CONCLUSIONS: This study provides a table of DGIs for brain SRS/SRT treatments as a tool for assessing the quality of intracranial SRS/SRT plans. DGI guidelines support SRS/SRT planning that results in lower risk of radionecrosis.